煤油氧气脉冲爆震火箭发动机爆震特性

脉冲爆震火箭发动机(PDRE)是一种利用脉冲式爆震波产生高温、高压燃气发出的冲量来产生推力的推进系统.与常规液体火箭发动机相比,脉冲爆震火箭发动机具有更高的性能,并且结构更简单.本文以航空煤油为燃料、氧气为氧化剂、压缩氮气为隔离气体,并利用电磁阀控制燃料、氧化剂和隔离气体的间歇式供给.利用低的点火能量(50mJ),在内径50mm,长度1.1m的爆震管内进行了大量的多循环爆震试验,研究煤油氧气电磁阀脉冲爆震火箭发动机的爆震波特性.研究结果为进一步研究气液两相多次爆震燃烧机理提供了依据,为研制工程应用的PDRE提供理论和实践基础.     

多循环PDE利用壁温蒸发煤油的试验研究

燃用煤油是脉冲爆震发动机工程化应用研究中亟待解决的一项关键技术.由于煤油的蒸发性差,常温下在空气中很难起爆,为了突破煤油在脉冲爆震发动机中的应用限制,利用爆震室壁面高温蒸发煤油,提高煤油在PDE中的起爆性能.本文利用PDE工作时的壁温和少量来流空气,在PDE管外设计了蒸发器,对供入PDE的煤油实行预蒸发,以提高燃用煤油...     

Thrust characteristics of an airbreathing pulse detonation engine in supersonic flight at various altitudes

The main thrust characteristics, such as thrust force, specific impulse, specific fuel consumption, and specific thrust, of a pulse detonation engine (PDE) with an air intake and nozzle in conditions of flight at a Mach number of 3 and various altitudes (from 8 to 28 km above sea level) are for the first time calculated with consideration given to the physicochemical characteristics of the oxidation and combustion of hydro-carbon fuel (propane), finite time of turbulent flame acceleration, and deflagration-to-detonation transition (DDT). In addition, a parametric analysis of the influence of the operation mode and design parameters of the PDE on its thrust characteristics in flight at a Mach number of 3 and an altitude of 16 km is performed, and the characteristics of engines with direct initiation of detonation and fast deflagration are compared. It is shown that a PDE of this design greatly exceeds an ideal ramjet engine in specific thrust, whereas regarding the specific impulse and specific fuel consumption, it is not inferior to the ideal ramjet.     

煤油／空气脉冲爆震发动机激波反射起爆研究

为了研究煤油/空气脉冲爆震发动机爆震室内激波遇到障碍物发生反射促使PDE通常完成爆燃向爆震转变的起爆技术,设计加工了环型孔板和双半V型楔面体,并安装在内径100 mm的爆震管内,进行了多循环爆震试验,成功实现了煤油/空气脉冲爆震发动机工作频率30 Hz稳定工作,获得稳定传播的爆震波.研究结果表明:在爆震室内安装合理结构的障碍物能够有效提高激波反射,缩短爆燃向爆震转变的距离(时间),成功获得稳定传播的爆震波.研究结果为优化设计煤油/空气脉冲爆震发动机原理样机提供了初步理论基础.     

铝粉-空气混合物爆燃转爆轰过程及爆轰波结构

 在长为32.4 m、内径为0.199 m的大型长直水平管道中,对铝粉-空气两相流的燃烧转爆轰（DDT）过程及爆轰波结构进行了实验研究。对铝粉-空气混合物弱点火条件下DDT过程不同阶段的特征进行了分析,实验结果显示混合物经历了缓慢反应压缩阶段、压缩波加速冲击波形成阶段、冲击反应过渡阶段、冲击反应向过压爆轰过渡阶段和爆轰阶段,得到了混合物各阶段的DDT参数,由此进一步分析了DDT浓度的上、下限。在1.4 m爆轰测试段的4个截面的环向上各均匀安装8个传感器,对爆轰波结果进行测试,并对铝粉-空气混合物爆轰波的单头结构进行了分析。     

Experimental demonstration of the operation process of a pulse-detonation liquid rocket engine

A low-frequency demonstrator of the operation process of a pulse-detonation liquid-fuel rocket engine, intended for shaping the future design of a new type of rocket engines for spacecraft control, is for the first time developed and tested. As a result, the conditions are determined under which the demonstrator provides reliable deflagration-to-detonation transition (DDT) in a single-pulse or repetition mode. Because DDT occurs within a very short distance (less than 10 bores of the detonation tube), the operating frequency of the demonstrator can be substantially increased.     

