AN IMPROVED THRUST PREDICTION MODEL FOR HIGH PRESSURE MULTI-STAGE CENTRIFUGAL COMPRESSORS
(2022) Srinivasan, Anand; Fowler, Edward J.; Marechale, Russell K.
Axial thrust load predictions are an important aspect when it comes to predicting the performance of centrifugal compressors. The accurate prediction of axial thrust forces is necessary to size the appropriate balance piston and the thrust bearing dimensions for the operating limits of the compressor. Inline centrifugal compressors utilized for pipeline compression (and multistage upstream & midstream applications) often have a range of operating conditions, varying in flow, speed and discharge pressure (in addition to other variables such as gas composition and ambient conditions). The ability to accurately predict thrust loads over these ranges is thus important, especially at discharge pressures exceeding 3,000 psia [207 bar]. The key to predicting axial thrust forces lies in estimating the swirl ratio in the front and rear cavities of a shrouded impeller. This paper presents the modeling techniques for the prediction of swirl ratios in cavities as validated with scaled testing at the original equipment manufacturer’s (OEM) facility. The extension of this proposed model for full-scale compressor models, along with test results on high pressure compressors operating at 4,285 psia [295 bar] has also been presented. The ability to validate thrust modeling procedures in the absence of load cell measurements from thrust bearings is detailed in this paper.
Rotordynamic Stability Of A Rotor With Three Open Impellers, Validated By Magnetic Bearing Exciter During Full Load Full Pressure (Flfp) Testing
(Turbomachinery Laboratory, Texas A&M Engineering Experiment Station, 2022) Wu, Tingcheng; Kuzdzal, Mark J.
As speed and power density increase, open (unshrouded) impellers are becoming more and more utilized in process gas compressors. Open impellers enable higher tip speeds and more aerodynamic head per stage than closed impellers. However, the industry still lacks maturity and experience of rotordynamic stability assessment with single shaft multistage compressors when open impellers are used. To accurately assess the stability of compressors with open impellers, the estimation of the destabilizing fluid force induced by open impellers is important. The American Petroleum Institute (API) uses the anticipated cross-coupling (QA) to estimate the induced rotordynamic destabilizing forces, whereas this empirical QA number was initially derived for applications with closed (shrouded) impellers. This paper presents the measured and predicted stability (log dec.) results from a full-load, full-pressure test with a magnetic bearing exciter of a 6 stage back-to-back centrifugal compressor for natural gas processing. The compressor has three open impellers in the first section, and (three) closed impellers in the second section. The unit was tested to 17,800 RPM with a shaft end horsepower of 20,500 HP (15.3 MW). The labyrinth seals at interstage and balance piston locations are equipped with swirl brakes to reduce the cross-coupled effects. The magnetic bearing exciter (MBE) test provides the rotor stability results and thus helps to confirm calculated impeller induced destabilizing forces. The comparison of the impeller-induced destabilizing forces (Kxy obtained through different methods, namely, PACC (Predicted Aerodynamic Cross-Coupling), Wachel, CFD (Computational Fluid Dynamics), and measurements, gives Copyright© 2022 by Siemens-Energy & Turbomachinery Laboratory, Texas A&M Engineering Experiment Station -- 2 the industry insight into the open impellers and their induced destabilizing forces. This paper provides additional test data in the open literature.
