The Thermodynamics of Wake Blade Interaction in Axial Flow Turbines: Combined Experimental and Computational Study

Abstract

This paper reports on insights into the detailed thermodynamics of axial turbine nozzle guide vane (NGV) wakes as they interact with the rotor blades. The evidence presented is both computational and experimental. Unsteady Reynolds-averaged Navier–Stokes (RANS) simulations are used to compare the experimental observations with theoretical predictions. Output processing with both Eulerian and Lagrangian approaches is used to track the property variation of the fluid particles. The wake is found to be hot and loses heat to the surrounding fluid. The Lagrangian output processing shows that the entropy of the wake will fall due to heat loss as it passes through the rotor and this is corroborated experimentally. The experimental vehicle is a 1.5-stage shroudless turbine with modest Mach numbers of 0.5 and high response instrumentation. The entropy reduction of the wake is determined to be about four times the average entropy rise of the whole flow across the rotor. The results show that the work done by the wake fluid on the rotor is approximately 24% lower than that of the free-stream. The apparent experimental efficiency of the wake fluid is 114% but the overall efficiency of the turbine at midheight is around 95%. It is concluded that intrafluid heat transfer has a strong impact on the loss distribution even in a nominally adiabatic turbine with moderate row exit Mach numbers of 0.5.

Aero-thermodynamic and chemical process interactions in an axial high-pressure turbine of aircraft engines

“…Generally, the flow parameters in both cases evolved very closely. Their baselines are similar and in good agreement with flow-parameter evolution evidenced in past studies and experiments reported on by Marchal and Sieverding, 47 Strickland et al, 44 Langston, 48 Sonoda, 50 Goldstein and Spores, 45 Sieverding et al, 46 Sieverding, 49 and Rose et al 22,23 The flow vortex in both cases began at stator blade's LE and developed along the blade profile. The vortex was strong in the rotor where rotation impacts occur, as explained in detail in section ''Baseline 1D; 2D full HPT flow-path calculation.''…”

“…The potential field of the moving rotor causes finites (∂T=∂x, ∂p=∂x, and ∂U=∂x), which, according to equations (1)-(3) cause the total temperature, pressure, and velocity to vary. 22,23,43 The flow variation results in Figure 4 are in good agreement with the experimental results of Strickland et al, 44 Goldstein and Spores, 45 Sieverding et al, 46 and Rose et al 22,23 To better understand the mechanism forming the vortex from blade LEs to blade TEs, Goldstein and Spores 45 combined various visualizations and measurements described in the literature (see, among others, Marchal and Sieverding, 47 Langston, 48 Sieverding, 49 and Sonoda 50 ). This mechanism is illustrated in Figure 5, which shows the major vortices, labeled 1-7, and primary regions of interest, labeled A-K, in the turbine passage.…”

“…In order to achieve these goals, we set up the following: (a) the HPT of a gas turbine was designed using the BLADE GEN module (ANSYS), 19 (b) STAR-CCM + (CD-ADAPCO) 20 software was used to simulate the aero-thermodynamic and chemical processes, and (c) the results were executed and analyzed with an in-house MATLAB routine and compared with that reported in the literatures. [6][7][8][9]12,[21][22][23][24]…”

Importance of the vane exit Mach number on the axial clearance-related losses

“…Although the unsteady stator-rotor interaction is an important contributor to the overall turbine performance, it is a complex mechanism and it cannot be said whether the weaker interaction is always more beneficial or whether the stronger interaction should be the aim, as proposed by Rose et al 23 The positivity or negativity of the stator-rotor interaction can also vary from hub to shroud, as shown by Yamada et al 24 and Gaetani et al 2,18 In addition, Gaetani et al 25 reported that the wake-induced interaction decreased the efficiency with larger clearances and the vortex-induced interaction with small clearances.…”

Computational Study of the Impact of Unsteadiness on the Aerodynamic Performance of a Variable-Speed Power Turbine

“…Thirdly, the unsteady computations simulate spatiotemporal loss production associated with wake transport and stretching (Ref. 15) to some degree of accuracy (grid dependent). Lastly, Haselbach et al (Ref.…”