Effect of the cavity depth on the combustion efficiency of lean H2/air flames in a micro combustor with dual cavities

2017 ◽  
Vol 42 (20) ◽  
pp. 14312-14320 ◽  
Author(s):  
Wei Yang ◽  
Ying Xiang ◽  
Aiwu Fan ◽  
Hong Yao
2019 ◽  
Vol 142 (4) ◽  
Author(s):  
Yunfei Yan ◽  
Kaiming Shen ◽  
Yu Cui ◽  
Ziqiang He ◽  
Li Zhang ◽  
...  

Abstract Effects of controllable vortex slotted bluff body parameters (position of a bluff body, slit size, and controllable flow ratio) on the combustion characteristics of hydrogen/air in a micro-combustor with a bluff body were investigated numerically. The results illustrated that the combustion efficiency of hydrogen decreases with increasing distance (L1) between the front edge of the bluff body and the combustor inlet. The combustion characteristics of the micro-combustor are optimum when L1 is 0 mm. The blow-off limit of the combustor reaches a maximum (564 cm3/s) when the slit width (d) is 20% of the bluff body width. The blow-off limit first increases and then decreases when the equivalence ratio (φ) increases and reaches a maximum (732 cm3/s) when φ is 1.0, and the controllable flow ratio is 0.2. The combustion efficiency of hydrogen is gradually increased with the increase in the controllable flow ratio. When φ is less than 1.0, the optimal controllable flow ratio gradually decreases with the increase in the premixed gas flow rate, and the optimal controllable flow ratio basically remains at 0.6 when the premixed gas flow rate is less than 360 cm3/s.


Energies ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3821 ◽  
Author(s):  
Xiao Yang ◽  
Zhihong He ◽  
Lei Zhao ◽  
Shikui Dong ◽  
Heping Tan

Improving the flame stability and thermal behavior of the micro-combustor (MC) are major challenges in microscale combustion. In this paper, the micro combustions of an H2/air premixed flame in a swirl MC with various channel diameters (Din = 2, 3, 4 mm) were analyzed based on an established three-dimensional numerical model. The effects of hydrogen mass flow rate, thermal conductivity of walls, and the preferential transport of species were investigated. The results indicated that the flame type was characterized by the presence of two recirculation zones. The flame was anchored by the recirculation zones, and the anchoring location of the flame root was the starting position of the recirculation zones. The recirculation zones had a larger distribution of local equivalence ratio, especially in the proximity of the flame root, indicating the formation of a radical pool. The combustion efficiency increased with an increasing Din due to the longer residence time of the reactants. Furthermore, the MC with Din = 2 mm obtained the highest outer wall temperature distribution. However, the MC with Din = 4 mm had a better uniformity of outer wall temperature and large emitter efficiency due to the larger radiation surface. An increase in thermal conductivity boosts the thermal performance of combustion efficiency, emitter efficiency, and wall temperature uniformity. But there is a critical point of thermal conductivity that can increase the thermal performance. The above results can offer us significant guidance for designing MC with high thermal performance.


2012 ◽  
Vol 608-609 ◽  
pp. 934-940
Author(s):  
Jian Wu ◽  
Bo Li ◽  
Bin Xu ◽  
Jia Xuan Miao

As the critical component of the system, micro-combustor requires a high and uniform temperature distribution along the wall to meet demands for the band gap of the PV cells. The past experiments have proved that the peak wall temperature of the combustor with porous media increases obviously. This paper will have a research on stratified porous media to enhance the combustion efficiency of the combustor and reduce the emissions.


Energies ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6577
Author(s):  
Dongli Tan ◽  
Guicheng Ran ◽  
Guangling Xie ◽  
Jie Wang ◽  
Jianbin Luo ◽  
...  

