发动机多工况有机朗肯循环中混合工质研究

摘要

The thermal efficiency of an engine is relatively low. Most of the combustion energy is wasted in the at-mosphere. Recently, the utilization of the organic Rankine cycle( ORC) system to recover the waste heat of an en-gine has been taken for improving the fuel economy of the engine and reducing the consumption of fossil fuel re-sources. Through the process of the experiment, the characteristics of the exhaust of a diesel engine under multiple operating conditions were studied and a set of organic Rankine cycle waste-heat recovery systems were designed in this paper. In combination with the experimental results and theoretical calculations, the effects of four kinds of zeo-tropic mixtures on the performance of the organic Rankine cycle waste-heat recovery system under multiple operating conditions,and the impact of the superheat degree and evaporation pressure on the performance of ORC using zeo-tropic mixtures are analyzed;and the variations of the net power output, thermal efficiency, exergy efficiency of the ORC system and the power output increasing rate ( POIR) following the variations of the engine behavior are dis-cussed. The results show that the net power output of the ORC system may reach as high as 24.65 kW. When the superheat is 10 K and the evaporation pressure is 2.0 MPa, the power output of the combined system is increased by 10.63%.%发动机的热效率并不理想，大部分燃料燃烧后的能量被浪费。为了提高发动机的燃油利用效率、降低能源消耗，利用有机朗肯循环系统回收发动机的余热能。通过实验，研究一台柴油机多工况下的排气特点，为此设计一套有机朗肯循环余热回收系统。结合实验结果和理论计算，分析4种非共沸混合工质对多工况下车用发动机有机朗肯循环余热回收系统性能的影响。研究过热度和蒸发压力对非共沸混合工质的有机朗肯循环系统的影响，探讨随着发动机工况的变化，有机朗肯循环系统净输出功率、热效率、（火用）效率及有用功提升率的变化情况。研究结果表明，过热度为10 K，蒸发压力为2．0 MPa时，ORC余热回收系统净输出功率最大可达24．65 kW，联合系统的输出功率提升10．63％。