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间隙密封技术是自由活塞斯特林发动机的一项关键技术,间隙密封避免了摩擦损耗,不需要润滑,对自由活塞斯特林发动机整机性能的提高起到了重要的作用。本文建立了自由活塞斯特林发动机间隙密封双边运动的一维层流模型,结合施密特等温分析法,对一台输出功率为100 W的自由活塞斯特林发动机计算了工作腔与缓冲腔之间的泄漏率曲线和单个循环工作腔向缓冲腔泄漏的泄漏量,并比较了不同间隙宽度情况下泄漏损失所占的比重,得到了最大允许的密封间隙宽度。同时,建立带有进出口的二维模型,运用Fluent进行了数值模拟,并与一维层流模型计算结果进行对比,得出二者泄漏率基本一致的结果,但由于间隙流动处进出口体积骤变的存在,二维模型数值模拟结果泄漏率略低于一维层流模型,更接近实际情况。 相似文献
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《真空与低温》2019,(4)
以自由活塞斯特林发动机为研究对象,采用响应面优化法(RSM)研究各因素及其交互作用对响应值的影响规律。以输出功率和热效率作为响应值,选取活塞杆直径、加热器、回热器以及冷却器长度作为因变量,建立了二次回归模型。通过对回归方程的ANOVA分析和模型诊断,检验因变参数对斯特林发动机性能是否具有显著影响。此外,利用RSM的二维等高线图和三维表面图,揭示了斯特林发动机输出功率、热效率与各因素之间的相互作用关系。结果显示:发动机输出功率随加热器、回热器以及冷却器长度的增加而降低,而热效率随加热器和回热器长度的增加而增加,随冷却器的变化有最佳值。因此,需综合考虑各因素的影响关系再选取合适的结构参数。 相似文献
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《制冷与空调(北京)》2020,(9)
建立了冷藏车余热驱动型跨临界有机朗肯-制冷循环系统热力学计算模型,研究了R1234ze(E)在该循环系统中运行性能,系统地分析了冷凝温度为40℃、50℃、60℃时系统运行性能参数,得到冷凝温度为40℃时,对应发动机尾气温度约为140℃时,系统拥有最高的膨胀机做功量10.20 kW;对应发动机尾气温度约为165℃,系统拥有最优的TORC系统热效率9.49%和最大的TORC-制冷循环系统制冷量18.36kW以及最佳的热效率值19.12%。 相似文献
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利用LNG冷能具有较好的节能潜力和经济效益,通过流程的创新设计,提出了一种将LNG冷能用于燃气轮机和斯特林发动机的联合系统。基于热力学第一、第二定律,对联合系统进行热力学分析,结果表明:在环境温度35℃条件下,联合系统的输出功率为5715.48kW,热效率为31.62%,效率为43.65%;相比燃气轮机系统和直接冷却进气系统,联合系统的输出功率分别提高了7.84%和0.78%,热效率分别提高了3.16%和1.18%,效率分别提高了4.23%和1.63%。联合系统在不同环境温度下,可将燃气轮机的进气温度降低10℃左右,系统的输出功率和效率随着进气温度的降低均有所提高。 相似文献
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航空发动机材料的现状和发展 总被引:1,自引:1,他引:0
航空发动机实际上是一种产生强大推力的高温气体发生器,它把燃油中的热能转变为机械能和电能,并使气体加热膨胀,产生强大的动力。 作为航空用途,对于发动机的重量及飞行阻力还有更高的要求,因此,常用推重比以及推力和迎风面积比来衡量发动机性能的优劣。而对于发动机材料,不仅要求具有所必须的成分和力学性能,而且要求在燃油燃气腐蚀环境中具有足够的可靠性。 新型航空发动机设计时的要求,仍然是功率大,油耗少,成本低,工艺性好等。为了满足这些要求,增大推重比以及推力迎风面积比便是至关重要的。降低成本的关键在于延长发动机的使用寿命,而降低油耗,增大推重比的途径为简化压气机,减少级数,加大负载,提高温度,最终是提高发动机的热效率。 提高发动机热效率的办法是提高空气压缩比和提高涡轮进气温度。图1a为空气压缩比和涡轮进气温度对发动机热效率的关系曲线。 相似文献
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A Stirling engine is a thermal system that may be used to produce power from a high temperature heat source or as a refrigerator and heat pump to deliver energy at a higher temperature than abstracted from the source. A Stirling engine may therefore be used as the driver for natural gas heated air conditioning/heat pump Rankine cycle vapour compression systems or itself be used as the refrigerating/heat pump system requiring an input of work. Two Stirling systems, one acting as the driver, the other as the heat pump may be combined into the Stirling-Stirling or duplex Stirling arrangement. This paper touches briefly on a number of topics about fundamental aspects and recent developments in this field. 相似文献
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A Stirling cycle cooling engine operates on a closed regenerative thermodynamic cycle with compression and expansion of the working fluid at different temperature levels. Conventional engines use a gaseous working fluid but a significant improvement in refrigerating capacity may be gained with a two-phase, two-component working fluid. This consists of a gaseous carrier and a component which is liquid in the cold region and gaseous in the ambient temperature spaces with the phase change occurring during the regenerative process. This causes an increase in the range of the pressure excursion of the working fluid and consequently increases the refrigerating capacity with no penalties in terms of size, weight, or cost. The degree of improvement depends on the particular design and operating conditions of the engine. The effects of variation of some of these parameters are explored. 相似文献
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R. Salzbrenner 《Journal of Materials Science》1984,19(6):1827-1835
The mechanical shape memory effect associated with a thermoelastic martensitic transformation can be used to convert heat directly into mechanical work. Laboratory simulation of two types of heat engine cycles (Stirling and Ericsson) has been performed to measure the amount of work available per cycle in a Ni-45 at% Ti alloy. Tensile deformations at ambient temperature induced martensite, while a subsequent increase in temperature, caused a reversion to the parent phase during which a load was carried through the strain recovery, i.e. work was accomplished. The amount of heat necessary to carry the engines through a cycle was estimated from calorimeter measurements and the work performed per cycle. The measured efficiency of the system tested reached a maximum of 1.4% which was well below the theoretical (Carnot) maximum efficiency of 35.6%. 相似文献
