微型脉冲式回热器的试验方法和换热效率影响因素研究

发布时间：2018-06-13 06:54

  本文选题：微型摆式发动机 + 回热器　； 参考：《南京航空航天大学》2016年硕士论文

【摘要】：为了满足便携式电子产品越来越大的用电需求,采用碳氢燃料的微动力发电装置因其在能量转化方面的巨大优势,迅速成为新一代便携式电源的发展趋势。微型摆式发动机具有便于微型化,能量密度高的特点,是未来便携式电源的发展趋势之一,但由于发动机尾气带走了燃烧产生的大部分热量,其热效率低下,为此引入回热技术对提升发动机性能十分必要。适用于微型摆式发动机的回热器具有冷热气流量小,脉冲特性明显的特点,与常规回热器工作流动形式差异明显。本文为对微型脉冲式回热器进行试验研究,设计了微型脉冲式回热器试验台,并对回热器换热效率影响因素进行了试验和数值模拟研究。本文首先对加装微型回热器后的微型摆式发动机运行困难的问题进行分析,改进发动机结构,并采用混合动力循环驱动发动机正常运行。分析发动机工作循环,获得回热器冷热气真实流动情况。模拟回热器冷热气进出口条件,设计试验台及试验测量方案。查阅文献可知,微型化后发动机内泄漏对发动机影响较大。建立发动机内泄漏数学模型,对发动机内泄漏进行分析,并设计试验台封严手段,研究结果表明:由于尺寸微小化,样机内泄漏流质量占到样机内气体总质量的大部分;通过改变泄漏缝隙尺寸和样机运行频率可抑制有效样机内泄漏;提出了一种新型逆向射流式多级凹槽封严技术,通过数值计算,验证其封严效果较好,可抑制泄漏流量达到12%以上。对回热器换热效率的影响因素冷气单次进气量和脉冲频率进行了数值模拟研究,结果发现:由于冷气单次进气量和脉冲频率变化对回热器内流场的影响,导致回热器冷气对流换热能力增强,使得回热器换热效率虽然由于冷气需吸收的热量增加和换热时间较少的原因出现下降,但下降幅度不大。同时发现回热器换热效率较定常流动时降低,造成这种变化的原因为微型化后,脉冲效应引起的回热器内沿换热间壁的轴向导热引起的。接着对回热器换热效率的影响因素进行试验研究。目前试验台目前工作频率可达25Hz,热气温度可上升至700℃。在试验台调试阶段发现脉冲流发生器内泄漏严重,增压较低,验证了泄漏问题的严重影响,并验证了运行频率对泄漏的抑制。采用油脂密封和篦齿封严应用于试验台,从试验数据来看,油脂密封能够获得较好的密封效果,可应用于试验台上;篦齿封严技术可一定程度上抑制泄漏流,但目前效果不明显。进行了微型脉冲式回热器换热效率试验,试验中由于散热和试验管路导热的原因,导致测量得到的换热效率较低,考虑两者影响后,试验换热效率达到60%左右,通过分析,符合预期效果,且试验规律验证了数值模拟结果。
[Abstract]:In order to meet the increasing demand of portable electronic products, the new generation of portable power supply is rapidly becoming the development trend of the new generation portable power supply because of its great advantage in energy conversion. Micro pendulum engine is one of the development trends of portable power supply in the future because of its convenience for miniaturization and high energy density. However, because engine exhaust takes away most of the heat produced by combustion, its thermal efficiency is low. Therefore, it is necessary to introduce regenerative technology to improve engine performance. The recuperator suitable for micro pendulum engine has the characteristics of low flow rate of cold and hot air and obvious pulse characteristics, which is different from the working flow form of conventional recuperator. In this paper, in order to study the miniature pulse regenerator, a miniature pulse regenerator test-bed is designed, and the factors affecting the heat transfer efficiency of the regenerator are studied by experiment and numerical simulation. In this paper, the difficulty of the micro pendulum engine with micro regenerator is analyzed, the engine structure is improved, and the hybrid cycle drive engine is used to run normally. The real flow of hot and cold gas in the regenerator is obtained by analyzing the engine working cycle. Simulates the inlet and outlet condition of the regenerator, designs the test bed and the test measurement scheme. It can be seen from the literature that the internal leakage of the engine after miniaturization has a great influence on the engine. The mathematical model of engine internal leakage is established, the internal leakage of engine is analyzed, and the sealing method of test bed is designed. The results show that the mass of leakage flow in the prototype accounts for the majority of the total mass of gas in the prototype because of the miniaturization of the size; The leakage in the prototype can be restrained by changing the leak slot size and the operating frequency of the prototype, and a new type of reverse jet multistage groove sealing technology is proposed. The numerical results show that the sealing effect is good. The leakage rate can be restrained by more than 12%. The factors affecting the heat transfer efficiency of the regenerator are numerically simulated. The results show that the flow field in the regenerator is affected by the variation of the single air intake and the pulse frequency. As a result, the convection heat transfer capacity of the regenerator is enhanced, and the heat transfer efficiency of the regenerator is reduced because of the increase of the heat absorbed by the air conditioner and the decrease of the heat transfer time, but the decrease is not significant. At the same time, it is found that the heat transfer efficiency of the regenerator is lower than that of the steady flow, which is caused by the axial heat conduction of the inner wall of the regenerator caused by the pulse effect after miniaturization. Then the factors affecting the heat transfer efficiency of the regenerator are studied experimentally. At present, the operating frequency of the test bed can reach 25 Hz, and the hot gas temperature can rise to 700 鈩，

本文编号：2013129