Reciprocating Piston Compressor Research Articles

Characterization of PPS Piston and Packing Ring Materials for High-Pressure Hydrogen Applications.

The widespread adoption of renewable energy hinges on the efficient transportation of hydrogen. Reciprocating piston compressor technology in non-lubricated operation will play a key role, ensuring high flow rates and compression ratios. These systems rely on advanced high-strength sealing solutions for piston and rod packing rings utilizing advanced fiber-reinforced polymers. Polyphenylene sulfide (PPS) polymer matrix composites have seen use in tribological applications and promise high mechanical strength and wear resistance. The presented work describes carbon and glass fiber-reinforced PPS matrix polymers in comparison, which are characterized by complementary methods to investigate their properties and potential for application in reciprocating compressor under non-lubricated operation. Thermo-mechanical and tribological testing was supported by microstructure analysis utilizing advanced X-ray and electron imaging techniques. New insights in micromechanical deformation behavior in regard to fiber materials, interface strength and orientation in fiber-reinforced polymers are given. Conclusions on the suitability of different PPS matrix composites for high-pressure hydrogen compression applications were obtained.

High-Strength PPS-Polymer Composites for Hydrogen High-Pressure Applications

Hydrogen technology can be one key for a transition to sustainable energy necessary to achieve climate targets and limit global warming to 1.5 °C since the beginning of the industrial revolution. Hydrogen as a CO2 neutral energy carrier must replace fossil fuels from the existing natural gas grid and infrastructure to enable an environmentally friendly and circular economy in future societies. Batteries and e-fuels are practicable technologies for short term and quantitatively limited energy provision, with disadvantages including raw material demands and technologically complex transformation cycles. Utilizing advanced power-to-gas concepts, hydrogen will not only be most efficient technology in energy storage, but also allows adaption and reuse of existing energy transportation infrastructure.To provide volatile hydrogen gas in the required flow and energy densities, advanced compression technology needs to be developed inspired by conventional gas compression systems. Reciprocating piston compressors are developed for high-pressure hydrogen applications, providing high pressure levels and flow rates. Compression equipment must be designed for non-lubricated dry-running conditions, as high gas purity standards of hydrogen do not allow for oil-based lubricants to be introduced into the process gas. High-strength carbon fiber reinforced composites are developed as piston and packing ring materials to withstand extreme pressure differences under harsh thermo-mechanically loaded operation conditions.Promising candidates with high strength and wear resistance in the form of PPS-polymers, are developed with PTFE solid lubricants and different carbon fiber fractions to combine high strength, with low friction and wear, improve pressure operation range, and limit down times of hydrogen piston compressors. The current work describes tribological testing of advanced PPS-polymers with 10 to 30 wt.% carbon fibers in a high-velocity tribometer under hydrogen gas atmosphere. Supporting thermo-mechanical tests give new insights in deformation mechanisms of fiber reinforced polymer composites and allow conclusions on their applicability for hydrogen compression.

Thermo-mechanical properties and internal architecture of PI composites for high-pressure hydrogen applications

The efficient transport of Hydrogen is pivotal to the wide scale adaption of energy produced from renewable sources. Reciprocating piston compressors with high strength non-lubricated sealing solutions for piston and rod packing rings will be a key technology to fulfill gas purity and high-pressure gradients demands set by hydrogen applications. Polyimide polymer matrix composites have seen use in tribological applications and promise high mechanical strength and temperature resistance. The presented work describes carbon fiber reinforced Polyimide blends in comparison, characterized by complementary advanced methods to investigate their properties and potential for reciprocating compressor applications. Thermo-mechanical and tribological testing was supported by microstructure analysis utilizing synchrotron tomography and electron microscopy, pinpointing the necessity of dry lubricating additives such as PTFE. New insights in micromechanical deformation behavior of fiber reinforced polymers are given and promising fiber-reinforced polyimide compositions suitable for high-pressure hydrogen compression applications were identified.

