Numerical Simulation of Swirling Impinging Jet Issuing from a Threaded Hole under Inclined Condition

Abstract

There are some inclined jet holes in the cooling structure of the leading edge region of gas turbine blades. In order to improve the cooling effect of traditional round holes, this paper proposes to replace the round holes with threaded holes, and studies the complex flow and heat transfer performance of the swirling impinging jet (SIJ) issuing from the 45° threaded holes in the inclined condition by numerical simulation. The influencing factors include jet inclination angle α (45°–90°), jet-to-plate distance (H/d = 2, 4, 6), and Reynolds number (6000–24,000). The results show that the inclination angle and jet-to-plate distance have a great influence on the size, shape, and position of vortices in the jet space, while the Reynolds number has little effect on the vortices. In the inclined state, the impinging cooling effect of the swirling impinging jet is better than that of the circular impinging jet (CIJ), both heat transfer coefficients will degrade significantly when the inclination angle is 45°. When the inclination angle is greater than 45°, compared with the round hole, the enhanced heat transfer region for the swirling jet is in the region of r/d < 3, while both of the Nusselt numbers in the wall jet region are weak, with a value of just 20. At the same time, with the increasing of the inclination angle (α > 45°), the average Nusselt number on target surface holds a constant value. Under the inclined conditions, the heat transfer coefficient on the target surface for the swirling jet is increased totally with the increasing of the Re, but when the Re is larger than 18,000, the rate of enhanced heat transfer gradually weakens.

Heat Transfer Augmentation through Different Jet Impingement Techniques: A State-of-the-Art Review

“…In this regard, Xu et al [90] performed a numerical study to analyze the effect of swirling jets achieved through threaded holes on the heat transfer performance of gas turbine blades. They used 45 • threaded holes instead of circular holes to study the impact of swirling jet impingement on heat transfer.…”

Flow and Heat Transfer Characteristics of a Swirling Impinging Jet Issuing from a Threaded Nozzle of 45 Degrees

“…According to our previous work [32,33], the RNG k − ε model is more suitable for simulating swirling impinging jets, and it provides better stability and higher computational efficiency. Therefore, it is applied in this work.…”

“…Therefore, choosing a new nozzle to achieve perfect cooling effectiveness is a talking point. Our research group designed a new type of nozzle with the superposition of the vertical jet and swirl [32,33]. Earlier research results revealed that the cooling effectiveness and uniformity can be increased by equipping spiral grooves.…”

Large-Eddy Simulation Study of Flow and Heat Transfer in Swirling and Non-Swirling Impinging Jets on a Semi-Cylinder Concave Target

“…Compared with the traditional round hole jet, the heat transfer of the swirling jet was enhanced at S = 0.4; the intensity of heat transfer was weakened at a large swirling number, i.e., S = 0.78 and S = 0.94. Our research group [13,14] recently reported a threaded nozzle, which generated swirling flow and enhanced heat transfer performance of impinging jets under the vertical and inclined conditions compared with the conventional round hole. Our proposed nozzle consisted of a smooth circular hole and four circumferential screw grooves for structuring the impinging jet flow with a superimposed swirl, so that the nozzle was similar to the conventional circular hole with internal threads.…”