Damage localization effects of the regeneratively-cooled thrust chamber wall in LOX/methane rocket engines

To investigate the damage localization effects of the thrust chamber wall caused by combustions in LOX/methane rocket engines, a fluid-structural coupling computational methodology with a multi-channel model is developed to obtain 3-demensioanl thermal and structural responses.Heat and mechanical loads are calculated by a validated finite volume fluid-thermal coupling numerical method considering non-premixed combustion processes of propellants. The methodology is subsequently performed on an LOX/methane thrust chamber under cyclic operation. Results show that the heat loads of the thrust chamber wall are apparently non-uniform in the circumferential direction. There are noticeable disparities between different cooling channels in terms of temperature and strain distributions at the end of the hot run phase, which in turn leads to different temperature ranges, strain ranges, and residual strains during one cycle. With the work cycle proceeding, the circumferential localization effect of the residual strain would be significantly enhanced. A post-processing damage analysis reveals that the low-cycle fatigue damage accumulated in each cycle is almost unchanged, while the quasi static damage accumulated in a considered cycle declines until stabilized after several cycles. The maximum discrepancy of the predicted lives between different cooling channels is about 30%.

Thermal-structural analysis of regeneratively-cooled thrust chamber wall in reusable LOX/Methane rocket engines

To predict the thermal and structural responses of the thrust chamber wall under cyclic work,a 3-D fluid-structural coupling computational methodology is developed.The thermal and mechanical loads are determined by a validated 3-D finite volume fluid-thermal coupling computational method.With the specified loads,the nonlinear thermal-structural finite element analysis is applied to obtaining the 3-D thermal and structural responses.The Chaboche nonlinear kinematic hardening model calibrated by experimental data is adopted to predict the cyclic plastic behavior of the inner wall.The methodology is further applied to the thrust chamber of LOX/Methane rocket engines.The results show that both the maximum temperature at hot run phase and the maximum circumferential residual strain of the inner wall appear at the convergent part of the chamber.Structural analysis for multiple work cycles reveals that the failure of the inner wall may be controlled by the low-cycle fatigue when the Chaboche model parameter c3= 0,and the damage caused by the thermal-mechanical ratcheting of the inner wall cannot be ignored when c3〉 0.The results of sensitivity analysis indicate that mechanical loads have a strong influence on the strains in the inner wall.

Thermo-structural analysis of regenerative cooling thrust chamber cylinder segment based on experimental data

To evaluate the structural failure risk of the regenerative cooling thrust chamber cylinder segment,a Finite Element Method(FEM)based on experimental data was developed.The methodology was validated and utilized to reveal the thermal response and the nonlinear deformation behavior of the cylinder segment phase by phase.The conclusions of the research are as follows:The 2 D heat flux distribution caused by the injector determines the uneven temperature distribution on the gas-side wall and leads to the temperature disparity between various cooling channels;The reason for the accumulation of residual strain is that the tensile strain generated in the post-cooling phase is greater than the compressive strain produced in the hot run phase;Through the single-cycle simulation,two potential failure locations with conspicuous deformations were found,but it is difficult to determine which point is more dangerous.However,the multi-cycle thermo-structural analysis gives the evolution of the stress-strain curve and gradually discloses that the low-temperature corner of a particular channel is the most likely location to fail,rather than the maximum residual strain point of the gas-side wall.The damage analysis for dangerous point indicates that the quasistatic damage accounts for the majority of the total damage and is the main factor limiting the service life.

姿控推力室隔热框断裂故障分析及改进

针对某姿控动力系统推力室在力学环境试验过程中发生的隔热框断裂故障,对故障部位进行断口分析和结构强度分析,发现在高量级随机振动条件下隔热框支撑肋根部存在严重的应力集中,导致发生疲劳断裂。通过改进隔热框支撑肋结构,经强度分析和推力室力学环境试验验证,隔热框未再发生类似故障,表明改进措施方案可靠有效。

重复使用火箭发动机推力室疲劳寿命研究进展

再生冷却推力室内壁的热-机械疲劳失效严重影响重复使用液体火箭发动机的可靠性和使用寿命,疲劳分析在内壁损伤机理研究、寿命预测和结构优化设计中具有重要作用。简要回顾了推力室再生冷却结构热-机械疲劳分析方法的发展历程,重点围绕材料本构关系、热-力响应计算和疲劳寿命模型,对比梳理已有方法,讨论其特点及应用。基于研究进展与工程需求,从全服役周期瞬态载荷环境、材料本构关系、热-机械损伤模型及验证、基体与涂/镀层耦合失效分析和基于有限数据的工程方法等方面给出了进一步研究的方向和建议。

