基于火炮膛内气固两相流的热散失模型数值仿真

火炮发射过程中的热散失会影响内弹道性能。在数值仿真时由于直接计算热散失较为困难,通常采用对火药力或者燃气的绝热指数进行修正的方法,但该方法无法准确预测内弹道的性能。为此该文提出了一种基于气固两相流模型的热散失计算方法,从高温燃气与身管内壁的热交换出发,建立热散失模型,并将热散失模型与火炮膛内气固两相流模型耦合,热散失量将在气相能量守恒方程中的源项中考虑。以某155 mm火炮为研究对象,采用MacCormack差分格式求解修正后的气固两相流模型,获得膛内流场变化情况。求解得到的流场参量作为热散失模型和身管传热模型的输入参数,计算出内弹道过程中总热散失量以及身管径向温度分布规律。对给出的2种测试工况进行仿真计算,计算结果与实验结果的比较表明,考虑热散失时各指标误差明显减小,最大压力误差小于1.0%,初速误差小于0.5%。总热散失占火药燃烧后产生总能量的2%～4%。证明了该方法的可行性和优越性,有助于提高内弹道仿真的精度。

Numerical Simulation of Heat Loss Model Based on Gas-solidTwo-phase Flows in a Gun Bore

The heat loss during the firing process of artillery will affect the performance of interior ballistics. In numerical simulation,it is difficult to calculate the heat loss directly,so the method of modifying the propellant force or the adiabatic index of the gas is usually used,but this way cannot accurately predict the performance of the interior ballistics. Therefore,a calculation method of heat loss based on gas-solid two-phase flow model was proposed in this paper. Starting from the heat exchange between high-temperature gas and the inner wall of the barrel,a heat loss model was established,and the heat loss model was coupled with the gas-solid two-phase flow model in the gun bore,and the heat loss would be considered in the source term of the gas phase energy conservation equation. Taking a 155 mm gun as the research object,the modified gas-solid two-phase flow model was solved using MacCormack difference scheme to obtain the change of the flow field in the bore. The flow-field parameters obtained were used as the input parameters of the heat loss model and the heat transfer model of the barrel,and the total heat loss in the internal ballistic process and the radial temperature distribution of the barrel was calculated. Through the simulation calculation of the two test conditions given in this paper,the comparison between the calculation results and the experimental results shows that the error of each index is significantly reduced while considering the heat loss; the maximum pressure error is less than 1.0%; the initial velocity error is less than 0.5%. The total heat loss accounts for 2%～4% of the total energy generated by the powder after combustion. The feasibility and superiority of this method were proved. The study is useful to improve the accuracy of interior ballistic simulation.