1. Physical properties of the sintered layer structure (4) The median, which is the particle size corresponding to half the weight of the mix. It is usually required to be used as a method of graph. Where G is the total mass of the sample, g t is the percentage of the mass of the sample of a certain size, and d i is the diameter of the sample of a certain size. People are most accustomed to using weighted arithmetic mean, which truly reflects objective laws. However, the weighted harmonic mean is mostly used in the study of bulk gas resistance, because the meaning of dp of some bulk gas mechanical equations is completely consistent with the concept of weighted and flat enthalpy, that is, the equation itself has been specified. Figure 1 shows that the relationship between the drag coefficient and the harmonic mean is more compatible than the arithmetic mean. The harmonic mean is closest to the fine-grained end, and the main factor affecting the permeability of the layer is the content of the fine-grained fraction. Therefore, using the harmonic mean can better reflect the macro regularity. It can be explained that in order to reduce the resistance of the layer, in addition to the general increase of the grain size, it is the most effective way to reduce the fine fraction in the mixture. [next] Common stacking methods (I), (IV) or a mixture of the two, (II) and (III) are not common in practice due to the complicated stacking conditions. According to the average of the 10 data of the pellets, the average measured value is 0.478, which is close to the theoretical calculation value of 0.4764 for the most loosely arranged simple cube. However, due to the difference in the degree of earthquake, it appears between 0.2559 and 0.4764. The average value is 0.3680. This is just another stable value of some measured data of 0.37. The sinter is more inclined to form a simple cube because its shape is not so regular. Arrangement, they also have two levels of stable values, generally between 0.5 and 0.53; under seismic conditions, they may be reduced to 0.43 to 0.46. From the figure, we can see: Its regularity: Changes in physical properties of the sinter layer The porosity ε is an important factor in determining the bed structure. It has a significant impact on the pressure drop of the gas through the layer, the effective thermal conductivity of the bed and the specific surface area. The main factors affecting ε are the shape of the particles, the particle size distribution, the specific surface roughness and the filling method, etc. These factors can be approximated as a combination of the shape factor Ф of the particles and the influence of ε. At the same time, the combustion of the fuel and the shrinkage of the material layer during the sintering process are very important for the change of ε. Petrol Engine Parts,Petrol Engine Piston,Car Engine Piston,Auto Engine Pistons KINCON POWER TECHNOLOGY CO.,LTD , https://www.kinconparts.com
When studying the airflow resistance of the sinter layer, the physical properties of the layer structure are involved, and its improvement has a great effect on reducing the gas resistance of the layer. These parameters mainly include the average diameter d of the pellet, the shape factor Ф and the porosity ε of the layer.
(I) Average diameter of pellets Sintering raw materials are composed of particles of different grain sizes. It is necessary to find a representative size to express their size. There are several methods: 
(2) Shape factor of the pellet The shape factor of the pellet refers to the ratio of the surface area of ​​the sphere with the same volume of the pellet and the actual surface area of ​​the pellet itself, ie Ф=S ball /S pellet (4)
However, the experiment pointed out that in addition to the shape of the pellet, its surface structure and roughness have a great influence, so in fact, the following formula should be expressed:
Ф=Ф G ×a
Where a———roughness coefficient;
Ф G ——— Geometric shape factor.
(3) Porosity of the material layer The possible accumulation form of the uniform material particles and the corresponding porosity, and refer to Figure 2.
The porosity of the two kinds of particle size ratios can be seen in the CF Furnas curve and the measured sinter curve, see Figure 3. [next]
1) The smaller d m /d k is , that is, the difference between the fine particles and the coarse particles is very far, and the porosity ε changes very steeply;
2) When the d m /d k ratio is fixed, when the coarse-grain dk mass accounts for 60-70% of the total amount, ε has a minimum value;
3) ε depends on the accumulation mode of coarse particles. Under the condition of non-vibrating accumulation, it is generally arranged in a simple cubic form. If the layer is vibrated, the porosity becomes small.
The variation of porosity in a variety of particle size combinations can be illustrated from the ternary diagram of Figure 4.
1) The interaction between the coarsest and the finest grades is dominant, and the law presented when the two-stage particle ratio is followed.
2) The increase of the intermediate-stage particles causes an increase in the porosity without changing the basic law of the two-stage particle ratio;
3) Roughly speaking, all the fractions can be divided into two levels according to the ratio of 67:33, and the tendency of the above two-stage ratio will still be exhibited.
The porosity of the layer is also affected by the size of the container. Figure 5 shows the effect of vessel diameter (D) and pellet diameter (d). To eliminate the edge effect of the container, at least make D / d = 10, preferably 20.
Gasochemistry in sintering process (1)