Compressor and Valve Control Performance Implications on Active Flow Control Aircraft

This study presents the feasibility of implementing commercial-off-the-shelf reciprocating piston compressors for a developed active flow control (AFC) actuation framework to quantify the aerospace relevant performance ramifications of control architecture and compressor operational choices. Three architectures are studied: supply valve metering, exit area metering, and a combined approach. All concepts are studied under varying compressor operation schedules. The analysis framework in this study integrates internal pneumatic actuation and discharge dynamics, an experimentally calibrated compressor pressure and thermal dynamics model, three feedback control architectures, and flight dynamics models. The framework is implemented in simulation to provide a user-friendly tool for linking AFC architecture choices to achievable flight trajectories. Actuator performance is evaluated using actuation time, output, compressor duty cycle, and specific energy consumption. Aircraft tracking performance is evaluated as usable time and slalom centerline deviation. The analysis indicates that a supply-volume-based metering approach is comparatively inefficient concerning an exit-area-based metering, resulting in high flight tracking error. Exit area metering provides the best efficiency and run time with some structural drawbacks, while the combined approach provides the best flight tracking performance at the expense of additional complexity. These results inform the choice of onboard AFC hardware choices.

A Topology Optimization Design of Compressor Connecting Rod

To address the problems of unstable and noisy compressor operation caused by excessive mass of the connecting rod of reciprocating piston compressor, a multi-objective topology optimization algorithm based on the compromise planning method is used to optimize the design of the connecting rod by considering both dynamic low-order inherent frequency and stiffness, and a multi-objective function of joint stiffness and inherent frequency is proposed. The finite element model is established and the optimized model is revalidated. The analysis results show that the optimized connecting rod mass is reduced by 21.6%, the low-order inherent frequency is improved, and the material meets the requirements of strength and stiffness.

Comprehensive multi-scale cylinder lubrication model for reciprocating piston compressors: From rigid-body dynamics to lubricant-flow simulation

A new comprehensive cylinder lubrication model for reciprocating piston compressors is presented. The focus lies on deriving the oil transport along the piston assembly to obtain compressor specific, optimal lube strategies without neglecting any main driver for oil consumption. The model accounts for the mutual interactions between the oil film, the compressed gas, the piston- and rider rings, the piston motion, the bending of the piston rod, and the crosshead motion. The presented model deals with the dynamical behavior of the entire drive including the secondary piston movements. A starving number St is introduced to study the tribological conditions between rings and cylinder wall and to assess the impact of starved lubrication.

Analysis and Development of a Small-Scale Supercritical Carbon Dioxide (sCO2) Brayton Cycle

Carbon dioxide’s (CO2) ability to reach the supercritical phase (7.39 MPa and 304.15 K) with low thermal energy input is an advantageous feature in power generation design, allowing for the use of various heat sources in the cycle. A small-scale supercritical carbon dioxide (sCO2) power cycle operating on the principle of a closed-loop Brayton cycle is currently under construction at The University of Texas at San Antonio, to design and develop a small-scale indirect-fired sCO2 Brayton cycle, acquire validation data of the cycle’s performance, and compare the cycle’s performance to other cycles operating in similar conditions. The power cycle consists of four principal components: A reciprocating piston compressor, a heating source, a reciprocating piston expander to produce power, and a heat exchanger to dissipate excess heat. The work explained in the present manuscript describes the theory and analysis conducted to design the piston expander, heating source, and heat exchanger in the cycle. Theoretical calculations indicate that using sCO2 for the Brayton cycle generates 4.5 kW of power with the inlet pressure and temperature of 17.23 MPa and 358.15 K to the piston expander. Based on the fully isentropic conditions, the thermal efficiency of the system is estimated to be 12.75%.

