工质变比热和传热损失对Otto循环性能的影响

用有限时间热力学的方法分析空气标准Otto循环，由数值计算给出了存在传热损失和工质变比热时循环功率与压缩比、效率与压缩比以及功率和效率的特性关系，并分析了传热损失和工质变比热对循环性能的影响特点。通过分析可知传热和变比热特性对Otto循环性能有较大影响，所以在实际循环分析中应该予以考虑。     

多孔介质发动机再热循环有限时间热力学分析

建立了多孔介质（PM）发动机循环的有限时间热力学模型，对PM循环进行了分析，导出了存在摩擦及传热损失时循环功率与压缩比、效率与压缩比以及功率效率的特性关系，同时由数值计算分析了压缩比、预胀比、传热损失和摩擦损失对循环性能的影响特点。将PM循环与Otto循环进行了比较，结果表明：PM循环的性能要优于Otto循环的性能。     

工质变比热和传热损失对内可逆矩形循环性能的影响

用有限时间热力学理论和方法分析空气标准矩形循环,由数值计算给出了存在传热损失和工质变比热时循环功与压缩比、效率与压缩比以及功和效率的特性关系,并分析了传热损失和工质变比热对循环性能的影响特点,通过分析可知传热和变比热特性对矩形循环性能有较大影响。     

工质变比热对内可逆Lenoir循环性能的影响

用有限时间热力学理论和方法分析内可逆Lenoir循环,建立了存在工质变比热和传热损失时的循环模型,由数值计算得到了循环的临界压缩比范围,给出了功与压缩比、效率与压缩比以及功和效率的特性关系,并分析了传热损失和工质变比热对循环性能的影响特点,通过分析可知变比热特性和传热损失对Lenoir循环性能有较大影响,对该循环的应用具有一定指导意义。     

包含多变过程的不可逆普适往复式循环有限时间热力学分析

建立了存在传热损失、摩擦损失和工质变比热时的不可逆普适往复式循环模型,用有限时间热力学理论和方法分析其性能。由数值计算给出功率与压比、效率与压比以及功率与效率的特性关系,并分析了摩擦损失、工质变比热和多变指数对循环性能的影响。所得结果包含了内可逆和不可逆Otto循环和Diesel循环的结果,但又有一定的拓展。     

包含多变过程的Dual-Miller循环有限时间热力学分析

建立了包含多变过程的空气标准Dual-Miller循环模型,其中包含2个多变过程、2个加热过程和两个放热过程。应用有限时间热力学理论分析其性能,导出了考虑传热损失时的输出功率、热效率表达式,通过数值计算,获得了循环功率与压缩比,效率与压缩比以及功率与效率之间的特性关系,分析了多变指数和预胀比对循环性能的影响。在特定条件下,所建立的模型可简化为其他不同的循环模型,获得结果具有一定的普适性。     

内可逆工质恒比热Meletis-Georgiou循环有限时间热力学建模与性能优化

应用有限时间热力学理论建立内可逆工质恒比热Meletis-Georgiou(MG)循环模型,导出循环各点温度、循环功、效率等性能参数表达式,并对MG循环性能进行分析和优化。应用数值计算方法,得到循环功与效率特性关系;分别以循环功和效率为目标,对压缩比、转换比、过膨胀比进行优化并得到一系列优化结果;分析了传热损失及循环各参数对循环性能与优化结果的影响。所得结果对实际MG发动机的设计优化有一定指导作用。     

不可逆Dual循环的功率效率特性

用有限时间热力学的方法考虑空气标准 Dual循环 ,导出了存在摩擦及传热损失的空气标准 Dual循环的功率与压缩比、效率与压缩比以及功率和效率的最佳特性关系 ,同时由数值计算分析了摩擦和传热对循环性能的影响特点。     

考虑摩擦时Otto循环功率效率特性新析

对有摩擦时的 Otto循环进行了有限时间热力学分析。建立了一种新的模型 ,以循环的活塞平均速度和摩擦系数为基准求得了摩擦损失功率以及功率和压缩比、效率和压缩比的关系 ,进而得到了功率与效率关系 ,并进行了计算和讨论。结果表明 ,与实际热机循环的性能特性一致。     

