Abstract
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.
Highlights
The HFC system is a device that converts part of the difference of the chemical energy of the water vapor molecule and the hydrogen molecule and oxygen half molecule into electrical work [1]
As typical positive displacement compressors, scroll and screw compressors are more suitable for HFC power generation systems of vehicles with a stacking power of less than 100 kW
Since the research and test prototype is applied to the vehicle PEMFC system, it is necessary to analyze and study the changes in the working chamber volume of the compressor according to the requirements of the fuel cell stack for the volume flow and exhaust pressure of the air supply subsystem; the calculation equations for the working chamber volume of the oil-free double-wrap scroll compressor are as follows [10]: Discharge chamber: Vd = hpt(4φs + 5π)
Summary
The HFC (hydrogen fuel cell) system is a device that converts part of the difference of the chemical energy of the water vapor molecule and the hydrogen molecule and oxygen half molecule into electrical work [1]. Ooi et al [14] used the CFD method to analyze the two-dimensional non-steady-state numerical simulation of the scroll compressor, and found that the heat transfer and leakage between the working chambers have an impact on the fluid distribution in the working chamber, and that the pressure of the distribution has the least impact in the chamber. Conducted three-dimensional unsteady-state numerical simulation of compression and found that the shape and area of the compressor inlet will affect the pressure distribution in the discharge chamber. A three-dimensional unsteady-state numerical simulation of a PEMFC air supply subsystem (suitable for a 45 kW stack) of oil-free double-wrap scroll compressor with a volume flow qv = 4 m3 /min was studied, under rated operating function. The basic geometric parameters of the CP-type single-screw compressor are shown in Table 2; Figure 1b illustrates the basic structure of the screw and star-wheel of the screw compressor
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