•A lower pressure ratio vapor injection scroll compressor is devised and tested.•Performance of the injection compressor is studied under low ambient temperatures.•The injection process is more ...efficient at lower evaporation temperatures.•A theory model with correlations of compressor efficiencies is built and verified.
Vapor injection technology is a promising method to improve the performance of heat pump systems on electric vehicles. In this work, an experimental study on a low pressure ratio vapor injection scroll compressor was carried out under low ambient temperature conditions. Comparative experiments were conducted for various injection pressures, compressor speeds, and evaporation temperatures. The typical flow and heat transfer characteristics were obtained and analyzed, especially the compressor volumetric efficiency and compressor efficiency. The results showed that the heating performance was improved and discharge temperature was reduced with the increasing injection pressure at a higher compressor speed and a lower evaporation temperature. The volumetric efficiency and compressor efficiency both decreased with the increasing injection pressure. The maximum heating capacity could increase by 16% and the maximum discharge temperature reduction would reach 8 °C for the vapor injection process compared with non-injection process under the evaporation temperature of -22 °C. Furthermore, a semi-empirical model with correlations of volumetric efficiency and compressor efficiency was developed. The results were validated and showed a reasonable agreement with experimental results.
•Two types of two-stage water vapour compression methods were proposed.•Thermal characteristics of the two methods were investigated and evaluated.•The cascaded method was good for applications with ...low saturation temperature rises.•The combined method achieved high saturation temperature rise at limited flow rates.•The combined system showed promising with high compression and energy efficiencies.
Water vapor compression is a key technology that greatly affects system performance in heat pump and mechanical vapor compression/recompression applications. In this paper, two-stage water vapor compression methods (cascaded centrifugal compressors and combined centrifugal and twin-screw compressors) were proposed and studied to deal with the water compression process with large suction volume flow rates and high compression pressure ratios. A mathematical model was developed, and the thermal characteristics, achievable volume flow rate and saturation temperature rise of the two water compression systems were presented. The two-stage compression process using cascaded centrifugal compressors was found to be better for applications with total saturation temperature rise lower than 40 °C. The two-stage compression process using combined centrifugal and twin-screw compressors was found to satisfy applications with a saturation temperature rise as high as 80 °C. Further investigation showed that the second method could deliver a suction volume flow rate of 1418 m3/min with a suction vapor temperature of 50 °C using a current market-available twin-screw compressor with a capacity of 600 m3/min. The performance of the combined systems was largely affected by the pressure ratio and the compressor efficiency, system suction vapor temperature, and total vapor saturation temperature rise. The analyses showed that the combined system had high energy efficiency above 3.4 under all studied working conditions.
•Parameters of a compressor model are identified using Newton iteration method.•A feedforward air flow controller is proposed to eliminate the load disturbance.•Both the performances of the ...compressor and the controller are evaluated.
Air compressor which is to used to deliver the air (including about 21% oxygen) to the cathode channel for electrochemical reaction is a crucial component for the polymer electrolyte membrane (PEM) fuel cell. The working characteristics of the compressor greatly influences the fuel cell performance as well as the durability. In this paper a semi-physical modeling method is adopted to analyze the operating property of a centrifugal compressor which is more suitable for automotive fuel cells because of its compactness. This model includes many physical and empirical parameters which are very difficult to determine. Interior-point optimization method based on Newton iteration is used to identify those parameters. The result shows that the modeled compressor map has a good agreement with the experimental data. Meanwhile, the compressor efficiency is analyzed and compared with the measurement to further validate the developed model. This compressor is thus adapted to a validated 10 kW fuel cell model. A dynamic feedforward controller is proposed based on the load torque to control the air mass flow, eliminating the disturbance produced by the compressor load in transient. The simulation results show that this compressor could satisfy requirements of the fuel cell under dynamic load situations while keeping both the fuel cell and compressor with high efficiencies.
Large-scale centrifugal compressors play an important role in modern industry. As the core component of a centrifugal compressor, the blades are prone to fatigue failure due to the long-term ...operation in complex conditions. If the early stage blade failure cannot be found in time, catastrophes could be caused by this potential risk. However, since the blades work in a closed environment, there is always lack of effective monitoring techniques. Aiming at this challenge, pressure pulsation signal inside the compressor is studied in this paper for the condition monitoring and weak fault waring of blades indirectly. A big issue is that the fault characteristic induced by incipient blade crack is quite weak, which will be much weaker in pressure pulsation signal, and interfered with strong noise. Hence, appropriate feature extraction methods are urgently needed. An adaptive bistable stochastic resonance method combined with multi-scale noise tuning is proposed to improve this problem. As the classical stochastic resonance is just suitable for small parameter signal, normalized scale transformation is adopted to overcome this disadvantage. In addition, numerical stability analysis for the stochastic resonance system is conducted to ensure the convergence of system output and improve the characteristic enhancement performance of proposed method. Simulation signal is constructed to verify the effectiveness of the proposed method first. Then, the experimental pressure pulsation signal is analyzed by this method. Analysis results verify that the proposed diagnostic framework can effectively identify the weak characteristic frequency induced by blade crack and has potential for long-term condition monitoring and fault warning of large-scale centrifugal compressor blades.
