CN1089333A - Delivery lift adjustable centrifugal pump - Google Patents

Abstract

A kind of delivery lift adjustable centrifugal pump is made up of delivery chamber 1, impeller 2, seal ring 3, ring suction chamber 4, skeleton rubber shaft seal 5, axle 6 and carriage member 7 etc., and its structural feature is: 1. Fi 〉=F ₂, wherein Fi is that any cross section of fluid channel of delivery chamber is long-pending, F ₂For impeller outlet end cross section of fluid channel amasss; 2. arrange suitably many radial blades in the delivery chamber.Because the present invention changed existing voluted type delivery chamber into the impeller type delivery chamber, avoided the fluid energy loss that flow at high speed is brought in delivery chamber, and its lift can regulate, saved energy, improved efficient.

Description

Delivery lift adjustable centrifugal pump

The present invention relates to a kind of delivery lift adjustable centrifugal pump.

Centrifugal pump is a kind of universal machine, is widely used in the every field of national economy.But there are three distinct issues in existing centrifugal pump: the one, and its basic theory is imperfection very, does not have due theoretical direction effect.The 2nd, existing delivery chamber inner fluid energy loss is very big, makes centrifugal pump efficient not high.The 3rd, lift can not be regulated, and the energy waste that causes thus is considerable.

Just above problem is done detailed elaboration respectively below.

1. existing centrifugal pump basic theory and existing problems thereof

Existing centrifugal pump theory is under the hypothesis prerequisite of unlimited many unlimited slim vane, based on Euler's turbine equation (referring to document [1]).Gained centrifugal pump H=f(Q thus) equation is (referring to document [2])

H＝ (U ² ₂)/(g) - (U ₂)/(g) · (ctgβ ₂)/(F) （1）

In the formula, H-centrifugal pump unit weight fluid energy (, being commonly called as lift) hereinafter to be referred as fluid energy

The U-impeller circumferential speed,

β-blade angle,

The F-cross section of fluid channel is long-pending,

The Q-flow,

G-gravity accleration,

Footnote 2-represents the impeller outlet end.

But (1) error of formula and test curve is very big, and the various countries scholars have revised over one hundred year, and still effect is little so far.

The inventor thinks, because historical reasons, Euler's turbine equation lacks one 1/2nd Coriolis force square, has therefore done and has revised (seeing document [3] for details).

More worth proposition be that turbomachine should be divided into two Da Lou: the turbine that fluid can be converted to mechanical energy is called turbine, with mechanical energy be converted to fluid can turbine be called pump.The characteristics of motion of fluid in turbine and pump has principle distinction, and the hypothesis of much more unlimited unlimited slim vane do not meet the pump actual conditions, turbine equation also inapplicable pump both or after revising.

The inventor has derived the practical H=f(Q of centrifugal pump according to test curve) equation (seeing document [4] for details), its citation form is

$H=\frac{{V_{2c}}^2}{g}-K\·\frac{{(\frac{Q}{F_2}-[W{]}_{\mathrm{eq}})}^2}{2g}---\left(2\right)$

In the formula, V _{2 ℃}Circumference (tangentially) component of-impeller outlet end fluid absolute velocity; To the pump of determining, under certain rotating speed and medium, V _{2 ℃}=constant.

K-delivery chamber form factor is to delivery chamber and the medium K=constant of determining.

The equivalent whirling speed of [W] eq-decision odd-job condition fluid energy Ho; To the pump of determining, under certain rotating speed and medium, [W] eq=constant.

Analysis meter opinion centrifugal pump performance, during problems such as energy loss, (2) formula is very with practical value.

2. influence the deciding factor of voluted type centrifugal pump efficient.

We discuss the deciding factor that influence has voluted type (or stator formula) delivery chamber centrifugal pump efficient based on (2) formula.

For the simplification problem, outstanding principal contradiction; Suppose that centrifugal pump odd-job condition energy Ho equals ceiling capacity Hmax.So (2) formula becomes

H= (V _2℃ ²)/(g) -K· (Q ²)/(2gF ₂ ²) （3）

1) centrifugal pump specific discharge-specific energy equation

Order

H=(H)/(Hmax)-specific energy

So (3) formula becomes

h=1- (Kq ²)/2 （4）

2) centrifugal pump specific discharge-than fluid power equation

Centrifugal fluid power is

N＝HrQ （5）

In the formula, the N-fluid power,

R-fluid severe.

