Effect of protrusion amount on gas ingestion of radial rim seal

In this paper, the effect of different amount of protrusion on various parameters in rotor–stator system was experimentally studied by measuring CO₂ concentration and pressure, in order to obtain the optimal protrusion amount. The parameters of different dimensionless sealing flow were measured under the condition that the annulus Reynolds number was 4.39 × 10⁵ and the rotating Reynolds number was 1.05 × 10⁶. The results show that the change of the amount of protrusions has little effect on the static pressure in the cavity, and the static pressure change near the sealing ring is almost negligible. But the total pressure and sealing efficiency increase first and then decrease with the increase of the amount of protrusion. The variation of power consumption is the same. A complex vortex structure will appear at the high radius region when the protrusion is installed. On the other hand, the protrusion can effectively reduce the minimum sealing flow of the rotor–stator cavity. Furthermore, considering the sealing efficiency and power consumption, the best range of the protrusion amount is about 36. The ratio near this range can optimally balance the alleviation of the gas ingestion and the reduction of the power consumption.     

A novel control method for turboshaft engine with variable rotor speed based on the Ngdot estimator through LQG/LTR and rotor predicted torque feedforward

In order to compensate for the disturbance of wide variation in rotor demanded torque on power turbine speed and realize the fast response control of turboshaft engine during variable rotor speed, a cascade PID control method based on the acceleration estimator of gas turbine speed (Ngdot) and rotor predicted torque feedforward is proposed. Firstly, a two-speed Dual Clutch Transmission (DCT) model is applied in the integrated rotor/turboshaft engine system to achieve variable rotor speed. Then, an online estimation method of Ngdot based on the Linear Quadratic Gaussian with Loop Transfer Recovery (LQG/LTR) is proposed for power turbine speed cascade control. Finally, according to the cascade PID controller based on Ngdot estimator, a rotor demanded torque predicted method based on the Min-batch Gradient Descent-Neural Network (MGD-NN) is put forward to compromise the influence of rotor torque interference. The simulation results show that compared with cascade PID controller based on Ngdot estimator and the one combined with collective pitch feedforward control, the novel control method proposed can reduce the overshoot of power turbine speed by more than 20%, which possesses faster response, superior dynamic effect and satisfactory robustness performance. The control method proposed can realize the fast response control of turboshaft engine with variable rotor speed better.     

预旋系统稳态和非稳态计算对比研究

针对预旋系统由于旋转引起流场和温度场参数周期性瞬态变化的问题，分别采用滑移网格的瞬态法和固定转子相位的稳态法进行数值求解，并在稳态计算中通过改变转子相位来近似模拟非稳态问题的时空变化特性。通过稳态空间平均结果与非稳态时均结果的对比，以期为预旋系统非稳态问题的低成本求解提供方法依据。结果表明：稳态计算结果与非稳态计算结果相比，周期性波动频率一致，接受孔进口处，稳态计算的压力波动幅度小39%左右，温度波动幅度小15%左右；多个相位的稳态空间平均结果与非稳态时均结果相比，压力高0.2%，温度低0.1%；采用多个计算周期数与单个周期的非稳态计算结果差异微小。当采用喷嘴出口气流中心正对接受孔迎风面前缘的转子相位时，稳态计算结果与非稳态计算时均结果最接近。     

燃料分级对旋流火焰的动态特性影响研究

为深入研究分级旋流火焰特性,以分级旋流模型燃烧室为研究对象,对四个不同燃料分级比(Rf)条件下的分级旋流火焰进行了数值研究,在时均燃烧场特性分析的基础上进一步对燃料分级比为1和3两个工况进行了基于壁面建模的大涡模拟(WMLES)研究。结果表明:燃料分级比的改变会影响中心回流区(CRZ)的长度和宽度。燃烧室中截面的散点分布图能够显示出不同燃料分级比条件下的燃烧特征。燃料分级比为1时,燃烧室剪切层仅存在零散的涡破碎区;而燃料分级比为3时,伴随涡破碎区还出现了单螺旋分支进动涡核(PVC)。通过FFT变换获得的燃烧室内剪切层速度能谱主频与进动涡核的旋转频率相同,表明内剪切层速度脉动的产生与进动涡核有关。另外进动涡核会使流场内的燃料分布和燃烧模式发生周期性的变化,进而影响燃烧过程。调整燃料分级比在1附近,能够使分级火焰达到稳定燃烧降低排放的目标。     

