Effect of a catalytic segment on flame stability in a micro combustor with controlled wall temperature profile

Energy ◽  
2018 ◽  
Vol 165 ◽  
pp. 522-531 ◽  
Author(s):  
Shixuan Wang ◽  
Linhong Li ◽  
Yongfang Xia ◽  
Aiwu Fan ◽  
Hong Yao
Keyword(s):  
Temperature Profile ◽  
Wall Temperature ◽  
Flame Stability ◽  
Micro Combustor

Flame Chromatography: Toward Fuel Indexing Based on Multiple Weak Flames in a Meso-Scale Channel With a Prescribed Temperature Profile

2011 ◽  
Author(s):  
Kaoru Maruta
Keyword(s):  
Temperature Profile ◽  
Wall Temperature ◽  
Wide Temperature Range ◽  
Ignition Temperature ◽  
Flame Stability ◽  
Research Octane Number ◽  
Multi Stage ◽  
Auto Ignition ◽  
First Time ◽  
Meso Scale

For understanding flame stability in microcombustor, fundamental studies on the combustion characteristics in a meso-scale channel with a prescribed wall temperature profile have been conducted. Results showed that the existence of dynamic oscillatory flames and weak flames in addition to the normal propagating flames for the first time. It is then recognized that the weak flame phenomena can be applied for examining multi-stage oxidation of hydrocarbon fuels in wide temperature range from 300K up to auto-ignition temperature. Based on the preliminary experiments with various fuels including primary referenced fuel for gasoline, research octane number (RON) of the test fuels can be clearly described by the aspects of the stabilized stationary multiple weak flames. The methodology can be termed “flame chromatography” and it is expected to be applied for fuel indexing of future alternative fuel characterizations.

A numerical study on the blow-off limit of premixed hydrogen/air flames in a cylindrical micro-combustor

2020 ◽  
pp. 095441002097144
Author(s):  
Saeed Naeemi ◽  
Seyed Abdolmehdi Hashemi
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Flow Velocity ◽  
Equivalence Ratio ◽  
Numerical Study ◽  
Flame Stability ◽  
Convection Coefficient ◽  
Inlet Flow ◽  
Micro Combustor ◽  
Emissivity Coefficient

In the current work, a numerical study on combustion of premixed H2–air in a micro-cylindrical combustor was carried out and the critical velocity of inlet flow that causes the blow-off was obtained. Furthermore, the effects the equivalence ratio, wall thickness, geometry of combustor and thermal properties of walls on the critical blow-off velocity were studied. The numerical results showed that, increasing the equivalence ratio results in higher critical blow-off velocity. A micro combustor with thicker wall had better flame stability. As the combustor dimeter is decreased the blow-off occur in lower inlet flow velocity. Higher thermal conductivity of walls increases the critical blow-off velocity. In addition, with varying heat convection coefficient (h) and emissivity coefficient [Formula: see text] of the walls from 1 to 60 W/m2.K and 0.2 to 0.8 respectively, the critical blow-off velocity is reduced and shows the importance of wall thermal properties in the design and operation of micro-combustors.

Laboratory Combustibility Testing of Solid Fuel

1980 ◽  
Vol 102 (3) ◽  
pp. 666-671
Author(s):  
E. C. Winegartner ◽  
C. J. Lin
Keyword(s):  
Residence Time ◽  
Wall Temperature ◽  
Solid Fuels ◽  
Excess Oxygen ◽  
Flame Stability ◽  
Firing Rates ◽  
Low Load ◽  
Carbon Burnout ◽  
Load Conditions

A laboratory furnace having a controlled wall temperature is used to measure the combustibility of coal and other solid fuels. Operation at wall temperatures of 1260–1370°C (2300°–2500° F) permits determination of percent carbon burnout as a function of residence time and excess oxygen under furnace conditions representative of those encountered in large boilers. Operation at decreasing wall temperatures provides information on flame stability under conditions approaching those encountered under low load conditions in operating boilers. Firing rates are generally in the range of 11.7–29.3 KWt (40–100k BTU/hr) permitting testing of 100–150 kg (200–300 lb.) samples which can reasonably be obtained by core drilling or from small pilot units.

