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1.
Aiming at the questions of raceway section two dimension temperature distribution from two dimensional image accumulated by three dimensional radiation space and three dimensional temperature reconstruction error caused by limited charge coupled device (CCD) sensors for a sudden spread combustion chamber, the two dimension rectangle interpolation virtual CCD sensor installation algorithm is provided as a new technology for solving the difficulties of installing more CCD sensors and filtered back projection reconstruction error caused by limited projection numbers. The radiation intensity projection data got from flame image collected from the installed CCD sensors and computed virtual CCD sensors is interpolated for filtered back projection to computer intensity distribution and calibrated bi color method is used to calculation temperature in raceway depth direction. The results of experiments on a mini type coal gas furnace and practice test showed that the algorithm is accurate and credible and realized the on line monitoring for sudden spread combustion chamber raceway depth direction. At the same time, the useful information is provided for further studying combustion working state for the sudden spread combustion chamber. 相似文献
2.
A kind of small scale wind tunnel with low velocity is proposed according to the characteristics of strong ionization discharge chamber and the demands of discharge for flux, velocity and flow fields. On the precondition that the airflow field and velocity is satisfied, aerodynamic design and structural design are carried out. Key techniques are studied including overall structure, aerodynamic and structural design of airflow vent and collection vent, aerodynamic and structural design of power section, flow rate adjustment and control, and cooling system of motor. Based on the design scheme, a small scale wind tunnel with strong ionization discharge for an enterprise is developed. Application indicates that the small scale wind tunnel is a practical and effective airflow loop device for high pressure and strong ionization discharge with the features of stability and reliability. 相似文献
3.
According to the volatile combustion, the mathematical and physical models on the volatilization combustion of coal field fire area are established. The governing equations are analyzed by analytic method. The parameters such as volatilization combustion speed, the content of volatile component and the flame temperature are obtained at relatively high temperature environment. According to the solutions, the flame temperature of the volatilization combustion is calculated by the heat insulation temperature in the light of the low-heat value of the volatile component. Due to the free or forced convection in the actual fire area, the true temperature would be lower than the calculation. Through experiment, heating process takes the greatest impact on the heating surface but least on inner parts. The temperature is increased and the heating surface temperature will exceed the temperature and continue increasing, which indicates that the coal begins oxidation. While the airflow is increased, the temperature will be slightly increased. The temperature is descent more slightly in the coal temperature because of thermal radiation. 相似文献
4.
Numerical simulation on low calorific value coal-bed gascombustor and structural design optimization
This paper conducts the full size three-dimensional combustion numerical simulation study on the low-calorific value coal bed gas combustor. It explors the effects of different ratios of swirling wind and straight wind on flow field,temperature field and concentration field when this combustor combusts coal bed gas which methane volume concentration is 30 percent. The optimal ratio of swirling wind and straight wind is gained. Based on this,the number and obliquity of cyclone vane in gas pipeline are further optimized. The results show that when ratio of straight wind is 80 percent and ratio of swirling wind is 20 percent,the good jet flow rigidity is not only possessed,but also the strong spin momentum is brought. Reverse axial velocity grads and reverse velocity in central backflow region are also big,the burning temperature and combustion efficiency are high,and high-temperature region is diffusely distributed. When the number and obliquity of cyclone vane are respective 6 and 60,the mass fraction of methane descends quickly,the mass fraction of methane is low in outlet of combustion region,and the combustion efficiency is high. 相似文献
5.
To accurately analyze the loss and heat of large hydro generator,the finite element models of 2D steady state electromagnetic field,moving electromagnetic field and field circuit coupling are established respectively.As an example,the losses of the rotor iron and damper winding of a 36 MW tubular hydro generator are calculated.Furthermore,the influences of 3 different electromagnetic field models on the thermal sources and temperatures are analyzed by 3D finite element calculation of the temperature field.The results are compared with the test data and indicate that the precision of the field circuit coupling model is better.The losses of each damp bar are different and the heat of the damp bar at the lee side is larger than that at the windward with the full load.The maximal temperature of the rotor is located at the damper winding,instead of the field winding.The research is valuable for improving the calculation precision of the rotor losses and temperature field and enhancing the reliability of the hydro generator design and operation. 相似文献
6.
