具有热阻、热漏和回热损失的不可逆斯特林循环生态学性能系数优化分析研究

利用有限时间热力学分析了具有热阻、热漏和回热损失的不可逆斯特林循环生态学经济性能优化ECOP评判标准,推导了不可逆斯特林循环关于功率输出、效率、经济学函数和ECOP优化分析的数学表达式,利用数字分析以及热漏、回热时间和回热器效率研究上述参数之间的相互关系.研究结果表明:在最大ECOP工作条件下工作的斯特林循环比在最大生...     

燃气-蒸汽联合循环的生态学优化

建立了具有热阻、热漏的定常流布雷顿一朗肯联合循环模型,分析了联合循环功率、效率和生态学指标性能,并对其进行了优化;通过数值计算分析了功率、效率和生态学之间的优化关系,并讨论了热漏对联合循环优化性能的影响.结果表明:最大生态学指标下的效率十分接近联合循环可达到的最大效率,布雷顿一朗肯循环是燃气一蒸汽联合循环的一个特例.分析研究结果为燃气一蒸汽联合循环热机的设计提供了一定的依据.     

线性唯象传热下的斯特林制冷机的Ω函数优化

以线性唯象传热规律为基础,建立了不可逆斯特林制冷机的相关模型,结合热阻、热漏、回热损失等一些不可逆因素,将能使性能系数和制冷率达到平衡的Ω函数作为目标,对斯特林制冷机进行有限时间热力学优化。数值计算的结果表明:不可逆因素A1和热漏越小,Ω函数所取得的极值越大。在温比相同的条件下,制冷率和性能系数不能在同一工况下取得最大值,故而通过协调优化,使Ω函数在某一工况下存在极大值,进而实现制冷循环性能最佳,并最终对实际斯特林制冷机的发展和改进提供理论指导意义。     

广义不可逆布雷逊热机的生态学性能优化

应用有限时间热力学方法和生态学优化准则对不可逆布雷逊热机循环的各种性能参数进行优化,导出了服从牛顿传热规律并考虑热阻、热漏和内不可逆性的布雷逊热机循环在生态学目标函数最大时输出功率和效率的表达式。讨论了热漏、内不可逆性对该热机各种性能参数的影响,同时还比较了最大输出功率和最大生态学目标函数下该热机各种优化性能参数间的关系。所得结果给实际热机的优化设计提供了理论依据。     

不可逆变温热源斯特林热机的?生态学性能研究

基于?的生态学目标函数,使用一种新的指标——?生态指标对不可逆变温热源斯特林热机进行了分析。在热机高低温热源的热容均为有限的前提下,考虑斯特林热机的热阻、回热损失、内不可逆性以及热漏对其影响。研究了回热器的回热效率和高低温热源的热容的比值等参数对斯特林热机的功率、效率和?生态学指标的影响,并将结果与另一种生态目标函数的结果进行了比较,得到最佳功率输出功率和热效率。     

内可逆四热源吸收式制冷机生态学最优性能

基于能量分析的观点,建立了反映四热源吸收式制冷机制冷率与熵产率之间最佳折中的生态学准则,分析了线性(牛顿)传热定律下内可逆四热源吸收式制冷机的生态学最优性能.导出了生态学目标与制冷系数的优化关系和最大生态学目标值及其相对应的制冷系数、制冷率和熵产率,确定了循环主要参数的生态学优化选择范围.数值算例分析了制冷率目标和生态学目标的相互关系,计算表明生态学准则对吸收式制冷机优化设计是一种具有长期效应的可选优化目标.     

具有热阻、热漏的不可逆布雷森循环生态学性能新析

以反映热机循环输出火用和火用损失之比的生态学性能系数为目标,用有限时间热力学的方法分析具有热阻、热漏的不可逆布雷森循环性能.导出了在牛顿传热律下布雷森循环无因次功率、效率、无因次熵产率和生态学性能系数的解析式;并通过数值算例得到它们之间的关系.结果表明:对比生态学目标E,循环在最大生态学性能系数ECOP下工作时,其相应的熵产率和热效率有明显优势.     

内可逆四热源吸收式热泵生态学最优性能

基于能量分析的观点,建立了反映四热源吸收式热泵泵热率与熵产率之间最佳折衷的生态学准则,分析了线性(牛顿)传热定律下内可逆四热源吸收式热泵的生态学最优性能,导出了生态学目标与泵热系数的优化关系和最大生态学目标值及其相对应的泵热系数、泵热率和熵产率,确定了循环主要参数的生态学优化选择范围。数值算例分析了泵热率目标和生态学目标的相互关系,计算表明生态学准则对吸收式热泵优化设计是一种具有长期效应的可选优化目标。     

