Acoustical Modeling of Reciprocating Compressors with Stepless Valve Unloaders
Kelly Eberle, P.Eng & Brian C. Howes, M.Sc., P.Eng.–Beta Machinery Analysis, Ltd.
Capacity control of reciprocating compressors can be accomplished by a variety of techniques. Some common techniques include changing compressor speed, adjusting compressor cylinder head-end variable volume pockets, recycling slow and changing compressor cylinder operation from double acting to single acting. These compressor loading techniques are well understood from an acoustical simulation perspective. One shortcoming with these compressor control techniques is they do not offer a continuous range of capacity control with minimal wasted energy. Stepless valve unloaders are one solution to address this short-coming. Acoustical simulation of reciprocating compressors using stepless valve unloaders offers several challenges. This paper presents techniques for modeling systems with stepless valve unloaders. Results of an acoustic simulation are compared for systems with and without stepless valve unloaders.
Subjects: Acoustics, Modeling, Stepless Valve Unloaders
Addressing Hazardous Air Pollutant & Odor Issues for Natural Gas Fired Lean Burn Engines
Gregg Arney & Larry Sasadeusz–Southern California Gas Co./Larry Hottenstein-MWH America
The National Emission Standards for Hazardous Pollutants (NESHAP) regulations require Maximum Achievable Control Technology (MACT) when the annual mass emissions of Hazardous Air Pollutants (HAP) exceed the maximum source threshold. However, in California, HAPs are also controlled under Toxic Hot Spot Regulations which are based on health risk determinations rather than mass emissions. This creates a completely different set of problems than MACT, including which HAPs species are of concern, air dispersion, risk calculations, and refinement of catalytic control technologies. Many of these same issues must be addressed when dealing with odor complaints. SoCalGas has experiences which demonstrate the process, its pitfalls and solutions. SoCalGas also learned before spending capital on catalysts, it is best to verify catalyst performance using a corollary reactor and exhaust slip stream. Risk based analysis will become important to the entire industry as individual states drive new regulations from health laws (as opposed to air regulations) and when EPA addresses MACT residual health risk around 2012.
Advanced Reciprocating Compression Technology (ARCT)
Danny M. Deffenbaugh, Ralph Harris, Robert McKee & Klaus Brun–Southwest Research Institute
The objective of this research and development project is to develop the next generation of Advanced Reciprocating Compression Technology (ARCT) to enhance the efficiency, reliability, and integrity of pipeline operations through improved compression. The suite of technologies developed during this program will provide pipeline operators with improved choices for new and retrofit applications. The current state of the art is passive and fixed configurations for a specific operating design point. However, compressors infrequently operate at that design point, resulting in an overall reduction in reliability and efficiency. The advanced concepts for ARCT are intelligent compression technologies that monitor operational conditions and automatically adapt internal geometries to tune performance over the full-required operational range. The result is improved performance and enhanced machine integrity for optimized gas throughput. The ARCT program duration is five years with three sequential phases. Each phase will increase the next generation of compression technology. Each phase of the program is organized into five tasks. Each task will address a different compressor subsystem: advanced pulsation control, advanced capacity control, advanced valve technology, advanced sensors and automation, and systems integration and optimization.
Subjects: Efficiency, Infrastructure, Reliability
Fiji George-El Paso Corp./Jim McCarthy–Innovative Equipment Solutions
This annual session on air regulatory issues will include updates on air permitting, Title V, NSR, MACT implementation, NOx SIP Implementation, turbine NSPS, and greenhouse gases.
Subjects: Emissions
Alternative Methods of Engine Balance Based on In-Cylinder Determination of Air/Fuel Ratio
Greg Beshouri & Mark Richter–Advanced Engine Technologies Corporation
Engines in the natural gas pipeline industry operate under even more stringent emissions restrictions. Some of these engines, particularly in the Northeast, have been subject to regulations requiring NOx emissions reductions down to ~3 g/BHP-HR or less. Balance is a key to achieving and maintaining these low emissions. However, recent research has shown the traditional methods of balance, based on peak combustion pressure, may not result in optimal NOx emissions. Rather, optimum balance for emissions occurs when each cylinder operates at the same air/fuel ration. Variations in cylinder charging and scavenging can result in differences in the air trapped in each cylinder. Consequently, even when fuel is precisely metered by modern electronic fuel injection systems, the air/fuel ratio will not necessarily be the same. Peak pressure balance then results in some cylinders operating leaner than optimal while others operate richer than optimal. Recognizing these limitations, AETC has been investigating air/fuel ratio based balance methods for over 5 years, funded in part by the Pipeline Research Council International (PRCI). This effort has resulted in two methods of determining and balancing air/fuel ratio in typical lean burn pipeline engines. The first method, pressure ratio, is based on work in the automotive industry from the 1990s. The technique exploits low cost/low performance methods of measuring in-cylinder pressure by calculating the pressure ratio and then using this as a surrogate for Mass Fraction Burned (MFB). The MFB directly correlates with air/fuel ratio, as does pressure ratio when properly calculated. The second method, again based on automotive technology, utilizes post ignition ionization measurements from a standard spark plug. This data rich signal contains information on air/fuel ratio in addition to misfire, detonation, peak pressure, location of peak pressure and IMEP. AETC has used both methods to determine air/fuel balance ratio from typical pipeline engines both in the lab and field. This paper presents these results for the first time in the open literature.
Subjects: Air/Fuel Ratio, Balance
Analysis of Exhaust Silencer Stack Using CFD
Jeet Sengupta, Ali Keshavarz & Kirby Chapman-Kansas State University NGML/Jon Tice-El Paso Corp.
A key concern during stack emissions testing is the sampling port location. The sampling port must be selected so that the velocity measurements truly represent the exhaust gas flow field within the exhaust stack. Usually the port is located near the stack exit. However, in some instances during field testing, concerns have been raised over the location of the port and its influence in accurate measurements. Furthermore, the use of perforated baffles in the silencer stack has also been questioned; it has been suggested that these could cause flow disturbances that are not acceptable. The veracity of the concerns raised can be examined by physically changing the baffle design and the location of the port. However, this approach would not only take an extensive period of time but would also prove expensive. A lower cost approach is to conduct a CFD analysis on the existing silencer stack and then analyze the results to determine the impact of small perturbations on the measurements and the overall flow field. Modifications, if needed, could be made in the solid model of the silencer/stack system. The impact of these modifications could then be tested with the CFD model to determine how the unmodified stack compares to the modified stack and to establish the degree to which the baffle perforations and the port location influence testing results. The paper describes a detailed CFD analysis of the flow pattern in the silencer stack.
