The Effect of Ignition Parameters on the Combustion Characteristics of an Aviation Piston Engine

A cylinder combustion simulation model was established for a two-stroke aviation piston engine used in a small unmanned aerial vehicle. The influence of different ignition system parameters on the combustion process of aviation kerosene was studied using this model. The research results showed that under the working conditions of 5500 r/min and 50% throttle opening, as the ignition energy increased, the peak values of average cylinder pressure and average temperature increased, and the combustion duration shortened, The advance of the combustion center of gravity increases the tendency of the engine to knock. Under the same operating conditions, as the ignition timing advances, the peak values of average pressure and average temperature in the cylinder increase, gradually approaching the top dead center, and the tendency of engine detonation increases more significantly.

120-ton Thrust Liquid-Oxygen/Kerosene Engine Passed Acceptance Test

On May 28, the 120-ton thrust liquid-oxygen/kerosene engine developed by the Academy of Aerospace Liquid Propulsion Technology (AALPT) passed the acceptance test organized by China National Space Administration (CNSA). The 120-ton thrust liquid-oxygen/kerosene engine is a non-pollution, non-toxic, high performance and reliable basic pro-

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.

Gas film/regenerative composite cooling characteristics of the liquid oxygen/liquid methane (LOX/LCH4) rocket engine

The thermal protection of rocket engines is a crucial aspect of rocket engine design.In this paper,the gas film/regenerative composite cooling of the liquid oxygen/liquid methane(LOX/LCH4)rocket engine thrust chamber was investigated.A gas film/regenerative composite cooling model was developed based on the Grisson gas film cooling efficiency formula and the one-dimensional regenerative cooling model.The accuracy of the model was validated through experiments conducted on a 6 kg/s level gas film/regenerative composite cooling thrust chamber.Additionally,key parameters related to heat transfer performance were calculated.The results demonstrate that the model is sufficiently accurate to be used as a preliminary design tool.The temperature rise error of the coolant,when compared with the experimental results,was found to be less than 10%.Although the pressure drop error is relatively large,the calculated results still provide valuable guidance for heat transfer analysis.In addition,the performance of composite cooling is observed to be superior to regenerative cooling.Increasing the gas film flow rate results in higher cooling efficiency and a lower gas-side wall temperature.Furthermore,the position at which the gas film is introduced greatly impacts the cooling performance.The optimal introduction position for the gas film is determined when the film is introduced from a single row of holes.This optimal introduction position results in a more uniform wall temperature distribution and reduces the peak temperature.Lastly,it is observed that a double row of holes,when compared to a single row of holes,enhances the cooling effect in the superposition area of the gas film and further lowers the gas-side wall temperature.These results provide a basis for the design of gas film/regenerative composite cooling systems.

Numerical analysis of reactive turbulent flow in the thrust chamber of RD-108 engine rocket

Combustion chamber modeling and simulation of the liquid propellant engine with kerosene as fuel and liquid oxygen as an oxidizer in the turbulent flow field are performed by CFD technique.The flow is modeled as Single-phase in steady state and using RNG k-ε turbulence model.Simulation results are validated by experimental data of thrust,special impulse and combustion chamber pressure.By comparing t.^wo reaction models of finite rate chemistry and frozen model with experimental data,it is concluded that finite rate chemistry has acceptable results.The optimum value of equivalence ratio(oxidizer to fuel ratio)per reaction and operational parameters of the engine which maximize thrust and special impulse are determined.

膨胀循环氢氧发动机火炬点火系统方案研究

针对膨胀循环氢氧发动机多次点火需求,开展了火炬式电点火系统方案论证和仿真研究,明确了较为合理的低压火炬式电点火系统方案,并完成整机级试验验证。结果表明,氢主阀打开瞬间点火室混合比波动较大,可能造成结构烧蚀;从氢涡轮前引气氢、氧泵后引液氧的方案烧蚀风险较小,但对发动机起动和稳态特性有一定影响。试验验证了仿真分析结果,实现了中国液体火箭发动机首次低压火炬式电点火起动,初步表明点火系统方案可行。

N235从废催化剂沉钒废液中回收钒

这是一篇冶金工程领域的论文。针对陕西某炼锌厂废催化剂的沉钒废液,通过溶剂萃取法除杂并回收沉钒废液中的钒,考查N235体积分数、萃取相比、萃取时间、萃取级数等对钒萃取率的影响。结果表明:采用30%N235+5%TBP+65%的磺化煤油的萃取体系经过四级逆流萃取,萃取相比V_(O)/V_(A)=2∶1,萃取时间t=5 min,钒的萃取率为95.68%;反萃取剂Na_(2)CO_(3)体积分数为5%,反萃相比V'_(O)/V'_(A)=4∶1,反萃时间t=4 min,经三级逆流反萃取,钒的反萃取率为98.25%。