广义不可逆卡诺热机的生态学最优性能

以反映热机功率与熵产率之间最佳折衷的“生态学”准则为目标，综合考虑热阻、热漏及其它不可逆性对卡诺热机性能的影响，导出牛顿传热规律下循环的生态学最优性能，由数值计算分析比较了热漏、内不可逆性的影响特点。生态学优化以牺牲小部分输出功率为代价，较大地降低了循环的熵产率，而且在一定程度上提高了热机效率。因此，生态学目标函数不仅反映了输出功率和熵产率之间的最佳折衷，而且反映了输出功率和热效率之间的最佳折衷。     

内可逆四热源吸收式热变换器生态学最优性能

基于能量分析的观点，建立了反映四热源吸收式热变换器泵热率与熵产率之间最佳折衷的生态学准则。导出了线性(牛顿)传热定律下生态学目标与泵热系数的优化关系、最大生态学目标值及其相对应的泵热系数、泵热率和熵产率以及最大泵热率时的生态学目标和熵产率。通过数值算例分析得到了吸收式热变换器的生态学优化准则。计算发现，与最大泵热率目标相比，最大生态学目标牺牲了27．3％的泵热率。使循环熵产率降低了77．0％。泵热系数增加了55．4％，表明生态学准则对吸收式热变换器优化设计是一种具有长期效应的可选优化目标。     

Performance of a twin power piston low temperature differential Stirling engine powered by a solar simulator

This paper provides an experimental investigation on the performance of a low-temperature differential Stirling engine. In this study, a twin power piston, gamma-configuration, low-temperature differential Stirling engine is tested with non-pressurized air by using a solar simulator as a heat source. The engine testing is performed with four different simulated solar intensities. Variations of engine torque, shaft power and brake thermal efficiency with engine speed and engine performance at various heat inputs are presented. The Beale number, obtained from the testing of the engine, is also investigated. The results indicate that at the maximum simulated solar intensity of 7145 W/m², or heat input of 261.9 J/s, with a heater temperature of 436 K, the engine produces a maximum torque of 0.352 N m at 23.8 rpm, a maximum shaft power of 1.69 W at 52.1 rpm, and a maximum brake thermal efficiency of 0.645% at 52.1 rpm, approximately.     

有限速率过程对活塞式斯特林发动机性能的影响

本文讨论在给定热源温度和压缩比的情况下,过程进行的速率有限,并受热传导不可逆影响的内可逆活塞式斯特林发动机的最优性能,导出以理想气体或范德瓦尔斯气体为工质的斯特林发动机的最大输出功率与热效率的关系,以及最大热效率与输出功率的关系,并推出了一些新的有限时间热力学的性能界限。     

Mobile hydraulic power supply: Liquid piston Stirling engine pump

Conventional mobile hydraulic power supplies involve numerous kinematic connections and are limited by the efficiency, noise, and emissions of internal combustion engines. The Stirling cycle possesses numerous benefits such as the ability to operate from any heat source, quiet operation, and high theoretical efficiency. The Stirling engine has seen limited success due to poor heat transfer in the working chambers, difficulty sealing low-molecular weight gases at high pressure, and non-ideal piston displacement profiles. As a solution to these limitations, a liquid piston Stirling engine pump is proposed. The liquid pistons conform to irregular volumes, allowing increased heat transfer through geometry features on the interior of the working chambers. Creating near-isothermal operation eliminates the costly external heat exchangers and increases the engine efficiency through decreasing the engine dead space. The liquid pistons provide a positive gas seal and thermal transport to the working chambers. Controlling the flow of the liquid pistons with valves enables matching the ideal Stirling cycle and creates a direct hydraulic power supply. Using liquid hydrogen as a fuel source allows cooling the compression side of the engine before expanded the fuel into a gas and combusting it to heat the expansion side of the engine. Cooling the compression side not only increases the engine power, but also significantly increases the potential thermal efficiency of the engine. A high efficiency Stirling engine makes energy regeneration through reversing the Stirling cycle practical. When used for regeneration, the captured energy can be stored in thermal batteries, such as a molten salt. The liquid piston Stirling engine pump requires further research in numerous areas such as understanding the behavior of the liquid pistons, modeling and optimization of a full engine pump, and careful selection of materials for the extreme operating temperatures. Addressing these obtainable research quandaries will enable a transformative Stirling engine pump with the potential to excel in numerous applications.     

The impact of heat exchanger fouling on the optimum operation and maintenance of the Stirling engine

This paper focuses on the effect of heat exchanger fouling on the performance of the Stirling engine in combined heat and power (CHP) application. Fouling results from using biomass fuels and affects the heat exchanger that transfers heat into the engine. This heat exchanger is referred to as the heater. The heat exchanger that recovers heat from the flue gases is also affected by fouling. To determine the performance of the Stirling engine, a commercial Stirling analysis tool is applied together with models that have been developed for the heat transfer in the heater, regenerator and cooler of the engine. The Stirling engine model uses constant temperatures for the heat addition and rejection, with the theory of displacement engine as a basis. The fouling in the heat exchanger is taken into account by using a fouling factor that corresponds with the degradation in the total heat transfer coefficient. The Stirling engine model together with the model for heat exchanger fouling makes it possible to estimate the effect of fouling on the performance of the Stirling engine. A cost model is developed for the engine to translate changes in performance into economy in CHP operation. In the studied application, the Stirling engine is operated by the heat demand. Together with the selected control method, performance and cost models compose a tool for the simulation and optimization of the system. The use of the models to determine the optimal cleaning interval of the heat exchanger surfaces is considered.     

