冲压发动机的固液燃气发生器方案研究

为解决固体火箭冲压发动机和固体燃料冲压发动机的流量调节问题,曾经提出过采用固液燃气发生器的方案。近年来,意大利那不勒斯大学航天科学与工程系研究了两种固液燃气发生器方案,用控制固液燃烧来调节进入冲压燃烧室的富燃料燃气流量,从而达到调节固体火箭冲压发动机和固...     

涡轮增压固冲发动机燃气调节研究

在涡轮增压固冲发动机(TSPR)中,驱动涡轮所需燃气的流量和压强应同时满足涡轮的要求。为实现TSPR的燃气调节,首先完成了等换算转速下TSPR涡轮对驱涡燃气的需求分析。验证了相对换算转速等于1的调节规律下,变燃面燃气发生器可以满足涡轮对燃气的需求,误差小于5%,但该调节方案限制了TSPR的应用范围。证明了在等相对换算转速的调节规律下,喉部面积可调的燃气发生器难以满足涡轮对燃气的需求。提出了换算转速松弛的调节规律,此种调节规律下的发动机实现了实时调节,但同相对换算转速等于1的发动机相比,发动机的速度包线减小了约50%,最大推力值和推力变化比明显减小。因此根据不同的任务需求发动机可选择不同的调节规律和与之对应的燃气调节方式。     

固体火箭冲压发动机燃气流量调节特性

为了研究固体火箭冲压发动机燃气流量调节特性,对固体火箭冲压发动机燃气流量控制阀的5种不同开度下的二维流场进行了数值模拟,分析得出了补燃室压力、阀门开度对流量控制阀流场分布、阀头轴向受力和通过控制阀的燃气质量流量的影响,基于模拟得到的数据,分析得到了固体火箭冲压发动机燃气流量调节特性的参数表达式,该表达式可以用来作为固体火箭冲压发动机燃气流量调节的参考。     

固体火箭发动机后效推力对导弹底阻影响的数值仿真

采用二维轴对称N-S方程与湍流模型相结合,建立了固体火箭发动机喷管尾流和弹体外流一体化仿真模型.针对给定的导弹模型,开展了不同发动机燃气流量下的流场仿真,得到了流场速度和压力分布,分析了不同燃气流量下发动机后效推力对导弹底阻的影响.结果表明:与发动机不工作时相比,加入较小的燃气流量后,导弹底部压力增大,底阻值减小.随着燃气流量的增加,底部压力先减小后增大,底阻先增大后减小.随着燃气流量的增加,后效推力与导弹底阻的合力不断增大,且动推力所占比重逐渐增加.      

固体推进剂吸气式涡轮发动机控制规律与特性

建立了用于控制规律研究的单变量控制和双变量控制的固体推进剂吸气式涡轮火箭发动机(SPATR)特性计算模型,并编制了相应的计算程序。计算模型中采用了以试验数据为基础的燃烧室出口总温计算方法。利用程序分别计算了燃气流量不可调、燃气流量可调、尾喷管喉部面积可调以及燃气流量和尾喷管均可调的不同控制规律的SPATR发动机速度特性,并分析了其特点。对SPATR发动机进行了双变量控制规律设计,得到了相应的燃气流量调节比和尾喷管喉部面积调节比。计算结果表明,按照所设计的双变量控制规律进行控制,SPATR具有很宽的飞行包线和更好的推力特性和比冲特性。     

用于燃气流量可调固冲发动机的贫氧推进剂

在分析了固体火箭冲压发动机的高度特性、壅塞式和非壅塞式固体火箭冲压发动机性能调节特性的基础上, 提出了燃气流量可以调节的燃气发生器, 尤其是非壅塞式固体火箭冲压发动机对贫氧推进剂的特殊要求。分析结果表明： 非壅塞式固体火箭冲压发动机要求贫氧推进剂具有高的燃速压强指数、低的可燃极限和足够好的燃烧稳定性。探讨了贫氧推进剂性能调节的途径。     

欧美固体火箭冲压发动机研制

详细介绍了欧美固体火箭冲压发动机的发展过程和研制情况,以及欧洲"流星"导弹用固冲发动机和美国"变流量火箭冲压发动机-飞行器概念"演示项目的研制和试验情况,并对固冲发动机关键技术的进展进行了分析.     