Subjects: Computational Fluid Dynamics, Exhaust
API Specifications Review for Gas Turbine Driven Turbocompressors
Klaus Brun, Ph.D., Jeff Moore & Anthony J. Smalley, Ph.D.–Southwest Research Institute/Rainer X. Kurz, Ph.D.–Solar Turbines Incorporated
This tutorial will provide an overview of the latest editions of American Petroleum Institute (API) Codes API 613, 614, 616, 617, 670, 671, and 677 as they apply to gas turbine driven compressors. Critical sections of the codes will be discussed in detail with a special focus on their technical interpretation and relevance for the purchasing scope-of-supply comparison, machine testing, and field operation. Technical compliance issues for package, core engine, instrumentation, and driven compressor will be addressed individually. As the API 616 and 617 data sheets form the backbone for most oil and gas machinery acquisitions, they will be covered in detail. Some recommendations for acceptance of manufacturer exceptions to API and the technical/commercial implications will be provided. A brief discussion of the relevance of NFPA 70 to gas turbine driven compressor sets in oil and gas applications will be included. The perspective on API specifications and codes from a gas turbine and compressor manufacturer will also be presented. This tutorial course is intended for purchasing, operating, and engineering staff of turbomachinery use companies.
Subjects: API Specifications, Turbines, Turbocompressors
Application of Elastomeric Materials to Valves in Reciprocating Gas Compressors
Kevin Durham–Cook Manley
Recent research into the application of elastomeric materials into reciprocating compressor valves has shown that substantial and measureable improvements in compressor valve longevity and valve element sealing efficiency over current short fiber reinforced thermoplastics is possible. Advances in polymer technology have provided elastomeric materials that possess thermomechanical and chemical resistance properties suitable for compressor valve applications. Elastomers alone possess the inherent ability to form gas tight seals over a wide range of irregular surfaces however elastomeric materials typically lack the mechanical properties to resist the severe loads imparted by high differential pressures. A method has been developed whereby a thermoset or thermoplastic substrate is used in conjuction with an elastomeric overlay to operate at pressures up to 600 psid. In this manner, the improved sealing capabilities of elastomeric materials can be realized in reciprocating compressor valves with differential pressures that allow for application to most compressed gas services. This technology not only improves the operational efficiency of compressor valves but the substantial improvements in the mean time between failures suggests that unscheduled compressor shutdowns and the costs associated with them can be minimized or avoided in the interval between compressor overhauls. Non-linear FEA is used to evaluate the contact behavior between the elastomeric element and rigid seating surface. Understanding and optimizing the contact regions allows for efficient geometries to be used that keep operational stresses below thresholds where damage to the elastomeric materials can occur. Due to the dynamics of compressor valve elements, rigid/glassy materials are typically excluded from use however the energy dissipation properties of elastomers will provide opportunities for thermoset or thermoplastic materials with favorable chemical resistance, but lacking the necessary impact or fracture properties, to be used. Elastomeric technology increases the damage tolerance of compressor valves, makes more materials available for use in reciprocating compressor valves and the ability to mold elastomers into complex shapes, opens the door for innovative and relatively inexpensive aerodynamic shapes to be produced for improved flow dynamics through the valve.
Subjects: Valves
Balancing Large Bore Gas Engines & Factors Affecting Balance
David W. Decker, II–Dresser-Rand Co.
The purpose of this paper is to provide reasons why it is important to balance an engine as well as describing many of the possible impediments to achieving a good balance. One of the principle reasons for balancing the firing pressures of large bore integral gas engines is that a well-balanced engine operates more smoothly and efficiently, with a reduction in harmful exhaust emissions and the frequency of detonation.
Subjects: Balance
Basic Engine & Compressor Analysis Techniques
Ben Boutin, P.Eng.-Dynalco
Reciprocating compressors and engines have many predictable failure modes which can be detected and corrected before they significantly affect the machine’s performance or availability. This short course introduces data collection and analysis techniques that can be used to detect: compressor rod failures, valve leaks, ring leaks, and valve dynamics problems: compressor horsepower and capacity inefficiencies from valve leaks, ring leaks, and pulsation; engine mechanical failures like liner scoring, valve train condition, wrist pin knocks and piston slap, and engine combustion inefficiencies from ignition timing and firing problems, power cylinder unbalance, and port and valve dynamics. The course focuses on the scientific and physical principles at play rather than on a specific tool. Using the problem-solving techniques outlined in this course, participants will be able to determine what measurements to take, where and how to take them and how to convert the data into intelligence about their machine’s condition and performance. This course introduces methods for performing engine and compressor economic analysis and how economic results are reported.
Subjects: Analysis
Basic Thermodynamics of Reciprocating Compression
Greg Phillippi-Ariel Corporation
This short course is intended to provide the attendee a review of the basic thermodynamic principles of compression utilizing a reciprocating compressor. This will include discussions of the pressure-volume diagram, volumetric efficiency, capacity, and adiabatic valve loss and friction horsepower. In addition, the topics of varying conditions, gas analysis, temperature, pulsation, staging and end deactivation horsepower are reviewed.
Subjects: Reciprocating Compressors, Thermodynamics
Closed-Loop Control of NOX Emissions in a Two-Stroke Integral Compressor Engine – Part II
Gary D. Bourn, Jack A. Smith, Jess W. Gingrich–Southwest Research Institute/Warren Lawler–Cooper Compression
This paper presents continued results from an investigation into methods to enhance operation of integral engine compressors in gas transmission service through application of advanced controls and sensors. The project is funded by the Department of Energy’s (DOE) Office of Fossil Energy and managed by the National Energy Technology Laboratory (NETL) as part of their Natural Gas Infrastructure Reliability Program, with co-funding Cooper Compression. A laboratory GMVH-6 turbocharged engine was utilized to provide baseline data in both open-chamber and pre-combustion chamber configurations. Various ‘open-loop’ control strategies were evaluated with this dataset to determine the robustness of each. Algorithms for ‘closed-loop’ feedback and adaptive control were developed to enhance the open-loop strategies for more precise control to improve efficiency and integrity at a given emissions level. As part of this process, several sensors were evaluated for their potential use in commercial systems. Of particular focus was a combined fast-response NOX and universal exhaust gas oxygen (UEGO) sensor.
Compressor Efficiency Is Worth How Much?
Charles Ely-ACTT/Bill Couch, Mark Noall & Scott Stampka-El Paso Corp./Craig Linn, Jim Harrison, Bruce Howerton, Steve Burdette, Greg Moosa & Tony Harrington-Williams Gas Pipeline
As gas transmission companies continue to look for ways to squeeze more profitability out of their existing compression equipment, concentrated efforts have been made to evaluate the economic value of new technologies on compressor efficiency. In fact, over the past few years, numerous compressor efficiency studies have been completed and some have been published. This technical paper will present a summary of findings based on published studies and non-published internal studies conducted at various pipeline operators. The report will focus primarily on compressor valve technology improvements but will also discuss other compressor modifications that have resulted in improved compressor efficiency.
