【作者】 潘玉竹；

【导师】 余永刚；

【作者基本信息】 南京理工大学 ， 兵器发射理论与技术， 2013， 博士

【摘要】 HAN基液体推进剂是一种新型绿色高能液体推进剂,是液体火箭发动机的理想燃料之一,其燃烧特性的优劣直接影响到发动机的工作性能。本文围绕HAN基液体推进剂的高压燃烧特性,开展了实验研究和数值模拟工作,主要研究内容及成果如下：(1)利用流体极性物质热物性参数估算的理论与经验公式,计算了HAN基液体推进剂LP1845、LP1846的热物性参数随温度、压力的变化规律,为HAN基液体推进剂蒸发、燃烧理论的数值模拟工作提供了必要的基础数据。(2)建立了HAN基液体推进剂单滴常压蒸发的简化模型,计算了不同环境温度、液滴尺寸、液滴初温、对流速度条件下LP1846液滴的蒸发特性。计算结果表明：LP1846单滴的蒸发过程可以分为瞬态加热阶段和平衡蒸发阶段。提高环境温度,瞬态加热阶段和平衡蒸发阶段都缩短,平衡温度增大。增大液滴初始直径,瞬态加热阶段和平衡蒸发阶段都延长,但平衡温度没有变化。提高液滴初始温度,瞬态加热时间变短,但对平衡蒸发阶段没有影响,平衡温度保持不变。对流速度越大,瞬态加热时间越短,平均蒸发常数越大,但平衡温度不受影响。(3)建立了HAN基液体推进剂单滴高压蒸发的简化模型,计算了LP1845液滴在高温高压氮气环境中蒸发时滴径、滴温随时间的变化关系。计算结果表明：随着蒸发的进行,液滴半径先增大后减小,且减小时滴径满足D2定律；液滴温度先迅速上升,然后逐渐稳定在一个平衡温度。在环境温度保持不变时,随着环境压力的增大,液滴达到平衡温度的时间增长,而液滴生存时间缩短。(4)采用VOF两相流模型,考虑气液相间传质、表面张力、气相内的组分输运,推导了液滴蒸发时的相间传质源项,建立了HAN基液体推进剂单滴在对流氮气中的蒸发模型,计算了LP1846液滴蒸发过程中液滴及周围流场特性参数的变化规律,成功捕捉了液滴表面的Stefan流和尾部的漩涡特性。(5)考虑液滴表面的气相化学反应,建立了一个适用于HAN基液体推进剂液滴燃烧的简化模型。利用此模型,计算了LP1846单滴在静止大气中燃烧时不同环境温度下的质量燃速和液滴寿命。结果表明,随着环境温度的升高,液滴质量燃烧速率加快,且温度越高,速率增加得越快。液滴寿命随环境温度的增大而减小。通过计算结果与实验数据的对比,验证了此模型的正确性。(6)设计了一种测量HAN基液体推进剂高压线燃速的实验装置,其高压环境通过固体火药燃烧产生,并引入包覆药柱燃烧补偿压降,以维持近似的恒压环境,同时采用自研的离子探针测速技术测定了液体推进剂燃烧时火焰面的传播速度。利用此实验装置,分别测量了HAN基液体推进剂AF-315在29.4～55.0MPa内、LP1846在6-28MPa内的表观线燃速。(7)借助固体推进剂稳态燃烧理论,提出了液体推进剂一维燃烧波结构的概念,建立了HAN基液体推进剂液柱一维稳态燃烧的简化模型,得到了其燃烧速率随压力变化的函数关系式。利用此简化模型,计算了LP1846在6～28MPa压力范围内的燃烧速度,其数值模拟结果与实验结果的最大误差为3.2%,表明这种简化模型是有效的。(8)利用VOF两相数值模拟方法,建立了HAN基液体推进剂高压稳态燃烧的二维模型,计算了AF-315在高压线状燃烧器中燃烧时,温度场、压力场、速度场等随时间的变化规律,成功捕捉了液面在整个燃烧过程中的动态移动图像,得到了AF-315液体推进剂在不同的环境压力下的燃烧速度。通过与实验结果进行对比,验证此法可行,能够用来模拟HAN基液体推进剂的高压燃烧过程。更多还原