低压环境下RP-3航空煤油自燃特性研究

开展了低压环境下RP-3航空煤油的自燃特性研究,测试了101 kPa、80 kPa、60 kPa、40 kPa、20 kPa五种压力环境下航空煤油自燃点及着火延迟时间数据。结果表明,随着环境压力降低,自燃点升高,并基于谢苗诺夫热自燃理论,建立了耦合压力参数的自燃点预测模型。分析了环境压力对着火延迟时间的影响机制,建立了不同环境压力下的着火延迟时间预测模型。分析了GB/T 5332—2007标准在低压环境下测试存在的问题,并提出了相关改进方法。

Improving the performance of LOX/kerosene upper stage rocket engines

Improved liquid rocket engine cycles were proposed and analyzed via comparison with existing staged combustion and gas-generator cycles.The key features of the proposed cycles are regenerative cooling of thrust chamber by oxygen and subsequent use of this oxygen for driving one or two oxygen pumps.The fuel pump(s)are driven in a conventional manner,for example,using a fuel-rich gas-generator cycle.Comparison with staged combustion cycle based on oxygen-rich pre-burner showed that one of the proposed semi-expander cycles has a specific impulse only on 0.4%lower while providing much lower oxygen temperature,more efficient tank pressurizing system and built-in roll control.This semi-expander cycle can be considered as a more reliable and cost-effective alternative of staged combustion cycle.Another semi-expander cycle can be considered as an improvement of gas-generator cycle.All proposed semi-expander cycles were developed as a derivative of thrust chamber regenerative cooling performed by oxygen.Analysis of existing oxygen/kerosene engines showed that replacing of kerosene regenerative cooling with oxygen allows a significant increase of achievable specific impulse,via optimization of mixture ratio.It is especially the case for upper stage engines.The increasing of propellants average density can be considered as an additional benefit of mixture ratio optimization.It was demonstrated that oxygen regenerative cooling of thrust chamber is a feasible and the most promising option for oxygen/kerosene engines.Combination of oxygen regenerative cooling and semi-expander cycles potentially allows creating the oxygen/kerosene propulsion systems with minimum specific impulse losses.It is important that such propulsion systems can be fully based on inherited and well-proven technical solutions.A hypothetic upper stage engine with thrust 19.6 kN was chosen as a prospective candidate for theoretical analysis of the proposed semi-expander cycles.The newly-developed software RECS was used for the comparative analysis of engine cycles.

LOX/LCH_4变推力发动机技术初步研究

对国内外变推力发动机和LOX/LCH4发动机的研究进展进行了总结,在此基础上,提出了一种LOX/LCH4变推力发动机系统方案。在深入分析的基础上,对此方案进行了功率平衡和推力室传热计算,结果表明该系统方案完全能够实现10:1推力变比。LOX/LCH4变推力发动机可以广泛应用于多种运载器和航天器中,对我国探月及后续的载人登月工程均可以提供技术支持,对LOX/LCH4发动机的技术发展和未来的载人登陆火星等任务都具有深远影响。

利用Cre/lox重组系统建立番茄基因工程雄性不育恢复系

【目的】利用Cre/lox重组系统具有的重组删除特性建立番茄工程恢复系,特异删除F1中的雄性不育基因恢复其育性。【方法】将TA29-Barnase雄性不育基因表达盒置于两个同向lox位点之间并与NPTⅡ基因、Bar基因融合后获得植物表达载体pBinBarloxTABn,转化番茄获得雄性不育转基因植株。Cre基因在CaMV35S启动子的驱动下转入番茄获得工程恢复系。两者在开花时进行杂交,利用Cre重组酶删除F1中的TA29-Barnase不育基因表达盒使育性恢复。【结果】利用NPTⅡ作为转化筛选标记基因获得了番茄雄性不育转基因植株。转基因植株中的Bar基因能正常表达,真叶叶盘在含PPT3mg·L-1(phosphinothricin)分化培养基上能分化愈伤组织及芽;真叶具有抗PPT20mg·L-1浓度以上的能力。获得的TA29-Barnase转基因植株表现雄蕊退化、无花粉产生或产生少量形状畸形且无生活力的花粉。雄性不育植株自花授粉不能坐果,用非转基因保持系花粉授粉后,果实正常膨大结籽,杂交后代对除草剂Basta的抗性按1﹕1分离。不育植株与Cre转基因工程恢复系杂交后,果实也正常膨大结籽。对不育植株与Cre转基因工程恢复系杂交后代进行分子检测,结果发现同时含Bar基因和Cre基因F1植株中的TA29-Barnase雄性不育基因被精确删除。TA29-Barnase基因删除植株育性被恢复,能正常开花结果。【结论】利用Cre/lox重组系统建立的Cre工程恢复系成功将番茄F1代中的不育基因删除,恢复了F1的育性。该研究结果为植物基因工程雄性不育系的育性恢复提供了一条新的途径。