Methods to Determine and Specify Rotodynamic Pump Dynamic Analysis
(Turbomachinery Laboratory, Texas A&M Engineering Experiment Station, 2022) Gaydon, Peter; Claxton, Jack; Cropper, Mike; Marscher, Bill
Vibration caused by resonance is an industry problem for new and retrofit applications that persists due to lack of specification and upfront analysis. To limit the chances of resonant vibration, dynamic analysis of the structure and rotating assembly to evaluate structural, rotor lateral and rotor torsional frequencies is done when the pump installation “warrants” it. However, dynamic analyses take time, require expertise, and cost money: It is not always clear when a pump is purchased if the installation warrants the expense of analysis. Furthermore, the purchaser may not know what type and levels of dynamic analysis should be specified. This results in poor specification, missed specification or specification of analysis when it is not needed. ANSI/HI 9.6.8 Rotodynamic Pumps – Guidelines for Dynamics of Pumping Machinery is the first American National Standard to cover this topic; it provides methods to evaluate the risk and uncertainty of a pump installation. A standard specification template is provided to aid the user. This tutorial will address the issue of resonance, review the importance of the guideline, how to apply the guideline, and risk factors, levels of analysis and methodology. Case studies are also provided.
Visualization Of Oil-Water Emulsion Formation In A Centrifugal Pump Stage
(Turbomachinery Laboratory, Texas A&M Engineering Experiment Station, 2022) Perissinotto, Rodolfo Marcilli; de Cerqueira, Rafael Franklin Lazaro; Verde, William Monte; Biazussi, Jorge Luiz; Bannwart, Antonio Carlos; de Castro, Marcelo Souza
Electrical submersible pumps are assembled in oil wells to act as artificial lift methods. When water is present in the reservoir, oil-water emulsions are formed in the pump. These two-phase mixtures affect the performance and promote instabilities that lead the machine to operate inefficiently and fail prematurely. Therefore, this paper aims to investigate the formation of emulsions and behavior of mineral oil drops in a transparent centrifugal pump through a flow visualization approach. Shut-off, best efficiency point, and open-flow condi tions are investigated at three impeller rotational speeds with high-speed imaging and particle image velocimetry. As the oil fraction increases, large drops accumulate in the impeller channels, while some escape to the volute and circulate until the water flow carries them out of the pump stage. Regions with vortices and water recirculation explain the accumulation of oil drops in the impeller and reduced pump performance at low water flow rates. Intense velocity fluctuations at the impeller and impeller-volute boundary indicate the main causes for oil drop rotation, deformation, and fragmentation at high water flow rates. The new findings can be used to improve models and numerical simulations for pumps operating with multiphase flows and help the creation of new pump designs.
An End-User's Guide to Centrifugal Pump Rotordynamics
(Turbomachinery Laboratory, Texas A&M Engineering Experiment Station, 2022) Marscher, William D.; Onari, Maki M.
This tutorial outlines the basics of pump rotordynamics in a form that is intended to be Machinery End User friendly. Key concepts will be defined in understandable terms, and analysis and testing options will be presented in summary form. The presentation will explain the reasoning behind the HI, ISO, and API-610 rotor and structural vibration evaluation requirements, and will summarize key portions of API-RP-684 “API Standard Paragraphs Covering Rotordynamics” as it applies to pumps. Pump rotordynamic problems, including the bearing and seal failure problems that they may cause, are responsible for a significant amount of the maintenance budget and lost-opportunity cost at many refineries and electric utilities. This tutorial discusses the typical types of pumps rotordynamic problems, and how they can be avoided in most cases by applying the right kinds of vibration analysis and evaluation criteria during the pump design and selection/ application process. Although End Users seldom are directly involved in designing a pump, it is becoming more typical that the reliability-conscious End User or his consultant will audit whether the OEM has performed due diligence in the course of pump design. In the case of rotordynamics, important issues include where the pump is operating on its curve (preferably close to BEP), how close the pump rotor critical speeds and rotor-support structural natural frequencies are to running speed or other strong forcing frequencies, how much vibration will occur at bearings or within close running clearances for expected worst-case imbalance and misalignment, and whether or not the rotor system is likely to behave in a stable, predictable manner. When and why rotordynamics analysis or finite element analysis might be performed will be discussed, as well as what kinds of information these analyses can provide to an end-user that could be critical to reliable and trouble-free operation. A specific case history will be presented of a typical problematic situation that plants have faced, and what types of solution options were effective at providing a permanent fix.
