Mixing Control System Using Micro Nozzle of 3D Vortex Generator and Flame holder Aiming at High-Speed Diffusion Combustion

对于微型涡轮燃烧室来说，在高速流动中加强火焰保持和混合是使燃烧室紧凑和实现等温膨胀燃烧的关键。为此，我们提出了一种小尺寸的组合喷嘴和火焰支架。即在相对高温气流的下游，引入一个形状类似天使鱼的微小物体作为喷油器：在喷油器的背面，产生强烈的湍流。在实验中，我们首先准备了一个高速高温风洞。获得的最大速度为105m/s，温度为550℃。其次，采用比最终喷油器大2 ~ 3倍的v型和u型喷油器，获得基本的混合和保焰特性；它们的长度和宽度分别为1.5mm和1mm。v形喷射器的阻焰性能优于u形喷射器，表明了天使鱼型微喷射器的有效性。另一方面，为了更详细地阐明微喷射器背面的混合机理，采用k-e湍流模型进行了不同喷嘴几何形状的数值计算，作为数值分析的第一步，分析了凹壁面后台阶周围的流动。结果表明，当壁面为凹壁面时，回流带的流向长度减小。在凹壁上安装了燃油喷射孔，凹壁上的速度约为主流的1%。这些事实在混合增强方面是可取的。从2000-2002年的实验和理论研究中，我们得出结论，目前的微型喷油器作为高速扩散燃烧的高潜力已经得到证实。微型涡轮燃烧室的实际应用目前正在进行中。

For combustors of microturbines, enhancement of flame holding and mixing in a high-speed flow is crucial to make the combustor compact and also realize isothermal expansion combustion. To this end, we propose a combined nozzle and flame holder with small dimensions. That is, in the downstream of relatively high-temperature gas flow, a micro object, the shape of which is similar to an angel fish, is introduced as a fuel injector: on the back side of the injector, intense turbulence is generated.In the experiment, first, we prepared a high-speed and high-temperature wind tunnel. The attained maximum velocity and temperature were 105m/s and 550℃, respectively. Secondly, V-type and U-type fuel injectors which are two or three times larger than the final ones were used to obtain fundamental mixing and flame holding characteristics; their length and width are 1.5mm and 1mm, respectively. The V-shaped injector shows higher flame holding performance than the U-shaped injector, which indicates the validity of an angel-fish type micro injector.On the other hand, to clarify the mixing mechanism on the back side of the micro injector in detail, a numerical calculation using k-e turbulence model was conducted varying the injector geometry, As a first step of the numerical analysis, a flow around backward facing step with concave wall was analyzed. It was found that for the case with the concave wall the streamwise length of a recirculation zone decreases. The velocity near the concave wall, where fuel-injection holes are installed, was about 1% of that of the main flow. These facts are preferable in terms of the mixing enhancement.From the experimental and theoretical studies during 2000-2002, we conclude that the high potential of the present micro fuel injector as a high-speed diffusion combustion has been confirmed. An actual application to a microturbine combustor is now in progress.