一种新型气泡雾化喷嘴水平喷射特性的研究

研究了一种新型锥面注气方式的气泡雾化喷嘴，用水和压缩空气在常温常压下试验了水平喷射时结构和工作参数对雾化及流场特性的影响，用2D-PDA测量了液雾的平均直径尺寸分布和速度分布。结果表明，注气孔的尺寸及数目均对雾化特性产生一定影响；气泡发生器的锥角存在一最佳值，对于本文研究的结构，60°锥角可达到良好的雾化；混合段长度也存在一最佳值范围，提高液体的喷射压力和气液比，能够改善雾化，增大液雾的速度。实验结果表明，锥面多孔注气能有效地抑制水平喷射情况下由浮力产生的气泡聚合，能够使气泡均匀分布，实现稳定、连续的雾化。     

环喉环簇塞式喷管推力矢量控制研究

针对环喉环簇塞式喷管发动机的结构特点,提出了二次流喷射实现推力矢量控制的方案,并用数值方法研究了二次流的总温、总压、位置、角度、流量、喷射孔的数量以及孔间距等工作参数对推力矢量控制性能的影响。结果表明,侧向力与二次流的总温、总压、流量成正比关系;多孔比单孔的喷射效果好,孔与孔的间距要适当;逆向喷射比顺向喷射产生的侧向力大;喷射孔位置的选取受工作压比的影响很大。     

四桥臂三相逆变器的PWM控制

四桥臂三相逆变器的结构，其三相负载可以是平衡的或不平衡的，线性的或非线性的，由于第四桥臂的加入，控制变得非常复杂。本文分析了三相逆变器的调制信号与输入直流电压的关系。讨论了中点电压这个关键量。分析了该技术电压利用率不高的缺点，提出谐波注入法解决了该缺点，谐波注入法可以输出幅值更高的基波，同时谐波不会影响输出电流，文中提出了一种新的PWM控制方案，该方案电压利用率高，并能带任意负载载。仿真和实验结果证实了该方案的可行性。     

Multi-objective design optimization of the transverse gaseous jet in supersonic flows

The mixing process between the injectant and the supersonic crossflow is one of the important issues for the design of the scramjet engine, and the efficiency mixing has a great impact on the improvement of the combustion efficiency. A hovering vortex is formed between the separation region and the barrel shock wave, and this may be induced by the large negative density gradient. The separation region provides a good mixing area for the injectant and the subsonic boundary layer. In the current study, the transverse injection flow field with a freestream Mach number of 3.5 has been optimized by the non-dominated sorting genetic algorithm (NSGA II) coupled with the Kriging surrogate model; and the variance analysis method and the extreme difference analysis method have been employed to evaluate the values of the objective functions. The obtained results show that the jet-to-crossflow pressure ratio is the most important design variable for the transverse injection flow field, and the injectant molecular weight and the slot width should be considered for the mixing process between the injectant and the supersonic crossflow. There exists an optimal penetration height for the mixing efficiency, and its value is about 14.3 mm in the range considered in the current study. The larger penetration height provides a larger total pressure loss, and there must be a tradeoff between these two objection functions. In addition, this study demonstrates that the multi-objective design optimization method with the data mining technique can be used efficiently to explore the relationship between the design variables and the objective functions.     

Statistical characteristics of spray autoignition of transient kerosene jet in cross flow

To study statistical characteristics of the random spray autoignition, aviation kerosene was injected transiently into non-vitiated air crossflow in a flow reactor with optical accesses. The operating conditions were relevant to gas turbine combustor: the air crossflow pressure and temperature were in the range of 1.4–1.7 MPa and 830–947 K, respectively, and the jet-to-crossflow momentum flux ratios were 20, 50 and 80. Statistical distributions of random ignition delay times with adequate convergence were estimated based on histograms. The dependences of the distributions on reactor pressure, temperature, and jet-to-crossflow momentum flux ratio were studied. The results show that the resulting distributions appear more concentrated with the increase of air temperature or jet-to-crossflow momentum flux ratio. And then the correlations for the mean and standard deviation of the ignition delay time sample data were developed based on the present results. Compared with the correlations of ignition delay time of homogeneous premixed gas-phase kerosene/air mixture reported in the literature, the results show a greater significance pressure dependence and lower temperature sensitivity of the ignition delay time of non-premixed kerosene spray.     