High Temperature Sealing Advancements Utilizing Non-Contacting Gas Seal Technology
(Turbomachinery Laboratory, Texas A&M Engineering Experiment Station, 2022) McManus, Robert F.; Butler, Brian M.
Non-contacting dual pressurized gas lubricated seals for use in pumps have been in service since the early 1990’s. The application of these seal designs has expanded over time into very high temperature applications up to 800°F (425°C) where emissions, pumped fluid contamination and overall operating/lifecycle costs are a major concern. Sealing technology using metal bellows is needed due to the high process fluid pumping temperatures, mainly in the oil and gas refining and petrochemical industries. Traditional non-contacting gas seal designs utilize a non-interference fitted seal ring to a seal ring adapter. Reliability issues have been encountered with non interference fitted seal ring assemblies in hot, dirty services. The predominant factor affecting long term reliability of the mechanical seal has been seal ring distortion caused by a build-up of hard particulate from the process fluid in the region of the non-interference fitted seal ring to seal ring adapter assembly. The distortion can lead to higher than desirable barrier gas consumption rates, a loss of non-contacting seal operation and reduced mean-time-between-repair (MTBR). Recent advancements have been made in high temperature non-contacting gas lubricated seal technology for industrial use in pumps and other rotating equipment. A study of the latest technology is provided, particularly in the design of an interference fitted seal ring adapter assembly for high temperature non-contacting gas seal design which is both thermally compliant and pressure stable in these applications.
Refrigeration Compressor Basics For The Oil And Gas Industries
(Turbomachinery Laboratory, Texas A&M Engineering Experiment Station, 2022) Zaghloul, Medhat; Jacobson, Wayne
This tutorial discusses the design basics for refrigeration compressors, using the 2â€�section Propane refrigeration configuration as an example. The benefits of incorporating a flash gas Economizer are discussed, as are the various methods of controlling the performance these machines, with the pros and cons for each method analyzed. The proper antisurge control design is developed and correct recycle line arrangements are presented. A case study of incorrect recycle line arrangements for a Single Mixed Refrigeration (SMR) Compressor, and the proposed modifications, is also presented.
Precision Grouting of Turbomachinery
(Turbomachinery Laboratory, Texas A&M Engineering Experiment Station, 2022) Goodwin, Fred; Termunde, Dan; First, Rick
Rotating equipment being installed in industrial environments, including refineries and chemical processing plants, are critically aligned with exact tolerances. When in operation, this equipment experiences heavy dynamic and repetitive loading with high vibration, and in some cases, high temperatures and chemical exposure. Due to these extreme forces and environments, this equipment requires maximum support by using a high-quality precision grout able to properly transfer those forces, providing a long-term solution resulting in maximum operation efficiency, increased reliability, and reduced maintenance. Techniques to utilize epoxy grouts will be described to provide adequate equipment support.
Factors Influencing the Accuracy of Turbomachinery Aerodynamic Performance Predictions
(Turbomachinery Laboratory, Texas A&M Engineering Experiment Station, 2022) Aikens, Kurt; MacWilliams, Scott; Gilarranz, Jose; Sorokes, James M.; Hermes, Viktor
This tutorial delves into the factors that impact the accuracy of turbomachinery performance predictions. The discussion is broken down into three partsâ€¦ the influence of engineering tools / procedures, the impact of the various manufacturing processes and the uncertainties associated with performance testing. Under the engineering portion, the discussion focuses on the inaccuracies that can result from modeling assumptions or the computational methods themselves. The manufacturing segment explains how construction or machining techniques can yield parts that vary from the designs provided by engineering. Finally, the test portion provides an overview of the uncertainties associated with test methods, procedures, and instrumentation. The objective of the tutorial is to give readers a better appreciation of the role each of these considerations play in the prediction accuracy.
