HEAT TRANSFER CHARACTERISTICS OF NEW COOLING TECHNIQUE BASED ON THERMAL DRIVING

新型涡轮叶片冷却技术换热特性实验研究(英文)

A new cooling technique based on thermal driving in high centrifugal field （TDHCF） is developed for gas turbine rotational components, such as turbine blades. The key point of TDHCF is to enhance heat transfer by the fluid thermal driving in closed loop small channels placed in the high centrifugal field. Heat transfer characteristics of the new cooling technique are analyzed. In experiments, two different fluids （liquid water and Freon R12） are used as thermal driving media （fluid inside the loop channel）. And the channel width d is 1 mm and the height h is 30 mm. The temperature is measured by thermocouples and an average heat transfer coefficient KH is defined to indicate heat transfer capacity of TDHCF. Experimental results show that KH is enhanced when heat flux and the rotating speed increase. And thermal properties of thermal driving media are also influenced by KH. Larger KH can be achieved by using Freon R12 as thermal driving medium compared with using liquid water. It can increase to 2 300 W/（m^2 · K） and it is much higher than that of the normal air cooling method （usually at the level of 600-1200 W/（m^2·K））. All fundamental studies of TDHCF show that there actually exists thermal driving in the closed loop small channel in the centrifugal field to improve heat transfer characteristics.

通过实验研究了一种新型涡轮叶片冷却技术(Ther-mal driving in high centrifugal field,TDHCF)的换热特性。该技术主要利用高彻体力场下微小封闭循环通道内流体的热驱动运动来达到高效换热的目的。实验中分别采用了液态H2O和氟利昂R12为热驱动介质,分析了离心力场下热驱动运动的流动规律和换热特性,讨论了TDHCF技术的总平均换热效果KH随旋转速度和热流密度的变化规律。研究发现:离心力场下,采用不同的流体作为热驱动介质所形成的热驱动运动规律相同,温度分布也基本类似,均是随着转速和热流密度的增加,热驱动运动强度提高,平均换热系数随之变大。研究结果表明:旋转速度、热流密度以及热驱动介质的热物性均影响了TDHCF所最终能达到的换热效果,其中旋转速度的影响尤为显著;在热流密度或转速不变的情况下,以液态氟利昂R12为热驱动介质,TDHCF可以达到更高的强化换热效果。与常规的气冷技术相比,采用TDHCF可以有效地提高换热效果。