Three-dimensional numerical simulation of the characteristics of a ramjet power plant with a continuous-detonation combustor in supersonic flight

Multi-variant three-dimensional numerical simulations demonstrate the feasibility of the continuous- detonation process in an annular combustor of a ramjet power plant operating on hydrogen as fuel and air as oxidant in conditions of flight at a Mach number of M ₀ = 5.0 and an altitude of 20 km. Conceptual schemes of an axisymmetric power plant, 400 mm in external diameter and 1.3 to 1.5 m in length, with a supersonic intake, divergent annular combustor, and outlet nozzle with a frusto-conical central body are proposed. Calculations of the characteristics of the internal and external flows, with consideration given to the finite rate of turbulent-molecular mixing of the fuel mixture components with each other and with the combustion products, as well as the finite rate of chemical reactions and the viscous interaction of the flow with the bounding surfaces, have shown that, in these flight conditions, the engine of such a power plant has the following performance characteristics: the thrust, 10.7 kN; specific thrust, 0.89 (kN s)/kg; specific impulse, 1210 s; and specific fuel?consumption 0.303 kg/(N h). In this case, the combustor can operate with one detonation wave traveling in the annular channel at an average velocity of 1695 m/s, which corresponds to a detonation wave rotation frequency of 1350 Hz. It is shown that, an operating combustor has regions with subsonic flow of detonation products, but the flow is supersonic throughout its outlet section.     

Oblique detonation waves stabilized in rectangular-cross-section bent tubes

Oblique detonation waves, which are generated by a fundamental detonation phenomenon occurring in bent tubes, may be applied to fuel combustion in high-efficiency engines such as a pulse detonation engine (PDE) and a rotating detonation engine (RDE). The present study has experimentally demonstrated that steady-state oblique detonation waves propagated stably through rectangular-cross-section bent tubes by visualizing these waves using a high-speed camera and the shadowgraph method. The oblique detonation waves were stabilized under the conditions of high initial pressure and a large curvature radius of the inside wall of the rectangular-cross-section bent tube. The geometrical shapes of the stabilized oblique detonation waves were calculated, and the results of the calculation were in good agreement with those of our experiment. Moreover, it was experimentally shown that the critical condition under which steady-state oblique detonation waves can stably propagate through the rectangular-cross-section bent tubes was the curvature radius of the inside wall of the rectangular-cross-section bent tube equivalent to 14–40 times the cell width.     

Numerical simulation of the operation process and thrust performance of an air-breathing pulse detonation engine in supersonic flight conditions

Multidimensional simulations of the unsteady gasdynamic flow in the duct of an air-breathing pulse detonation engine (ABPDE) operating on propane gas and the flow around it in supersonic flight at Mach numbers M of 3.0 and an altitude of 9.3 and 16 km are performed. It is shown that, at a length and diameter of the duct of 2.12 m and 83 mm, respectively, an ABPDE with an air intake and a nozzle can operate in a cyclic mode at a repetition frequency of 48 Hz, with a rapid deflagration-to-detonation transition (DDT) occurring at a distance of 5–6 combustion chamber diameters. To determine the thrust performance of the ABPDE in flight conditions, a series of working cycles were simulated with consideration given to the external flow around the engine. Calculations showed that the specific impulse of the ABPDE is approximately 1700 s. This value is much higher than the specific impulse typical of ramjet engines operating on conventional combustion (1200–1500 s) and substantially lower than the specific impulse obtained for the atmospheric conditions at sea level at zero flight velocity (∼2500 s).     