Performance Of Industrial Gas turbines
(Turbomachinery Laboratory, Texas A&M Engineering Experiment Station, 2022) Kurz, Rainer; Reitz, Daniel; Burnes, Daniel
Industrial gas turbines have performance characteristics that distinctly depend on ambient and operating conditions. Application of these gas turbines, as well as the control and condition monitoring, require to consider the influence of site elevation, ambient temperature and relative humidity, the speed of the driven equipment, the fuel, and the load conditions. The reasons for these performance characteristics can be explained by the behavior the gas turbine components and their interaction. The tutorial explains the performance characteristics based on the performance of the engine compressor, the combustor and the turbine section, and certain control strategies. It introduces fundamental concepts that help to understand the flow of energy between the components. Further discussed are control concepts, both for single shaft and two shaft machines, driving generators, compressors, or pumps. Methods are introduced that allow to use performance data for trending and comparison purposes. The impact of component degradation on individual component performance, as well as overall engine performance is discussed, together with strategies to reduce the impact of degradation.
Compression Turbomachinery For The Decarbonizing World
(Turbomachinery Laboratory, Texas A&M Engineering Experiment Station, 2022) Kurz, Rainer; Allison, Tim; Moore, Jeff; McBain, Marybeth
In the context of carbon reduction efforts, discussions evolve around hydrogen compression, as well as compression requirements related to CO2 capture, transportation and sequestration. In this paper, compression requirements for various aspects of these applications are discussed, and the energy intensity of various energy transport configurations is compared. Carbon sequestration by capturing, transporting and sequestering CO2 from the exhaust of fossil fired power plants, from the generation of blue hydrogen, or the generation of Ammonia is discussed. Compression duties include the compression from capture pressure to pipeline pressure, the boost compression as part of the pipeline transport, and the compression required to sequester the CO2. Issues addressed in this part include the relative effort required based on the CO2 concentration in the exhaust, and methods to compress CO2and CO2 mixtures from close to atmospheric pressure to pipeline pressure. In this discussion, the option of transporting hydrogen to apower plant versus transporting natural gas to said power plant, and transporting captured CO2 back to a sequestration site, has to be evaluated. The use and creation of hydrogen imposes specific questions on the use of turbocompressors. These questions involve the requirement to compress hydrogen for significant pressure ratios from production to a pipeline, the impact of transporting hydrogen in pipelines, and the compression from pipeline pressure to storage or vehicle fuel tank pressure. Part of the discussion is also the location of blue hydrogen production versus green hydrogen production, based on the fact that transport of CO2 or natural gas requires less energy than the transport of hydrogen.
Thermo-Structural Analysis Of Steam Tracing Arrangements Applied To Pump Barrels
(Turbomachinery Laboratory, Texas A&M Engineering Experiment Station, 2022) De Francesco, Francesco; Annese, Francesco; Da Soghe, Riccardo; Mazzei, Lorenzo; Brizzi, Rita
Pumps steam tracing is widely used in Oil&Gas industry for critical services in which the process fluid requires a minimum temperature to avoid its crystallization during stand-by. This paper describes the process of utilizing Computational Fluid Dynamics to perform a thermo-structural analysis of a barrel pump to determine the optimal steam tracing arrangement to maintain a minimum internal temperature. The most critical part of the analysis was to define the Heat Transfer Coefficient of the entire system. The computations consisted in conjugate Computational Fluid Dynamics solutions involving the ambient temperature and wind distribution, the skid dimensions and arrangement (barrels materials), the tracing system (carbon steel piping), the insulation (Mineral Wool) and the fluid compartments, both steam inside the piping and air in the gaps. The steam was modelled as a single-phase fluid with properties defined to consider the latent heat of condensation
Prediction Of Lateral Vibration Behavior Of Integrally Geared Centrifugal Compressor During Synchronous Motor Startup By Transient Torsional-Lateral Coupled Analysis
(Turbomachinery Laboratory, Texas A&M Engineering Experiment Station, 2022) Adachi, Akira; Baba, Yoshitaka
Startup transients of both torsional and lateral vibration behaviors of an integrally geared centrifugal compressor driven by a synchronous motor are examined by transient torsional-lateral coupled analyses, and the numerical calculation results are evaluated using the field measurements as a benchmark. Since linear bearing coefficients are employed in the numerical simulation instead of more sophisticated nonlinear bearing model, bilinear stiffness is additionally considered to reflect the effects of the rotor confinement within the bearing clearance. Moreover, temporary teeth separation of the gear meshing and engagement at the backside during torque reversal is also considered in the numerical calculation. The transient lateral vibration behavior of the pinion rotor during the synchronous motorâ€™s startup is successfully replicated. Both (a) bilinear stiffness of the pinion rotor bearings due to rotor restraint within the bearing clearance, and (b) effect of temporary teeth separation within the backlash and engagement at the backside because of torque reversal, are found to strongly influence the numerical predictions.
