爆震室壁面条件对脉冲爆震发动机爆震性能的影响

Influence of the Detonation Chamber Wall Conditions on the Performance of the Pulse Detonation Engine

在爆震室内快速形成稳定传播的爆轰波是脉冲爆震发动机的关键.本文利用有限速率化学反应模型,考虑粘性、热对流,基于N-S方程对氢气与空气/氧气为反应混合物的爆震发动机爆震室内流场进行计算.从流场压力、速度、涡量、湍流动能等方面研究爆震室壁面条件对燃烧爆轰性能的影响,分析流场爆轰波压力与流场湍动能的关系,讨论可燃气体燃烧转爆轰的机理.结果表明:爆震室内燃烧爆轰机理受到化学反应能量释放、壁面摩擦效应、壁面与外界热交换的影响.在文中讨论的范围内,相比于半圆形和三角形的爆震室装置,矩形的爆震室增强装置能在更短的时间内得到较高的爆轰波压力和湍动能峰值.壁面粗糙层高度(粗糙度)影响爆震室的燃烧爆轰性质.当壁面粗糙度为0.15mm时,粗糙度对爆轰的激励作用大于抑制作用,能较快形成稳定的爆轰波,且推力为35.5N;随着壁面对流换热系数的增大,爆震室壁面的散热加剧.当壁面对流换热系数大于临界值2.6W/(m2·K)时,爆震室内不能形成稳定的爆震波.

One of the key problems of PDE （Pulse Detonation Engine） is how to quickly form stable propagation of detonation wave in the detonation tube. In this paper, using a finite-rate chemical reaction model, and based on Navier-Stokes equations with viscous effects and heat convection, a numerical simulation on the inner flow field of PDE detonation chamber with the mixture fuel of hydrogen and air/oxygen is carried out. The influences of detonation chamber wall conditions on the deflagration and detonation behaviors are investigated in terms of field pressures, velocities, vortices and turbulent kinetic energy. The relationship between the detonation wave pressure and the turbulent kinetic energy is analyzed. The mechanisms in the deflagration to detonation transition of combustible gases are discussed. The results show that the deflagration to detonation transition is influenced by the released energy of chemical reaction, wall friction and heat exchange between wall and external environment. For the same conditions, compared with the semicircle or triangle obstacles, the rectangular obstacles as enhancement device in the detonation tube can generate a higher pressure of detonation wave and a higher peak value of turbulent kinetic energy in a shorter time. The roughness of the detonation tube wall can influence detonation behavior. When the wall roughness is 0.15 mm, the motivation effect of the wall roughness exceeds its restraint effect on detonation, resulting in fast generation of stable detonation wave and a thrust of 3 5.5 N. The increase of convection heat transfer coefficient can aggravate the heat loss around the wall of detonation tube. Stable detonation wave cannot be produced when the convection heat transfer coefficient on the wall of detonation tube is more than the critical value 2.6W/（m^2·K）.