不同优化准则下斯特林发动机的性能分析

应用有限时间热力学原理.建立了一个考虑热阻、热漏和回热损失等不可逆因素的斯特林发动机模型;推导了最大输出功率、最大效率和生态学优化准则下,斯特林发动机性能的表达式;比较了三种优化准则下,热漏系数和回热器有效性对斯特林发动机性能的影响.研究表明:对热漏损失和回热损失较大的斯特林发动机,宜选用生态学优化准则.为斯特林发动机...     

自由活塞式斯特林发动机的性能优化

以Simple分析法为基础,扩展针对自由活塞式斯特林发动机的分析软件,研究各项设计参数对自由活塞式斯特林发动机性能的影响,并对各项设计参数进行优化。结果表明:发动机性能随回热器孔隙率和相位角的变化有最佳值,而随系统平均压力和频率的增加而增加;当加热器和冷却器长径比(L/g)大于10时,环形间隙(g)越小,发动机输出功率与热效率越高;发动机输出功率随回热器长径比的增加而减小,热效率随回热器长径比的增加而增加;而发动机性能随加热器与冷却器长径比的变化有最佳值。     

一种β型三曲拐斯特林发动机的建模与仿真

斯特林发动机作为一种外部燃烧的发动机,具有燃料来源广、污染小、噪声低和维修方便等优点,对节能与环保具有积极的意义,而其中的β型斯特林发动机更是具有体积小、传动平稳、易于密封等优点,具有广泛的应用前景。本文针对一款β型三曲拐闭式循环斯特林发动机,进行了工作过程数学建模、运用simulink软件进行仿真,根据仿真与分析结果,得到了不同气体工质功率输出与热效率随转速变化的规律。结果表明,在斯特林发动机不同转速运行范围内,应采用不同的气体作为工质,才能获得较高的功率输出与热效率。     

在近实际条件下斯特林发动机效率研究

正据《Энергетцка》2013年5-6月刊报道,亚美尼亚国立工程大学的学者研究了斯特林发动机近实际条件下的效率,并尝试考虑与热交换有限值有关的热量回收损失。在工质为范德华尔斯气体的条件下,得到在无回热器和有回热器情况下斯特林发动机的绝对内效率。结果表明,在考虑分子体积情况下,斯特林发动机的热效率取决于工质的克分子数并且比理想气体稍有增加。同时,考虑了斯特林发动机在热量与回收情况下的运行热损失,得到了回热度与热交换时间的相互关系。     

新世纪的发动机——没有运动件的发动机热声斯特林发动机简介

1979年Ceperley首先提出热声斯特林发动机的设想,但是他做的模型未能运转。其后的热声发动机(又称热声热机)采用不可逆驻波热声循环,热效率较低。1999年5月,“NATURE”刊载美国能源部LosAlamos国家试验室科学家S.Backhaus和G.Swift的文章:“热声斯特林热发动机(AthermoacousticStirlingHeatEngine)”,采用可逆斯特林循环热声热机,使热效率大大提高。热声斯特林发动机被认为是21世纪的发动机,将有可能替代传统的发动机——内燃机。国外许多刊物的“未来的发动机”、“没有运动件的发动机”、“无活塞热气机——热声发展的方向”等为题…     

斯特林发动机瞬态模型及特性分析

为获得斯特林发动机的动态特性和优化方案,将损失机制和压力梯度耦合进控制方程中,提出一维瞬态斯特林循环分析模型及分析方法,并针对GPU-3斯特林发动机进行模型验证和特性分析.模型的指示功率相对误差平均值约为4.8％,热效率的相对误差小于1％.当氦气工质在热源温度为977 K、平均压强为2.76 MPa时,输出功率随转速的...     

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。     

考虑热阻时发动机理论循环分析

根据发动机仅考虑热阻时,其混合加热循环的有限时间热力学模型,建立了发动机输出功率,热效率与循环参数εｃ,λｐ,ρｏ之间的函数关系,并依此对某实际柴油机进行了计算。计算结果表明,有限时间热力学较之传统热力学更深刻地反映发动机的实际循环。     

斯特林热机膨胀腔与压缩腔的容积匹配研究

基于斯特林绝热模型对α型斯特林热机运行状况进行数值模拟,通过对热机各部件间的质量与功量传输的计算,模拟振荡流体对热机运行的影响。同时在不同工况下探讨斯特林热机膨胀腔与压缩腔的容积比对热机效率的影响,获得最大热效率,为斯特林热机的优化设计提供思路。     

