Experimental Research Of Combustion And Heat Transfer Characteristics In The Micro Combustors Partially Filled With Porous Medium

With the rapid development of Micro Electro Mechanical System(MEMS),a portal high-efficiency power supply device is becoming more and more urgent.And the micro-combustion which transfer chemical energy in the fuel to heat energy in the micro scale becomes a potential method.However,there exist some problems in the micro combustion such as large heat loss,shorter resident time and unstable flame.Based on there problems,an approach partially filled with porous medium in the micro planar combustor which can preheat the unburned premixed mixture to strengthen the combustion is put forward in the paper.An experimental set-up is designed and built.Through the experiments,four critical conditions are measured,including the blow off limits(Φ1);the flash back limits(Φ2);the limits of breaking through the porous medium(Φ3)and the limits of blowing out of the porous medium(Φ4).Once the critical conditions are ensured,the flame position can be given at any condition(Φ).For example,Φ<Φ1,to not be ignited;Φ1<Φ<Φ2,Bunsen flame at the combustor-outlet;Φ2<Φ,flash back;Φ4<Φ<Φ3,to be stabilized within the porous medium;Φ<Φ4,to blow off from the porous medium till extinguish.Through the experiments,it is found that filling conditions of the porous medium,porosity of the porous medium,and size of the micro combustors will influence the critical conditions and stability limits.Among all above elements,the width of the combustor will influence most.With the larger of the width of the micro-combustor,the stability limits are narrowed obviously.Besides,the heat radiance of the combustor-wall is also calculated.The results show that although when the combustor width increases and the wall temperature rise,but the wall heat radiance instead;it is also found that the wall temperature peak move to the combustor entrance as the porous medium(Lin)increase but the wall radiance reached the maximum at 8 mm away from the entrance of the combustor(Lin=8 mm).And fixed the position of the porous medium,change the width of the porous medium(W).It was found that: at the porous medium width of 5 mm(W=5 mm),the highest peak,and the corresponding wall radiance are the highest.The results will provides a theoretical foundation for micro combustion.