With the improvement and development of micro-mechanical manufacturing technology, people can produce an increasing variety of micro-electromechanical systems in recent years, such as micro-satellite thrusters, micro-sensors, micro-aircrafts, micro-medical devices, micro-pumps, and micro-motors. At present, these micro-mechatronic systems are driven by traditional energy power systems, but these traditional energy power systems have such disadvantages as short endurance time, large size, and low energy density. Therefore, efforts were made to study micro-energy dynamical systems with small size, light gravity, high density and energy, and long duration so as to provide continuous and reliable power for these systems. In general, the micro-thermal photoelectric system not only has a simple structure, but also no moving parts. The micro-thermal photoelectric system is a micro-energy power system with good application prospects at present. However, as one of the most important structural components of micro-thermal photoelectric systems, the microburner, is the key to realize the conversion of fuel chemical energy to electric energy in micro-thermal photoelectric system. The studies of how to improve the flame stability and combustion efficiency are very necessary and interesting. Thus, some methods to improve the performance of micro-burners were introduced and summarized systematically, hoping to bring some convenience to researchers in the field.


2003 ◽  
Vol 125 (3) ◽  
pp. 487-493 ◽  
Author(s):  
Dae Hoon Lee ◽  
Dae-Eun Park ◽  
Euisik Yoon ◽  
Sejin Kwon

Combustion measurement in a cylindrical micro combustor, the construction procedure and test run of a MEMS reciprocating device are described. The sizing of the MEMS device was based on the findings of combustion measurements. Thermodynamic analysis of the pressure measurement resulted in available work up to 2.4 Joules in a combustor height of 2 mm and more with combustion efficiency of 0.6∼0.7. With combustor height less than 2 mm, combustion was incomplete due to excessive heat loss to the wall. In order to achieve the chamber height imposed by the combustion measurement, a fabrication process and wafer material that allow deeper etching was used.


Author(s):  
Yunfei Yan ◽  
Li Zhang ◽  
Jingyu Ran ◽  
Jie Zhang

In micro combustors, the residence time of gas is dramatically reduced. It is much more important to improve combustion efficiency and stability of the micro-combustor by improving the uniformity of flow distribution and mixed results in micro premixing chamber. The flow distribution in micro premixing chamber is analyzed. The influence of micro premixing chamber structures (including the diameter of fuel inlet, numbers of arc-shaped and straight micro-channels, distance and numbers of subordinate fuel inlets) on the uniformity of flow distribution and premixing characteristics is numerical investigated. The influence of the different structure of micro premixing chamber is gained. It is an important guide for designing high efficient micro premixing devices.


Author(s):  
Kousuke Isomura ◽  
Motohide Murayama ◽  
Hiroshi Yamaguchi ◽  
Nobuaki Ijichi ◽  
Nobuyoshi Saji ◽  
...  

A gas turbine at micro-scale is under development at Tohoku University in conjunction with Ishikawajima-Harima Heavy Industries Co., Ltd. (IHI). The development of the engine is currently at the stage of experimentally proving the component performance required to realize the Brayton cycle. The component tests are split into two activities at current stage to separate the effect of the heat transfer from the combustor to the compressor, which was shown to have large effect on the component efficiency, by previous studies. Current objective of the tests is to clarify whether the gas turbine at micro-scale is feasible from the point of performance change due to the scaling effect. A micro-turbocharger has been developed to prove the performance of the compressor and the bearing. It has been started operating and the micro-turbocharger tests are currently underway. Micro-combustors have been developed to find the appropriate configuration of the micromachine gas turbine. It has successfully been designed and tested to achieve 99.9% of combustion efficiency with both Hydrogen and Methane fuel.


2015 ◽  
Vol 19 (6) ◽  
pp. 2185-2194
Author(s):  
J.F. Pan ◽  
Z.Y. Hou ◽  
Y.X. Liu ◽  
A.K. Tang ◽  
J. Zhou ◽  
...  

Micro-combustors are a key component in combustion-driven micro power generators, and their performance is significantly affected by their structure. For the application of micro-thermophotovoltaic (MTPV) system, a high and uniform temperature distribution along the walls of the micro combustor is desired. In this paper, a three-dimensional numerical simulation has been conducted on a new-designed parallel plate micro combustor with two nozzles. The flow field and the combustion process in the micro combustor, and the temperature distribution on the wall as well as the combustion efficiency were obtained. The effects of various parameters such as the inlet angle and the fuel volumetric flow rate on the performance of the micro combustor were studied. It was observed that a swirl formed in the center of the combustor and the radius of the swirl increased with the increase of the inlet rate, and the best working condition was achieved at the inlet angle ?=20?. The results indicated that the two-nozzle combustion chamber had a higher and more uniform mean temperature than the conventional combustor under the same condition.


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