Basic study for developing supercritical spray combustion simulator

通过数值模拟，研究了燃料液滴突然置于静止的惰性/氧化性气体中，在超过临界点的不同状态下的蒸发/凝结特性。充分揭示了汽化/燃烧特性及其基本物理特性。对于给定的环境气体温度，最小气化/燃烧时间是在这样的压力下实现的，即液滴在暴露于热惰性气体或点燃后立即呈现的表面温度与“混合物”临界温度一致。该压力远高于在相对低的温度下在环境气体中气化的液滴的燃料临界压力，而火焰的存在使其非常接近燃料临界压力。在环境气体温度和压力的参数空间中，确定了三种液滴汽化模式：（1）在亚临界汽化区， 关于我们 在我看来，液滴在其整个生命周期中都具有表面。(2)在超临界气化制度，空间连续的相变发生从一开始。(3)建立了一个广义渐近理论，对喷雾中液滴的蒸发和燃烧特性进行了研究.在高压下，由于每个液滴的影响范围被限制在很短的距离内，因此喷雾可以被视为独立液滴压力的集合。为了将现有的低压喷雾燃烧模拟器改造为高压喷雾燃烧模拟器，发展了一种新的数值计算方法，该方法综合考虑了液滴固有的非定常汽化和燃烧特性，可以用拉格朗日方法来追踪大量液滴的运动。研究了液滴表面张力减小或消失时出现的动力学现象，以接近超临界条件下喷雾的隐蔽动力学行为。少

Numerical simulations were performed to examine the vaporization/cobustion characteristics for a liquid fuel droplet which was suddenly placed in an otherwise quiescent, inert/oxidizing gas at various status beyond the critical point of the fues. The vaporization/combustion characteristics were fully disclosed, together with their underlying physics. For a given ambient gas temperature, the minimum gasification/combustion time is achieved at such a pressure that the surface temperature which the droplet assumes immediately after its exposure to the hot inert gas or ignition coincides with the 'mixture' critical temperature. This pressure is far above the fuel critical pressure for a droplet gasifying in the ambient gas at a relatively low temperature, whereas the presence of flame shifts it very cose to the fuel critical pressure. Three modes of droplet vaporization were identified in the parameter space of ambient gas temperature and pressure ; (1) In the subcritical vaporization regi … More me, the droplet has the surface throughout its lifetime. (2) In the supercritical gasification regime, spatially continuous phase change occurs from the beginning. (3) Between them, there is the transient vaporization regime in which the transition from the sub-to-supercritical vaporization mode takes place.A generalized asymptotic theory was constructed to gain insight into the interactive droplet vaporization and combustion property in spray. At high pressures, a spray can be regarded as an ensemble of independent droplets pressures because the range of influence of each droplet is restricted within a short distance. A new numerical calculation method which incorporates the inherently unsteady droplet vaporization and combustion property was developed in order to transform a low-pressure spray combustion simulator at hand to a high-pressure one, in which the movements of a great number of droplets can be pursued in a Lagrangian way. Dynamic phenomena which would appear when the surface tension of droplet diminishes or vanishes were examined to approach the masked dynamic behaviors of sprays in supercritical conditions. Less