Mixing Control System Using Micro Nozzle of 3D Vortex Generator and Flame holder Aiming at High-Speed Diffusion Combustion

2002 Fiscal Year Final Research Report Summary

• Project/Area Number: 12450087
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Thermal engineering
• Research Institution: KYOTO UNIVERSITY
• Principal Investigator: YOSHIDA Hideo Dept. of Mechanical Eng., Professor, 工学研究科, 教授 (50166964)
• Co-Investigator(Kenkyū-buntansha): KOBAYASHI Kenichi Meiji Univ., Dept. of Mechanical Eng., Assistant Professor, 理工学部, 専任講師 (10242273) ; SAITO Motohiro Dept. of Mechanical Eng., Res. Associate, 工学研究科, 助手 (90314236)
• Project Period (FY): 2000 – 2002
• Keywords: combustion / high-speed diffusion combustion / flame holding / micro nozzle / mixing control

Research Abstract

For combustors of microturbines, enhancement of flame holding and mixing in a high-speed flow is crucial to make the combustor compact and also realize isothermal expansion combustion. To this end, we propose a combined nozzle and flame holder with small dimensions. That is, in the downstream of relatively high-temperature gas flow, a micro object, the shape of which is similar to an angel fish, is introduced as a fuel injector: on the back side of the injector, intense turbulence is generated.
In the experiment, first, we prepared a high-speed and high-temperature wind tunnel. The attained maximum velocity and temperature were 105m/s and 550℃, respectively. Secondly, V-type and U-type fuel injectors which are two or three times larger than the final ones were used to obtain fundamental mixing and flame holding characteristics; their length and width are 1.5mm and 1mm, respectively. The V-shaped injector shows higher flame holding performance than the U-shaped injector, which indicates the validity of an angel-fish type micro injector.
On the other hand, to clarify the mixing mechanism on the back side of the micro injector in detail, a numerical calculation using k-e turbulence model was conducted varying the injector geometry, As a first step of the numerical analysis, a flow around backward facing step with concave wall was analyzed. It was found that for the case with the concave wall the streamwise length of a recirculation zone decreases. The velocity near the concave wall, where fuel-injection holes are installed, was about 1% of that of the main flow. These facts are preferable in terms of the mixing enhancement.
From the experimental and theoretical studies during 2000-2002, we conclude that the high potential of the present micro fuel injector as a high-speed diffusion combustion has been confirmed. An actual application to a microturbine combustor is now in progress.