Technical Innovation of LH2/LOX Rocket Engines in China

This paper provides a detailed introduction to and analysis of the course of China's technological innovation in liquid hydrogen/liquid oxygen(LH2/LOX)rocket engines from a historical point of view.It starts with the investigation of LH2/LOX rocket engines by relevant departments of the Chinese Academy of Sciences in the 1960s and their preliminary achievements.Then,the policy decision concerning LH2/LOX engine development,the project approval of the Long March-3(Chang Zheng-3,CZ-3)rocket,and the process of developing LH2/LOX engines are analyzed in detail,followed by an introduction to and summary of the development situation and technical innovation characteristics of China's LH2/LOX engines as they grew from 4 tons to 8 tons,and finally to 50 tons.Finally,the paper briefly analyzes the innovation experience connected with China's LH2/LOX engines.

Progress in Technology of Main Liquid Rocket Engines of Launch Vehicles in China

Liquid propellant rocket engines for a launch vehicle are an essential aerospace technology, representing the advanced level of hi-tech in a country. In recent years, China’s aerospace industry has made remarkable achievements, and liquid rocket engine technology has also been effectively developed. In this article, the development processes of China’s liquid rocket engines are discussed. Then, the performance features of China’s new generation liquid rocket engines as well as the flight tests of the new-generation launch vehicles are introduced. Finally, the development direction and the most recent progress of the next generation large-thrust liquid rocket engine is presented.

Research on Key Technologies for Reusable Liquid Rocket Engines

Based on current research,the development trend of reusable liquid rocket engines was analyzed.Key technologies and research focuses of the reusable liquid rocket engine have been analyzed and summarized,and then suggestions on the development of future key technologies are proposed.

Experimental Investigation on Performance of Pulse Detonation Rocket Engine Model

The PDRE test model used in these experiments utilized kerosene as the fuel, oxygen as oxidizer, and nitrogen as purge gas. The solenoid valves were employed to control intermittent supplies of kerosene, oxygen and purge gas. PDRE test model was 50 mm in inner diameter by 1.2 m long. The DDT （deflagration to detonation transition） enhancement device Shchelkin spiral was used in the test model. The effects of detonation frequency on its time-averaged thrust and specific impulse were experimentally investigated. The obtained results showes that the time-averaged thrust of PDRE test model was approximately proportional to the detonation frequency. For the detonation frequency 20 Hz, the time-averaged thrust was around 107 N, and the specific impulse was around 125 s. The nozzle experiments were conducted using PDRE test model with three traditional nozzles. The experimental results obtained demonstrated that all of those nozzles could augment the thrust and specific impulse. Among those three nozzles, the convergent nozzle had the largest increased augmentation, which was approximately 18%, under the specific condition of the experiment.

An Experiment on Cavitating Flow in Rocket Engine Inducer

An experiment for rocket engine inducer cavitating flow is conducted on a new experimental platform.The experiment platform,using water as working medium,can be used to investigate the steady and unsteady flows of cavitating and noncavitating turbopumps.The experimental platform is designed as a flexible and versatile apparatus for any kind of fluid dynamic phenomena relating to high performance liquid rocket engine turbopumps.Design details for the platform is introduced.Various extend of cavitation images and dynamic pressure impulse are obtained,which provides a reference for cavitating flow study in rocket engine inducer.

Ignition characteristics and combustion performances of a LO_2/GCH_4 small thrust rocket engine

A 500 N model engine filled with LO2/GCH4 was designed and manufactured.A series of ignition attempts were performed in it by both head spark plug and body spark plug.Results show that the engine can be ignited but the combustion cannot be sustained when head spark plug applied as the plug tip was set in the gaseous low-velocity zone with thin spray.This is mainly because flame from this zone cannot supply enough ignition energy for the whole chamber.However,reliable ignition and stable combustion can be achieved by body spark plug.As the O/F ratio increases from 2.61 to 3.49,chamber pressure increases from 0.474 to 0.925 MPa and combustion efficiency increases from 57.8%to 95.1%.This is determined by the injector configuration,which cannot produce the sufficiently breakup of the liquid oxygen on the low flow rate case.

