The Stirling engine,as a closed-cycle power machine,exhibits excellent emission characteristics and broad energy adaptability.Second-order analysis methods are extensively used during the foundational design and therm...The Stirling engine,as a closed-cycle power machine,exhibits excellent emission characteristics and broad energy adaptability.Second-order analysis methods are extensively used during the foundational design and thermodynamic examination of Stirling engines,owing to their commendable model precision and remarkable efficiency.To scrutinize the effect of Stirling engine design parameters on the cyclical work output and efficiency,this study formulates a series of differential equations for the Stirling cycle by employing second-order analysis methods,subsequently augmenting the predictive accuracy by integrating considerations of loss mechanisms.In addition,an iterative method for the convergence of the average pressure was introduced.The predictive capability of the established model was validated using GPU-3 and RE-1000 experimental data.According to the model,parameters such as the operational fluid,porosity of the regenerator,and diameter of the wire mesh and their influence on the resulting work output and cyclic efficiency of the Stirling engine were analyzed,thereby facilitating a broader understanding of the engine's functional characteristics.These findings suggest that hydrogen,owing to its lower dynamic viscosity coefficient,can provide superior output power.The loss due to flow resistance tends to increase with the rotational speed.Additionally,under conditions of elevated rotational speed,the loss from flow resistance declines in cases of increased porosity,and the enhancement of the porosity to diminish flow resistance losses can boost both the output work and the cyclic efficiency of the engine.As the porosity increased further,the hydraulic diameter and dead volume in the regenerator continued to expand,causing the pressure drop within the engine to become the dominant factor in the gradual reduction of output power.Furthermore,extending the length of the regenerator results in a decrease in the output work,although the thermal cycle efficiency initially increases before eventually decreasing.Based on these insights,this study pursues the optimal designs for Stirling engines.展开更多
Knowing the optimal operating parameters of Stirling engines is important for efficient combustion through adaptability to changed pressures and oxygen atmospheres. In this study, the optimum operating conditions for ...Knowing the optimal operating parameters of Stirling engines is important for efficient combustion through adaptability to changed pressures and oxygen atmospheres. In this study, the optimum operating conditions for efficient combustion in a singular Stirling engine combustor at different oxygen atmospheres were investigated and determined. Numerical simulations were performed to investigate the effects of ejection ratio and pressure on combustion performance. In an oxygen/carbon dioxide atmosphere, the results show that increasing the ejection ratio substantially alters the flame distribution in the Stirling engine combustor, increasing heat transfer and external combustion efficiency. In contrast, increasing the ejection ratio reduces the average and maximum temperatures of the Stirling engine combustor. Increased pressure affects the flame distribution in the Stirling engine combustor and impedes the flow and convective heat transfer in the combustor, reducing the overall external combustion efficiency at pressures above 6.5 MPa. In an air/carbon dioxide atmosphere, an increased ejection ratio reduces the average and maximum temperatures in the Stirling engine combustor. However, the overall flame distribution does not change substantially. The external combustion efficiency tends to increase and then decrease because of two opposing factors: the increase in the convective heat transfer coefficient and the decrease in the temperature difference. Increasing pressure inhibits forced convection heat transfer in the Stirling engine combustor, reducing external combustion efficiency, which drops from 78% to 65% when pressure increases from 0.2 MPa to 0.5 MPa.展开更多
Sheila Sundaram在研究对称群上关于子词序的具有特定秩的子偏序集的同调表示时,得到了一个关于第二类Stirling数的恒等式,并提出如何给出此恒等式的一个组合证明这样一个公开问题。本文旨在给出此恒等式的两个新的证明以及重新构造前...Sheila Sundaram在研究对称群上关于子词序的具有特定秩的子偏序集的同调表示时,得到了一个关于第二类Stirling数的恒等式,并提出如何给出此恒等式的一个组合证明这样一个公开问题。本文旨在给出此恒等式的两个新的证明以及重新构造前人使用的一个反号对合以给出一个对合证明,从而回答了Sundaram提出的问题。此外,我们还给出了此恒等式左侧和式的一个组合解释,这一组合解释源自于Mansour和Munagi的结果。Sheila Sundaram obtained an identity between Stirling numbers of the second kind while studying representations of the symmetric group on the homology of rank-selected subposets of subword order. She posed an open question that how to give a combinatorial proof of this identity. The aim of the paper is to present two new proofs as well as reproduce a sign-reversing involution proof of this curious identity, thereby answering the question posed by Sundaram. Moreover, we also provide a combinatorial interpretation of the left-hand side of this identity which is originally due to Mansour and Munagi.展开更多
基金supported by Sichuan Science and Technology Program(No.24NSFSC4579)National Natural Science Foundation of China(No.12305193)+2 种基金Sichuan Science and Technology Program(No.23NSFSC6149)National Natural Science Foundation of China(No.12305194)Technology on Reactor System Design Technology Laboratory Stable support Funding(No.2023_JCJQ_LB_003).
