A new design of vane-shaped hole pre-swirl nozzle

Abstract

Theoretical analysis shows that the temperature drop of a pre-swirl system directly relates to the pre-swirl effectiveness of the pre-swirl nozzle. Besides, increasing the discharge coefficient and reducing the actual flow angle are the main ways to increase the pre-swirl effectiveness. A new design of pre-swirl nozzle called vane-shaped hole nozzle was introduced and analyzed in this paper. By keeping the throat area, the radial location and the pre-swirl angle (15°), numerical comparisons were carried out between the vane-shaped hole nozzle and other three typical nozzles, widely used in industry: simple drilled nozzle, aerodynamic nozzle and cascade vane nozzle. In order to involve the mixing and rotating effects in the pre-swirl cavity downstream of the nozzles, the rotating pre-swirl cavity and receiver hole were included in the computational models. Numerical results show that aerodynamic nozzle could alleviate the rapid acceleration and deflection at nozzle inlet, which results in 13.7% higher discharge coefficient than the simple drilled nozzle. The discharge coefficient of the cascade vane nozzle can be as high as 0.97 due to the aerodynamical design; however, the pre-swirl effectiveness is only 0.86 because of a large deviation angle (2.4°). For the vane-shaped hole nozzle, the vane height/pitch ratio could be flexibly adjusted to an appropriate value, which makes its performance better than that of the traditional ones. Higher vane height/pitch ratio and close to zero trailing edge radius lead to a small deviation angle (0.56°). Consequently, the pre-swirl effectiveness of the vane-shaped hole nozzle is about 8% higher than that of the cascade vane nozzle, though the discharge coefficient is about 5% lower. Additionally, the volume of the solid block in the vane-shaped hole nozzle is larger than that in the cascade vane nozzle, which could reduce the difficulty in manufacturing but increase the total weight.