Order,

So, (5) formula is rewritten as

n=h·q=(1- (Kq ²)/2 )·q （6）

3) centrifugal pump specific discharge-than air horsepower equation

Because, but prime mover by impeller to unit weight fluid work Hmax=V ² _{2 ℃}/ g=constant, this energy are after impeller output, and how much irrelevant with prime mover loss is actually in delivery chamber.So to the impeller of determining, under uniform medium and certain rotating speed, centrifugal pump shaft power can be write as

Ne＝A+BQ （7）

In the formula, Ne-air horsepower,

A, B-are constant

Order,

Of course, (7) formula becomes

n _e＝a+bq （8）

In the formula, a, b-are respectively the constant of corresponding A, B.

Merit attention, in (8) formula, a represents that odd-job condition (q=0) compares air horsepower.B represents q-n _eThe slope of straight line.Different impellers, rotating speed and medium a, b are got different value.For comparing, get a=0.2 at this, b=0.25 with test curve shown in the accompanying drawing 2.Therefore, (8) formula is rewritten as

n _e＝0.2+0.25q （9）

4) centrifugal pump specific discharge-efficiency equation

Centrifugal pump efficient is

$\mathrm{\η}=\frac{n}{n_e}=\frac{(1-\frac{{\mathrm{kq}}^2}{2})\·q}{0.2+0.25q}---\left(10\right)$

Should be noted that in (4), (9), (10) formula, except that independent variable and dependent variable, to have only a unknown number K.Therefore, use (4), (9), (10) formula, corresponding different K values is drawn centrifugal former q-h, q-n _e, q-η curve such as accompanying drawing 1.Accompanying drawing 2 influences the test curve (document of getting [2]) of performance of centrifugal pump for explanation volute chamber throat opening area.

Obviously, in accompanying drawing 1, Fig. 2, the shape of corresponding each curve is very close.This shows that above formula has more objectively reflected the characteristics of motion of fluid in centrifugal pump.

So far as can be seen, to the impeller of determining, under certain rotating speed and medium, delivery chamber form factor K, decision peak efficiency operating mode specific discharge q _ηK is bigger, q _ηLittler; Meanwhile, delivery chamber inner fluid energy loss is also bigger, highest efficiency eta _MaxJust lower.When K when 14 become 100, η _MaxReduce to 25% from 58%.Vice versa.

We can also further count opinion, and K is bigger, q _ηLittler, η _MaxWhat is again the low essence that just heals? for this reason, second of (3) formula equation right-hand member is rewritten as

K (Q ²)/(2gF ² ₂) =ξ· ((K′V _Q) ²)/(2g) （11）

In the formula, V _Q=(Q)/(F ₂)-impeller outlet is held equal flow speed level with both hands.

K=ξ (K ') ², wherein ξ-be called energy-loss factor is relevant with runner roughness and fluid viscosity etc.; K '-be called actual flow velocity coefficient.

Again (10) formula is rewritten as

So, can know that by (11) formula to delivery chamber structure, material, technology and the medium determined, ξ can be considered invariant.Therefore, making K become big unique factor is exactly K '.

Twoly can know that because K is very big, q-η curve becomes very steep, q by (12) formula _ηBecome very for a short time, the denominator in (12) formula is just very big, η _MaxInevitable very low.

So conclusion, the deciding factor that influences voluted type centrifugal pump efficient is the delivery chamber inner fluid loss of energy, it is caused by delivery chamber inner fluid flow at high speed.

Inference if can cancel the bigger existing delivery chamber of K value, and adopts the very little novel delivery chamber of K value, will improve centrifugal pump efficient significantly so.

3. the classification of centrifugal pump and energy adjustment problem thereof

By purposes centrifugal pump is divided into transfer pump and jet pump two classes.So-called transfer pump means that this pump overcomes pipe network (abbreviation of the suction line and the pipeline that spues) resistance and geometric height by the fluid energy in the delivery chamber, transports fluid into a certain distant place, or a certain eminence.The most of centrifugal pumps such as conveying that are used for farmland discharging-irrigating, urban water supply and sewerage, all kinds of petroleum chemicals all belong to transfer pump.So-called jet pump means that this pump is with the fluid energy in the delivery chamber, and mainly the form with kinetic energy ejects.Be used for centrifugal pumps such as fire-fighting, high pressure water injection and all belong to jet pump.

