Positive Displacement Compressors Research Articles

Experimental study on system characteristics of vapor compression refrigeration system using small-scale, gas-bearing, oil-free centrifugal compressor

Small-scale refrigeration centrifugal compressors hold the potential for superior efficiency compared to currently used positive displacement compressors. However, traditionally, centrifugal compressors have been employed in large refrigeration systems with cooling capacity of several hundred kilowatts or more. Conversely, the application of small-scale centrifugal compressors in smaller refrigeration systems, with cooling capacity in the tens of kilowatts, has largely remained theoretical, lacking practical experimental studies. For a better understanding of the operational characteristics of such systems, this study constructed a 45 kW R245fa refrigeration system test bench based on the small-scale oil-free centrifugal compressor utilizing gas foil bearings. The experimental investigation analyzed the impact of refrigerant charge amount, compressor speed, and coolant flow rate on system performance. Results indicate that the system achieves its peak cooling capacity of 49.73 kW with a system COP of 3.64 at 65,000 rpm. Moreover, at 50,000 rpm, the system demonstrates its highest system COP of 4.23 with a cooling capacity of 26.07 kW. In comparison to traditional positive displacement compressor refrigeration systems, it exhibits higher energy efficiency. Additional simulation studies were conducted to evaluate the effects of substituting R1233zd(E) for R245fa on the system performance and to assess the feasibility of such a substitution.

Simplified steady-state modeling of positive displacement compressors

Semi-empirical models for predicting the suction flow rate, input power, and discharge temperature are proposed for positive displacement compressors. A data set containing twenty-six combinations of compressors and refrigerant pairs wherein each compressor was tested over a wide range of operating conditions is used to evaluate the models. The model fitted parameters and prediction errors of each data set is discussed.

A forward-curved blade centrifugal compressor for anode recirculation in proton exchange membrane fuel cells

Anode recirculation is crucial for the stable and efficient operation of automotive proton exchange membrane fuel cells (PEMFCs). The circulation is commonly driven by ejectors or positive displacement compressors, rather than centrifugal compressors, which have difficulty overcoming large pressure drops at low flow rates despite their promising attributes such as stable control and smooth operation. To address this gap, the present work proposes a novel design of a magnetically levitated centrifugal compressor featuring forward-curved blades. The comprehensive design process of this compressor is described, incorporating a novel design methodology, numerical simulations, and experimental validation. The compressor operates stably within the low-power range of typical automotive PEMFCs. At the design point, it achieves a static-to-static pressure ratio of 1.10 with an isentropic efficiency of 50 % and a system efficiency of 41 %. The test results demonstrate that the forward-curved blade centrifugal compressor is a viable option for anode recirculation in PEMFCs.

A comparative analysis of a new semi-empirical model and the AHRI polynomial model for positive displacement compressors

A semi-empirical model has been proposed to predict the refrigerant mass flow rate, input power, and discharge temperature of positive displacement compressors. The prediction accuracy of the proposed model is compared with the accuracy of the AHRI polynomial model. To examine the generalizability of the models, a resampling methodology is used to compare prediction accuracy that results when smaller data sets are used to fit the models. These results show that the semi-empirical model has similar mass flow rate and input power prediction errors to the AHRI polynomial model and results in more consistent performance when smaller data sets are used to fit the model. The results also show that the AHRI polynomial is not a good choice for the prediction of discharge temperature and that the proposed model is much more suitable for this purpose.

Optimization of Propane Compressor Capacity and Flow Rate in Refrigeration System

Plant X requires pressurized gas in the refrigeration system unit, which plays an important role in the smooth operation of the production system. This is because propane gas is used as a support for the main operating system in the manufacture of LPG. More precisely as a cooling medium for tools called Chiller and Sub-Cooler. To obtain the pressurized propane gas, a screw compressor type positive displacement compressor is used. Propane Compressor C-440 A has a function, namely to circulate propane gas which is used to cool or lower the temperature of hydrocarbon gas. Considering the important role of the Propane Compressor C-440 A screw compressor, it is necessary to optimize it to determine the performance of the compressor. Optimization steps need to be carried out to find the most effective and efficient operating conditions. By lowering the suction temperature and increasing the rotational speed of the rotor. The reference parameter is that the targeted capacity has increased by 9%, resulting in the actual calculation of 30614.40 cfm and optimization of 30902.03 cfm. The mass flow rate is targeted to increase by 4%, resulting in an actual calculation of 627.92 lbm/min and an optimization of 654.80 lbm/min. With this, it can be calculated that the economic value is 26.89 lbm/min.

