Measurement of temperature, velocity and water vapor concentration in a scramjet combustor based on nearinfrared diode laser absorption

A multi-channel Tunable Diode Laser Absorption Spectroscopy (TDLAS) system was designed and constructed for flow parameters diagnostics in a scramjet combustor. Two fiber coupled distributed feedback (DFB) lasers with narrow line width were used to probe two H2O absorption features (7185.597cm-1,7444.35cm-1+7444.37cm-1(c ombined)) by using direct absorption Time-Division-Multiplexing (TDM) strategy at a 4-kHz repetition rate. Laser light was split into five beams and transmitted across the test region. Two motorized precision translation stages were used to move the collimators during the test, so that the three beams located near the cavity and at the exit of the combustor can scan the cross sections respectively. Flow parameters could be obtained simultaneous which included average temperature, water vapor concentration and velocity at the entrance of the combustor, the distribution of temperature, water vapor concentration at a cross section near the cavity, the distribution of temperature, water vapor concentration and velocity at the exit cross section of the combustor. The parameters of the flow entering and exiting the combustor could be used to evaluate the performance of the direct-connected scramjet facility and the combustion efficiency of the combustor. The parameters at the cross section in the combustor could also be used to analysis combustion characteristics in the combustor

Plasma-assisted ignition for a kerosene fueled scramjet at Mach 1.8

By using a plasma jet (PJ) torch with 1.5 kW input power as an igniter, successful ignition for liquid-kerosene fueled combustion experiment was conducted in a direct-connected supersonic test facility. The incoming flow has total temperature of 950 K and local Mach number of 1.8, corresponding to Mach 4 flight condition. In this study, several optical techniques, including high speed photography, high speed schlieren photography, and planar laser scattering (PLS) technique, were combined to study the ignition process, flame propagation, and mixing features of liquid kerosene fuel with air around the cavity. The effect of fuel injection position, injection pressure, and feedstock gas on ignition performance has been analyzed. The results indicate that local mixing is a critical factor for ignition. It is also shown that the PJ torch with N-2 + H-2 feedstock is superior to the PJ torch with N-2 feedstock for the ignition of liquid-kerosene fuel. These results are valuable for the future optimization of kerosene-fueled scramjet engine when using a PJ torch as an igniter

燃烧气脉冲除灰技术

我国电站锅炉大量燃用高灰煤,致使锅炉尾部受热面出现严重积灰,影响锅炉效率和出力。国内外最常用的蒸汽吹灰方法往往会使烟气湿度增大,更容易造成受热面的积灰,腐蚀和堵塞。1993年中国科学院力学研究所在国内率先采用高速脉冲气流和冲击波清除积灰(灰垢)的原理,研究并开发了适用于我国电站锅炉的新一代除灰技术——燃烧气脉冲除灰技术

气脉冲除灰技术应用研究

从气脉冲原理出发，系统地分析了混合气的流动和混合比对燃烧波压力的影响，测量了气脉冲的作用范围，并对伴随输出的声波进行了声频谱分析。结果表明：在8m的范围内，气脉冲冲击波能清除中等粘合强度的灰渣，气脉冲的声频谱基本覆盖了声波除灰的频谱范围

障碍物扰动对预混火焰发展的影响

研究了半开口管道中障碍物对预混火焰传播的影响．结果表明，由于障碍物引起的扰动，使火焰在传播过程中不断加速，同时管内压力上升．根据火焰速度的量级，在受限管道中的火焰传播可以分为3种状态：熄火态、雍塞态和爆轰态．在贫燃极限附近，火焰加速一段距离后自动熄灭；在雍塞态，最大火焰速度略低于燃烧产物声速，基本上不受阻塞比变化的影响；随着当量比的上升，对敏感气体而言，火焰传播由爆燃转变为爆轰，最大火焰速度随阻塞比的增加而降低；而对于非敏感气体，则不存在爆燃转爆轰现象．管内压力随障碍物阻塞比的变化并不呈现单调规律．同时用非稳态可压缩流体模型模拟了管内的火焰加速和压力发展过程，计算结果和实验结果吻合得较好

半开口管道中的氢/空气火焰加速和压力发展过程

研究了氢/空气预混火焰在半开口管道中的火焰加速现象和压力发展过程。结果表明，重复 布置的障碍物对火焰速度和压力提升产生显著的影响。火焰传播状态随着氢气当量比的变化而发生改变，在氢气当量比约为0.34时，火焰速度出现第一次跃变；随着氢气当量比进一步提高，火焰速度发生第二次跃变，即由爆燃转为爆轰。发生爆轰时氢气当量比的范围随着阻塞比的不同而发生变化

Flame Propagation of H_2-Air in a Semi-Open Obstructed Tube

针对氢/空气混合物，通过实验研究了其预混火焰在半开口管道中的火焰传播加速现象。结果表明，火焰传播状态随着氢气当量比的变化而发生改变。当氢/空气混合物被点燃后，由于障碍物的扰动，火焰在管道中不断加速传播，并最终到一准稳态传播。在氢气当量比0.34附近时，火焰速度发生跃变。当氢气当量比足够大时，火焰传播由爆燃态转变为爆轰态。在本实验条件下，爆燃转准爆轰的临界条件是d/λ ≥ 2.6（d是圆环形障碍物内径，λ是爆轰格胞尺度）。障碍物阻塞比的变化对最大火焰速度和压力提升的影响不明显

Numerical Simulation of Development of Turbulent Flame in an Obstructed Tube

应用湍流马赫数修正的非稳态可压缩性K-ε-f-gr四方程湍流模型，模拟了半开口狭长管道中重复布置的障碍物引起的湍流火焰加速现象。结果表明，障碍物产生的扰动对加强燃烧和湍流输运的影响很大。随着火焰向前传播，火焰穿过障碍物时发生变形，反应区越来越长，且火焰速度逐渐上升。同时，火焰速度和管内压力的计算结果与实验测量值吻合良好，修正后的湍流模型能较真实地模拟障碍物管内预混火焰的发展过程