RU2016257C1 - Vane pump - Google Patents

Abstract

FIELD: mechanical engineering; pumps. SUBSTANCE: pump has wheel 1 and inlet branch 5 which accommodates bypass chamber 2 with guide vane plate 3. Vanes 4 of guide vane plate 3 are crescent-shaped. Guide vane plate 3 is located at axial distance equal to 0.3 - 0.5 of calibre of diameter of branch 5 from wheel 1. Vanes 4 of guide vane plate 3 at inlet are installed at angle of 25 30 degrees and at outlet at angle of 150 - 160 degrees relative to front of guide vane plate 3. EFFECT: enhanced stability of operation of hydraulic system with vane pump owing to increase in head at low delivery duties. 2 dwg

Description

 The invention relates to hydraulic engineering and can be used in pump engineering for the design of pumps with a wide operating range of supply work.

 A known design of a vane pump, in which a bypass chamber is installed in front of the impeller, which eliminates cavitation self-oscillations in those modes when reverse currents are completely selected by the camera [1].

 However, the design is not efficient from an energy point of view, since in the bypass chamber there occurs an almost complete loss of the energy of the countercurrent swirl.

The closest technical solution is the design of a vane pump with a bypass chamber, in which a rectifying grid is installed, which serves to convert the kinetic energy of the "swirling" countercurrents into static pressure energy. In the rectifier lattice, the flow is completely unwound, i.e. the angle of flow at the exit of the lattice is approximately 90 ^about . The use of this design of the pump leads to an improvement in its anti-cavitation properties at low flow rates [2].

 The disadvantages of this design include the weak effect of the installation of a straightening grid on the pressure characteristic of the pump. Therefore, if the vane pump had an unstable branch of the pressure characteristic, then it is most often preserved for the design. This often leads to loss of stability of the hydraulic system with the pump, the basis of the mechanism of which are surge phenomena.

 The purpose of the invention is to ensure the stable operation of the hydraulic system with a vane pump by increasing the pressure at low flow rates.

This is achieved by the fact that in the vane pump, consisting of an impeller and an inlet pipe, a bypass chamber with a guide vane grill is installed, the blades of the guide grill are crescent-shaped, while the grill is located at an axial distance of 0.3-0.5 from the impeller the caliber of the diameter of the inlet pipe, and the grating blades at the inlet are installed at an angle of 25-30 ^about , and at the exit - at an angle of 150-160 ^{about the} front of the grating.

The proposed technical solution differs from the prototype in that the guide vane blades are crescent-shaped, while the lattice is located from the impeller at an axial distance of 0.3-0.5 caliber of the inlet pipe diameter, and the inlet grill blades are installed at an angle of 25-30 ^about , at the exit from the lattice - 150-160 ^about relative to the front of the lattice.

= -0,344 = const, т. е. направление потока к направлению окружной скорости составляет приблизительно -19^о, поэтому угол установки лопастей, в решетке на входе принят на 6-11^о больше (19^о), что обеспечивает натекание потока на лопатки с нулевым или небольшим положительным углом атаки. Для создания значительной "отрицательной" закрутки потока на выходе из решетки угол установки лопаток на выходе должен составлять 150-160^о. Фактический угол выхода потока из решетки несколько меньше из-за отставания потока от лопатки.Experimental studies have shown that for the counterflow zone at the periphery, the ratio of the meridional component of the flow velocity to the circumferential one is constant for all flows and along the axis of the pipeline:

= -0,344 = const, t. E. The direction of flow to the direction of the circumferential speed of approximately ^about -19, so the installation angle of the blades in the array at the input accepted at ^about 6-11 higher ^(about 19) that provides a leakage flux to scapula with zero or small positive angle of attack. To create a significant "negative" swirl of the flow at the exit from the lattice, the angle of installation of the blades at the outlet should be 150-160 ^about . The actual angle of exit of the flow from the grating is slightly smaller due to the lag of the flow from the blade.

-

, (1) где С_2и и С_1и - окружная составляющая скорости потока на выходе из рабочего колеса и на входе в него соответственно;
U₂ и U₁ - окружная скорость на наружном диаметре рабочего колеса D₂и на диаметре канала входных кромок лопаток колеса на входе D₁соответственно.In this case, the flow exiting the grate is “twisted” in the direction opposite to the rotation of the impeller, i.e. C _and <0. By turbulent viscosity, said negative swirl is transmitted to the main stream flowing into the impeller. Then, according to the Euler equation, the pressure of the pump increases
H _t =

-

, (1) where C _2i and C _1i are the circumferential component of the flow velocity at the exit of the impeller and at the entrance to it, respectively;
U ₂ and U ₁ - peripheral speed on the outer diameter of the impeller D ₂ and on the diameter of the channel of the input edges of the blades of the wheel at the input D _1, respectively.