Annular Clearance Gas Seals In The 21st Century: A REVIEW OF THE EXPERIMENTAL RECORD ON LEAKAGE AND DYNAMIC FORCE COEFFICIENTS, INCLUDING COMPARISONS OF MODEL PREDICTIONS TO TEST DATA
(Turbomachinery Laboratory, Texas A&M Engineering Experiment Station, 2022) San Andres, Luis; Delgado, Adolfo
Turbomachinery seals are engineered to maintain efficiency and power delivery by minimizing leakage. Seals also appreciably affect the system rotordynamic behavior due to their relative position within a turbomachine. The tutorial reviews the experimental record on gas seals as published in the 21st century, and gives insight on the physical models predicting leakage and dynamic force coefficients. Simple leakage and transport equations are the basis for bulk flow models (BFMs), whereas computational fluid dynamics (CFD) software relies on the solution of the Reynolds-Averaged Navier-Stokes equations (RANS) with an appropriate turbulence flow model in a multi-million node mesh count. Leakage data for seals with nominal clearance (Cr) include labyrinth and interlocking labyrinth seals, damper seals such as honeycomb (HS), pocket damper seals (PDS), conventional and hybrid brush seals, and the advanced (clearance control) HALO seal. A flow factor characterizes the seals as a single-knife (restriction) with an effective clearance (Ce). The extensive comparisons of leakage, measured and predicted, show that engineered seals have an effective clearance Ce/Cr = 0.30 - 0.40, and which is not a function of either inlet pressure, exit pressure, rotor speed, or even actual clearance. The finding attests to the well-understood nature of the fluid flow through the seals. Both BFM and CFD models accurately predict seal leakage. Seals produce reaction forces due to shaft lateral displacements, and with stiffness and damping coefficients characterizing a seal dynamic response. A direct stiffness (K) produces a centering action whereas a direct damping (C) dissipates mechanical energy. A cross-coupled stiffness (k) arises due to shaft rotation dragging the gas around the seal circumference. In general, the force coefficients of a gas seal are frequency (ï�·) dependent. A positive k (>0) decreases the seal effective damping Ceff = (C-k/ï�·), hence degrading the stability of the mechanical element. k is proportional to the gas circumferential speed entering the seal; hence, adding either a swirl-brake or shunt-injection with (excess) gas flowing in the direction opposite to shaft rotation helps to diminish k (ïƒ 0 or negative). The tutorial reviews multiple examples of normalized stiffness and damping coefficients for various seal types including uniform clearance seals, LS, and damper seals (HS and PDS). LS with teeth on the rotor surface are notorious for producing large k. Poorly designed LS, installed as either balance piston seals or impeller eye seals, are the cause of many rotordynamic instability fiascos. Damper seals produce direct K and C orders of magnitude larger than those from conventional LS. Damper seals in conjunction with a swirl brake also produce very small k; hence, effectively removing a concern on rotordynamic instability. Past are the days when LS, known bad actors, were the only choice effectively sealing the stages in a turbomachine. Incidentally, damper seals, honeycomb and hole-pattern seals in particular, can produce a large centering stiffness (K>>0 ) that makes a balance piston seal in a back-to-back centrifugal compressor act as a third bearing, hence rising the first natural frequency of the rotor system. Although both the BFM and CFD models are good at predicting leakage, they fall short of replicating the experimental force coefficients of damper seals. At times, C is accurately predicted while K or k are not, or vice versa. The predictive methods still need improvement, hence the need of constant and continuous experimental verification. Differences between predictions and measured force coefficients are likely due to the lack of fidelity in reproducing complex unsteady (highly turbulent) flows whose dynamic pressure acting on the rotor produces the seal reaction force. Derived from the comprehensive experimental results, the review concludes by advancing rules of thumb to estimate the range of expected direct stiffness (K) and effective damping (Ceff) applicable to damper seals. Unlike experiences in the past century, damper seals offer a remarkable opportunity to control the leakage and tailor the rotordynamic performance and stability of modern rotating machinery.