【Abstract】 HAN-based liquid propellant is a new type of green high-energy liquid propellant, whose combustion behaviors will directly affect the performance of the engine, as an ideal fuel for the liquid rocket engine. The experimental and theoretical studies have been conducted, focusing on the high-pressure combustion characteristics of HAN-based liquid propellants. The main research contents and results are as follows:(1) By use of the theoretical and empirical formulas for estimating the thermal physical property parameters of liquid polar substances, the thermal physical properties of HAN-based liquid propellant under different pressures and temperatures were calculated, which can provide basic data for the theoretical research on the evaporation and combustion of HAN-based liquid propellants.(2) A simplified model for the HAN-based liquid propellant single droplet evaporation under atmospheric pressure was established, and the influences of ambient temperature, droplet size, droplet initial temperature, convection velocity on the LP1846droplet evaporation characteristics were researched. The results show that the evaporation process of the LP1846droplet can be divided into the transient heating stage and the equilibrium evaporation stage. As the ambient temperature grows, the periods of both the transient heating stage and the equilibrium evaporation stage are shortened, but the equilibrium temperature increases. The two stages are all extended with increasing droplet size, but there is no change in the equilibrium temperature. As the droplet initial temperature increases, the transient heating duration gets shorter, but the equilibrium evaporation stage is unaffected, and the equilibrium temperature remains the same. The larger the convection velocity is, the shorter the time of the transient heating stage is, and the bigger the average evaporation constant becomes, but the equilibrium temperature remains constant.(3) A high-pressure evaporation model for the HAN-based liquid propellant droplet was built, and the droplet temperature and the radius versus time curves were calculated when a LP1845droplet evaporates in a high-temperature, high-pressure nitrogen environment. The results indicate that the droplet radius increases firstly and reduces afterward as the evaporation goes on, and the reduction rate of the radius satisfies the D2law. The droplet temperature rises rapidly at the beginning, then maintains stable gradually at an equilibrium value. When the ambient temperature remains constant, with increasing ambient pressure, the time to reach the equilibrium temperature lengthens, but the droplet lifetime shortens. (4) Considering the liquid-gas interphase mass transfer, surface tension and gas component transport, the droplet evaporation mass transfer source term was derived. A theoretical model for the HAN-based liquid propellant droplet evaporation in a convection nitrogen environment was set up based on the theory of VOF two phase flow. The variation regularity of the flow field around the evaporating LP1846droplet was studied, and the Stefan flow around the droplet surface and the swirl at the droplet tail were also captured successfully.(5) Considering the gas-phase chemical reaction at the droplet surface, a simplified combustion model applicable to the HAN-based liquid propellant droplet was established. Based on the model, the mass burning rate and the droplet lifetime under different ambient temperatures were calculated when a LP1846single droplet combusts in a stationary atmospheric environment. The results show that the mass burning rate accelerates with increasing ambient temperature, and the higher the temperature, the faster the rate increases. The droplet lifetime gets longer as the ambient temperature increases. The model is valid by comparing the calculation results with the experimental data.(6) A device for measuring the linear burning rate of HAN-based liquid propellants at high pressures was designed. The high-pressure environments were generated by the combustion of solid propellants. The coated propellants which burn progressively were introduced to maintain the approximate constant-pressure environments. The spread velocity of the combustion flame surface was measured by virtue of the measuring velocity technology of ion probe. Based on the experimental device, the apparent linear burning rates of AF-315at29.4-55.0MPa and LP1846at6～28MPa was measured, respectively.(7) Referencing the steady-state combustion theory of the solid propellant, the concept of the liquid propellant one-dimensional combustion wave structure was put forward. A one-dimensional simplified model of the steady-state combustion of HAN-based liquid propellant column was developed, and the relational expression between the burning rate and the ambient pressure was also obtained. Based on the model, the burning rates of LP1846at6～28MPa was calculated. The maximum error is3.2%between the simulation results and the experimental data, which shows that the simplified model is valid.(8) A two-dimensional high-pressure steady-state combustion model for the HAN-based liquid propellant was built by use of the VOF two-phase numerical simulation method. The combustion process of AF-315in a high pressure strand burner was simulated, and the variation regularities of the temperature, pressure and velocity were researched. The liquid surface movement throughout the combustion process was captured successfully, and the burning rates of AF-315under different ambient pressures were obtained. This method is feasible by comparing the simulation results with the experimental data, so it can be used to simulate the high-pressure combustion process of HAN-based liquid propellants.更多还原