Subjects: Efficiency
Compressor Operations Management Expert Tool with Sarbanes Oxley Compliance
J. Eric Maier, PE–El Paso Corp.
In today’s competitive energy marketplace, companies need the tools to give them information for capital decisions, accurate regulatory reporting, comprehensive asset analysis, and data for efficient operations. The Compressor Operations, data Management and Expert reporting Tool, COMET, gives El Paso Pipeline the resources to achieve these goals and the ability to supply this data to everyone in the company for their use. Whether it is Environmental running EPA reports, Planning modeling the pipeline, Operations running reliability studies or upper management allocating O&M dollars, COMET is the central repository for the information they need to make their decisions and meet regulatory requirements. Some of the applications for COMET in regard to gas compression machinery issues are: all engine data like the unit size, (Hp), capacity, (Mmscf) load, (unloaders, cylinders, rods), heat rates and hours operated on every compression and non-compression unit is included in the database; this data is used to model the pipeline for capacity sales; this data is used to determine what impact any engine change like adding unloaders bore a cylinder or adding a turbocharger will have on the performance by using a “What if” scenario. The latest program additions include the tracking of emissions with an environmental database of emissions factors. Data is automatically uploaded to all of the Environmental Emission reports. The program resides on a server that is accessible to all registered users. Users are assigned a security level depending on their job description. For example, a station operator cannot change any emission factors, and an Environmental specialist cannot change any engine performance data, yet they both can see operating data and unit running status. The operating and performance data ares used to run reliability studies and to create and manage work orders directly from the program. Innovative reports track missing fuel and data integrity. Blowdowns and lost and unaccounted gas is tracked and included in measurement reports. COMET is an enterprise wide program receiving data from the three gas control centers and one DR, data recovery site. It is used as a compliance tool for all government reports, FERC Form 2, EPA Title V, and Emission Inventory. To meet the needs of the company, the program is written and supported in house.
Subjects: Data Interpretation, Operations
Compressor Station Ancillary Equipment: Know What You Are Buying - Part 2
Fred J. Mueller-Mueller Environmental Designs, Inc./Michael A. Smith-Hoerbiger Service, Inc.
Compressor station design engineers and other design professionals are usually “systems” designers. These professionals design, specify and procure equipment that is engineered and fabricated by others. Part 2 will continue to address the basics of some of the ancillary equipment required to create an efficient, low maintenance natural gas compressor station. The information in this short course will allow the designer to make more informed decisions. The equipment covered in Part 2 will be Intake and Exhaust Systems for Turbines and Reciprocating Engines. The basic areas covered for this equipment will follow the same guidelines set forth in Part 1 and are as follows: What (is in the air, are silencing requirements, are thermal parameters); types and/or designs available and their applications; fabrication parameters; specifying your equipment, and analyzing your options. Successful completion of the course will allow design personnel to create more detailed specification sheets and to better analyze the proposals received from suppliers.
Subjects: Equipment, Exhaust Systems, Intake Systems
Computerized Method to Optimally Match Retrofit Turbochargers to Upgraded Engines
Kirby Chapman, Ali Keshavarz & Jeet Sengupta–Kansas State University NGML
The Turbocharger Reciprocating Engine Computer Simulation program (T-RECS) developed at the NGML has been used to match turbochargers to engines for the last few years. The existing T-RECS uses a user-defined compressor and turbine efficiency to conduct the matching process. However, it was perceived that a second generation T-RECS program should include the complete turbocharger map rather than a user-defined efficiency. The objective of this project was to enhance the existing T-RECS algorithm to incorporate information that would fully characterize turbocharger information. The database that provides information to the T-RECS software program has been updated with additional turbocharger characterization parameters for a number of Cooper ET-18 turbochargers. The simulation system includes sub-models of all major components between the inlet filter and the exhaust pipe of the engine. The end result is (1) the enhanced T-RECS software program that was developed at the National Gas Machinery Laboratory at Kansas State University and (2) an updated engine/turbocharger database. The simulation program calls upon the database of system components to allow the user to specify a specific system. While the database in the original edition of T-RECS contained nominal components, the current database includes additional information to determine how a turbocharger will operate and perform on a particular engine. The ET-18 turbocharger was comprehensively tested at the NGML. All the test data collected were then corrected for standard conditions and introduced into the T-RECS database. This paper describes the model development using the tested data to create the ET-18 database. The same method that was used to incorporate the ET-18 turbocharger into the database can be used to likewise incorporate other turbochargers into the database, such as the Globe 1215 Alco series turbochargers, and the HP-090G turbocharger.
Subjects: Turbochargers
Considering the Options: Making the Most of Emissions Reduction Requirements
Hans Mathews–Hoerbiger Service, Inc./Thomas W. Burgett–El Paso Corp.
This paper focuses on strategies for reducing the overall cost of emissions compliance. It explores the possibilities for more aggressive and less aggressive retrofit strategies, each offering compliance. The paper also looks at the combination of retirement and uprates within a facility for meeting mandated emissions standards. The following three scenarios are evaluated, based on maintaining the FERC permitted plant horsepower, while minimizing the cost of compliance for a 10 unit station: (1) A station wide retrofit for a moderate reduction; (2) A combination of more and less aggressive control techniques for compliance; (3) A combination of aggressive control techniques and retirement. The paper concludes with a brief case study of an actual implementation that used a combination of retirement and uprating to meet its compliance targets.
Subjects: Emissions
Controlling Engine Air Balance through Manifold Design
Gary D. Bourn, Ford A. Phillips, Ralph E. Harris–Southwest Research Institute/Randy Raymer–El Paso Corp.
This paper presents results from an investigation into the causes and correction of inlet air imbalance to power cylinders of a two-stroke integral compressor engine. The project is funded by the Department of Energy’s (DOE) Office of Fossil Energy and managed by the National Energy Technology Laboratory (NETL) as part of their Natural Gas Infrastructure Reliability Program. Co-funding for this project is provided by GMRC, El Paso, Cooper Compression, and Optimum Power Technology. A laboratory GMVH-6 turbocharged engine was utilized to provide baseline data. In addition to many performance and dynamic measurements, the engine was disassembled to quantify the geometric variations among cylinders. Three of the six power cylinders were also flow tested to investigate the variance in port discharge coefficient. From the dimensional and performance measurements, a computational model of the engine was created. The computational model was utilized to further distinguish the effects of dimensional variation and to aid in the design of manifolds or manifold modifications to achieve air balance. Prototype components are to be manufactured and validation testing on the laboratory engine is planned. After which, a cost-benefit analysis is to be performed from the results. The desire for improved air balance relates to the potential for improvements to engine efficiency, emissions, detonation and misfire tolerance, and mechanical integrity.
