Turbine Platform Cooling and Blade Suction Surface Phantom Cooling From Simulated Swirl Purge Flow

Abstract

This paper presents the swirl purge flow on a platform and a modeled land-based turbine rotor blade suction surface. Pressure-sensitive paint (PSP) mass transfer technique provides detailed film-cooling effectiveness distribution on the platform and phantom cooling effectiveness on the blade suction surface. Experiments were conducted in a low-speed wind tunnel facility with a five-blade linear cascade. The inlet Reynolds number based on the chord length is 250,000. Swirl purge flow is simulated by coolant injection through 50 inclined cylindrical holes ahead of the blade leading edge row. Coolant injections from cylindrical holes pass through nozzle endwall and a dolphin nose axisymmetric contour before reaching the platform and blade suction surface. Different “coolant injection angles” and “coolant injection velocity to cascade inlet velocity” result in various swirl ratios to simulate real engine conditions. Simulated swirl purge flow uses coolant injection angles of 30 deg, 45 deg, and 60 deg to produce swirl ratios of 0.4, 0.6, and 0.8, respectively. Traditional purge flow has a coolant injection angle of 90 deg to generate swirl ratio of 1. Coolant to mainstream mass flow rate (MFR) ratio is 0.5%, 1.0%, and 1.5% for all the swirl ratios. Coolant to mainstream density ratio maintains at 1.5 to match engine conditions. Most of the swirl purge and purge coolant approach the platform; however, a small amount of the coolant migrates to the blade suction surface. Swirl ratio of 0.4 has the highest relative motion between rotor and coolant and severely decreases film cooling and phantom cooling effectiveness. Higher MFR of 1% and 1.5% cases suffers from apparent decrement of the effectiveness while increasing relative motion.

Assessment of binary PSP technique for film cooling effectiveness measurement on nozzle vane cascade with cutback trailing edge

“…The cascade was tested at different exit Mach numbers ranging from Ma2,is = 0.2 up to 0.6, corresponding to a Re2,is variation from 6.5x10 5 to 1.6x10 6 , and at a low Tu1 of 1.6% (Table 2). Tests were performed using the binary PSP technique, injecting air and N2, with the coolant to mainstream mass flow ratio (MFR) ranging from 0.8% to 2.8%.…”

“…3, such a (negative) temperature mismatch will result in an underestimation of pressure ratio when injecting nitrogen (if data processing is based on a unique calibration curve, as typically is). This will translate into an overestimation of film cooling effectiveness, according to equation (6). Please note that compressibility effects, if relevant, are expected to act differently, as this time a temperature mismatch will exist between both cooling (air and nitrogen) and reference (wind off) conditions.…”

“…In this review paper results from the application of single component PSP technique on a flat plate model as well as on airfoils and platforms, both in stationary and rotating condition, are put together to demonstrate the ability of this technique to provide detailed and accurate adiabatic film cooling effectiveness distributions on complicated geometries. In fact, Li et al [6] have shown that, differently from TLC technique, PSP signal is practically unaffected by surface curvature, allowing to obtain useful data over complicated geometries. Moreover, opposite to IR Thermography, PSP technique does not require particular optical windows, making its application cheaper and easier.…”

The Aero-Thermal Performance of Purge Flow and Discrete Holes Film Cooling of Rotor Blade Platform in Modern High Pressure Gas Turbines: A Review

“…The former family of experimental facilities may simulate rotation effects through swirl motion or fin introduction. Most of these researches were carried out at Texas A and M University on a five-blade cascade test facility [13][14][15][16][17][18][19][20], at the University of Bergamo on a seven-blade cascade test facility [21][22][23][24][25][26] and at Whittle Laboratory of the University of Cambridge [27,28]. Meanwhile, the latter family of experiments (rotating platforms) were carried out in the TPFL-research turbine facility at Texas A and M University [29,30], in the CT3 compression tube turbine test rig at the von Karman Institute [31], at Ohio State University Turbine Test Facility (TTF) [32][33][34], at the LISA research turbine available at ETH Zurich [35,36] and, more recently, at the Large Annulus Rig (LAR) of the University of Bath [37,38].…”

“…Figure10. Rotor platform pitch averaged film cooling effectiveness at MFR = 1.0% for different cooling slot configurations: S2r at design rotational speed[29], S1 and S1f with −10 • fins[22], S1 and S1s with SR = 0.4[17], S2 with simulated stator effect[20].…”