| The balance of axial force has always been the focus of the centrifugal pump industry.Most of the existing axial force balancing devices have complex structure,which balance less axial force and have a greater impact on the performance of the pump.Therefore,it is of great significance to study the new axial force balanc ing devices.According to the flow characteristics of the pump cavity,the plunger type axial force balance device of the centrifugal pump was proposed in this thesis.The theoretical calculation,numerical simulation and experimental verification were u sed to study it,and the relevant conclusions were obtained.(1)In order to study the flow mechanism of the disk cavity of the plunger type axial force balancing device of the centrifugal pump,the disk cavity pressure test device was designed.The dimensionless parameters,such as gap diameter ratio,pressure coefficient and rotational Reynolds number,were introduced,and the disk cavity coefficient was defined.The experimental study was carried out when gap diameter ratio was 0.0026 and disk cavity coefficient was 0.058 and 0.077.The results show that the pressure coefficient of each pressure measuring point decreases with the increase of flow rate and increases with the increase of radius.The pressure coefficient and radius in the cavity are approximately linear.The curve of pressure coefficient and rotational Reynolds number shows a parabola rise.The increase of rotational Reynolds number will lead to the increase of pressure gradient in radius direction in the cavity.With the increase of disk cavity coefficient,the head and shaft power of the pump decreased slightly and the efficiency increased.(2)From the theoretical point of view,this thesis put forward the relevant assumptions of the flow in the disk cavity.Combined with the boundary conditions,the Navier-Stokes equations was simplified and the calculation formula of the pressure in the disk cavity was obtained.When gap diameter ratio was 0.0013,0.0026,0.0039 and disk cavity coefficient was 0.019,0.038,0.058,0.077,0.097,0.116,the numerical calculation was carried out.The leakage coefficient was introduced.The influence of gap diameter ratio and disk cavity coefficient on the pressure and the leakage was analyzed.The results show that the curve of pressure coefficient and disk cavity coefficient increases linearly,and the slope decreases with the increase of gap diameter ratio.The pressure coefficient of disk cavity increases with the increase of gap diameter ratio,and then tends to be stable.The leakage coefficient is positively correlated with gap diameter ratio and disk cavity coefficient.Gap diameter ratio is the main factor affecting the leakage,and disk cavity coefficient is the secondary factor.The leakage coefficient is the smallest when gap diameter ratio is 0.0013.(3)The axial forces on the impeller were classified according to the action position.Through numerical calculation,the variation of axial force with disk cavity coefficient and gap diameter ratio was studied.The results show that the axial force of the front cover plate plays a dominant role in each component of axial force,and the axial force inside the impeller can be ignored.The change of gap diameter ratio and disk cavity coefficient can lead to the change of the axial force of rear cover plate,and the other components will not be affected.The axial force of rear cover plate incr eases linearly with disk cavity coefficient increasing and approximately as a power function with gap diameter ratio increasing.There are zero points in the curves of total axial force and gap diameter ratio,which are mainly distributed between 0.0025 an d 0.0035,and most of them are near 0.003.The plunger type axial force balancing device can balance the residual axial force of about 3500 N through the reasonable combination of 3 groups gap diameter ratio and 6 groups disk cavity coefficient. |
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