【作者】 龚建波；

【导师】 聂超群； 徐纲；

【作者基本信息】 中国科学院研究生院（工程热物理研究所） ， 工程热物理， 2009， 博士

【摘要】 伴随着小型燃气轮机日益广泛的应用以及其尺度的不断缩小，燃机传热效应越来越明显，此时若对气体流动过程继续沿用绝热的处理方法，必导致燃机的设计估算误差。热量从燃机高温端(主要是透平)传入低温端(主要是压气机)，会带来一系列的副作用，包括压气机、透平乃至燃机整体性能都会受到影响。本文的主要内容即是针对非绝热“背靠背”小型燃气轮机，研究内部传热效应对性能的影响，通过热力学模型分析，阐述其传热机理，建立非转实验台，以CFD、实验等手段对燃机传热现象进行模拟和验证，进而考查相关隔热措施，指导改进非绝热小燃机设计。首先，本文在前人工作的基础上，推导分析了压气机和涡轮非绝热运行工况热力学模型。基于一定假设，定义三种不同的效率表达式，即为绝热效率、非绝热效率和传热效率。发现测量效率(即非绝热效率)不能准确反映部件的实际气动能力，它对压气机和涡轮实际气动效率的估计均存在偏差，而传热效率可视为实际气动效率。文章具体分析了影响各种效率改变的因素及变化趋势。本文采用ANSYS CFX软件对MarkⅡ叶片进行流热耦合验证计算并与实验值比较，研究表明虽然流热耦合计算的精度受湍流模型、转捩模型、网格密度等诸项因素制约，但相比非耦合计算，其结果更加接近真实值，完全满足工程计算要求。流热耦合计算的准确应用，将大大推动非绝热燃机的设计效率。本文以真实“背靠背”小燃机为模型，以相似准则为基准，自行设计了非转模型实验台，并且搭建了实验台软硬件测试系统。基于非转实验台进行传热实验考查，测量了不同工况条件实验件压气机、涡轮通道的壁面温度分布，并与数值计算结果进行对比，两组结果吻和得较好，进一步验证流热耦合计算的有效性。另一方面，考查了不同隔热方式的隔热效果，发现降低空隙辐射强度是工程上较为有效和可行的一种方法，从而给真实燃机的隔热设计提供了参考。本文针对某“背靠背”80kW非绝热小燃机建立三维整机计算模型，进行了CFD数值模拟。对比不同计算方式结果发现，绝热计算与耦合计算对流场影响的差别主要体现在温度场的不同上，而对流场内的压力场及其他参数影响不太明显。同时对有无隔热情况也进行了耦合计算比较，可以看到，采用有隔热耦合计算，燃机热效应明显减弱，这又一次验证了隔热设计对非绝热燃机的有效性。最后，为了使压气机性能与透平更好地相匹配，对非绝热压气机修改设计指标，并尝试进行了气动改进设计。新设计压气机提高了通流能力，并且减小了扩压器尺寸。计算结果表明，改进设计的压气机传热效应有所降低，取得一定效果。更多还原

【Abstract】 The small gas turbine is being used more widely accompany with its scale getting smaller and smaller, so the heat effect of gas turbine is more and more obvious nowadays. If we treat the gas flow as an adiabatic procedure, some mistakes of gas turbine design will be made. Because of the heat transfer from the hot side (mainly turbine) to the cold side (mainly compressor), many side-effects appear, such as the performance of compressor, turbine and the whole engine will be affected. The main work of this article is to investigate the inside heat transfer effect on the performance of non-adiabatic "back to back" small gas turbine. The thermodynamic model is analyzed to describe the mechanism of the heat transfer, and a non-rotating experiment rig is built to validate the heat transfer phenomenon by CFD or experiment. Further more the heat insulation method will be researched, and the design of non-adiabatic small gas turbine will be improved.First, on the work before, this article builds a non-adiabatic thermodynamic model of compressor and turbine. Based on certain assumptions, three different definitions of efficiency were proposed, that is adiabatic efficiency, diabatic efficiency and heat efficiency. It is found that the measurement efficiency (i.e. diabatic efficiency) can not describe the components’ actual aerodynamic power, and it estimates the aerodynamic efficiency in error. Meanwhile the heat efficiency can be treated as actual aerodynamic efficiency. This article discusses the factors affect the efficiency and their relationship.The ANSYS CFX software is used in this article to investigate the fluid-thermal coupling CFD method of MarkⅡtest case and compare with experimental data. The research shows that even though the precision of fluid-thermal coupling numerical simulation is restricted by turbulence model, transition model and mesh density, its result is closer to real value compare to non-couple numerical simulation, and it meets the engineering demands. So the fluid-thermal coupling CFD method will promote the design of non-adiabatic small gas turbine greatly.Based on real "back to back" small gas turbine, using similarity criterion, a non-rotating model experiment rig, together with hardware and software test system, is built. Heat transfer experiment is carried out on this test rig, and the temperature distribution on compressor and turbine wall in different conditions is measured. The experiment data conform to CFD result very well, which proved the validity of fluid-thermal coupling CFD method. On the other hand, the effect of different heat insulation method are investigated, and it is found that reducing the radiation intensity of interspace is a effective way in engineering, which will provide the experience for real gas turbine.This article practices the CFD numerical simulation of an 80kW "back to back" non-adiabatic small gas turbine 3D model. Comparing the results, the difference of adiabatic simulation and coupling simulation is mainly reflected on temperature field, rather than pressure field or other field. Meanwhile, it is different in the situation that with or without heat insulation. It can be seen from the simulation result that with heat insulation the heat effect of gas turbine is obviously weaker, and this proves the validity of heat insulation design for non-adiabatic small gas turbine.Finally, for making the compressor match the turbine well, the design target of non-adiabatic small gas turbine is changed, and new aerodynamic design is tried. The new design compressor improves the through-flow capability, and reduces the size of diffuser. The simulation result shows that the heat effect of new design compressor is braked, which makes progress.更多还原