CN108229027B - Method for improving angle modulation precision and reliable durability of mechanical full-adjusting mechanism of water pump - Google Patents
Method for improving angle modulation precision and reliable durability of mechanical full-adjusting mechanism of water pump Download PDFInfo
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Abstract
A method for improving the angle modulation precision and the reliable durability of a mechanical full-adjusting mechanism of a water pump belongs to the technical field of precision and reliable durability of power mechanical equipment, and aims to reduce the stress deformation of an adjusting rod and the adjusting error of a blade, reduce the separating bearing stress of the adjusting mechanism and improve the reliable durability on the premise of not changing the hydraulic performance of an impeller; the method specifically comprises the steps of optimizing the position of a water pump blade shaft under the full operation condition based on CFD-computational fluid dynamics, increasing the length of a crank arm of an adjusting mechanism under the condition that the space in an impeller hub is allowed, selecting a small-inclination-angle separation thrust roller bearing and the like; through the comparison of the improved front and rear adjusting force of the adjusting mechanism and the bearing force and service life of the separating shaft, the invention can reduce the blade adjusting force of the water pump under the full operating condition by about 60 percent averagely, reduce the bearing force of the separating shaft by 68 percent averagely and prolong the service life by about 30 times by calculation.
Description
Technical Field
The invention belongs to the technical field of precision and reliable durability of power mechanical equipment, and relates to a method for improving the angle modulation precision and reliable durability of a mechanical full-adjusting mechanism of a water pump, in particular to a method for reducing the blade adjusting force and the bearing stress of the adjusting mechanism and improving the angle modulation precision and reliable durability of the mechanical full-adjusting mechanism of the water pump by optimizing the position of a blade shaft, increasing the length of a rotating arm of the adjusting mechanism, applying a small-inclination-angle thrust bearing to the adjusting mechanism and the like aiming at the full-operation working conditions of different lifts and different blade angles of the water pump.
Background
The large and medium axial-flow pump and the guide vane type mixed-flow pump carry out blade angle adjustment by arranging a blade full-adjusting mechanism, thereby realizing variable-angle optimized operation, adjusting flow and saving operation cost; the angle of the blade is adjusted to be small, the starting and the stopping are carried out, and the reliability and the durability of the unit are improved. Calculation research shows that the regulating mechanism is mainly affected by the water moment, centrifugal moment and friction moment of the blades. At present, the position of a mechanical full-regulating mechanism blade shaft is unreasonable, the blade water moment of a water pump under the full-operation working condition cannot be considered, the regulating mechanism is unreasonable in design, a separating thrust bearing is unreasonable to select for the regulating mechanism, so that the blade water moment is large, and the regulating rod of the regulating mechanism bears overlarge pressure for most of time, so that on one hand, the lower separating thrust bearing with small design load is large in bearing force and exceeds the allowable load, and the lower separating thrust bearing is extremely easy to damage; on the other hand, the adjusting rod has large compression deformation and large angle adjustment error, and the compression bow deformation of the adjusting rod is easy to cause jamming, stiffness, eccentric wear and even damage at the hollow water pump shaft, the motor shaft guide shaft sleeve and the lower separation thrust bearing. Therefore, on the premise of ensuring or not changing the hydraulic performance of the impeller, a mechanical full blade adjusting mechanism with small blade adjusting force and small separating bearing force under the full operation working conditions of different lifts and different blade angles is required to be designed so as to improve the angle adjusting precision of the adjusting mechanism and the reliability and durability of the separating bearing.
Disclosure of Invention
Aiming at the problems of large water moment, large adjusting force, large angle adjusting error and poor reliability and durability of a release bearing of the large and medium-sized mechanical full-adjustment axial flow pump and the guide vane type mixed flow pump, the invention provides a method for improving the angle adjusting precision and the reliability and the durability of a mechanical full-adjustment mechanism of a water pump.
The technical scheme of the invention is as follows: the method for improving the angle modulation precision and the reliability and the durability of the mechanical full-adjusting mechanism of the water pump comprises the following steps:
A. optimizing the position of the blade shaft based on the full operation condition:
the factors constituting the regulating force or the vane torque of the fully-regulated water pump include a vane water moment, a vane centrifugal moment and a vane friction moment, which are generally equal to 90%, 1% and 9%, respectively, and the ratio of the vane water moment is the largest. The blade water moment is related to the working condition of the water pump and the position of the blade shaft. Through optimizing blade axle position, reduce the blade water moment of water pump full operating mode, can reduce the regulating force by a wide margin.
