工质变比热条件下内燃机循环普适特性

用有限时间热力学的方法分析空气标准不可逆内燃机循环,导出了考虑工质变比热情况下,存在摩擦及传热损失时,由两个加热过程、两个放热过程和两个绝热过程组成的普适的空气标准不可逆内燃机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工质变比热和循环过程对循环性能的影响特点,比较了工质恒、变比热时循环性能差异。所得结果包含了不可逆往复式Diesel、Otto、Brayton、Atkinson、Dual和Miller 循环的性能特性。     

辐射对流传热对不可逆太阳能Braysson热机性能的影响

建立高温端同时辐射对流传热、低温端对流传热的不可逆太阳能Braysson热机循环新模型,探索有限速率热传导和绝热过程不可逆性等对热机循环性能的影响,基于热力学分析方法,导出热机输出功率和效率的解析表达式,数值计算结果揭示了等压温比、内不可逆参量及与热传导系数和面积有关的匹配参量等对热机性能特性的影响,所得结论不仅能导出其它不可逆太阳能热机的优化性能.且可为太阳能热机的参数设计和性能评价提供新理论参考.     

以广义Redlich-Kwong气体为工质的不可逆回热式斯特林热机循环输出功率和效率

研究了热阻、回热损失和热漏等多种不可逆因素对以广义Redlich-Kwong气体为工质的斯特林热机性能的影响,给出了斯特林热机输出功率和效率的具体表达式并分析非理想回热特性及循环主要性能参数(如循环体积比及工质高低温比等)对循环输出功率和效率的影响.同时指出,只有在理想回热及无热漏的情况下,气体斯特林热机的效率才能达到卡诺效率.     

多孔介质(PM)发动机理想循环热力学分析

本文论述了基于多孔介质燃烧技术的超绝热发动机的原理及其工作过程,建立了PM发动机的热力学模型,对 PM发动机内的PM回热循环进行热力学分析,列出了循环参数如压缩比、预胀比、预压比等对发动机效率、循环功的影响,确定了PM回热循环的两种极限状态。将PM回热循环与发动机的Otto循环、Diesel循环进行比较,结果表明: PM回热循环在保证效率的同时,可以大幅度提高循环功。     

实际闭式中冷回热布雷顿循环新析

用有限时间热力学方法分析了变温热源条件下实际闭式中冷回热布雷顿循环的性能,导出了无因次功率及效率的解析式。由数值计算,分析了循环最优功率和最优效率时的最佳中间压比分配,并研究了中冷度等一些主要循环参数对性能的影响,发现了不管有无回热,中冷都可以提高循环效率这一新结果。     

热泵系统的不可逆度及其热力参数优化

本文采用等价热力变换法,把有内循环不可逆损失和有限热容热源的实际热泵热水器系统变换为等价逆卡诺循环系统,并用定态有限时间热力分析法建立了系统各环节的有效能消耗率方程和系统不可逆度方程,求解了换热器与热泵循环的不可逆耦合问题,重点推导了蒸发器的空气流率与风机消耗功率、传热不可逆损失、蒸发温度、系统性能系数以及不可逆度的关系,算例分析得到了系统的最小不可逆度、最大COP参数所对应的最佳热力参数,所得的最佳冷风温差值与实际基本符合。     

Hyperbar涡轮复合发动机循环的热力学第二定律分析

Hyperbar复合发动机是一种高增压、低压缩比并具有旁通补燃系统的涡轮复合发动机,其特点是在不过分增加热负荷和机械负荷的条件下,可以大幅度地提高功率,并能明显地改善发动机的加速特性和扭矩特性。本文对此新型复合发动机循环进行第二定律分析。文中计算了各种不可逆因素导致的(火用)损失,研究了(火用)效率与平均压力随各主要参数的变化规律,并指出改善发动机性能的途径。本文的研究成果对于合理应用及发展     

恒温热源闭式燃气轮机中冷循环性能优化

本文运用有限时间热力学(FTT)理论,导出了恒温热源条件下闭式燃气轮机不可逆中冷循环功率、效率和功率密度的解析式,分别优化了循环最优功率和功率密度时各换热器热导率分配、中间压比和总压比,并比较了相应性能。     

以铁磁材料为工质的不可逆Ericsson制冷循环的热经济性能优化

据朗之万理论导出铁磁材料的磁化强度和熵表式,构建以铁磁材料为工质的不可逆回热Ericsson制冷循环,分析和评估该制冷循环的热经济及热力学性能,揭示有限热源、回热器效率、外磁场强度等参量对循环热经济性能及其相应的制冷率和性能系数等的定量影响。所得结果为实际磁制冷机循环参数优化设计提供参考。     

