Clocking Effects in a 1.5 Stage Axial Turbine—Steady and Unsteady Experimental Investigations Supported by Numerical Simulations

Abstract

The interaction between rotor and stator airfoils in a multistage turbomachine causes an inherently unsteady flow field. In addition, different relative circumferential positions of several stator rows and rotor rows, respectively, have an influence on the flow behavior in terms of loss generation, energy transport and secondary flow. The objective of the presented study is to investigate the effects of stator airfoil clocking on the performance of a 1-1/2 stage axial cold air turbine. The investigated axial turbine consists of two identical stators. The low aspect ratio of the blades and their prismatic design leads to a three-dimensional outlet flow with a high degree of secondary flow phenomena. Nevertheless, the small axial gaps between the blade rows are responsible for strong potential flow interaction with the radial wake regions in the measurement planes. Consequently, parts of the wakes of the first stator are clearly detected in the rotor outlet flow. To give an overview of the time-averaged flow field, measurements with pneumatic probes are conducted behind each blade row at ten different clocking-positions of the second stator. Further, an optimized clocking position was found due to a minimum in pressure loss behind the second stator. The unsteady measurements are carried out with hot-wire probes for three selected stator-stator positions. Animations of selected flow properties show the influence of different circumferential positions of the second stator on the unsteady flow behavior and secondary flow field. In addition and compared with experimental results three-dimensional unsteady viscous flow computations are performed.

Effect of clocking on unsteady rotor blade loading in a low-speed axial compressor at design and off-design operating conditions

“…Further investigations on the effect of clocking on the performance were done by Reinmoeller et al [4], Arnone et al [5], and Bohn et al [6].…”

Unsteady Aerodynamics, Aeroacoustics and Aeroelasticity of Turbomachines

“…A number of experimental and numerical studies have been carried out in recent years to investigate these flow phenomena [e.g. Arnone et al 2000Arnone et al , 2002, Eulitz 2000Haldeman et al, 2003;He et al 2002, Howel et al 2001, Huber 1996, Hummel 2002Jouini et al 2003;Reinmoeller et al 2002, Saren et al 2002. The experimental work presented herein is the continuation of our earlier studies, starting from mid-nineties [e.g.…”

Vane Clocking Effects on Stator Loss for Different Compressor Loading Conditions

“…Much of the available clocking literature involves turbine applications, where as much as a a 2% stage efficiency benefit has been observed with optimal clocking [2][3][4]. These turbine experiments are supported by computational clocking studies [4,5], which show the potential for changes in stage efficiency from 0.7 to 2% with vane clocking.…”

“…These turbine experiments are supported by computational clocking studies [4,5], which show the potential for changes in stage efficiency from 0.7 to 2% with vane clocking. Furthermore, it is generally agreed that, for turbines, the CL LE clocking configuration is the most efficient case, and the CL MP clocking configuration is the least efficient.…”