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This communication presents the thermoeconomic optimization of an irreversible Stirling cryogenic refrigerator cycle. The external irreversibility is due to finite temperature difference between the working fluid and the external reservoirs while the internal irreversibility is due to the regenerative heat loss. The thermoeconomic function is defined as the cooling load divided by the total cost of the system plus the running cost. The thermoeconomic function is optimized with respect to the working fluid temperatures and the values for various parameters at the optimal operating condition are calculated. The effects of different operating parameters on the performance of the cycle have been studied. It is found that the effect of regenerative effectiveness is more than those of the other parameters on all the performance parameters of the cycle, for the same set of operating condition. 相似文献
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The performance of a small thermoacoustic Stirling heat engine (TASHE) was investigated with three kinds of working gases experimentally and numerically. The examined performances focused on the operating frequency, onset temperature, pressure amplitude and some temperature characteristics after onset. The working frequency with nitrogen, argon and helium as the working gas was 45 Hz, 42 Hz and 130 Hz, respectively. The engine worked with helium in a much wider range of mean pressure than with nitrogen and argon. There was an optimal mean pressure for the minimum onset temperature for each working media. Using nitrogen and argon as working gas rather than helium, another optimal mean pressure for the highest pressure ratio was obtained in the experiment. The loop dimension was indispensable in determining the frequency and the highest pressure ratio was observed in the resonator cavity. 相似文献
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A thermodynamic model based on exergy flow through a Stirling Refrigerator is developed. Important irreversibilities of the refrigerator due to external heat transfer with the reservoirs, heat leak, flow and heat transfer in regenerator are included in the model. Expansion and compression efficiencies are introduced in the model to account for the losses in these processes. The effect of a control phase shift between the mass flow rate and pressure across regenerator on the performance of the refrigerator is presented. Analytical solutions representing important quantities in the design of Stirling refrigerators such as the load curve, cooling power and efficiency in terms of basic system input parameters are developed. Thermodynamic bounds for the performance of Stirling refrigerators are obtained. Results indicating a compromise between cooling power and efficiency that are dependent on the constraint of the system are presented and discussed. 相似文献
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Edwin Geo Varuvel Nadia Mrad Fethi Aloui Mohand Tazerout 《Clean Technologies and Environmental Policy》2017,19(4):1099-1108
In the present work, biofuel derived from industrial fish processing industry waste is used in diesel engines to study its suitability . Biofuel from industry fish waste is produced through catalytic cracking, and its quality has been improved through distillation. A single cylinder 4.5 kW at 1500 rpm was used to find the suitability of biofuel and undistilled biofuel in diesel engine. Experimental results show that the brake thermal efficiency of biofuel and undistilled biofuel is similar. Brake thermal efficiency for diesel, undistilled biofuel and biofuel is 29.98, 32.12 and 32.4%, respectively, at 80% load. Carbon monoxide, unburnt hydrocarbons, particulate matter and oxides of nitrogen emissions increase with undistilled biofuel compared to biofuel. There is a small reduction in carbon dioxide emission with undistilled biofuel compared to biofuel. Even though the cylinder pressure is high with undistilled biofuel, the intensity of premixed combustion is lower than distilled biofuel. The ignition delay and combustion duration increase with undistilled biofuel. Finally, it is concluded that the fuel derived from fish processing industry waste can be used as a fuel for diesel engine after distillation. 相似文献
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回热损失对磁斯特林制冷循环制冷率的影响 总被引:7,自引:0,他引:7
从铁磁质的磁化强度一般表示式出发,探讨热阻和回热损失对磁斯特林制冷循环性能的影响,导出最大制冷率及其它性能参数。得到了结果适用于以顺磁质为工质的磁斯特林制冷循环。并指出在理想回热条件下的结论也适用于磁卡诺制冷循环。 相似文献