1. Determining the calculation condition of the full-operation condition range:
in the range of the operating lift of the water pump, m lifts at equal intervals are selected, including the highest lift and the lowest lift, and for each lift of the m lifts, in the range of the operating blade angle of the water pump, n angles including the maximum angle and the minimum angle are selected according to a certain interval by the blade angle, so that the total m multiplied by n calculation working conditions are obtained.
Calculating the water moment of the blade under m × n calculation conditions:
performing numerical simulation on the flow field in M × n calculation conditions of the water pump by using fluid calculation software to obtain the water moment M of the impeller bladeshAs in table 1, the water moment adjusts the blades to be positive in the wide angle direction.
TABLE 1 vane water moment M of each calculation condition of water pump before optimizing vane shaft positionh(Unit: N. m)
3. Determining the position of the optimal blade shaft under the full-operation condition:
the distance from the blade water pressure resultant force action line to the current blade shaft on the middle calculation section between the hub and the rim of the blade under each calculation condition is as follows:
in the formula: l is the distance from the resultant action line of the water pressure of the blade to the current blade shaft; mhThe blade water moment is directly obtained by calculation of fluid calculation software; fhAnd calculating by using fluid calculation software to respectively obtain the axial water pressure, the circumferential water pressure and the radial water pressure of the blade, and synthesizing to obtain the resultant water pressure.
On the calculation section of the blade, dividing an area s between two blade water pressure resultant force action lines farthest away in all m multiplied by n calculation working conditions into k equal parts, and respectively setting blade shafts 1, 2, …, k-1 and k at each equal part; calculating the blade water moment with the maximum absolute value in m multiplied by n working conditions of the water pump at the set k blade shaft positions, and determining two adjacent set blade shafts O for positive and negative conversion of the maximum hydraulic moment of the blades1-O1、O2-O2Location.
The method adopts 0.618 golden section method to find and determine the position of the blade shaft, so that the water pump is under all working conditionsThe maximum hydraulic moment of the blades is the smallest. Is provided for the blade shaft O1-O1The maximum water torque of the blade shaft O is positive2-O2Is negative, then the self-O on the cross section is calculated in the blade1-O1Axial direction O2-O2The blade shaft O is set at the position of 0.618s/k distance from the shaft3-O3For blade axis O3-O3The maximum water torque of the blades of the water pump under all working conditions; if for the blade shaft O3-O3The maximum water torque of the water pump all-working-condition blade is positive, which indicates that the optimal blade shaft is positioned at O3-O3Shaft and O2-O2Between the shafts, continue from O3-O3Axial direction O2-O2The shaft takes a distance of 0.618 (1-0.618) s/k, where the vane shaft O is set4-O4(ii) a If for the blade shaft O3-O3When the maximum water torque of the blades of the water pump under all working conditions is negative, the water pump continues to operate from the position O1-O1Axial direction O3-O3The axes are taken at a distance of 0.618 x 0.618s/k, where the blade axis O is determined4-O4… …, and so on, until the distance between two adjacent blade axes of the last approximation is small enough to satisfy equation (2).
Δs≤0.001m (2)
The blade shaft at the position is the blade shaft at the optimal position, and the maximum hydraulic moment of the blades under all working conditions of the water pump can be ensured to be minimum. After the position of the blade shaft is optimized, M multiplied by n working condition blade water moments M 'of the water pump'hAs shown in table 2.
B. Increase adjustment mechanism rocking arm length:
1. blade torque calculation:
blade torque M as described in step AbIncluding blade water moment, blade centrifugal moment and blade frictionMoment of friction, water moment M of bladeshCalculated with fluid calculation software.
When the impeller rotates, centrifugal force acts on each tiny mass on the blade, the action line of the centrifugal force is not superposed with or intersected with the blade shaft to generate moment to the blade shaft, and the resultant of the centrifugal force of all the masses of the blade to the moment of the blade shaft is the centrifugal moment M of the bladec。
The centrifugal force generated by any infinitesimal mass of the blade is as follows:
dF＝ρ(drdzrdα)rω2 (3)
in the formula: dF is the centrifugal force of the micro-mass of the blade; ρ -blade material density; omega-impeller angular velocity; r is the radius from the vane infinitesimal to the axis of the impeller; alpha is the included angle between the projection of the radius of the vane infinitesimal and the radius of the water inlet edge of the vane on the horizontal plane on a certain calculated cylindrical section; z is the height difference between the vane micro element and the vane axis in the z direction on the calculation cylinder section.
