Compressor Characteristics Research Articles

A Study of Loss Model Parameter Sensitivity in Compressor Unsteady Flow Simulations

Abstract This article presents results from a comprehensive sensitivity analysis focused on loss models used in a recently developed compressor unsteady mean line flow model for a transonic axial-centrifugal compressor. The mean line flow model treats flow through rotors and stators in their respective reference frames (rotating or stationary), and the compressor performance is determined by the kinetic energy addition and various physics-based loss models in relative frames. In this paper, we describe the modeling approach of the compressor flow model, as well as the loss models that are used to obtain a relatively good match against test data. Sensitivity studies of selected loss model parameters are presented to show the effect of individual loss model parameters on the overall compressor characteristics in the entire speed range. The effects of losses on unsteady flow transients are assessed by comparing the transient responses when a step reduction of throttle area is applied. The comparisons show that the change in loss magnitude has weak effects on transient response if the change of loss does not significantly change the system stability.

A novel optimization framework for natural gas transportation pipeline networks based on deep reinforcement learning

Natural gas is an emerging and reliable energy source in transition to a low-carbon economy. The natural gas transportation pipeline network systems are crucial when transporting natural gas from the production endpoints to processing or consuming endpoints. Optimizing the operational efficiency of compressor stations within pipeline networks is an effective way to reduce energy consumption and carbon emissions during transportation. This paper proposes an optimization framework for natural gas transportation pipeline networks based on deep reinforcement learning (DRL). The mathematical simulation model is derived from mass balance, hydrodynamics principles of gas flow, and compressor characteristics. The optimization control problem in steady state is formulated into a one-step Markov decision process (MDP) and solved by DRL. The decision variables are selected as the discharge ratio of each compressor. By the comprehensive comparison with dynamic programming (DP) and genetic algorithm (GA) in three typical element topologies (a linear topology with gun-barrel structure, a linear topology with branch structure, and a tree topology), the proposed method can obtain 4.60% lower power consumption than GA, and the time consumption is reduced by 97.5% compared with DP. The proposed framework could be further utilized for future large-scale network optimization practices.

Research on intelligent control system of dynamic magnetic tubular linear compressor

Abstract Addressing the cooling power control issue of linear compressors, a PID controller based on a cubic spline improved grey wolf optimization (tri-GWO) algorithm was designed. The mechanical and electromagnetic characteristics of the linear compressor were used to construct the cooling power transfer function of the linear compressor. The effects of different control algorithms on the cooling power of the linear compressor were studied in Simulink, and the response speed, settling time, and robustness of different algorithms were compared based on the simulation results. Further analysis was conducted on the impact of different algorithms in PID control. The results show that in terms of stability and robustness, the tri-GWO-PID controller has an overshoot close to 0 and quickly stabilizes at the target cooling power; in terms of tracking, the tri-GWO-PID controller exhibits the best tracking performance with the smallest cooling power deviation. The research results provide a reference for the study of cooling power control of linear compressors.

Experimental and numerical analysis of mechanics and fracture characteristics of engine compressor

Abstract Investigating the fatigue failure behavior of compressor fan blades and their materials in aero-engines is a crucial research area. This paper focuses on the compressor fan blades and their constituent materials of aero-engines. Firstly, fluid-structure interaction (FSI) numerical simulations under various rotational speeds are conducted to determine the stress distribution and identify the maximum stress. Secondly, based on the FSI results, fatigue tests on fan blade materials under different stress amplitudes are performed to explore the relationship between load and life, so as to analyze the fracture characteristics under various stress amplitudes. This research has significant implications for ensuring the stable operation of aero-engine fan blades.

OPTIMIZATION SYSTEM FOR LOCAL CONTROL OF COMPRESSOR STATION

The article was devoted to the characteristics of using a compressor to process gas deposits. It is an important principle that the liquid is lifted to the surface of the earth by the energy of the gas compressed from the layer during processing. The structure of the well, the diameter of the exploitation belt, and the fountain pipes should be determined in such a way that there is little pressure in the well and in the trunk. Fountain pipes should not be lowered from the barrier to reducing pressure in the well's trunk and saving metal consumption. Depending on the daily gas volume of oil deposits, the gradient of pressure in the bed and the duration of the gas-water border should have been known. The change in those parameters depends primarily on the energy of the bed. The exploitation of the oil bed can lead to gas and flooding. The gas tank is the force that enables the liquid to move. In the compressor regime, however, the main energy is the energy of six gases. The compressor lifts the liquid to the surface of the earth, mainly because of air or gas. Keywords: gas compressor, field operation compress, compressor characteristics, formation water, wellbore pressure.

