弹性体运载火箭建模及控制器设计

考虑运载火箭飞行过程中的弹性振动特性,对运载火箭进行全量动力学建模以及控制器设计。首先将运载火箭考虑为一维梁模型并建立全量动力学模型,分别引入自适应滤波姿态控制算法和H_2范数鲁棒增益调度控制算法设计控制器。仿真结果表明:在考虑舵机非线性情况下两种控制方法均能够满足精度要求,在具有较大外部扰动情况下,鲁棒增益调度控制算法相较于自适应滤波算法具有较强的鲁棒性。     

电容式多次放电点火系统设计与试验

针对某型二冲程点燃式空气辅助缸内直喷发动机燃用柴油问题,提出了实现单电容连续多次放电点火的方法,研制了直流电容式多次放电点火模块,进行了多次点火功能性验证及点火能量测试.在此基础上,进行了环境温度为6℃下的冷起动试验及3000r/min小负荷性能试验,结果表明:在该环境条件下,采用5次放电点火策略能够使发动机起动成功,在小负荷工况下,增加点火次数有利于改善缸内燃烧,点火提前角在10°~20°之间时,4次点火对发动机动力性、燃油消耗率及排放性能改善比2次点火更明显,当点火提前角提前至30°后,其改善作用逐渐减小.      

疲劳开裂结构等效分析谱构造方法

为了解决外场疲劳裂纹排故中结构疲劳载荷谱数据不全或过于复杂的问题,提出了一种适用于飞机外场疲劳开裂结构的等效分析谱构造方法。该方法以细节疲劳额定值(DFR)法和结构细节有限元分析为基础,构建地—空—地最大应力与结构疲劳寿命的变化曲线,进而通过寿命反推,获取适用的地—空—地损伤比,以此构建等效分析谱,谱型为等幅谱。通过应用实例,将该方法构造的载荷谱与实测谱进行了对比,确认了该方法的正确性和有效性。     

基于图论的燃油管路稳态流动计算方法

基于节点分析法,提出将局部损失并入相应管段的处理方法,推导阻力计算公式,从而得到兼顾沿程和局部损失的稳态流动计算方法。将该计算方法应用于实际的航空发动机燃油管路,采用VB.NET语言编写计算软件;同时,对燃油管路开展三维数值模拟计算。结果表明:局部损失对管路的流量分配影响较大;该计算方法得到的流量分配与数值计算结果趋势吻合很好,差别在±10%。      

电机变频控制实现换热器节能的应用研究

结合寒冷地区气候特点与通信机房温控的现状,针对50%浓度乙二醇溶液为工质的换热器,试验研究了自然冷源利用率与换热器自身变频节能的关系。结合乙二醇冷剂的特性,通过建立功率与频率关系模型、温差与功率和频率关系模型,实现了换热器循环泵和风机的变频控制策略。结果表明:在室内外温差、换热功率与循环泵、风机频率同时满足的条件下,以功率模型作为参数进行换热器自身的变频节能是可行的。通过对哈尔滨地区的气候数据与散热房控温试验分析,证明了乙二醇换热器的变频节能效果。     

永磁力矩电机三相绕组不对称性改进方法研究

由于力矩电机多作为驱动电机使用,且电机对低速平稳性要求很高,所以选用了一种特殊的极槽配合方式。12极39槽的选择使得电机齿槽转矩较小的同时导致电机三相绕组不对称。降低绕组不对称对电机低速平稳性的影响,对提高绕组的对称性的方法研究有着重要的意义。以一台采用12极39槽的力矩电机为例,提出了一种绕组不对称性的改进方法,通过改变绕组的排列方式提高了绕组的对称性,且保证了电机的低速平稳性。最终通过理论研究与仿真分析验证了不对称性改进方法的有效性。     

Coupled Lagrangian impingement spray model for doublet impinging injectors under liquid rocket engine operating conditions

To predict the effect of the liquid rocket engine combustion chamber conditions on the impingement spray, the conventional uncoupled spray model for impinging injectors is extended by considering the coupling of the jet impingement process and the ambient gas field. The new coupled model consists of the plain-orifice sub-model, the jet-jet impingement sub-model and the droplet collision sub-model. The parameters of the child droplet are determined with the jet-jet impingement sub-model using correlations about the liquid jet parameters and the chamber conditions.The overall model is benchmarked under various impingement angles, jet momentum and offcenter ratios. Agreement with the published experimental data validates the ability of the model to predict the key spray characteristics, such as the mass flux and mixture ratio distributions in quiescent air. Besides, impinging sprays under changing ambient pressure and non-uniform gas flow are investigated to explore the effect of liquid rocket engine chamber conditions. First, a transient impingement spray during engine start-up phase is simulated with prescribed pressure profile. The minimum average droplet diameter is achieved when the orifices work in cavitation state, and is about 30% smaller than the steady single phase state. Second, the effect of non-uniform gas flow produces off-center impingement and the rotated spray fan by 38°. The proposed model suggests more reasonable impingement spray characteristics than the uncoupled one and can be used as the first step in the complex simulation of coupling impingement spray and combustion in liquid rocket engines.     

Drag derived altitude aided navigation method

The navigation problem of the lifting reentry vehicles has attracted much research interest in the past decade.This paper researches the navigation in the blackout zone during the reentry phase of the aircraft,when the communication signals are attenuated and even interrupted by the blackout zone.However,when calculating altitude,a pure classic inertial navigation algorithm appears imprecise and divergent.In order to obtain a more precise aircraft altitude,this paper applies an integrated navigation method based on inertial navigation algorithms,which uses drag derived altitude to aid the inertial navigation during the blackout zone.This method can overcome the shortcomings of the inertial navigation system and improve the navigation accuracy.To further improve the navigation accuracy,the applicable condition and the main error factors,such as the atmospheric coefficient error and drag coefficient error are analyzed in detail.Then the damping circuit design of the navigation control system and the damping coefficients determination is introduced.The feasibility of the method is verified by the typical reentry trajectory simulation,and the influence of the iterative times on the accuracy is analyzed.Simulation results show that iterative three times achieves the best effect.     

CVD技术制备Ta/W层状复合材料

运用化学气相沉积(Chemical Vapor Deposition,CVD)技术制备了W体积分数分别10%,13%和18%的Ta/W两层层状复合材料,采用金相显微镜(OM)、扫描电镜(SEM)和室温拉伸实验对复合材料的性能进行分析。结果表明:运用CVD技术可以制备W体积分数不同,且密度优于理论密度99.4%的层状复合材料;复合材料中Ta,W层的晶粒均为柱状晶粒,离界面越近,晶粒越细;沉积态复合材料的力学性能优于纯CVD Ta和CVD W;1600℃×2 h的热处理后,复合材料的界面扩散层宽度显著增大,力学性能高于沉积态的力学性能,最高抗拉强度可达660 MPa。     

大型飞机整体壁板喷丸成形延展变形分析

针对基于喷丸成形的大型飞机机翼整体壁板延展变形问题,从影响整体壁板喷丸延展变形的因素出发,通过对整体壁板喷丸成形展向应变的理论计算和实测延展数据对比,得出整体壁板喷丸成形加工环节的延展变形规律。