液体火箭发动机热试车启动中导流锥对燃气管路流动特性影响研究

双推力室液体火箭发动机启动过程中,若出现两支管流量分配不均等现象,极易引起点火失败,造成重大损失。因此,燃气管路分叉处内部流动特性和在分叉处布置导流锥对改善流动特性影响的研究具有重要意义。本文针对某双推力室液体火箭发动机热试车启动过程中的燃气管路,以试验数据作为边界条件,开展了瞬态流动数值仿真研究。结果表明,火箭发动机热试车启动过程中,燃气管路流动呈现出4个典型阶段,分别为点火前的平稳期、点火后的一次上升期、下降期和二次上升期。在启动过程中,无导流锥时,导流罩进口存在预旋回流区、一侧出口存在滞止回流区,导流罩与燃气支管衔接处内侧存在转弯回流区,三者相互作用是造成两支管间压力分布不对称及出口质量流量分配不平衡的主要原因;有导流锥时,预旋回流区被导流锥约束而缩小,滞止回流区消失。有导流锥与无导流锥时相比,在启动过程中约0.2 s与0.6 s时刻,两支管对称测点压差均值分别降低约80.0%与80.0%,两支管出口质量流量差值分别降低约55.0%与80.8%。导流锥有效改善了流动特性,使得两支管压力分布的对称性提高,流量分配平衡性增强。导流锥对双推力室液体火箭发动机稳定性提高有重要作用。

复杂力热载荷下推力室内壁失效机理研究

大推力氢氧火箭发动机在经过多次试车后,推力室内壁会产生不同程度的裂纹,严重影响发动机的工作可靠性。为了分析复杂力热载荷下推力室内壁的失效机理,本文根据发动机实际工作过程涉及预冷-工作-后冷-松弛四个阶段,分别计算了经过单次和多次工作循环的内壁应力应变情况,并针对试车分解后的内壁材料进行断貌分析和金相检查。仿真与材料分析结果表明:内壁面的失效机理为疲劳和棘轮共同作用下导致通道中心点处残余拉应变不断累积,不断向外鼓起,而内壁材料在高温下会出现晶粒粗化和再结晶现象,导致材料性能出现不可逆的下降,加速了结构失效,最终产生裂纹。

变形高温合金在液体火箭发动机中的应用进展及展望

变形高温合金以其良好的耐高温、抗氧化、抗热腐蚀性能和较好的冷、热加工性,在液体火箭发动机推力室身部、涡轮壳体、涡轮转子等热端部件中得到了广泛的应用。通过查阅文献,综述了国内外变形高温合金及热加工技术发展现状、液体火箭发动机热端构件对高温合金性能需求、变形高温合金在国内外著名液体火箭发动机中的应用情况。结合液体火箭发动机可回收、高性能、轻量化、低成本的发展趋势,总结了变形高温合金在液体火箭发动机领域的主要发展趋势,包括研发针对液体火箭发动机服役工况的高温合金材料、改进热加工工艺,从而提升高温合金性能、降低高温合金构件制造成本;研发和推广耐高温轻质金属间化合物、降低热端构件质量。

基于相场模型的再生冷却推力室热机疲劳寿命分析

为了分析再生冷却推力室在服役过程中的应力/应变情况,研究循环热力载荷下推力室的变形与疲劳失效行为,建立热-弹-塑性耦合的疲劳断裂相场模型,并计算断裂序参量的演化过程,预测推力室结构的热机疲劳寿命。通过热传导方程计算结构的温度分布及热应变,根据应力平衡方程和相场演化方程计算热循环作用下结构中应力/应变和序参量演化,根据序参量达到临界值的循环数预测结构的热机疲劳寿命。结果表明:推力室内壁下表面中心点最先断裂失效,疲劳寿命约为91次。循环温度载荷作用下,内壁下表面中心点处残余拉伸应变不断累积,导致表面塌陷及内壁变薄,最终破坏。利用相场疲劳断裂模型研究推力室结构的热机疲劳失效行为,为预测发动机推力室结构疲劳寿命及辅助发动机再生冷却通道优化设计提供了新思路与方法。

Numerical Analysis and Modelling of a 100 N Hypergolic Liquid Bipropellant Thruster

This study focuses on the stepwise procedure involved in the development of a numerical model of a bi-propellant hypergolic chemical propulsion system using key features and performance characteristics of existing and planned (near future) propulsion systems. The study targets specific impulse of 100 N delivery performance of thrust chambers which is suitable for primary propulsion and attitude control for spacecraft. Results from numerical models are reported and validated with the Rocket Propulsion Analysis (RPA) computation concept. In the modelling process, there was proper consideration for the essential parts of the thruster engine such as the nozzle, combustion chamber, catalyst bed, injector, and cooling jacket. This propulsion system is designed to be fabricated in our next step in advancing this idea, using a combination of additive manufacturing technology and commercial off the shelf (COTS) parts along with non-toxic propellants. The two non-toxic propellants being considered are Hydrogen Peroxide as the oxidiser and Kerosene as the fuel, thus making it a low-cost, readily available and environmentally-friendly option for future microsatellite missions.

