变循环发动机风车起动建模及仿真研究

Modeling and Simulation Study of Variable Cycle Engine Windmill Starting

关键词:  变循环发动机  风车起动  部件特性  换算扭矩  差分进化算法

Key words:  Variable cycle engine  Windmill starting  Component characteristics  Corrected torque  Differential evolution algorithm

摘要:

为了满足变循环发动机风车起动性能仿真的需求，建立了变循环发动机部件级风车起动模型。针对旋转部件等熵效率不连续的问题，引入使用换算扭矩代替等熵效率的方法，给出了旋转部件全转速特性拓展方法。提出了考虑点火及燃烧稳定性的燃烧室稳定性模型。考虑了变循环发动机的8个可调参数，采用差分进化算法对变循环发动机的风车及风车起动性能进行了优化。结果表明，风车状态时，变循环发动机在单外涵模态具有更高的核心机物理转速，有利于点火之后核心机物理转速快速趋于其慢车值。单外涵模态时，变循环发动机在风车状态的可调参数仅与飞行马赫数有关，为了保持较高的核心机物理转速，后涵道引射器外涵面积需随飞行马赫数的增加而减少，其余参数皆固定在其最佳值。飞行高度6km，马赫数0.8时，变循环发动机在单外涵模态下的风车起动时间为1.4s。风车起动过程中燃油流量的增长主要受燃烧稳定性所约束。通过对可调参数的优化，可使变循环发动机在风车起动过程中的关键性能参数最大程度地逼近其限制值，从而缩短风车起动时间。

Abstract:

In order to meet the requirement of windmill starting simulation for variable cycle engines， a component-level windmill starting model of variable cycle engine was established. To solve the problem of discontinuous isentropic efficiency of rotating components， a method of using corrected torque instead of isentropic efficiency was introduced. The method to expand the full speed characteristics of rotating components was given. A burner stability model that can consider ignition and burn stability was proposed. Considering eight variable parameters of variable cycle engine， differential evolution algorithm was used to optimize the windmill and windmill starting performance of variable cycle engine. The results show that，in the windmill state， variable cycle engine has a higher core physical speed in the single bypass mode， which is beneficial to the core physical speed quickly tending to its idle value after ignition. In the single bypass mode， the variable parameters of variable cycle engine in the windmill state are only related to flying Mach number. In order to maintain a high physical speed of the core， the outer bypass area of rear variable area bypass injector needs to be decreased with the increase of the flying Mach number， and the remaining parameters are fixed at their optimal values. When the flying altitude is 6km and the Mach number is 0.8， the windmill starting time of the variable cycle engine in the single bypass mode is 1.4s. The increase in fuel flow during windmill starting is mainly constrained by the burning stability. By optimizing the variable parameters， the key performance parameters of variable cycle engine during windmill starting can be approached to their limit values to the greatest extent， thereby reducing windmill starting time.