Cost Effective NOx Emission Retrofit Control Technologies
Allen Adriani, Kirby S. Chapman, Ali Keshavarz-Kansas State University NGML/Gene McClendon & Bruce Chrisman-Cooper-Ajax
This paper discusses emission control technologies applied to a two-stroke cycle natural gas-fueled engine. In this first phase, a one-cylinder Ajax DP-115 (13 ½” bore x 16” stroke) is used to assess a variety of low-emissions technologies. These technologies are targeted to the exploration and production oil and gas field engines to meet clean air requirements. The primary goal in this project is to determine a roadmap that can use NOx reduction technologies that have been successfully used on pipeline engines on exploration and production engines, such as the Ajax. The paper describes the battery of tests that demonstrate synergies between some technologies, as well as the impact and capabilities of new technologies, such as ion sensing. The end goal is a closed loop control, low cost NOx retrofit package. The battery of tests includes a range of fuel nozzles, pre-combustion chambers, in-cylinder sensors, the means to adjust the air-to fuel ratio, and electronic fuel injection. The first series of tests will vary the air/fuel ratio and ignition timing to determine the optimal fueling rate, efficiency, and emissions from the baseline engine. Subsequent tests investigate the impact of pre-combustion chamber design, fuel nozzle design, ignition, and fuel injection, along with ion sensors and fiber optic pressure sensors to measure in-cylinder parameters in real time. The battery of tests with these technologies shows the capability of optimizing the engine and reducing NOx. By using the Ajax DP-115 as a surrogate for the smaller pipeline engines, these tests are completed in low-cost and efficient manner. The various technologies can be quickly swapped with different hardware and the cost to operate the engine is very expensive. This project is sponsored by the Department of Energy.
Development & Field Testing of Air-In-Head Starting System
Kevin White–Exline, Inc./Michael Duffy–Altronic, Inc./Chris Fitzgerald–Texas Gas Transmission
Air-in-head starting of large bore internal combustion engines has been problematic due to poor reliability, high air consumption, difficulties associated with remote starting, and dead spots on some engines. This paper describes the development, flexibility, and field test of an electronic air-in-head starting system designed to overcome these problems. It represents the first major advancement in the state-of-the-art of air-in-head starting in over 30 years. The development and operation of the system, which controls both the individual cylinder crank angle that initiates air injection, and the duration or (dwell time) of the air injected into each individual power cylinder, is described. Other design goals, such as major reduction of starting air consumption, regulation of cranking rpm, elimination of dead spots, reduction of wearing parts on the engine, and the elimination of manual barring of the engine are described, as are the hardware and software approaches embodied in the system to achieve the design goals. The resulting system knows and displays crankshaft angular position both at rest and throughout the starting process. The system regulates cranking RPM at desired values by varying the duration of the air being injected into the power cylinders. Unlike ring gear start conversions the engine purge cycle is shortened by virtue of using spent air to scavenge the cylinders. Reliance on cam lobe actuated push rods is also eliminated and reduces parasitic load on the engine. Field test results of the system on a Cooper GMW-6 in mainline gas transmission service shows up to 70% reduction in starting air consumption are also presented.
Subjects: Starting System
Development of an Open Path Laser Ignition System for a Large Bore Natural Gas Engine
Kirk Evans, Daniel Ahrens, Dan Olsen, Azer Yalin - Colorado State University
Using a laser, as opposed to a conventional (electrical) spark plug, to create a combustion initiating spark is potentially advantageous for several reasons: flexibility in choosing and optimizing the spark location, in particular to move the spark away from solid heat sinks; production of a more robust spark containing more energy; and obviation of electrode erosion problems. Design considerations for implementing open path laser ignition on a large bore natural gas engine are presented. Implementation issues and on-engine test results for laser ignition in a single cylinder of a large bore natural gas engine are discussed. The data shows that when the laser spark is optimally located in the cylinder the combustion duration is significantly shortened.
Subjects: Ignition
Randy Potter–Enginuity, LLC
The trend for new gas compression horsepower and horsepower replacement has been to retire existing reciprocating, integral, slow speed engines and to replace them with gas turbines, electric-driven compressors or high speed reciprocating engines coupled to compressor packages. The justifications for these projects have been the high cost of infrastructure required to install slow speed reciprocating engines, the inability of the integral slow speed engines to meet the new source emissions levels, the cost of upgrading and/or maintaining the existing integral units to meet new pipeline conditions, and more recently, the availability of integral reciprocating engines to purchase and install. Along with the justifications, there have been recognized penalties for replacing existing reciprocating engines: reduced flexibility to adjust to changing pipeline and operating conditions, shorter component life cycle, and reduced throughput efficiency. As replacement projects have been installed and actual operating data has become available, some of the original justifications have begun to lose their credibility and the trade-offs have grown in importance. The development and availability of new combustion and emissions control technologies for integral reciprocating engine/compressors has made it feasible to reduce NOx emissions to the sub 1.0 g/bhp-hr level and to improve the unit fuel efficiency to the sub 7000 btu/bhp-hr levels. The increasing cost of natural gas has raised the pressure on fuel efficiency and overall throughput efficiency. The performance limitations of the turbines and centrifugal compressors at off-design point conditions are becoming a larger issue as pipelines are asked to operate closer to actual certificated capacity. This paper will present case studies for the evaluation and justification of adding compressor station capacity by up-rating existing low BMEP integral reciprocating engine/compressor units and using re-manufactured, previously retired integral reciprocating engine/compressor units as the prime movers for grass roots compressor station construction.
Subjects: Horsepower Replacement
Electric Motor Conversion of 2-Stroke & 4-Stroke Integral Engines
Douglas Bird, Edward Bonham & Thomas Sine–Dresser-Rand
Other options for extending the operating life of existing integral engines is conversion to electric motor drive. This type of retrofit consists of removing power end components while retaining and utilizing frame, running gear and compressor cylinders. A synchronous or induction motor is coupled to the engine crankshaft by direct coupling, flex coupling or for low horsepower applications belt drive. Where electric utility infrastructure exists, and electricity rates are cost effective, this type of retrofit may make sense. Factors that justify this conversion are elimination of exhaust emissions, reduced maintenance and operations costs, reuse of existing frame, running fear, compressor cylinders, pulsation vessels and process piping. Additional benefits are reuse of existing foundations building infrastructure and reduced overall installation costs. The first step is a feasibility study analyzing torsional vibration, crankshaft stress, unbalanced forces and moments, starting torque, general arrangement and engine layout. In some cases, space constraints and engine layout prevent the retrofit. A secondary issue is the ability of the engine crankshaft to handle stresses and torsional vibration from a motor drive. If the crankshaft is deemed unsuitable, a new crankshaft design can be developed. Three case studies will review the retrofits of HSRA, KVSR and XVG engine models.
Subjects: Electric Motor Drives
Emissions Compliance Monitoring Options for Mid-Range Industrial Gas Turbines
Leslie Witherspoon & Anthony Jones-Solar Turbines Inc.