Centrifugal Compressor Configuration, Selection And Arrangement: A User's Perspective
(Turbomachinery Laboratory, Texas A&M Engineering Experiment Station, 2022) Sandberg, Mark R.
The detailed sizing and selection of centrifugal compressors may be somewhat of a mystery to the typical user. Once the suction and discharge process conditions and required flow rates are established, they are submitted to an equipment supplier for sizing and selection. The resulting combination of impeller diameters, casing sizes and operating speed determined by the equipment supplier can be puzzling to the engineer charged with evaluating the selections. This tutorial is intended to introduce the dimensional and dimensionless similarity parameters that can be utilized to perform an independent, equivalent selection for a compression application or provide a more thorough evaluation of the selections provided by an equipment supplier. These performance parameters will allow prediction of design point head and efficiency, approximate impeller diameters, and approximate compressor operating speeds. Furthermore, the inter-relationship between impeller diameter and rotational speed will be investigated to highlight the trade-offs in changing either of these design variables. The tutorial will also investigate useful mechanical parameters and guidelines that allow comparative preliminary assessment of proposed designs. When significant head and/or flow requirements exist for a specific application, it becomes necessary to divide the compression service into multiple sections and in some situations multiple casings. Although a few different ways to configure multiple compressor sections exist, there are benefits and issues associated with each of these configurations. The potential benefits and issues of different arrangement options will also be addressed in this tutorial.
Predicting And Correcting Nonlinear Vibration Growth In Tilting Pad Journal Bearings Undergoing Large-Amplitude Whirl
(Turbomachinery Laboratory, Texas A&M Engineering Experiment Station, 2022) Armentrout, Richard
When machines equipped with tilting pad bearings are well enough balanced to limit the journal whirl amplitudes to less than 40% to 50% of the bearing clearance, the bearing behavior can usually be considered linear and the pad pivots usually stay loaded radially against the bearing housing without pivot separation. However, if unbalance or other excitations impose higher journal whirl amplitudes that exceed 50% of the bearing clearance, pivot separation or â€œrattleâ€� can occur between the pad pivots and the supporting bearing housing, leading to increased clearances and vibration. Along with pivot separation, nonlinear bearing stiffening under increasing whirl amplitudes can elevate the critical speed in parallel with the running speed, leading to violent motions at a point of response instability often referred to as a â€œnonlinear jumpâ€�. A 35-year-old case study of a single-stage overhung compressor is revisited to investigate whether the above phenomena played a role in compromising the original machineâ€™s longevity. The compressor experienced a high unbalance condition due to abrasive erosion of the impeller. The resulting increase in journal motion lead to rapid pivot wear within the original rocker-pivot tilting pad bearings, causing repeated unplanned shutdowns. Basic linear analyses conducted 35 years ago provided bearing and shaft upgrades that were sufficient to restore the machineâ€™s reliability at the time. However, a new rotordynamic model having the ability to represent tilting pad bearing nonlinearity has deepened the understanding beyond that of the original linear study. After a summary of its theoretical basis, the new model is exercised to illustrate the potential for nonlinear bearing behavior in the original machine, and subsequently to demonstrate the benefits of additional bearing modifications in mitigating the nonlinear behavior even more effectively than the original shaft modifications performed 35 years ago
