无油螺杆空压机余热ORC回收系统运行特性研究

Research on operation characteristics of organic Rankine cycle recovery system for waste heat of oil-free screw air compressor

针对无油螺杆空压机排气的实际工况,利用ORC(organic Rankine cycle)发电系统对其进行余热回收。建立了涡旋膨胀机及ORC系统数学模型,耦合膨胀机变工况运行特性,分析了空压机排气压力、环境温度对膨胀机及系统性能的影响。结果表明:涡旋膨胀机在环境温度较低或空压机排气压力较高时发生欠膨胀,相反则发生过膨胀现象。排气压力升高,膨胀机的膨胀比增大,指示效率先增大后减小。ORC系统净功率、热效率与余热回收率随着排气压力的增大而增大,随着环境温度的升高而减小,系统净效率与余热回收率最高值为7.02 kW与5.44%。低环境温度、高排气压力时系统热经济性优势明显。

It utilizes an organic Rankine cycle(ORC)power generation system for waste heat recovery from an oil-free screw air compressor,based on its actual operating conditions.The mathematical model for scroll expander and ORC system are established,integrating the variable working condition operation characteristics of expander to analyze the influence of air compressor exhaust pressure and ambient temperature on the expander and system performance.The results show that under expansion occurs when the ambient temperature is low or the exhaust pressure of air compressor is high,while over expansion occurs otherwise.The expansion ratio of expander increases with the increase of exhaust pressure,and the indicating efficiency increases first and then decreases with the increase of exhaust pressure.The net power,thermal efficiency and waste heat recovery rate of the ORC system increase with the increase of exhaust pressure and decrease with the increase of ambient temperature.The net efficiency and the maximum waste heat recovery rate of the system are 7.02 kW and 5.44%.The thermo-economic advantage of the system is more obvious when the ambient temperature is low and the exhaust pressure is high.