多层涡轮机匣内螺栓对换热特性影响的试验研究

Experimental Study of Effects of Bolts Inside Multilayer Turbine Casing on Heat Transfer Characteristics

关键词:  高压涡轮机匣  主动间隙控制  定位螺栓  换热特性  经验关系式

Key words:  High pressure turbine casing  Active clearance control  Set bolt  Heat transfer characteristics  Empirical formulas

摘要:

针对叶尖间隙主动控制系统的高压涡轮多层机匣，研究了机匣内部斜向冲击高肋结构中，定位螺栓对机匣换热特性的影响规律。试验中改变孔平均雷诺数[Re]([2543~7121])、螺栓直径与冲击孔直径比[Dd](2.67，4.13，5.33)、螺栓间距与冲击孔直径比[Sd](23.2，30.7，45.2)等参数，获得了不同工况下螺栓安装面局部和平均[Nu]数变化规律，并整理出对应的经验关系式。研究中发现，安装螺栓的存在，显著增强了机匣表面的局部换热效果，但是平均换热系数的提升幅度有限。研究结果表明，在本文试验参数范围内，当保持螺栓间距比不变时，增加螺栓直径可以有效强化机匣表面的换热系数，如当螺栓直径比[Dd]由2.67增加到5.33时，螺栓周围机匣表面平均[Nu]数增加幅度达20%～30%。当螺栓直径比保持不变的工况中，螺栓间距比[Sd]为[30.7]时机匣表面平均[Nu]数达到最大值，但是螺栓间距比参数对机匣表面换热系数影响相对较小，平均[Nu]数的变化幅度在10%以内。

Abstract:

According to multilayer casing of high pressure turbine with active clearance control system，experiments were conducted to investigate the effects of embedded bolts on heat transfer characteristics，which inside the oblique?impact high rib structure of the turbine casing. In experiments，the average Reynolds number [Re]([2543~7121])，the ratio of bolt diameter to jet holes diameter [Dd](2.67，4.13，5.33) and the spacing ratio [Sd] (23.2，30.7，45.2) were changed to investigate the local and average heat transfer coefficient [Nu](Nusselt number). The empirical formulas of average heat transfer with [Dd] and [Sd] were also obtained. It was found that the existence of the bolts enhanced the local [Nu]，but the enhancement of the average [Nu] was limited. Within the range of research parameters，if the bolts’ spacing ratio remained constant，increase of the bolt diameter can effectively strengthen the heat transfer on the turbine casing surface around the embedded bolts，i.e. average [Nu] rose by 20% ～ 30% with the bolt diameter ratio [Dd] increasing from 2.67 to 5.33. If the [Dd] was constant，maximum [Nu] was obtained when [Sd] was 30.7. However，[Sd] affected the heat transfer on the turbine casing surface faintly，and the variation of the average [Nu] was within 10%.