飞机撞击安全壳燃油泄漏燃烧数值模拟研究

为研究飞机撞击核电厂安全壳后引发燃烧对安全壳的影响,采用Fluent模拟了航空煤油替代燃料在安全壳内部和外部的燃烧过程,分析了安全壳不同位置处的火焰温度变化情况。结果表明,在开始阶段,燃油泄漏时间比较短,燃油缓慢蒸发汽化,燃烧发展过程以扩散蔓延为主,高温区域主要分布在安全壳侧壁面和底面。随着时间推移,液面蒸发速度加快,火焰高度呈现纵向发展的态势,最后在顶部形成较为均匀的温度场。安全壳内部燃烧最高温度可以达到2229 K,外部燃烧最高温度为1308 K。此外,撞击位置越高,安全壳顶部会越早出现高温区域,而较低位置处由于液池的堆积缓慢,燃油蒸发速率低,温度上升相对较慢。区别于内部燃烧,外部燃烧火焰不会波及安全壳顶部中心位置。

甲醇喷入对主燃烧室燃烧性能的影响

为探究甲醇水溶液喷入对航空发动机主燃烧室燃烧性能的影响,通过迭代理论计算,得到喷入不同甲醇水溶液后的主燃烧室进口条件;再利用FLUENT软件,研究了不同甲醇水溶液参数对航空发动机主燃烧室燃烧性能的影响。结果表明:甲醇水溶液喷入会降低整体燃烧温度,且随着甲醇替代率和含水量的增加,燃烧室中最高燃烧温度、出口平均温度和燃烧效率均逐步降低,NO排放量显著降低;在保证甲醇和航空煤油的燃烧总热值相等的条件下,主燃烧室温升总体差距较小。

高温高压环境下RP-3航空煤油单液滴的加热与蒸发特性研究

RP-3航空煤油是当前国内最常用的商用喷气燃料,煤油液滴在航空发动机燃烧室中的蒸发直接影响燃料的雾化效果、空燃混合气的形成和燃烧质量。本文以单个RP-3航空煤油液滴为研究对象,选取正十二烷、2,5-二甲基己烷、甲苯作为替代燃料,提出了一个考虑自然对流效应的高温高压环境下多组分液滴蒸发模型。利用自主搭建的试验装置得到了环境压力为1MPa、环境温度为473~673K下RP-3煤油单液滴在蒸发过程中的液滴直径变化。模型预测结果与试验结果的对比验证了模型的准确性。通过模型预测了不同环境参数下三组分替代物液滴直径、内部温度分布、各组分质量分数分布和液滴寿命等参数的瞬态变化,定量分析了不同高温条件下环境压力对单液滴蒸发特性的影响。结果表明,液相内部的传热传质会影响多组分液滴的蒸发速率,且液相扩散阻力造成了液相内部组分质量分数与温度空间分布的不均匀性。环境压力对RP-3煤油液滴蒸发寿命的影响随环境温度的变化而变化。当环境温度低于正十二烷的临界温度(658.25K)时,液滴寿命与环境压力的关系不是单调的,液滴寿命随环境压力的增加先增后减;而当环境温度超过658.25K时,液滴寿命随环境压力的升高而单调减小。这是因为在高温高压环境中,环境压力的升高能显著增大自然对流传热传质强度,而自然对流超过一定强度时,能明显促进液滴蒸发。上述研究有利于认识液滴内部组分扩散过程,从源头上为未来高性能低污染发动机的优化设计提供依据与参考。

RP-3煤油作为柴油机燃料在不同工况下的燃烧特性与性能研究

为研究不同转速和不同海拔下RP3-煤油的燃烧过程和性能,本文利用RP-3煤油和柴油燃烧与性能台架试验平台,开展了柴油机燃烧过程和性能的试验研究,在分别改变发动机转速和海拔高度条件下,围绕柴油机的燃烧特性和性能开展了RP-3煤油的台架试验,实验结果表明,柴油发动机在不同转速和海拔下燃用RP-3煤油的燃烧特性和性能变化规律和燃用柴油的变化趋势一致,RP-3煤油可作为柴油机的应急燃料。

Effect of dicarboxylic acid esters on the lubricity of aviation kerosene for use in CI engines

To reduce their fuel related logistic burden,North Atlantic Treaty Organization(NATO)Armed Forces are advancing the use of a single fuel for both aircraft and ground equipment.To this end,F-34(the commercial equivalent is Jet A-1)is replacing distillate diesel fuel in many applications.However,tests conducted with this kerosene type on high frequency reciprocating rig showed that this type of fuel causes unacceptable wear.This excessive wear is caused by the poor lubricity of aviation fuel.In order to make this type of fuel compatible with direct injection compression engines,seven di-carboxylic acid esters have tested to improve the lubricity of kerosene.Tribological results showed that all esters tested in this series of experiments seem to be suitable for increasing the kerosene lubricity to a satisfactory level.

