| With the increasing use of gas turbines in various fields,such as aviation systems,power generation systems and ship power systems,improving the performance of gas turbines has become an urgent problem at this stage.Based on the principle of Brayton cycle,increasing the pressure ratio and the exit temperature of the combustion chamber are beneficial to increase the thrust-to-weight ratio.As the thrust-to-weight ratio increases,the design of the combustion chamber components will inevitably develop toward high temperature rise and high heat capacity.The increase in combustion chamber temperature will increase the amount of air involved in combustion,reduce the amount of air used for cooling,increase the temperature of the cold air and the wall temperature of the combustion chamber is much higher than the withstand temperature of the metal.Therefore,in order to ensure the components of the combustion chamber can operate at so high temperature without significant deterioration,developing highly-efficient cooling schemes,such as full-coverage film cooling,double-wall cooling and Lamilloy cooling,is one of the key technological routines.Experimental tests are conducted for the two arrangement modes of Lamilloy cooling configuration.The influence of the blow ratio on the overall cooling effectiveness of the laminate porous plate is obtained.And the validation of numerical method is also confirmed.The results show that within the scopes of this experimental study,the temperature of the hot-side wall is reduced as the blowing ratio increases.Under low blowing ratios,the increase of the blowing ratio shows an obvious influence on the overall cooling effectiveness.When the blowing ratios are larger than 1.5,the overall cooling effectiveness changes weakly with the increase of the blowing ratio.A series of numerical simulations are performed to investigate the effects of geometric parameters on cooling performance of a laminate porous plate,under a given coolant massflow rate per unit wall-surface area and the combustor linear representative conditions.The relationship between impinging-hole number,pin-fin number and film-hole number is 1:10:1.Among the current ranges of geometric parameters,it is found that the film-hole diameter and impinging-hole diameter have relatively stronger influence on overall cooling effectiveness and pressure drop across the laminate porous plate.Increasing film-hole diameter is helpful for improving overall cooling effectiveness and reducing pressure drop.Increasing film-hole diameter results a reduction of pressure drop and overall cooling effectiveness.The variation of pin-fin diameter or impinging distance has nearly no influence on the pressure drop.The increase of pin-fin diameter results in a little increase of overall cooling effectiveness.The effect of dimensionless impinging distances on the overall cooling effectiveness is determined by coolant massflow rate per unit wall-surface area.Increasing the streamwise spacing or reducing the spanwise spacing can improve the overall cooling effectiveness,increase the hole spacing will increase the relative pressure loss.The change of the shapes of the pin-fin has influence on the overall cooling effectiveness and flow coefficient.In the impingement-effusion double-wall cooling structure,the cylindrical pin-fin is more reasonable.The overall cooling effectiveness increases with the increase of the coolant massflow rate per unit wall-surface area and the decrease of the mainstream flow rate. |
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