Full Coverage Discrete Hole Film Cooling: The Influence of Hole Size

Abstract

The influence of hole size and hence blowing rate on full coverage discrete hole wall cooling for gas turbine combustion chamber applications was investigated. Two temperature conditions were used, firstly a 750K gas temperature and 300K coolant, and secondly a realistic combustor primary zone condition of 2100K flame temperature and 700K coolant. It was shown that a large hole size resulted in a significant improvement in the overall cooling effectiveness due to a reduced film heat transfer coefficient. At high temperature the cooling effectiveness was reduced due to radiative heat transfer from the flame gases. At low coolant flow large temperature increases of the coolant occurred within the wall and approached the transpiration situation.

Full Coverage Discrete Hole Film Cooling: The Influence of the Number of Holes and Pressure Loss

“…These practical temperatures could be studied directly on the test facility with an inline kerosene fired preheater to generate the combustion temperature and electrical preheating of the coolant. Andrews et al (1985aAndrews et al ( , 1985b have shown that cooling effectiveness data can be determined on the present facility at these practical conditions. However, there were problems in attaining a uniform temperature at the test section.…”

“…Thus, the optimum design of effusion cooling at low coolant flow rates must also maximize both the film and internal wall cooling components of the overall heat transfer. Andrews et al (1985aAndrews et al ( , 1985b have demonstrated the importance of film and internal wall cooling for a limited range of full coverage effusion cooling geometries. The heat transfer due to the passage of the coolant through the wall has been evaluated in an extensive series of investigations by Andrews et al (1986bAndrews et al ( , 1987Andrews et al ( , 1989.…”

“…In these situations the full combustor wall pressure loss must occur across a single wall and effusion designs for this application were investigated. Andrews et al (1985b) have shown the importance of the hole size or pressure loss and the influence of the number of holes was also investigated for a low pressure loss or large hole size. These results were applicable to impingement/effusion cooling designs where the main pressure loss is at the impingement wall.…”

High Resolution Experimental and Computational Methods for Modelling Multiple Row Effusion Cooling Performance

“…This is often described by small non-dimensional hole pitch (S/D). This increased hole density with reduced diameter has been shown to provide significant increases in effectiveness (see [4][5][6]); this is a result of both a reduction in blowing ratio (and consequently, jet lift-off), allowing the formation of a near continuous film, along with an increased combined convective effect within each of the cooling holes. Foster and Lampard [7] demonstrated the rise in effectiveness with smaller spanwise hole pitching and also observed a decrease in jet lift-off.…”

High Resolution Experimental and Computational Methods for Modelling Multiple Row Effusion Cooling Performance

“…This is often described by small non-dimensional hole pitch (S/D). This increased hole density with reduced diameter has been shown to provide significant increases in effectiveness (see Andrews et al (1985), Gustafsson & Johansson (2001) and Crawford et al (1980)); this is a result of both a reduction in blowing ratio (and consequently jet lift-off) allowing the formation of a near continuous film, along with an increased convective effect within each of the cooling holes. Foster and Lampard (1980) demonstrated the rise in effectiveness with smaller spanwise hole pitching and also observed a decrease in jet lift-off.…”