Thermodynamic optimization of Stirling heat engine with methane gas using finite speed thermodynamic model

With the daily rise in environmental issues due to the use of conventional fuels, researchers are motivated to use renewable energy sources. One of such waste heat and low-temperature differential driven energy sources is the Stirling engine. The performance of the Stirling engine can be improved by finding out the optimum operating and geometrical parameters with suitable working gas and thermal model. Based on this motivation, the current work focuses on the multiobjective optimization of the Stirling engine using the finite speed thermodynamic model and methane gas as the working fluid. Considering output power and pressure drop as two objective functions, the system is optimized using 11 geometrical and thermal design parameters. The optimization results are obtained in the form of the Pareto frontier. A sensitivity assessment is carried out to observe the decision variables, which are having a more sensitive effect on the optimization objectives. Optimization results reveal that 99.83% change in power output and 78% change in total pressure drop can take place in the two-dimensional optimization space. The optimal solution closest to the ideal solution has output power and pressure drop values as 12.31 kW and 22.76 kPa, respectively.     

A four power-piston low-temperature differential Stirling engine using simulated solar energy as a heat source

In this paper, the performances of a four power-piston, gamma-configuration, low-temperature differential Stirling engine are presented. The engine is tested with air at atmospheric pressure by using a solar simulator with four different solar intensities as a heat source. Variations in engine torque, shaft power and brake thermal efficiency with engine speed and engine performance at various heat inputs are presented. The Beale number obtained from the testing of the engine is also investigated. The results indicate that at the maximum actual energy input of 1378 W and a heater temperature of 439 K, the engine approximately produces a maximum torque of 2.91 N m, a maximum shaft power of 6.1 W, and a maximum brake thermal efficiency of 0.44% at 20 rpm.     

Multi-objective optimization for GPU3 Stirling engine by combining multi-objective algorithms

Stirling engine has become preferable for high attention towards the use of alternate renewable energy resources like biomass and solar energy. Stirling engine is the main component of dish Stirling system in thermal power generation sector. Stirling engine is an externally heating engine, which theoretical efficiency is as high as Carnot cycle's, but actual ones are always far below compared with the Carnot efficiency. A number of studies have been done on multi-objective optimization to improve the design of Stirling engine. In the current study, a multi-objective optimization method, which is a combination of multiple optimization algorithms including differential evolution, genetic algorithm and adaptive simulated annealing, was proposed. This method is an attempt to generalize and improve the robustness and diversity with above three kinds of population based meta-heuristic optimization techniques. The analogous interpreter was linked and interchanged to find the best global optimal solution for Stirling engine performance optimization. It decreases the chance of convergence at a local minimum by powering from the fact that these three algorithms run parallel and members from each population and technique are swapped. The optimization considers five decision variables, including engine frequency, mean effective pressure, temperature of heating source, number of wires in regenerator matrix, and the wire diameter of regenerator, as multiple objectives. The Pareto optimal frontier was obtained and a final optimal solution was also selected by using various multi-criteria decision making methods including techniques for Order of Preference by Similarity to Ideal Solution and Simple Additive Weighting. The multi-objective optimization indicated a way for GPU-3 Stirling engine to obtain an output power of more than 3 kW and an increase by 5% in thermal efficiency with significant decrease in power loss due to flow resistance.     

Using supercritical heat recovery process in Stirling engines for high thermal efficiency

Stirling engine, using a composite working fluid, such as two-component fluid: gaseous carrier and phase-change component and single multi-phase fluid as the working fluid is studied to get high thermal efficiency. In Stirling engine with a composite fluid, a thermodynamic supercritical heat recovery and heating process is proposed and demonstrated to improve the heat transfer of the heat regenerator and cooler of common gaseous Stirling engine. The criteria for the choice of the working fluids are also formulated.     

Efficiency bound of a solar-driven stirling heat engine system

A solar-driven Stirling engine is modelled as a combined system which consists of a solar collector and a Stirling engine. The performance of the system is investigated, based on the linearized heat loss model of the solar collector and the irreverisible cycle model of the Stirling engine affected by finite-rate heat transfer and regenerative losses. The maximum efficiency of the system and the optimal operating temperature of the solar collector are determined. Moreover, it is pointed out that the investigation method in the present paper is valid for other heat loss models of the solar collector as well, and the results obtained are also valid for a solar-driven Ericsson engine system using an ideal gas as its engine work substance. © 1998 John Wiley & Sons, Ltd.     

有限热源斯特林热机的优化性能研究

应用有限时间热力学方法,探索有限热源、热阻和回热损失的斯特林热机的优化性能,得到一些新的性能参数,所得结论可为斯特林热机的研制和优化设计提供些新理论指导。