Process model design for positive displacement compressors and their experimental validation: Comparison of Optimal Experimental Design and Machine Learning

Valid simulation models play a critical role in enhancing efficiency in development processes and minimizing experimental efforts. As a result, ensuring accurate predictions through model discrimination, Model Calibration, and Validation (MoCaVal) has become increasingly important and is a necessary step to analyze the behavior and evaluate the effectiveness of systems during their initial design stages. Additionally, to achieve the climate objectives, it is imperative that heat pumps predominantly perform the building sector’s heating. The effectiveness of heat pumps hinges on the performance of the compressor. Therefore, there is a requirement for valid compressor models. However, currently, there is no universal compressor model that applies to all refrigerants and designs. Therefore, every refrigerant or design modification requires the development or adaptation of models. Since creating new models is a time-consuming procedure, automated techniques are advantageous.This paper compares two automated model development methods, Optimal Experimental Design (OED) and Machine Learning (ML), to create valid simulation models within the MoCaVal framework. OED is used to calibrate existing simulation models, while ML is employed to develop new models. Our comparison of the two methods focuses on a fixed-speed scroll compressor of 4 kW nominal power, using R410A and featuring 51 measurement points. Using the Full Factorial Plan (FFP) and the D-Optimal Experimental Design (D-OED), predefined models for mass flow rate, electrical power, isentropic and volumetric efficiency were calibrated. Employing the FFP, Machine Learning (ML) was also applied through support vector regression.The OED reduces experimental effort by 75–90 % compared to the FFP while only slightly increasing the average uncertainty by 0.30–0.79 %. For the FFP, MoCaVal achieved uncertainties of 0.52–3.9 % for calibrated models and 0.34–0.56 % with ML models. Therefore, within the design space, ML outperforms calibrated models based on the FFP and OED regarding uncertainty. However, since machine learning models were trained on the FFP, additional research is needed to demonstrate their potential for reducing test time and extrapolating results.

A Literature Review of the Positive Displacement Compressor: Current Challenges and Future Opportunities

Positive displacement compressors are essential in many engineering systems, from domestic to industrial applications. Many studies have been devoted to providing more insights into the workings and proposing solutions for performance improvements of these machines. This study aims to present a systematic review of published research on positive displacement compressors of various geometrical structures. This paper discusses the literature on compressor topics, including leakage, heat transfer, friction and lubrication, valve dynamics, port characteristics, and capacity control strategies. Moreover, the current status of the application of machine learning methods in positive displacement compressors is also discussed. The challenges and opportunities for future work are presented at the end of the paper.

Thermodynamic properties of oil droplets in oil-injected screw compressors and their influencing factors

As a typical positive displacement compressor, screw compressors are widely used in various industrial fields with a fast-growing trend, especially with the boost of the application of oil injection technology. The oil injection process inside the screw compressor is complicated and difficult to be captured by direct observation experiment, so is the accompanying heat transfer process. On the basis of single particle dynamics, the Lagrangian method is used to establish a spatial kinematic model of oil droplets in the simplified chamber of an oil-injected screw compressor, the droplet trajectory is analyzed. The relationship between the oil droplet diameter, injection velocity and temperature and the free flight time of oil droplets in the compression chamber is obtained. In order to investigate the liquid-gas two-phase flow after oil injection, the Level Set Method is adopted to simulate the oil distribution in the compression chamber. The impacting process of oil droplet on a hot wall is simulated, the influence of oil injection parameters such as the injection speed, temperature difference, droplet diameter, and the initial velocity on the heat transfer between oil droplets and hot gas and the wall is analyzed theoretically. For the simulated cases studied, the oil droplet diameter has the greatest effect on the gas-liquid heat transfer, while the temperature difference plays a greater role in the heat transfer between the oil droplet and the hot wall than other factors. The research in this paper helps to further understand and accurately predict the heat transfer process in oil-injected screw compressors, which is important for improving the energy efficiency of screw compressor.

A Novel Screw Compressor with a Shunt Enhanced Compression and Pulsation Trap (SECAPT)

Some positive displacement (PD) compressors are equipped with automatic discharge valves such as reed valves that open automatically whenever the cavity pressure is slightly larger than the outlet pressure to deal effectively with varying pressure ratio applications. Screw compressors today do not have such valves, resulting in off-design conditions known as the under-compression or over-compression when the cavity pressure at discharge is deviating from the outlet pressure. Compressor efficiency suffers and pulsation/noise becomes worse under these conditions. Some type of controls are desired such as a discharge pulsation dampener or a variable volume ratio (often called variable Vi) slide valve design to lessen or cure the discharge pressure mismatch problems.Injecting gas vapor into a screw compressor cavity during internal compression phase has been known to be beneficial in enhancing compressor performance and has been widely used in HVAC&R industry known as the Economizer. However, the underlining principle of the Economizer has thus far not been explored for optimizing compression schemes of a screw compressor in general. This paper introduces a self-sensing and self-correcting compression process that can be “derived or deduced” from the Perfect Gas Law by optimizing for multiple design criteria such as compressor efficiency, pulsation/noise abatement, and cost and footprint reduction for a screw operating over a wide range of pressures. The scheme, called SECAPT (Shunt Enhanced Compression And Pulsation Trap), is then investigated and optimized numerically by a new CFD code for one industrial case: a bulk truck loading application where compressor pressure varies from no pressure rise to maximum load. The numerical simulations illustrate that SECAPT is tentatively capable of achieving multiple targets as theorized.