All centrifugal pumps all have conveying function, but whether centrifugal pump has ejection function, depend on the shape of delivery chamber.Existing voluted type (or the stator formula) delivery chamber of etc.ing all has ejection function, and therefore having centrifugal pump now both can be as transfer pump, again can be as jet pump.

The distinguishing feature that delivery chamber has ejection function is can not be regulated by the fluid energy of delivery chamber output.After delivery chamber outlet valve one amount is opened, unit weight fluid energy in the delivery chamber, except that the loss part, all output.

As everybody knows, in the practical application of centrifugal pump, the resistance of pipe network can not be estimated very accurately.In addition, pipe network itself also may change sometimes.Therefore, selecting the principle of centrifugal pump for use is to satisfy the required maximum fluid energy of pipe network.

Because the output fluid energy of existing centrifugal pump can not be regulated, so be difficult to avoid occurring following situation: the fluid energy H of centrifugal pump input pipe network is greater than the fluid energy H ' of pipe network actual demand.At this moment, sheerly waste of the rQ part △ N=(H-H ' in the centrifugal pump fluid power).Extensively according to the application of centrifugal pump, more than the operating number, be not difficult to infer that the energy waste that causes thus is appreciable.

4. the energy loss of centrifugal pump

The energy loss of centrifugal pump can be divided into four classes: common mechanical frictional loss, disc friction, volumetric loss and the fluid loss of energy.

The notion of first three items energy loss is with the same usually.Only, usually, with common mechanical frictional loss and disc friction general designation mechanical friction loss.Separately be because in the total energy loss of delivery lift adjustable centrifugal pump, the shared ratio of disc friction seems very outstanding, is necessary to draw attention with them herein.

About the fluid loss of energy, the inventor thinks that its final form of expression is a heat energy.Mainly cause, with square being directly proportional of flow velocity by flowage friction.Flow and comprise along Cheng Liudong and vortex motion; The former is with V _Q=(Q)/(F) (F is an actual internal area) represent; Under the situations such as the latter undergos mutation at actual internal area, the change of flow velocity direction, occur when collision between fluid and the fluid, between fluid and the tube wall and flow velocity redistribution.

Centrifugal pump inner fluid-with the clear water is an example, is incompressible, and the runner tube wall also can be regarded absolute rigidity as.Therefore, when bumping, if adopt an effective measure the elimination vortex motion, fluid dynamic energy can be converted into the pressure heat energy that energy-collision produced fully and ignores so.

The purpose of this invention is to provide a kind of delivery lift adjustable centrifugal pump, it can avoid the fluid energy loss that flow at high speed is brought in delivery chamber, and its lift can regulate, thereby conserve energy is raised the efficiency.

For achieving the above object, concrete solution of the present invention is: delivery lift adjustable centrifugal pump of the present invention is made up of delivery chamber 1, impeller 2, seal ring 3, annulus suction chamber 4, skeleton rubber shaft seal 5, axle 6 and carriage member 7 etc.The characteristics of its structure are: 1. Fi 〉=F2, and wherein Fi is that any cross section of fluid channel of delivery chamber is long-pending, F2 is that impeller outlet end cross section of fluid channel is long-pending, 2. arranges suitably many radial blades in the delivery chamber.

Because the present invention has changed existing voluted type delivery chamber into the impeller type delivery chamber, makes when fluid enters delivery chamber that its rotation function is converted into the pressure energy, fluid only is V in delivery chamber _Q=Q/Fi(is the Q-flow wherein, and any cross section of fluid channel of Fi-delivery chamber is long-pending) along Cheng Liudong, and vortex motion and flow at high speed do not occur, thereby can increase substantially efficient, its peak efficiency can be brought up to more than the 85-90% from about present 60-70%.The fluid energy of the pipe network of delivery chamber input simultaneously can be regulated by the delivery chamber outlet valve according to the actual demand of pipe network, makes rate of energy always be in rational state, and the economic benefit that this energy saving brings is very considerable.

