| Along with the rapid development of MEMS technology, micro dynamic system has become the research focus of research, the micro dynamic system has the broad application prospect in national defense and economic construction. Currently micro combustor mainly adopts hydrocarbon fuels for electricity, heat and heat power transformation.Combustion in micro scale has great difference than in large scale. Combustion in micro scale will encounter problems such as surface/volume relative increase, heat loss increase and time scale shortening etc. At present micro scale combustion is mainly concentrated in gas hydrocarbon fuels, and the liquid hydrocarbon fuels are still in the experimental stage research. Liquid fuel combustion is much more complicated than gas fuel, but liquid hydrocarbon fuels has advantage of big density, small volume etc. Liquid hydrocarbon fuels are more suitable for micro combustor. Therefore, research of the liquid fuel burning in micro cause our attention. Based on experimental study of liquid ethanol lamimar disffusion characteristics, experimental and numerical simulation method combining study is used to analyze the relationship between flame characteristics size, the flame temperature and flow characteristics and tube diameter, fuel flow field. Thus reveals the liquid fuel combustion mechanism in micro scale, it will lay the foundation for micro combustor to develop.In the process of experiment research, three different specifications of micro scale ceramic burner with inner diameter 0.6 mm,0.4 mm and 1.0mm ceramic tubeare slected as combustors.The injection pump supplies micro flow of liquid fuel. Stered microscope with digital cameras and micro computer observe flame structure.S-type thermocouple measures temperature of micro flame. High-voltage dc power provides strong electric fields.In numerical simulation process, using numerical simulation software Fluent6.3 establishes three-dimensional numerical combustion model corresponding with the experiment.Considering the micro-structure of ceramic tube, the grid type of Tet/Hybrid and the gridding method of TGrid are slected.Selecting laminar model as flow mathematical model, P-1 radiation model as radiation heat transfer, laminar finite rate model as combustion chemical reation, general finite rate chemical reation model as liquid fuels transport and combustion, UDS as solving electric field,solver based on pressure as numerical calculation.In the experiment and numerical simulation based on laminar diffusion flame liquid ethanol shape characteristic, characteristic size and temperature field characteristic are analyzed.The study results show that the quenching limit flame, stability flame and oscillation flame in the experiment is highly similar to the flame shape structure of numerical simulation.The relations between micro flame height and width in the experiment and numerical simulation and liquid ethanol volume flow are linear increasing and linear slopes in numerical simulation are high than in the experiment, this illustrate that numerical simulation models can be used for small flow range; the numerical simulation values of micro flame height and width are larger than experimental values, but the deviations are less than 10% and belong to allow deviation range.In different flow conditions, the numerical simulation values of the micro flame temperature agree well with experimental values,the deviations are less than 3%.The above analysis proves the reliability of numerical simulation.In order to reveal that the ceramics tube inner diameter, Reynolds number and electric field are influence to micro flame structure, the temperature field, concentration field and velocity field effect, the results of numerical simulation are analyzed emphatically. The study results show that the boundary sliding and thermal diffusion have a direct impact on flame structure and flame temperature and the impact of the boundary sliding and thermal diffusion is larger when inner diameter is smaller.The relation between the higherst temperature and Re is open side down parabola,under the condition of different inner ceramic tube and different additional electric field,the maximum values of the highest temperature of the flame with corresponding Re are different; the positive and reverse electric field can improve the maximum values of the highest temperature of the inner diameter 0.6mm and 1.0mm ceramic tubes and reduce the maximum values of the highest temperature of the inner diameter 0.4mm ceramic tube. The relation between the flame temperature and pipe orifice distances at the central axis is left slant and open side down parabola, slant degree is larger when inner diameter is smaller; the positive and reverse electric field has a great influence on temperature field distribution of larger inner diameter ceramic tube, has less influence on themperature field distribution of small inner diameter ceramic tube.Reverse electric can reduce the flame temperature of X axis of inner diameter 1.0mm and 0.4mm ceramic tubes, positive electric field can reduce the flame temperature of X axis of inner diameter 0.6mm ceramic tube. The relation between flame dimensionless height and width and Re is linear; increasing range of flame dimensionless height and width will be larger when inner diameter ceramic tube is small without additional electric field; the positive and reverse electric field has less influence on flame dimensionless height and width of inner diameter 1.0mm ceramic tube; the positive and reverse electric field has less influence on flame dimensionless width of inner diameter 1.0mm and 0.6mm ceramic tube, but it can improve flame dimensionless width of inner diameter 0.4mm ceramic tube; the positive electric field can improve flame dimensionless height of inner diameter 0.6mm ceramic tube and reduce flame dimensionless height of inner diameter 0.4mm ceramic tube; the reverse electric field can reduce on flame dimensionless height of inner diameter 0.6mm ceramic tube and improve flame dimensionless height of inner diameter 0.4mm ceramic tube.The reverse electric field can reduce ethanol mass fraction of inner diameter 1.0mm cenramic tube on the central axis and improve ethanol mass fraction of inner diameter 0.4mm and 0.6mm cenramic tubes on the central axis.Fluid velocity can change rapidly because liquid ethanol is heated to gaseous ethanol in ceramic tube, the relation between fluid velocity and ceramic tube inlet distance is linearity increase.Velocity linearity slope of inner diameter 1.0mm ceramic tube is the smallest and velocity linearity slope of inner diameter 0.4mm ceramic tube is the largest; the positive and reverse electric field can improve fluid velocity change in cermic tube.The distribution curved shape of X axis fluid velocity is open down parabola,X axis fluid velocity is more obvious when the inner diameter is smaller, the reverse electric field can reduce fluid velocity of inner diameter 1.0mm ceramic tube, the positive and reverse electric field can improve fluid velocity of inner diameter 0.6mm and 0.4mm ceramic tubes.Clearly, there is close relation between inner diameter of ceramic tube, Reynolds number and electric field and flame structure, temperature field, concentration field and velocity field.
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