The Analytical Modeling of Finite-Length Homogonous Micro-Combustor for a Hydrogen-Oxygen Mixture with Wall Temperature Effects

2016 ◽  
Vol 32 (5) ◽  
pp. 631-642 ◽  
Author(s):  
S. A. Fanaee
Keyword(s):  
Reaction Zone ◽  
Finite Length ◽  
Wall Temperature ◽  
Iterative Solution ◽  
Maximum Temperature ◽  
Oxygen Mixture ◽  
Governing Equations ◽  
Computational Data ◽  
Micro Combustor ◽  
Acceptable Agreement

AbstractThis paper analytically investigates the reaction phenomenon in micro-combustors using a two-dimensional model. The length of micro-combustor is considered at finite length that makes a better physical model than other works. The micro-combustor medium is divided into three integral zones composed of preheat, reaction and post flame where the governing equations are solved using the matching conditions of neighboring zones. The reaction zone thickness is considered as a variable and predicted by an iterative solution. In order to validate the model, normalized magnitude of maximum temperature is compared with published computational data for different values of Peclet number that shows an acceptable agreement that confirms the accuracy of the predicted data. Since a higher wall temperature causes the reaction to be faster, increasing the normalized wall temperature will result to reduce reaction zone thickness.

scholarly journals Passive generation from a novel thermoelectric energy harvesting system model integrated with phase change material

2019 ◽  
Vol 111 ◽  
pp. 03060
Author(s):  
Yoo-Suk Byon ◽  
Hansol Lim ◽  
Yong-Kwon Kang ◽  
Soo-Yeol Yoon ◽  
Jae-Weon Jeong
Keyword(s):  
Phase Change ◽  
Temperature Profile ◽  
Phase Change Material ◽  
Temperature Difference ◽  
Wall Temperature ◽  
Waste Heat ◽  
Thermoelectric Energy ◽  
Temperature Method ◽  
Thermoelectric Energy Harvesting ◽  
Change Material

The purpose of this research is to evaluate the performance of a novel model that incorporates a thermoelectric generator (TEG) and phase change material (PCM). The proposed model passively generates electricity using waste heat that accumulates at exterior wall surfaces. The main generator is a TEG. To maintain the temperature difference between the two sides of the TEG, PCM is located at its cold side—thus converging the heat transferred into latent heat. The proposed passive generation system is formed into a TEG-PCM block. The block can be stacked to form a wall or inserted into any part of a building that faces the sun. The experiment setup is based on a constant temperature method. The wall temperature profile is set according to solar radiation, convection, and radiative heat transfer. To replicate daily wall temperatures during the experiment, a heat plate is used to match a wall temperature profile. Step control was used for the heating plate. The resulting data shows the average temperature difference between the hot and cold sides of the TEG to be 10-20°C. The peak generated electricity was 0.08 W for a single module.

scholarly journals Fundamental Numerical Analysis of a Porous Micro-Combustor Filled with Alumina Spheres: Pore-Scale vs. Volume-Averaged Models

2021 ◽  
Vol 11 (16) ◽  
pp. 7496
Author(s):  
Qingqing Li ◽  
Jiansheng Wang ◽  
Jun Li ◽  
Junrui Shi
Keyword(s):  
Porous Media ◽  
Flame Temperature ◽  
Scale Model ◽  
Solid Matrix ◽  
Flame Stability ◽  
Pore Scale ◽  
Flame Zone ◽  
Heat Recirculation ◽  
Micro Combustor ◽  
Averaged Model

Inserting porous media into the micro-scale combustor space could enhance heat recirculation from the flame zone, and could thus extend the flammability limits and improve flame stability. In the context of porous micro-combustors, the pore size is comparable to the combustor characteristic length. It is insufficient to treat the porous medium as a continuum with the volume-averaged model (VAM). Therefore, a pore-scale model (PSM) is developed to consider the detailed structure of the porous media to better understand the coupling among the gas mixture, the porous media and the combustor wall. The results are systematically compared to investigate the difference in combustion characteristics and flame stability limits. A quantified study is undertaken to examine heat recirculation, including preheating and heat loss, in the porous micro-combustor using the VAM and PSM, which are beneficial for understanding the modeled differences in temperature distribution. The numerical results indicate that PSM predicts a scattered flame zone in the pore areas and gives a larger flame stability range, a lower flame temperature and peak solid matrix temperature, a higher peak wall temperature and a larger Rp-hl than a VAM counterpart. A parametric study is subsequently carried out to examine the effects of solid matrix thermal conductivity (ks) on the PSM and VAM, and then the results are analyzed briefly. It is found that for the specific configurations of porous micro-combustor considered in the present study, the PSM porous micro-combustor is more suitable for simplifying to a VAM with a larger Φ and a smaller ks, and the methods can be applied to other configurations of porous micro-combustors.

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