Performance Of Scroll Compressor Research Articles

Numerical analysis of scroll compressor performance with pre-discharge valve for low-temperature heat pumps

Scroll compressors are a crucial component of automotive air conditioning systems. When operating at off-designed working conditions, over-compression can occur in the scroll compressor. A pre-discharge valve (PDV) is proposed to enhance the performance of the scroll compressor under off-design working conditions. The performance of the scroll compressor with a PDV for a low-temperature heat pump system is simulated. The results show that the scroll compressor with the PDV structure has lower pressure in the compression chambers and improved over-compression compared to conventional scroll compressors. The use of the PDV also leads to a reduction in the temperature of the refrigerant gas in the compression chambers and a decrease in the leakage between the compression chambers. As the evaporating temperature increases from −25 °C to −5 °C, the mass flow rate and volumetric efficiency increase, and the discharge temperature decreases. At an evaporating temperature of −5 °C, the discharge temperature at the center discharge port of the scroll compressor with the PDV is reduced by 2.4 °C compared to the conventional scroll compressor. The input power of the scroll compressor is reduced by 165.4 W–897.7 W. The volumetric efficiency and the isentropic efficiency are improved by 0.13 % and 6.63 % respectively.

Experimental Research on the Output Performance of Scroll Compressor for Micro Scale Compressed Air Energy Storage System

Micro compressed air energy storage systems are a research hotspot in the field of compressed air energy storage technology. Compressors and expanders are the core equipment for energy conversion, and their performance has a significant impact on the performance of the entire compressed air energy storage system. Scroll compressors have the advantages of small size, low noise, light weight, low vibration, long service life, continuous and stable gas transmission, and reliable operation. This article builds a micro compressed air energy storage system based on a scroll compressor and studies the effects of key parameters such as speed, torque, current, and storage tank pressure on the temperature difference, pressure ratio, energy consumption, and efficiency of the scroll compressor. The experimental results indicate that the power consumption of the scroll compressor shows an increasing trend with the increase in current, torque, and gas storage tank pressure. The isentropic efficiency of a scroll compressor shows a decreasing trend with increasing current, torque, and storage tank pressure. The maximum values of power consumption and isentropic efficiency of the scroll compressor are 3427 W and 90.8%, respectively.

A dynamic model for pin coupling anti-rotation mechanism of automotive scroll compressor

Pin coupling anti-rotation mechanism is adopted in mechanically driven automotive scroll compressor due to its simple structure and high reliability. However, the sidewall of anti-rotation hole in pin coupling anti-rotation mechanism is easy to be worn out, deteriorating the performance of scroll compressor. To figure out the cause and take measures, a dynamic model for pin coupling anti-rotation mechanism is developed in this paper. The dynamic model takes two important factors into consideration, offsetting scroll wraps and radial compliance mechanism. Using the dynamic model, the contact force between the anti-rotation pin and anti-rotation hole can be determined, thus the wear zone can be predicted during one rotation cycle. A simulation program adopting the above dynamic model is developed to predict the performance of automotive scroll compressor. The error between simulated shaft power of compressor and experimental result is no more than 4% for all test conditions. The wear zone predicted by the simulation program agrees well with the actual scroll compressor which survived a durability test.

Unsteady characteristic and flow mechanism of a scroll compressor in small-scale compressed air energy storage system

Tangential leakage loss reduction has significant impact on improving the performance of scroll compressors. In this study, the flow field of a scroll compressor working with air was numerically investigated. The characteristics of the tangential leakage flow in different radial clearances were studied, which was obtained by analyzing the field quantities distributions. Moreover, the influence of radial clearance on the time-averaged performance of the scroll compressor and the aerodynamic force on it in each direction are analyzed. The results showed that the gas flowed into the low-pressure chamber through the radial clearance, and the downstream gas in compression chamber was compressed and collides with the leakage flow, having aggravated the uneven distribution of the flow field in the compression chamber. The gas velocity was faster in the region with large pressure difference, and the peak velocity appeared near the radial clearance. Moreover, as the radial clearance continues to increase in a certain range, its influence on the working characteristic curve of scroll compressor has two sides. The research can provide theoretical basis for the structural design of scroll compressors.