Hardware-in-loop simulation on hydrostatic thrust bearing worktable pose

A controllable hydrostatic thrust bearing was presented to improve rigidity. The bearing worktable poses were controlled by coupling oilfilm thickness of four controllable chambers. The chamber flow can be regulated by electro hydraulic servo valve-control variable pump according to the surface roughness, load, cutting force, and thermal effects of worktable. The mathematical models of the controllable chamber flow, servo variable mechanism and controller were built. The pose control model was established, which contained the kinematics positive and negative solution and control strategy of feedforward and hydraulic cylinder position feedback. Hardware-in-loop simulation experiment was carried out on the electro hydraulic servo test bench by means of the non-linear relation of film thickness and hydraulic cylinder displacement. Hardware-in-loop simulation experiment results show that the controllable bearings exhibit high oilfilm rigidity, the rising time is 0.24 s and the maximum overshoot is 2.23%, and can be applied in high precision heavy machine tool.

连续变推力离子推力器双荷离子特性分析与诊断

离子推力器束流离子中的双荷离子在制约栅极组件工作寿命的同时也影响到推力器实际推力的大小,其在总束流中的占比直接决定了推力器寿命、推力等关键性能指标的符合性。为准确、快速研判10 cm氙离子推力器在宽范围推力调节过程中的双荷离子占比,利用放电室经验模型,分析了推力器变推力调节过程中双荷离子的变化特性及其影响因素,结合实际工作参数计算得到了不同推力工况点下双荷离子的理论占比。在此基础上,采用E×B探针诊断系统测试获得了相应推力工况点下双荷离子的实验占比,并将理论计算结果与实验测试结果进行了对比。研究结果表明:离子推力器放电室内双荷离子的占比是关于推力器工质利用率等性能参数及原初电子与麦氏电子间的密度比、电子温度等相关等离子体参数的函数;在变推力调节过程中,随着放电室内阳极功率的增加,束流中的双荷离子比例不断上升,且其引出束流中双荷离子比例分布呈现出强烈的非线性分布,整体表现为伴随增长的趋势。研究为离子推力器在轨控制策略的优化设计及性能评估提供了技术支持。

液氧-甲烷发动机点火器接口过度烧蚀问题研究

针对某液氧-甲烷发动机试车中出现的点火器与管路接口过度烧蚀问题,进行了原因分析及试验验证,提出改进措施并对其进行试验验证。结果表明:接口倒台阶和缝隙过大是造成过度烧蚀的原因。采用“突变式”变径结构代替“斜面过度”变径结构,可避免点火器与管路内径公差设计不合理及装配不对位造成的倒台阶问题;并且,将石墨垫圈厚度由4.0~4.5 mm调整为2.6~3.0 mm,可使压紧后接口缝隙小于0.1 mm。试验表明改进措施有效。

10 cm考夫曼型离子推力器放电室关键参数优化

放电室构型设计是离子推力器结构设计的基础与核心,直接影响到放电室工作能效及整机工作寿命。针对新型航天器在轨飞行任务对大推力、长寿命连续变推力离子推力器的应用需求,探究了影响10 cm离子推力器整机效能的放电室关键参数因子,揭示了发散场放电室的磁场发散度、电子通道面积及阴极位置等敏感参数对放电室性能的影响作用关系。开展了10 cm离子推力器放电室参数构型的优化与验证。结果表明:在不改变整机结构的情况下,通过优化放电室关键参数,10 cm离子推力器最大输出推力由20 mN提升至25 mN,提升近25%,推力调节范围由1~20 mN扩展至1~25 mN,全范围内推力分辨率均优于50μN,且推力器在20 mN最佳工作点的阳极电压由43.5 V降至38.4 V,放电损耗由345 W/A降至308 W/A,预估整机寿命将由15000 h提升至17500 h。研究为推动10 cm离子推力器的在轨扩展应用提供了一定的技术支撑。

氢氧火箭发动机助推器结构分析及寿命预测

After several trial runs,penetrating cracks appeared in the thrust chamber wall of a hydrogen-oxygen rocket engine,which will affect the service life and performance of the engine.It is necessary to reduce the wall heat flux by injection element mixture ratio biasing or propellant films to prolong the life of the liner wall.In this paper,the deformation of three types of inner walls was calculated under cyclic mechanical loading,and the stress-strain response and the fatigue life of the inner walls were compared.The results show that the bottom midpoint of the gas side channel,with the largest residual strain,is the most prone to failure.In addition,the adoption of injection element mixture ratio biasing or film cooling can greatly increase the life of the inner wall,and the improvement effect of the two measures is similar.

