Effect of Initial Turbulence on Ignition, Combustion, and Flame Stabilization in a Gas-Suspension Flow

The influence of initial turbulence of an air flow with suspended aluminum particles and the aluminum-particle size on ignition, combustion, and flame stabilization in a combustor with sudden expansion is considered. __________ Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 1, pp. 39–48, January–February, 2006.     

Effect of Unmixedness in Large Eddies on Ignition and Combustion of Turbulent Jets of the Fuel in a Supersonic Flow

A method and results of computing the influence of unmixedness in large eddies generated by instability of a contact discontinuity on ignition and combustion of turbulent jets of a fuel in a supersonic flow are presented. The basic system of equations is the Reynolds-averaged Navier-Stokes equations. The influence of unmixedness on chemical reaction rates is reproduced by using a random number generator adjusted in accordance with the probability of origination of favorable conditions for proceeding of chemical reactions, which is computed in each node of the computational grid. The problem of combustion of a plane hydrogen jet injected into a supersonic flow along the plate surface is considered as an example. It is shown that allowance for unmixedness in the case where the flow and the jet have favorable initial parameters for self-ignition leads to a delay in heat release and to origination of pressure and temperature fluctuations. As the parameters approach the self-ignition limit, these fluctuations increase, and the combustion becomes intermittent. __________ Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 1, pp. 49–56, January–February, 2006.     

Modeling of Ignition and Combustion of a Coflowing Hydrogen Jet in a Supersonic Air Flow

Combustion, Explosion, and Shock Waves - Results of a numerical study of mixing, ignition, and combustion of a cold hydrogen jet propagating along the lower wall of a channel parallel to a...     

Experimental Investigation of Supersonic Flame Stabilisation based on Fuel Self‐Ignition

As part of the Special Research Co‐operative Sonderforschungsbereich 255 “Transatmospheric Flight Systems” the thermo‐fluid dynamics of supersonic reacting flows were experimentally studied. Fuel (gaseous hydrogen, liquid kerosene) was injected into a vitiated Mach 2.15 air stream. The supersonic flame was stabilized by means of fuel self‐ignition. The interaction between gas dynamics and chemical kinetics was investigated employing optical measurement techniques (schlieren technique, Rayleigh technique, OH self‐fluorescence). Special attention has been focussed on the influence of shock waves on the self‐ignition mechanisms. The use of liquid hydrocarbons as fuel in a supersonic combustor was the second research topic. Fundamental differences were found to exist in the ignition characteristics of gaseous hydrogen and liquid hydrocarbons. The analysis of the test data led to the formulation of a gas dynamic feedback mechanism, which helps to explain the operating characteristics of kerosene‐fuelled combustors.     

Stabilization of the Flame of a Powdered Metal Combustible in a Turbulent Air Flow

The process of stabilization of the flame of a powdered metal combustible in a combustion chamber with sudden expansion is studied. Experimental data on the influence of the main factors on the limits of stable combustion in a turbulent flow of an aluminum–air mixture are obtained.     

Combustion of Liquid and Gaseous Fuels in a Supersonic Combustor

Results of an experimental study of a full scramjet model operating on kerosene, which was performed in an IT-302M hotshot wind tunnel based at the Institute of Theoretical and Applied Mechanics of the Siberian Division of the Russian Academy of Sciences, and an experimental study of a model operating on hydrogen, which was performed in a hotshot wind tunnel with fire heating based at the China Aerodynamic Research and Development Center, are reported. The tests were performed for Mach numbers 5 and 6 for flow parameters close to in-flight conditions. An optimal system for kerosene injection under these conditions was determined, and the thrust characteristics of the engine model were examined. The possibility of controlling kerosene combustion in tests in the short-duration wind tunnel was analyzed, and special features of fuel ignition in a short combustor were considered. Intense combustion of kerosene was achieved with upstream injection of more than 3% of hydrogen, which allowed obtaining effective thrust. The distributions of static pressure and force characteristics of the model in the case of kerosene and hydrogen combustion were compared.     