Brief Review of N2O Decomposition Catalysts for Engines

A brief review of nitrous oxide decomposition catalysts was presented.The features of catalyst operating conditions in low-thrust engines of space vehicles and requirements to monopropellant(hydrogen peroxide,hydrazine,nitrous oxide)decomposition catalysts were considered.A scientific basis for development of a nitrous oxide decomposition catalyst and general principles for selection of efficient catalysts were formulated.The results of selecting catalyst systems for the development of decomposition catalysts for N2O as a monopropellant were presented.Preliminary selection of catalyst systems for the development of a catalyst designed for low-thrust rocket engines(LTREs)was carried out:supporter—Al2O3 and ZrO2;active substances—Co,Ni,Fe,Pd,Rh,Pt,Ru,Ir,NiO,Fe2O3,RuO2,Rh2O3,PdO,IrO2,PtO2,CoO,Al2O3,La2NiO4,Nd2NiO4,Pr 2NiO4,La2O3,TiO2,NiO,La2O3,TiO2,ZnO.With 71 references.

Based on Fluent Numerical Calculation of Refractive Index on Rocket Engine Nozzle Plume

Numerical 2D simulation and research on internal flow field and external flow field of rocket motor nozzle using FLUENT software. Analyze the flow condition of internal flow field and external flow field, and according to add in the amount of the different gas components, obtain the clear distribution of contour of density flow field, pressure flow field and various material components and so on. Simulation results agree with the results observed from the test on the ground, and provide reference for solid rocket motor development.

Safety Analysis of Liquid Rocket Engine Using Bayesian Networks

Safety analysis for liquid rocket engine has a great meaning for shortening development cycle, saving development expenditure and reducing development risk. The relationship between the structure and component of liquid rocket engine is much more complex, furthermore test data are absent in development phase. Thereby, the uncertainties exist in safety analysis for liquid rocket engine. A safety analysis model integrated with FMEA(failure mode and effect analysis) based on Bayesian networks (BN) is brought forward for liquid rocket engine, which can combine qualitative analysis with quantitative decision. The method has the advantages of fusing multi-information, saving sample amount and having high veracity. An example shows that the method is efficient.

Numerical and Experimental Characterizations of SiFRP Ablator for the Application to Liquid Rocket Engine Combustors

The ablative material is supposed to be one of good candidates for LRE （liquid rocket engine） combustion chamber to achieve both high reliability and low cost and a numerical analysis for the ablator is considered to be a potentially efficient tool to reduce cost as well. So far, ablators have been successfully applied for many SRM （solid rocket motors）, but the application to LRE is still quite limited in Japan. The authors believe that this is primarily because of the unpredictable nature of the heat load from combustion gases to the combustor wall. Indeed, reliable thermal design of ablative combustion chamber, namely reliable prediction of thermal performance, needs both reliable heat load model and reliable ablator response model. This paper elaborates our research activities and our recent research findings.

An Electro-Hydraulic Actuator for the TVC of a Throttlable Kerolox Rocket Engine

An electro-hydraulic actuator for the thrust vector control(TVC)of a throttlable kerolox rocket engine is introduced in this paper.The creative feature is an integrated hydraulic power drive unit,where a constant speed kerosene motor is used to draw high pressure kerosene from the engine and to drive a constant pressure variable displacement piston pump,acting as the power supply for the actuator.Its operational mechanism,to accommodate the varying pressure from the turbo-pump of a throttling engine,lies in a pressure-reducing flow regulator inserted at the motor inlet.Another key point is that the displacement of the motor is reasonably bigger than the pump so that a sufficiently wide range of pressures can be adapted.Modeling analysis and flight test results were well matched,which show the outstanding performance of this novel type actuator.

