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RISS 인기검색어
- 검색키워드
- 저자 : Mrinal Kaushik (검색결과 3 건)
- 무료
- 기관 내 무료
- 유료
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Mrinal Kaushik 한국항공우주학회 2019 International Journal of Aeronautical and Space Sc Vol.20 No.3
To have an efficient combustion, the aircraft engine intakes operating at supersonic and hypersonic speeds necessarily decelerate the flow to subsonic level before entering the combustor, which is achieved by a combination of oblique and normal shock waves in the intake-isolator, and thus the high-speed intakes are called the mixed-compression intakes. The advantages of shock-enabled compression, however, does not come standalone rather associated with colossal losses due to shock and boundary layer interactions (SBLIs). The repercussions in the flow due to these interactions may include; intake unstart, abrupt thickening, separation of the boundary layer, unsteady shock oscillations, etc. Therefore, the SBLIs must be controlled to minimize the losses. Control of these interactions by manipulating the boundary layer using micro-vortex generators (MVGs) has gained prominence. In this study, a new ramped-vane MVG configuration, deployed near the shock impact point in the Mach 2.2 mixed-compression intake at varied contraction ratios, has been experimentally investigated. Plain intake and the intake controlled with conventional MVGs are also investigated for comparison. The heights of all the MVGs were varied as; 600 μm, 400 μm and 200 μm. The ramped-vane MVGs of height 200 μm are found to be the most efficient in causing a favorable pressure drop at the locations; near-upstream (x = 0.48 L) and near-downstream (x = 0.7 L) of the MVGs. The maximum reductions in static pressures about 11% at the intake contraction ratio of 1.20 at x = 0.48 L, and about 24% at the contraction ratio of 1.23 at x = 0.7 L, are achieved. The Schlieren pictures clearly demonstrate the effectiveness of all the tested ramped-vane MVGs (particularly 200 μm MVGs) in weakening the waves and reducing the separation length.
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Performance of corrugated actuator-tabs of aspect ratio 2.0 on supersonic jet mixing enhancement
Tamal Jana,Mrinal Kaushik 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.3
The present experimental investigation explores the ability of the corrugated actuator-tabs (or simply, the corrugated actuators) of aspect ratio 2 in encouraging the mixing of Mach 1.73 circular jet at different levels of expansion conditions. Essentially, rectangular, triangular, and semi-circular corrugated actuators are deployed at the opposite positions across the diameter of the nozzle outlet and compared with the plain or simple actuators located at the same positions. Quantitative and qualitative observations were conducted by pitot pressure measurements and shadowgraph flow visualization. Interestingly, the characteristic decays are higher for the semi-circular and triangular corrugated actuators, exhibiting superior mixing than the rectangular corrugated actuator in the far-field. However, the core length reduction for rectangular corrugation is greater than for triangular and semicircular corrugation geometry. As high as 96.5 % core length reduction was obtained for the rectangular corrugated actuators operating at the overexpansion condition. The pressure profiles along and perpendicular to these actuators confirmed that the deployment of the corrugation geometry significantly reduces the flow asymmetry. The shadowgraphic flow visualizations reveal that the plain and corrugated actuators weaken the waves and shorten the cells when compared to the uncontrolled or free jet.
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Jana Tamal,Thillaikumar T.,Kaushik Mrinal 한국항공우주학회 2020 International Journal of Aeronautical and Space Sc Vol.21 No.4
The supersonic/hypersonic flow through an aircraft intake must be decelerated before entering the combustion chamber to ensure efficient combustion. Retardation in the flow speed is achieved through a progression of oblique and normal shock waves in the isolator region of the intake. However, the advantages of speed reduction in intake are usually accompanied by huge losses due to the shock wave and boundary-layer interactions (SBLIs). These losses may include, inlet-unstart, abrupt thickening or separation of the boundary layer, unsteady shock oscillations, etc. Clearly, the SBLIs must be controlled to minimize the losses and improve the performance of the complete vehicle. Control of these interactions by manipulating the strength of the shock using a shallow cavity with wall ventilation has gained prominence. In this study, the efficacy of a thin porous surface deployed over shallow cavity in the higher adverse pressure gradient regions of Mach 5.7 and Mach 7.9 mixed-compression intakes, is experimentally investigated. With the variation of diameter and pitch of the pores, the porosity in Mach 5.7 intake is varied as; 4.5%, 7.5%, 17%, 21.6%, and 25%. A maximum of 20.53% drop in static pressure in the Mach 5.7 intake controlled by the cavity covered with 25% surface perforation, at a near-reattachment location (x/L = 0.73), is observed. However, the separation bubble in Mach 5.7 intake is suppressed most efficiently, when the cavity is covered with 17% porous surface. For Mach 7.9 intake also, the 25% surface perforation has maintained its superiority in reducing the wall static pressure to a maximum of 20.20% at x/L = 0.73. Once again, the 17% porous surface controlled configuration is found to be quite effective in suppressing the bubble. A qualitative investigation of the Schlieren images supports the findings of wall static pressure data.
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