Computational Study of Reynolds Number Impact on Characteristics of a Spatial Air Intake Mounted on the Fuselage Imitator

Aeronautical and Space-Rocket Engineering


Аuthors

Novogorodtsev E. V.*, Koltok N. G.**

Central Aerohydrodynamic Institute named after N.E. Zhukovsky (TsAGI), 1, Zhukovsky str., Zhukovsky, Moscow Region, 140180, Russia

*e-mail: novogorodtseve91@mail.ru
**e-mail: nikitakoltok@gmail.com

Abstract

The presented article focuses on the study of the Reynolds (Re) number impact on the characteristics of a supersonic air intake under condition of the boundary-layer growth prior to the inlet of the air intake. The authors studied a flat fixed-geometry supersonic air intake of external compression with oval inlet. The air intake is equipped with a boundary layer control system presented by perforation. The air intake was mounted on a pylon on the wedge, which imitates the fuselage surface of the hypothetical aircraft. The distance from the edge of the wedge to the air intake inlet plane was l = 5L, where L is the length of the air intake duct. As is known, the boundary layer thickness on a solid surface can be estimated as δ ~0.01l, where l is the distance along the surface upstream. Thus, the height of the pylon, on which the air intake is mounted is 1% of the distance from the edge of the wedge to the air intake inlet plane, or h = 0.05L, where L is the length of the air intake duct.
The RANS-SST approach with unstructured computational grid application was employed to conduct the air intake flow-around numerical simulation. The total pressure recovery coefficient prior to the engine v and circumferential non-uniformity parameter of the total pressure field prior to the engine (Δσ_о ) ̅ are presented as the air intake characteristics being studied. The value of the Re number was being computed in this study by changing the values of static pressure and static temperature of the airflow prior to the air intake. Thus, the air intake characteristics were being studied at the Re values from 0.4 × 107 to 4.2 × 107. The air intake throttle characteristics and flow patterns in the air intake channel at the studied flow-around modes were obtained by the results of the flow-around numerical modeling.
Comparative analysis of the obtained characteristics of the air intake mounted on the fuselage imitator at the studied Re numbers revealed that with the Re number decrease, the air intake characteristics decrease as well. Thus, with Re ~0.4 х 107 the υ coefficient values were obtained lower than those with the Re ~ 0.4 х 107 by the value of the Δυ ≈ 0.005 order. The air intake characteristics degradation is stipulated by the intensity increase of the boundary layer growth prior to the air intake inlet and in its channel with the Re number decrease.
Characteristics comparison of the air intake, mounted on the fuselage imitator, with characteristics of the isolated air intake at the Re ~0.7 х 107 was performed within the framework of this work. Comparative analysis confirmed the positive effect of flow total pressure losses reduction revealed in the isolated air intake in the λ-shaped structure, occurring while the control system perforation flow-around by the boundary layer. The authors revealed that the air intake mounting on the fuselage imitator leads to the characteristics degradation compared to the isolated air intake. Thus, the value of the υ coefficient in the air intake mounted of the fuselage imitator was obtained lower at the average of Δν ≈ 0.005–0.01 than in the isolated air intake. The authors revealed the two basic factors affecting the air intake characteristics degradation. Firstly, with the set pylon height, a portion of the low-energy air enters the air intake inlet. Secondly, the air intake characteristics degradation is stipulated by the effectiveness decrease of the boundary layer control system. It was found that the air volume being removed from the air intake channel through the perforation of the boundary layer control system  decreased by the value of the 28% order while the air intake mounting on the fuselage surface imitator.

Keywords:

numerical air inlet flow simulation, Reynolds number, 3D fixed-geometry air inlet, air inlet boundary-layer control system, total pressure recovery coefficient, throttle characteristic of the air inlet, parameter of circumferential flow distortion

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