高压补燃液体火箭发动机推力室冷却技术及结构优化

The LM-5B launch vehicle has successfully completed four missions.Eight high-pressure staged combustion LOX/kerosene engines(YF-100)are equipped in the four boosters of the LM-5B,two in each booster.The YF-100 engine adopts various cooling techniques to ensure cooling,including a metal thermal barrier coating,multiple liquid film cooling slots,spiral milled regenerative cooling channels with high aspect ratio,a non-weld forming thrust chamber and an optimal cooling flow path design.In addition,the 480-ton LOX/kerosene engine for China’s future heavy-lift launch vehicle LM-9 will be larger in size,which makes it more difficult to be developed and will have more strict requirements in the cooling process.The main differences between the LM-5B and LM-5 are briefly described in this paper and the development process and working characteristics of YF-100 engines are introduced.The advantages and disadvantages of main cooling methods used in the thrust chambers of high-thrust liquid propellant engines are also described.Finally,the future challenges and countermeasures in cooling technology for China’s high-thrust LOX/kerosene engines and future reusable rocket engines are also presented.

基于3D打印的过氧化氢/煤油再生冷却推力室设计及试验

为了实现过氧化氢/煤油推力室关键技术的快速验证,开展了基于3D打印快速制造的推力室设计及试验。首先针对设计指标,充分利用3D打印零件少、连接强度高、结构质量轻等优点,完成过氧化氢/煤油推力室的设计;然后利用商用软件Fluent对设计方案进行快速燃烧数值仿真,获得设计工况推力室压强、温度、流线以及各组分质量分数分布等,并对燃烧性能进行分析,完成设计方案的优化;最后通过长程热试车对推力室的性能进行考核。结果表明:3D打印推力室结构可靠性高、冷却性能好、燃烧性能高,满足设计指标要求,相比于传统机械加工工艺,缩短50研制周期,降低40制造成本,减少50零件数量,减轻20质量。充分展现了3D打印技术在推力室关键技术验证阶段的周期短、成本低、可靠性高等优势。

基于增材制造的液氧/煤油推力室喷注器分析

为了实现液体火箭发动机推力室喷注器3D打印技术的工程应用,从方案设计、打印制造、质量控制、试验验证多个方面对3D打印喷注器进行了研究。通过一体化集成设计和整体制造,喷注器零件数量由16个减至1个,21条焊缝全部取消,大幅提高产品结构的固有可靠性,同时降低了工艺难度,实现了设计方案的快速验证和迭代;通过液流试验和质量检查,保证了产品质量,在此基础上总结了3D打印喷注器研制全流程质量控制方法。热试结果表明打印喷注器的性能与机加喷注器的性能相当,其中燃烧效率达到95以上,验证了液体火箭发动机复杂结构喷注器3D打印技术的可行性,为实现液体火箭发动机推力室全3D打印奠定了基础。

冷却环带结构形态及离心角度对流场的影响

为了优化冷却环带局部喷注结构的型面参数,延长液膜存续寿命,采用广义超临界流体定义方法,对高压液氧煤油火箭发动机推力室第一环带的液膜流动特性进行了数值研究。分析了喷注结构的内边弧度半径和冷却剂的入射离心角度对流线发展、介质分布、湍流动能等的影响。结果表明,受超临界流体物性参数的突变影响,入口上、下游壁面处均会出现涡流效应,阻碍当地对流换热作用,阻断液膜铺展并引起液壁分离现象,加剧气液卷吸掺混;增大内弧半径可扩大液膜有效区域,半径为2.0mm时,有效区占比为59.2%;提高入射离心角可显著减弱涡流效应;2.0mm的内弧半径和84°的入射离心角为最佳工况组合,采用该方案可大幅优化液膜的稳定性和顺滑性。

电磁阀节流孔板与过滤网的间隙对推力器室压的影响

为解决某单组元推力器在试车试验过程中出现室压偏低的问题,通过运用Fluent软件仿真分析与试验验证的方法,分析出某电磁阀入口安装的节流孔板与过滤网之间的间隙会影响电磁阀流阻,从而影响单组元推力器室压。研究表明:将电磁阀节流孔板与过滤网之间的间隙增大能够有效地解决单组元推力器室压降低的问题,具有实用性。同时也为其他推力器的设计与试验提供了有益的借鉴。