多重射流氢氧焰燃烧反应器的结构及特性

在分析多重射流燃烧特性的基础上,设计了预混合多重射流氢氧焰燃烧反应器,研究了其结构及燃烧特性。采用燃烧后热流体的空白模拟实验考察了多重射流氢氧焰反应器的火焰形式,定性分析了反应区的温度场和浓度场,利用经验公式对多重射流的空气动力学特征进行了分析和模拟计算,从理论上说明预混合火焰可以提供较为均匀的温度场和浓度场。     

Kerosene Combustion in a Pseudoshock with Varied Conditions at the Supersonic Ramjet Combustor Model

Combustion, Explosion, and Shock Waves - Results of studying kerosene combustion in a pseudoshock with varied temperature and velocity in a supersonic ramjet combustor model are presented....     

Diffusion Combustion of a System of Plane Supersonic Hydrogen Jets in a Supersonic Flow

Calculation results for diffusion combustion of a system of plane supersonic hydrogen jets in a supersonic flow are presented. The calculations are based on parabolized Navier–Stokes equations closed by the one-parameter (k – l) model of turbulence and a multistage mechanism of hydrogen oxidation. The influence of the air-flow composition and fuel-injection methods on the shape of the flame front and combustion efficiency of hydrogen is analyzed.     

波动耦合影响下的淹没式射流研究

简述了一种新型射流研究方式。淹没式射流研究中,射流流束受到周围介质波动影响。以波动耦合叠加效应的理论为基础,研究射流流束扩散的能量分布变化。以这种能量分布变化为依据,得出介质波动对于射流加载影响的效果结论,为今后的淹没式射流研究提出新型的理论依据。     

刚性组合装药可燃传火管性能试验研究

本文针对刚性组合装药的点传火技术进行了一些基础性试验研究和理论分析，建立了自然环境下刚性组合装药的点传火试验系统，并对多种点传火方案进行了模拟试验，获得了点传火系统在自然环境下的重要性能参数。     

Effect of Fuel Mixture Composition on Flame Vortex Structure

This paper studies the effect of propane–air mixture composition on the spontaneous structure of an inverted vortex flame during combustion of a gas injected to the lower surface of a plate inclined to the horizon. It has been established that the angular velocity of combustion products is determined by the orientation of the gas injection velocity vector with respect to the gravity direction, the velocity in the burner nozzle, and the fuel mixture composition. It has been shown that fuel composition changes cause restructuring of the velocity field in the vortex structure, which leads to concentration and temperature changes in the flame. Dependences of flame height and fuel combustion completeness on injectionrate and propane content are obtained.     

旋转流中预混合火焰高速传播现象-II. 点火位置与燃烧过程

在前期关于Vortex-bursting旋流式预混燃烧器的燃烧效率及其进口混合气速度分布对燃烧效率的影响实验基础上，围绕燃烧器的点火特性，对旋流场中的点火位置和稳定火焰形成进行了数值分析. 结果表明，不适当的点火位置会影响稳定火焰的形成，在相同的燃烧工况下，在流场中点火位置不同，火焰的发展出现不同的趋势. 在靠近中心轴附近的低速区点火时，火焰能够稳定；在靠近管壁的高速区点火时，撤离点火源后，火焰吹熄. 本结果对于强化预混合燃烧的稳定性具有理论和工程指导意义.     

Particle Deposition on a Truncated Cylinder in a Supersonic Flow at Low Pressure

Deposition of particles, suspended in supersonic gas flows, onto the impaction plane of a truncated cylinder in low pressure has been studied numerically. The analysis of axisymmetric compressible Navier-Stokes equations was carried out, for a gas phase, by using the lower-upper symmetric Gauss-Seidel (LU-SGS) scheme. In addition, the Lagrangian trajectory model was used for a particle phase. The dilute gas-particle flow was assumed to be coupled in one direction. The effect of freestream pressure on the process of particle deposition was investigated. The local characteristics of deposition were also demonstrated in terms of particle size and freestream pressure. It is found that the particles with low total deposition efficiencies can be deposited rather uniformly on the impaction plane when the effect of thermophoresis is considered.     