螺旋波导压缩频率调制脉冲的初步研究

利用螺旋波导对频率调制脉冲进行压缩可大幅度提高脉冲峰值功率。利用所编Matlab程序对螺旋波导的色散特性进行了计算和分析,获得了波纹幅度和纵向周期长度等结构参数对其色散特性的影响规律;给出了脉冲功率压缩比的计算公式,对不同脉宽和频带宽度、不同频率调制形式的微波脉冲通过螺旋波导后的功率压缩比进行了计算和分析。计算表明:脉冲的频率调制形式对功率压缩比影响较大;相同频率调制形式下,脉冲长度越长,工作频带越宽,功率压缩比越高。为了获得尽可能高的功率压缩比,需对脉冲的频率变化方式进行调节,使其与螺旋波导色散特性匹配。同时还需要在高的功率压缩比和高的压缩效率之间做出权衡。计算得到,当注入脉冲的脉宽为40ns、工作频带为8.8~9.5GHz、频率调制形式与螺旋波导色散特性匹配时,功率压缩比达到了15,压缩效率约为40%。     

Performance Analysis and Optimization for Irreversible Combined Carnot Heat Engine Working with Ideal Quantum Gases

An irreversible combined Carnot cycle model using ideal quantum gases as a working medium was studied by using finite-time thermodynamics. The combined cycle consisted of two Carnot sub-cycles in a cascade mode. Considering thermal resistance, internal irreversibility, and heat leakage losses, the power output and thermal efficiency of the irreversible combined Carnot cycle were derived by utilizing the quantum gas state equation. The temperature effect of the working medium on power output and thermal efficiency is analyzed by numerical method, the optimal relationship between power output and thermal efficiency is solved by the Euler-Lagrange equation, and the effects of different working mediums on the optimal power and thermal efficiency performance are also focused. The results show that there is a set of working medium temperatures that makes the power output of the combined cycle be maximum. When there is no heat leakage loss in the combined cycle, all the characteristic curves of optimal power versus thermal efficiency are parabolic-like ones, and the internal irreversibility makes both power output and efficiency decrease. When there is heat leakage loss in the combined cycle, all the characteristic curves of optimal power versus thermal efficiency are loop-shaped ones, and the heat leakage loss only affects the thermal efficiency of the combined Carnot cycle. Comparing the power output of combined heat engines with four types of working mediums, the two-stage combined Carnot cycle using ideal Fermi-Bose gas as working medium obtains the highest power output.     

Exergetic efficiency optimization for an irreversible heat pump working on reversed Brayton cycle

This paper deals with the performance analysis and optimization for irreversible heat pumps working on reversed Brayton cycle with constant-temperature heat reservoirs by taking exergetic efficiency as the optimization objective combining exergy concept with finite-time thermodynamics (FTT). Exergetic efficiency is defined as the ratio of rate of exergy output to rate of exergy input of the system. The irreversibilities considered in the system include heat resistance losses in the hot- and cold-side heat exchangers and non-isentropic losses in the compression and expansion processes. The analytical formulas of the heating load, coefficient of performance (COP) and exergetic efficiency for the heat pumps are derived. The results are compared with those obtained for the traditional heating load and coefficient of performance objectives. The influences of the pressure ratio of the compressor, the allocation of heat exchanger inventory, the temperature ratio of two reservoirs, the effectiveness of the hot- and cold-side heat exchangers and regenerator, the efficiencies of the compressor and expander, the ratio of hot-side heat reservoir temperature to ambient temperature, the total heat exchanger inventory, and the heat capacity rate of the working fluid on the exergetic efficiency of the heat pumps are analysed by numerical calculations. The results show that the exergetic efficiency optimization is an important and effective criterion for the evaluation of an irreversible heat pump working on reversed Brayton cycle.     

Performance Analysis and Four-Objective Optimization of an Irreversible Rectangular Cycle

Based on the established model of the irreversible rectangular cycle in the previous literature, in this paper, finite time thermodynamics theory is applied to analyze the performance characteristics of an irreversible rectangular cycle by firstly taking power density and effective power as the objective functions. Then, four performance indicators of the cycle, that is, the thermal efficiency, dimensionless power output, dimensionless effective power, and dimensionless power density, are optimized with the cycle expansion ratio as the optimization variable by applying the nondominated sorting genetic algorithm II (NSGA-II) and considering four-objective, three-objective, and two-objective optimization combinations. Finally, optimal results are selected through three decision-making methods. The results show that although the efficiency of the irreversible rectangular cycle under the maximum power density point is less than that at the maximum power output point, the cycle under the maximum power density point can acquire a smaller size parameter. The efficiency at the maximum effective power point is always larger than that at the maximum power output point. When multi-objective optimization is performed on dimensionless power output, dimensionless effective power, and dimensionless power density, the deviation index obtained from the technique for order preference by similarity to an ideal solution (TOPSIS) decision-making method is the smallest value, which means the result is the best.     