Impact of micro-grooves in scroll wrap tips on the performance of a trans-critical CO2 scroll compressor

Radial leakage was commonly regarded as the primary factor restricting the aero-thermodynamic performance of scroll compressors. In this paper, a passive flow control approach of micro-grooves in scroll wrap tip for the radial leakage in the scroll compressor was proposed, and its flow characteristics were numerically investigated. The impact of micro-grooves geometric parameters, such as groove number, depth, and partitions, on the flow control effect of the radial leakage was discussed, which was obtained by analyzing the evolution of the flow field and its influence on the performance of the scroll compressor. Results showed that the adoption of micro-grooves in scroll wrap tip yielded a significant limitation on the radial leakage, and geometrical parameters of the micro-grooves directly affected the flow control performance. Increasing groove numbers and partitions decreased the radial leakage effectively, while the leakage decreased first and then increased with the increase of the groove depth. The energy dissipation induced by the continuous throttling effect, jet expansion, and vortex in the groove cavity was the main flow control mechanism. The quadruple-grooves with the groove width of 0.5 mm and the groove depth of 100 μm were adopted in this study eventually. The volumetric and isentropic efficiency of the scroll compressor raised up 2.1 and 1.0 percentage point compared to the original case, respectively. Through reasonable working conditions and micro-grooves geometry, the aero-thermodynamic performance of the oil-free scroll compressor could be improved effectively by the scroll wrap tip with micro-grooves.

Geometric design and analysis of scroll compressors with a novel circular involute modified wrap

The scroll geometry in the central region of the scroll wrap plays a crucial role in determining the working performance of scroll compressors. In order to improve the comprehensive performance of scroll wraps, in this study, a novel circular involute modified wrap was put forward, in which the central and peripheral wrap profiles were connected by a circular involute in the central regions, so that a pair of fully smooth and correct meshing scroll wraps were generated. A geometric model of the involute modified wrap were proposed, and then equations of the wrap profiles and relations between geometric parameters were derived. Effects of geometric parameters on the shape and performance of the involute modified wrap were discussed in detail. Furthermore, the compression ratio of the involute modified wrap was studied by numerical simulation, and the deformation of the involute modified wrap produced by temperature load and pressure load was calculated, compared with the conventional circular arc modified wrap under the same geometric shape of scroll compressors. Study results demonstrate that the proposed involute modified wrap may simultaneously improve the compression ratio and the strength of wrap head for scroll compressors; in addition, the involute modified wrap is good for design flexibility, and therefore is superior to the circular arc modified wrap.

Performance evaluation of low-GWP refrigerants in 1–100 ton scroll compressors

• Method to scale the scroll compressor for different cooling capacities and refrigerants. • Validation of scroll compressor model in PDSim. • Performance evaluation of low-GWP refrigerants in scroll compressor. Performance evaluation of low-GWP refrigerants in scroll compressor is carried out to aid the selection of suitable refrigerant for different applications. The open-source modeling platform PDSim, used for this study, is based on the mechanistic chamber model that has the accuracy comparable to the heuristic methods. A scaling model is developed to design and select the scroll geometry for 1–100 ton range of cooling capacity and seven refrigerants. This method is based on manufacturing constraints and minimization of leakage. Additionally, the ports and the bearings are scaled to make their effect fair for a range of capacities and refrigerants. The simulation model is validated using two example scroll compressors. The predicted mass flow rate and power are within 3% MAE while the isentropic efficiency is within 4% mean absolute error. A validated model and standard AHRI conditions are used for the performance evaluation of the refrigerants over a range of 1 to 100 tons of refrigeration capacity. Seven refrigerants are studied including low-pressure refrigerants, R1234ze(E) and R1234yf, medium-pressure refrigerants, R410A, R32, R454B, and R452B and high-pressure R744. The results suggest that an optimum range exists for each refrigerant to achieve good compressor performance. The leakage area is the primary contributor to the scroll compressor performance.

