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Ziwen Xing - One of the best experts on this subject based on the ideXlab platform.

  • theoretical and experimental research on the working process of screw refrigeration compressor under superfeed condition
    International Journal of Refrigeration-revue Internationale Du Froid, 2007
    Co-Authors: Ziwen Xing
    Abstract:

    Abstract In order to increase the refrigeration capacity and improve the coefficient of performance (COP), an economizer arrangement is used in the refrigeration system with screw refrigeration compressor. In this system, the mid-pressure refrigerant gas from the economizer is injected in the screw refrigeration compressor. So it affects the performance of the compressor. In this paper, the working process of a twin screw refrigeration compressor with economizer under different superfeed pressures is studied. A mathematical model for simulating the working process of screw refrigeration compressor under superfeed condition with the economizer is presented; especially the flow coefficient of superfeed is obtained by the experimental research. To verify the model, the p – V diagrams (pressure–volume diagrams) of screw refrigeration compressor under different superfeed pressures with the economizer are recorded successfully by making use of a micro-type pressure sensor that embedded into the groove at the root of the female rotor on the Discharge Side. The p – V diagrams of theoretical calculation are in good agreement with the results of experimental recorded, which lead to conclusion that the model can be used as a powerful tool for performance prediction of screw refrigeration compressor, also, it is very helpful for refrigeration system design.

  • experimental study on p v indicator diagrams of twin screw refrigeration compressor with economizer
    Applied Thermal Engineering, 2004
    Co-Authors: Huagen Wu, Xueyuan Peng, Ziwen Xing
    Abstract:

    This paper presents the experimental investigation on the effects of the superfeed pressure together with economizer type on the performance of the twin-screw refrigeration compressor by means of the indicator diagram. With a pressure sensor embedded into the groove at the root of the female rotor on the Discharge Side, the pressure within the working chamber of a semi-hermetic twin-screw compressor with an economizer is recorded and then transformed into the indicator diagram. The results thus obtained are utilized to investigate the thermodynamic process of the compressor. It is shown that the compressor with an economizer has higher pressure during almost the whole compression process than without an economizer, resulting in the increase in the indicated power. Under different superfeed pressures, the pressure within the compression experiences different changes. This results in an optimal superfeed pressure for maximized compressor efficiency, which can be identified from the calculated compressor efficiency based on the indicator diagrams. It is also found that the pressure has a rapid increase at the beginning of superfeed process, and then a slow rise even a slight drop at the end of superfeed process, which is caused by the dynamic effect during superfeed process. Furthermore, if the superfeed pressure keeps the same, the pressure during compression in the compressor with the heat exchanger economizer is slightly higher than with the flash tank economizer, due to the higher temperature of superfeed refrigerant gas in the former case.

  • analysis of the working process in an oil flooded screw compressor by means of an indicator diagram
    Proceedings of the Institution of Mechanical Engineers Part A: Journal of Power and Energy, 2002
    Co-Authors: Xueyuan Peng, Ziwen Xing, Liansheng Li
    Abstract:

    This paper presents the results of an experimental investigation of the thermodynamic processes in an oil-flooded screw compressor. The pressure within the working chamber is measured with a small pressure sensor, embedded in the female rotor on the Discharge Side. The results so obtained were transformed into an indicator diagram. Based on the indicator diagrams at various operating conditions, the working process is analysed. Owing to oil restricting back-flow of the gas through the Discharge port, constant-volume compression is not evident even at substantial under-compression conditions, thus making the compressor maintain a high efficiency over a wide range of pressure ratios. However, the additional power consumption resulting from over-compression is comparatively large at pressure ratios lower than that for which the compressor was designed. So a compressor with fixed volume ratio should be designed with the built-in volume ratio low enough to avoid this effect. At the end of the Discharge process, the pressure rises steeply due to increased resistance to oil flow, and therefore, the design of a flow-guiding slot to assist oil Discharge is recommended. Higher rotating speeds increase the pressure slightly, but the losses associated with this are compensated by the increased volumetric efficiency. Thus a screw compressor maintains its isentropic efficiency over a wide range of speeds. Larger oil:gas ratio presents a higher pressure level in the indicator diagram, offsetting the improved sealing effect, and test results show that the appropriate oil:gas mass ratio range is between 8:1 and 20:1.

Shu Pengcheng - One of the best experts on this subject based on the ideXlab platform.

  • theoretical and experimental study on indicator diagram of twin screw refrigeration compressor
    International Journal of Refrigeration-revue Internationale Du Froid, 2004
    Co-Authors: Wu Huage, Xing Ziwe, Shu Pengcheng
    Abstract:

    Abstract In this paper a new mathematical model for calculating the indicator diagram of twin screw refrigeration compressor is presented firstly. The geometric parameters related to the rotation angle of male rotor are used in the model such as groove volume, suction and Discharge port area, slide valve bypass port area, leakage area etc. The effects of internal leakage through five paths, oil injection, gas–oil heat transfer, refrigerant property and partial loading etc. are taken into account simultaneously and separately in the theoretical study. To verify the model and the calculated p–V indicator diagram, experimental recording of p–V indicator diagram of twin screw refrigeration compressor is carried out. Various indicator diagrams are recorded successfully by a small pressure sensor embedded in the bottom of female rotor at the Discharge Side. The results of theoretical calculation are in good agreement with the measured data, which lead to conclusion that the model can be used as a powerful tool for performance prediction and product development.

Wu Huage - One of the best experts on this subject based on the ideXlab platform.