助推段火箭发动机喷焰红外辐射特性数值计算

助推段火箭发动机尾喷焰具有显著的红外辐射特性,成为天基红外预警系统重点关注的对象。以三组元固体发动机为研究对象,建立连续流域和过渡流域的尾喷焰反应流场计算模型,采用两级助推段质心弹道法确定飞行弹道,通过反向寻优法完备发动机型谱参数,基于等效单喷管法简化流场计算,基于窄谱带法和视在光线法计算尾喷焰的红外辐射特性。研究结果表明:复燃效应使得尾喷焰红外辐射光谱强度升高约20倍,谱带积分强度升高约10倍;尾喷焰红外光谱存在2.7μm和4.3μm的特征峰值;低空流域的光谱强度较高,且不同谱带内积分强度随高度的升高呈现出波动规律和暗区现象;助推段尾喷焰辐射强度差值高达3个量级,尤其在4.3μm较为明显。所得成果可为火箭在助推段的探测和识别提供一定的理论参考。

重复使用运载火箭液体动力技术发展

重复使用是未来运载火箭更新换代的技术发展趋势,是降低航天发射成本、实现规模化航天发射的有效途径。重点概述了国内外垂直起降重复使用运载火箭动力技术的发展现状,分析了垂直起降重复使用运载火箭发射和回收全任务剖面,总结了垂直起降重复使用运载火箭动力技术的特点,包括宽范围入口压力多次启动技术、大范围快速高精度推力调节技术、故障诊断及健康管理技术、状态检测与维修维护技术等。

液体火箭发动机健康监控技术研究进展

液体火箭发动机健康监控技术作为保障运载火箭安全、可靠发射的核心关键技术,经过几十年的发展,有力推动了航天事业的进步。介绍了液体火箭发动机健康监控技术中故障检测与诊断、容错控制与健康监控系统研制等技术的研究现状与发展趋势;梳理了健康监控领域面临的重难点问题,并提出相应的解决方案。分析展望了液体火箭发动机健康监控技术未来发展趋势,为从事火箭发动机健康监控技术研究的科研人员提供参考。

基于Hessian局部线性嵌入和MLP-Mixer的液体火箭发动机涡轮泵轻量化故障诊断框架

作为液体火箭发动机推进剂输送系统的关键部件,涡轮泵的运行状态直接影响着整个运载系统的性能,然而,现有的故障诊断方法往往面临特性参数选择片面及计算复杂度高等问题。针对上述局限,提出了面向涡轮泵的轻量化故障诊断框架。所提方法利用Hessian局部线性嵌入算法对信号时域、频域及时频特征进行降维,并引入一种轻量化的深度学习模型MLP-Mixer作为分类器,进而实现不同故障状态的辨识。采用某型号涡轮泵试车数据验证了所提方法的有效性,结果表明,该方法能够在保障诊断精度的同时有效降低计算复杂度,提高诊断效率。

泵入口参数对全流量补燃循环发动机动态特性影响研究

全流量补燃循环发动机性能高,并具备便于重复使用的优势,是未来重复使用运载器的最佳选择之一。在液体火箭发动机启动过程中,泵入口推进剂的压力和温度变化会对全流量补燃循环发动机动力系统的启动特性造成一定的影响。为分析其影响规律,建立了涡轮泵、预燃室、推力室、两相流和混合气体组件等动力学模型并进行求解。结果表明,随着燃料泵入口压力升高或氧化剂泵入口压力降低,涡轮泵系统参数的波动将会逐渐增大,甲烷温度和液氧温度所产生的影响要强于甲烷压力和液氧压力,而液氧的影响则强于甲烷。为动力系统中泵入口推进剂状态参数控制提供了一定的指导。