Flow characteristics of tangential leakage in a scroll compressor for automobile heat pump with CO2

Tangential leakage loss reduction has great significance on improving the performance of scroll compressors. In this study, the flow field of a scroll compressor working with CO2 was numerically investigated. The development characteristics of the tangential leakage flow in different working chambers were carried out, which was obtained by analyzing the field quantities distributions. The impacts of the radial clearances and sidewall roughness on the tangential leakage were also taken into consideration, in order to explore the feasible method of the flow control for the tangential leakage in scroll compressors. Results showed that the tangential leakage flow had various characteristics in the suction and compression chambers due to the different interactions between the tangential leakage flow and mainstream. Owing to little reverse pressure gradient, the tangential leakage flow maintained the typical jet form in the suction chambers. By contrast, the mixing of the tangential leakage flow and mainstream induced the passage vortex and secondary flows in the compression chamber. The secondary flow was the primary factor that results in the occurrence of localized high temperature region rather than the tangential leakage. With the increase of the radial clearance, the volumetric efficiency declined and the discharge temperature increased rapidly. In terms of flow control of the tangential leakage, the increase of sidewall roughness by 2 µm could achieve the same effect as the decrease of the radial clearance by 4 µm, while the volumetric efficiency increased by almost 5% and average discharge temperature decreased by 5 K.

Thermodynamics and flow unsteadiness analysis of trans-critical CO2 in a scroll compressor for mobile heat pump air-conditioning system

Heat pump air-conditioning system operating with trans-critical CO2 is a promising technology on electric vehicles, and scroll compressor has played a vital role in micro heat pump air-conditioning system. In order to obtain a better performance of scroll compressor for CO2, internal flow characteristics should be investigated. In this paper, an unsteady Reynolds Average Navier-Stokes of working process in a scroll compressor operating with trans-critical CO2 was firstly carried out. The effect of CO2 properties tables resolution on numerical simulation was investigated in detail. Then, some phenomena including pre-compression and over-compression in the working process were presented. Finally, physical mechanisms of asymmetric leakage flow considering influence of aerodynamics and thermodynamics were revealed. The results indicated that CO2 properties tables resolution hardly affects simulation results considering fierce fluctuations of CO2 properties near critical point. Periodic pre-compression and over-compression was mainly induced by geometrical structure and operation mechanism of scroll compressor. Asymmetric flow fields in circumferential direction were also observed due to unilateral inlet and orbiting scroll rotation. Meanwhile, so-called “quasi-centrosymmetric” leakage flow was captured in compression chambers owing to the non-uniform distribution of flow field. The results provide an instrumental guidance for optimal design of trans-critical CO2 scroll compressor.

Investigation on the Performance Improvement of the Scroll Compressor by DLC Film

The material property of orbiting scroll surface, mainly affects the life and performance of scroll compressors. Generally, the anodic oxide film (AOF) is used in the surface treatment of the domestic orbiting scroll, which has numerous drawbacks such as poor adhesion of the film-substrate and easy wear failure. In this paper, a process producing the diamond-like carbon film (DLCF) on the surface of an orbiting scroll by unbalanced magnetron sputtering technology was proposed based on the mechanical characteristics of the scroll compressor and the surface treatment method of the orbiting scroll. The friction coefficient, microhardness, film-substrate adhesion and other performances of the AOF and DLCF were analyzed from the data measured by various test facilities. The refrigeration capacity, power and volumetric efficiency of compressors with different coatings were analyzed and compared by tests under different operating conditions with fixed values of refrigerant charge and oil content. The surface morphology of the coatings was then studied by scanning electron microscope to identify the microstructure after the operation. The results showed that a more even and dense surface was obtained by the DLCF compared with the AOF, which improved the wear resistance of the surface. The surface friction coefficient was only 0.11 as the Cr transition layer markedly enhanced the bonding strength. The DLCF displayed more properties of graphite with the thickness of only 0.73 μ m. The volumetric efficiency of the compressor under the nominal operating condition increased by 5.8%.

