【作者】 魏杰；

【导师】 郑新前；

【作者基本信息】 清华大学 ， 动力工程及工程热物理， 2024， 博士

【摘要】 航空发动机启动、停车、加速、减速等瞬态过程叶尖间隙变化十分复杂,转子与机匣之间极易发生刮磨,从而导致叶片断裂甚至损毁整台发动机,造成灾难性后果。快速准确预测航空发动机瞬态叶尖间隙并对其实施有效控制,对提高航空发动机的安全性和经济性具有重要意义。本文基于航空发动机机匣、叶片、轮盘的几何特征和换热特性差异,建立了一/二维耦合的多维度瞬态叶尖间隙预测模型。本模型通过三维流-热-固耦合仿真和间隙测量试验在多型航空发动机的涡轮和压气机上开展了验证,所预测的间隙变化趋势与三维仿真和试验一致。本模型较一维模型在稳态和瞬态间隙的预测精度上分别提升0.6%和0.5%叶高,克服了传统一维模型预测精度不足的难题;与试验测量和三维仿真的预测偏差均不超过0.2%叶高,且预测速度较三维仿真提高了3个数量级,克服了传统三维仿真预测时间过长无法满足工程设计要求的难题。本文基于建立的多维度瞬态叶尖间隙预测模型,探明了采用变转速时间、盘腔冷却气流、材料属性、几何特征等不同控制因素的主动和被动控制策略对涡轮瞬态叶尖间隙的影响规律和机理。研究指出控制因素与间隙通常满足单调相关,盘腔冷气温度对涡轮叶尖间隙的控制效果最显著;轮辐厚度由于对轮盘热和离心变形的影响相反,与间隙不满足单调相关。基于瞬态间隙模型生成大量高精度快速预测样本,结合神经网络实现了多因素耦合控制对间隙影响的快速预测,该方法可用于机载实时叶尖间隙的监测和控制。本文发展了考虑叶尖间隙变化对发动机性能影响的性能预测方法,在变循环发动机上实现了考虑叶尖间隙变化影响的整机性能快速预测。论文分析了不同转速下前、后风扇和低压涡轮的叶尖间隙变化和部件特性变化,最终实现了航空发动机性能变化预测。与不考虑叶尖间隙变化的发动机性能预测相比,本文方法预测的100%转速下的耗油率偏差和高压涡轮进口温度偏差虽然分别仅为-0.1%和3 K,但推力偏差可达1.1%,对于大推力的航空发动机尤为重要,表明航空发动机的性能预测应该考虑叶尖间隙变化的影响。更多还原

【Abstract】 The variation of the tip clearance during startup,shutdown,acceleration,deceleration,and other transient processes of the aero-engine is very complicated,and it often cause scrapping between the rotor and the shroud,resulting in blade breakage or even damage to the whole engine,which brings in catastrophic consequences.Rapid and accurate prediction of the transient tip clearance and effective control of it is of great significance to improve the safety and economy of the aero-engine.Based on the geometric characteristics and heat transfer characteristics of the shroud,blade,and disk of the aero-engine,a multi-dimensional transient tip clearance model through one-dimensional/two-dimensional coupling is established.The model is verified through three-dimensional fluid-thermal-solid coupling simulations and clearance measurement tests on the turbine and compressor of multiple aero-engines.The predicted clearance variation trend is consistent with the results of three-dimensional simulations and tests.Compared with the one-dimensional model,this model improves the prediction accuracy of the steady and transient tip clearance by 0.6%and 0.5%of the blade height,respectively,overcoming the problem of insufficient prediction accuracy of the traditional one-dimensional model.The prediction deviation from tests and three-dimensional simulations is less than 0.2%of the blade height,and the prediction speed is three orders of magnitude higher than that of the three-dimensional simulation,which overcomes the problem that the traditional three-dimensional simulation can not meet the engineering design requirements for too long prediction time.Based on the established multi-dimensional transient tip clearance model,the influence law and mechanisms of the active and passive control strategies on the transient tip clearance of the turbine adopting different control factors such as shaft speed variation time,disk cooling flow,material properties,and geometric characteristics are investigated.It is pointed out that the control factors are usually monotonically correlated with the tip clearance,and the temperature of the disk cooling flow has the most significant control effect on the tip clearance of the turbine.The thickness of the disk diaphragm is not monotonically related to the tip clearance because it has opposite effects on the thermal and centrifugal deformation of the disk.In addition,numerous high-precision and fast prediction samples are generated based on the transient tip clearance model,and the effect of the coupling control on the tip clearance is quickly predicted by combining the neural network,and the neural network can be used to monitor and control the tip clearance for airborne real-time applications.This paper developed a prediction method for introducing the tip clearance impact to the engine,and it was conducted on the adaptive cycle engine.The variations of clearance of the front and rear fans and the low-pressure turbine and the change of component characteristics under different shaft speeds are analyzed,and the performance change of the engine is finally predicted.Compared with the prediction performance of the engine without considering the clearance variation,though the deviations of the fuel consumption and the inlet temperature of the high-pressure turbine are only-0.1%and 3K,respectively,the thrust deviation reaches 1.1%.The thrust deviation is significant,especially for the high-thrust aero-engines,which shows that the change of tip clearance should be considered in the performance prediction of aero-engines.更多还原