多旋流器阵列贫油直喷燃烧室流场的数值模拟

采用雷诺应力模型(RSM)对于同旋向多旋流器阵列贫油直喷(LDI)燃烧室流场进行了数值模拟.计算结果表明,9个旋流器产生的回流区迅速变形衰减,在远离旋流器阵列的下游,形成了一个大的总体旋流.流场中存在的多个回流区及强湍流表明该燃烧室有潜力实现良好的燃烧性能.通过将RSM的模拟结果与激光多普勒测速仪(LDV)测量值进行比较发现,RSM准确描述了绝大部分流动特性,较好地求解了回流区和高速度梯度问题.      

气体二次喷射矢量喷管三维流场计算

采用三维雷诺平均Navier-Stokes方程和κ-ε湍流模型对气体二次喷射推力矢量喷管复杂干扰内流场进行数值模拟.比较了在不同喷射参数和不同喷管落压比NPR(Nozzle Pressure Ratio)下的流场特征,分析了这些参数对矢量偏转效率和推力系数的影响.结果表明,二次流喷射位置、喷射角度和二次流质量流量对矢量角的影响相互耦合,喷管达到最大矢量角时,各参数并不能同时达到各自的最优值;矢量角越大,推力系数越小,推力损失越大;矩形喷射口的推力矢量性能优于圆形喷射口;减小喷管落压比可以提高矢量偏转角度.     

考虑液体晃动效应的运载火箭等效转动惯量对姿控系统稳定裕度的影响

基于某型火箭,分析了考虑液体晃动后的全箭等效转动惯量变化,同时仿真了对姿控系统设计结果的影响,给出了姿控系统相关裕度的变化。结果表明:液体晃动的等效效应对一级转动惯量Jz的影响较小,对二级转动惯量Jz的影响较大;等效转动惯量对二级高频稳定裕度基本不产生影响,而系统的中、低频稳定裕度均有一定程度的下降。     

Trajectory Analysis of Fuel Injection into Supersonic Cross Flow Based on Schlieren Method

Trajectory analysis of fuel injection into supersonic cross flow is studied in this paper. A directly-connected wind tunnel is constructed to provide stable supersonic freestream. Based on the test rig, the schlieren system is established to reveal the fuel injection process visually. Subsequently, the method of quantitative schlieren is adopted to obtain data of both fuel/air interface and bow shock with the aid of Photoshop and Origin. Finally, the mechanism based on two influential factors of fuel injection angle and fuel injection driven pressure, is researched by vector analysis. A dimensionless model is deduced and analyzed. The curve fitting result is achieved. The relationship between the data and the two influential factors is established. The results provide not only the quantitative characteristics of the fuel injection in supersonic cross flow but also the valuable reference for the future computational simulation.     

SRAM型FPGA单粒子效应逐位翻转故障注入方法

针对SRAM(Static Random Access Memory)型FPGA(Field Programmable Gate Array)空间应用的可靠性评测问题,提出一种逐位翻转的故障注入试验方法,利用动态重配置技术,通过检测逻辑电路设计配置存储单元中的单粒子翻转敏感位数量和位置,可计算出动态翻转截面和失效率,绘出可靠度变化曲线.分别对采用TMR(Triple Modular Redundancy)防护设计的和未采用TMR防护设计的SRAM型FPGA乘法器模块进行了故障注入试验,验证了得到的敏感位位置的正确性,并计算出各自的可靠性参数和曲线.