Since C _1i <0, it follows from equation (1) that the pump head rises. Moreover, the smaller the flow rate Q, the greater the value of | C _{1 and} | and all the more significant is the increase in the pump head at low flow rates, which leads to a decrease in the pressure gradient from the feed, which makes the system more stable with respect to low-frequency surge fluctuations.

 In FIG. 1 and 2 show the design of a vane pump. The pump consists of a blade impeller 1, a bypass chamber 2, in which a grill 3 is installed, with crescent vanes 4. The bypass chamber 2 is located in the inlet pipe 5 of the pump. The flow inlet is located at a distance of 0.3-0.5 caliber diameter of the inlet pipe 5 of the pump. It is impractical to locate the beginning of the bypass chamber closer to the specified distance, since in this case the flow at the inlet to the chamber is essentially non-axisymmetric, to position it at a greater distance is also impractical, since the energy of countercurrents is lost due to friction against the pipeline walls.

 The work of the proposed design in low feed modes.

 From the impeller 1 into the inlet pipe of the pump 5 there are countercurrents that are strongly swirled towards the rotation of the wheel, which enter the bypass chamber 2, where due to the force action of the sickle-shaped blades 4 of the grill 3 and countercurrents, the flow is unwound in the inlet half of the grill of the blades 3, and in the output half of the lattice 3 - swirling the flow of countercurrents in the direction opposite to the direction of rotation of the impeller. The "swirling" flow enters the suction line, where, due to the action of turbulent viscosity forces, it "swirls" the main flow in the direction opposite to the direction of rotation of the impeller, resulting in an increase in the pump head at low flow rates.

PRI me R. The minimum pump flow is 20% of the nominal. The peripheral velocity of the countercurrents at the entrance to the grill is 0.75 U _n , where U _n is the peripheral velocity of the input edges of the wheel blades on the periphery. The flow angle at the periphery is approximately 19 ^about . The angle of installation of the blades of the wheel 30 ^about . Angle of attack of the flow at the entrance to the blade is less than 11 ^o, since the lattice is set at a diameter larger internal diameter of the pipeline (inlet), so because of the reduction C. _and at a flow transition to larger diameters upstream corner of the lattice increases, which leads to decrease the angle of attack.

3, где L_л - длина лопастей в решетке;
Z - число лопастей;
D - диаметр решетки.The lattice density τ =

3, where L _l - the length of the blades in the lattice;
Z is the number of blades;
D is the diameter of the grating.

= -

= -0,5 U_н. Знак минус означает, что окружная составляющая скорости потока, вытекающего из решетки, по направлению противоположна окружной скорости вращения центробежного колеса.For such a lattice, the coefficient taking into account the influence of a finite number of blades in the lattice is approximately equal to p ≈ 0.5. Then, with the equality of the meridian velocities in the lattice and the adoption of the angle of installation of the blades at the exit from the lattice βg.l.r = 150 ^about
C _2p = -

= -

= -0.5 U _n The minus sign means that the circumferential component of the flow rate flowing from the lattice is opposite in direction to the circumferential speed of rotation of the centrifugal wheel.

=

=

= 0,444, где Q_р.т - расход обратных токов;
Q - подача насоса. Если относить расход обратных токов к расходу Q, то

=

=

= 0,8. Таким образом, расход обратных токов только на 20% меньше подачи насоса.According to the dependence of the relative consumption of reverse currents
Q $\genfrac{}{}{0ex}{}{\text{′}}{\text{about}}$ _.t. =

=

=

= 0.444, where Q _rt is the flow rate of reverse currents;
Q - pump flow. If we relate the flow rate of reverse currents to the flow rate Q, then

=

=

= 0.8. Thus, reverse current consumption is only 20% less than the pump flow.

Naturally, such a powerful swirling flow causes a substantial swirling of the main flow, which, according to formula (1), leads to an increase in the pump head at low flow rates. It can be assumed that for pumps with a speed factor n _s = 80-150, the pump head at low flow rates increases by 20-30%.

Claims (1)

VANE PUMP, consisting of an impeller and an inlet pipe, in which a bypass chamber with a guide vane is installed, characterized in that, in order to ensure stable operation of the hydraulic system with a vane pump by increasing the pump head at low flow rates, the vanes of the guide vane are made sickle-shaped , wherein lattice extends from the impeller at an axial distance of 0.3 - 0.5 caliber diameter inlet and inlet grille vane mounted at an angle of 25 - 30 ^o, and the output of the lattice - at an angle of 150 - 160 ^o with respect to the front grille.

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