工质气体振动自由度对热机效率的影响  

INFLUENCE OF GASEOUS WORKING SUBSTANCE'S VIBRATION DEGREE OF FREEDOM ON INTERNAL COMBUSTION ENGINE EFFICIENCY

作　　者：许恒瑞 李列明[2] XU Hengrui;LI Lieming(Xi'an Jiaotong University,School of Energy and Power Engineering,Shaanxi,Xi'an 710049;Department of Physics,Tsinghua University,Beijing 100084)

机构地区：[1]西安交通大学能源与动力工程学院,陕西西安710049 [2]清华大学物理系,北京100084

出　　处：《物理与工程》2021年第6期45-49,共5页Physics and Engineering

摘　　要：国内典型的工科大学物理教材和工程热力学教材在计算内燃机循环效率时,都假设工质气体分子是刚性的而忽略其振动自由度对比热容的贡献。本文修正了这个假设,使用理想气体严格的比热容温度关系考虑了振动自由度的贡献,对萨巴德循环、狄塞尔循环和奥托循环这三种常见的内燃机循环,进行了数值模拟。与前述教科书的简化结果比,我们计算得到的循环效率,在常见参数下,下降了6~12个百分点,而且循环中工质组分、燃烧做功过程的温度等重要因素对循环效率的影响被呈现。这样的修正幅度说明大学物理和工程热力学教材中忽略振动自由度对比热容的贡献是合适的。同时,我们认为,在进行半定量热机效率的理论计算时,工质气体振动自由度的影响是一个值得考虑的因素。When calculating the cycle efficiency of internal combustion engine,the typical textbooks of college physics and thermodynamics in China assume that the working gas molecules are rigid and ignore the contribution of the vibration degree of freedom to the heat capacity.In this paper,we modify this assumption and use the strict specific heat capacity temperature relationship of ideal gas,taking into account the contribution of vibration degrees of freedom,to simulate three common internal combustion engine cycles,namely Sabad cycle,Diesel cycle and Otto cycle.Compared with the simplified results of the above-mentioned textbooks,we found that the strictly calculated cycle efficiency,under the common parameters,decreases by 6%~12%,and the influence of the working substance composition,the temperature of combustion work process and other important factors on the cycle efficiency are presented.Such a correction reflects the rationality of the assumptions in the textbooks.We considered that the influence of the vibration degree of freedom of the working substance is a factor worthy of consideration in the semi-qualitative cycle efficiency calculation.

关 键 词：理想气体比热容 分子振动自由度 萨巴德循环 狄塞尔循环 奥托循环 

分 类 号：TK402[动力工程及工程热物理—动力机械及工程]