Zhao Yuanyang

Research on oil-free air scroll compressor with high speed in 30 kW fuel cell

Abstract To supply the clean compressed air to a fuel cell system, an oil-free compressor is needed. The working process of the oil-free air scroll compressor and its cooling feature are discussed in this paper. A prototype, delivering 100 m3/h and having a speed of 5000 rpm, is researched. The water from the fuel cell system is used as the lubricant of the bearings and the moving parts of the compressor. The prototype of the oil-free air scroll compressor has been designed, fabricated and tested, and the performances are satisfactory. Whatever material the scroll parts are constructed of, for example, aluminum alloy or titanium alloy, the trend of the compressor delivery with rotary speed is similar. However, the power consumption varies with the materials and the surface coating of the scroll parts because different materials and surface coating have different friction coefficients.

Theoretical and experimental research on scroll expander used in small-scale organic Rankine cycle system

Scroll expander is suitable for small-scale organic Rankine cycle system. In this article, a detailed mathematical model describing the stable and dynamic process of scroll expander is built, an experiment system is set up, and the performance of scroll expander is tested. The results show that the p−V diagram of simulation and experiment show good agreement. The volumetric efficiency of scroll expander increases with rotating speed, and the maximum value is 63% under the tested condition. The isentropic efficiency increases at low rotating speed but then decreases, and the maximum value is 36.4%. Both the stable rotating speed and stable time of scroll expander increase with the electric resistance; here the stable time is defined as the elapsed time when the scroll expander varies from one stable condition to another. Although the transient rotating speed varies periodically with running time when the scroll expander runs stably, the variable quantity can be ignored. The total efficiency of expander and system efficiency first increase with the rotating speed and then decrease, and the maximum values are 41% and 2.9%, respectively, when the Carnot efficiency is 21.2% and the maximum theoretical efficiency is 8%.

Thermodynamic simulation of scroll compressor/ expander module in automotive fuel cell engine

Abstract Considering the leakage and heat transfer, the mathematical model of the scroll compressor/expander module (CEM) used in the automotive fuel cell systems is developed based on thermodynamics theory. The performance of the scroll CEM is simulated at different rotation speed, operating pressure, inlet temperature, and so on. The simulated results show that the power consumed by the scroll CEM is about 50 per cent of that of just the scroll compressor. However, for different operating pressures, the consumed power of the scroll CEM has the least value at the design point. The power consumed by the scroll CEM decreases about 4.5 per cent when the inlet temperature rises from 0 to 35°C. The flowrate of dry air increases with the rise of the scroll CEM rotation speed. Moreover, it decreases 11.4 per cent when the scroll CEM inlet temperature changes from 0 to 35 °C.

Experimental Research on Dynamic Response of Capacity Control System in Reciprocating Compressor

The forces acting on the actuator used in a reciprocating capacity control system are analyzed in this article. The dynamic response of this system is influenced significantly by hydraulic pressure and reset spring force. The performance of dynamic response is tested under different hydraulic pressures and reset springs. The results show that the influence of reset spring force on the downward speed and displacement of actuator is more inconspicuous than the hydraulic pressure, but the reset speeds decrease obviously when the reset spring force is small (SPR2 and SPR3). The maximum downward displacement decreases and the consuming time increases with the decrease in the hydraulic pressure. The maximum downward speed of actuator decreases with the decrease in hydraulic pressure which influences the reliability and life of this system. Therefore, the performance of dynamic response and operating lifetime needs to be considered simultaneously during the design of partial stroke press-off inlet valve capacity control systems.

Experimental Study on Performance Enhancement of Heat Pump With Screw Compressor

The air-source heat pump has been widely used in industrial refrigeration and central air-conditioning applications because of its unique superiority. An important consideration in the design of heat pump is improving its COP (coefficient of performance). In this paper, the results of experimental investigation on the effects of alternative refrigerants (R22, R134a, R404A and R407C) and economizer on the performance of heat pump are presented. The COP of the heat pump used R134a is up to 4.5% higher than R22, but its capacity got a 37.08% decrease. The refrigerant R407C applied in heat pump can improve the capacity up to 7.86% than R22, but its COP shows a decrease up to 5.92%. The refrigerant R404A used in heat pump will result in poor capacity and COP compared to R22. The economizer system used in heat pump will improve the COP, but as the superfeed pressure of the economizer increases, the system COP increases first, and then drops. So there exists an optimal superfeed pressure of the economizer for the best COP. Also, the effect of the economizer on the screw compressor performance is analyzed by recording the P-v indicator diagram.Copyright