Integrating the moment of the blade shaft by all the infinitesimal centrifugal force of a single blade to obtain the centrifugal moment of the single blade:
in the formula: mc-single blade centrifugal moment; rh-blade hub radius; r-radius at the blade rim; z is a radical ofu-calculating the difference in height of the profile of the airfoil in the section of the blade from the blade axis; z is a radical ofdCalculating the height difference from the lower profile of the airfoil on the section to the axis of the blade by the blade; alpha is alphamCalculating the central angle of the airfoil profile projected in the horizontal plane between the water inlet edge and the water outlet edge on the blade section; integrating the formula (4) by using a numerical method, and calculating to obtain the angle alpha of a single blade1，α2，…，αn-1，αnThe centrifugal moment of (a).
When the angle of the water pump blade is adjusted, the friction torque of a sealing rubber between the blade and a hub needs to be overcome, and the calculation formula of the sliding friction torque of the single blade seal is as follows:
Mf＝FfRs＝μpSRs (5)
in the formula: mf-blade friction torque; ff-blade root friction; rs-blade root seal friction face radius; mu-coefficient of friction between the blade root and the rubber seal; p-unit area sealing pressure; s-sealing area. The blade friction torque is irrelevant to the working condition of the water pump.
During blade adjustment, the torque M of a single bladebComprises the following steps:
Mb＝±Mh±Mc+Mf (6)
in the formula (6), blade water moment MhAnd a centrifugal moment McThe positive sign of the front is opposite to or the same as the angle direction of the blade to be adjusted depending on the respective acting directions, the positive sign is taken when the directions are opposite, and the negative sign is taken when the directions are the same; due to blade friction moment MfAlways opposite to the blade adjustment direction, so the front always takes the positive sign.
2. Adjusting rod adjusting force calculation:
the mechanical type full regulating mechanism of the water pump blade is subjected to stress analysis as shown in figure 1, wherein 1 is the rotation center of a blade shaft; 2-rotating arm; 3, connecting rods; 4-handling frame, according to fig. 1, having the following relation:
PgLg＝Mb (7)
in the formula: mb-blade torque; l isgLength of pivoted arm；Pg-a tumbler driving force, directed perpendicular to the tumbler;
-the angle of the pivoted arm to its horizontal position; l isl-connecting rod length; beta is the included angle between the connecting rod and the vertical position; p1-the force of a blade link acting on the handling frame or the adjusting lever when adjusting the blade angle; p is the adjusting force on the adjusting rod when the angle of the blade is adjusted; z is the number of leaves. And (3) respectively calculating m multiplied by n calculation working conditions by using the formula (10) to adjust the stress of the adjusting rod when the blade is adjusted to a large angle and adjusted to a small angle.
3. Adjusting the adjusting force calculation after the length of the rotating arm is increased:
according to the formula (10), for the determined water pump, the working condition of the water pump is certain, namely the operation lift and the blade angle are certain, the blade adjusting direction is determined, and then, the blade number Z and the blade torque M are obtainedbIncluded angle
Certainly, the length L of the rotating arm is increased under the condition that the internal space of the impeller hub allowsgWhile proportionally increasing the length L of the connecting rodlIf the included angle beta is not changed, the adjusting force P and the length L of the rotating arm are adjustedgIn inverse proportion, the stress P of the adjusting rod is reduced, LgIs increased to L'gThe adjusting force P is reduced to P', and the length L of the rotating arm is respectively calculated by applying the formula (10)gThe m multiplied by n blades under the calculation working conditions are adjusted to a large angle and adjusted to a small angle under the stress P' of the adjusting rod, and the reduction rate of the adjusting force of the operating rod is
C. Selecting a small-inclination-angle separation thrust roller bearing:
in the separator of the mechanical full-regulating mechanism of the water pump, the lower release bearing is easy to be stuck, seriously abraded and the like. The lower release bearing adopts a tapered roller thrust bearing, the adjusting rod bears larger pressure P most of the time when the water pump runs, the pressure is transmitted to the lower release bearing, and the inner ring, the outer ring and the roller of the lower release bearing bear positive pressure N
N＝P/cosγ (12)
In the formula: the gamma-angle of inclination of the release bearing, i.e. the included angle between the working surface and the horizontal plane, usually, in order to take the radial force into consideration, the release bearing with a larger angle of inclination is selected, as a result, the positive pressure of the working surface of the bearing is increased, and the phenomenon of blocking of the bearing is easily caused by small radial clearance, installation error, thermal expansion during operation and pressure bending of the adjusting rod; the thrust bearing with the separated roller with a smaller inclination angle can reduce the pressure of the working surface of the bearing, prevent the bearing from being blocked during operation, and reduce the positive pressure of the separated bearing by the positive pressure reduction rate
In the formula: gamma' -the newly selected tilt angle of the release bearing.
