| Summary: | Using finite time thermodynamic theory, an irreversible steady-flow Lenoir cycle model is established, and expressions of power output and thermal efficiency for the model are derived. Through numerical calculations, with the different fixed total heat conductances (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>U</mi><mi>T</mi></msub></mrow></semantics></math></inline-formula>) of two heat exchangers, the maximum powers (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>P</mi><mrow><mi>max</mi></mrow></msub></mrow></semantics></math></inline-formula>), the maximum thermal efficiencies (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>η</mi><mrow><mi>max</mi></mrow></msub></mrow></semantics></math></inline-formula>), and the corresponding optimal heat conductance distribution ratios (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>u</mi><mrow><msub><mi>L</mi><mi>P</mi></msub><mo stretchy="false">(</mo><mi>o</mi><mi>p</mi><mi>t</mi><mo stretchy="false">)</mo></mrow></msub></mrow></semantics></math></inline-formula>) and (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>u</mi><mrow><msub><mi>L</mi><mi>η</mi></msub><mo stretchy="false">(</mo><mi>o</mi><mi>p</mi><mi>t</mi><mo stretchy="false">)</mo></mrow></msub></mrow></semantics></math></inline-formula>) are obtained. The effects of the internal irreversibility are analyzed. The results show that, when the heat conductances of the hot- and cold-side heat exchangers are constants, the corresponding power output and thermal efficiency are constant values. When the heat source temperature ratio (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>τ</mi></semantics></math></inline-formula>) and the effectivenesses of the heat exchangers increase, the corresponding power output and thermal efficiency increase. When the heat conductance distributions are the optimal values, the characteristic relationships of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>P</mi><mo>-</mo><msub><mi>u</mi><mi>L</mi></msub></mrow></semantics></math></inline-formula> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>η</mi><mo>-</mo><msub><mi>u</mi><mi>L</mi></msub></mrow></semantics></math></inline-formula> are parabolic-like ones. When <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>U</mi><mi>T</mi></msub></mrow></semantics></math></inline-formula> is given, with the increase in <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>τ</mi></semantics></math></inline-formula>, the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>P</mi><mrow><mi>max</mi></mrow></msub></mrow></semantics></math></inline-formula>, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>η</mi><mrow><mi>max</mi></mrow></msub></mrow></semantics></math></inline-formula>, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>u</mi><mrow><msub><mi>L</mi><mi>P</mi></msub><mo stretchy="false">(</mo><mi>o</mi><mi>p</mi><mi>t</mi><mo stretchy="false">)</mo></mrow></msub></mrow></semantics></math></inline-formula>, and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>u</mi><mrow><msub><mi>L</mi><mi>η</mi></msub><mo stretchy="false">(</mo><mi>o</mi><mi>p</mi><mi>t</mi><mo stretchy="false">)</mo></mrow></msub></mrow></semantics></math></inline-formula> increase. When <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>τ</mi></semantics></math></inline-formula> is given, with the increase in <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>U</mi><mi>T</mi></msub></mrow></semantics></math></inline-formula>, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>P</mi><mrow><mi>max</mi></mrow></msub></mrow></semantics></math></inline-formula> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>η</mi><mrow><mi>max</mi></mrow></msub></mrow></semantics></math></inline-formula> increase, while <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>u</mi><mrow><msub><mi>L</mi><mi>P</mi></msub><mo stretchy="false">(</mo><mi>o</mi><mi>p</mi><mi>t</mi><mo stretchy="false">)</mo></mrow></msub></mrow></semantics></math></inline-formula> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>u</mi><mrow><msub><mi>L</mi><mi>η</mi></msub><mo stretchy="false">(</mo><mi>o</mi><mi>p</mi><mi>t</mi><mo stretchy="false">)</mo></mrow></msub></mrow></semantics></math></inline-formula> decrease.
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