Emissions compliance monitoring requirements for mid-range industrial gas turbines vary significantly by application and geography. The monitoring requirements for any particular installation can be driven by local and/or federal New Source Review (NSR) requirements, Title V permit conditions, New Source Performance Standard (NSPS) requirements, and/or site specific negotiated requirements that aren’t based in regulation. While NOx (oxides of nitrogen) is typically the primary pollutant of concern, other pollutants such as carbon monoxide (CO), volatile organic compounds (VOCs), particulate matter PM10), and sulfur dioxide (SO2) are sometimes monitored as well. Emissions compliance monitoring requirements for industrial gas turbines range from no monitoring to the other extreme of a multi-pollutant Continuous Emissions Monitoring Systems (CEMs). This paper will discuss the pros and cons of various emissions monitoring options for mid-range industrial gas turbines including CEMs, Predictive Emissions Monitoring Systems (PEMs), parametric or parameter monitoring, portable analyzers, and periodic source testing. Challenging operating conditions such as low load and cold ambient temperatures will be addressed. The paper will also summarize first cost and annual operating cost estimates of each option.
Scott A. Chase & Daniel B. Olsen–Colorado State University/Mark K. Noall-El Paso Corp.
This paper describes the implementation of a retrofit micro-liter diesel pilot ignition system on a Worthington SUTC two-stroke cycle natural gas engine located in a natural gas compressor station. The engine is uniflow scavenged and has a 16” (41 cm) bore and a 16” (41 cm) stroke. It operates at 300 rpm with a nominal load of 2500 hp. The pilot fuel injectors are installed in a liquid cooled adapter mounted in a spark plug hole. The engine is equipped with dual-spark plug heads. One spark plug port is used for the pilot injector and the other contains a spark plug used to start the engine. A high pressure, common-rail, diesel fuel delivery system is employed and customizable power electronics control the current signal to the pilot injectors. Pollutant emissions and fuel consumption are measured before and after pilot ignition system installation.
Subjects: Ignition
HPFiTM Retrofit Installation Package for Miller Cycle Derivative Large Bore Engines
Grant Broughton & Gary Hutcherson–Enginuity, LLC
Focus on improved engine performance and new emissions regulations have brought higher BMEP, slow speed, large-bore, natural gas fired engines to the forefront for the next level of high-pressure fuel injection installations. Many of these higher BMEP engines operate on a derivative of an “over-expanded cycle” or “Miller Cycle” combustion process. Extending, or “over-expanding”, the expansion stroke of the combustion in relation to the intake even enhance engine fuel efficiency and performance. These performance improvements are typically at the expense of NOx emissions levels, which can reach levels in excess of 20 grams/bhp-hr. The majority of engines operating on a “Miller Cycle” approach are four-stroke class engines, with the exception of the Worthington ML line of two-stroke, uni-fow engines. While four-stroke engines have benefited from the use of exhaust gas catalytic converters and air/fuel ratio controllers with greater success than two-stroke’s resultant fuel performance, maintenance costs, and variations in exhaust temperatures limit the overall effectiveness of classic emissions reduction technologies. Implementation of high-pressure fuel injection technology on engines operating with an “over-expanded” combustion cycle has proven effective in reducing criteria pollutants emissions levels while maintaining overall engine performance. Evaluation of improved operation and performance is based upon the Nordberg FSE engines, Ingersoll-Rand KVR-KVT engine series, and Worthington ML and UTC engine series. Additional information had been obtained from the Ingersoll-Rand KVS engine series, Cooper-Bessemer LSV series engine, and Nordberg FSE series engines. Designs were based on KVR/KVT cylinder heads, both the DT and FT style cylinder heads for the KVS series engine, LSV-SG cylinder heads for the LSC series engine, and the FSE 1316 cylinder head design for the FSE series engines. All designs show unique differences in layout, design and installation. Design, development, and implementation of the various packages considered the following areas: air/fuel ratio and systems control; high pressure fuel delivery; air/fuel mixing and distribution; ignition source (high energy ignition and pre-combustion chambers); charge air requirements. For the successful completion of the project, many technical challenges had to be overcome including converting the mechanical fuel valve system to an electro-hydraulic high pressure fuel injection valve, air/fuel mixing for the combustion chamber, reliable fuel delivery given OEM cylinder head design, and adjustments made to the air delivery using existing turbochargers. This study shows the benefits to applying high-pressure fuel injection to multiple slow speed, large bore engines, which utilize an “over-expanded” cycle. These benefits are achieved without sacrificing operating costs associated with classic emission reduction technologies while meeting target emission levels.
Subjects: High Pressure Fuel Injection
Influence of Sensor Installation on Performance of Combustion Pressure Sensors
Thomas Walter–Kistler Switzerland/Dr. Bryan Willson–Colorado State University EECL/Greg Beshouri–AETC/Dr. CH. Gossweiler–Engineering School Aargau/Paul Odneal–Kistler North America
The objective of this paper is to investigate the influence of different sensor installations and sensor positions on the performance of combustion pressure sensors. Key topics to be evaluated and to be presented are: brief introduction about piezoelectric sensor technology; typical sensor installations on large gas engines; physics of acoustic oscillations and sensor mounting temperature; calculated influence of acoustic oscillations and pressure values; measured results from actual installations, and conclusions and recommendations. The paper will provide some very useful information for enhancing data as well as signal quality. Further more, it will give some recommendations for more suitable sensor installation and for generating a larger benefit for engine operators.
Subjects: Combustion, Sensors
Integrated Design Approach for Reciprocating Compressor Installation
Christine Scrivner & Ralph Harris-Southwest Research Institute
This short course will present the components of an integrated design process for reciprocating compressor installations. Several interrelated analyses will be examined in detail including acoustic analysis, cylinder performance analysis and load prediction, mechanical manifold analysis, piping layout and support review, thermal analysis, torsional analysis and skid/foundation analysis. Guidelines will be discussed that will assist with determining when a particular analysis is appropriate and how it would best be performed. A detailed description of the design methodologies and major concerns associated with each type of analysis will be presented. Case histories will be used to illustrate the key components and potential pitfalls of designing for modern high-speed installations as well as upgrading existing units.
Subjects: Acoustics, Design, Piping Systems, Reciprocating Compressors
Introduction to Vibration & Pulsation in Reciprocating Compressors
Luis De la Roche–Beta Machinery Analysis, Ltd.
This paper is intended to provide a basic understanding of pulsation and vibration in reciprocating compressor installations. Common terminology used in acoustical and mechanical analysis will also be presented.
Subjects: Pulsation, Vibration
Lateral & Torsional Vibration Problems in Systems Equipped with Variable Frequency Drives
Luis De la Roche & Brian Howes, M.Sc., P.Eng.-Beta Machinery Analysis Ltd.