D. The mechanical full-adjusting mechanism improves the calculation comparison of the front and back adjusting force, the angle adjusting error, the separating bearing force and the service life:
taking the blade angle as a horizontal coordinate and the adjusting force as a vertical coordinate, and comparing the adjusting force before and after the adjustment of the adjusting mechanism on one graph by using the adjusting force of the adjusting mechanism in two conditions of m multiplied by n working conditions of the original blade full-adjusting mechanism water pump calculated in the step B, blade shaft position optimization calculated in the step B and m multiplied by n working conditions of the water pump after the rotating arm of the adjusting mechanism is lengthened in the step B and the adjusting force of the adjusting lever for adjusting the small angle on one graph; the blade angle is taken as an abscissa and the angle adjusting error is taken as an ordinate, the blade angle adjusting errors of the water pump m multiplied by n working condition blade adjusting mechanisms before and after the improvement of the two conditions for adjusting the large angle are compared on one graph, and the blade angle adjusting errors of the small angle are compared on one graph; the small-inclination-angle separation thrust bearing is adopted, the pressure borne by the bearing is calculated by the formula (12), and the pressure reduction amplitude borne by the bearing is calculated by the formula (13).
Release bearing calculated life calculation using equation (14)
In the formula: l ish-bearing calculated life; n-water pump rotation speed; c, bearing rated dynamic load; n-bearing equivalent dynamic load; epsilon-index, for a thrust roller bearing epsilon 10/3; the calculated life of the front and rear lower throw-out bearings is improved using the calculation of equation (14) compared to a mechanical full adjustment mechanism.
The invention has the beneficial effects that: the method for improving the angle modulation precision and the reliability and durability of the mechanical full-regulating mechanism of the water pump has clear principle, eliminates the overlarge pressure of the regulating rod after the position of the blade shaft is optimized and the rotating arm of the regulating mechanism is increased based on the full-operation working condition of the water pump, and reduces the maximum absolute value regulating force of the blade by about 55 percent; the average absolute value regulating force under the full-operation working condition is reduced by about 60 percent; the maximum adjusting error of the angle of the blade is reduced to 0.11 degrees from 0.27 degrees, and the average adjusting error of the full-operation working condition is reduced to 0.04 degrees from 0.15 degrees; the problem that the adjusting rod is jammed, stiff, eccentric and damaged at the hollow water pump shaft, the motor shaft guide shaft sleeve and the lower separation thrust bearing due to the bow-shaped bending formed by large pressure is avoided, the pressure of the working surface of the separation thrust roller bearing is reduced by 68%, the service life is prolonged by about 30 times, and the adjusting rod has important significance for reducing the stress and deformation of a mechanical full-adjusting mechanism of the water pump, improving the angle adjusting precision of the blades and improving the reliability and durability of the adjusting mechanism.
Drawings
FIG. 1 is a force diagram of the mechanical blade adjustment mechanism of the present invention.
FIG. 2 is a graph of pump assembly performance in an embodiment of the present invention.
FIG. 3 is a comparison graph of full operating mode maximum blade water moments before and after blade shaft position optimization in an embodiment of the invention.
FIG. 4 is a graph comparing the blade angle adjustment force before and after the adjustment mechanism is modified in the embodiment of the present invention.
FIG. 5 is a graph comparing the adjustment force of the improved forward and backward adjustment of the small blade angle of the adjustment mechanism in the embodiment of the present invention.
FIG. 6 is a comparison graph of blade angle adjustment errors before and after the adjustment mechanism is improved in the embodiment of the present invention.
FIG. 7 is a comparison graph of the adjustment error of the adjustment mechanism for adjusting the blade angle back and forth according to the embodiment of the present invention.
In the figure: a vane shaft rotation center 1, a rotating arm 2, a connecting rod 3 and an operation frame 4.
Detailed Description
The invention will be further described with reference to the accompanying drawings in which:
large-scale vertical axial-flow pump of certain pump station, impeller diameter phi 1640mm, impeller wheel hub diameter phi 820mm, the impeller has 4 blades, and blade design angle 0, blade angle control range: 4 degrees to 6 degrees, the rotating speed is 250r/min, the design lift of a pump device is 6m, and the design flow is 10.6m3And s. The blades are made of stainless steel, and the general performance curve of the pump device is shown in figure 2 under the condition that the structures of the impeller and the guide vane of the water pump are known.
A. Optimizing the position of the blade shaft based on the full operation condition:
1. determining the calculation condition of the full-operation condition range:
according to the actual operating range of the water pump, 5 pump device lifts are determined: 3.5m, 4.75m, 6m, 7.25m, 8.5m, 5 blade angles of-4 degrees, -2 degrees, 0 degrees, 3 degrees and 6 degrees, and 25 calculation conditions in total.
And 2.5 multiplied by 5 blade water moment calculation under calculation conditions:
and (3) calculating to obtain 25 impeller blade water moments under calculation working conditions by using CFX fluid calculation software, as shown in a table 3.
