航空发动机技术进步与投资强度的定量关系

对航空发动机技术水平提高速度与投资强度这两个概念做了界定.利用有关数据,针对航空涡轮发动机的技术水平提高速度、最大推力、类型(涡喷或涡扇)与投资强度的定量关系建立了的一个数学模型,并对模型的应用进行了探讨.     

喷管分离流动与侧向载荷定常数值模拟

利用商业CFD软件,进行了三维、有粘、定常计算,模拟了某液体火箭大面积比喷管地面条件下的分离流动.计算了多个不同入口总压下的工况.其结果预示了该喷管的分离流动在不同入口总压下的激波模态变化,并获得了非对称分离及其造成的侧向载荷的分布情况.计算为进一步相关研究打下了基础.      

电磁阀式两相脉冲爆震火箭发动机试验

为了提高脉冲爆震火箭发动机的工作频率,设计了一台内径30mm,长度1000mm的电磁阀式脉冲爆震火箭发动机模型.脉冲爆震火箭发动机模型采用航空煤油为燃料,压缩氧气为氧化剂,压缩氮气为隔离气体,通过选用高速大流量电磁阀,加热燃料,安装Shchelkin螺旋等方法,使得该模型能够在20～30Hz频率下多循环稳定工作.工作频率为30Hz时,爆震波峰值压力达到2.2MPa.脉冲爆震火箭发动机的时均推力随着工作频率的提高接近线性增大.      

一种改进的航空发动机转静件碰摩故障诊断方法

针对航空发动机碰摩故障的实际情况,分析了各种诊断方法的应用局限性,引入并改进适用于航空发动机碰摩诊断的基于SVD(奇异值分解)的碰摩特征提取方法:提出利用数据边界延拓来消除边界振荡,以此发展了适合短时间序列和长时间序列的奇异值分解处理方法,并探讨了简便实用的奇异值选择方法.并在某航空发动机故障信号的检测中,取得了良好的效果.      

基于红外传感器智能车的设计与实现

目的结合飞思卡尔全国智能车大赛,介绍一种基于红外反射式光电传感器路径识别的智能车控制系统;方法利用10路红外光电传感器构成光电传感器阵列采集路面信息,采用霍尔式速度传感器采集小车速度信息;结果单片机获得路径信息和车速信息后,用以控制智能车的舵机转向,同时对电机进行调速,实现智能车沿着既定的跑道自主运行;结论试验证明,系统能够较好地满足智能车对路径识别和稳定性的要求,具备一定的抗干扰能力,能够快速平稳地自动寻迹行驶。     

内并联型TBCC进气道方案设计及验证

提出了一种带可变几何泄流腔的内并联型涡轮基组合循环(TBCC)进气道设计方案.介绍了进气道的总体设计思路,给出了进气道的设计马赫数、转级马赫数及飞行轨迹,对不同来流条件下进气道的工作方式以及全马赫数范围进气道型面调整的安排进行了论述,确定了进气道主要气动参数与型面参数的选取原则.通过数值模拟和高速风洞试验的手段,对进气道设计方案的可行性进行了验证.数值模拟结果表明:当Ma₀≤2.5时,进气道的总压恢复系数均在0.8以上,当2.5<Ma₀≤4.5时,进气道的总压恢复系数均在0.3以上,符合进气道总体方案的要求;冲压模态下,冲压通道的出口马赫数均小于0.4,出口静压均大于0.5个标准大气压,均能满足冲压燃烧室的燃烧需求.风洞试验结果表明:模态转换过程中,进气道涡轮通道具有良好的进/发匹配特性,且进气道涡轮/冲压通道具有良好的相容性能.研究结果可为我国开展组合动力研究提供方案参考和技术储备.      