Laser-Optical Shear-Flow Analysis across the Annular Gap of a Simplified Displacement Compressor Model

The present experimental feasibility study testifies the two flow measurement techniques Defocusing Particle Tracking Velocimetry (DPTV) and Interferometric Particle Imaging (IPI) for their applicability to measure the two-phase flow of thin (sub-millimeter) annular rotor-stator gaps such as occur across for the leakage flow e.g. in the housing gap of oil-injected rotary positive displacement compressors (RPDC). To provide unrestriced optical access to the annular gap and in turn eliminate secondary effects, a simplified displacement compressor model has been developed and fabricated from perspex. The proof-of-concept results of both experimental campaigns (DPTV & IPI) are discussed and avenues for future efforts towards a straight-forward and accurate applicability of either method are elaborated.

Analysis of the Primary Means for Increasing the Efficiency of Positive Displacement Compressors

Analysis of the Primary Means for Increasing the Efficiency of Positive Displacement Compressors

The Survey on Reciprocating Gas Compressor: A Review

Abstract— This paper represent the survey on reciprocating gas compressor and there effects on different location whether it is onshore or offshore. Reciprocating air compressors are the foremost ordinarily used compressor for domestic and industrial functions. These papers also investigate the improving volumetric efficiency of two stage reciprocating gas compressor by providing IC Tube bundle and cooling system. These surveys perform the experiments of a two-stage with double-cylinder reciprocating gas compressor system with gas and different cooling systems were performed. This study develops a higher understanding on the impact of honing within the cylinder that reduces the surface roughness within the cylinder and ends up in bigger air output. In these review paper there are various things that are considered for designing the cylinder for the purpose of compressing the gas in differential uses. In these review the effecton reciprocating is seen whether it is steady state or in a thermal state conditions, so to get this results they have done assessments on various conditions and for various purpose. The aim of these survey papers is to define the proper way of research done on reciprocating compressor i.e. the research paper data, methodology, verification and validation, the way of results and discussion of various assessments test, etc. These paper mainly focus on the positive displacement compressor and that of the sub part is reciprocating gas compressor and their design, modelling, analysis and development i.e. from raw stage to the final stage of reciprocating gas compressor. From these survey we also find the whole process of reciprocating gas compressor and there future scope. Keywords— Reciprocating Gas Compressor, Honing, Two Stage Cylinder, Cooling, Volumetric efficiency

Innovative hybrid device for the simultaneous damping of pressure pulsations and vibrations in positive displacement compressor manifolds

Manifold vibrations in refrigerating compressor manifolds are the result of pressure pulsations as well as compressor-generated mechanical vibrations. In this article, an analysis of a device combining a TMD (tuned mass damper) and a shaped nozzle for pressure pulsation attenuation is presented. The nozzle shape and geometry is determined on the basis of our previous findings using 3D analysis. The nozzle pulsation attenuation is caused by viscous and vorticity energy dissipation. The nozzle is mounted inside the pipe in the chosen position using springs with tuned stiffness. The nozzle mass and spring stiffness create the TMD. The simulation of the TMD damping using the OpenModelica SimulationX package is presented with kinetic energy transfer from a vibrating pipe to the TMD. It transpired that the result on the pressure pulsations damping of the vibrating nozzle is not as high as it is in the case of a nozzle in a fixed position due to the clearance between the nozzle and the pipe that is necessary in the TMD case. Nevertheless, vibrations are more efficiently damped using the combined TMD and nozzle damping action (28%) than a fixed nozzle (13%). This innovation makes it possible to reduce vibration and pressure pulsation using one device, which is especially important for small refrigerating manifolds, where the size of the damping element is important and vibration reduction leads to noise attenuation. The hybrid suppression device is currently patent pending.

Mathematical modeling and parametric study of the limaçon rotary compressor

In this paper, a class of rotary positive displacement compressors which is known as the limaçon compressor is introduced. The main feature of such a compressor is that profiles of its housing and rotor and the motion of its rotor are developed from a mathematical curve called the limaçon of Pascal. A mathematical model of the limaçon compressor, which incorporates the mass flow of the working fluid, the leakage loss, the dynamic response of the discharge valve, as well as the thermodynamic behaviors, is formulated, and the simulation of such a model has been performed to study the operational characteristics of the limaçon compressor. A parametric analysis is also conducted to investigate the effects of various parameters on the compressor performance. Based on the results, it is found that the machine performance deteriorates as the operating speed increases despite an initial rise in the volumetric efficiency. Additionally, the isentropic efficiency appears insensitive to the change of the pressure ratio, whereas a negative effect on the volumetric efficiency is noticed when the pressure ratio is increased. The effect of the valve diameter on the over-compression loss has also been studied, and the result indicates that a smaller valve diameter leads to a higher level of fluid over-compression.

