Adiabatic and Overall Effectiveness Measurements of an Effusion Cooling Array for Turbine Endwall Application

Abstract

An experimental analysis for the evaluation of adiabatic and overall effectiveness of an effusion cooling geometry is presented in this paper. Chosen configuration is a flat plate with 98 holes, with a feasible arrangement for a turbine endwall. Fifteen staggered rows with equal spanwise and streamwise pitches (Sx/D=Sy/D=8.0), a length to diameter ratio of 42.9 and an injection angle of 30 deg are investigated. Measurements have been done on two different test samples made both of plastic material and stainless steel. Adiabatic tests were carried out in order to obtain adiabatic effectiveness bidimensional maps. Even if a very low conductivity material polyvinyl chloride was used, adiabatic tests on a typical effusion geometry suffer, undoubtedly, from conductive phenomena: a full three-dimensional finite element method postprocessing procedure for gathered experimental data was therefore developed for reckoning thermal fluxes across the surface and then correctly obtaining adiabatic effectiveness distributions. The objective of the tests performed on the conductive plate, having the same flow parameters as the adiabatic ones, was the estimation of overall efficiency of the cooled region. Experimental measurements were carried out imposing two different crossflow Mach numbers, 0.15 and 0.40, and varying blowing ratio from 0.5 to 1.7; effectiveness of the cooled surface was evaluated with a steady-state technique, using thermochromic liquid crystal wide band formulation. Results show that the postprocessing procedure correctly succeeded in deducting undesired thermal fluxes across the plate in adiabatic effectiveness evaluation. The increasing blowing ratio effect leads to lower adiabatic effectiveness mean values, while it makes overall effectiveness to grow. Finally, Reynolds-averaged Navier–Stokes steady-state calculations were performed employing an open source computational fluid dynamics code: an adiabatic case has been simulated using both a standard and an anisotropic turbulence model. Numerical achievements have then been compared with experimental measurements.

Effects of Effusion Cooling Pattern Near the Dilution Hole for a Double-Walled Combustor Liner—Part 1: Overall Effectiveness Measurements

“…Because there was no coolant attached to the surface, the improved cooling effectiveness for the outward and inward cases compared to the closed case must have come from in-hole convection. Similar to the current study, Facchini et al [2] found that when there were conduction effects, effusion holes acted as a heat sink due to the in-hole convection, especially at higher blowing ratios.…”

“…In addition, they found that the momentum flux ratio for the effusion jets did not have any impact on the effectiveness for the first three rows of holes. In a different study with only effusion cooling, Facchini et al [2] found that increasing the effusion blowing ratio generally led to decreased adiabatic effectiveness due to jet separation; however, overall effectiveness increased at high blowing ratios due to in-hole convection. Martin and Thorpe [3] studied the effects of freestream turbulence intensity on effusion cooling without dilution jets and found that at low blowing ratios of the effusion jets (M eff,in < 0.5), high freestream turbulence resulted in decreased adiabatic effectiveness; whereas at relatively high blowing ratios, up to M eff,in ¼ 1.4, high freestream turbulence caused an increase in adiabatic effectiveness.…”

Analysis of the Thermomechanical Stresses in Double-Wall Effusion Cooled Systems

“…4.4. The thermal analysis of such a system can be performed using different methods, e.g., full CFD analysis of the cooling air and the mainstream [3,4], a decoupled conjugate approach (using CFD for the internal cooling and empirical correlation to model the mainstream) [2], or using suitable empirical correlations [5,6]. The outcome of the thermal analysis, using these methods, is the temperature and heat transfer coefficients on the external surface of the outer skin and the internal walls for a given Reynolds number at the impingement holes and mainstream temperature and velocity.…”

“…( 16) and (18), i.e., Tf f f , and the heat flux to the inner wall is taken to be zero. Several analyses were then performed for different values of the wavelength in the range λ f /L ∈ 10 −1 -10 1 and H/t ∈ [3][4][5][6][7][8][9][10].…”

Study of an effusion-cooled plate with high level of upstream fluctuation

“…Experiments to determine adiabatic coolant-film effectiveness (ACE) generally involve measuring spatially resolved surface temperature distributions using techniques such as thermochromic liquid crystal [1,2] and infra-red (IR) Thermography [3,4]. The measurement surface is usually manufactured from a material with an extremely low thermal conductivity in order to satisfy the adiabatic condition.…”