Several unusual problems involving lateral vibration and torsional vibration have been seen recently in systems equipped with variable frequency drives and different types of driven equipment. The drives and motors are from different manufacturers and vary widely in size. The vibrations seem to be consistent in that there is a vibration frequency that remains constant as the shaft speed of the motor changes. Sometimes the vibrations are seen in accelerometer readings, but more consistently, the vibrations are torsional. Changes in the VFD control system have helped achieve satisfactory operating conditions in systems that originally could not run without experiencing failures. Field testing and modeling have been essential to diagnose and solve the problems.
Subjects: Vibration
A Missing Reading, A Surrogate Analysis Tool & A Paradigm for Emission Reductions
Randy Anderson–ACTT, div. of CECO
The purpose of this short course is to provide three useful tools engineers, technicians, environmentalists, operators and supervisors can find in their everyday operations to help them better understand the performance of their engines and interpret the problems easier and even remedy some of those problems. These three tools center around an engine reading that should be taken but typically isn’t (exhaust back pressure), another way to interpret oil analyses (nitration and oxidation), and another way to reduce emissions (compressor efficiency).
Subjects: Analysis, Emissions, Oil, Performance
Mitigating Turbocharger Reliability Issues on Caterpillar G3600 Series Engines
William Couch–El Paso Western Pipelines/Mitchell Opat–Universal Turbo/David Krenek– Caterpillar, Inc.
Since the introduction of the natural gas Caterpillar 3600 Series Engines in the nineties, operators of these engines with the first generation VTC turbochargers have been plagued with chronic turbocharger failures resulting from deposit buildup (fouling) on the turbine blades. This paper will briefly review and update the following: the casual factors surrounding turbocharger fouling; update population information of VTC and TPS configuration of G3600 engines; the statistics regarding the number and types of VTC turbochargers affected by the fouling buildup; discuss the costs involved in the repair/replacement of both ailing and failed turbochargers; the economics of repairing or replacing turbochargers prior to catastrophic failure; review methods of detecting eminent failure, thus allowing the turbochargers to be removed from service before a catastrophic failure. The following topics will also be reviewed and discussed in detail: the root cause of the deposit buildup on the turbine parts and review possible methods of preventing catastrophic failures of the turbochargers; methods of preventing the deposit buildup on the turbine parts with ethylene glycol and water injection and specialized blade coatings; the economics and benefits of replacing the first generation VTC turbochargers with the more fouling resistant second generation TPS turbochargers; the economics and benefits of replacing the ESS panel with Adem III panel.
Subjects: Turbochargers
Mark J. Kuzdzal & Zheji Liu-Dresser-Rand/Einar Flood, Jr.-Statoil Norway
Most industrial centrifugal compressors absorb large amounts of power and produce significant head rise. This is accomplished by imparting velocity into the working fluid using impellers and by diffusing the flow downstream of the impeller. As a result, noise is generated by the compressor as an undesirable by-product. The noise signature of a centrifugal compressor is typically dominated by the discrete frequency noise occurring at the blade passing frequency and its harmonics. Excessive noise is not only an environmental hazard but can indicate the poor health of the machine. It can take a considerable amount of resources to address the noise issue of a compressor. Historically, this challenge was addressed by treating the sound transmission path. This involves using acoustic lagging, sound insulation, sound enclosures and ear protection. In the past few years, a new centrifugal compressor noise reduction device was developed to reduce compressor noise. The intent of this device is to attenuate the noise as close as possible to the source. This approach includes mounting duct resonator arrays inside the compressor flow path to minimize the internal acoustic energy. Over the last few years, more than fifty-five centrifugal compressors, both single stage and multi-stage, have been equipped with this technology. This paper presents an application of duct resonator arrays applied to a 2528 PSIG (172 BARG) multi-stage centrifugal compressor on a platform in the North Sea. This compressor is used in a gas export process. Comparative field noise data taken from the compressor with duct resonator arrays and a second compressor, of the same design but without duct resonator arrays, will be shown in this study. The compressor with the duct resonator arrays was commissioned in September 2002 and has been successfully running. The field data presented in the paper will show that noise reduction of 12 dBA can be achieved without the use of traditional noise insulation products.
Subjects: Noise
Non-OEM Re-Rate of Centrifugal Compressor: Methods & Results
Robert Huffman-GE Oil & Gas/Marcell Minotti & Roy Smith-Florida Gas Transmission
This paper will present the methodology employed to re-rate a centrifugal compressor for increased capacity of the station. The uniqueness of this re-rate is that a company performed it other than the original equipment manufacturer and the design utilized many existing components to minimize the cost of the re-rate. Items of concern of the end user that must be addressed when this is done include reliability, performance, minimization of down time in implementing the new hardware, parts interchangeability, review of special tools requirements, updated instruction manuals and changes in maintenance methods of the equipment. The particular compressor was in operation at Florida Gas Transmission’s Station 15 at Perry, Florida. The goal of the re-rate was to optimize the throughput capacity of the compressor due to changing operational conditions. Concerns addressed were matching compressor re-design to the newly uprated capacity of the turbine, minimization of the downtime associated with obtaining the required internal dimensions, integration of the new compressor design to existing auxiliary systems to minimize changes and cost, documentation of maintenance provisions and special tools requirements. The paper will detail the process employed and discuss the results obtained. Other end users can use this information as a framework of the process and key issues to be evaluated as part of the re-rate process.
Subjects: Centrifugal Compressors
Greg Beshouri–Advanced Engine Technologies Corp./ Ed Torres–Orange County Sanitation Dist.
The natural gas pipeline industry operates the vast majority of large bore (14” bore or greater) stationary engines currently in service. Some of the engines, particularly in the northeast, have been subject to regulations requiring NOx emissions reductions down to ~3 g/BHP-HR or less. Over the past five years, the industry has achieved these levels (with varying degrees of effectiveness depending on the design characteristics of the subject engine) through the use of cost-effective emerging fuel injection technologies. While a far smaller portion of the population, other industries also operate large bore engines including Public Owned Treatment Works (POTWs). Depending on location, these engines operate under even more stringent emissions limitations on a variety of fuels. While significantly different in design from typical pipeline engines, the successful reduction of emissions from these engines offers insight into long term options for emissions reduction strategies for pipeline engines. This paper describes the system modifications made to an OEM-PCC fitted low- NOx engine to further reduce emissions to the unprecedented levels required by SCAQMD for 2004. It also describes the parametric continuous monitoring technology required to maintain compliance and optimize engine performance. A detailed evaluation of the design characteristics of the Cooper LSVB-SGC engine and the unique characteristics that facilitate very low NOx emissions without the use of add-on fuel injection technology provides insight into the fundamental mechanisms of NOx formation and reduction. The lessons learned from this case study can be applied to other engine makes and models to aid in the development of combustion modifications for NOx reduction.