Thermodynamic performance and compression characteristics analysis of low GWP refrigerant in compressors: Experimental investigation and 0-D/3-D simulation

The utilization of low global warming potential (GWP) refrigerants is crucial for reducing greenhouse gas emissions. Among these alternatives for hydrofluorocarbons (HFCs), R290 stands out as a natural refrigerant with a low GWP value of 3. Therefore, it is beneficial to promote its widespread adoption and enhance the efficiency of compressors and their systems that utilize R290 to mitigate the greenhouse effect. The present study investigates and compares the thermodynamic performance and compression characteristics of a high-speed compressor employing R290 as a refrigerant with those of an R32 compressor. In contrast to previous studies, this paper presents a novel approach by developing validated the zero-dimensional (0-D) and three-dimensional (3-D) simulation model, along with experiments, to investigate the distribution of performance loss and suction-compression characteristics in high-speed R290 compressors. The results demonstrate that the R290 compressor exhibits superior volumetric efficiency, while excessive compression at high speeds leads to a noticeable reduction in indicated power. The combination of increased over-compression loss and motor loss at high speeds resulted in a 11.7% rise in input power, leading to an 8.4% decline in thermodynamic performance for the R290 compressor under standard heating compared to the R32 compressor.

Unsteady flow and thermal dynamic performance of pre-compression characteristics in variable-speed scroll compressors

In the suction process of scroll compressors, a special thermodynamic phenomenon occurs, known as pre-compression, which significantly affects the inhalation capacity, volumetric efficiency, and thermal characteristics of scroll compressors. To explore its generation and impact, unsteady flow field distributions of the pre-compression phenomenon were obtained by numerical simulations. The pressure variation of the pre-compression phenomenon in air was analyzed, and the power consumption caused by pre-compression during the working process was investigated. Study results indicated that the pre-compression phenomenon is mainly produced by the geometric structure and operating features of the scroll compressor. The initial angle of the pre-compression phenomenon decreases by 31° as the rotational speed ranges from 3000 to 7000 r/min. The generation of the pre-compression phenomenon induces eddies in the suction chamber. Additionally, it was demonstrated that during the suction process, mass flow rate increases owing to the pre-compression phenomenon. The study is helpful for analyzing the suction process and improving operating efficiency of scroll compressors.

Виявлення впливу шорсткості та радіального зазору на характеристику осьового багатоступеневого компресора

The operation of gas turbine engines inevitably increases the blade roughness and tip clearance in multistage axial compressors. The result is an increase in its thermogasodynamic parameters. The reason for the increase in the roughness of the blades and the tip clearance can be various factors: clogging of the flow part of the compressor (adhesion and deposition of dust on the surface of the blades), erosion due to the arrival of hard sand grains in the flow part, etc. The subject of this study is thermogasodynamic processes in the flow part of a multistage axial compressor, based on the presence of flow part removal. The goal is to develop a methodology for forecasting and researching the influence of the blade surface roughness and increased tip clearance on the overall characteristics of a multistage axial compressor. A twelve-stage axial compressor was used as the research object. The guiding vanes of the first four stages and the inlet guiding vanes depend on the rotation frequency. As a result, it was not possible to investigate the influence of the surface roughness of the blades and the increased tip clearance on the overall characteristics of the multistage axial compressor. The calculation of the characteristics of an axial multistage compressor with simulation of different levels of roughness and increased tip clearance in comparison with its initial values and obtained several indicators of changes in thermogasodynamic parameters and characteristics of the compressor with changes in roughness (ks = 3 μm, ks = 20 μm, ks = 40 μm) was performed. and tip clearance (Δr=1%, Δr=2%, Δr=5%). The scientific and practical novelty of the obtained results arises from the following: the method of calculating the thermogasdynamic parameters and characteristics of an axial multistage compressor has been improved, which makes it possible to evaluate the effect of the roughness of the surfaces of the blades and the increased tip clearance; new data were obtained regarding the change in the compressor characteristics at different levels of roughness and the size of the tip clearance.

