Numerical Investigation On Performance Of Ramjet Combustion With Nonuniform Inlet Flows

Compared with gas turbine engine, ramjet engine has no compressor and turbine, having simple structure, light quality, low cost, supersonic flight and other characteristics,these are dominances that have attracted international researchers’ attention. Combustor is a core component of ramjet engine, High inlet velocity for ramjet is difficult to organizely burn, to improve the mixing gas-oil and oil residence time, therefore design good performance of film vapor flameholder is important for ramjet combustor. In this paper, based on blockage ratio0e, flame stability parameterstK and structural parameters within flameholder etc, that gets the design rules of film vapor flameholder.In this paper uses Volvo experimental examples to make sure numerical methods applied were corrected, and it indicates that standard k -e turbulence model suits the imulation study of the flameholder. The value of the skirt’s length with two-dimensional film vapor flameholder was identified and researched the inner flow field of flameholder, including vortex center postion of recirculation zone, distribution of velocity, pressure and temperature, the results show that for incompressible flow, speed of recirculation zone and vortex strength are mainly affected by the value of inlet velocity, inlet velocity doesn’t affect distribution of the recirculation zone’s vortex center postion. For the thermal flow field, the distribution of vortex center postion in addition to is affected by the structure of flameholder and the interaction force of recirculation zone, also with it is impacted on the squeezing action of high temperature and high pressure gas. But for the cold flow field, the distribution of vortex center postion is only affected by the structure of flameholder and the interaction force of recirculation zone; Axial position of extreme point about axial velocity coincides with axial postion of vortex center located in coss section.In order to improve the performance of ramjet combustor, the structure of flameholder’s jagged edges and fuel system need be designed and be to researched. When the blockage ratio0e is the same, the larger the angle b of the flameholder’s jagged edges is, the higher combustion efficiency of the flameholder will be. When uses two layers of the nozzle which is based on the normal jagged edges, and combustion efficiency is higher than the distribution of the single layer nozzle about 10%.In this paper, the speed’s nonuniform d was introduced to describe uneven degree of inlet the airflow, different Sine wave types of nonuniform inlet velocity are constructed to investigate the impact on the performance of the flameholder. The mechanism of both sides of jagged edges producing streamwise vorticity and the effect streamwise’s on mixing oil and gas need be studied.The results show that the nonuniform velocity of the inlet changes fuel distribution in flameholder leading to the variation of combustion efficiency. The film vapor flameholder Uses separate fuel system, distribution of flameholder’ internal oil and gas is affected on out fluid a little, it playes a role of precombustion chamber that could impairs adverse effect on the products of nonuniform inlet velocity for flameholder and increase the combustion efficiency.The film vapor flameholder has a strong ability to impair adverse effect on distribution of inlet Velocity along the XZ plane, but it has a weak ability to impair adverse effect on inlet Velocity’ distribution along the XY plane. Because the structure of flameholder’s jagged edges was symmetrical, so air flowing though the jagged edges can respectively produce streamwise vorticity on both sides of flameholder in out flow and internal flow of flameholder’s jagged edges. The vorticity about both sides of jagged edges’ streamwise vorticity is the same in the value, but the direction of streamwise vorticity is on the contrary. The direction of streamwise vorticity which is on the same side of flameholder’s jagged edges is the same, streamwise vorticity isn’t only advantageous to mix of oil and gas, but also impairs adverse effect on inlet Velocity’ distribution along the XY plane.