從式(3-4-7）中可以看出

求葉論和壓水室內(nèi)的水力損失并計(jì)算泵的揚(yáng)程(參圓本章第二節(jié))

所確定一些參教值匯集在表3-4-2(序號(hào)1~8)中

Power Special Curve

I. Power Composition

II. Various Losses in Pumps

The hydraulic loss in the impeller is not supported by miscellaneous working conditions in a wide flow range, and can be considered as a constant in the whole flow specification of the pump. Because the hydraulic efficiency of impeller r = Hk / Hr= (H+ - hx) / HT, it can be calculated that HK = H+ (1x).

In the first section of this chapter, the method of determining the added x value is described, and the loss hors in the pressurized water chamber is described in the third section of the third chapter of this chapter.

Power Ny and volume loss are related to the amount of gap Thirst Relief between the rotating parts and the fixed parts of the pump. Leakage occurs only at the front seal of the slurry pump, because the solid-liquid mixture is not allowed to leak through the seal of the pump shaft in normal operation. On the contrary, the seal supply is usually flushed clean water.

Volumetric efficiency for characterizing relative leakage in pumps

So you can get it.

In the model, the micro-circle in the pump.

Leakage Q (in the formula, the flow coefficient at the seal) is related to the hydraulic resistance at the seal and the head Hy at the seal. The head Hy is smaller than the pump's head. It can be determined according to the recommended method described in Chapter 8. Because the leakage measurement q is related to the head of the seal, it is first a function of the pump's head, and the volume loss is a function of the pump's working state. When the flow rate increases, the volume loss decreases, that is to say, the maximum volume loss occurs in the small flow state.

Tolerance efficiency is a function of pump head. Its value is usually selected according to the specific speed n and the statistical data of the best working state. For slurry systems, the volumetric efficiency is shown in Table 3-4-1.

The liquid passing through the discharger at the sealing position has a certain relationship with the theoretical head of the impeller, so the power consumed at the sealing position is determined by the theoretical head produced by the pump.

When drawing characteristic curve N= f(Q), the work factor Ny.cn of optimum working condition is calculated [according to formula (3-4-6)]. At the same time, q is determined according to formula (3-4-5). O is selected according to specific speed n. As mentioned above, the specific speed corresponds to the optimal working state.  For other states, the power Ny is determined according to the following formula

It is believed that the power Ny consumed in leakage is generally proportional to the effective power of the pump, so if Ny is expressed in decimal multiples (or percentages) of the effective power of the pump, it is theoretically constant for all similar slurry pumps (n, = constant). However, in fact, because the coefficient of Mu is very large, 7 is lower on the small pump, because it can not maintain the similarity of sealing elements and correspond to the flow state in the gap (because it can not guarantee the small courtyard on the small pump) and the gap, while on the large pump, these clearances can adopt larger size.

Braking power (see Chapter 2, Section 5 of this chapter)

It can be seen from formula (3-4-7) that the power consumed in disc friction has nothing to do with the flow rate, that is, for the same pump, N = constant. The relative friction loss power of the disc is r. -N. xtNnm. The ET. value of the disc decreases as the flow rate increases.

According to C.C Rudetiv data, for n, = 50 pumps, the coefficient cT: A_0.26; for n, = 100 pumps, er.an 0.065; and for n, = 200 pumps, eT.n = 0.01. That is to say, when n, decreases, the relative friction loss power of the disc increases obviously, and the increase is especially great at the specific speed n, < 100.

Friction loss power in bearings, bearing seals and stuffing boxes is usually much less than that in other forms. When the power of pumps increases, a part of them decreases sharply in the power balance. Therefore, NT. n can be approximated to 1%~3% of the power of the pump in the optimal working condition, and the smaller value corresponds to the larger pump.

3. Examples of Drawing Power Characteristic Curve

Draw the characteristic curves H=f(Q) and N=f(Q) of TyY3000/100(3rM-3M) slurry pump.

It is known that the pump speed is 750r/mm1 impeller parameters: D. -1.07mb, -0.23m, Rh=21', z=3; pressure water width parameters: pressure chamber width B=0.254m. h. = 0.295mhn=0.23m, F0.083, 9o36.

Determining flow-independent parameters

Calculate the theoretical head (using the method described in Section 3 of Chapter II of this chapter).

Seek the hydraulic loss in the blade theory and the pressurized water chamber and calculate the pump head (see Section 2 of this chapter).

Some reference values determined are aggregated in Table 3-4-2 (serial numbers 1-8).