固体火箭发动机药柱翼槽内的火焰传播过程

翼槽区内的火焰传播过程对固体火箭发动机整个点火升压过程有潜在的影响。文中采用高速摄影技术测定了点火瞬态模拟实验发动机后翼槽区内的火焰传播过程，研究了不同设计参数对火焰传播过程的影响，发现翼槽内的火焰传播过程首先是燃气充填过程，其次是火焰传播过程。翼槽内的火焰传播速度与升压梯度和翼槽的宽度有关，升压梯度越高、翼槽越宽则火焰传播速度越高。     

模拟发动机火焰传播过程试验研究

固体发动机火焰传播过程对发动机整个点火升压过程有着潜在的影响.利用靶线法对模拟发动机在不同点火强度、不同点火燃气射流角度和不同药柱结构条件下进行火焰传播试验研究,并对火焰传播位置、火焰峰传播速度进行了分析.结果发现,燃气倾斜喷射导致的火焰峰传播速度大于燃气平行喷射下的火焰峰传播速度；翼槽型装药发动机的火焰峰传播速度大于...     

大型分段式固体火箭发动机点火瞬态过程研究

通过建立固体火箭发动机点火瞬态数学模型,对某大型分段式固体火箭发动机工作初期小火箭式点火装置的火焰喷射方式、分段对接部位火焰传播过程以及前后翼燃面的传播过程等进行数值计算研究。计算结果表明,发动机点火过程中,燃烧室内的流动顺畅,没有出现压强异常振荡现象,点火初期的火焰冲击对分段对接部位的绝热结构影响很小,但整个后翼槽药面全部点燃用时在整个火焰传播期用时占比过大。数值计算结果与全尺寸发动机地面热试车结果对比表明,数值计算点火平衡压强、压强爬升时间以及升压速率与地面热试车结果吻合性好。     

翼柱形药柱模拟发动机火焰传播规律研究

翼柱形药柱模拟发动机的翼槽结构对点火瞬态过程的火焰传播规律存在着潜在的影响.通过试验分析不同质量流量的点火剂燃气以不同的角度喷射到翼柱形药柱模拟发动机的推进剂表面时的火焰传播规律,发现火焰峰传播到翼槽区域后,尾部翼槽底部区域被最后点燃.通过对试验进行数值仿真分析可知,压缩在翼槽底部温度较低的气体减弱了高温燃气与推进剂的...     

翼柱型装药发动机设计参数的匹配性分析

翼槽内的火焰传播过程对翼柱型固体发动机的点火升压过程有很大的影响。通过模拟试验发动机点火试验获得的翼槽内火焰传播数据,结合翼柱型装药点火升压计算模型,分析了推进剂燃速、点火能量、喷管堵盖打开压强、翼槽部位的初始燃面等设计参数在点火升压过程中的匹配关系。分析方法对不同结构翼柱型装药发动机设计是有用的。     

具有潜入式喷管的翼柱形药柱发动机火焰传播过程研究

对潜入和非潜入式喷管的翼柱形药柱发动机点火瞬态过程进行了数值仿真研究,采用修改源项法模拟推进剂燃烧加质,并分析了不同深度、不同宽度的翼槽结构对翼槽区域火焰传播的影响。发现潜入喷管的存在、不同深度、不同宽度的翼槽结构影响火焰传播方式;潜入喷管的存在导致火焰峰连续向翼槽底部及尾部区域传播;尾部翼槽较深时,尾部翼槽尾部尖角处首先点燃,然后火焰峰自尾部翼槽前部与翼槽尖角处同时向翼槽底部传播。尾部翼槽宽度较宽,火焰峰传播速度越快;尾部翼槽深度越深,火焰峰传播速度越慢。     

大长径比SRM头部复杂结构三维纯气相火焰传播过程

以N-S方程,RNGk-ε湍流模型、P1辐射模型为基础,以美国"大力神-Ⅳ"运载火箭助推发动机PQM-1为算例,采用流固耦合传热的火焰传播边界条件,建立了大长径比SRM头部复杂结构的三维纯气相火焰传播模型,分析了发动机点火瞬态头部径向和轴向翼槽内的火焰传播过程。结果表明,对于采用单喷管点火发动机点火的大长径比SRM,头部翼槽的初始发火点在轴向翼槽末端,且头部轴向翼槽内的冷空气影响径向翼槽内的火焰传播,而轴向翼槽内的火焰传播过程对药柱锥形通道内的火焰传播影响不大。     

固体火箭发动机点火瞬间火焰传播模型比较研究

以N-S方程、k-ε湍流模型、P1辐射模型为基础,采用流固耦合传热的火焰传播边界条件,分别对固体火箭发动机点火瞬间的层流粘性模型、湍流粘性模型、层流粘性辐射模型、湍流粘性辐射模型进行了比较分析研究。以PS-1发动机点火过程为算例的分析表明,燃气和推进剂热力参数相同时,层流粘性模型不能形成火焰;湍流粘性模型虽然形成了燃面,但不可自持燃烧;层流粘性辐射模型的点火诱导期长;湍流粘性辐射模型可正确预示初始发火点和火焰传播过程。     

