Boundary Layer Control on a Low Pressure Turbine Blade by Means of Pulsed Blowing

Abstract

The current work investigates the performance benefits of pulsed blowing with frequencies up to 10 kHz on a highly loaded low pressure turbine (LPT) blade. The influence of blowing position and frequency on the boundary layer and losses are investigated. Pressure profile distribution measurements and midspan wake traverses are used to assess the effects on the boundary layer under a wide range of Reynolds numbers from 50,000 to 200,000 at a cascade exit Mach number of 0.6 under steady as well as periodically unsteady inflow conditions. High-frequency blowing at sufficient amplitudes is achieved with the use of fluidic oscillators. The integral loss coefficient calculated from wake traverses is used to assess the optimum pressure ratio driving the fluidic oscillators. The results show that pulsed blowing with fluidic oscillators can significantly reduce the profile losses of the highly loaded LPT blade T161 with a moderate amount of air used in a wide range of Reynolds numbers under both steady and unsteady inflow conditions.

Continuous Closed-Loop Transonic Linear Cascade for Aerothermal Performance Studies in Microturbomachinery

“…The schematic layout of the closed test facility and its components are presented in Fig. 1, comprising of the two-stage oil $3.5 0.9-1.12 University of German Armed Forces, Munich, Germany [8] 0.7-11 0.2-1.05 University of North Dakota, Grand Forks, ND [9] 0.5-10 0.5-0.9 University of Oxford, Oxford, UK [10] 8-30 0-1.6 Virginia Tech, Blacksburg, VA [11] 6-11 0.55-1.05 Von Karman Institute (VKI), Rhode-Saint-Genèse, Belgium [12] 5-34 0.3-1.25 Transactions of the ASME free screw compressor, small 6 m 3 pressure equalization tank to damp out transients, electric 350 kW heater, test section, pressure drop valves, large 24 m 3 dump tank, and aftercooler, which reduces the compressor inlet temperature to 300 K. Considering the aerodynamic similarity parameters, the volumetric flow rate (and therefore M) is predominantly set by the compressor rotational speed, whereas the total mass in the isolated system defines the Reynolds number. The air retained in the cycle is coarsely adjusted during start-up by a blow-off valve, and finetuned during operation.…”

“…2. The subsections include an inlet (1), flow straightener and turbulence grid (2), controllable main frame frontboards (3), bladed test section (4), optical access window (5), rotating disks (6), controllable main frame tailboards (7), and an outlet (8). The modules are designed to interface with other components with sufficient tolerance Oð10 À5 mÞ to not hinder operability, while preventing undesired movement between subsections.…”

“…Addressing these issues, there are a limited number of continuous transonic turbine research rigs, capable of operating in various Reynolds conditions. Regardless of operational principle, a noninclusive list of existing transonic linear cascade facilities in academic institutions is provided in Table 1 [1][2][3][4][5][6][7][8][9][10][11][12]. The only heated test rigs among them are in Ecole Polytechnique Federal de Lausanne and Virginia Tech [2,11].…”

“…[13] and [11], respectively. Although the operational principles of some existing facilities (located in Munich and North Dakota [8,9]) can partially address this range, the lower Reynolds and the upper Mach boundaries of the operation envelope have not received much attention. However, these are the critical design aerothermal flow conditions relevant to the microturbomachinery community.…”

High Frequency Boundary Layer Actuation by Fluidic Oscillators at High Speed Test Conditions

“…Modern LPTs are aerodynamically highly loaded, usually featuring flow separation on the suction side towards low Reynolds number operating points. Since the high speed investigations at ISA showed many promising results [2,9,13,14] for AFC applied on the T161, this paper focuses on a T161-like suction side flow of a flat plate with pressure gradient. The massive flow separation is controlled with high frequency periodic excitation [15], induced by a newly developed coupled fluidic oscillator [16].…”