富氧补燃循环液氧煤油发动机深度推力调节方案对比分析

针对富氧补燃循环液氧煤油发动机目前推力调节范围窄的问题,以某型富氧补燃循环液氧煤油发动机为原型,建立了发动机非线性静态数学模型,利用Matlab计算分析了5种推力调节方案,其中调节推力室供应路流量的方案不可行;调节燃气发生器燃料路流量会引起燃气发生器混合比严重偏离稳定工作点;联合调节燃气发生器燃料路和氧路流量使得系统复杂;调节涡轮燃气流量可获得较宽推力调节范围,未来将针对该调节方案开展技术研究。     

固液混合火箭发动机仿真与优化设计

建立了固液混合火箭发动机的仿真模型和相应的单目标和多目标优化模型,编制了系统仿真程序;采用差分进化算法针对不同的优化目标对发动机的参数进行优化;针对挤压式系统建立了质量模型,在优化过程中考虑了主要部件结构质量对发动机性能的影响;针对固液发动机常用的侧面燃烧药柱编制了内弹道计算程序。以药柱几何参数、氧化剂流量、燃烧室平均工作压强和喷管扩张比等参数为设计变量,对发动机平均比冲、总质量、关机时飞行速度和密度比冲等性能参数进行优化,在Pareto分析的基础上选择了氧化剂流量、燃烧室平均工作压强和喷管扩张比对发动机性能的影响作了深入研究;最后对某型固液发动机进行了优化分析。     

跟踪微分器在变流量燃气发生器上的应用研究

变流量固冲发动机(VFDR)工作时,常采用PID控制器控制燃气发生器内燃气压强。对于阶跃或方波形式的压力指令,往往由于误差信号的突变使执行机构瞬时输出的控制力过大,产生较大的燃气压强超调与燃气流量负调,严重影响了控制系统的性能。为解决上述问题,在常规的PID控制器基础上,引入跟踪微分器(TD)给压力指令信号合理地安排一个快速无超调的过渡过程并提取微分信号。然后令燃气压强跟踪这个安排的过渡过程,使压强达到期望值。通过对变流量燃气发生器的非线性模型进行仿真试验,结果表明:相比于PID控制器,无论压力指令在高或低压强范围内,所提出的控制器均具有更高的稳态精度和快速性,压强的超调量不超过3.7%,响应时间在1s以内。此外,该控制器在抑制燃气流量的负调量上展现了巨大的优势,可将最大负调量减小2.7～3.25倍,显著地提升了VFDR的性能。     

The effect of inlet conditions on the flow and heat transfer in multiple rotating cavity with axial throughflow

This paper discusses experimental results from two different build configurations of a heated multiple rotating cavity test rig.Measurements of heat transfer from the discs and tangential velocities are presented.The test rig is a 70% full scale version of a high pressure compressor stack of an axial gas turbine engine.Of particular interest are the internal cylindrical cavities formed by adjacent discs and the interaction of these with a central axial throughflow of cooling air.Tests were carried out for a range of non-dimensional parameters representative of high pressure compressor internal air system flows(Re up to 5×106 and Rez up to 2×105).Two different builds have been tested.The most significant difference between these two build configurations is the size of the annular gap between the(non-rotating) drive shaft and the bores of the discs.The heat transfer data were obtained from thermocouple measurements of surface temperature and a conduction solution method.The velocity measurements were made using a two component,LDA system.The heat transfer results from the discs show differences between the two builds.This is attributed to the wider annular gap allowing more of the throughflow to penetrate into the cavity.There are also significant differences between the radial distributions of tangential velocity in the two builds of the test rig.For the narrow annular gap,there is an increase of non-dimensional tangential velocity V/Ωr with radial location to solid body rotation V/Ωr=1.For the wider annular gap,the non-dimensional velocities show a decrease with radial location to solid body rotation.      

Research on Auto-detection for Remainder Particles of Aerospace Relay Based on Wavelet Analysis

Aerospace relay is one kind of electronic components which is used widely in national defense system and aerospace system. The existence of remainder particles induces the reliability declining, which has become a severe problem in the development of aerospace relay. Traditional particle impact noise detection (PIND) method for remainder detection is ineffective for small particles, due to its low precision and involvement of subjective factors. An auto-detection method for PIND output signals is proposed in this paper, which is based on direct wavelet de-noising (DWD), cross-correlation analysis (CCA) and homo-filtering (HF), the method enhances the affectiv-ity of PIND test about the small particles. In the end, some practical PIND output signals are analysed, and the validity of this new method is proved.     

Preparation of Highly Dispersed Antimony-doped Tin Oxide Nano-powder via Ion-exchange Hydrolysis of SnCl4 and SbCl3 and Azeotropic Drying

Antimony-doped tin hydroxide colloid precipitates have been synthesized by hydrolysis of SnCl4 and SbCl3 using: (1) an ion-exchange hydrolysis to remove chlorine ions, and (2) isoamyl acetate as an azeotropic solvent to obviate water. The obtained dried powder is of high dispersivity without any need for further grinding. The size and dispersivity of the final particles are investigated with the aid of TG-DTA, BET, XRD and TEM. After having calcined, the antimony-doped tin oxide nanopowder possesses a tetragonal rutile structure with high dispersivity, uniform particles and low hard agglomeration.     