Preliminary Investigations of an Opposed Rotary Piston Compressor for the Air Feeding of a Polymer Electrolyte Membrane Fuel Cell System

Automotive polymer electrolyte membrane fuel cell systems are attracting much attention, driven by the requirements of low automotive exhaust emissions and energy consumption. A polymer electrolyte membrane fuel cell system provides opportunities for the developments in different types of air compressors. This paper proposed an opposed rotary piston compressor, which had the merits of more compact structures, less movement components, and a high pressure ratio, meeting the requirements of polymer electrolyte membrane fuel cell systems. Preliminary performance evaluations of the opposed rotary piston compressor were conducted under various scenarios. This will make a foundation for optimizations of outlet pipe layouts of the compressor. A three-dimensional numerical simulation approach was used; further, in-cylinder pressure evolutions, fluid mass flow rates, and P–V diagrams were analyzed. It indicated that the cyclic period of the opposed rotary piston compressor was half of reciprocating piston compressors. The specific mass flow rate of the compressor is in the range of 0.094–0.113 kg·(s·L)−1 for the given scenarios. Outlet ports 1 and 2 dominated the mass flow in the discharge process under scenarios 1, 3, and 4. In-cylinder pressure profiles show multipeaks for all of these scenarios. In-cylinder pressure increased rapidly in the compression process and part of the discharge process, which led to high energy consumption and low adiabatic efficiency. The maximum adiabatic efficiency is approximately 43.96% among the given scenarios.

On the value of liquid-air and pumped-thermal electricity storage systems in low-carbon electricity systems

We consider two medium-to-large scale thermomechanical electricity storage technologies currently under development, namely ‘Liquid-Air Energy Storage’ (LAES) and ‘Pumped-Thermal Electricity Storage’ (PTES). Consistent thermodynamic models and costing methods based on a unified methodology for the two systems from previous work are presented and used with the objective of integrating the characteristics of the technologies into a whole-electricity system assessment model and assessing their system-level value in various scenarios for system decarbonization. It is found that the value of storage depends on the cumulative installed capacity of storage in the system, with storage technologies providing greater marginal benefits at low penetrations. Two carbon target scenarios showed similar results, with a positive effect of more ambitious carbon targets on the system value of storage. The location and installed capacity of storage plants is found to have a significant impact on the system value and acceptable costs of both technologies. The system value of PTES was found to be slightly higher than that of LAES, driven by a higher storage duration and efficiency, although these results must be seen in light of the uncertainty in the (as yet, not demonstrated) performance of key PTES components, namely the reciprocating-piston compressors and expanders. At the same time, PTES was also found to have a higher power capital cost, which makes its deployment less economically attractive for implementation at lower volumes. The results indicate that the complexity of the decarbonization challenge makes it difficult to identify clearly a ‘best’ technology and suggest that the uptake of either technology can provide significant system-level benefits.

Simulation and Experimental Investigation of Labyrinth Seals for Reciprocating Piston Compressors

AbstractTo optimize the performance of oil‐free reciprocating piston compressors, the leakage flow through the piston seal has to be minimized. Therefore, the effects of the geometrical parameters and shapes of labyrinth seals on the leakage flow are examined. The main geometrical parameters and shapes are investigated by means of computational flow dynamics simulations. The optimum geometries obtained from the simulations are experimentally tested on a compressor rig. The rectangle labyrinth shows the lowest leakage followed by a novel semicircle geometry and the triangle geometry shows the highest leakage flow among the labyrinths. The straight seal exhibits the highest leakage flow rate. It can be concluded that the rectangle labyrinth reduces the leakage flow rate in the most efficient way.