The field models for smoke flow in atrium, takings into account strong buoyancy, turbulence, radiation exchange and wall heat losses are developed according to the characteristics of the atrium fire. Realistic combustion processes in the burning fuel have not been included. A six-flux radiation model is included in a general mathematical model for fires, which are taking as a volumetric heat source, It is applied to the predictions of fire smoke development in a small-scale atrium. In order to avoid complicated radiation exchange models, radiation heat loss effects are combined to the wall heat loss. A General-purpose compute program PHOENICS has been developed to meet this need. Results of numerical calculations based on the field model are compared with test data for a fire in the small-scale atrium test facility. The resullts indicate that radiation transfer has the minor effects, due to the relatively low temperatures encountered. The method that the effect of radiation is included in the calculation of wall heat transfer losses by using maximum heat transfer coefficient is feasible. The field model used in the present study is not good enough, which a turbulent combustion sub-model must be included. 相似文献
7.
To be effectively heated in incinerator for MSW is very important for stabilization and completeness combustion, the smaller produce of the PCDD/Fs. At the same time, the transient heat transfer characteristics of the MSW lump decides the stay time of the MSW in incinerator and effects on the operation feature of the combustion equipments. All of these would lead to design the reasonable and clean combustion project, the optimum incinerator and recover energy system. The component, shape, dimension, property, the hardly and inner structure feature of the MSW lump are taken in account, and the effective conduct heat coefficient has been adopted. And then, the physical model is setup with different shape(ball, cylinder, squareness), and the 3-D mathematical model and conduct heat efficient with porous feature for transient heat transfer of MSW lump are presented, at the same time, the simulation tests are gotten in various boundary and the interesting conclusions are gotten: The center stable temperature of the MSW lump is mostly decided by the inner gas temperature of the incinerator and the heated area of the lump. The transient heat transfer characteristics is variously effected by the shape of the MSW lump in incinerator. The transient process becomes longer and the center stable temperature decreases, the volatile can't be easily separated out and the combustion efficiency decreases because of the increasing of the lump feature dimension. 相似文献
8.
To research the influence of combustion chamber thermal boundary conditions on micro combustion characteristics in micro ICE, the laminar flow finite rate model is adopted to simulate the micro combustion process. Firstly, the influence of grid scale, the time step length and the maximum iterations per time step on accuracy of simulation results are explored. The results show that simulation results agree well with experimental results. And then, the influences of heat transfer coefficient, wall thickness and material on combustion characteristics are discussed. The results indicate that heat transfer coefficient has obvious influence on combustion characteristics. The pressure rise rate decreases, the ignition delays and the highest pressure value drops 2 atmospheres as heat transfer coefficient increases from 0 to 55 W/(m 2·K). The wall thickness and material have a little effect on combustion characteristics. This is because that the main heat transfer resistance in the heat flow path from cylinder to external environment lies between the outer wall and environment. 相似文献
9.
The thermal radiation is the main factor affecting internal thermal flow field in a tunnel. This paper studies on two open ends of a channel inclined with angles of 10°, 20° and 30° by experiments and numerical simulations. The experimental data agree well with the predicted results by using Large Eddy Simulation (LES) to solve N-S equations driven by the buoyancy flow. And the influence of thermal radiation on thermal flow field of tunnel with inclination angles from 10° to 30° at same heat source is obtained by comparing the experiment results and numerical resolutions of coupled with radiation model and without radiation model. Thermal radiation makes temperature near the upper wall of tunnel drop, and the influence of thermal radiation on bottom end of tunnel declines with the inclination angle increasing. However, the inclination angle has a little effect on temperature near the ceiling of the top end of tunnel. Simultaneously, the higher temperature zone leaning to the top end due to the thermal radiation is obtained, and the temperature at the bottom of the upper part of the tunnel increases. The findings of the study are important references for theory research of thermal flow field in inclined tunnels. 相似文献
10.