TABLE 3 blade Water Torque (unit: N.m) for Water Pump conditions before blade shaft position optimization
3. Determining the position of the optimal blade shaft under the full-operation condition:
taking the working point that the lift H is 6m and the blade angle α is 0 ° as an example, the blade water moment is calculated to be 2974.868N · m by using CFX, the blade pressure resultant force acting line is located on the water inlet side of the blade shaft, and the distance from the blade shaft L is 0.0915m by calculation according to the formula (1). Through calculation of the 25 working conditions of the water pump, the action points of the resultant force of the water pressure of the blades are all located on the water inlet side of the existing blade shaft, the maximum value and the minimum value of the distance from the existing blade shaft are 0.193003m and 0.001734m respectively, the optimal blade shaft is located on the water inlet side of the existing blade shaft and is within the range from 0.001734m to 0.193003m from the existing blade shaft, and further partition calculation is carried out to determine that the position of the optimal blade shaft is located between 0.081429mm and 0.097368mm from the existing blade shaft.
In the range of 0.081429mm to 0.097368mm from the existing blade shaft on the water inlet side of the existing blade shaft, the optimal position of the blade shaft approaching the minimum maximum blade hydraulic moment is calculated by adopting a 0.618 golden section method, the optimal position of the blade shaft is 0.084m away from the existing blade shaft, and the error of the optimal position of the blade shaft satisfies the formula (2), namely, the optimal position of the blade shaft is not more than 0.001 m. After the position of the blade shaft is optimized, 25 blade water moments under calculation conditions of the water pump are shown in table 4, the blade water moments before and after the position of the blade shaft is optimized are shown in fig. 3, after the position of the blade shaft of the water pump is optimized, the maximum blade water moment under the full-operation condition is reduced by about 1/2, the average blade water moment is reduced by about 3/4, the blade water moment is obviously reduced, and the blade adjusting force under the full-operation condition of the water pump can be greatly reduced.
TABLE 4 embodiment blade shaft position optimized water pump each calculation condition blade water moment (unit: N.m)
B. Increase adjustment mechanism rocking arm length:
1. blade torque calculation:
aiming at the water pump and the mechanical full-adjusting mechanism of the blades of the water pump, numerical integration is carried out on the formula (4) to calculate the centrifugal moment M of the bladescWhen the blade angle is +6 degrees, +3 degrees, 0 degrees, -2 degrees and-4 degrees, the centrifugal torque of a single blade is 54.724N · m, 53.547N · m, 51.106N · m, 49.7768N · m and 48.3794N · m respectively, and the centrifugal torque is positive and indicates that the centrifugal torque has the tendency of rotating the blade around the direction in which the axial blade angle of the blade is increased; calculation of blade Friction Torque M Using equation (5)fThe friction torque of a single blade is 355.78 N.m; by the formula (6)Calculating blade torque M when adjusting large blade angle and small blade angleb。
2. Adjusting rod adjusting force calculation:
and (3) respectively calculating the stress of the adjusting rod when the 25 working condition blades of the water pump are adjusted to a large angle and adjusted to a small angle by using the formula (10).
3. Adjusting the adjusting force calculation after the length of the rotating arm is increased:
the length of the rotating arm is increased from 0.22m to 0.28m according to the space of the inner cavity of the hub, the connecting rods are simultaneously increased in proportion, the adjusting force is calculated by using the formula (10), for example, the adjusting force of the adjusting rod is reduced from 114865.26N to 90252.14N under a certain working condition, and the force of the adjusting rod is reduced by 21.4% according to the formula (11).
