内喷管单元间隙对塞锥换热的影响

为了解内喷管单元间隙对塞锥换热的影响,建立塞式喷管发动机的三维计算模型,采用数值模拟的方法对不同背压不同冷却剂流量下的塞锥进行换热研究,得出不同工况下的冷却剂温升、压降以及壁面温度、压强和热流密度的分布情况,其中着重研究了内喷管单元间隙对塞锥换热的影响.计算结果表明:由于受单元间隙的影响,造成沿宽度方向上塞锥壁面的压强、热流密度和温度的大小分布不均,并且随着环境压强的降低,单元间隙的影响有减弱趋势.      

一种简化算法的航空发动机全状态数学模型

通过一种简化的燃气空间模型对某型双转子混排加力涡扇发动机各部件进行了建模和仿真计算,并给出了详细的计算流程以及数学公式.在仿真过程中结合实际工程应用经验,对涡轮处采用一个局部的小循环迭代以减小涡轮部件内燃气空间计算的时间步长,提高计算精度.与其他数值方法相比,该简化算法避免了求解非线性方程组时大范围的循环迭代,提高了全状态数学模型的计算速度.通过仿真结果与发动机实际试车数据的对比,证明该方法有足够的计算精度.      

基于分布式专家系统的运载火箭故障诊断技术

针对运载火箭结构庞大,各分系统纵横交错、相互耦合的特点,基于分布式专家系统思想,提出了一种分布式运载火箭故障诊断技术方案.该方案采用产生式知识表达技术,将专家知识通过由测点表、征兆表、规则表和结论表组成的4表结构来表示,具有表述清晰、易于扩展和移植的特点.推理机制采用分布式推理和分级推理相结合的方式.分布式推理将运载火箭的系统级故障与各分系统级故障分别同时进行诊断,可有效提高诊断速度.分级推理将危害级别高的故障优先进行诊断,因此运载火箭一旦有危害程度大的故障发生时,可以及时发现、及时处置,从而使故障对系统的影响降至最低.      

基于DTW的涡扇发动机气路故障定量诊断方法

提出了一种利用动态过程信息对气路故障进行定量诊断的新方法.采用动态时间规整(DTW, Dynamic Time Warping)技术,对动态测试样本同已知的故障模式进行相似性度量,充分利用发动机的过渡态特征信息,实现了发动机气路部件故障的定量诊断.结果表明:这种方法的漏报率和误报率低,具有很高的诊断准确性,对测量噪声和其它不确定性具有很好的鲁棒性.      

长空发动机转速状态的调整规律

“长空发动机的控制是通过设计几个转速状态来实现的。但转速状态的调整一直比较困难。本文从理论上对此作了深入的分析,提出了简便的调整方法,给出了由实验得到的调整数据。     

Spectral analysis and self-adjusting mechanism for oscillation phenomenon in hydrogen-oxygen continuously rotating detonation engine

The continuously rotating detonation engine(CRDE)is a new concept of engines for aircraft and spacecraft.Quasi-stable continuously rotating detonation(CRD)can be observed in an annular combustion chamber,but the sustaining,stabilizing and adjusting mechanisms are not yet clear.To learn more deeply into the CRDE,experimental studies have been carried out to investigate hydrogen-oxygen CRDE.Pressure histories are obtained during each shot,which show that stable CRD waves are generated in the combustor,when feeding pressures are higher than 0.5 MPa for fuel and oxidizer,respectively.Each shot can keep running as long as fresh gas feeding maintains.Close-up of the pressure history shows the repeatability of pressure peaks and indicates the detonation velocity in hydrogen–oxygen CRD,which proves the success of forming a stable CRD in the annular chamber.Spectrum of the pressure history matches the close-up analysis and confirms the CRD.It also shows multi-wave phenomenon and affirms the fact that in this case a single detonation wave is rotating in the annulus.Moreover,oscillation phenomenon is found in pressure peaks and a self-adjusting mechanism is proposed to explain the phenomenon.     

An IPC-based Prolog design pattern for integrating backward chaining inference into applications or embedded systems

Prolog is one of the most important candidates to build expert systems and AI-related programs and has potential applications in embedded systems. However, Prolog is not suitable to develop many kinds of components, such as data acquisition and task scheduling, which are also crucial. To make the best use of the advantages and bypass the disadvantages, it is attractive to integrate Prolog with programs developed by other languages. In this paper, an IPC-based method is used to integrate backward chaining inference implemented by Prolog into applications or embedded systems. A Prolog design pattern is derived from the method for reuse, whose principle and definition are provided in detail. Additionally, the design pattern is applied to a target system, which is free software, to verify its feasibility. The detailed implementation of the application is given to clarify the design pattern. The design pattern can be further applied to wide range applications and embedded systems and the method described in this paper can also be adopted for other logic programming languages.     

Efficiency optimized fuel supply strategy of aircraft engine based on air-fuel ratio control

Accurate fuel injection control of aircraft engine can optimize the energy efficiency of UAV power system while meeting the propeller speed requirement. Traditional injection control method such as open-loop calibration causes instability of fuel supply which brings the risk of power loss of UAV. Considering that the closed-loop control of AFR can ensure a stable fuel feeding, this paper proposes an AFR control based fuel supply strategy in order to improve the efficiency of fuel-powered UAV while obtaining the required engine speed. According to the optimum fuel injection results, we implement fuzzy-PID method to control the set AFR in different situations. Through simulation and experiment studies, the results indicate that, to begin with, the calibrated mathematical model of the aircraft engine is effective. Next, this fuel supply strategy based on AFR control can normally realize the engine speed regulation, and the applied control algorithm can eliminate the overshoot of AFR throughout all the working progress. What is more,the fuel supply strategy can averagely shorten the response time of the engine speed by about two seconds. In addition, compared with the open-loop calibration, in this work the power efficiency is improved by 9% to 33%. Last but not the least, the endurance can be improved by 30 min with a normal engine speed. This paper can be a reference for the optimization of UAV aircraft engine.     

Inverted decoupling and LMI-based controller design for a turboprop engine with actuator dynamics

The main objective of the turboprop engine control system is to ensure propeller absorbed power at a constant propeller speed by controlling fuel flow and blade angle. Since each input variable affects the selected output variables, there exist strong interactions between different control loops of a Two-Spool TurboProp Engine (TSTPE). Inverted decoupling is used to decouple the interactions and decompose the TSTPE into two independent single-input single-output systems. The multi-variable PI controller and two single-variable PI controllers are designed for the TSTPE with actuator dynamics based on Linear Matrix Inequality (LMI), respectively, which is derived from static output feedback and pole placement condition. The step responses show that due to the difference in the response times of the selected output variables, it is difficult to design an appropriate multi-variable PI controller. The designed single-variable PI controllers are tested on the TSTPE integrated model to illustrate the effectiveness of the proposed method, that is, the interactions are first decoupled and then the controllers are designed, and the resulting simulated responses show that compared with the controller designed without actuator dynamics, the gas-generator shaft speed and power turbine shaft speed can better track their respective commands under the action of the controller designed with actuator dynamics.     

航空发动机H_∞控制器设计方法

本文提出了一种结构摄动系统鲁棒控制器综合方法。采用该方法可以同时考虑闭环系统的频域设计要求及对结构摄动的鲁棒稳定性。该方法被用于某型双转子涡喷航空发动机稳态控制器的设计，并取得了良好效果。