包含多变过程的内可逆Brayton循环热力学分析

应用有限时间热力学理论,建立了包含多变过程的内可逆往复式Brayton循环模型,由数值计算得到了多变指数n取不同值时的循环输出功率与压缩比、效率与压缩比、输出功率与效率之间的特性关系,分析了多变指数对循环性能的影响。结果表明:随着n的增加,当n k (k为绝热指数)时,γ_(P(opt))(最大输出功率对应的最佳压缩比)和P_η(最大效率对应的循环输出功率)减小,γ_(η(opt))(最大效率对应的最佳压缩比)和η_P(最大输出功率对应的循环效率)增加;当n k时,γ_(P(opt))和γ_(η(opt))减小,η_P和P_η减小。选取适当的多变指数,调整压缩比在γ_(P(opt))≤γ≤γ_(η(opt))范围内可得循环最优性能区域。     

Thermodynamic Analysis and Comparison of Performances of Air Standard Atkinson,Otto, and Diesel Cycles with Heat Transfer Considerations

This paper focuses on the overall performances of Otto, Atkinson, and Diesel air standard cycles. This study compares performance of these cycles with regard to parameters such as variable specific heat ratio, heat transfer loss, frictional loss, and internal irreversibility based on finite‐time thermodynamics. The relationship between thermal efficiency and compression ratio, and between power output and compression ratio of these cycles are obtained by numerical examples. In this study, it is assumed that during the combustion process, the heat transfer occurs only through the cylinder wall. The heat transfer is affected by the average temperature of both the cylinder wall and the working fluid. The results show that for each cycle, with the increase of the compression ratio in the specific mean piston speed, power output and thermal efficiency first increase and after reaching their maximum value, start to decrease. The results also indicate that maximum power output and maximum thermal efficiency of an Atkinson cycle could be higher than the values of these parameters in Diesel cycle and Otto cycle in the same operating conditions. The maximum power output and the maximum thermal efficiency of the Otto cycle have the lowest value among studied cycles. By increasing the mean piston speed, power output and thermal efficiency of Atkinson, Diesel, and Otto cycles start to decrease. The results of this study provide guidance for the performance analysis and show the improvement areas of practical Otto, Atkinson, and Diesel engines.     

Effects of heat transfer and friction on the performance of an irreversible air-standard miller cycle

The performance of an air standard Miller cycle with heat transfer loss and friction-like term loss was analyzed by using finite-time thermodynamics. The relation between the power output and the compression ratio, between the thermal efficiency and the compression ratio as well as the optimal relation between the power output and the efficiency of the cycle are derived. Moreover, the influences of heat transfer loss and friction loss on the cycle performance are analyzed by detailed numerical examples. The results obtained herein include the performance characteristics of different cycles in given conditions, which have universal guidance.     

不可逆Miller循环的功率效率特性

用有限时间热力学的方法考虑空气标准Miller循环，导出存在摩擦及传热损失的空气标准Miller循环的功率与压缩比、效率与压缩比，以及功率和效率的最佳特性关系；同时由数值计算分析了摩擦和传热对循环性能的影响特点。结论包含了各种特定条件下不同循环的特性，具有一定的普适性。     

内可逆矩形循环有限时间热力学分析

应用有限时间热力学理论分析了空气标准矩形循环的性能,导出存在传热损失的空气标准矩形循环的功与膨胀比、效率与膨胀比以及功和效率的特性关系,同时分析了传热损失及循环各参数对循环性能的影响。     

Reciprocating heat-engine cycles

The performance of a generalized irreversible reciprocating heat-engine cycle model consisting of two heating branches, two cooling branches and two adiabatic branches with heat-transfer loss and friction-like term loss was analyzed using finite-time thermodynamics. The relations between the power output and the compression ratio, between the thermal efficiency and the compression ratio, as well as the optimal relation between the power output and the efficiency of the cycle are derived. Moreover, analysis and optimization of the model were carried out in order to investigate the effect of the cycle process on the performances of the cycles using numerical examples. The results obtained herein include the performance characteristics of irreversible reciprocating Diesel, Otto, Atkinson, Brayton, Dual and Miller cycles.     

Optimum outlet temperature of solar collector for maximum work output for an Otto air-standard cycle with ideal regeneration

The optimum solar collector outlet temperature for maximizing the work output for an Otto air-standard cycle with ideal regeneration is investigated. A mathematical model for the energy balance on the solar collector along with the useful work output and the thermal efficiency of the Otto air-standard cycle with ideal regeneration is developed. The optimum solar collector outlet temperature for maximum work output is determined. The effect of radiative and convective heat losses from the solar collector, on the optimum outlet temperature is presented. The results reveal that the highest solar collector outlet temperature and, therefore, greatest Otto cycle efficiency and work output can be attained with the lowest values of radiative and convective heat losses. Moreover, high cycle work output (as a fraction of absorbed solar energy) and high efficiency of an Otto heat engine with ideal regeneration, driven by a solar collector system, can be attained with low compression ratio.