超声速预混可燃气流的点火与燃烧

在激波风洞一激波管组合设备上开展了碳氢燃料超声速预混可燃气流的点火与燃烧实验研究。实验结果表明:利用激波对燃料进行预热,并以高温燃气作为引导火焰,可以有效缩短汽油空气超声速可燃混气的点火延迟时间,使之缩短到 0.2 ms以下。利用纹影照片对超声速燃烧流场结构作出了分析;研究了超声速预混可燃气流的温度以及当量比对超声速燃烧流场结构、点火与火焰传播特性的影响。     

瞬态光谱法确定环氧丙烷DDT过程中起主导作用的基团

解决了燃料爆燃转爆轰(DDT)过程初始阶段弱辐射瞬态光谱测试问题、反应中间产物辐射相对强度定标问题和瞬态光谱测试系统同步控制问题后,从爆炸激波管的6个不同侧窗,拍摄了环氧丙烷DDT过程不同距离处的曝光时间为2～8 μs、分辨率达到0.2 nm的瞬态发射光谱。对所测光谱进行相对强度定标后,得到了主要反应中间产物光辐射强度随燃烧波阵面传播距离的变化曲线, 此曲线反映出DDT过程中反应中间产物的发展过程和其相应的浓度变化。结果显示,在爆燃阶段,燃烧气体的化学反应速率平缓增加,反应中间产物浓度逐渐增大;但在爆燃转爆轰的瞬间,反应急剧增快,反应中间产物的浓度突跃式地成倍增大。其中CO分子和CHO,OH自由基的浓度增幅显著大于其他反应产物,表明这几个基团是环氧丙烷爆燃转爆轰过程中起主导作用的重要基团。     

脉冲爆震发动机性能分析

本文发展了一种新的脉冲爆震发动机性能分析模型,考虑了流体阻力和油珠直径对爆震波速度、压力及脉冲爆震发动机比冲的影响。性能分析模型计算结果与试验结果比较表明,当进行了两相流和流体阻力影响修正后,两者较好。     

Reaction propagation modes in millimeter-scale tubes for ethylene/oxygen mixtures

Effects of tube diameter and equivalence ratio on reaction front propagations of ethylene/oxygen mixtures in capillary tubes were experimentally analyzed using high speed cinematography. The inner diameters of the tubes investigated were 0.5, 1, 2 and 3 mm. The flame was ignited at the center of the 1.5 m long smooth tube under ambient pressure and temperature before propagated towards the exits in the opposite directions. A total of five reaction propagation scenarios, including deflagration-to-detonation transition followed by steady detonation wave transmission (DDT/C–J detonation), oscillating flame, steady deflagration, galloping detonation and quenching flame, were identified. DDT/C–J detonation mode was observed for all tubes for equivalence ratios in the vicinity of stoichiometry. The velocity for the steady detonation wave propagation was approximately Chapman–Jouguet velocity for 1, 2, and 3 mm I.D. tubes; however, a velocity deficit of 5% was found for the case in 0.5 mm I.D. tube. For leaner mixtures, an oscillating flame mode was found for tubes with diameters of 1 to 3 mm, and the reaction front travelled in a steady deflagrative flame mode with velocities around 2–3 m/s when the mixture equivalence ratio becomes even leaner. Galloping detonation wave propagation was the dominant mode for the fuel lean regime in the 0.5 mm I.D. tube. For rich mixtures beyond the detonation limits, a fast flame followed by flame quenching was observed.     