Subjects: Emissions
Optimizing Peak Efficiency & Flow Range in Pipeline Centrifugal Stages
James Sorokes, Jason Kopko, Jose Gilarranz & Andrew Ranz–Dresser-Rand
Most pipeline compression systems today must operate effectively over a wide range of flow conditions. End users cannot accept a significant reduction in performance for so-called off-design operation. This demand for increased flexibility in pipeline compressor operation has forced turbomachinery suppliers to focus on attaining high efficiency over a wider flow range. This has resulted in the increased use of advanced design, analysis, and test methods in the development of pipeline stages. The paper will describe the approach taken to develop a new line of high efficiency centrifugal stages that also provide wide flow range, i.e., from surge/stall to choke. The paper will begin with a brief review of the key parameters used to assess compressor performance, such as efficiency, rise-to-surge, surge/stall margin, overload capacity, and range ratio. This discussion will then move to the various design and analysis tools applied in the development of the new stages, i.e., 1-D, 2-D, and 3-D analysis software. Analytical results for the new stages will be presented and observations will be offered regarding the typical assessment parameters applied to insure optimal efficiency and range. Next, test data gathered on the new stages will be presented and comments will be offered regarding the agreement (or lack thereof) between the analytical and test results. Of particular interest, 5-hole probes were used during the testing of the new stages allowing direct measurement of flow angles at key locations in the stage, i.e., impeller exit, return channel entrance. This permitted a direct comparison against the flow angles predicted by the analytical results. Such comparisons are atypical for production testing and represent a major step forward in the validation of new stage designs. Finally, conclusions will be drawn with respect to the success of the new stages at meeting the design objectives: increased range and efficiency. Comments will also be offered regarding the design, analysis, and test procedures used and potential improvements that could be made in the future.
Subjects: Centrifugal Compressors, Efficiency, Flow
Performance Control of Reciprocating Compressors: Devices for Managing Load & Flow
Chad Brahler, Dwayne A. Hickman, W. Norm Shade, PE & Edward J. Miller-ACI Services, Inc.
Course participants will be empowered with a fundamental knowledge for understanding the various types of unloading and capacity control devices, the ability to evaluate and compare individual product features, and the skills to identify methods and equipment for modifying and optimizing compressor performance relative to needs and budgets. Useful, objective comparisons between the various performance control devices are detailed, as well as summarized via provided quick-reference charts. In addition, this course will present, discuss, and provide technical overviews of the following: how devices operate and actuate, advantages and disadvantages, performance considerations, maintenance issues, operational limitations, practical applicability, and economic evaluation model. Upon course completion, attendees will be able to identify the best possible means to achieve optimum performance control for current, reapplied and new reciprocating compressors. Furthermore, participants will gain valuable knowledge that can be readily implemented when considering all of the economic factors affecting a company’s return on investment.
Subjects: Load, Performance
A Physical Interpretation of the Principles & Application of Rotor Dynamics
Krish Ramesh, Ph.D.–Dresser-Rand
The aim of this course is to provide a physical understanding of rotor dynamics. Rotor dynamics basically deals with the vibration characteristics of rotating machinery. This course covers the principles of lateral vibration of the turbomachinery. Since most of these machines operate in critical services in the oil and gas industries, one has to ensure that the machines operate with a high degree of reliability. The dynamic characteristics of the turbomachinery need to be completely understood before the machine is placed in service. A basic knowledge of the underlying principles of the rotor dynamics will help in a better understanding of the behavior of rotating machinery. This course is intended for rotating equipment personnel, project and facility engineers, and other personnel responsible for rotating machinery systems.
Subjects: Rotor Dynamics
Predicting Exhaust Gas Temperatures for Lean Burn Two-Stroke Engines
Reagan Mayces & Dustin Malicke-Hoerbiger Gas Engine Systems Div./Kirby Chapman-Kansas State University NGML
This paper focuses on the techniques used for predicting exhaust gas temperatures for lean burn two stroke engines. When planning for emissions retrofits, it is often necessary to upgrade the turbocharger system, dramatically changing the air manifold pressure and scavenging flow of the two-stroke engine. Proper matching of the turbocharger requires accurate prediction of the post retrofit exhaust gas temperatures. Predicting exhaust gas temperatures for a lean burn two stroke is difficult. Modeling the combustion and blow down process is complex and varies among unit types. Further complicating modeling is that the only reference data is typically exhaust elbow temperatures. These temperatures represent some average of blow down temperature and scavenging temperature for the unit. Hoerbiger’s Gas Engine Systems has developed a simplified model that combines theoretical expectations and empirical data to accurately predict post retrofit exhaust gas temperatures. The model focuses on gross combustion process analysis and then uses correction factors to tailor the results for each unit type. The model equations and matching techniques are presented in their entirety. Several case studies are presented, including the use of non-turbocharged data to predict turbocharged results.
Subjects: Exhaust
Recip Pulsation Vibration Troubleshooting: A Practical Approach
Frank Fifer–Peerless Dynamics, LLC
Practical field troubleshooting techniques will be discussed followed by case studies of real vibration problems where the class will be challenged to come up with the solutions.
Subjects: Pulsation, Troubleshooting, Vibration
Reciprocating Compressor Sizing & Evaluation
Hasu Gajjar-Hasu Gajjar & Associates, Inc.
Correct sizing of gas compression equipment for each individual application is a critical factor for efficiency and cost effectiveness. This course examines on general terms theoretical compression applications set on commonly-used parameters and then presents a comparison of various sizing programs presently available from compressor OEMs. The course will provide an engineer the basic knowledge necessary to size, evaluate, and select compression.
Subjects: Compressor Sizing
Reciprocating Compressor Valve Plate Life & Performance Analysis
Klaus Brun, Ph.D., Anthony J. Smalley, Ph.D.–Southwest Research Institute/John Platt, PE–BP
To better understand the factors that affect reciprocating compressor valve performance and life, GMRC, BP, and SwRI have initiated a program to systematically investigate the physical behavior of valve plates during compressor operation. A reciprocating compressor’s valve life is generally considered to be a function of the plate’s cyclic kinematics behavior and material properties. Thus, transient stresses of valve plates were measured in controlled single impact tests. By mounting a complete valve assembly in front of a burst-membrane shock-tube and instrumenting the valve with multiples optical probes, detailed 3-D motion and plate transient strain data for controlled single impact events of a valve plate were obtained. The transient strain data for these single impact tests, determined from three strain gauges strategically located on the valve plate, was correlated to the kinematics behavior of the plate. Results from these tests were then employed to calibrate and verify a dynamic finite element calculation of valve plate single impact events. The measured and the finite element model results were found to agree within the measurement uncertainty. Parametric finite element studies were performed to determine the effects of plate angle, impact velocity, and plate position on the transient stresses and to develop some generalized relationships for plate motion versus transient stresses. These relationships, in combination with plate material properties, can be employed to predict the plate life based on operating conditions and design.