Measurement And Calculation Of A Self-Equalized Tilting-Pad Thrust Bearing Under Static Misalignment
(Turbomachinery Laboratory, Texas A&M Engineering Experiment Station, 2022) Havlik, Nico; Kraft, Christian; Winking, Philipp Sebastian; Schwarze, Hubert; Lindloff, Kai
Tilting-pad thrust bearings which include a self-equalizing feature, ensure reliable and safe operation especially under conditions on which misalignment between bearing and collar occurs. One common method to incorporate such a self-equalizing feature to a thrust tilting-pad bearing is the usage of leveling links. Radii and spherical contacts ensure a free rolling surface between the links, thrust pads and bearing housing. However, the verification whether a design works properly can be relatively challenging. For example, the friction forces between all the radii contacts always lead to different residual misalignments between the pads. This leads to a periodic rotational distribution of the hydrodynamic pressure and thus to different temperatures of each pad. This paper shows detailed measurements of a self-equalizing thrust tilting-pad bearing using leveling links. The test campaign includes a wide range of bearing to collar misalignment and operating conditions. The measurements show, that such a mechanical equalizing-mechanism may sufficiently balance very large deflections, despite the fact, that the residual pad misalignment of each pad due to friction lead to a relative high temperature difference between the pads. Furthermore, the paper presents a methodology of calculating the bearing behavior of self-equalizing thrust bearings to generate a better understanding and assessment of the proper function of such a bearing design. It presents the development of a mechanical model, which can iteratively solve a FEA software and a thermo-elastic-hydrodynamic (TEHD) software for fluid-film bearings.
Materials And Coatings For Turbomachinery In Hydrogen Applications
(Turbomachinery Laboratory, Texas A&M Engineering Experiment Station, 2022) Bauer, Derrick
Centrifugal compressors are commonly utilized for hydrogen compression in refineries for critical applications, and a potential â€œHydrogen Economyâ€� to lowering the carbon footprint on a worldwide scale will require compression of hydrogen to even higher pressures. Provided that the temperature is kept below 200Â°C (392Â°F), relatively standard materials that are currently utilized in hydrogen compression and transportation can be utilized at pressures up to 69 MPa (10 ksi). There is an extensive service history of centrifugal compressors which utilize carbon steel casings in a hydrogen environment, and API 941 has recognized that standard carbon steel can be used at these conditions. Carbon steel is used for the pressure-containing components such as the process piping and the centrifugal compressor casing. Higher strength steels can be used for the rotating components provided that they have a maximum yield strength of 827 MPa (120 ksi). While this provides a method to compress the hydrogen for transportation and storage, the yield strength requirement limits the maximum performance of the compressor and results in the need for more compression stages or additional compressors to be utilized to achieve a desired storage or transportation pressure. Efforts are underway to find a material with a higher strength that it suitable for hydrogen compression.
