Positive Displacement Compressors Research Articles

On Rotor Profling of Internally Geared Screw Machines

Abstract The internally geared screw machine represents a novel type of positive displacement compressor which consists of an inner and outer rotor. Both rotors rotate in the same direction but are each centered on offset parallel axes. The rotor profiles are designed to create multiple continuous contact points between the rotors, forming several separate working chambers whose volumes vary from minimum to maximum and back to minimum during a single rotation of the outer rotor. For a gas or two-phase working fluid, adjusting the discharge port geometry allows internal compression to occur before discharge. Previous research has focused on using the well-known rotor profling method, which employs a circular pin to generate the inner and outer rotor profiles. Although the rack method for rotor profile generation has been described and investigated for conventional screw machine rotor profiles, it has never been applied to internally geared screw machine profile generation. This paper provides an initial description and application of the rack method for generating internally geared screw machine profiles. Potential benefits of using the rack method compared to conventional methods for rotor profile generation in internally geared machines are discussed. Additionally, the limitations of using the rack method for internal gearing are presented and illustrated through various examples and applications.

Investigation of Pressure Pulsation and Vibration of the Internally Geared Screw Compressor

Abstract The Internally Geared Screw Machine (IGSM) is a relatively novel and promising type of positive displacement compressor concept that takes inspiration from classic gerotor pumps. The IGSM uses two rotors rotating in the same direction about parallel axes while maintaining continuous contact between both rotors which isolates several working chambers. By using ported end plate, the IGSM can determine the timing of the fluid entering and exiting the working chamber. There are several key advantages to the IGSM over traditional twin-screw compressors including reduction of the rotor to casting leakage, elimination of the blow hole area, reduction in sliding velocity at the point of contact, and a uniform circumferential rotor temperature profile. Although there is some research regarding the geometric profiling and chamber modeling of this type of machine, there is no research currently available on the pressure pulsation and vibration characteristics of the IGSM. The purpose of this paper is to provide an initial look into the pressure pulsation and vibration characteristics of the IGSM and how they differ from that of a traditional twin-screw machine. By explicating the key differences between the IGSM and the industry standard twin-screw compressor, this paper aims to better understand an important yet underdeveloped area of IGSM design.

Astigmatism Quantification for Depth Localization of Bubbles and Tracers across Curved Surfaces

Abstract The present combined theoretical/experimental study addresses the impact of astigmatism on the two-phase flow diagnostics across the curved surfaces of liquid test-rig containments. In the present context, the target application is the two phase leakage-flow diagnostics across the annular housing gaps of oil-injected rotary positive displacement compressors (RPDC). Earlier studies by the authors identified the Defocusing Particle Tracking Velocimetry (DPTV) and Interferometric Particle Imaging (IPI) as particularly promising combination of flow measurement techniques to investigate the liquid and disperse gas phases inside the annular housing gap of RPDCs. The test-rig-specific influence of astigmatism on the resulting optical transfer function for a quantitative evaluation of the recorded defocused particle images (PI) is first compared to the theoretically derived circular PI diameter upon pure defocussing and subsequently tested for both classes of PIs, i.e DPTV and IPI. To mimic the optical configuration of optically accessible lateral surfaces of typical RPDC test rigs, a circular beaker glass (CBG) of comparable diameter is chosen for the experimental campaign. The results are discussed and future efforts for advanced PI-evaluation strategies are outlined on the grounds of the drawn conclusions.

Thermodynamic simulation of a water-injected twin-screw steam compressor

Abstract Decarbonisation of industrial heating and process steam generation is crucial for the mitigation of advancing climate change. High-temperature heat pumps can meet these demands while effectively integrating with renewable energy sources, outperforming traditional heating and boiling systems, especially when operating with natural refrigerants. Since compressor efficiency is critical for the effectiveness of heat pump systems, particular care is required in compressor design and specification. Detailed thermodynamic simulations of the compressor system are indispensable in this process. The compression of fluids with a negative saturation vapour curve leads to challenging temperature increases during compression, with substantial superheating of the working fluid. In this context, a promising approach is the injection of liquid working fluid into the compressing chambers for internal cooling. This introduces new complexity to compressor simulations for heat-pump applications. In this work, a novel two-phase approach for multi-chamber model simulations of positive displacement compressors is presented. Initially, a quasi-isentropic reference process for vapour compression with internal liquid injection is introduced and efficiency ratings are derived. Furthermore, the simulation process is described in detail, and comprehensive thermodynamic simulations of a water-injected twin-screw steam compressor are carried out.

