加力燃烧室用气冷喷油杆结焦特性数值研究

Numerical Studies on Fuel Deposition Characteristics in an Afterburner Air-Cooled Fuel Injector

关键词:  气冷喷油杆  一维非稳态换热  燃油结焦  燃油进口参数  数值模拟  加力燃烧室

Key words:  Air-cooled fuel injector  One-dimensional unsteady heat transfer  Fuel deposition  Fuel inlet parameters  Numerical simulation  Afterburner

摘要:

为阐明实际工作环境参数下气冷喷油杆内燃油结焦速率与沉积厚度等特性，建立沿喷杆轴向的一维非稳态热-流-固耦合换热与燃油结焦计算模型，获得了喷杆壁面与燃油温度、结焦速率与相对结焦厚度等参数沿程分布。分析了燃油进口温度和质量流量对燃油结焦特性的影响，并与无气冷喷杆方案结果进行了对比。计算结果表明：燃油温度沿轴向逐渐升高，喷杆壁温在底端达到峰值。基准工况下气冷喷杆结焦速率和结焦厚度均沿轴向先升高后降低。结焦速率最大为26μg/(cm²·h)，对应相对结焦沉积厚度0.6%。无气冷喷杆方案，在喷杆前端和底部各存在一结焦峰值区域。结焦速率峰值分别为398μg/(cm²·h)和807μg/(cm²·h)，对应相对结焦沉积厚度8%和15%。固定燃油进口流量，随着燃油进口温度升高，结焦速率显著增大，喷杆内结焦总质量呈指数级增长趋势。固定燃油进口温度，进口流量越大，结焦速率略有增大，结焦总质量仅呈线性增长趋势。相较于无气冷喷杆，气冷喷杆可显著降低喷杆壁面与燃油温度，从而大幅抑制结焦生成。

Abstract:

In order to investigate the fuel deposition rate and deposit thickness in an air-cooled injector under actual working conditions, a one-dimensional unsteady heat-fluid-solid coupled heat transfer and fuel deposition model along the axial direction of the injector was proposed. Distributions of both injector wall and fuel temperature, deposition rate and relative deposit thickness were obtained. Effects of both inlet fuel temperature and mass flow rate on deposition characteristics were studied and compared with a non-air-cooled fuel injector. Results show that the fuel temperature increases along the axial direction, and the wall temperature reaches its peak at the bottom of the injector. For the air-cooled injector, the deposition rate and deposit thickness first increase and then decease along the axial direction under the basic condition. The maximum deposition rate is 26μg/(cm²·h), corresponding to a relative deposit thickness of 0.6%. For the non-air-cooled injector, there are two deposition peak areas respectively located at the front and bottom of the injector. Peak values of deposition rate are 398μg/(cm²·h) and 807μg/(cm²·h) respectively, corresponding to relative deposit thicknesses of 8% and 15%. With a fixed inlet mass flow rate, the deposition rate increases significantly as increasing the inlet temperature, and the total deposit mass shows an exponential growth trend. With a fixed inlet temperature, the deposition rate just increases slightly with the increase of inlet mass flow rate, and total deposit mass increases linearly. Compared with the non-air-cooled injector, both wall and fuel temperature can be reduced greatly with the air-cooled one, thus the deposit formation can be significantly inhibited.