Experimental Study of the Unsteady Boundary Layer Behavior on a Turbine Cascade

Abstract

The unsteady boundary layer behavior on a turbine cascade is experimentally investigated and the results are presented in this paper. To perform a detailed study on unsteady cascade aerodynamics and heat transfer, a new large-scale, high-subsonic research facility for simulating the periodic unsteady flow has been developed. It is capable of sequentially generating up to four different unsteady inlet flow conditions that lead to four different passing frequencies, wake structures, and freestream turbulence intensities. For a given Reynolds number, three different unsteady wake formations are utilized. Detailed unsteady boundary layer velocity, turbulence intensity, and pressure measurements are performed along the suction and pressure surfaces of one blade. The results presented in the temporal-spatial domain display the transition and further development of the boundary layer, specifically the ensemble-averaged velocity and turbulence intensity.

Effect of Reynolds Number and Periodic Unsteady Wake Flow Condition on Boundary Layer Development, Separation, and Intermittency Behavior Along the Suction Surface of a Low Pressure Turbine Blade

“…However, the above investigations were not sufficient to draw any conclusion with regard to an eventual universal character of the relative intermittency function. Further detailed investigations of the unsteady boundary layer on a high Reynolds number turbine cascade by Schobeiri et al [9,10] and its subsequent analysis [ 11,12] verified the universal character of the relative intermittency function. For this purpose, Schobeiri et al [9] utilized a conceptually different type wake generator, which is also used for the investigation presented in this paper.…”

“…Further detailed investigations of the unsteady boundary layer on a high Reynolds number turbine cascade by Schobeiri et al [9,10] and its subsequent analysis [ 11,12] verified the universal character of the relative intermittency function. For this purpose, Schobeiri et al [9] utilized a conceptually different type wake generator, which is also used for the investigation presented in this paper. Fottner and his coworkers [ 13,14] and Schulte and Hodson [ 15] used the same wake generating concept for the investigations on the influence of the unsteady wake flow on the LPT-boundary layer.…”

“…Considering this fact, the research facility described in Refs. [9,10] , with state-of-the-art instrumentation, has been substantially modified to systematically and efficiently study the influence of the periodic unsteady and highly turbulent flow on the LPT cascade aerodynamics at the design and off-design incidence angles, where the Reynolds number, wake impingement frequency, free-stream turbulence, and the blade solidity can be varied independently.…”

Periodic Unsteady Flow Aerodynamics and Heat Transfer: Studies on a Curved Surface, Combined Part I and II

“…Consequently, the intermittency again increases to approach unity, showing the combined effect of wake-induced and natural transition due to an increased turbulence intensity level. The damping process of the high turbulence intensity wake flow discussed above explains the phenomena of the becalming effect, a wake induced transition observed by several researchers (Pfeil and Herbst, 1979;Orth, 1992;Schobeiri et al, 1995). Figure 13 also shows the average intermittency that is a result of the integral effect of periodic wakes with respect to time.…”

“…LaGraff et al (1989), Ashworth et al (1989), Liu and Rodi (1992), and Schobeiri et al (1995b) studied the wake effect in a linear turbine cascade facility. Boundary layer transition models for wake-induced transition have been developed by Walker (1974), Doorly (1988), Sharma et al (1988), Addison and Hodson (1990a,b), and Mayle and Dullenkopf (1989,1991).…”