Effect of film-hole configuration on film-cooling effectiveness of squealer tips

Abstract

Three-dimensional numerical simulations are carried out to investigate the effects of film-hole arrangement and blowing ratio on the squealer tip leakage flow field and tip film-cooling performance. Six film-hole arrangements with 13 holes are designed in the current study for comparison. In type-A and type-B, the film-cooling holes are arranged in a single row, located at the middle camber line or close to the suction-side squealer. The four modified film-hole arrangements are realized by placing two rows of total 7 film-cooling holes at the leading edge (type-C, type-D, type-E and type-F) and remaining the rest film-cooling holes in a row at the middle chord zone. The results show that the leakage flow entering the tip gap from the leading edge of suction side, the leading edge of pressure side and the middle chord and trailing edge of pressure side behaves different flow feature inside the tip cavity, inducing complicated swirling flow filed. The modified film-hole arrangements yield more reasonable film coverage on the tip surface by comparing with the single row film-hole arrangement under relatively high blowing ratios. In addition, the modified film-hole arrangements also show different rules on the film-cooling effectiveness distributions over some specific surfaces, such as tip cavity bottom surface and squealer top surface, as well as PS squealer inner surface and SS squealer inner surface. Among the presented four modified film-hole arrangements, type-D and type-F gain the most favorable film-cooling improvement.

Effect of Cutbacks on Tip Leakage Flow and Film-Cooling Effectiveness of a Turbine Blade Tip under Relative Moving Condition

“…For the second type, seven film holes are located in the vicinity of the leading-edge and the remaining six film holes are arranged near the suction-side squealer in the mid-chord region (referred to as LE mode). In previous studies, 20,21) we demonstrated the superiority of the LE mode for improving the film-cooling effect on the squealer tip. In this paper, we continue to explore the effect of trailing-edge cutbacks while considering the relative motion between the blade tip and the casing.…”

Effects of casing motion on tip leakage flow and film-cooling effectiveness of squealer tips

“…It is proposed according to pre-simulate of the tip leakage flow field of squealer tip without film-cooling under the condition of stationary casing. And our study (Cheng et al 2017) has described the structural parameter of type-C in detail. Figure 4 presents the definition of the separation line.…”

“…Table 2 is the summation of the structural parameter of the film-hole arrangements. Cheng, Chang, Jingyang Zhang and Jingzhou Zhang, Journal of Thermal Science and Technology, Vol.12, No.2 (2017) Fig.4 Limiting lines on the squealer tip (Cheng et al, 2017). …”

“…Figure 7 shows the tip leakage flow field on the uncooled squealer tip with a squealer height of H=1.7mm (4.1%span) for (a) stationary casing and (b) moving casing. According to the study of Cheng et al (2017), the film-cooling characteristic on the squealer tip is closely related to the leakage flow in the cavity, which is formed by the leakage flow entering the tip clearance from the leading edge of SS (red streamlines) and leading edge of PS (blue streamlines). In order to show the effect of the rotation more clearly, the leakage characteristic within the cavity is analyzed in detail.…”

Aerothermal Investigation of Transonic Over-Tip Leakage Flow with Cooling Injection for Different Tip Geometries

“…Furthermore, Ameri and Bunker (1999) implemented a computational study to investigate the detailed heat transfer characteristics on the blade tip surfaces for a high-power turbine, and the numerical results were compared with the experimental data of Bunker et al (1999). Cheng et al (2017) studied the effects of film hole location on squealer tip leakage flow, film cooling effectiveness, and surface heat transfer coefficient. The effect of trailing edge cutback on squealer tips was numerically investigated by .…”