Abstract
This paper aims at evaluating the characteristics of the wakes periodically shed by the rotating bars of a spoked-wheel type wake generator installed upstream of a high-speed low Reynolds linear low-pressure turbine blade cascade. Due to the very high bar passing frequency obtained with the rotating wake generator (fbar = 2.4−5.6 kHz), a fast-response pressure probe equipped with a single 350 mbar absolute Kulite sensor has been used. In order to measure the inlet flow angle fluctuations, an angular aerodynamic calibration of the probe allowed the use of the virtual three-hole mode; additionally, yielding yaw corrected periodic total pressure, static pressure and Mach number fluctuations. The results are presented for four bar passing frequencies (fbar = 2.4/3.2/4.6/5.6 kHz), each tested at three isentropic inlet Mach numbers M1,is = 0.26/0.34/0.41 and for Reynolds numbers varying between Re1,is = 40,000 and 58,000, thus covering a wide range of engine representative flow coefficients (ϕ = 0.44−1.60). The measured wake characteristics show fairly good agreement with the theory of fixed cylinders in a cross-flow and the evaluated total pressure losses and flow angle variations generated by the rotating bars show fairly good agreement with theoretical results obtained from a control volume analysis.
Highlights
This paper aims at evaluating the characteristics of the wakes periodically shed by the rotating bars of a spoked-wheel type wake generator installed upstream of a high-speed low Reynolds linear low-pressure turbine blade cascade
The results are presented for four bar passing frequencies, each tested at three isentropic inlet Mach numbers M1,is = 0.26/0.34/0.41 and for Reynolds numbers varying between Re1,is = 40,000 and 58,000, covering a wide range of engine representative flow coefficients (φ = 0.44−1.60)
The measured wake characteristics show fairly good agreement with the theory of fixed cylinders in a cross-flow and the evaluated total pressure losses and flow angle variations generated by the rotating bars show fairly good agreement with theoretical results obtained from a control volume analysis
Summary
For the purpose of investigating the effects of unsteady wake–boundary layer interactions on the aerodynamic performance of (high-lift) low-pressure turbine airfoils in linear cascades, periodic wake generators placed upstream of the cascade and equipped with linearly moving or rotating cylindrical bars are commonly used. Of an airfoil and that of a cylindrical body of the same drag is almost identical In their own work investigating unsteady wake–boundary layer interactions in low-pressure turbine cascades, Schulte and Hodson [2] have further shown that this holds true for values of xw /d ranging between 40 and 80. In order to simulate these rotor–stator interactions as accurately as possible, the flow coefficient φ (ratio between axial inflow velocity and peripheral velocity) as well as the reduced bar passing frequency fr (ratio between the characteristic convective time of the wake through the blade passage and the characteristic time between two consecutive wakes) need to be correctly matched with the values typically encountered in real-life low-pressure turbines.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: International Journal of Turbomachinery, Propulsion and Power
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