Effects of Mo on the Microstructure and Hydrogen Sorption Properties of Ti-Mo Getters

The effects of Mo on the microstructure evolution, porosity and hydrogen sorption properties of Ti-Mo getters are investigated in this work. The results show that the addition of Mo prolongs the densification process of Ti-Mo getters and results in a significant amount of sintered pores. With the Mo content increasing, the porosity of getters firstly increases reaching the maximum value as it at- tains about 7.5wt.%, and then drops. At the room temperature, the hydrogen sorption property of getters increases progressively with the Mo content increasing, but the tendency is not very clear before its content lies below 2.5wt.%. When the Mo content achieves about 7.5wt.%, the hydrogen sorption property proves to be the best. The discussion is made about the above mentioned phenomena inclusive of hydrogen sorption properties of getters under different activation conditions (from 500-750 ℃).     

超声速燃烧数值模拟中的湍流与化学反应相互作用模型

高精度数值模拟有助于理解超声速湍流燃烧中湍流与化学反应的相互作用,可为发动机燃烧室等工程应用设计提供可靠的预测模型。除直接数值模拟外,目前在湍流燃烧应用中使用的大涡模拟和雷诺平均Navier-Stokes模拟均需要借助模型模化发生在湍流小尺度上的流动与化学反应过程对湍流大尺度运动的影响。现有的湍流与化学反应相互作用模型大致可分为:火焰面类模型和概率密度函数类模型,2类模型在不同的应用中各自具有优势和局限性。此外,现有模型大都基于低马赫数燃烧,而超声速燃烧中通常会伴随快速混合、局部熄火和再着火以及激波等复杂过程,这为发展其中的湍流与化学反应相互作用模型提出了更多的挑战。     

适于低轨卫星IP网络的单核共享树组播算法(英文)

为了解决低轨卫星IP网络中现有典型源组播算法的信道资源浪费问题,本文提出了一套单核共享树组播算法,即核心群合并共享树(CCST)和加权核心群合并共享树(w-CCST)算法。CCST 算法包括动态近似中心(DAC)选核方法和核心群合并组播路径构建方法。DAC方法专为周期、规律运动的低轨卫星网络提出,不需要复杂的星上计算。在核心群合并方法中,以核节点作为初始核心群,通过核心群和剩余组成员的最短路径方法逐步扩展直至整棵组播树构建完成,从而使得组播树的树代价最小,大大提高了网络的带宽利用率和组播传输效率。w-CCST 算法中所提出的加权因子可以调整树代价和端到端传播时延之间的折衷程度,因此,可以通过调整加权因子来适度增大树代价、降低端到端传播时延以支持某些端到端时延要求苛刻的实时组播业务。最后,与低轨卫星 IP 网络中典型算法进行了性能比较,仿真结果说明,CCST 算法的平均树代价比其它算法显著降低,w-CCST 算法的平均端到端传播时延小于 CCST 算法。     

Jet Vectoring Control Using a Novel Synthetic Jet Actuator

A primary air jet vectoring control system with a novel synthetic jet actuator (SJA) is presented and simulated numerically. The results show that, in comparison with an existing traditional synthetic jet actuator, which is able to perform the duty of either “push” or “pull”, one novel synthetic jet actuator can fulfill both “push” and “pull” functions to vector the primary jet by shifting a slide block inside it. Therefore, because the new actuator possesses greater efficiency, it has potentiality to replace the existing one in various appli- cations, such as thrust vectoring and the reduction of thermal signature. Moreover, as the novel actuator can fulfill those functions that the existing one can not, it may well be expected to popularize it into more flow control systems.     

Nonlinear Adaptive Slewing Motion Control of Spacecraft Truss Driven by Synchronous V-gimbaled CMG Precession

The slewing motion control of a truss arm driven by a V-gimbaled control-moment-gyro (CMG) is a nonlinear control problem. The V-gimbaled CMG consists of a pair of gyros that must precess synchronously. The moment of inertia of the system, the angular momentum of the gyros and the external disturbances are not exactly known. With the help of feedback linearization and recursive Lyapunov design method, an adaptive nonlinear controller is designed to deal with the unknown items. Performance of the proposed controller is verified by simulation.     

An SOR Implicit Time-accurate Scheme in Calculating Unsteady Flows

A new time-accurate marching scheme for unsteady flow calculations is proposed in the present work. This method is the combination of classical Successive Over-Relaxation (SOR) iteration method and Jacobian matrix diagonally dominant splitting method of LUSGS. One advantage of this algorithm is the second-order accuracy because of no factorization error. Another advantage is the low computational cost because the Jacobian matrices and fluxes are only calculated once in each physical time step. And, the SOR algorithm has better convergence property than Gauss-Seidel. To investigate its accuracy and convergency, several unsteady flow computa- tional tests are carried out by using the proposed SOR algorithm. Roe’s FDS scheme is used to discritize the inviscid flux terms. Un- steady computational results of SOR are compared with the experiment results and those of Gauss-Seidel. Results reveal that the numerical results agree well with the experimental data and the second-order accuracy can be obtained as the Gauss-Seidel for unsteady flow computations. The impact of SOR factor is investigated for unsteady computations by using different SOR factors in this algorithm to simulate each computational test. Different numbers of inner iterations are needed to converge to the same criterion for different SOR factors and optimal choice of SOR factor can improve the computational efficiency greatly.