回热器增压腔对斯特林发动机性能影响的研究

建立了回热器碰撞射流数值计算模型,开展了回热器三维仿真分析;研究了增压腔对回热器基体内流场的影响规律,并分析了其对斯特林发动机性能的影响。以某型号斯特林发动机为对象,对仿真结果进行的试验验证表明:仿真结果和试验结果吻合性较好,研究结果可供斯特林发动机性能改进做参考。     

Optimization of Output Power and Thermal Efficiency of Solar‐Dish Stirling Engine Using Finite Time Thermodynamic Analysis

This paper presents an investigation on finite time thermodynamic (FTT) evaluation of a solar‐dish Stirling heat engine. FTTs has been applied to determine the output power and the corresponding thermal efficiency, exergetic efficiency, and the rate of entropy generation of a solar Stirling system with a finite rate of heat transfer, regenerative heat loss, conductive thermal bridging loss, and finite regeneration process time. Further imperfect performance of the dish collector and convective/radiative heat transfer mechanisms in the hot end as well as the convective heat transfer in the heat sink of the engine are considered in the developed model. The output power of the engine is maximized while the highest temperature of the engine is considered as a design parameter. In addition, thermal efficiency, exergetic efficiency, and the rate of entropy generation corresponding to the optimum value of the output power is evaluated. Results imply that the optimized absorber temperature is some where between 850 K and 1000 K. Sensitivity of results against variations of the system parameters are studied in detail. The present analysis provides a good theoretical guidance for the designing of dish collectors and operating the Stirling heat engine system.     

Finite time thermodynamic evaluation of endoreversible Stirling heat engine at maximum power conditions

Maximum power and efficiency at the maximum power point of an endoreversible Stirling heat engine with finite heat capacitance rate of external fluids in the heat source/sink reservoirs with regenerative losses are treated. It was found that the thermal efficiency depends on the regenerator effectiveness and the internal irreversibility resulting from the working fluid for a given value of reservoir temperature. It was also concluded that it is desirable to have larger heat capacity of the heat sink in comparison to the heat source reservoir for higher maximum power output and lower heat input.     

Optimal regenerator performance in Stirling engines

The key component of a Stirling engine is its regenerative heat exchanger. This device is subject to losses due to dissipation arising from the flow through the regenerator as well as due to imperfect heat transfer between the regenerator material and the gas. The magnitudes of these losses are characterized by the Stanton number St and the Fanning friction factor f, respectively. Using available data for the ratio St/f, results are found for the Carnot efficiency and the power output of the regenerator. They depend on the conductance and on the ratio of pressures at the two sides of the regenerator. Optimum results for efficiency and power output of the regenerator are derived in the limit of zero Mach number. The results are applied to the Stirling engine. The efficiency and the power output of the engine are found for given amplitude of the compression piston. Optimization with respect to regenerator conductance and piston phase angle leads to a maximum possible value of the power output. Under optimal conditions, the Carnot efficiency just below this maximum is close to 100%. Copyright © 2009 John Wiley & Sons, Ltd.     

Application of the multi-objective optimization method for designing a powered Stirling heat engine: Design with maximized power,thermal efficiency and minimized pressure loss

In the recent years, numerous studies have been done on Stirling cycle and Stirling engine which have been resulted in different output power and engine thermal efficiency analyses. Finite speed thermodynamic analysis is one of the most prominent ways which considers external irreversibilities. In the present study, output power and engine thermal efficiency are optimized and total pressure losses are minimized using NSGA algorithm and finite speed thermodynamic analysis. The results are successfully verified against experimental data.     

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.     

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.     

Optimum absorber temperature of a once-reflecting full conical concentrator of a low temperature differential Stirling engine

This paper provides a theoretical investigation on the optimum absorber temperature of a once-reflecting full conical concentrator for maximizing overall efficiency of a solar-powered low temperature differential Stirling engine. A mathematical model for the overall efficiency of the solar-powered Stirling engine is developed. The optimum absorber temperature for maximum overall efficiency for both limiting conditions of maximum possible engine efficiency and maximum possible engine power output is determined. The results indicated that the optimum absorber temperatures calculated from these two limiting cases are not significantly different. For a given concentrated solar intensity, the maximum overall efficiency characterized by the condition of maximum possible engine power output is very close to that of the real engine of 55% Carnot efficiency, approximately.     

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.     

以Dieterici气体为工质的两类热机循环性能分析

对Dieterici实际气体作了简要分析,并以Dieterici实际气体为工质,分别导出卡诺热机和斯特林热机的输出功和效率的一般表达式.最后通过数值计算,讨论了卡诺热机及斯特林热机的输出功和效率分别与体积和温度之间的关系.所得结论可为热机的运行条件和优化设计提供理论参考.