英语PPT演讲稿

2020-03-01 18:36:06 来源：范文大全收藏下载本文

CAN you hear me all right? I am glad to have the opportunity of making this presentation.I shall be speaking today about The Model Formulation of this article.DO you everyone have printed this article ? OK,good! NOW, before we start our presentation, let\'s answer some questions.Question 1: What reactions can we find when carbon is

burning in the air？ Anyone? OK! These there reactions Qestions 2: Can you translate it? Yech, I can\'t either… But, we can underline the Subject and predicate.

Who wants to try?? ok...ignore! Next! Second part is about what we\'ve known about the model fomulation.we know Kinetics models for the combustion of carbon particles are intended to reproduce major features of the proce without having to account for underlying complexities.

2.The kinetic parameters of these models must be determined experimentally.3.These large particles burn nearly as shrinking spheres and diffusion tends to control the burning rate rather than chemical kinetics. Third part is What THEY have known.THEY are the scientists who have studied the model.Ragland and Yang [7] measured the time evolution of the ma of captive millimeter sized particles for different gas temperatures, gas velocities, oxygen concentrations, particle sizes, and coal types. They found that the char burning rate normalized with the initial ma of the particle（最初的质量相等） is insensitive to gas temperature in the range 900 to 1200 K, increases slightly with gas velocity and markedly with oxygen concentration, and decreases with particle size.

Matsui and coworkers [8] experimentally studied the combustion of a heated carbon plate subjected to a stagnation (停滞的) point flow of air.

They determined

the activation energy of the heterogeneous carbon oxidation reaction and the effect of the oxidation of CO

in the gas, which interferes with (干扰) the heterogeneous reaction through the consumption of O2 Adomeit et al.[9] numerically solved the stagnation point flow problem and were able to match Matsui’s data by taking into account the heterogeneous reactions of O2 and CO2 with C and different approxi- mations to the gas-phase kinetics Blake and Libby [10] quantified the enhancement (增强)of the burning rate of a char particle due to its motion. Musarra

et al.[11] carried out numerical computations (数值计算) using two competing reactions to model pyrolysis, and the heterogeneous reactions of O2 and CO2 with C to model char gasification. little effect of the oxidation of CO during the char gasification period. SO This paper extends the analysis of the flow around a moving char particle, removing some of the simplifying aumptions that have been made in previous works and covering a larger range of particle sizes and gas conditions.

Now,I\'m going to be speaking about these there reactions : The rates of the heterogeneous reactions are the following.

(ma of carbon consumed per unit surface area and per unit time)

AND the gas-phase reaction is aumed to be infinitely fast and not taken into account.

In general, Ts and qs are not uniform on the surface, and the relation between them is not local or quasi-stationary.

However, if the conduction time in the solid, is short compared with the combustion time of the particle and the characteristic time of variation of the ambient conditions seen by the particle, then Ts is nearly uniform except is an initial period of order tc.

In these conditions,

the problem can be solved for a given value of Ts

These are the ma and energy equations which are used to determine the surface distribution of qs.,and we can obtain the relation between a and m ,and between ts and qs.

these are the surface-averaged values.

NOW, let\'s have a conclusion: Independent variables

the oxygen and the carbon dioxide ma

fractions of the gas ——YCO2 velocity——U

The surface temperature——Ts Radius——a

And dependent variable——the time evolution of the ma m