Application of a Novel Weighted Essentially Non-Oscillatory Scheme for Reynolds-Averaged Stress Model and Reynolds-Averaged Stress Model/Large Eddy Simulation (RANS/LES) Coupled Simulations in Turbomachinery Flows

In numerical simulations, achieving high accuracy without significantly increasing computational cost is often a challenge. To address this issue, this paper proposes an improved finite volume Weighted Essentially Non-Oscillatory (WENO) scheme for structured grids. By employing a single-point quadrature rule to perform flux integration on the control volume faces, this scheme is designed for use in NUAA-Turbo three-dimensional fluid solvers based on structured grids, utilizing RANS and RANS/LES coupling to simulate turbomachinery flows. Firstly, the new WENO scheme is validated against classical numerical test cases to evaluate its stability and reliability in handling discontinuities, double Mach reflection problems, and Rayleigh–Taylor (RT) instability. Compared to the original scheme, this improved finite-volume WENO scheme demonstrates better stability near discontinuities and more effectively resolves flow features at the same grid resolution. Next, for engineering applications related to turbomachinery, such as compressor and turbine characteristics, calculations using RANS are performed and the results obtained with WENO-ZQ3 and WENO-JS3 are compared. Finally, the new fifth-order WENO scheme is applied to RANS/LES coupling simulations of turbine wake and film cooling. The results indicate that the improved finite-volume WENO scheme provides better stability and accuracy in engineering applications. For instance, the average error in calculating compressor efficiency characteristics is reduced from 0.76% to 0.05%, the error in turbine vane pressure distribution compared to the experimental values is within 1%, and the error in film cooling efficiency centerline distribution compared to the experimental values is within 3%. Additionally, the qualitative results of turbine wake and film cooling show that even with a small number of grid points, more detailed flow physics can be captured, thereby reducing computational costs in aerodynamic applications.

Nearly isothermal compression characteristics of the helium oil-flooded scroll compressor

The helium compressor is a crucial component in cryocooler refrigeration systems. Oil-flooding is a promising technique to solve the cooling and leakage challenges in helium scroll compressors, facilitating nearly isothermal compression. In this paper, the validated numerical model is employed to investigate the nearly isothermal compression characteristics of the two-phase mixture of helium and oil in a scroll compressor. Results indicate that the discharge temperature can be remarkably lowered from 455 °C to approximately 64 °C with the injection of an appropriate amount of oil into the working chamber. Moreover, the sealing effect of oil enhances the volumetric efficiency from approximately 66 % to 93.6 %. These advantages of oil flooding ensure an internal indicated efficiency that exceeds 100 % and results in superior isothermal efficiency. However, the polytropic exponent during the nearly isothermal compression process is smaller than the theoretical value, which imposes higher requirements on the built-in volume ratio for the helium oil-flooded scroll compressor.

Experimental study on the blade tip clearance sensitive effect in compressors with different loading levels

Rotor tip clearance has significant influences on both the performances and internal flow fields of compressors. To explore the relationship between these influences and compressor loading levels, four single-stage compressors, with loading levels ranging from 0.36 to 0.59, have been designed for experiments. Compressor characteristics and flow fields at blade row inlet and outlet planes were measured under two rotor tip clearance conditions: 1% and 2.2% blade height. Based on these experimental results, an analysis was conducted to examine the influence of loading levels on the sensitivity to rotor tip clearance. The experimental results indicate that increase in the loading level enhances the sensitivity of compressor stage characteristics to rotor tip clearance. At the design point, an increase of 1% in the rotor tip clearance causes reductions of 1.3% in the stage efficiency and 2.3% in the stage static pressure rise when the loading level is 0.36. However, when the loading level is 0.59, the reductions are 2.9% and 3.4% in stage efficiency and stage static pressure rise, respectively. Increasing the rotor tip clearance brings the static pressure rise at the rotor tip region closer to its limit, resulting in a rapid growth of local loss. This trend becomes increasingly pronounced with higher compressor loading level.

Experimental study on performance and compressor characteristics of transcritical CO2 heat pump system

The accelerated advancement of the economy has led to a heightened focus on the issue of energy conservation and reduced consumption within heat pump systems. An experimental investigation was conducted to analyze the impact of discharge pressure and outlet water temperature on the performance of the transcritical CO2 single-stage heat pump system and vapor injection heat pump system. The experimental results show that the heating capacity first increases and then tends to be constant or even slightly decreases with the increase of discharge pressure in single-stage heat pump system. When subjected to the same operating conditions, the coefficient of performance of vapor injection heat pump system exceeds that of single-stage heat pump system. Compared with single-stage heat pump system, the performance coefficient of vapor injection heat pump system has increased by an average of 6.21% and the heating capacity has increased by an average of 9.54%. Additionally, the volumetric efficiency of the compressor substantially decreases when producing high-temperature hot water. Semi-empirical models for evaluating the compressor performance in both single-stage heat pump system and vapor injection pump system are established through the parameterization of the volumetric efficiency with respect to the pressure ratio and compressor speed. These models effectively forecast compressor performance.

