叶型孔式预旋喷嘴流动特性数值研究

Numerical Investigation on Flow Characteristics of a Vane

关键词:  预旋系统  预旋喷嘴  叶片  流量系数  预旋效率

Key words:  Preswirl system  Preswirl nozzle  Vane  Discharge coefficient  Preswirl effectiveness

摘要:

现有研究表明叶片式喷嘴是目前为止性能最好的预旋喷嘴。而在整环的喷嘴盘设计中，当喷嘴总面积、预旋角度、喷嘴数目和半径位置确定后，喷嘴叶高和栅距就固定下来，往往因为叶高与栅距的比值过小而大大降低喷嘴性能。在叶片式喷嘴基础上提出了一种能够调整喷嘴叶高到恰当值的新型预旋喷嘴——叶型孔式喷嘴(vane shaped hole nozzle，vsh nozzle)。采用数值方法深入对比研究了叶型孔式喷嘴与叶片式喷嘴的性能差异。为了考虑喷嘴下游预旋腔的掺混影响，计算域不仅包括静止的进气腔和喷嘴，还包括转动的预旋腔和接受孔。计算结果表明，叶型孔式预旋喷嘴的流量系数和预旋效率显著高于叶片式喷嘴，vsh-52喷嘴的流量系数比vane-52喷嘴高9.14%，预旋效率高4.44%。还提出采用有效流量系数、有效预旋效率两个参数来体现考虑喷嘴下游预旋腔掺混影响的喷嘴综合性能。

Abstract:

Investigations on preswirl nozzle show that the cascade vane nozzle is the best one so far. While in the design of whole circular nozzle disc，the blade height and blade spacing will be settled with the throat area，preswirl angle，number and radial position of nozzle decided. If the ratio between blade height and blade spacing is too small，it will reduce the performance of nozzle significantly. Based on the vane nozzle，a new kind of preswirl nozzle called vane shaped hole preswirl nozzle(vsh nozzle for short) is proposed，with which the ratio of blade height against blade spacing can be adjusted to a more appropriate value. The flow characteristics of vane nozzle and vane shaped hole nozzle are compared numerically . To consider the mixing influence of preswirl cavity downstream the nozzle，the computational models contain not only the stationary inlet chamber and preswirl nozzle ，but also the rotary preswirl cavity and receiver hole. Results show that the discharge coefficient and preswirl effectiveness of the vsh nozzle are higher remarkably than that of vane nozzle. The discharge coefficient of the vsh-52 preswirl nozzle increased by 9.14% comparing with that of the vane-52 nozzle，and the preswirl effectiveness increased by about 4.44%. Two new parameters called effective discharge coefficient and effective preswirl effectiveness are also proposed to reflect the comprehensive performance considering the mixing influence of preswirl cavity downstream the nozzle.