功率特作曲線
一、 功率組成

二、泵內(nèi)各種損失
葉輪內(nèi)的水力損失在很寬流量范圍內(nèi)不取扶于雜的工作狀態(tài)，在泵的整個流量范用內(nèi)可以認為是常數(shù)。因為葉輪水力效率r = Hk/Hr=(H+ -hx)/HT,所以可以求出hk=H+(1一x)。
在本章第一節(jié)中敘述了加x值的確定方法，而壓水室內(nèi)的損失hors已在本篇第三章第三節(jié)中進行了敘述。
功率Ny與容積損失即與經(jīng)過泵旋轉(zhuǎn)部件和固定部件之間的間隙泄渴量有關(guān)。在渣漿泵上只在泵的前密封處發(fā)生泄謝，因為在正常運行時不允許固液混合物經(jīng)過泵軸密封而泄漏，相反，通常對該處密封供應沖洗清水。
表征泵內(nèi)相對泄漏量的容積效率

于是可以得到
式中，泵內(nèi)的微圓量。
    泄漏量q(式中，為密封處的流量系數(shù))，與封密處的水力阻力和密封處揚程Hy有關(guān)。揚程Hy小于泵產(chǎn)生的揚程，它可以根據(jù)本篇第八章中所述的推薦方法確定，因為泄測量q與密封處的揚程有關(guān)，所以它首先是泵揚程的函數(shù)，容積損失是泵工作狀態(tài)的函數(shù)。當流量增大時時，容積損失減小，即最大容積損失發(fā)生在小流量工作狀態(tài)。

    容取效率是泵揚程的函數(shù)，其值一般根據(jù)比轉(zhuǎn)速n，按照最佳工作狀態(tài)的統(tǒng)計資料來選用。對于渣漿系，容積效率見表3-4-1.
    經(jīng)過密封處泄器的液體，與葉輪理論揚程有一定關(guān)系，因此消耗在密封處的功率由泵產(chǎn)生的理論揚程來確定，即為
    在繪制特性曲線N= f(Q)時，開始計算最佳工作狀態(tài)的功慮Ny.cn [根據(jù)式(3-4-6)]，同時根據(jù)式(3-4-5) 確定q，按照比轉(zhuǎn)速n,選取o。如上所述，比轉(zhuǎn)速對應于最佳工作狀態(tài)。對于其他狀態(tài)，功率Ny按照下式確定
    可以確信，消耗在泄漏方面的功率Ny,大體上與泵的有效功率成正比，因此如果Ny用泵有效功率的小數(shù)倍數(shù)(或者百分數(shù))表示，那么對所有相似的渣漿泵(n,= 常數(shù))，從理論上說它為常數(shù)。但是，實際上由于系數(shù)μ值很大，在小型泵上7較低，因為不能保持密封要素相似和在間隙(由于不能保證小型泵上很小同院)和縫隙中流動狀態(tài)相對應，而在大型泵上這些間隙可以采用較大尺寸。
    制動功率(參閱本篇第二章第五節(jié))為

從式(3-4-7）中可以看出，消耗在圓盤摩擦方面的功率與流量無關(guān)，即對同一臺泵來說，N=常數(shù)。圓盤相對摩擦損失功率為r.-N.xtNnm.因3 No隨著流量的增大面增大，所以ET.值隨之降低。
    根據(jù)C.C魯?shù)绿岱蛸Y料，對于n,=50的泵，系數(shù)cT:A≈0.26;對于n,=100的泵er.an0.065;而對于n,=200 的泵，eT.n=0.01. 即當n, 減小時，圓盤相對摩擦損失功率顯署增大，并且在比轉(zhuǎn)速n,<100時，增長特別大。
    在軸承，軸承密封和填料函中摩擦損失功率，通常遠小于其他形武損失功率，在泵的功率增大時，在功率平衡中它們的一部分急劇下降。因此，可以近似地采用NT.n約為泵在最佳工作狀態(tài)時功率的1%~3%，并且較小值對應于較大型的泵。

三、功率特性曲線繪制舉例
    繪制TyY3000/100 (3rM - 3M)型渣漿泵的特性曲線H=f(Q)和N=f(Q).
    已知，泵的轉(zhuǎn)速為750r/mm1葉輪參數(shù): D.-1.07m b,-0.23m， Rh=21'，z=3;壓水寬參數(shù):壓水室寬度B=0. 254m. h.. =0.295m hn=0.23m, F0.083，9o36.
確定與流量無關(guān)的參數(shù)
    計算理論揚程(采用本篇第二章第三節(jié)中所述的方法)。

求葉論和壓水室內(nèi)的水力損失并計算泵的揚程(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1~8)中。AF泡沫泵

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).