考虑自然对流的厚交换层液滴蒸发模型及其检验

Natural Convection Thick Exchange Layer Droplet Evaporation Model and Its Verification

关键词:  单液滴  蒸发  煤油  甲醇  蒸发率  蒸发模型  厚交换层理论

Key words:  Droplet  Evaporation  Kerosene  Methanol  Evaporation rate  Evaporation model  Thick exchange layer theory

摘要:

两相模型对航空发动机燃烧室数值模拟的准确性至关重要，液体燃料的蒸发特性是两相模型的一个关键因素，为了得到准确合理的两相模型从而为燃烧室的设计提供依据，采用悬滴法实验研究了甲醇、煤油及航空煤油液滴在静止环境下的高温蒸发现象，并得到了液滴蒸发速率随环境温度的变化规律。比较实验数据与已有液滴蒸发模型计算结果，发现二者具有较大差距，分析认为已有模型应该考虑静止环境中自然对流对液滴蒸发的影响。在前人工作基础上，用考虑自然对流浮升力因素的厚交换层理论对静止环境下液滴的高温蒸发进行理论推导，得到新的蒸发模型。采用本文实验结果及文献液滴蒸发实验数据对新模型进行了检验。对于甲醇和煤油，在本文的实验工况下，新模型计算结果与实验结果具有较好的一致性，与实验的相对偏差不超过20%；对于煤油，新模型计算结果与文献实验结果的相对偏差不超过10%。

Abstract:

Two phase model is crucial for the accuracy of the numerical simulation of the combustion in the aero engine combustor，and the liquid fuel evaporation characteristic is a key factor of the two phase model. In order to obtain the accurate and reasonable two phases model to provide theoretical basis and direction for the design of combustor，the methanol，kerosene and aviation kerosene droplets evaporation rate in a quiescent high temperature environment were studied by suspended droplets experiments，and the variation law of the evaporation rate value over the ambient temperature was obtained. There are obvious differences between the existing evaporation models predictions and the experimental data. Upon the results analysis，the existing evaporation models should consider the natural convection influence in a quiescent environment. Based on the previous research，in this paper，the natural convection buoyancy force factor was introduced into the thick exchange layer theory and the theoretical derivation for the droplet evaporation characteristic in a quiescent high temperature environment. A new evaporation model was worked out. Under the experimental conditions of this paper，the calculation results of the new model are consistent with the experimental data for kerosene and methanol，and the relative deviations from experimental results are less than 20%. The relative deviations between the new evaporation model predictions for kerosene and experimental ones from references are within 10%.