An Investigation into Turbine Blade Tip Leakage Flows at High Speeds
The effect of the blade tip geometry of a high pressure
gas turbine is studied experimentally and computationally for high
speed leakage flows. For this purpose two simplified models are
constructed, one models a flat tip of the blade and the second models
a cavity tip of the blade. Experimental results are obtained from a
transonic wind tunnel to show the static pressure distribution along
the tip wall and provide flow visualization. RANS computations
were carried to provide further insight into the mean flow behavior
and to calculate the discharge coefficient which is a measure of the
flow leaking over the tip. It is shown that in both geometries of tip
the flow separates over the tip to form a separation bubble. The
bubble is higher for the cavity tip while a complete shock wave
system of oblique waves ending with a normal wave can be seen for
the flat tip. The discharge coefficient for the flat tip shows less
dependence on the pressure ratio over the blade tip than the cavity
tip. However, the discharge coefficient for the cavity tip is lower than
that of the flat tip, showing a better ability to reduce the leakage flow
and thus increase the turbine efficiency.
[1] Bunker RS, (2004), "Blade tip heat transfer and cooling techniques", VKI
Lecture Series 2004-02.
[2] Bryant RAA (1960) "The Hydraulic Analogy for External Flow", Journal
of the Aerospace Sciences, Vol. 27, No. 2 , pp. 148-149.
[3] Moore J, Elward KM, (1993) "Shock formation in over expanded tip
leakage flow", ASME Journal of turbomachinary, vol.115, pp 392-399
[4] Chen G, Dawes WN, Hodson HP, (1993) "A numerical and experimental
investigation of turbine tip gap flow" 29th Joint Propulsion Conference
and Exhibit, AIAA 93-2253.
[5] Wheeler, A.P.S., Atkins N., and He, L. 2009 "Turbine blade tip heat
transfer in low speed and high speed flows", GT 2009-59404, presented
at the ASME Turbo Expo 2009, Orlando, Florida.
[6] Korakianitis T, Hamakhan I, Rezaienia MA, Wheeler APS, Avital EJ and
Williams JJR (2012), Design of high-efficiency turbomachinery blades
for energy conversion devices with the 3D prescribed surface curvature
distribution blade design (CIRCLE) method. Applied Energy, Vol. 89 No.
1, pp. 215-227.
[7] Doulgeris G, Korakianitis T, Avital EJ, Pilidis P. and Laskaridis P., Effect
of jet noise reduction on gas turbine engine efficiency Proc IMechE Part
G: J Aerospace Engineering, 0954410012456925, first published on
September 3, 2012.
[1] Bunker RS, (2004), "Blade tip heat transfer and cooling techniques", VKI
Lecture Series 2004-02.
[2] Bryant RAA (1960) "The Hydraulic Analogy for External Flow", Journal
of the Aerospace Sciences, Vol. 27, No. 2 , pp. 148-149.
[3] Moore J, Elward KM, (1993) "Shock formation in over expanded tip
leakage flow", ASME Journal of turbomachinary, vol.115, pp 392-399
[4] Chen G, Dawes WN, Hodson HP, (1993) "A numerical and experimental
investigation of turbine tip gap flow" 29th Joint Propulsion Conference
and Exhibit, AIAA 93-2253.
[5] Wheeler, A.P.S., Atkins N., and He, L. 2009 "Turbine blade tip heat
transfer in low speed and high speed flows", GT 2009-59404, presented
at the ASME Turbo Expo 2009, Orlando, Florida.
[6] Korakianitis T, Hamakhan I, Rezaienia MA, Wheeler APS, Avital EJ and
Williams JJR (2012), Design of high-efficiency turbomachinery blades
for energy conversion devices with the 3D prescribed surface curvature
distribution blade design (CIRCLE) method. Applied Energy, Vol. 89 No.
1, pp. 215-227.
[7] Doulgeris G, Korakianitis T, Avital EJ, Pilidis P. and Laskaridis P., Effect
of jet noise reduction on gas turbine engine efficiency Proc IMechE Part
G: J Aerospace Engineering, 0954410012456925, first published on
September 3, 2012.
@article{"International Journal of Mechanical, Industrial and Aerospace Sciences:58083", author = "Z. Saleh and E. J. Avital and T. Korakianitis", title = "An Investigation into Turbine Blade Tip Leakage Flows at High Speeds", abstract = "The effect of the blade tip geometry of a high pressure
gas turbine is studied experimentally and computationally for high
speed leakage flows. For this purpose two simplified models are
constructed, one models a flat tip of the blade and the second models
a cavity tip of the blade. Experimental results are obtained from a
transonic wind tunnel to show the static pressure distribution along
the tip wall and provide flow visualization. RANS computations
were carried to provide further insight into the mean flow behavior
and to calculate the discharge coefficient which is a measure of the
flow leaking over the tip. It is shown that in both geometries of tip
the flow separates over the tip to form a separation bubble. The
bubble is higher for the cavity tip while a complete shock wave
system of oblique waves ending with a normal wave can be seen for
the flat tip. The discharge coefficient for the flat tip shows less
dependence on the pressure ratio over the blade tip than the cavity
tip. However, the discharge coefficient for the cavity tip is lower than
that of the flat tip, showing a better ability to reduce the leakage flow
and thus increase the turbine efficiency.", keywords = "Gas turbine, blade tip leakage flow, transonic flow.", volume = "7", number = "1", pages = "64-5", }