气膜冷却平板表面颗粒物沉积的实验研究

Experimental Study on Particle Deposition of Plate Surface with Film Cooling

关键词:  石蜡颗粒  气膜冷却  沉积  吹风比  射流角度  冷却效率

Key words:  Wax particles  Film cooling  Deposition  Blowing ratio  Injection angle  Cooling effectiveness

摘要:

为了解涡轮叶片表面颗粒物的沉积规律和沉积对气膜冷却的影响，实验通过石蜡喷涂装置将熔融石蜡颗粒喷入到小型风洞中，石蜡颗粒沉积在具有气膜冷却的平板表面上来模拟涡轮叶片上的颗粒物沉积过程。实验中将表征石蜡熔融颗粒尺寸的斯托克斯数与实际燃气涡轮发动机中的煤灰颗粒相匹配，通过调节主流温度，保持石蜡颗粒在沉积前处于熔融状态来模拟真实涡轮叶片上颗粒物的粘附机理，观察没有气膜冷却情况下的石蜡沉积过程和有气膜冷却情况下，不同吹风比和不同射流角度对石蜡沉积的影响，以及石蜡沉积后对平板表面气膜冷却的影响。研究发现石蜡熔融温度与主流温度相接近时，更容易沉积在平板表面，并且石蜡沉积在生长到一定厚度后不再增长。在有气膜冷却的情况下，吹风比从0增加到1.5时，平板表面石蜡沉积先减少后增加，吹风比为0.5时，石蜡沉积最少。射流角度由30°增加到90°时，平板表面石蜡沉积逐渐增多。石蜡沉积降低了平板气膜冷却效率，并且气膜孔间下游区域的温度比气膜孔下游区域更高。

Abstract:

In order to understand the deposition regularity of particulate matter on the surface of the turbine blade and the effects of deposition on the cooling of the film， the wax particles was sprayed into small wind tunnel by wax spraying apparatus in this experiment. The wax was deposited on the surface of the plate with film cooling to simulate the deposition process of the particles on the turbine blades. The Stokes number， which characterized the size of the wax melting particles， was matched with the particles of coal ash in the actual gas turbine engine. By adjusting the mainstream temperature， the wax particles were kept in a molten state before deposition to simulate the adhesion of the particles on the real turbine blades. The effects of different blowing ratios and different injection angles on the deposition of wax and the effects of wax deposition on the film cooling of the flat surface were observed in the process of wax deposition with and without film cooling. It was found that when the melting temperature of paraffin wax is close to the mainstream temperature， it is easier to deposit on the surface of the plate， and the paraffin deposition does not increase after growing to a certain thickness. In the case of film cooling， when the blowing ratio increases from 0 to 1.5， the deposition of wax on the surface of the flat plate decreases first and then increases， and the deposition of wax is the least when the blowing ratio is 0.5. With the injection angle increased from 30° to 90°， the deposition of wax on the plate surface gradually increases. Wax deposition reduces the cooling effectiveness of the flat membrane， and the temperature of the downstream region between the film holes is higher than that of the downstream region of the film holes.