Subjects: Valve Plates, Valves
K.E. Atkins, PE-Engineering Dynamics, Inc./Martin Hinchliff-Dresser-Rand/Bruce McCain-Oxy
Reciprocating compressors are usually rated in terms of horsepower, speed and rod load. Horsepower and speed are easily understood; however, the term “rod load” has many different meanings to many different people. This paper will discuss the various definitions of rod load, including historical and current API definitions, manufacturer’s ratings, and various user interpretations. The basic kinematics of a slider-crank mechanism will be reviewed to provide a better understanding of the various definitions that are used. Analytical results and field rod load measurements will be compared to illustrate the various factors that influence rod load on typical compressor installations.
Subjects: Rod Load
Solid Rider Bands: Considerations for Installation
Tim Bremner–Hoerbiger America Rings & Packing
The installation of solid rider bands on hollow cast pistons is not ranked among the simplest operations in compressor repair, especially with large piston diameters and thick rider band profiles. Innovative methods have been developed for such installations, but many have the potential to permanently damage the rider band and potentially reduce its service life. This discussion presents a number of practical considerations in solid rider band material selection and installation that will prevent damage. Additionally, developments in materials and pre-stretching technologies aimed at simplifying the installation procedures in the field will be discussed.
Subjects: Rider Bands
Surge Protection in Centrifugal Compressor Systems
Rainer Kurz & R. C. White–Solar Turbines Inc.
Centrifugal compressor surge and its prevention have drawn significant attention from manufacturers and users. An important aspect of surge avoidance lies in the design of the compressor station and, in particular, the piping upstream and downstream of the compressor. Most anti-surge systems are perfectly capable of avoiding surge during normal operating conditions. However, unplanned emergency shutdowns present a significant challenge, and surge avoidance in these cases depends to a large degree on the station layout. In this paper, data from a compressor that surged during an emergency shutdown are presented. The data are analyzed to determine the effects of surge and the rate of deceleration. Simple rules that help with proper sizing of upstream and downstream piping systems, as well as the necessary control elements are described. Furthermore, recommendations to avoid problems at start-up, as well as control problems during normal operation, are given.
Subjects: Centrifugal Compressors, Surge Control
Technologies to Enhance Operation of the Existing Natural Gas Compression Infrastructure
Ralph E. Harris & Danny M. Deffenbaugh–Southwest Research Institute/Anthony J. Smalley-Consultant
This paper addresses the opportunities to increase pipeline capacity by increasing overall efficiency of pipeline compressors. As a result of early road-mapping, DOE’s Natural Gas Infrastructure Reliability Program set a goal to increase pipeline capacity ten percent without changing the infrastructure. At any time, the useful compression power available from pipeline compressor drivers set a limit on the system’s maximum capacity. In its third year, the project “Technologies to Enhance Operation of the Existing Natural Gas Compression Infrastructure” has emphasized reducing compression losses; these losses limit useful gas compression power and thereby limit capacity. Some years ago, a survey by GMRC showed that integral reciprocating compressors can achieve 90 to 92 percent thermal efficiency in pipeline service. However, the median lay far below this benchmark, leaving substantial system-wide opportunity for improvement. The paper reviews the numerous contributors to compressor losses, overviews technologies to measure them, and discusses the opportunities for their cost-effective, documentable reduction. Recent program tests on three different, but widely deployed, integral engine/compressor models have confirmed achievability of over 90 percent s a benchmark thermal efficiency. Through an initial screening process, the research program will identify a target compressor, whose thermal efficiency lies well below the benchmark. Detailed testing on the selected compressor, followed by a design study will quantify the opportunities for beneficial change, both within the compressor cylinders and in the compressor installation (nozzle, manifold, pulsation control hardware, and laterals). Further tests will quantify the efficiency increase achieved by implementing these changes. After its review of compression losses, the paper presents evolving progress in implementing this plan.
Subjects: Infrastructure
Turbocharging a Low BMEP Pump Scavenged Engine
Damian Kuiper & David Stickler–DigiCon/Randy Potter–Enginuity/Jonathan Goss–El Paso Corp.
Increasingly stringent emissions standards are continually driving the natural gas industry to seek cost-effective methods of reducing environmentally harmful pollutants. It is widely known that the two significant contributors to air pollution are NOx and CO. NOx formation is exponentially dependent on temperature and time. The combustion temperatures which provide the environment where oxides of nitrogen form are directly linked to the equivalence ratio. CO formation is dependent on combustion efficiency as a function of mixing, ignition energy, cylinder temperature and, therefore, equivalence ratio. Thus, engine operation under a leaner equivalence (air/fuel) ratio effectively reducing combustion temperatures can decrease NOx and CO production. To meet these desired operating conditions, a turbocharger in combination with enhanced mixing nozzles were installed directly to a Worthington LTC 2-stroke, spark ignition, direct injection engine. Turbocharger installation in combination with modified port geometry allows for a higher air manifold pressure increasing the trapped air/fuel ratio as well as increasing the engine air through flow improving cylinder scavenging. By supplying fuel at injection speeds greater than Mach and boosting engine air through flow, NOx and CO emissions were reduced – but not without a few technical challenges. Low BMEP internal combustion engines such as the Worthington LTC have less energy available due to their low operating efficiency. This reduces the available energy within the exhaust stream and therefore reduces the available work delivered to the turbocharger turbine and compressor. To account for and overcome this challenge, the design team implemented modifications to the piston, intake port and exhaust port geometry. Utilizing parametric modeling and computational fluid dynamic (CFD) software, the intake, exhaust and mixing processes are completely visualized ensuring that desired flow characteristics are employed by the geometric modifications made to the cylinder piston and liner.
Subjects: Turbochargers
Virtual Pipeline System Testbed for Non-Thermal Transient Simulation
Kirby Chapman, Prakash Kirishnaswami & Mohammad Abbaspour–Kansas State University NGML
A review of project titled “Virtual Pipeline System Testbed (VPST) to Optimize the U.S. Natural Gas Transmission Pipeline System” is presented in this paper. The goal of this project was to develop a Virtual Pipeline System Testbed (VPST) for natural gas transmission. This testbed simulates compressor stations, the pipe that connects these compressor stations, the supply sources, and the end-user demand markets. The compressor station was described by identifying the make, model, and number of engines, gas turbines, and compressors (centrifugal and reciprocating) that the station is comprised, System operators and engineers are able to analyze the impact of system changes on the dynamic deliverability of gas and on the environment. For example, the users of the virtual pipeline system are able to drill down into a compressor station to describe that compressor station with a high degree of detail. The VPST also includes optimization algorithms to identify the most reliable and lowest cost path to deliver natural gas to the costumer.
Subjects: Reliability