某液体火箭发动机用起动器峰值压力时间超差故障研究

针对某液体火箭发动机用起动器峰值压力时间超差故障,进行了原因分析,提出了改进措施并对其有效性进行了试验验证。结果表明:造成起动器峰值压力时间超差故障的原因为起动器内膜片与端盖间的焊接强度不足,在高温燃气冲击下膜片过早脱落、烧蚀,从而导致压力提前泄放。提出将1圈焊接改进为2圈焊接、将点焊改进为连续焊接,焊接后增加气密性及承压性能检测,以及加强削弱槽深度检测等改进措施。验证试验表明上述改进措施可有效避免起动器出现峰值压力时间超差故障。

固体火箭发动机零维内弹道点火模型与计算

点火过程是内弹道的初始阶段,但由于点火过程的复杂性以及点火机理仍然不完善,点火过程始终不能与内弹道有机结合,使得目前工程上的内弹道计算只能忽略点火过程而直接选择点火压强作为计算初始点。以零维内弹道理论为基础,建立了点火过程3个阶段,即点火诱导期、火焰传播期和充气期的简化理论模型,可以与零维内弹道有机结合,从而完成了内弹道从环境压强(而不是点火压强)开始计算的完整过程。通过实例计算与验证,该模型能够很好展示在点火阶段燃烧室压强的建立过程,并可以计算得到点火延迟时间、火焰传播时间、点火药流量等点火参数,具有较高的预示精度,满足工程计算要求。研究表明,建立的点火过程理论模型与传统零维内弹道一样计算简便快捷,并具有较好精度的工程应用化特点。研究结果对于完善固体火箭发动机内弹道理论、提高固体火箭发动机内弹道预示精度,均具有重要的实际应用意义。由于采用了简化的点火过程理论模型,该结果不能直接用于点火性能的研究,只能用于零维内弹道性能的预估与计算。

基于无迹卡尔曼滤波的液体火箭发动机故障诊断

针对火箭发动机故障数据难以获取的问题,设计了一种基于无迹卡尔曼滤波(UKF)的液体火箭发动机故障诊断算法。采用MATLAB/Simulink平台搭建了液体火箭发动机故障仿真模型,实现发动机正常运行仿真和预燃室氧阀门故障、氧主泵汽蚀、氢主涡轮叶片脱落3种故障仿真。将正常运行仿真值与设计值、试车值进行了对比。结果表明:模型参数与设计值最大误差不超过5%,仿真精度较高;仿真参数变化趋势与试车值基本一致,且稳态值误差较小。使用UKF算法求取发动机正常运行阈值范围,并对故障序列进行滤波处理,若故障数据连续3次超出阈值区间,且在0.1 s内有至少2个涡轮泵发出报警,则判定故障发生,故障发生时间为第2个涡轮泵报警时间。使用设计算法对3种故障序列进行诊断,判定故障发生时间分别为20.08 s、20.05 s、20.18 s。相比于传统红线阈值算法,文中所设计算法响应更为及时,且误报率较低。

HAN基单组元推进剂热分解过程的分子动力学模拟

为揭示非催化点火方式的硝酸羟胺(HAN)基单组元液体火箭发动机内推进剂的反应机理,采用分子动力学模拟方法,在ReaxFF/lg力场下对HAN基推进剂热分解机理及配方影响作用机制开展研究。计算结果表明:推进剂热分解过程存在两个阶段。第一个阶段为吸热阶段,推进剂内硝酸羟胺和硝酸肼氢键断裂,分解生成羟胺、肼和硝酸,吸热阶段主要受推进剂内氢键个数影响;第二个阶段为推进剂分解反应阶段,由硝酸和羟胺的分解所引发,生成NH_(2)、NO_(2)和OH。OH为主要的氧化性物质,与肼、甲醇反应,生成大量的水。肼在推进剂中的分解主要依靠与OH反应脱氢,生成N_(2)H_(3),并最终分解形成N_(2)和H_(2)。推进剂配方仅对与OH的反应有显著影响。降低甲醇的含量,能够显著提升燃料的反应速率,同时促进肼分子的反应脱氢,提高推进剂初始分解速率;提高硝酸羟胺的含量能够促进甲醇的分解,但受肼分解反应速率较低的影响,推进剂整体分解速率降低。