  • theoretical and experimental study on indicator diagram of twin screw refrigeration compressor
    International Journal of Refrigeration-revue Internationale Du Froid, 2004
    Co-Authors: Wu Huage, Xing Ziwe, Shu Pengcheng
    Abstract:

    Abstract In this paper a new mathematical model for calculating the indicator diagram of twin screw refrigeration compressor is presented firstly. The geometric parameters related to the rotation angle of male rotor are used in the model such as groove volume, suction and Discharge port area, slide valve bypass port area, leakage area etc. The effects of internal leakage through five paths, oil injection, gas–oil heat transfer, refrigerant property and partial loading etc. are taken into account simultaneously and separately in the theoretical study. To verify the model and the calculated p–V indicator diagram, experimental recording of p–V indicator diagram of twin screw refrigeration compressor is carried out. Various indicator diagrams are recorded successfully by a small pressure sensor embedded in the bottom of female rotor at the Discharge Side. The results of theoretical calculation are in good agreement with the measured data, which lead to conclusion that the model can be used as a powerful tool for performance prediction and product development.

D. J. Richards - One of the best experts on this subject based on the ideXlab platform.

  • Compressor Station Recycle System Dynamics During Emergency Shutdown
    Journal of Engineering for Gas Turbines and Power-transactions of The Asme, 1996
    Co-Authors: Kamal K Botros, W M Jungowski, D. J. Richards
    Abstract:

    Transient phenomena associated with gas recycling during compressor emergency shutdown (ESD) have been studied both experimentally and numerically. A scaled-down laboratory test rig has been constructed to study the influence of various underlying parameters on ESD operation. Three different configurations representing different design scenarios were tested. The first configuration has a long recycle system with a volume capacitance representing an air-cooled heat exchanger in the recycle loop, and the recycle valve located close to the Discharge Side. The second one is the same as the first except the recycle valve is placed close to the suction Side. In the third configuration, the cooler capacitance was removed from the recycle loop and the piping capacitance on the Discharge Side was further reduced. Shutdown tests were carried out from different steady-state initial conditions varying the recycle valve opening time, and the synchronization time between the compressor ESD signal and valve opening signal. Numerical simulations based on the solution of the full one-dimensional conservation equations using the method of characteristics were also conducted for the above configurations. Good agreement was obtained between measurements and simulation results. Numerical simulations were used to analyze other cases, which were not investigated experimentally, to further investigate themore » interaction between equipment and flow parameters. Results indicate that the valve prestroke time is more crucial than the stroke time and that it should be made short to avoid surging the compressor during ESD. Locating the recycle valve as close as possible to the suction or Discharge of the compressor helps reduce unit surge during shutdown.« less

  • compressor station recycle system dynamics during emergency shutdown
    Volume 3: Coal Biomass and Alternative Fuels; Combustion and Fuels; Oil and Gas Applications; Cycle Innovations, 1994
    Co-Authors: Kamal K Botros, W M Jungowski, D. J. Richards
    Abstract:

    Transient phenomena associated with gas recycling during compressor emergency shutdown (ESD) have been studied both experimentally and numerically, A scaled-down laboratory test rig has been constructed to study the influence of various underlying parameters on ESD operation. Three different configurations representing different design scenarios were tested. The first configuration has a long recycle system with a volume capacitance representing an air cooled heat exchanger in the recycle loop, and the recycle valve located close to the Discharge Side. The second one is the same as the first except the recycle valve placed close to the suction Side. In the third configuration, the cooler capacitance was removed from the recycle loop and the piping capacitance on the Discharge Side was further reduced. Shutdown tests were carried out from different steady state initial conditions varying the recycle valve opening time, and the synchronization time between the compressor ESD signal and valve opening signal. Numerical simulations based on the solution of the full one-dimensional conservation equations using the method of characteristics were also conducted for the above configurations. Good agreement was obtained between measurements and simulation results. Numerical simulations were used to analyze other cases which were not investigated experimentally, to further investigate the interaction between equipment and flow parameters. Results indicate that the valve prestroke time is more crucial than the stroke time and that it should be made short to avoid surging the compressor during ESD. Locating the recycle valve as close as possible to the suction or Discharge of the compressor helps reduce unit surge during shutdown.© 1994 ASME

Huagen Wu - One of the best experts on this subject based on the ideXlab platform.

  • experimental study on p v indicator diagrams of twin screw refrigeration compressor with economizer
    Applied Thermal Engineering, 2004
    Co-Authors: Huagen Wu, Xueyuan Peng, Ziwen Xing
    Abstract:

    This paper presents the experimental investigation on the effects of the superfeed pressure together with economizer type on the performance of the twin-screw refrigeration compressor by means of the indicator diagram. With a pressure sensor embedded into the groove at the root of the female rotor on the Discharge Side, the pressure within the working chamber of a semi-hermetic twin-screw compressor with an economizer is recorded and then transformed into the indicator diagram. The results thus obtained are utilized to investigate the thermodynamic process of the compressor. It is shown that the compressor with an economizer has higher pressure during almost the whole compression process than without an economizer, resulting in the increase in the indicated power. Under different superfeed pressures, the pressure within the compression experiences different changes. This results in an optimal superfeed pressure for maximized compressor efficiency, which can be identified from the calculated compressor efficiency based on the indicator diagrams. It is also found that the pressure has a rapid increase at the beginning of superfeed process, and then a slow rise even a slight drop at the end of superfeed process, which is caused by the dynamic effect during superfeed process. Furthermore, if the superfeed pressure keeps the same, the pressure during compression in the compressor with the heat exchanger economizer is slightly higher than with the flash tank economizer, due to the higher temperature of superfeed refrigerant gas in the former case.