High-resolution simulations of gas-liquid Couette-type sealing gap flows

Abstract The two-phase flow in sealing gaps of twin-screw compressors is investigated using highly resolved coupled multiphase simulations. Oil-injected rotary-type positive displacement compressors (RPDC) such as twin-screw machines are used for the compression of refrigerants in HVAC (Heating, Ventilation, and Air Conditioning) systems. The efficiency of such machines is largely determined by the inevitable two-phase surge and gap flows. The simulation of flows in such compressors is still a challenge due to the complexity of the two-phase flow in the narrow gaps (<0.3mm) with organic working fluids and moving boundaries. Due to the rotation of the screws relative to the housing, gaps are present between the rotors and the end plates of the housing and between the tips of the rotors and the cylindrical housing walls. Oil injection can increase the efficiency of screw compressors or expanders by more than 10%, since oil enhances the sealing of the gaps where leakage occurs. On the other hand, additional momentum losses are caused by the two-phase gap flows. The oil injection, however, increases the hydraulic losses which depend on the geometry of the gap, the liquid, and the kinematics of the established multiphase flow in the gap. In this work, a highly efficient, high-resolution numerical method is used for the simulation of the gas-liquid multiphase flow in the screw compressor gap between the rotor tip and the stationary housing. The Lattice-Boltzmann method (LBM) defines the basis of the method used in this work, forming an in-house developed framework in which each fluid phase is solved by a separate solution algorithm. To capture the motion of the liquid-gas phase boundary, a level-set method is used. In the present work, a generic gap flow is considered. A Couette-type flow configuration, where the sealant flow in the gap is driven by the moving inner wall, is investigated. The Reynolds number based on the height of the channel is Re = 20000. Finally, we discuss the impact of bubble-laden sealing gaps on the momentum losses of the system.

Evaluasi Unjuk Kerja Screw Compressor UP5-15-10 di PT XYZ

This paper aims to evaluate the efficiency of screw compressor UP5- 15-10 used at PT XYZ. Screw compressor efficiency is a key factor in the operation of gas processing facilities, then a good understanding of screw compressor operation can improve operational efficiency and reduce energy consumption. The compressor used in this KKW is an Ingersoll Rand UP5-15-10. The UP5-15-10 compressor is used to power pneumatic tools and instrumentation equipment. The UP5-15-10 compressor is included in the rotary type positive displacement compressor, the compressor uses ambient air as its working fluid. UP5-15-10 screw compressor operation, including design data from the manual book and actual data such as incoming air capacity of 65 CFM at a temperature of 186 F with a pressure of 135 Psia getting a power of 13.74 kW from the power specification data of 15 kW obtained efficiency of 91%. The decrease in power in screw compressor UP5-15-10 by 9% is due to the difference in intake capacity between design and actual conditions, this is caused by process needs.

Study of nonequilibrium regenerative heat exchange in positive displacement compressors

BACKGROUND: An important task in the design of thermal engines is the evaluation of power losses in different processes to determine the installation efficiency. One of the processes that generates power losses in the compressor is the process of nonequilibrium regenerative heat exchange (NRHE) of the compressed gas with the working cavity walls. This heat exchange occurs at a significant temperature difference, which can lead to noticeable power losses. Modern compressor design methods do not consider losses from nonequilibrium regenerative heat exchange and do not describe them separately from other types of losses. AIM: This study investigates the mechanism of losses during regenerative heat exchange between the gaseous working flow out and the working cavity walls and evaluates the scale of these losses. METHODS AND RESULTS: This work provides a qualitative description of the mechanism for the formation of losses from NRHE. As a result of solving the problem of unsteady thermal conductivity, an analytical expression for calculating such losses is derived based on the Gouy-Stodola theorem. CONCLUSIONS: The study revealed that power losses from NRHE account for a significant share in the overall balance of machine losses. Parameters influencing the magnitude of these losses were also determined, and recommendations were developed to reduce them.

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.

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.

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.

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.