Mathematical Model of Ignition of Condensed Systems by a High-Temperature Supersonic Underexpanded Jet

An approximate mathematical model is constructed and characteristics are calculated of ignition of a reactive plane infinite obstacle by a high-temperature nonstationary axisymmetric supersonic jet of combustion products escaping from the igniter. The approximate model data are compared with the results of numerical calculations using the system of equations of motion of an ideal gas, nonstationary equations of heat conduction and chemical kinetics, and conditions of conjugate heat exchange at the gas–condensed medium interface. The suggested approximate model adequately describes the ignition process and can be used for proximate evaluation of ignition time and temperature. Key words: ignition, jet, gas dynamics, supersonic flow, mathematical simulation.     

大长径比点传火管的点传火性能

设计了一种点传火模拟装置,对布质点火药包、用硝基软片管封装的点火装药两种点传火装药结构进行了点传火性能试验。结果表明,同一种点火药条件下,带有硝基软片管的药管结构能够将火焰传播速度从85m/s提高到144m/s;相同装填方式下,以黑火药和奔奈药条为点火药时,传火管的火焰传播速度为205m/s,比以黑火药为点火药时提高了42.4%。采用带有硝基软片管的药管、以黑火药和奔奈药条为点火药的点传火装药结构,能够显著提高传火管的传火速度、解决传火不畅问题,使大长径比点传火管具有良好的传火性能。     

带侧边微孔射流扰动火焰结构特性

In this paper, an innovative jet lifted flame with side micro-jets has been proposed and its effects on the flame structure have also been investigated. Due to the changes of the initial combustion conditions, mixing and aerodynamics which resulted from the perturbation of the side micro-jets, such a lifted jet flame has different flame structure compared with the common premixed flame. Results demonstrate that use of the micro-jets can control, to a certain extent, the flame structure, including the flame length, lift-off distance and blow-off limit. With the same fuel and air flow rate, the flame length with the side micro-jets will decrease about 5%-40% as the air volume ratio α increases from 58%-76%. Compared with the common diffusion flame, the jet flame with the side micro-jets demonstrates to be easier to be a momentum-dominated flame. The flame length with 2 micro-jets is about 5% less than with 6 micro-jets under the same fuel and air flow rate. With the same α, the fewer number of the controlled jets lead to the flame with relatively shorter length, not easier to be blown off and higher NOx emission. With cer-tain fuel flow rate, the critical air volume ratio is largest for the flame with 3 micro-jets, which is more difficult to be blown off than the cases with 2, 4 or 6 micro-jets.     

高分子甲醛吸收剂对聚甲醛的热稳定性能与结构的影响

采用差示扫描量热仪（DSC）、热重分析仪（TGA）及偏光显微镜（PLM）研究高分子甲醛吸收剂共聚酰胺（COPA）和密胺树脂（MF）对聚甲醛（POM）的热稳定性能与结构的影响。结果表明：两种高分子甲醛吸收剂都能起到结晶成核剂的作用。同时COPA对POM的热稳定性效果优于ME的,但会提高POM的黄色指数,而MF会降低POM的黄色指数。     

基于火焰稳定特性浸没燃烧器的设计与试验研究

采用传统设计方法对浸没燃烧技术中的燃烧器进行设计,在实际应用过程中总出现回火、脱火、燃烧不稳定问题,本文根据火焰稳定特性知识构建了天然气火焰稳定性图,提供了一种对于燃烧气体燃料浸没燃烧器燃烧室的设计思路,并对该思路下设计的浸没燃烧器燃烧室进行了具体设计;融入旋流稳焰原理,一次空气与燃料旋流预混,二次空气冷却燃烧室外壁并被预热然后在燃烧室头部进入燃烧室助燃,进行了浸没燃烧器的总体设计,并对设计的燃烧器在自行设计的增压浸没燃烧试验台进行了初步试验研究,试验侧重燃烧稳定性与污染物排放。结果表明该浸没燃烧器燃烧稳定性相对较好,且由于良好的结构设计,节能减排效果显著。     

超声波辅助提取桔子皮中果胶的研究

讨论了利用超声波辐射萃取法从桔皮中提取果胶的不同因素的影响,通过实验确立了超声波条件下提取果胶的最佳工艺条件为:用盐酸调pH值为1.8,用水作为溶剂,料液比为1:20,超声功率为600W,作用时间为40min,乙醇浓度为60%,提取率可达到20.8%。