组合发动机空气预冷换热器动态特性的数值分析

基于守恒原理，导出叉流管－管型换热器非稳态传热过程的数学模型及相应的离散方程。利用隐式格式，求得组合发动机空气预冷换热器随时间而变的出口及壁面温度。指出此类动态计算若采用显式格式是极其费时的。对比解析解及显式方法的计算结果，表明隐式方法的解是有效可信的。所编计算机程序可用于发动机系统调式。     

一种改进的空间载人机动装置参数辨识鲁棒投影算法

空间载人机动装置(MMU)在进行救援过程中,其动力学参数存在很大的不确定性.为解决这一辨识问题,本文首先推导系统关于各动力学参数的线性化模型,然后结合该线性模型的特点,提出了一种用于估计动力学参数的改进鲁棒投影算法,并在理论上分析了该算法的收敛性质,数字仿真验证了方法的有效性.     

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.     

卫星单相流体回路热控系统前馈PID控制

利用传热学相关理论,对卫星单相流体回路热控系统的传热机理进行了分析与简化,建立起一个包括卫星单相流体回路各热组件模型、受控对象模型与控制系统模型的系统动态热模型。针对卫星单相流体回路系统惯性比较大,温度经常超调的特点,提出在现有PID反馈控制的基础上,引入系统热负荷作为反映系统扰动信号的前馈控制,以减少系统温度的动态偏差。利用热力学模型进行了仿真研究,仿真结果表明:采用以"系统热负荷"为信号的前馈PID控制温度超调量更小,具有更好的控制性能。仿真结果也可用于指导工程设计。     

一种实时测量微推力瞬时值的方法

微推进器是微型航天器的重要功能器件。实时测量微推进器不同时刻推力的瞬时值对研究微推进器的工作机理很有帮助;对于工作在低频多脉冲条件下的推进器,通过实时测量微推力的瞬时值,也可以获得多脉冲微推力的信息。提出了一种瞬态微推力的实时测量方法。初步仿真计算结果表明,此方法具有很好的跟踪特性,计算精度较高,可用于低频多脉冲微推力以及连续微推力实时测量。     

Numerical investigation of effect of a centrifugal boost impeller on suction performance of an aircraft hydraulic pump

An integrated boost impeller can effectively improve the suction performance of an aircraft hydraulic pump (AHP). It must be designed very carefully; however, few studies thus far have investigated boost impellers. To explore the effect of the boost impeller, this study developed a three-dimensional computational fluid dynamics (CFD) model for an AHP based on the k-ε turbulence model and full cavitation model. The results of verification tests demonstrated that the model is reliable for simulating the delivery characteristics of piston pumps and the boost capacity of the inlet impeller. Steady-state simulations reveal that the boost impeller can remarkably improve the suction performance and mitigate the cavitation damage due to insufficient fluid filling while only consuming a small proportion of the total input power. Transient-state simulations show that the pump with an impeller is more capable of catching up with a sudden increase in flow demand, and it has a lower suction flow ripple and impact. However, such a boost impeller also has some limitations such as magnifying the suction pressure fluctuation and having little effect on mitigating the cavitation caused by the back-flow jet.     

船用大功率柴油机瞬态工况油气响应及燃烧特性研究

针对船用大功率柴油机瞬态性能提升的需求，开展了增压中冷船用大功率柴油机瞬态工况动态响应及燃烧特性实验研究。研究表明，涡轮增压器惯性导致的进气滞后是柴油机瞬态工况下性能恶化的主要原因；突加载工况下，进气量响应滞后供油量响应4~5个工作循环，且进气量响应速度随初始负荷增加而增加，指示平均有效压力（Indicated Mean Effective Pressure，IMEP）等燃烧特征参数加载过程中响应速度较快，波动较小；缸内燃烧过程恶化，燃烧重心和燃烧终点较同负荷下稳态工况值均推迟。     

复合叶片对小流量工况下燃油离心泵非定常特性的影响

为了研究长中短复合叶片对小流量工况下燃油离心泵非定常特性的影响规律,基于CFD技术对某型燃油离心泵进行了非定常数值模拟。首先,分别建立原型方案和带有长中短复合叶片的优化方案的离心泵三维模型和网格模型。其次,基于RNG k-ε湍流模型,对两个方案中泵内流动非定常特性进行数值计算。仿真结果表明：长中短复合叶片减弱了叶轮流道内的大尺度漩涡,降低了叶轮的出口滑移,使得压力分布更加均匀。同时,叶轮与隔舌的动静干涉造成了蜗壳内一定程度的压力脉动产生,且长中短复合叶片相对较低。另一方面,小流量工况下,优化方案中离心泵的扬程为1826m,效率为26.9%,比原型方案中离心泵的扬程和效率分别提高了3.6%和2.6%。