Chae-Hyoung Kim

A Performance Study of Vent Mixer with Geometric Characteristics in Supersonic Flow

This paper studies the aerodynamic performance that the vent mixer-new conceptual supersonic mixer-showed with its geometric characteristics. The hole is 2 mm with 2 mm`s distance from the wall in case 1 and with no distance in case 2. In case 3 die hole is 1 mm. Case 1 and case 2 showed the same total pressure recovery ratio, of which the case 3 was lower than that. While cases 1-3 had the same reattachment length, the shear layer was thicker in cases 1 and 2 than in case 3. Within the recirculation zone, cases 1 and 2 had lower pressure loss and higher velocity gradient difference than case 3-they enhance mixing between air and fuel. Separation bubble which is developed by the inflow into the recirculation zone has a significant effect on the total pressure recovery ratio in the combustor. Also separation bubble influences pressure distributions and recirculation flows in the recirculation zone. Therefore, inflow rate of air into the recirculation zone mainly affects the performance of vent mixer.

Combustion Characteristics Study using Hyper-mixer in Low-enthalpy Supersonic Flow

ABSTRACT In this study, a forced ignition method with a plasma jet tor ch is studied in Mach 2 laboratory scaled wind-tunnel. The hyper-mixer is used as a mixer. For two normal injection cases, the one is collided against a wedge plate of the hyper-mixer and the other is directly injected into the cold main flow. For the first case, the hyper-mixer disperses the injecte d fuel, leading to the mixing enhancement. Furthermore, the fuel-air mixture is provided into the plasma hot gas, which enhances the combustion performance. However, the direct injection into the main flow method spends amount of fuel without ignition in the cold supersonic flow. In the en d, for the forced combustion, it is important to supply the fuel-air mixture into the heat source.초 록 본 연구에서는 마하 2의 실험실 규모의 풍동장치에서 플라즈마 제트 토치를 점화기로 사용하여 강제점화에 대한 연소 특성을 연구하였다. 하이퍼 혼합기는 혼합기로 사용되었다. 수직분사의 경우, 하나는 하이퍼 혼합기의 웨지면에 충돌하도록 하였으며, 다른 하나는 차가운 주유동으로 바로 분사되도록 하였다 . 하이퍼 혼합기와 충돌하는 경우 충돌된 연료는 분산되며 확산 혼합에 의해 혼합성능이 증대된다 . 또한 혼합된 가스는 대부분 플라즈마 제트의 열원으로 유입되어 연소 성능을 증대시킨다 . 하지만 주유동으로 직접 분사되는 경우는 초음속의 주유동 내에서 점화되지 못하고 많은 양의 연료가 소비된다 . 따라서 강제점화 방식의 연소의 경우에는 많은 양의 연료-공기 혼합물을 점화가 가능한 열원으로 공급하는 것이 중요하다 .Key Words: Hyper Mixer(하이퍼 혼합기), Normal Injection(수직분사), Supersonic Combustion(초음속 연소), Mixing Enhancement(혼합 증대), Forced Ignition(강제 점화)Received 5 June 2013 / Revised 31 October 2013 / Accepted 6 Nov ember 2013

Effect of a Vent Slot Mixer with a Plasma Jet Torch in Unheated Supersonic Flow

Mixing and combustion experiments were conducted in a supersonic wind-tunnel of Mach number 2. In the current work, a new idea for dual-mode scramjet engine was simply introduced, and a new mixer, vent slot mixer, was developed to perform the supersonic combustion. The new idea of flight vehicle is based on forced ignition in cold supersonic inflow condition. Thus, an igniter such as a plasma jet torch was used to ignite fuel-air mixture in the combustor. The vent slot mixer shows high mixing efficiency, which is significantly sensitive to fuel injection locations. The mixing in the recirculation region is enhanced by the interaction between the fuel injectant and inflow air through the vent slot. The plasma jet torch ignites the fuel-air mixture within the plasma jet plume (hot gas zone), and its combustion region is mainly distributed on the lower wall. Thus, the combustion shows good performance when the fuel injectant is distributed around the plasma jet plume on the lower wall. In cold inflow condition, thermal choking in the combustor occurs for low equivalence ratio without a diffuser. Although the thermal choking occurs in the combustor, the combustion region on the lower wall cannot intrude into the main flow in the cold inflow condition.

Characteristic Study on Effect of the Vent Mixer to Supersonic Fuel-Air Mixing with Stereoscopic-PIV Method

․ Byungil Choi*** ․ Toshinori Kouchi*** ․ Goro Masuya***ABSTRACT Vent mixer can provide main flow directly into a recirculatio n region downstream of the mixer to enhance fuel-air mixing efficiency. Based on experimental results of three-dimensional velocity, vorticity and turbulent kinetic energy obtained by a stereoscopic PIV met hod, the performance of the vent mixer was compared with that of the step mixer which was used as a basic model. Thick shear layers of the vent mixer induced the increase of the penetration heigh t. The turbulent kinetic energy mainly distributed along a boundary layer between the main flow and th e jet plume. This turbulent field activates mass transfer in a mixing region, leading to the mixi ng enhancement.초 록 벤트 혼합기는 혼합기 후류에 존재하는 재순환 영역으로 공기를 유입시켜 연료-공기 혼합을 증대시키는 혼합기이다. Stereoscopic PIV기법을 통해 얻은 3차원 속도, 와류, 난류운동에너지를 토대로 계단형 혼합기를 기본 모델로 하여 벤트 혼합기의 성능을 분석하였다. 벤트 혼합기는 두터운 전단층으로 인해 높은 침투거리를 보였으며, 난류운동에너지는 주로 주유동과 제트유동의 경계면을 따라 분포하였다. 이 난류 영역은 혼합영역 내에서 활발히 물질전달을 일으키며, 혼합 증대를 가져온다. Key Words: Vent Mixer(벤트 혼합기), Stereoscopic PIV(3차원 PIV), Vorticity Field(와류장), Counter- rotating Vortex Pair(한 쌍의 회전하는 와류), Turbulent Kinetic Energy(난류운동 에너지)