An Overview of the Design and Performance Testing of a 275 BAR Integrally Geared Supercritical CO2 Compressor for Power Generation
(Turbomachinery Laboratory, Texas A&M Engineering Experiment Station, 2022) Wilkes, Jason C.; Pelton, Robert; Wygant, Karl
An integrally geared compressor-expander (compander) for supercritical CO2 (sCO2) was developed to convert thermal energy to electricity. With operating pressures of 275 bar, this turbomachine represents the state of the art in integrally geared machine architecture, hitting compressor inlet densities of 600 kg/m3 and discharge pressures of 275 bar. The product development was funded by the Department of Energyâ€™s Energy Efficiency and Renewable Energy Office under EE0007114 to advance the state of the art in concentrated solar power applications; however, the technology itself is agnostic to heat source, and is predicted to achieve a thermal-to-electric conversion efficiency of 50% for any indirect heat source capable of providing turbine inlet temperatures of 700Â°C or greater. While the program encompassed the design and testing for the compressor and turbine elements, this paper will focus on the compressor design and operation. The paper will begin with an introduction to the cycle design and analysis of an indirectly heated integrally geared sCO2 compander, a discussion of the mechanical and aerodynamic design of the compressor that is a two stage radial compressor operating subcritically at 27,512 rpm, and will then proceed to describe the test facility and measured data to characterize the performance and robustness of the machine. The paper will conclude with a discussion on lessons learned throughout the course of commissioning and testing. Practical aspects of testing a compressor operating near the dome including complications relating to obtaining an accurate compressor flow map, efficiency calculations, flow unsteadiness, and associated measurement uncertainties will be discussed.
Developing & Testing Components For More Reliable Linear Reciprocating Compression Of Hydrogen
(Turbomachinery Laboratory, Texas A&M Engineering Experiment Station, 2022) Broerman, Eugene L.; Shade, W. Norman; Poerner, Nathan; Cockerill, Sam; Miller, Michael A.
Southwest Research InstituteÂ® (SwRIÂ®), ACI Services, Inc. (ACI), and Libertine FPE Limited collaborated to design and build a Linear Motor Reciprocating Compressor (LMRC) via a DOE-funded project with ACI cost share. The advanced compression system utilizes a novel concept of driving a permanent magnet piston assembly inside a hermetically sealed compressor cylinder through electromagnetic windings. The LMRC design minimizes the mechanical part count and has no process gas leakage to atmosphere. The LMRC has no â€œrod,â€� rod packing, crankshaft, coupling, or separate motor/driver. In addition, the LMRC is able to improve the efficiency of the compression process by eliminating bearing losses and optimizing the piston speed profile to reduce fluid dynamic losses. The primary project objective was to meet the DOE goal of increasing the compression efficiency and reducing the cost of forecourt hydrogen compression; however, most of the associated technology developments can be applied to high-pressure natural gas, process gas, air, and other compressors. High pressures, electromagnetic fields, and a hydrogen environment (for the specific DOE vehicle refueling application) are the main design obstacles that had to be overcome to design a linear motor reciprocating compressor that can ultimately achieve a 12,700-psi final discharge pressure in the third stage. Manufacturing of the first stage LMRC (first of three stages) was completed and tested in early-to-mid 2020. Solid model images and a photo of the LMRC that was built and tested is presented in Figure 1. The first stage LMRC has design suction and discharge pressures of 290 and 1,035 psi, respectively. After a failure caused the testing to end prematurely, SwRI internal research and development (IR&D) funding was sought to rebuild the LMRC using the lessons-learned from the 2020 testing to improve some of the key components of the design. The key components that were the focus of the IR&D project are as follows: â€¢ Metal Coatings â€“ Specifically, coatings for magnets. A new coating and process method was developed to protect magnets from hydrogen incursion. â€¢ Valve Design â€“ Based on the identified design improvements, a new valve design with minimal leakage for hydrogen service was developed and built. â€¢ Motion Profile â€“ Motion profile optimization efforts were performed with the rebuilt LMRC. Testing of the above-noted components of the LMRC was completed in early-to-mid 2022; therefore, test data is included in this lecture. In addition to those component developments, further advances in the hermetic actuator platform technology are expected to yield efficiency and durability benefits for subsequent phases of development ahead of commercial product launch. The paper will include discussions of design, manufacturing, and testing aspects of some of the individual components and of the entire LMRC. In addition to being highly relevant to the hydrogen gas economy, the LMRC is considered relevant and applicable to most gas compression industries.

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