Investigations of film cooling and its nonuniform distribution for the conjugate heat transfer passage with a compound inclined angle jet

ABSTRACT

Film cooling effectiveness and its distribution characteristics on the gas turbine blade surface were investigated numerically. Seven rectangular ribs were located on the internal wall, and a film cooling hole had a compound inclined angle. The case with a compound angle of 45° was designed to improve the lateral film cooling effectiveness on the downstream surface. The secondary flow jet from the internal channel was affected by the flow velocity ratios, and an investigation of the external film cooling was considered for various values of thermal conductivity and heat conduction. Two different plate materials were used to analyze the effect of plate thermal conductivity. The results showed that the compound angle of 45° causes an asymmetric distribution of the film cooling effectiveness. However, the bending effect can be of advantage to increase the film cooling effectiveness in the horizontal direction, so a better distribution of the lateral film cooling effectiveness can be achieved. The area-average cooling effectiveness is improved by an increase of the flow rate at the internal passage inlet. A new definition of D_n is introduced to evaluate the nonuniformity of the distribution of the local film cooling effectiveness quantitatively and conveniently. The downstream cooling effectiveness distribution becomes more uniform using a compound angle of 45°. For the high thermal conductivity case, higher blade-wall heat flux is transferred by heat conduction, which drops the area-average wall temperature along the secondary flow direction.