C. Selecting a small-inclination-angle separation thrust roller bearing:
in the embodiment, the lower release bearing originally adopts an 9069238 type roller thrust bearing, and the inclination angle or the contact angle is 40 degrees; instead of using a 32038 roller thrust bearing with an inclination angle of 25 °, it is known from equation (12) that the positive pressure N borne by the inner and outer races of the bearing and the roller is reduced without changing the adjustment force P of the adjustment lever, and the reduction ratio is calculated from equation (13)
D. The mechanical full-adjusting mechanism improves the calculation comparison of the front and back adjusting force, the angle adjusting error, the separating bearing force and the service life:
the adjusting force of the adjusting rod when the original blade full-adjusting mechanism and the blade shaft position are optimized and the rotating arm of the adjusting mechanism is lengthened is adjusted to be larger in angle under 25 working conditions of the water pump, as shown in figure 4, the adjusting force of the adjusting rod when the angle is adjusted to be smaller is shown in figure 5, and the angle adjusting errors under the two conditions are shown in figures 6 and 7; from fig. 4 to fig. 7, after the position of the water pump blade shaft is optimized and the rotating arm of the adjusting mechanism is lengthened, the maximum absolute value adjusting force of the blades is reduced from 114.9kN to 51.6N, and is reduced by 55.1%; the average absolute value regulating force of the full-operation working condition is reduced from 64.16kN to 24.29kN and is reduced by 62.1 percent; the maximum adjusting error of the angle of the blade is reduced to 0.11 degrees from 0.27 degrees, and the average adjusting error of the whole working condition is reduced to 0.04 degrees from 0.15 degrees; the phenomenon that the bow-shaped bending of the adjusting rod due to high pressure is jammed, stiff, eccentric and damaged at the hollow water pump shaft and the motor shaft guide shaft sleeve and the lower separation thrust bearing is avoided; by optimizing the position of the blade shaft, increasing the length of the rotating arm of the adjusting mechanism and selecting the lower separation thrust roller bearing with a small inclination angle, the average value of the working surface pressure of the lower separation thrust roller bearing under the full working condition is reduced to 26.80kN from 83.75kN, and the service life is prolonged by about 30 times. The invention has important significance for reducing the stress and deformation of the adjusting mechanism, improving the angle adjusting precision of the blade and improving the reliability and durability of the adjusting mechanism.
Claims (1)
1. The method for improving the angle modulation precision and the reliability and the durability of the mechanical full-adjusting mechanism of the water pump is characterized by comprising the following operation steps of:
optimizing the position of a blade shaft based on the full operation condition;
b, increasing the length of a rotating arm of the adjusting mechanism;
c, selecting a small-inclination-angle separation thrust roller bearing;
d, improving the front and back adjusting force, the angle adjusting error and the separating bearing force of the mechanical full adjusting mechanism and comparing the calculation of the service life;
the blade shaft position optimization based on the full-operation working condition in the step A comprises the following parts:
(1) full operating condition range calculation condition determination
In the range of the operating lift of the water pump, selecting m lifts at equal intervals, including the highest lift and the lowest lift, and selecting n angles, including the largest angle and the smallest angle, of the blade angle at certain intervals for each lift of the m lifts in the range of the operating blade angle of the water pump, so that m multiplied by n calculation working conditions are total;
(2) blade water moment calculation under m × n calculation conditions
Performing numerical simulation on the internal flow field of the water pump under M × n calculation conditions by using fluid calculation software to obtain the water moment M of the impeller bladeshAs shown in table 1, the water moment adjusts the blades to be positive in the large-angle direction;
TABLE 1 vane water moment M of each calculation condition of water pump before optimizing vane shaft positionhUnit: n.m
(3) Full operating condition optimal vane shaft position determination
The distance from the blade water pressure resultant force action line to the current blade shaft on the middle calculation section between the hub and the rim of the blade under each calculation condition is as follows:
in the formula: l is the distance from the resultant action line of the water pressure of the blade to the current blade shaft; mhThe blade water moment is directly obtained by calculation of fluid calculation software; fhCalculating by fluid calculation software to obtain axial water pressure, circumferential water pressure and radial water pressure of the blade respectively, and synthesizing to obtain a resultant water pressure;
on the calculation section of the blade, dividing an area s between two blade water pressure resultant force action lines farthest away in all m multiplied by n calculation working conditions into k equal parts, and respectively setting blade shafts 1, 2, …, k-1 and k at each equal part; calculating the blade water moment with the maximum absolute value in m multiplied by n working conditions of the water pump at the set k blade shaft positions, and determining two adjacent set blade shafts O for positive and negative conversion of the maximum hydraulic moment of the blades1-O1、O2-O2A location;
