根据詹德曼的试验资料，在泵输送砾石混合物时，得到后盖板最大磨损量(82) 和前盖板最大磨损量(8、) (按照磨损深度)之出8218与因子JC1gD.之间的关系，见表3 -7-5。
Examples of the influence of slurry pump working condition on blade wear
Now the working state of the pump, i. e. speed C, is studied. The effect of uneven wear on the inlet edge of the blade is illustrated. It is assumed that the flow rate of the optimum state is Q=4000m3/h; the composition of solid liquid mixture is composed of coarse sand and gravel, and the impeller inlet diameter is C=0.5 D. =600mm; solid-liquid mixture at impeller inlet velocity co=3.93m/s.
The parameters of wear and tear of the inlet edge of the blade are determined. The wear coefficient of impeller blade inlet is K=1.18., which indicates that the maximum linear wear at the inlet side (according to the enumeration data) is 18% larger than the average wear volume, that is, the blade wears fairly uniformly along the width direction. Increase the flow rate by 40%, and the entry speed is co=5.5m/s. The wear coefficient of the blade inlet is K=1.34, and the maximum linear wear of the blade inlet is 34% larger than that of the average wear.
As a result, the increase of flow rate will lead to the increase of non-uniform degree of wear at the inlet edge of the blade, and the wear of the inlet side will be more uniform when the pump works at low flow rate.
The head-on drag coefficient C can be calculated using the recommended values for hydraulic conveying. Table 3-7-4 shows the coefficient C values for different particle sizes in mixtures.
In addition to the blades, the wear of the front and rear cover plates of impellers is quite serious, and their surface wear distribution is very uneven, and there are local deep wear pits. Compared with the layout of the blades, the location of these pits is strictly limited. Local wear is the result of the decurrent produced by the flow around the inlet of the blade. In this case, the same particle may contact the worn surface more than once.
The diversion of solid-liquid mixture flow at impeller inlet is the reason for the increase of solids concentration at the rear cover plate and the decrease of concentration at the front cover plate. With the increase of pump flow rate, the non-uniform distribution of solid particles along the blade width increases and the number of particles at the back cover plate increases, which will lead to increased local wear. At the same time, the concentration of solid particles at the front cover decreases correspondingly, that is to say, the wear of the front cover decreases.
Parametric store VC/gD. It can be used as a criterion for evaluating the relative wear strength of front and rear cover plates.
According to Jandman's test data, the relationship between the maximum wear volume of the rear cover plate (82) and the maximum wear volume (8) of the front cover (8) and the factor JC1gD. is shown in Table 3 -7-5.
The wear of the cover does not affect the performance of the pump. When perforation occurs, the guard plate will be damaged.
From the above data, it can be seen that the front cover wears faster than the back cover when the JC/gDa value is small, that is, in the condition of small flow rate of the pump. On the contrary, when the parameter VC/gD. has a small value, the wear of the rear cover plate is the first cause. It should be noted that the wear of the rear cover plate of impeller is 1-2 times faster than that of the front cover plate in the larger flow rate state, while in the smaller flow rate state, the damage of the front cover is earlier than that of the back cover plate, which is due to the stronger discharge caused by the larger angle of attack of the back cover plate.