Variable thickness scroll compressor performance analysis—Part I: Geometric and thermodynamic modeling

In order to investigate the performance of variable thickness scroll compressors, a detail mathematical modeling based on energy and mass balances is established in this two-part. In part I, the geometric modeling and thermodynamic modeling are developed. The profile based on circle involute, high order curve, and arc is built up using the base line method. The volume of working chambers from suction to discharge is defined. Thereafter, the evolution and derivative of the working chamber volume with respect to the orbiting angle are discussed. The energy and the mass balance for working chamber are described. Suction gas heating, radial and flank leakage, heat transfer between the working fluid, scroll wraps and plates are considered in the thermodynamic modeling. The established geometric modeling and thermodynamic modeling can provide better understanding of the variable thickness scroll compressor working process. The dynamical modeling and model validation are reported in part II.

Variable thickness scroll compressor performance analysis—Part II: Dynamic modeling and model validation

In order to investigate the performance of variable thickness scroll compressor, a detail mathematical modeling based on energy and mass balances is established in this two-part. In part II, dynamic modeling and model validation are developed. Temperature, pressure, mass flow of working chambers, friction loss power of moving parts, efficiency, and shaft power are investigated by solving the mathematical modeling. The experimental rig for variable thickness scroll compressor based on involute of circle, high order curve and arc is set up. From the comparison of the simulated and measured data, it can be seen that the compressor model predicts the mass flow, discharge temperature, and shaft power very well. So the proposed mathematical modeling can accurately describe all the suction, compression, and discharge processes for variable thickness scroll compressor.

Study on Mathematical Model in Working Process of Automotive Air Conditioning Scroll Compressor

In order to study the working features of automotive air conditioning scroll compressor, this paper uses mathematical model of working process to analyze it. After studying working process, a equation of suction volume is given. The thermodynamic model of compression chamber and back pressure chamber includes mass conservation and energy conservation. Based on Hydromechanics, leakage models of radial leakage and tangential leakage are discussed. The model lays a foundation of automotive air conditioning scroll compressor performance simulation.

Study on Scroll Profile Design Using Involute of Elliptic for Scroll Compressor

The scroll compressor has the conjugate motion of meshing by the fixed scroll and the planet scroll. Several kinds of geometrical curves can be adopted to form the scroll compressor profile such as involute of circle with variable and constant radius, algebraic spiral, and so on, to improve the performance of scroll compressor. This study proposes a new scroll profile design using elliptic involute and two-envelope method to create a new conjugate meshing scroll of variable cross section. The curve of the scroll section on both sides can be specified as an arbitrary mathematical function. First, the base scroll swept out by the central base circle. Next, the base circle translation path envelope of the planet scroll is moved by the basic involute curve. The base circle translation path envelope is the first envelope. The second envelope generated by the planet scroll conjugate profile is the fixed scroll. By using two-envelope method, the variety of conjugate scroll can be produce with the cross section and symmetrical variables for parametric design.

Analysis of Orbiting Scroll Overturning for Scroll Compressor

Studies on leakage and friction have received considerable attention in scroll compressor, especially which between the fitting surface of orbiting scroll and fixed scroll, as they affect the scroll compressor performance. According to the scroll compressor working principle and structure, combined with the force model of the orbiting scroll, the overturning moment on the orbiting scroll was analyzed and verified by a specific example, in which the azimuth angle and of the overturning moment action line were calculated and compared. The results show that the overturning moment will have a significant effect not only on the leak and friction loss at the fitting surface of orbiting and fixed scroll, also on the dynamic characteristics of the orbiting scroll due to the linear change of the azimuth angle and the unstable of the azimuth angle . The result is helpful for the study on leakage, friction, and the dynamics and tribology coupling problem research of scroll compressor.