Energy conversion characteristics of reciprocating piston quasi-isothermal compression systems using water sprays

Air compressors are vital and have numerous industrial applications. Approximately 8% of the annual operating electricity consumption in industrial countries is constituted by due to the use of air compressors. Because the poor heat transfer to the environment in the rapid compression process, the compression is non-isothermal, the efficiency of compressors is restricted. To improve their efficiency and achieve isothermal compression, this study proposes energy conversion reciprocating piston quasi-isothermal compression using a water spray. First, a mathematical model of a reciprocating piston compressor with water sprays was established. Through experimental investigation and simulations, the mathematical model was validated. The energy conversion characteristics of the reciprocating piston compressor were then studied. To reduce compression power and enhance compression efficiency, it was first discovered that the critical parameters were the input pressure of the driving chamber, water spray mass, and compression volume ratio, which were then evaluated thoroughly. The higher the inlet pressure of the driving chamber, the faster the air compression velocity. Additionally, the compression efficiency was elevated as the water spray mass was gradually increased for a given compression volume ratio. When the compression volume ratio was increased from 2 to 3, the compression power increased from 172.7 J/stroke to 294.2 J/stroke and the compression efficiency was enhanced from 37.3% (adiabatic) to 80.6%. This research and its performance analysis can be referred to during the parameter design optimisation of reciprocating piston quasi-isothermal compression systems using water sprays.

Fully coupled fluid-structure interaction model of reed valves in a multi-cylinder reciprocating piston compressor

For years compressor researchers have tried to account for the fluid interaction effect of the working fluid on valve motion in displacement compressors. In recent years, the computing capacities and available CFD and FEA programs have allowed fully coupled interaction of fluids and moving structures to be modelled more comprehensively. This paper describes our experience and results from developing a model of a multi-cylinder reciprocating piston compressor with suction and discharge valve systems that are fully coupled with the pressure pulsation in the adjacent plenum. Valve dynamics are captured by the model that affects compressor performance. The results show that higher running speed causes more discharge valve delay on closing due to higher pressure pulsation in discharge plenum. The acoustic property of the discharge plenum as it relates to valve motion is studied by the developed cost-effective standalone model.

Transient Dynamic Analysis of Crankshaft Torsional Vibration for Reciprocating Piston Compressor

The crankshaft of 6M50 type reciprocating piston compressor frequently cracked because of torsional vibration. To perform full analysis of crankshaft vibration of the compressor and solve the cracking problems completely, the finite element analysis software is used, and dynamic simulation of crankshaft torsional vibration is developed and analyzed. Finite element modeling process of compressor crankshafts is discussed, and the results of modal analysis for different modification plans are compared. Transient dynamic analysis of the system is performed. The basic cracking reason for crankshafts with different major diameters is explained theoretically by comparison of calculated and practical results.

Fault Analysis on Crosshead Fracture of the Reciprocating Piston Compressor C102B

The C102B reciprocating piston compressor is an important equipment widely used in methanol production. Because of the complexity of exact dynamics analysis, the traditional and common way to find the reason of fracture is only based on metallographic structure analysis of crosshead material. In this paper, after metallographic structure analysis of crosshead material of the C102B compressor, the maximum loads on it are also calculated and two dangerous crosshead positions with maximum load are determined. Finally, stress analysis of the crosshead in two dangerous positions is implemented by FEM technology. Based on the above study, the reasons of crosshead fracture of the C102B compressor are found. The results has an inportant significance for judging the resaon of crosshead failure.

Preventive Suggestion and Fault Analysis on Piston Fracture of the Methanol Fresh Air Compressor C102B

The piston is a key moving-part of the reciprocating piston compressor with a high failure rate. Because of the difficult exact calculation of machinery dynamic, the traditional and common way to find the reason of fracture is based on metal-lographic phase of piston material. The C102B reciprocating piston compressor is an important equipment in methanol plant. In this paper, in connection with the piston fracture of the C102B fresh air compressor on service , besides a lot of analysis on metal-lographic phase, the 3-D model of piston and cylinder were built-up, and the two dangerous places where the piston suffered max-force were found. Bases on ANSYS and FEM technology, the value of max-force on piston at the two places were carried out. Finally, the reasons of piston fracture of the C102B fresh air compressor were found and some preventive suggestion was proposed.