大型水平管道中环氧丙烷-铝粉-空气混和物爆燃转爆轰的实验研究

 在长为32.4 m、内径为0.199 m的大型长直水平管道中,对环氧丙烷-空气两相流云雾及环氧丙烷-铝粉-空气三相流云雾的爆燃转爆轰（DDT）过程进行了实验研究。对弱点火条件下多相混和物DDT过程的不同阶段特征进行了分析,对比研究了不同浓度时混和物的燃爆情况。结果表明：浓度为513 g/m³的环氧丙烷-空气混和物及浓度为237和643 g/m³的环氧丙烷-铝粉-空气混和物均能在管道中完成爆燃向爆轰的转变,进入自持爆轰阶段,其胞格尺寸分别为0.28和0.50 m。     

Experimental study of the influence of annular nozzle on acoustic characteristics of detonation sound wave generated by pulse detonation engine

Acoustic characteristics of the detonation sound wave generated by a pulse detonation engine with an annular nozzle, including peak sound pressure, directivity, and A duration, are experimentally investigated while utilizing gasoline as fuel and oxygen-enriched air as oxidizer. Three annular nozzle geometries are evaluated by varying the ratio of inner cone diameter to detonation tube exit diameter from 0.36 to 0.68. The experimental results show that the annular nozzles have a significant effect on the acoustic characteristics of the detonation sound wave. The annular nozzles can amplify the peak sound pressure of the detonation sound wave at 90° while reducing it at 0° and 30°. The directivity angle of the detonation sound wave is changed by annular nozzles from 30° to 90°. The A duration of the detonation sound wave at 90° is also increased by the annular nozzles. These changes indicate that the annular nozzles have an important influence on the acoustic energy distribution of the detonation sound wave, which amplify the acoustic energy in a direction perpendicular to the tube axis and weaken it along the direction of the tube axis.     

Thrust characteristics of an airbreathing pulse detonation engine in flight at mach numbers of 0.4 to 5.0

Multidimensional calculations are performed to demonstrate that, by its characteristics, the pulse detonation engine (PDE) is a unique type of ramjet propulsion system, which can be used in both subsonic and supersonic aircraft. By a number of examples, it is shown that, in various thrust characteristics, such as the specific impulse, specific fuel consumption, and specific thrust, the PDE substantially exceeds ramjet engines.     

气-液组合横向射流中气体种类的影响

吸气式旋转爆震发动机中燃料的良好雾化对爆震燃烧的组织极其重要,气-液组合横向射流是其中一种重要的燃料喷注技术。为获取气体种类在超声速来流中对其的影响,通过数值方法对液体射流穿透深度和辅助射流气体分布进行研究。采用Euler-Lagrange方法研究不同气体射流对液体射流的作用规律,结果表明：气体射流通过激波结构降低局部来流动量通量提升液体射流穿透深度,相同的来流条件下气体射流动量通量越大,液体射流穿透深度越高,且主要影响扩张段之前的流场区域,气体种类的变化对于后场液体射流穿透深度和雾化特性几乎无影响。     

瞬态光谱法测量环氧丙烷爆轰温度

采用具有像增强功能的光谱探测器——增强型电荷耦合器件ICCD和DG535同步控制器,应用激波管技术和光纤光谱方法,由压力传感器监测爆燃转爆轰的过程,在解决了同步控制,防止误触发等问题后,从爆炸激波管的侧窗拍摄到了环氧丙烷由爆燃转变为爆轰时刻的曝光时间为2μs,分辨率达到0·2nm的瞬态发射光谱。对所测光谱进行强度定标后,可直接得到环氧丙烷爆轰时刻的热辐射背景,用黑体辐射公式按照最小二乘法原则对其进行拟合,得到了环氧丙烷的爆轰温度为2416K。此爆轰温度的获得,为进一步分析环氧丙烷爆燃转爆轰过程的微观机理提供了实验数据。     

Deflagration-to-detonation transition in air-binary fuel mixtures in an obstacle-laden channel

The results of studying deflagration-to-detonation transition (DDT) in hydrogen-methane (propane)-air in a detonation tube with uniformly spaced annular obstacles are presented. The effect of the scaling factor on the DDT was identified. The boundary between fast deflagration and detonation regimes was calculated using a criterion based on a comparison of the gasdynamic and chemical characteristic times for the ignition of the mixture behind the shock wave reflected from an obstacle.