Performance Analysis and Test Research of PEMFC Oil-Free Positive Displacement Compressor for Vehicle

In order to study the matching characteristics of the positive displacement air compressor and the PEMFC (proton exchange membrane fuel cells), air supply subsystem, the basic operating performance parameters of the scroll and single-screw air compressors were analyzed with the focus on the oil-free double-wrap scroll compressor. According to the thermodynamic model and three-dimensional unsteady-state numerical simulation, the variation of the temperature, pressure, and velocity was obtained. Besides, under the rated operating condition of the compressor, the inlet and outlet mass flow rate of the fluid in the working chamber with the orbiting angle of the crank was achieved. Based on the built test platform, the actual working process of scroll and screw compressors was analyzed. This study indicates that the volume flow can be significantly increased by improving the speed of the positive displacement compressor. Based on the experimental measurement, when the height of the scroll tooth of the scroll compressor increases by 5 mm, the volume flow of the prototype SC2 increases by 0.17 m3/min and the exhaust temperature is reduced by 13 °C at the rated speed.

General Approach for Estimating the Energy Efficiency of Cooling in Positive Displacement Compressors

General Approach for Estimating the Energy Efficiency of Cooling in Positive Displacement Compressors

On the Design of a Class of Rotary Compressors Using Bayesian Optimization

The optimization process of compressors is usually regarded as a ‘black-box’ problem, in which the mathematical form underlying the relationship between design parameters and the design objective is impractical and costly to be obtained. To solve the ‘black-box’ problem, Bayesian optimization has been proven as an accurate and efficient method. However, the application of such a method in the design of compressors is rarely discussed, particularly no work has been reported in terms of the positive displacement type compressor. Therefore, this paper aims to introduce the Bayesian optimization to the design of positive displacement compressors through the optimization process of the novel limaçon compressor. In this paper, a two-stage optimization process is presented, in which the first stage optimizes the geometric parameters as per design requirements and the second stage focuses on revealing an optimum setting of port geometries that improves machine performance. A numerical illustration is offered to prove the validity of the presented approach.

Analysis and Optimization of Over Compression for Rotary Cylinder Compressor Based on PV Test

Rotary cylinder compressor is a novel positive displacement compressor. Theoretical analysis shows that the compressor may have large over compression loss. Based on PV test, the over compression characteristics of rotary cylinder compressor was analyzed, and the over compression loss accounts for 5.5% of the indicated power. The over compression was optimized, and the optimized over compression loss is only 0.5% of the indicated power. By further comparing the energy efficiency improvement of the whole compressor, it is found that the improvement effect is equivalent to that of the over compression, and the effectiveness of the scheme is confirmed.

Development of a Reconfigurable Prototype Peristaltic Compressor

Traditional positive displacement compressors require valves, internal volume ratios or both to operate. These two features generate the majority of the losses in compressors. The peristaltic compressor is a novel compressor architecture that feature valve-less compression with variable volume ratios, which provides the potential for highly efficient compression. This paper will present a design of a reconfigurable prototype peristaltic compressor and illustrate how the structure of the compression chamber and actuation pattern affect the compressor efficiency. The prototype utilizes a flexible diaphragm constrained and sealed against a female die to make a compression chamber. Linear actuators with male dies press the diaphragm sequentially against the female die to move and compress the fluid. Preliminary experiments were performed using air as the working fluid for volume ratios ranging from 1.143 to 8 and operational frequencies ranging from 1.28 to 2.31 Hz. These results suggest that the actuation pattern has an impact on the major parameters such as mass flow, displacement volume, and pressure ratio which influence the overall efficiency of the compressor.

2D transient analysis of suction process for coupled vane compressor

Although CFD has been widely applied to the study of positive displacement compressors, the primary challenge remains in the generation of solution domain of complicated geometry and accurate handling of the deformation of the working chamber during the compressor operation. In this paper, a 2D transient CFD simulation employing the overset mesh method is performed on the Coupled Vane Compressor (CVC) with air as the working fluid. Initial results revealed the presences of flow reversal and circulation zones at the suction channel resulting in the reduction of effective suction flow area. This has significantly reduced the mass intake. Proposed modification to the suction channel design has resulted in an increase of mass flow rate of 6.97% when operating at 1500rpm. Simulation approach, results and design modification are presented and discussed in this paper.