不同高度通道内热薄燃料火焰传播特性的研究

为探究通道高度对逆风火焰传播特性的影响,采用实验、数值模拟、理论分析方法对微重力条件下不同高度通道内热薄燃料火焰传播特性进行了研究。通道高度分别为10mm, 14mm和60mm的短时落塔微重力实验结果表明,相同逆风气流速度时,随通道高度增加,火焰传播速度逐渐增大,且10mm, 14mm和16mm高度通道下的火焰长度比约为通道半高度比的二次方关系。数值模拟与理论分析表明,微重力条件下,随通道高度增加,火焰传播速度、火焰长度先增大再减小,呈非单调的变化趋势。燃烧热释放速率随高度变化呈非单调变化趋势,同火焰传播速度变化规律基本一致。     

翼柱型装药发动机点火升压过程计算

利用实验获得的翼槽内火焰传播规律经验公式,在Ｐ（ｔ）模型的基础上,建立了翼柱型发动机的点火升压计算模型。计算结果与实测数据吻合较好。同时就点火器流量、推进剂燃速、喷管堵盖打开压强等设计参数对发动机点火升压过程的影响进行了分析。     

On a distorted flame front as a hydrodynamic discontinuity

The radius of curvature of a steady distorted flame often turns out to be considerably larger than the width of the thermal structure of the flame. Thus, even under finite deformations of the flame, its structure remains quasi-one-dimensional. This property enables the propagation velocity of a distorted flame front (relative to the gas) to be determined explicitly as a function of the hydrodynamic field and the physico-chemical parameters of the gaseous mixture. With the aid of this relationship one can try to determine the shape of the front in a model which is external with respect to the flame structure and treats the flame as a density jump in an ideal incompressible fluid. As applications, we consider (1) the structure of a Bunsen cone, (2) the extinction of a flame in a divergent flow and (3) the propagation velocity of a corrugated flame.     

Laminar dust flames in a reduced-gravity environment

The propagation of laminar dust flames in suspensions of iron in gaseous oxidizers was studied in a low-gravity environment onboard a parabolic flight aircraft. The reduction of buoyancy-induced convective flows and particle settling permitted the measurement of fundamental combustion parameters, such as the burning velocity and the flame quenching distance over a wide range of particle sizes and in different gaseous mixtures. Experimentally measured flame speeds and quenching distances were found in good agreement with theoretical predictions of a simplified analytical model that assumes particles burning in a diffusive mode. However, the comparison of flame speeds in oxygen–argon and oxygen–helium iron suspensions indicates the possibility that fine micron-sized particles burn in the kinetic mode. Furthermore, when the particle spacing is large compared to the scale of the reaction zone, a theoretical analysis suggests the existence of a new so-called discrete flame propagation regime. Discrete flames are strongly dependent on particle density fluctuations and demonstrate directed percolation behavior near flame propagation limits. The experimental observation of discrete flames in particle suspensions will require low levels of gravity over extended periods available only on orbital platforms.     

Nonlinear analysis of hydrodynamic instability in laminar flames—I. Derivation of basic equations

An asymptotic nonlinear integrodifferential equation is derived for spontaneous instability of the plane front of a laminar flame.If the combustible mixture is deficient in the light component, spontaneous instability will lead to self-turbulization of the flame, and the flame front assumes a strongly nonstationary cellular structure.If there is an excess of the light component, spontaneous instability produces stationary, irregular wrinkles on the flame front, and the flame continues to propagate in a laminar regime.It is shown that in all cases spontaneous instability of the flame implies an increase in its propagation velocity.     

含偶氮四唑胍的RDX-CMDB推进剂的燃烧性能和热行为研究

采用浇铸工艺制备了GZT部分取代RDX的系列RDX-CMDB推进剂样品。研究了GZT对不含催化剂的RDX-CMDB推进剂的燃速、压强指数及燃烧火焰结构等燃烧性能的影响,并采用TG-DTG和DSC实验,初步研究了含GZT的RDX-CMDB推进剂的热行为。结果发现,GZT对推进剂的火焰温度、火焰的暗区厚度、燃面上的亮点数目和燃烧表面对凝聚相的温度梯度等都呈现一定规律性的影响;在1～10 MPa范围内,GZT使RDX-CMDB推进剂的燃速升高,压强指数降低。热行为研究表明,加入GZT时,推进剂的DSC曲线上出现一个单独的放热分解峰,对应TG曲线上也表现出一个单独的失重过程。     

Nonlinear analysis of hydrodynamic instability in laminar flames—II. Numerical experiments

We consider a nonstationary nonlinear integrodifferential equation describing the evolution of a disturbed plane flame front. The following two-dimensional problems are solved numerically: (i) The formation of a wrinkled noncellular laminar flame front under conditions of spontaneous hydrodynamic instability. (ii) The formation of a turbulent cellular flame front under conditions of spontaneous diffusional-thermal instability. (iii) The formation of a turbulent wrinkled-cellular flame front under conditions of spontaneous hydrodynamic and diffusional-thermal instability. We compute the flame front velocity in laminar and turbulent propagation.     