the method adopts 0.618 golden section method to find and determine the position of the blade shaft, so that the maximum water torque of the blade under the full working condition of the water pump is minimum, and the maximum water torque is set for the blade shaft O1-O1The maximum water torque of the blade shaft O is positive2-O2Is negative, then the self-O on the cross section is calculated in the blade1-O1Axial direction O2-O2The blade shaft O is set at the position of 0.618s/k distance from the shaft3-O3For blade axis O3-O3Maximum hydraulic moment of water pump all-condition blade(ii) a If for the blade shaft O3-O3The maximum water torque of the water pump all-working-condition blade is positive, which indicates that the optimal blade shaft is positioned at O3-O3Shaft and O2-O2Between the shafts, continue from O3-O3Axial direction O2-O2The shaft takes a distance of 0.618 (1-0.618) s/k, where the vane shaft O is set4-O4(ii) a If for the blade shaft O3-O3When the maximum water torque of the blades of the water pump under all working conditions is negative, the water pump continues to operate from the position O1-O1Axial direction O3-O3The axes are taken at a distance of 0.618 x 0.618s/k, where the blade axis O is determined4-O4… …, and so on, until the distance between two adjacent blade axes of the last approximation is small enough to satisfy equation (2),
Δs≤0.001m (2)
the blade shaft at the position is the optimal position blade shaft, the maximum hydraulic moment of the blades under all working conditions of the water pump can be guaranteed to be minimum, and after the position of the blade shaft is optimized, M multiplied by n working condition blade hydraulic moment M 'of the water pump are calculated'hAs shown in the table 2 below, the following examples,
meter 2 blade shaft position optimized rear water pump each calculated working condition blade water moment M'hUnit: n.m
The step B of increasing the length of the rotating arm of the adjusting mechanism comprises the following steps:
(1) blade torque calculation
Blade torque MbComprises blade water moment, blade centrifugal moment, blade friction moment, and blade water moment MhCalculating by using fluid calculation software;
when the impeller rotates, centrifugal force acts on each tiny mass on the blade, the action line of the centrifugal force is not superposed with or intersected with the blade shaft to generate moment to the blade shaft, and the resultant of the centrifugal force of all the masses of the blade to the moment of the blade shaft is the centrifugal moment M of the bladec；
The centrifugal force generated by any infinitesimal mass of the blade is as follows:
dF＝ρ(drdzrdα)rω2 (3)
in the formula: dF is the centrifugal force of the micro-mass of the blade; ρ -blade material density; omega-impeller angular velocity; r is the radius from the vane infinitesimal to the axis of the impeller; alpha is the included angle between the projection of the radius of the vane infinitesimal and the radius of the water inlet edge of the vane on the horizontal plane on a certain calculated cylindrical section; z is the height difference between the vane micro element on the cylindrical section and the vane axis in the z direction;
integrating all infinitesimal centrifugal forces of a single blade with the moment of a blade shaft to obtain the centrifugal moment of the single blade:
in the formula: mc-single blade centrifugal moment; rh-blade hub radius; r-radius at the blade rim; z is a radical ofu-calculating the difference in height of the profile of the airfoil in the section of the blade from the blade axis; z is a radical ofdCalculating the height difference from the lower profile of the airfoil on the section to the axis of the blade by the blade; alpha is alphamCalculating the central angle of the airfoil profile projected in the horizontal plane between the water inlet edge and the water outlet edge on the blade section; integrating the formula (4) by using a numerical method, and calculating to obtain the angle alpha of a single blade1，α2，…，αn-1，αnThe centrifugal moment of (a);
when the angle of the water pump blade is adjusted, the friction torque of a sealing rubber between the blade and a hub needs to be overcome, and the calculation formula of the sliding friction torque of the single blade seal is as follows:
Mf＝FfRs＝μpSRs (5)
in the formula: mf-blade friction torque; ff-blade root friction; rs-blade root seal friction face radius; mu-coefficient of friction between the blade root and the rubber seal; p-unit area sealing pressure; s, sealing area; the blade friction torque is irrelevant to the working condition of the water pump;
during blade adjustment, the torque M of a single bladebComprises the following steps:
Mb＝±Mh±Mc+Mf (6)
in the formula (6), blade water moment MhAnd a centrifugal moment McThe positive sign of the front is opposite to or the same as the angle direction of the blade to be adjusted depending on the respective acting directions, the positive sign is taken when the directions are opposite, and the negative sign is taken when the directions are the same; due to blade friction moment MfThe direction is always opposite to the blade adjusting direction, so the front face always takes a positive sign;
(2) adjustment lever adjustment force calculation
The mechanical full-adjusting mechanism of the water pump blade comprises a blade shaft, a rotating arm, a connecting rod and an operating frame, which are subjected to stress analysis, and the following relational expression is provided:
PgLg＝Mb (7)
in the formula: mb-blade torque; l isg-length of the swivel arm; pg-a tumbler driving force, directed perpendicular to the tumbler;
-the angle of the pivoted arm to its horizontal position; l isl-connecting rod length; beta is the included angle between the connecting rod and the vertical position; p1-the force of a blade link acting on the handling frame or the adjusting lever when adjusting the blade angle; p is the adjusting force on the adjusting rod when the angle of the blade is adjusted; z-number of leaves, respectively, by the formula (10)Calculating to obtain m multiplied by n calculation working condition blades, and adjusting the stress of the adjusting rod when adjusting towards a large angle and adjusting towards a small angle;