商用航空发动机转子部件的电子束焊接

现代商用航空发动机具有长寿命、高可靠性等要求,这对电子束焊接头的设计、制造及检测均提出了更高的要求。介绍了航空发动机转子部件电子束焊接结构及接头设计形式、检测要求,指出了针对商用航空发动机转子电子束焊需开展的研究工作。     

A coupling VWM/CFD/CSD method for rotor airload prediction

A coupling fluid-structure method with a combination of viscous wake model(VWM),computational fluid dynamics(CFD) and comprehensive structural dynamics(CSD) modules is developed in this paper for rotor unsteady airload prediction. The hybrid VWM/CFD solver is employed to model the nonlinear aerodynamic phenomena and complicated rotor wake dynamics;the moderate deflection beam theory is implemented to predict the blade structural deformation; the loose coupling strategy based on the ‘delt method' is used to couple the fluid and structure solvers.Several cases of Helishape 7A rotor are performed first to investigate the effect of elastic deformation on airloads. Then, two challenging forward flight conditions of UH-60 A helicopter rotor are investigated, and the simulated results of wake geometry, chordwise pressure distribution and sectional normal force show excellent agreement with available test data; a comparison with traditional CFD/CSD method is also presented to illustrate the efficiency of the developed method.     

直升机旋翼回波特性建模

给出了雷达半主动寻体制的直升机旋翼回波模型,分析了直升机旋翼回波的时频特性,以旋翼真实参数对模型进行了仿真,并研究了直升机旋翼回波在时域上的调制效应及频域分布特点。结果表明：理论模型所得结果与外场实验的导引头跟踪直升机实验数据吻合。     

基于实验设计和响应面模型的风扇转子气动优化设计

针对跨声速风扇动叶中掠、弯结合叶片基于控制点的B样条曲线对积叠线进行参数化,以掠、弯为设计自由度,应用实验设计、三维粘性流场求解、响应面模型及遗传算法对Rotor 67以近尖峰效率工况点为设计点对风扇转子进行了气动优化设计,得到了前掠与弯向旋转方向的复合设计叶片,其总压比有较明显提高。但由于优化是在单一工况点下进行的,其变工况性能不佳。     

A tip clearance prediction model for multistage rotors and stators in aero-engines

Tip clearances of multistage rotors and stators greatly affect aero-engines’ aerodynamic efficiency, stability and safety. The inevitable machining and assembly errors, as well as the complicated error propagation mechanism, cause overproof or non-uniform tip clearances. However, it is generally accepted that tip clearances are difficult to predict, even under assembly state. In this paper, a tip clearance prediction model is proposed based on measured error data. Some 3D error propagation sub-models, regarding rotors, supports and casings, are built and combined. The complex error coupling relationship is uncovered using mathematical methods. Rotor and stator tip clearances are predicted and analyzed in different phase angles. The maximum, minimum and average tip clearances can be calculated. The proposed model is implemented by a computer program, and a case study illustrates its performance and verifies its feasibility. The results can be referred by engineers in assembly quality judgement and decision-making.     

液体火箭发动机涡轮泵转子密封系统动力稳定性研究（该文已撤销，具体请见2015年第12期第1458页的撤销声明）

针对低温液体火箭发动机涡轮泵转子密封系统开展了动力学稳定性研究。采用有限元法建立了涡轮泵转子密封系统的动力学模型,研究了安装偏心对转子密封系统稳定性的影响,给出了失稳转速随安装偏心的变化规律,研究了当量密封间隙对涡轮泵转子系统稳定性的影响,分析了当量密封间隙对失稳转速的影响,最后开展了冷吹试验和热试试验研究,为液体火箭发动机涡轮泵转子系统结构设计、诊断与维护提供理论依据。