涡轴发动机尾气静电监测信号影响因素分析

 针对某型航空涡轴发动机试车台实验所获得的尾气静电监测信号,结合发动机台架试车状态和性能数据,分别在两个时间尺度上展开分析研究。研究发现发动机的工作状态和健康状态均对尾气静电信号产生重要影响。在小时间尺度上的分析发现,无故障情况下影响尾气静电信号变化的主要因素为燃油供给量,尾气静电信号能量随燃油供给量的增加近似按指数规律上升;而在大时间尺度上的分析发现,在一定的燃油供给和恒定的自由涡轮转速条件下,尾气静电信号能量随着发动机性能的缓慢衰退而逐渐上升。实测尾气静电信号所反映的趋势与初步的理论分析结果相一致,为建立涡轴发动机尾气静电信号的健康"基线",进而用于气路状态监测及故障识别提供了初步的依据。研究还发现,静电监测技术不仅能够为突发性故障提供预警信息,而且能够反映发动机整机性能衰退,进一步拓展了静电传感器的监测能力及其在航空发动机健康管理中的应用。     

Effect of scavenge port angles on flow distribution and performance of swirl-loop scavenging in 2-stroke aircraft diesel engine

Swirl-Loop Scavenging (SLS) improves the performance of 2-stroke aircraft diesel engine because the involved swirl may not only benefit the scavenging process, but also facilitate the fuel atomization and combustion. The arrangement of scavenge port angles greatly influences in-cylinder flow distribution and swirl intensity, as well as the performance of the SLS engine. However, the mechanism of the effect and visualization experiment are rarely mentioned in the literature. To further investigate the SLS, Particle Image Velocimetry (PIV) experiment and Computational Fluid Dynamics (CFD) simulation are adopted to obtain its swirl distribution characteristics, and the effect of port angles on scavenging performance is discussed based on engine fired cycle simulation. The results illustrate that Reynolds Stress Turbulence model is accurate enough for in-cylinder flow simulation. Tangential and axial velocity distribution of the flow, as well as the scavenging performance, are mainly determined by geometric scavenge port angles α_geom and β_geom. For reinforcement of scavenging on cross-sections and meridian planes, α_geom value of 27° and β_geom value of 60° are preferred, under which the scavenging efficiency reaches as high as 73.7%. Excessive swirl intensity has a negative effect on SLS performance, which should be controlled to a proper extent.     

Designing method of acceleration and deceleration control schedule for variable cycle engine

Studies show that different geometries of a Variable Cycle Engine (VCE) can be adjusted during the transient stage of the engine operation to improve the engine performance. However, this improvement increases the complexity of the acceleration and deceleration control schedule. In order to resolve this problem, the Transient-state Reverse Method (TRM) is established in the present study based on the Steady-state Reverse Method (SRM) and the Virtual Power Extraction Method (VPEM). The state factors in the component-based engine performance models are replaced by variable geometry parameters to establish the TRM for a double bypass VCE. Obtained results are compared with the conventional component-based model from different aspects, including the accuracy and the convergence rate. The TRM is then employed to optimize the control schedule of a VCE. Obtained results show that the accuracy and the convergence rate of the proposed method are consistent with that of the conventional model. On the other hand, it is found that the new-model-optimized control schedules reduce the acceleration and deceleration time by 45% and 54%, respectively. Meanwhile, the surge margin of compressors, fuel–air ratio and the turbine inlet temperature maintained are within the acceptable criteria. It is concluded that the proposed TRM is a powerful method to design the acceleration and deceleration control schedule of the VCE.     

Integration of high-fidelity model of forward variable area bypass injector into zero-dimensional variable cycle engine model

Forward Variable Area Bypass Injector (FVABI) is one of key components which contributes to modulate the cycle parameters of Variable Cycle Engine (VCE) under various operation conditions. The modeling method of zero-dimensional FVABI was reviewed and its deficiency was analyzed based on FVABI flow characteristic. In order to improve the accuracy of VCE performance simulation, the high-fidelity modeling method of FVABI was developed based on its working characteristics. Then it was coupled with the zero-dimensional VCE model and the multi-level VCE model was built. The results indicate that the geometric and aerodynamic parameters can affect the interaction between the two airflows and the zero-dimensional FVABI model is too simple to predict the component performance accurately, especially when the FVABI inner bypass is chocked. Based on the performance curves for single bypass mode and the regression model of multi-scale support vector regression for double bypass mode, the high-fidelity model can predict FVABI performance accurately and rapidly. The integration of high-fidelity FVABI model into zero-dimensional VCE model can be done by adjusting iterative variables and balance equations. The multi-level model has good convergence and it can predict VCE performance when the FVABI inner bypass is chocked.