Operation of a Rotary-valved Pulse Detonation Rocket Engine Utilizing Liquid-kerosene and Oxygen

The pulse detonation rocket engine （PDRE） requires periodic supply of oxidizer, fuel and purge gas. A rotary-valve assembly is fabricated to control the periodic supply in this research. Oxygen and liquid aviation kerosene are used as oxidizer and fuel respectively. An ordinary automobile spark plug, with ignition energy as low as 50 mJ, is used to initiate combustion. Steady operation of the PDRE is achieved with operating frequency ranging from 1 Hz to 10 Hz. Experimentally measured pressure is lower than theoretical value by 13% at 1 Hz and 37% at 10 Hz, and there also exists a velocity deficit at different operating frequencies. Both of these two phenomena are believed mainly due to droplet size which depends on atomization and vaporiza-tion of liquid fuel.

Numerical study of operational processes in a GOx-kerosene rocket engine with liquid film cooling

Combustion process inside kerosene-GOx rocket combustor with kerosene Alm cooling is studied,and a modeling approach is proposed.The paper suggests to use the Lagrangian particle tracking technique to model fuel film behavior while the continuous fluid is simulated via the Navier-Stokes system of Favre-averaged equations.The approach is validated over the 12 experimental regimes by the criterions of characteristic velocity and pressure,ence on the adiabatic wall temperatures and relatively low impact on the pressure.In general,phenomena,the calculation of operational processes becomes fast and robust yet precise en-the design process.

Performance, emission and combustion characteristics of DI diesel engine running on blends of honne oil/diesel fuel/kerosene/DMC

Honne oil(tamanu)(H),a non-edible vegetable oil is native for northwards of Northern Marianas islands and the Ryukyu Islands in southern Japan and westward throughout Polynesia.It has remained as an untapped new possible source of alternative fuel that can be used as diesel engine fuel.Literature pertaining to use of vegetable oil in diesel engine with kerosene and dimethyl carbonate(DMC)is scarce.The present research is aimed to investigate experimentally the performance,exhaust emission and combustion characteristics of a direct injection(DI)diesel engine,typically used in agricultural sector,over the entire load range,when fuelled with neat diesel(ND)and blends of diesel fuel(D)/DMC/H/kerosene(K).DMC/D/H/K blends have a potential to improve the performance and emissions and to be an alternative to ND.Experiments have been conducted when fuelled with H20(20%H+80%D),HK(20%H+40%K+40%D)and HKD5(20%H+40%K+35D+5%DMC)to HKD15 in steps of 5%DMC keeping H and K percentages constant.The emissions(CO,HC and smoke density(SD))of fuel blend HKD15 are found to be lowest,with SD dropping significantly.The NOx level is slightly higher with HKD5 to HKD15 as compared to ND.The brake thermal efficiency of HKD5 to HKD15 is same and it is higher than that of ND.There is a good trade off between NOx and SD.Peak cylinder pressure and premixed combustion phase increases as DMC content increase.

二冲程点燃式航空煤油发动机燃油消耗率及氮氧化物排放特性分析

针对某二冲程火花点火式活塞发动机燃烧航空煤油时燃油消耗率及氮氧化物排放特性的研究,采用GT-Power软件进行了数值模拟分析。首先建立了该发动机的整机模型,并利用发动机转速为6000r/min时的全负荷工况的缸内压力的数值模拟结果以及在3500r/min到6500r/min转速范围内的扭矩及功率等数值模拟结果分别跟试验数据进行对比分析,验证了GT-Power数值模拟计算模型的正确性。然后采用该模型对该发动机工作过程中的压缩比、空燃比、点火提前角、进气压力、进气温度等参数的变化对燃油消耗率以及氮氧化物生成量的影响进行了模拟计算。结果表明:在6000r/min工况下,压缩比增大使燃油消耗率降低,进气压力和进气温度增大均使得燃油消耗率升高,空燃比和点火提前角增大均使燃油消耗率呈现出先减小后增大的特点,燃油消耗率在空燃比为15.5和点火提前角为25°CA时出现了极值点;压缩比、进气压力、进气温度和点火提前角增大均使氮氧化物生成量增多,空燃比增大使得氮氧化物生成量出现了先增多后减少的现象,在空燃比为15.5时氮氧化物生成量达到峰值。