Impingement Cooling for Modern Combustors: Experimental Analysis and Preliminary Design

Abstract

The aim to reach very low emission limits has recently changed several aspects of combustor fluid dynamics. Among them, combustor cooling experienced significant design efforts to obtain good performances with unfavorable conditions. This paper deals with experimental research and 1D numerical simulations of impingement cooling from multiple jet arrays, performed in the first two years of the European research project LOPOCOTEP. Geometries are derived from typical LPP combustor cooling configurations, i.e. small and sparse holes, due to low coolant mass flow rate and high pressure losses (compared to typical blade cooling parameters). Tests are performed with both transient and steady-state technique, using TLC (Thermochromic Liquid Crystal) wide-band formulations. Results are obtained in terms of local distributions of heat transfer coefficient and effectiveness. Average values are compared with calculations to validate numerical code and derive useful indications on effectiveness variation for different blowing rate. It is accordingly found that literature results almost match the measurements. It is also shown that measured row-by-row effectiveness values can be usefully employed in a preliminary design stage. Data concerning holes discharge coefficients are also presented.

Impact of Swirl Flow on the Cooling Performance of an Effusion Cooled Combustor Liner

“…Investigations of circular and elliptical shaped effusion cooling arrays for combustor liner application are presented by Facchini et al [10,11]. In either cooling array increasing Reynolds numbers lead to a lesser dependency of cooling performance on blowing ratio and to slightly better cooling performance.…”

A 3D Coupled Approach for the Thermal Design of Aero-Engine Combustor Liners

“…Conceptual illustration of 1D thermal analysisGas side heat loads are evaluated from a given description of the flame conditions in terms of FAR, temperature, velocity and pressure.Moreover, heat sink effect (Q hs ) is accounted for applying, for each row, heat removal given by the calculated heat transfer coefficient and adiabatic wall temperature inside the perforation.After this introduction, some details concerning the coupling among the codes is given here below. The procedure is composed of three main parts: Icons1D (Internal COoling Network Solver), a fluid network solver for heat transfer evaluation on the interfaces between the metal and the coolant, Cowl, that estimates the radiative and convective heat loads on the gas side and radiative heat transfer between the liner and the casing, and the thermal solver, that computes the heat conduction through the metal and finally provides the wall temperature distribution.The analysis of the coolant fluid network is performed using a onedimensional steady code, Icons1D, developed starting from a in-house code (SRBC) used in several works[123,124,125]. The representation of a cooling system consists of a fluid network made up connecting basic components, each one dedicated to model a particular region of the combustor.…”