The waterpower design of two parts-impellers of the key of delivery lift adjustable centrifugal pump of the present invention and delivery chamber becomes very simple, and one group of design-calculated empirical correlation (back detailed description) arranged, reducing in large quantities, even do not need the situation of hydraulic model test, can realize standardization, seriation and generalization.

Fig. 1 voluted type delivery chamber form factor influences the calculated curve of performance of centrifugal pump.

Fig. 2 voluted type delivery chamber throat opening area influences the test curve of performance of centrifugal pump.

Fig. 3 delivery lift adjustable centrifugal pump structural drawing.

Wherein: 1. 6. 7. carriage members of delivery chamber 2. impellers, 3. seal ring 4. ring suction chambers, 5. skeleton rubber shaft seals

The estimated performance curve of Fig. 4 delivery lift adjustable centrifugal pump.

Characteristic to delivery lift adjustable centrifugal pump of the present invention is described in further detail below:

1. delivery lift adjustable centrifugal pump characteristic curve

We export the operating mode of maximum fluid energy with delivery chamber, are called design conditions, and its peak efficiency operating mode is called declared working condition; The operating mode of output fluid energy is called the adjusting operating mode.

(1) design conditions characteristic curve

A. flow-head curve

Available following empirical correlation is calculated

H=f (Q)=H _Tell+ H _Inhale=(U ₂ ²)/(2g)=H _Max=constant (13)

In the formula, H _Tell, H _Inhale-be respectively spue, the fluid energy in the suction line.

B. flow-shaft power curve

Formula is identical with (7) formula, promptly

Ne＝A+BQ （14）

In the formula, A, the B-pump to determining at certain rotating speed, is constant under medium and the operating mode determined.

C. flow-efficiency curve

η＝ (HrQ)/(102Ne) ＝ (HrQ)/(102（A+BQ）) （15）

Each calculation of parameter unit is in the formula, H-m, r-kg/m ³, Q-m ³/ s, Ne-kw.

(2) regulate the working characteristics curve

A. flow-head curve

H '=f(Q)=H ' _Tell+ H ' _Inhale=(H _Max-H ' _Inhale) (F _x/ F ₂) ²+ H ' _Inhale(16)

In the formula, Fx-delivery chamber outlet valve open area.

B. flow-shaft power curve

Ne′＝A+B′Q （17）

In the formula, B '=constant, but notice that B ' is not equal to design conditions B.

C. flow-efficiency curve

η＝ (H′rQ)/(102（A+B′-Q）) （18）

More than each characteristic curve as shown in Figure 4.Solid line is design conditions, and dotted line is for regulating operating mode.

Be easy to find out, Q-η, Q-η ' curve does not have extreme value, send to show, and under same H or the H ', Q is bigger, η _Max(η ' _Max) higher; In other words, specific speed is higher, and efficient is higher.

Regulating operating mode, H ' reduces, and Q can increase.But, when H ' too reduces, should not cross high restriction owing to increase the flow velocity that Q is subjected in cavitation conditions, the pipe network, thus original machine power can not give full play to, efficient will descend.

2. delivery lift adjustable centrifugal pump specific speed

Existing theoretical central centrifugal pump specific speed can only be calculated with performance parameter.The delivery lift adjustable centrifugal pump specific speed can not only be calculated with performance parameter, and can calculate with design parameter and energy consumption parameter, and method is as follows:

(1) specific speed of representing with performance parameter

With common the same (referring to document [2])

$n_s=\frac{3.65\·n\·\sqrt{Q}}{H^{3/4}}---\left(19\right)$

Unit of account, n-rpm, Q-m ³/ s, H-m.

(2) specific speed of representing with design parameter (declared working condition)

n _s=1151.26 √ go into b (20)

In the formula,

Go into=(Q)/(F ₂U ₂)-flow speed coefficient

B=(B ')/(D ₂)-impeller outlet end width of flow path coefficient.

Wherein, B ' is an impeller outlet end runner equivalent width, represent with following formula,

B′＝B(1- (S)/(πD ₂) ) （21）

Wherein, B is an impeller outlet end width of flow path, the invalid circumference of impeller length of S for causing owing to vane thickness or blocking portion runner.

Clearly, (10) formula shows, and is constant as long as b. goes into, and specific speed so is to D arbitrarily ₂, n is constant.