•Focus on the weak fault detection of centrifugal compressor blades.•A pressure pulsation based diagnosis method is proposed.•An adaptive bistable stochastic resonance (BSR) based on GA is proposed.•Noise tuning is utilized to improve the feature enhancement performance of BSR.•Output stability of a BSR system is numerically analyzed.
•The paper provides additional test data of S-CO2 centrifugal compressor performances.•The best set of loss models for the supercritical CO2 compressor design is proposed.•The predicted results show ...good agreement with all experimental data.
Due to the lack of test data of a supercritical CO2 compressor operating under supercritical CO2 conditions, the work of loss model validation for supercritical CO2 compressor could not be conducted successfully before. Therefore, as the first step, this study gathers the existing accessible experiment data as much as possible while conducting additional supercritical CO2 compressor performance experiments to validate the loss models for the supercritical CO2 compressor. To evaluate the reliability of test results, the measurement uncertainty is estimated from the experiment data. Then, three different combinations of loss models based on the mean streamline method are compared with six available experimental cases to find the most suitable combination of loss models for the supercritical CO2 compressor design and analysis. The combination of loss models proposed by Lee was found to predict pressure ratio and isentropic efficiency of supercritical CO2 compressors operating both on-design and off-design conditions successfully. It is expected that the set of loss models presented herein can be utilized as a conceptual design tool in the preliminary design stage of supercritical CO2 compressors.
The hierarchical structure of the compressor industry facilities is presented, taking into account their interaction and mutual influence. Analysis of production facilities that implement the gas ...compression technology, unstable operating conditions, the cause and nature of their occurrence, the degree of influence on the impact on facilities of different levels was performed. The technologies of adaptation of compressor equipment to unstable operating conditions are systematized, at the same time, depending on the emerging tasks, adaptation technologies are divided into stages (levels) of implementation. Present problems of scientific and methodological nature on implementation of technologies of adaptation of compressor equipment to unstable operating conditions at different levels of hierarchical structure of facilities are shown.
Options of approach to selection of standard size of anti-surge control valves in relation to two-section (two-shell) centrifugal compressor unit with three control circuits (first section, second ...section, general circuit) are considered. The problems arising from valve selection due to incorrect calculation of gas dynamic characteristics of compressor sections are shown. Field of application — natural and associated gas production and compression facilities.
•The performances of reciprocating and rolling piston compressors are assessed in a domestic heat pump water heater.•Novel approach of detailed compressor modeling coupled to a lumped ...quasi-steady-state model of the system.•The system is analyzed under winter, summer and standard conditions.•Thermodynamic and mass flow losses are evaluated during the system operation.
This paper reports a comparative analysis of a reciprocating compressor and a rolling piston compressor, both optimized for a domestic heat pump water heater. The analysis involves a novel approach that couples the detailed modeling of each compressor to a lumped quasi-steady-state model for the remainder of the system operating under summer, winter and standard conditions. Considering the summer conditions, the COP of the heat pump operating with the rolling piston compressor was found to be 12.3% higher than when using the reciprocating compressor. The heat pump operating with the rolling piston compressor was also more efficient under winter conditions, but the COP was only 7.6% higher. The superheating and leakage losses in the rolling piston compressor remained almost the same with the two sets of operating conditions, but the losses in the suction and discharge systems of the reciprocating compressor were considerably lower under the winter operating conditions.
The procedure for conditionally dynamic (quasi-dynamic) hydraulic and thermal calculation of recirculation lines of compressor stations has been developed. As an example, the solution to the problem ...of reconstruction of the linear compressor station of the main gas pipeline is considered. Using the developed methodology, options for upgrading the existing recirculation line in order to increase its throughput are proposed. The gas temperature change in the recirculation line is analyzed due to various factors (heat exchange with soil, throttling) at the starting modes of constant and variable rotations of the compressor rotor. The analysis of the change in the recirculation cycle time and the rate of temperature growth at the compressor inlet per unit time is performed.
