Abstract
Micro-electro-mechanical systems (MEMS) occupy an important position in the national economy and military fields, and have attracted great attention from a large number of scholars. As an important part of the micro-electromechanical system, the micro-combustor has serious heat loss due to its small size, unstable combustion and low combustion efficiency. Aiming at enhancing the heat transfer of the micro-combustor, improving the combustion stability and high-efficiency combustion, this paper embedded porous media in the combustor, and the effects of different parameters on the combustion characteristics were numerically studied. The research results showed that the layout of porous media should be reasonable, and the small and large pore porous media embedded in the inner and outer layers, respectively, can bring better combustion performance. Meanwhile, A: 10–30 has a high and uniform temperature distribution, and its methane conversion rate reached 97.4%. However, the diameter ratio of the inner layer to the outer layer (d/D) of the porous medium should be maintained at 0.4–0.6, which brings a longer gas residence time, and further enables the pre-mixed gas to preheat and burn completely. At a d/D of 0.5, the combustor has the highest outer wall temperature and CH4 conversion efficiency. Besides, compared with the pore size increasing rate of Δn = 10 PPI and Δn = 10 PPI, the radial temperature distribution of the Δn = 10 PPI combustor is more uniform, meanwhile avoids the occurrence of local high temperature. Under the condition of Δn = 10 PPI, A: 20–30 layout maintains excellent thermal and combustion performance. In addition, the lean flammable limits of MC-U20, MC-10/30-0.8, and MC-20/30-0.5 were compared, at an inlet velocity of 0.5 m/s, the corresponding lean flammable limits are 0.5, 0.4, and 0.3, respectively, among them MC-20/30-0.5 has a wider flammable limit range, showing excellent combustion stability. This research has guiding significance for the combustion stability of the micro combustor.
Highlights
Microelectromechanical systems (MEMS) have broad application prospects in the national economy and military fields, especially in the fields of electronics, medicine, industry, automobiles, and aerospace systems [1,2,3]
In order to study the influence of the porous media layout on the combustion characteristics, three porous media layouts were selected
The second is the layout of 30 PPI in the outer layer porous media and 10 PPI in the inner layer porous media, expressed as A: 10-30
Summary
Microelectromechanical systems (MEMS) have broad application prospects in the national economy and military fields, especially in the fields of electronics, medicine, industry, automobiles, and aerospace systems [1,2,3]. Yang [27] adopted a cavity design to broaden the blowing limit of the flame, and found that the cavity can improve the combustion efficiency and improve the flame tip splitting phenomenon He [28] and other relevant scholars have conducted a large number of studies to prove the steady burning effect of blunt body, especially in improving combustion efficiency, making the application of cavity and blunt body in micro combustors reach a high level [29,30,31,32,33,34]. More and more scholars from the perspective of thermal management, are adopting measures to reduce heat loss, so as to pursue efficient and stable combustion This method mainly uses heat recirculation to reduce heat dissipation loss, let high temperature exhaust preheat low temperature gas, improve the inlet gas temperature to stabilize combustion. This paper proposes to embed porous media in a micro-combustor, and reasserted the effects of porous media layout, interlayer diameter ratio (d/D), pore size increase rate, and lean flammability limit, so as to provide a basis for the design of porous media in the micro combustor
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