Effect of non-ideal gas working fluid on power and efficiency performances of an irreversible Otto cycle
Di Wu, Yanlin Ge, Lingen Chen, Lei Tian
Abstract
Abstract Based on the irreversible Otto cycle model, applying finite-time-thermodynamic theory, this paper takes power and efficiency as the objective functions, further studies the cycle performance under the condition of non-ideal gas working fluid, analyzes the effects of different loss items and freedom degree ( d ) of monatomic gas on the cycle performance, and compares performance differences of ideal gas and non-ideal gas under different specific heat models. The results demonstrate that, with the increase of d , the maximum-power-output ( P max ), the maximum-thermal-efficiency ( η max ), the corresponding optimal compression-ratio ( <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <m:msub> <m:mrow> <m:mrow> <m:mo stretchy="false">(</m:mo> <m:mrow> <m:msub> <m:mrow> <m:mi>γ</m:mi> </m:mrow> <m:mrow> <m:mtext>opt</m:mtext> </m:mrow> </m:msub> </m:mrow> <m:mo stretchy="false">)</m:mo> </m:mrow> </m:mrow> <m:mrow> <m:mi>p</m:mi> </m:mrow> </m:msub> </m:math> ${({\gamma }_{\text{opt}})}_{p}$ ) and efficiency ( η P ) at the P max point, and the corresponding optimal compression ratio ( <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <m:msub> <m:mrow> <m:mrow> <m:mo stretchy="false">(</m:mo> <m:mrow> <m:msub> <m:mrow> <m:mi>γ</m:mi> </m:mrow> <m:mrow> <m:mtext>opt</m:mtext> </m:mrow> </m:msub> </m:mrow> <m:mo stretchy="false">)</m:mo> </m:mrow> </m:mrow> <m:mrow> <m:mi>η</m:mi> </m:mrow> </m:msub> </m:math> ${({\gamma }_{\text{opt}})}_{\eta }$ ) and power ( P η ) at the η max point will all increase; the P max , <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <m:msub> <m:mrow> <m:mrow> <m:mo stretchy="false">(</m:mo> <m:mrow> <m:msub> <m:mrow> <m:mi>γ</m:mi> </m:mrow> <m:mrow> <m:mtext>opt</m:mtext> </m:mrow> </m:msub> </m:mrow> <m:mo stretchy="false">)</m:mo> </m:mrow> </m:mrow> <m:mrow> <m:mi>p</m:mi> </m:mrow> </m:msub> </m:math> ${({\gamma }_{\text{opt}})}_{p}$ , η max , <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <m:msub> <m:mrow> <m:mrow> <m:mo stretchy="false">(</m:mo> <m:mrow> <m:msub> <m:mrow> <m:mi>γ</m:mi> </m:mrow> <m:mrow> <m:mtext>opt</m:mtext> </m:mrow> </m:msub> </m:mrow> <m:mo stretchy="false">)</m:mo> </m:mrow> </m:mrow> <m:mrow> <m:mi>η</m:mi> </m:mrow> </m:msub> </m:math> ${({\gamma }_{\text{opt}})}_{\eta }$ , η p and P η will decrease with the increases of three irreversible losses; the specific heat model has only quantitative effect on cycle performance but no qualitative effect; under condition of non-ideal gas specific heat model, the power and efficiency are the smallest.