Research and Application of Diesel Engine Turbocharging Technology in Plateau Environment

This article summarizes the changes and correction methods of turbocharger compressor characteristics in plateau environments, providing a basis for the plateau matching of diesel engines and turbochargers. Analyze the current research status of plateau matching between fixed cross-section turbochargers, variable cross-section turbochargers, and two-stage turbocharging systems and diesel engines, and explore the potential of variable cross-section turbocharging (VGT), ordinary two-stage turbocharging (TST), and adjustable two-stage turbocharging (RTST) for diesel engine plateau power improvement. Through comparative analysis, the two-stage adjustable turbocharging system based on VGT combines the advantages of two-stage turbocharging and VGT technology, and has the characteristics of high pressure ratio and wide flow rate, which can significantly improve the comprehensive performance of diesel engines on high altitudes.

Erratum to “Characteristics of the axial compressor with different stator gaps in compressed air energy storage system”

Erratum to “Characteristics of the axial compressor with different stator gaps in compressed air energy storage system”

Study on pressurization characteristics of single-screw steam compressor with water spray cooling under fluctuating heat source operating conditions

For a water-injected single-screw steam compressor (SSSC), the performance of the compressor is significantly affected by the water spray rate. However, the precise relationship between the water injection parameters and the operating parameters of the heat source under fluctuating heat source operating conditions (FHSOC) has not been elucidated. This paper introduces a constructed thermodynamic analysis model for the wet compression process under FHSOC aiming to explore the impact of fluctuating heat source parameters such as inlet steam temperature (IST) and inlet steam dryness (ISD) on the thermodynamic performance parameters of the compressor. The operational performance of the SSSC is then analyzed and compared under two distinct conditions: optimal water spray rate (OWSR) and fixed water spray rate (FWSR). The results demonstrate that when the IST of the SSSC increases within the range of 375 K–400 K, there is an initial decline followed by an increase in both the leakage rate and volumetric efficiency. Simultaneously, displacement and power consumption decrease, while adiabatic indicated efficiency and OWSR increase. Within this range, an optimal synergy is observed between IST and water spray parameters enabling the compressor to exhibit superior lubrication, sealing, and pressurization performance. On the other hand, when the ISD increases within the range of 0.92–1, the total heat transfer in the compression chamber decreases, and the leakage, OWSR, displacement, power consumption, adiabatic indicated efficiency, and volumetric efficiency all show varying degrees of increase. Regarding the volumetric efficiency corresponding to the OWSR, the impact of ISD on volumetric efficiency surpasses that of IST to a significant degree.

Performance of a supercritical carbon dioxide compressor using a streamline curvature based throughflow method

Supercritical carbon dioxide (sCO2) has emerged as a promising working fluid for the Brayton power cycle, offering enhanced efficiency due to its high density and low viscosity near the critical point. A critical component of the sCO2 Brayton cycle is the turbomachinery, namely the compressor. The pronounced sensitivity of the thermophysical properties of sCO2 in the vicinity of the critical point where the compressor operates can significantly impact the performance characteristics of sCO2 compressors. This study presents a two-dimensional (2D) streamline curvature-based throughflow method, considering real gas thermophysical properties, to analyze a centrifugal compressor operating with sCO2 at near-critical inlet conditions. The method’s validity is established through comparisons of the predicted performance characteristics with those of the Sandia National Laboratories compressor and by comparing the predicted flow field with the pitch-averaged flow field obtained from computational fluid dynamic (CFD) analysis. Moreover, various compressor intake conditions including subcritical vapor, supercritical vapor, supercritical liquid, and near-critical conditions are investigated to explore their impact on compressor performance. The streamline curvature-based throughflow method demonstrates its effectiveness by achieving significant agreement between the flow field and performance characteristics, both at design and off-design conditions where efficiency predictions were within 5.84% near the best efficiency point compared to CFD simulations. At near critical conditions, a maximum of 3201% increase the computational run-time required for CFD based computation was observed compared to superheated conditions while only a maximum of 164% increase in run-time was observed in the throughflow based computations as a result of the numerical under-relaxation required.

