CO与H2氧化释热对煤油V型钝体稳焰器回流特性的影响

Effects of CO and H2 Oxidation Heat Release on Reversed-Flow Characteristics of Kerosene V-Gutter Bluff Body Flameholder

关键词:  V型钝体稳焰器  煤油化学机理  回流流动  释热率  LES-TPDF  两相扩散火焰

Key words:  V-gutter flameholder  Kerosene chemical mechanism  Reversed-flow  Heat release rate  LES-TPDF  Two-phase diffusion flame

摘要:

针对高速、贫氧的加力燃烧室流动特性，应用大涡模拟-输运概率密度函数方法（LES-TPDF）结合三种航空煤油机理，在来流马赫数为0.1的条件下，对一种V型钝体稳焰器进行两相燃烧流场的计算。结果表明，不同化学机理模拟的回流特性差异大，剪切层湍动能强度与回流区长度不同。由释热分析发现，钝体燃烧CO或H₂氧化强烈，过弱的氧化使剪切层释热率低、掺混弱，因此湍动能小，CO和H₂在回流区积累并缓慢反应、延长回流。本文统计不同机理的反应放热量，发现Kundu机理的CO，H₂氧化放热之和仅占总过程的25.30%。而反应强的骨架机理与JL4机理放热占比达到50.50%与87.16%，回流吻合实验，适用于当前工况的研究。

Abstract:

Aiming at the flow characteristics in the high-speed， low-oxygen afterburner combustion chamber， three chemical mechanisms with Large Eddy Simulation and Transport Probability Density Function （LES-TPDF） method were selected to calculate the two phase combustion flow field of a V-gutter flameholder with an inflow Mach number of 0.1. Results show that reversed-flow characteristics vary between different chemical mechanisms， making turbulent kinetic energy and recirculation zone length different. The analysis of heat release characteristics reveals that CO or H₂ are vigorously oxidized in bluff-body combustion. Too weak oxidation leads to low heat release rate at shear layer and weak mixing， hence a low turbulent kinetic energy and accumulating excess CO and H₂ in the recirculation zone， which reacts mildly and prolongs reversed-flow. The reaction exothermic is also analyzed in this paper and it is found that， for the Kundu mechanism， CO and H₂ oxidation exotherm only accounts for 25.30% of the overall process. While the skeleton mechanism and JL4 mechanism， with higher oxidation exotherm， account for 50.50% and 87.16%， which match experimental flow characteristics and are suitable for the study of the current condition.