The burning rate of hydrogen air pre mixture on meso scale is mainly determined by its chemical reaction rate. So a Laminar Finite Rate Model, the gas phase reaction mechanism for the combustion of hydrogen air mixture which consists of 19 reversible elementary reactions and the dynamic mesh method are adopted to simulate the combustion of hydrogen air mixture in a meso scale IC engine which operates a quasi gas power cycle under ultrahigh combustion load. The combustion of hydrogen air mixture on meso scale in the micro combustion chamber with moving boundary can be stable. The complete thermodynamic process of heat addition, internal energy increasing, and a boundary work output producing during expansion can be perfectly achieved in the closed combustion system of the meso scaled IC engine igniting the hydrogen air mixture by wire surface of high temperature. However, running parameters such as cycle period, initial pressure and fuel/air ratio have complex effects on the hydrogen air combustion of micro closed container with moving boundary. 相似文献
11.
Several previous general lumped parameter model of radioisotope concentration field in groundwater systems, such as EM, PM and EPM model, are introduced, and the ambiguous physical meaning of response functions within these models are pointed out.And then, based on the radioactive decay principles and mass conservation principle, assuming that 1)the fluid system is in steady state, 2)infiltration rate is constant, and 3)the horizontal transport of water flow rate is constant, a general lumped parameter model of radioisotope concentration-fluid coupled field in groundwater systems is deduced under these conditions, that is, Panel model.Compared with the above mentioned models, this new model is built on a clear physical basis with a definite physical meaning of each parameter, so that it could make accurate interpretations on radioisotope data of the relevant water flow system, and provide more precise mathematical foundation on quantitative analysis and simulation of radioisotope concentration. 相似文献
12.
《保鲜与加工》2003,(11):23-26
The characteristics of flow and combustion in micro gas turbine engine with the low Reynolds number and the high Mach number, the high Couette number and the low Biot number, as well as the ultra high duty ratio of combustion in very small space are analyzed, which are remarkably distinguished from those on macro scale. At the meantime, the limitation of traditional dynamic lubrication theory at ultra high speed on micro scale is presented, and the possibility of making the gas bearing to be able to work at ultra high speed by utilizing boundary slip is investigated. Due to the applied prospect of silicon carbide in the field of MEMS especially under high temperature and high strength conditions, the technical process of combining silicon etching with reactive sintering and grinding machining of silicon carbide is put forward so that the miniature machining of silicon carbide for micro gas turbine engine becomes possible. 相似文献
13.
To investigate the spatial electric field with the point-plate electrodes configuration, variations of the electric field intensity are analyzed for absolute air dielectric and liquid dielectrics contained in air dielectric based on the finite element method of numeric computation. The results show that the electric field intensity of the spatial electric field is great non-uniform with the point-plate electrodes configuration for absolute air dielectric, and it can be increased rapidly at the nozzle point to achieve a maximum value. Single oil drop existed in air dielectric induces a biggish deformation of the gradient of the electric field intensity in its neighbor field. Many oil drops along with horizontal distribution have an obvious tensioning operation on the electric field, so the electric field intensity on the normal at the nozzle point has an evident augment for overlapping effects among the oil drops, and it can spread electric corona area of the total spatial electric field. 相似文献
14.
电渣重熔能提高钢锭的质量,从而满足特种行业的需要,其过程伴随着复杂的物理现象,存在着磁流体流动、传热和传质以及电化学等多方面的影响。通过耦合电磁以及流动和温度方程对电渣重熔过程的三维瞬态进行了数学模拟,研究了熔化速率对重熔过程的影响。结果表明：电流密度、焦耳热和电磁力都随着熔化速率的增大而增大,当熔化速率由14.4 kg/h增加到27.0kg/h,电流密度、焦耳热和电磁力最大值的增大比例超过100%。随着熔化速率的增大,温度最大值有小幅的增加,而且速度最大值的增大幅度接近50%;金属熔池深度则由27 mm增大到38 mm,不利于保证铸坯的质量。 相似文献
15.
With the development of circulating fluidized bed boiler(CFB),the study field of external heat exchanger(EHE) is greater in extent and degree.In order to research the working process of EHE,the model which deals with flow and heat transfer of EHE for 300MW CFB of Dong Fang Boiler Grou PCo.Ltd.is presented.Based on the cell modeling theory,the EHE is divided into several chamber by heating surfaces.The mass and energy conservation equations of each cell have been developed according to some reasonable assumption.The complete mathematical model has been compiled by Fortran and solved by classical Algorithm of Runge-Kutta.The static test and perturbation experiment of simulating model has been performed.The simulation results show that the model has been reached the steady state rapidly,the dynamic responses are reasonable and the modeling presented in the paper is reliable and appropriate. 相似文献
16.
