向心涡轮可调导向叶栅内流动损失机理的分析

通过对向心涡轮可调导向叶栅三维流场数值模拟,分析在不同叶片安装角下,可调叶片表面静压系数和出口总压损失系数的变化规律。导叶安装角从21°增加到44°,通流面积调节范围为50%～116%设计通流面积。结果表明:叶栅开度减小时,叶片的气动负荷增加,总压损失增加。与设计工况相比,导叶关小15°总压损失增加了1倍多。叶栅端部间隙增加了导向叶栅的流动损失,间隙增加2%,损失增加1.5%,端部损失范围从20%叶高增加到40%叶高。叶栅开度减小,端部损失与叶型损失的变化较小,而间隙损失无论是数量还是占总压损失的比重都明显增加,是非设计工况下总压损失增加的主要原因。

Flow Loss Mechanism in Radial Variable Area Nozzles

Three dimensional flow fields of the variable area nozzle for radial turbines were calculated with CFD method. The static pressure contours and total pressure loss coefficients distribution were calculated with respect to different setting angles. Setting angle vary from 21° to 44° in the numerical model. Throat area changes from 50% to 116% of design one. The results show that with the guide vanes closing, blade loading and total pressure loss increase. Compared with the design conditions, total pressure loss increases by one time when the opening is - 15°. Tip clearance increases flow loss of cascade. Tip clearance of 2 percent indicates approximate 1.5 percent total pressure loss while tip leakage mass flow rate is increased for near 1.3 percent range of endwall loss increases from 20% to 40% of span. When the opening decreases, endwall loss and profile loss have small increase. But clearance loss and proportion enhance significantly. Increase of clearance loss with the opening is main reason for total loss increase in off design condition.