多凹腔燃烧室煤油非定常超声速燃烧流动过程研究

Investigation on Transient Process of Supersonic

关键词:  多凹腔燃烧室  非定常燃烧流动  液滴轨迹  穿透深度  凹腔质量交换律  数值研究

Key words:  Multi-cavity combustor  Transient combustion and flow  Droplet track  Penetration depth  Mass entrainment rate of cavity  Numerical study

摘要:

为探究多凹腔燃烧室的燃烧流动过程，采用非定常方法对液态煤油超声速燃烧特性进行了数值研究。计算结果发现，随着燃烧释热的进行，一道拟正激波被推到靠近隔离段入口处，最大压比达到3.77，燃烧达到稳态需要22ms；上游凹腔处煤油液滴运动轨迹表现出很强的非定常性，其运动方向与当地流动时刻的压力条件相匹配，上凹腔附近的液滴穿透深度明显大于下凹腔的，液滴个数也大于后者；出口总压恢复系数为47.09%，与实验值47.50%很接近，出口燃烧效率达到72.91%，体现了多凹腔燃烧室在保证燃烧性能较好时总压损失较低的优点；扩张型面上的凹腔质量交换律大于平直型面上的，表明型面扩张有利于增强凹腔内燃料与主流空气的质量交换；计算预测的燃烧室侧壁、上壁、下壁压力均与实验值吻合得较好。

Abstract:

In order to explore the process of combustion and flow based on a multi-cavity combustor，transient method is used to numerically investigate the supersonic combustion characteristics of liquid kerosene. The numerical results show that an approximate normal shock is pushed back to the isolator inlet as the heat release from combustion proceeds. The maximal ratio of pressure increase is up to 3.77，and the flowfield reaches steady within 22ms. Track of kerosene droplet in the upstream cavities presents strong transient characteristics. Its movement direction matches the pressure in local flow time. Penetration depth of droplet near the up cavity is obviously larger than that of the down cavity，and the droplet number of the former is much more than that of the latter. The total pressure recovery coefficient in the combustor outlet is equal to 47.09%，which is close to the experimental value 47.50%. The combustion efficiency is up to 72.91%，which displays the advantage of a low total pressure loss with a good combustion characteristics for the multi-cavity-based combustor. Mass entrainment rate where cavity located at the expanding surface is larger than that of the level surface，indicating that the expanding surface is beneficial to enhance the mass entrainment between the fuel in the cavity and the mainflow air. Numerically predicted static pressure on the side，up and down wall of the combustor has a good agreement with the experimental datum.