Research on the influence of initial parameters of water droplets on the performance of counter-rotating axial-flow compressor

This paper employs a numerical simulation method to investigate the wet compression working characteristics of a counter-rotating axial-flow compressor (CRAC) in an air-inlet, water-containing environment under different water droplet parameters at a designed rotational speed. The influence of initial water droplet parameters on the overall performance of the CRAC and the variations in the flow field characteristics under different wet compression conditions was investigated. The initial diameter of water droplets exhibited the most significant impact on the wet compression effect. Under an appropriate inlet water content, water droplets with smaller diameters effectively reduced the temperature of the CRAC’s internal flow field, increasing the air density. Consequently, the axial velocity decreased, altering the velocity triangle and increasing the rotor working capacity, which enhanced the performance of the CRAC. Additionally, wet compression influenced the flow field of the rear rotor stronger than that of the front rotor. When the initial diameter of water droplets is too large, the evaporative cooling effect cannot be fully exploited so wet compression only slightly improved the compressor performance. These findings may help understand the working characteristics of the CRAC in water-containing environments better, offering guidance for CRAC design using wet compression technology.

Numerical investigation on the flow resistance characteristics of balance block in the rotary compressor

With the increasing demand for energy saving, the air conditioner with variable frequency becomes the mainstream of the market, which leads to a high requirement for the dynamic balance characteristics of the rotary compressor at variable speed conditions. The balance block is the key part in the eccentric shaft system to balance the rotational inertia force brought by the eccentric wheel, and its flow resistance during rotating process has a large impact on the power consumption. In this paper, CFD simulations will be carried out to study the flow characteristics of several different compressor balance blocks and the results can provide reference for the optimization design of the balance block in the rotary compressor.

Analysis of methods for modeling operating modes of compressor equipment that ensures the operation of field low-temperature separation units

Objective. A booster compressor station (BCS) is one of the key technological facilities necessary to ensure the effective operation of low-temperature separation technology for natural gas in field gas preparation systems for transportation. Ensuring promising operating modes of booster compressor stations with high efficiency is an urgent task. Method. One of the tools for solving this problem is mathematical modeling of the operating modes of centrifugal compressors (hereinafter - CPC), which are part of gas pumping units (GPU). The basis of the mathematical model is the gas dynamic characteristic (GDC) of the pulp and paper mill. The existing regulatory documentation presents simplified methods for modeling HDC, which are suitable for low-pressure pulp and paper mills with a pressure ratio of up to 1.5 and the number of compression stages of no more than three, but are not suitable for multi-stage high-pressure pulp and paper mills. Result. The results of a comparison of three methods of modeling the hydrodynamic characteristics (method of reduced characteristics, refined method of reduced characteristics, method of two-parameter approximation) of high-pressure pulp and paper mills are presented using the example of a pulp and paper mill with a pressure ratio of up to 2.0, intended for equipping a gas pumping unit as part of field booster compressor stations. An analysis and comparison of the obtained modeling results with actual data was carried out. Conclusion. When using the UMPH-2D modeling method, the smallest errors were obtained (no more than 2.0%), which, in turn, indicates its highest accuracy among the considered methods for recalculating the gas flow characteristics of high-pressure and multi-stage compressors.

Characteristics of the axial compressor with different stator gaps in compressed air energy storage system

The axial compressor in compressed air energy storage (CAES) system needs to operate stably and efficiently within a wide working range. The stator gap plays a critical role in suppressing corner separation and enhancing blade throughflow. The primary objective of this study is to determine the optimal combination of stator gaps to further expand the stable working range of the compressor while ensuring high efficiency. In this study, the flow characteristics of different stator gaps of the five-stage axial compressor in a specific CAES system are researched numerically. Firstly, the impact of different stator gaps on the aerodynamic performance is analyzed. The stator gap effectively broadens the stable working range of the compressor, with the hub gap exhibiting greater potential for expansion compared to the shroud gap. Subsequently, a comparative analysis is conducted on the internal flow of the third stage stator under near-stall conditions. Different gap leakage forms different vortex structures, and the gap leakage can effectively eliminate the accumulation of low-energy fluid in the corner area, optimize the limit streamlines on the blade suction surface and the temperature distribution. The low-velocity area caused by different stator gaps is also different. Finally, energy loss and energy dissipation with different stator gaps are explored. The gap leakage flow results in high energy loss, and different stator gaps exhibit notable differences in distribution of the high energy loss regions. Different types of stator gaps exhibit consistent high energy dissipation areas, which include the leading-edge stagnation area, boundary layer area on blade surface, and wake area. It is important to note that the high energy loss area does not necessarily coincide with the high energy dissipation area. The combined application of two loss evaluation methods contributes to a more comprehensive investigation of the loss distribution characteristics of the compressor.