Reciprocating-piston compressor having non-contact gap

Reciprocating-piston compressor having non-contact gap

Admission (Economizer) Port Optimization of a Voorhees Modified Reciprocating CO2 Compressor

Admission (the use of an economizer) is a well-known method to reduce the expansion losses of a refrigeration system. The alternative refrigerant carbon dioxide (CO2) has a relatively large isentropic exponent. Therefore, refrigeration systems using CO2 as a refrigerant have a high potential for raising efficiency by admission. Reciprocating piston compressors are favored for CO2 refrigeration applications due to the compression chamber's small sealing length and resulting low internal leakage rate. This paper presents a methodology to investigate the influence of the admission (economizer) port design of a reciprocating compressor on the admission process. The port's geometry—especially its cross-sectional area—has a large impact on the system efficiency at operation conditions and therefore needs to be optimized. For this purpose, an optimization process has been established. It is based on indicator diagram analysis. To exemplify, the measurements of three admission ports were compared at constant suction pressure (1.2 MPa relates to an evaporation temperature of −35°C) and varying admission pressures (1.4–2.6 MPa). Based on the results, the optimal port diameter for the targeted operation condition is obtained by interpolation.

A Parametric Analysis Microcomputer Model for Evaluating the Thermodynamic Performance of a Reciprocating Brayton Cycle Engine

A novel Brayton open-cycle engine is under development. It operates similarly to a gas turbine engine, but uses reciprocating piston compressor and expander components. The design appears to have a number of advantages, including multifuel capability, the potential for lower cost, and the ability to be scaled to small sizes without significant loss in efficiency. An interactive microcomputer model has been developed that analyzes the thermodynamic performance of the engine. The model incorporates all the important irreversibilities found in piston devices, including heat transfer, mechanical friction, pressure losses, and mass loss and recirculation. There are 38 input parameters to the model. Key independent operating parameters are maximum temperature, compressor rpm, and pressure ratio. While the development of the model and its assumptions are outlined in this paper, the emphasis is on model applications. The model has demonstrated itself to be a powerful tool for evaluating engine thermal efficiency, net specific work, and power. It can be used to analyze the performance of individual engine designs, to generate performance “maps” that graphically represent engine operating characteristics, and to perform sensitivity analysis to compare the relative effects of various input parameters. Examples of each of these model applications are discussed. Recommendations for model improvements and for further engine development work are made. The need for better experimental data to verify some critical model assumptions is stressed.

NAVY AIR COMPRESSORS — PAST, PRESENT AND FUTURE

ABSTRACTAs part of a program to improve shipboard air compressor reliability, the Naval Sea Systems Command (NAVSEA) and David Taylor Naval Ship Research and Development Center (DTNSRDC) are developing a new generation of rotary machines to replace ships service reciprocating piston air compressors with new, smaller, lighter, more reliable designs.The successful development of completely water flooded 125 psi air compressor units by DTNSRDC resulted in the award of a four phase contract by NAVSEA to a compressor manufacturer to design, build, and test low and high pressure shipboard prototypes.A review of the shipboard air compressor history which led to the current approach is presented along with details of the new compressor development philosophy, the low pressure design phase of the contract and the building and testing of the low pressure prototype. The results of a design analysis with respect to reliability and maintainability goals are also presented and compared to the current oil free reciprocating piston compressors.

Paper 8: Problems Associated with Modern Designs of Oil-Free Labyrinth Piston Compressors

This paper presents a survey of problems common to all reciprocating piston compressors for oil-free delivery of gas, and states typical problems associated with labyrinth piston compressors. The paper discusses special arrangements for placing guiding elements outside the process gas area; the development of a self-centring, contact-free piston; and design and material problems relating to a labyrinth piston-rod gland. The closed, pressurized crankcase designs make it possible to use contactless sealing techniques in refrigerating and many other process gas applications with oil-free delivery or recycling of gas. Mention is made of gas in the crankcase and associated problems, such as oil-gas dilution and inside-pressure in the frame. The paper also presents an efficiency comparison between contactless and ring-sealed piston compressors and briefly mentions the reliability of labyrinth pistons, giving statistics on the sequence of replacement.