Search

Purpose Effusion cooling represents one the most innovative techniques for the thermal management of aero-engine combustors liners. The huge amount of micro-perforations implies a significant computational cost if cooling holes are included in computational fluid dynamics (CFD) simulations; therefore, many efforts are reported in literature to develop lower-order approaches aiming at limiting the number of mesh elements. This paper aims to report a numerical investigation for validating two approaches for modelling film cooling, distinguished according to the way coolant is injected (i.e. through either point or distributed mass sources).Design/methodology/approach The approaches are validated against experimental data in terms of adiabatic effectiveness and heat transfer coefficient distributions obtained for effusion cooled flat plates. Additional reynolds-averaged naver stokes (RANS) simulations were performed meshing also the perforation, so as to distinguish the contribution of injection modelling with respect to intrinsic limitations of turbulence model modelling.Findings Despite the simplified strategies for coolant injection, this work clearly shows the feasibility of obtaining a sufficiently accurate reproduction of coolant protection in conjunction with a significant saving in terms of computational cost.Practical/implications The proposed methodologies allow to take into account the presence of film cooling in simulations of devices characterized by a huge number of holes.Originality/value This activity represents the first thorough and quantitative comparison between two approaches for film cooling modelling, highlighting the advantages involved in their application. [ABSTRACT FROM AUTHOR]

The estimation of the discharge coefficient is of paramount importance in gas turbine design as this parameter affects the actual mass flow rate through secondary air and cooling systems. The lack of confidence in the estimation of its value may entail a reduction in the engine performance as well as lifespan. The scope of this work is therefore still an object of study in the scientific community, mostly due to the complexity and the variety of phenomena involved. In an effort to provide a general characterization of the aerodynamic losses across round orifices, an extended numerical campaign was carried out to develop a correlation for the discharge coefficient. The investigation was focused on round, inclined holes at isothermal conditions, with limited crossflow on both mainstream and coolant sides. Exploiting CFD simulations validated against a literature test case, a Design of Experiments (DoE) was performed to assess the influence of length-to-diameter ratio ( L / d ), inclination angle with respect to the crossflow direction ( α ) and pressure ratio ( β ). The large amount of data obtained were then correlated in order to provide an expression capable of predicting the discharge coefficient. The correlation is valid for round holes ( α = 20 ∘ − 90 ∘ , L / d = 1 − 10 , β = 1.01 − 2.0 ) with low crossflow on both mainstream and coolant sides ( M a m = M a c = 0.02 ). allowing to reproduce the CFD data set with a mean absolute error of 3.44% and a standard deviation of 1.81%. [ABSTRACT FROM AUTHOR]