微型内燃机微燃烧过程对当量比和转速变化非常敏感,采用层流有限速率模型和甲醇氧化反应机理对其预混层流微燃烧过程开展仿真研究,探讨当量比和转速对微燃烧特性的影响规律及临界运行参数。在此基础上,提出采用热着火理论和化学反应动力学理论探索当量比对微燃烧特性的影响机理。结果表明仿真与实验比较吻合。当量比从0.6增加到1.1时,燃烧速率增加,压力和温度增加,压力最高值增加约1.5E+6 Pa,温度最大值增加约1 300 K,此后随当量比增加,燃烧速率减小,压力和温度减小。研究还进一步揭示了当量比影响微燃烧特性的机理: 稀燃区当量比主要通过温度变化来影响微燃烧特性,随当量比增加,燃料浓度增加,燃烧释放的总热量增加,所以温度和压力增加,燃烧速率增加;浓燃区当量比主要通过氧气量变化来影响微燃烧特性,当量比越大,氧气量越不足,基元反应速率越小,所以燃烧速率越小,温度和压力越低。转速越高,燃烧时间越短,燃烧越不充分,所以温度、压力越低。受微燃烧相对热损大、驻留时间短的特征影响,微型发动机实现完全燃烧的运行区域较窄,其实现完全燃烧的稀燃极限约0.9,最高转速约6 000 r/min。这在设计微型内燃机时值得关注。 相似文献
17.
The acoustic field,flow field and temperature field inside a muffler are studied by the numerical analyze method.And an improved design is made aiming at the existent problem.The comparison of the computationally predicted and the experimentally measured transmission loss shows a good agreement.It is indicated that the numerical analysis method can simulate the exhaust muffler's characteristic accurately.So it is an effective method to predict exhaust muffler's performance and have an improved design. 相似文献
18.
Ventilation design is the difficulty of transformer room design. Temperature field and velocity field in a transformer room was simulated by CFD method . By comparing simulation value with the experimental value in related document , the effectiveness of the mathematical model was verified. Based on it, an indoor substation transformer built was taken as the simulation object, then designed and simulated six kinds of ventilation condition by changing the location and area of air inlet, focused on the influence of air inlet on the ventilation effect by comparing the temperature field ,velocity field and temperature characteristic value in different condition. The simulation results show that when air inlet area is fixed, the air inlet should be arranged in the radiator side and its center height should be controlled in the radiator center height or slightly offset position, it should not be higher than the radiator. When the air inlet location is fixed, air inlet area should be increased along the high direction to improve ventilation effect. The conclusions can provide technical support for the ventilation design of transformer room. 相似文献
19.
In order to optimize design and operation, it is necessary to calculate accurately hydraulic characteristics large central air-conditioning systems. Simplified Model can not be applied to hydraulic calculation of large pipe network topological structure for its large calculation error. Taking into account the regulating characteristics of terminal branch temperature regulating valve, a direct-return chilled water system is studied, an accurate mathematical model of pipe network hydraulic characteristics has been established and a computer logic algorithm with virtual flow has been given. A direct-return pipe network with ten AHU branches is used as simulation calculation object, the pipe network supply-return water pressure difference is calculated, and also the temperature regulating valve opening and actual flow of each branch are calculated in the condition of different supply-return water pressure difference. The calculated results accord with the natural characteristics of high pressure difference unbalanced for direct-return pipe network. The calculation method can ensure calculation convergence. 相似文献
20.
The flow characteristics of multi-jes in the same direction and in great velocitydifference in combustion chamber were researched by the cold mould simulating test of self-designedlow- calorie value gas burner.The results showed that the large negative pressure region and back-flow region would be produced by the multi-annular jets with high-velocity air involve intensivelythe central low-velocity gas jet and by virtue of the small main air volume resulting by some extentcirculation of gas jet.These have the advantage of realising homogeneously mixing between air jetsand gas jet and combusting steadily. 相似文献