(3) with the specific speed (declared working condition) of energy consumption parametric representation

${\mathrm{\η}}_s=27.25\sqrt{\frac{{\mathrm{\η}}_{\max }}{f}}---\left(22\right)$

In the formula, η _Max-declared working condition efficient.

F=(△ Nf)/(Ne)-disc friction coefficient.Wherein △ Nf is a disc friction power, can estimate (referring to document [2]) by following formula,

△Nf＝0.126×10 ^-9·rn ³D ⁵ ₂（23）

Clean waterpump is estimated with following formula,

△Nf＝0.126×10 ^-6n ³D ⁵ ₂（24）

F is to η _MaxInfluence press following formula estimation,

f＝（1-η _max）·ψ （25）

Wherein, big value is got to loaw specific speed pump in ψ=0.2～0.9.

(22) formula clearly illustrates that, delivery lift adjustable centrifugal pump efficient and disk friction coefficient and specific speed are closely related.We wish η _MaxHeal height better, but improve η _Max, must reduce f, increase η _STherefore, propose rationally to choose the specific speed problem.For example, a certain middle specific speed delivery lift adjustable centrifugal pump desires to reach η _Max=0.87, corresponding f=(1-0.87) * 0.4=0.052, it is η that above substitution (22) formula is got reasonable specific speed _s=110.

3. the use problem of relevant delivery lift adjustable centrifugal pump

(1) delivery lift adjustable centrifugal pump amasss the pipeline cross section of fluid channel that spues specific (special) requirements.If pump is worked under a certain definite operating mode, corresponding delivery chamber outlet valve open area is Fx, and flow velocity is Vx=Q/Fx herein; The main pipe any place actual internal area Fgi that spues so must satisfy the flow velocity Vgi(=Q/Fgi of this place)≤Vx; Branch pipe(tube) any place cross section of fluid channel amasss F ' _Gi, must satisfy the flow velocity V ' of this place _Gi(=Q '/F ' _Gi)≤Vx.

(2) ejection function of centrifugal pump delivery chamber and delivery lift adjustable function oppose, and gain in one thing and lose in another, and the two can not have concurrently.Therefore, delivery lift adjustable centrifugal pump does not have ejection function, can only be as transfer pump.

But if add the common stator formula centrifugal pump of one-level after the delivery lift adjustable centrifugal pump, so this combined multi-stage pump just has ejection function.

Embodiment:

Press the organization plan shown in the accompanying drawing 3, in the most preferred embodiment of the present invention, its impeller blade is a straight radial blade, i.e. impeller blade turnover bicker is 90 °, and other parameters selection is as follows:

Impeller diameter D ₂=0.16m, number of blade Z=8, impeller outlet end width of flow path coefficient b=0.056, flow speed coefficient go into=and 0.146, the pump bore=suction bore=0.08m(3 ") that spues

Power of motor Ne=5.5kw, rotation speed n=2900rpm

Then corresponding performance parameter is

H＝30m，Q＝0.0159m ³/s＝57m ³/h η _max＝0.85 n _s＝104

Reference

(1). theoretical mechanics study course, volume two first fascicle

Strong this base work in Lip river, People's Education Publishing House 1962.

(2). centrifugal pump base of design, centrifugal pump base of design are write group and are compiled, China Machine Press, 1974.

(3). " trying to make a comment the reason that the Euler's turbine equation error is very big ", Lai Xuanming, 92 years annual meeting collections of thesis of Chinese Society of Engineering Thermophysics, the 6th fascicle (fluid machinery).

(4) " explore the practical H=f(Q of centrifugal pump) equation ", Lai Xuanming, " forestry machinery " 1987 the 4th phases.

Claims (2)

1, a kind of delivery lift adjustable centrifugal pump is made up of delivery chamber 1, impeller 2, seal ring 3, ring suction chamber 4, skeleton rubber shaft seal 5, axle 6 and carriage member 7 etc., it is characterized in that:

1) Fi 〉=F ₂, wherein Fi is that any cross section of fluid channel of delivery chamber is long-pending, F ₂For impeller outlet end cross section of fluid channel amasss.

2) arrange suitably many radial blades in the delivery chamber.

2, adjustable Yang Cheng centrifugal pump according to claim 1, it is characterized in that: the radial blade of delivery chamber is a straight radial blade.

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