变温热源布雷顿循环的功率密度优化

计入工质与高、低温侧换热器的热阻损失及压气机和涡轮机中的不可逆压缩和膨胀损失,用有限时间热力学方法,导出了恒温热源条件下不可逆布雷顿循环功率密度与压比间的解析式,借助于数值计算,研究了高、低温侧换热器的热导率分配和工质与热源间的热容率匹配对最大功率密度的影响。     

Performance Optimizations with Single-, Bi-, Tri-, and Quadru-Objective for Irreversible Diesel Cycle

Applying finite time thermodynamics theory and the non-dominated sorting genetic algorithm-II (NSGA-II), thermodynamic analysis and multi-objective optimization of an irreversible Diesel cycle are performed. Through numerical calculations, the impact of the cycle temperature ratio on the power density of the cycle is analyzed. The characteristic relationships among the cycle power density versus the compression ratio and thermal efficiency are obtained with three different loss issues. The thermal efficiency, the maximum specific volume (the size of the total volume of the cylinder), and the maximum pressure ratio are compared under the maximum power output and the maximum power density criteria. Using NSGA-II, single-, bi-, tri-, and quadru-objective optimizations are performed for an irreversible Diesel cycle by introducing dimensionless power output, thermal efficiency, dimensionless ecological function, and dimensionless power density as objectives, respectively. The optimal design plan is obtained by using three solution methods, that is, the linear programming technique for multidimensional analysis of preference (LINMAP), the technique for order preferences by similarity to ideal solution (TOPSIS), and Shannon entropy, to compare the results under different objective function combinations. The comparison results indicate that the deviation index of multi-objective optimization is small. When taking the dimensionless power output, dimensionless ecological function, and dimensionless power density as the objective function to perform tri-objective optimization, the LINMAP solution is used to obtain the minimum deviation index. The deviation index at this time is 0.1333, and the design scheme is closer to the ideal scheme.     

摩擦对空气标准Diesel循环功率效率特性的影响

1前言自Novikov（1957），Chambadait1957）和Curzon－Ahlborn（1975）将传热过程引入卡诺热机循环研究，开创有限时间热力学理论后，截止96年9月已有八百余篇有关文献发表，包括专著七部，有关进展见综述文献＞3I。对mesel循环的有限时间热力学分析也已取得了一些进展。Hoffman等N用最优控制理论优化Diesel循环的活塞运动规律，AIZ。nblld等和本文作者将活塞式加热气缸中活塞最优运动规律用到了内燃机循环分析中；Orlov等导出了内燃机的功率效率极限，Klein，Blank等和本文作者问考虑了传热对Diesel循环特性的影响。除了热漏（传热）…     

喷水对半闭环燃气轮机循环的影响

本文对燃气轮机的简单循环、开环和半闭环系统,分别以空气和CO2作为工质、纯氧为氧化物、天然气为燃料时的热力循环过程,在喷水及不喷水条件下,利用自行设计的分析软件进行了较为系统的数值分析和性能评估,详尽分析了喷水量对使用空气或CO2作为工质的半闭环燃气轮机循环的影响,揭示了适量喷水有助于提高循环效率和输出功率的客观规律,为研制CO2零排放的高效燃气轮机装置奠定了坚实的理论基础.     

Maximum power output of a class of irreversible non-regeneration heat engines with a non-uniform working fluid and linear phenomenological heat transfer law

Maximum power output of a class of irreversible non-regeneration heat engines with non-uniform working fluid, in which heat transfers between the working fluid and the heat reservoirs obey the linear phenomenological heat transfer law [q ∝ Δ(T ⁻¹)], are studied in this paper. Optimal control theory is used to determine the upper bounds of power of the heat engine for the lumped-parameter model and the distributed-parameter model, respectively. The results show that the maximum power output of the heat engine in the distributed-parameter model is less than or equal to that in the lumped-parameter model, which could provide more realistic guidelines for real heat engines. Analytical solutions of the maximum power output are obtained for the irreversible heat engines working between constant temperature reservoirs. For the irreversible heat engine operating between variable temperature reservoirs, a numerical example for the lumped-parameter model is provided by numerical calculation. The effects of changes of reservoir’s temperature on the maximum power of the heat engine are analyzed. The obtained results are, in addition, compared with those obtained with Newtonian heat transfer law [q ∝ Δ(T)].     

冷热联供的空气制冷不可逆循环分析

本文分析了压气机排气余热利用的冷热联供回热空气制冷不可逆循环,并建立了仅忽略系统内所有换热器流动阻力损失的循环工作性能系数(COP)计算方程式。用该方程分析研究了透平膨胀机与压气机等熵效率、压缩机排气余热度、降温比、传热温差、压比等参数对系统COP值的影响,发现膨胀透平等熵效率提高对COP值的贡献远大于压气机效率同样提高的功效;在其它参数确定时,存在最佳压比,可使系统工作性能系数在该条件下达极值。在优化参数配置下,用于空气调节的冷热联供回热空气制冷不可逆循环的COP值可达2左右。