Simulation of Radial Deformation for Orbiting Scroll Wrap in a Scroll Compressor

Based on assumptions and tests of the discharge temperatures land pressures for a scroll compressor, a simulation of radial deformations of the orbiting scroll wrap is performed. All simulations show that the radial deformation of scroll wrap varies complicatedly in outer part. Although the deformations are controlled by the temperature of scroll wrap, the inner pressures of scroll wrap can make the radial deformation more uniform. So reducing temperature difference between the discharge and suction temperatures, using the material with lower thermal expansion coefficient are several effective means to improve the performance of scroll compressor in engineering practice.

Simplified Calculation for Thermal Deformation of Scroll Wrap Height in a Small-Parameter Scroll Compressor

For the scroll wrap in small-parameter scroll compressor, its temperatures under stable operating condition are analyzed and the simulations for thermal deformation of scroll wrap height are performed. By fitting the simulations, a formula for simplified calculation of thermal deformation of scroll wrap height is proposed. The maximum deviations between simplified calculations for thermal deformation of orbiting scroll wrap height in a scroll compressor and simulations by FEM are no more than 5%, so the simplified calculation for thermal deformation of scroll wrap height is feasible. The experiment for the scroll compressor in which the orbiting scroll wrap is modified based on simplified calculation shows the modification for scroll wrap considering deformation of scroll wrap height can improve obviously the performances of scroll compressor. At the same time, reducing the temperature differences between the discharge and suction temperatures, limiting scroll wrap height, using the material having lower thermal expansion coefficient, and selecting a larger thickness of scroll wrap are other several effective means to reduce the influence of thermal deformation of scroll wrap height and to improve the performance of scroll compressor in engineering practice.

Investigation of suction process of a large R134a scroll compressor

The suction process of a scroll compressor was investigated. The investigation started from the numerical simulation of the entire scroll compressor working process. The simulation included the upper main bearing housing, thrust plate, scrolls, dummy and discharge ports, check valve, plenum, and discharge line. The basic geometric features and physical mechanisms that the scroll compressor performance is associated with were simulated first. The working fluid was Refrigerant 134a. The suction process was studied as a part of the integrated working environment. The fundamental mechanism of the suction process was defined. The interaction of the compressor design features was quantified. The overall parameters were calculated from the field quantities. The relationship between design details, flow physics, and performance characteristics was established. The methodology developed and the data obtained can be applied to the design and optimization of scroll compressors.

Numerical analysis on the effects of refrigerant injection on the scroll compressor

Refrigerant injection is an effective method to improve the performance of the scroll compressor and its system under high compression ratio working conditions. This paper intends to find the exhaustive relationship between the injection parameters and the compressor’s performance. Based on a thermodynamic model, the effects of various parameters of refrigerant injection on general performance and inner compression process of scroll compressor have been investigated. As a result, it is found that the injected scroll compressor will get the maximum indicated efficiency when the ratio of inner compression ratio and outer compression ratio is a right value. The right value is 1 for the isentropic compression process, and smaller than 1 for a real compression process. Finally, the effects of all the injection factors on the compression work, refrigerant mass flow rate, p– h diagram, volumetric efficiency, and indicated efficiency are investigated detailedly.

An investigation of the performance of a scroll compressor under liquid refrigerant injection

In this study, fundamental and practical influence of liquid refrigerant injection on the performance of a refrigerant scroll compressor has been investigated experimentally and theoretically. In the theoretical analysis, a compression model of vapor/liquid mixture is developed by taking account of heat transfer from the cylinder wall to suction, compression and injection refrigerant. An experiment has been done under the condition of keeping the oil temperature constant in order to investigate the fundamental influence of the liquid refrigerant injection on the compressor performance, and the results were compared with the theoretical ones. It was found that the injection basically increases the compression power and decreases the compressor efficiency, though the situation depends on the condition of the heat transfer to the injection refrigerant. And furthermore, the performance of the liquid refrigerant injection compressor under practical operating condition without controlling the oil temperature has been investigated. Under this condition, the compressor showed recovery and slight improvement of performance due to the decrease of the oil and cylinder temperatures by the injection. In addition, influence of the refrigerant injection on the oil viscosity and refrigerant solubility in the oil, which relate mechanical loss and reliability of the compressor, have been discussed.