Study on Power System Using High Pressure Air Generator for Saving Energy

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A hybrid power system using high-pressure air as working fluid has been proposed and its pefformance and efficiency were studied. This system is mainly composed of a diesel compressor, a high-pressure air tank and an air expander. The diesel compressor generates high-pressure air by compression using energy supplied by combustion in the same cylinder. The Air is transferred into the air tank, stored there and is delivered to the expander to obtain the power output according to the power demand. This system is supposed to have some advantages, that is, reduction in transmission loss using variable output air expander, improvement in engine thermal efficiency due to the limitation of its speed and output and energy saving due to brake energy recovery.The results of energy and exergy analysis show that the ideal cycle of this system has the same thermal efficiency as Brayton cycle and that some parameters such as pressure ratio and cut-off ratio should be optimized for increasing exergy efficiency when various power output is required.The prototype of the air expander was designed and constructed. The test results show that the output power could not be fully controlled over the wide range. The modification of valve shape proved to be effective to extend the controllable output range. In addition the increase in exhaust port time area will give better thermal efficiency and broader power range.