文本描述
全球能源短缺问题随着汽车工业的发展而日趋严重,如何利用汽车尾气余热能量 也愈发引起研究人员的兴趣。斯特林发动机作为节能装置,具有燃料广泛、转换效率 高、噪音低等优点。国内外许多学者对其在汽车尾气能量的回收上展开了研究。而应 用斯特林发动机来回收汽车尾气能量,在解决能源短缺,提高能量利用率等方面具有 不可言喻的重要意义。本文主要研究针对汽车尾气能量,设计斯特林发动机的换热系 统,通过性能实验测试、理论模型分析及数值模拟,找出斯特林发动机效率影响的主 要因素,为优化斯特林发动机提供理论依据。 本文针对汽车尾气能量,设计一台能够利用汽车尾气余热驱动的斯特林发动机换 热系统,并在此基础上,对小型斯特林发动机进行性能实验测试。实验研究内容主要 包括在恒扭矩和变扭矩时,对应的充气压力为 5bar、10bar、12bar 及 14bar 共 8 组实 验工况下,分别测量加热温度,充气压力对输出功率的影响,斯特林发动机的动力输 出特性及能量的分析。仿真计算及数值模拟主要研究内容包括应用 MATLAB 软件仿真 计算斯特林发动机的工作过程(循环压力 17bar)并且计算不同工况时(充气压力为 5bar,10bar,12bar,14bar)发动机的指示功率;应用 ANSYS 软件模拟回热器的压力 场,并对影响回热器压降的因素进行分析。 实验研究发现, 1.热源温度,斯特林发动机的输出功率随热源温度的增加而增大; 2.充气压力,不同的热源温度,对应着不同的最佳充气压力,在最佳充气压力之 前,斯特林发动机的输出功率随着充气压力的增加而增大,达到最佳充气压力后,若 继续充压,则会使输出功率下降,同时发动机产生较大震动; 3.循环过程中换热器总压力损失最大值接近 7bar,这说明换热器内的流动阻力比 较大,换热器的尺寸还可进行优化; 4.发动机最大输出扭矩为 5.39N m,是在充气压力为 14bar 时获得的,当负载逐 渐增加时,速度也逐渐减少; 5.随着充气压力的增加,指示效率与有效效率均增加。 模拟研究发现, 1.实验样机的指示功率与模拟结果相差较大,说明实验样机还需要进一步优化; 2.由于无益容积、回热器流阻损失等使得实际斯特林循环功与理想斯特林循环功 相差较大; 3.回热器丝网目数的增加,会导致回热器流阻损失增大;丝网直径的增加,则使 回热器流阻损失减小。 综上所述,在设计斯特林发动机时,加热器的制造应选择耐高温材料;同时,确 定循环压力参数时,应重点考虑工质的密封性能。斯特林发动机的实际循环与理想循环具有较大差别,且主要是由回热器的存在而引起的,回热器的性能优劣是影响斯特 林机性能好坏的关键因素。 关键词,斯特林循环;换热系统;充气压力;回热器流阻损失ABSTRACT With the development of automotive industry, the global energy shortage is growing. So how to use exhaust heat energy of cars is increasingly attract researchers. As the energy-saving devices, Stirling engine has some advantages, such as a wide range of fuels, high conversion efficiency, low noise and so on. Most scholars at home and abroad carried out the research on the recovery of automobile exhaust energy , but the application of the Stirling engine has ineffable significance in solving the energy shortage , improve energy utilization on recovering automobile exhaust energy. This article studies the automobile exhaust energy ,the design of the Stirling engine heat exchanger system ,try to identify the main factors to impact the efficiency of the Stirling engine through the performance of laboratory tests ,theoretical analysis and numerical simulation model, the Stirling engine is optimized to provide the theoretical basis. In this paper, emphasizes automobile exhaust energy , which designed a Stirling engine heat exchanger system to take advantage of automobile exhaust heat-drive. And on that basis, provides the experimental performance test of a small-scale Stirling engine. Experimental studies include eight experiments which are the torque are constant and variable, respectively, corresponding to the charge pressure of 5bar, 10bar, 12bar and 14bar. Test the heating temperature and charge pressure have an effect on output power of Stirling engine. Make a analysis of engine dynamics energy. Numerical Simulation main contents include using MATLAB software simulation Stirling engine working process (cyclic pressure 17bar) and calculate the indicates power of engine at the different conditions (inflation pressure 5bar, 10bar, 12bar, 14bar). Use ANSYS software simulation the pressure field of regenerator, and make a analysis of the impact of the regenerator pressure drop. Experimental studies indicate that: 1, Heating temperature: the output power of engine increase along with heating temperature growth. 2, Charge pressure: Different heating temperature, corresponding to different optimum charge pressure. Before the best charge pressure, output power of engine increase along with charge pressure growth, after the best charge pressure, if continue to increase pressure, the output of engine will decline and vibration. 3, During the cycle, the maximum total pressure close to 7bar, which shows the flow resistance in the heat exchanger is relatively large, the size of the heat exchanger may be optimized. 4, The maximum torque of engine is 5.39N.m which is obtained when the charge pressure of 14bar, the speed of engine will reduce along with load growth.5, The indicate and effective efficiency increase along with charge pressure growth. Numerical simulation studies indicate that: 1, The indicated power of simulation and prototype have a large deviation, so the test engine need to be optimized prototype further. 2, Because of the engine die volume and the flow resistance of regenerator, there is a large deviation of the actual cycle and the ideal cycle of Stirling output power. 3, The flow resistance loss of regenerator increase along with the wire mesh growth and the flow resistance loss of regenerator decline along with wire diameter of regenerator. In summary, in the Stirling engine design, the manufacture of high temperature materials should be selected heater; Also, make sure the loop pressure parameters, should focus on the sealing performance of the working fluid. Actual and Ideal Cycle Stirling engine cycle has a big difference, and is dominated by the presence of the regenerator caused, regenerator performance is a key factor affecting the merits of the Stirling engine performance is good or bad. Key Words: Stirling cycle, exchanger system, charge pressure, flow resistance lossI 目 录 第一章 绪 论......................................................................................................................1 1.1 发动机尾气能量回收利用的研究背景及意义..................................................... 1 1.1.1 能源现存问题....................................................................................................... 1 1.1.2 能源梯级利用...................................................................................................... 3 1.2 汽车尾气能量回收利用的国内外研究................................................................. 4 1.2.1 余热温差发电...................................................................................................... 4 1.2.2 废气涡轮增压...................................................................................................... 5 1.2.3 余热驱动汽车空调制冷系统.............................................................................. 5 1.2.4 利用废气余热输出功技术.................................................................................. 6 1.3 余热驱动斯特林发动机的国内外研究.................................................................. 6 1.4 研究目标及研究内容............................................................................................. 8 第二章 斯特林发动机的工作原理及分析........................................................................10 2.1 斯特林发动机的构造及优点................................................................................ 10 2.1.1 斯特林发动机的基本构造................................................................................. 10 2.1.2 斯特林发动机的类型........................................................................................ 11 2.1.3 斯特林发动机的优点........................................................................................ 12 2.2 斯特林发动机工作原理....................................................................................... 13 2.2.1 可逆斯特林循环...............