文摘The Stirling engine,as a closed-cycle power machine,exhibits excellent emission characteristics and broad energy adaptability.Second-order analysis methods are extensively used during the foundational design and thermodynamic examination of Stirling engines,owing to their commendable model precision and remarkable efficiency.To scrutinize the effect of Stirling engine design parameters on the cyclical work output and efficiency,this study formulates a series of differential equations for the Stirling cycle by employing second-order analysis methods,subsequently augmenting the predictive accuracy by integrating considerations of loss mechanisms.In addition,an iterative method for the convergence of the average pressure was introduced.The predictive capability of the established model was validated using GPU-3 and RE-1000 experimental data.According to the model,parameters such as the operational fluid,porosity of the regenerator,and diameter of the wire mesh and their influence on the resulting work output and cyclic efficiency of the Stirling engine were analyzed,thereby facilitating a broader understanding of the engine's functional characteristics.These findings suggest that hydrogen,owing to its lower dynamic viscosity coefficient,can provide superior output power.The loss due to flow resistance tends to increase with the rotational speed.Additionally,under conditions of elevated rotational speed,the loss from flow resistance declines in cases of increased porosity,and the enhancement of the porosity to diminish flow resistance losses can boost both the output work and the cyclic efficiency of the engine.As the porosity increased further,the hydraulic diameter and dead volume in the regenerator continued to expand,causing the pressure drop within the engine to become the dominant factor in the gradual reduction of output power.Furthermore,extending the length of the regenerator results in a decrease in the output work,although the thermal cycle efficiency initially increases before eventually decreasing.Based on these insights,this study pursues the optimal designs for Stirling engines.
基金Supported by the Shanghai Rising Star Program (Grant No. 21QB1403900)the Shanghai Municipal Commission of Science and Technology (Grant No. 22170712600)。
文摘Knowing the optimal operating parameters of Stirling engines is important for efficient combustion through adaptability to changed pressures and oxygen atmospheres. In this study, the optimum operating conditions for efficient combustion in a singular Stirling engine combustor at different oxygen atmospheres were investigated and determined. Numerical simulations were performed to investigate the effects of ejection ratio and pressure on combustion performance. In an oxygen/carbon dioxide atmosphere, the results show that increasing the ejection ratio substantially alters the flame distribution in the Stirling engine combustor, increasing heat transfer and external combustion efficiency. In contrast, increasing the ejection ratio reduces the average and maximum temperatures of the Stirling engine combustor. Increased pressure affects the flame distribution in the Stirling engine combustor and impedes the flow and convective heat transfer in the combustor, reducing the overall external combustion efficiency at pressures above 6.5 MPa. In an air/carbon dioxide atmosphere, an increased ejection ratio reduces the average and maximum temperatures in the Stirling engine combustor. However, the overall flame distribution does not change substantially. The external combustion efficiency tends to increase and then decrease because of two opposing factors: the increase in the convective heat transfer coefficient and the decrease in the temperature difference. Increasing pressure inhibits forced convection heat transfer in the Stirling engine combustor, reducing external combustion efficiency, which drops from 78% to 65% when pressure increases from 0.2 MPa to 0.5 MPa.
文摘Sheila Sundaram在研究对称群上关于子词序的具有特定秩的子偏序集的同调表示时,得到了一个关于第二类Stirling数的恒等式,并提出如何给出此恒等式的一个组合证明这样一个公开问题。本文旨在给出此恒等式的两个新的证明以及重新构造前人使用的一个反号对合以给出一个对合证明,从而回答了Sundaram提出的问题。此外,我们还给出了此恒等式左侧和式的一个组合解释,这一组合解释源自于Mansour和Munagi的结果。Sheila Sundaram obtained an identity between Stirling numbers of the second kind while studying representations of the symmetric group on the homology of rank-selected subposets of subword order. She posed an open question that how to give a combinatorial proof of this identity. The aim of the paper is to present two new proofs as well as reproduce a sign-reversing involution proof of this curious identity, thereby answering the question posed by Sundaram. Moreover, we also provide a combinatorial interpretation of the left-hand side of this identity which is originally due to Mansour and Munagi.
