向心涡轮盘腔非定常流动换热特性与模态控制规律研究

Micro gas turbine is wildly used in military and civilian fields. The flow and heat transfer characteristics of radial turbine cavity has a great impact on thermal efficiency of turbine and engine, rotor temperature and axial force. The unsteady three-dimensional flow results in periodic ingress of mainstream gas and various cavity modes, which is significant to predict engine life and noise considering high cycle thermal fatigue and pressure fluctuation. The literature about unsteady flow and heat transfer characteristics of turbine cavity mainly focus on axial turbine, so the relevant theory need to be verified in radial turbine. And the variation laws of periodic ingress and cavity modes with seal plate throat and structure need to be revealed. In addition, the leakage flow in the engine environment is important for accurately simulating the cavity flow structure. In view of the above three issues, firstly micro gas turbine test rig and numerical simulation are combined to obtain leakage flow in the engine. Secondly, the unsteady heat transfer conjugate simulation method is employed to study the ingress and cavity modes in the radial turbine cavity. Furthermore, seal plate throat and structure are changed to explore the control method of cavity modes.

微小型燃气轮机广泛应用于军民领域，其中向心涡轮转静盘腔内流动与传热特性直接影响部件与整机效率以及转子温度场与轴向力等，同时其强三维非定常特性表现出周期性燃气热侵和盘腔多模态流动特征等，因此产生的高周热疲劳和压力脉动对准确预估燃机寿命甚至噪声有重要意义。然而涡轮盘腔流非定常流动与换热特性研究主要侧重轴流涡轮，向心涡轮方面鲜有参考，轴流涡轮相关理论是否适用仍有待考证。同时不同泄漏流量和密封结构下，其周期性热侵和模态特征变化规律也有待揭示。另外，泄漏流量对于准确预估向心涡轮盘腔流动极为重要，需要准确获得整机环境下的泄漏流量。针对上述三个问题，本项目拟采用基于整机试验和仿真手段相结合以获得整机环境下泄漏流量边界条件，采用非定常流热耦合仿真揭示向心涡轮盘腔热流入侵与密封流泄漏机制和模态分布特征，进一步地，通过改变盘腔喉道面积和盘腔结构探索模态控制规律。

微小型燃气轮机广泛应用于军民领域，其中向心涡轮转静盘腔内流动与传热特性直接影响部件与整机效率以及转子温度场与轴向力等，同时其强三维非定常特性表现出周期性燃气热侵和盘腔多模态流动特征等。然而涡轮盘腔流非定常流动特性研究主要侧重轴流涡轮，向心涡轮方面鲜有参考。.基于此，本项目围绕向心涡轮盘腔非定常流动与换热特性开展研究。首先基于仿真和试验开展整机环境下涡轮盘腔流动研究。分析考虑背部盘腔时的不同轮盘结构（开式、半开式和闭式）向心涡轮流动特征，揭示了封严流影响下的涡轮内部复杂二次流动力学机制。同时获得其变工况下的气动特性曲线，建立总体仿真平台，并完成整机环境总体性能试验验证。.其次对向心涡轮盘腔非定常流热特性进行分析。建立了盘腔—涡轮全周模型并获得设计工况下的非定常流动机理和封严特性，结果表明盘腔高半径处存在着低于动盘转速的低压区，造成压力波动及燃气周期性入侵。.再次开展了不同流量下的向心涡轮盘腔动态流场及模态变化规律研究。结果表明，随着封严流量增大，盘腔高半径处低压区数目减少、转速降低，高半径处低频幅值先增大后减小。当封严流量进一步增大时，盘腔高半径处低压区消失，低频脉动消失，燃气入侵现象消失，因此盘腔内高半径处低压区的存在可以作为燃气是否入侵的重要判据。