超音速燃烧室凹槽流动特性研究

对超音速燃烧室内各种构型的凹槽流场进行了数值模拟,研究了凹槽的后壁面斜角、凹槽长高比及凹槽前后壁面高度比等参数对凹槽流场的影响,计算了各种构型凹槽的阻力、停留时间等。研究结果对定量认识凹槽流场、优化凹槽构型、设计高效率的火焰稳定器具有一定借鉴作用。     

偶氮四唑胍对含催化剂的RDX-CMDB推进剂燃烧性能的影响研究

采用浇注工艺制备了GZT部分取代RDX的系列含催化剂的RDX-CMDB推进剂样品。研究了GZT对含催化剂的RDX-CMDB推进剂的燃速、压强指数及燃烧火焰结构等燃烧性能的影响,对比分析了GZT对含催化剂和不含催化剂的RDX-CMDB推进剂燃烧行为影响不同的原因,并采用DSC实验初步研究了含GZT和催化剂的RDX-CMDB推进剂的热行为。结果发现,GZT对推进剂的火焰温度、火焰的暗区厚度、燃面上的亮点数目、燃烧表面对凝聚相的温度梯度等都呈现一定规律性的影响;在1～10 MPa内,GZT使含催化剂的RDX-CMDB推进剂燃速降低,压强指数升高;热行为研究表明,含催化剂的GZT-RDX-CMDB推进剂的DSC曲线上出现了GZT单独分解峰,且DSC的第一分解峰温随GZT的加入而减小。     

液体亚燃燃烧室点火装置工作特性数值研究

基于气体动力学和计算流体力学的相关理论,采用CFD-ACE＋流场计算软件,对液体亚燃燃烧室点火装置单独工作时的稳态流场进行了数值模拟.在试验验证的基础上分析了点火器室压、点火导管内径和导管的结构形式对火焰点火性能的影响.结果表明：当点火器室温和燃气流量恒定时,若保持管道的扩张比不变,选用较低室压的点火器更利于点火;在一定范围内增大导管内径可以提高火焰的点火性能;燃气在直管内的流动损失较小,出口射流的速度较高,穿透深度较大,带弯头的点火导管出口火焰特征类似,有无弯头对火焰的影响很大,而角度差异产生的影响很小.     

Experiments on velocity augmentation of spherical flames by grids

Using spherical wire mesh screens with a wire diameter d and a mesh size l, an experimental study was carried out involving homogeneous mixtures of propane/air, ethylene/air, acetylene/air and with oxygen enriched air. Streak photographs of the processes were taken, yielding information on the flame propagation speeds inside and outside the screen. The ratio of the two speeds immediately before and after crossing the screen, α, can be interpreted as practically equivalent (for the same “heat release”) to the ratio of flame velocities relative to the unburned gas, i.e. Values of (α − 1) are correlated with the Reynolds number based on the wire thickness d, density and viscosity of the unburned gas and flame propagation speed inside the wire mesh. The experiments were repeated with two and three spheres of different diameters, e.g. inner screen 9 cm in diameter and outer screen 18 cm in diameter or three screens, 9, 13.5 and 18 cm, respectively. The second screen usually added a factor of 2 on the value of α. The third screen produced very little additional effect. The highest value of α we ever obtained for mixtures with air was about 12 (for acetylene/air). With oxygen enriched air the situation is quite different. If the flame velocity of the laminar flame relative to the unburned gas exceeds 2 m/sec, the value of α may increase up to a level corresponding to detonation.     

同轴喷嘴自发激励高频燃烧不稳定性试验研究

为增进对液氧煤油火箭发动机同轴离心喷嘴燃烧不稳定性过程的理解,在大气环境下进行了同轴离心喷嘴的自发激励燃烧不稳定性试验。试验采用单喷嘴敞口模拟燃烧室,高温的氧气和空气混合物从同轴喷嘴的直流喷嘴喷注,高温的煤油蒸气从同轴喷嘴的离心喷嘴喷注。通过逐步改变氧化剂流量使模拟燃烧室内产生自发激励高频燃烧不稳定性,使用脉动压力传感器和黑白高速相机记录稳定和不稳定燃烧工况下的脉动压力和火焰。研究发现：气气同轴离心喷嘴的自发激励高频燃烧不稳定过程呈现“滞后”现象;不稳定工况下的火焰均为脱口火焰,火焰特征长度约等于喷嘴出口到脱口火焰团上沿的距离;气气同轴离心喷嘴燃烧不稳定性的发生原因可以被认为是因混合特征时间与声学特征时间相关。