(3) adjusting lever adjustment force calculation after increasing the length of the rotating arm
According to the formula (10), for the determined water pump, the working condition of the water pump is certain, namely the operation lift and the blade angle are certain, the blade adjusting direction is determined, and then, the blade number Z and the blade torque M are obtainedbIncluded angle
Certainly, the length L of the rotating arm is increased under the condition that the internal space of the impeller hub allowsgWhile proportionally increasing the length L of the connecting rodlIf the included angle beta is not changed, the adjusting force P and the length L of the rotating arm are adjustedgIn inverse proportion, the stress P of the adjusting rod is reduced, LgIs increased to L'gThe adjusting force P is reduced to P', and the length L of the rotating arm is respectively calculated by applying the formula (10)gThe m multiplied by n blades under the calculation working conditions are adjusted to a large angle and adjusted to a small angle under the stress P' of the adjusting rod, and the reduction rate of the adjusting force of the operating rod is
The method for selecting the small-inclination-angle separation thrust roller bearing in the step C comprises the following steps:
in the separator of the mechanical full-regulating mechanism of the water pump, the lower release bearing is easy to be blocked and seriously abraded and the like, the lower release bearing adopts a thrust roller bearing, the regulating rod bears larger pressure P most of the time when the water pump runs, the pressure is transmitted to the lower release bearing, and the positive pressure N borne by the inner ring, the outer ring and the roller of the lower release bearing is
N＝P/cosγ (12)
In the formula: the gamma-angle of inclination of the release bearing, i.e. the included angle between the working surface and the horizontal plane, usually, in order to take the radial force into consideration, the release bearing with a larger angle of inclination is selected, as a result, the positive pressure of the working surface of the bearing is increased, and the phenomenon of blocking of the bearing is easily caused by small radial clearance, installation error, thermal expansion during operation and pressure bending of the adjusting rod; the separated thrust roller bearing with smaller inclination angle not only can reduce the pressure of the working surface of the bearing, but also can ensure that the bearing does not block during operation, and the positive pressure reduction rate of the separated bearing is
In the formula: gamma' -the newly selected tilt angle of the throw-out bearing;
d, the method for improving the front and rear adjusting force, the angle adjusting error, the separating bearing force and the service life of the mechanical full-adjusting mechanism in the step D is as follows:
taking the blade angle as a horizontal coordinate and the adjusting force as a vertical coordinate, and comparing the adjusting force before and after the adjustment of the adjusting mechanism on one graph by using the adjusting force of the adjusting mechanism in two conditions of m multiplied by n working conditions of the original blade full-adjusting mechanism water pump calculated in the step B, blade shaft position optimization calculated in the step B and m multiplied by n working conditions of the water pump after the rotating arm of the adjusting mechanism is lengthened in the step B and adjusting force of the adjusting rod for adjusting the small angle on one graph; the blade angle is taken as an abscissa and the angle adjusting error is taken as an ordinate, the blade angle adjusting errors of the water pump m multiplied by n working condition blade adjusting mechanisms before and after the improvement of the two conditions for adjusting the large angle are compared on one graph, and the blade angle adjusting errors of the small angle are compared on one graph; the small-inclination-angle separation thrust bearing is adopted, the pressure borne by the bearing is calculated by a formula (12), and the pressure reduction amplitude borne by the bearing is calculated by a formula (13);
release bearing calculated life calculation using equation (14)
In the formula: l ish-bearing calculated life; n-water pump rotation speed; c, bearing rated dynamic load; n-bearing equivalent dynamic load; epsilon-index, for a thrust roller bearing epsilon 10/3; front-rear lower release bearing improved by mechanical full-adjusting mechanism through formula (14) calculation and comparisonThe calculated lifetime of (c).
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103807184A (en) * | 2014-02-17 | 2014-05-21 | 扬州大学 | Method for determining blade adjustment frequency of variable-angle optimized operation of large fully-adjustable water pump station |
| CN105179303B (en) * | 2015-10-24 | 2017-05-24 | 扬州大学 | Axial flow pump impeller all-operating-condition design method |
| CN107143505A (en) * | 2017-06-20 | 2017-09-08 | 广东河海泵业机械有限公司 | A kind of in-service adjusting means of follow-up motor type mechanical water pump blade angle |
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2018
- 2018-01-05 CN CN201810009774.9A patent/CN108229027B/en active Active
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103807184A (en) * | 2014-02-17 | 2014-05-21 | 扬州大学 | Method for determining blade adjustment frequency of variable-angle optimized operation of large fully-adjustable water pump station |
| CN105179303B (en) * | 2015-10-24 | 2017-05-24 | 扬州大学 | Axial flow pump impeller all-operating-condition design method |
| CN107143505A (en) * | 2017-06-20 | 2017-09-08 | 广东河海泵业机械有限公司 | A kind of in-service adjusting means of follow-up motor type mechanical water pump blade angle |
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