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Study on the water-lubricated high-speed non-contact mechanical face seal supported by a disc spring

  • Guo-Yuan Zhang
  • Xiu-Tian Yan
  • Yi Zhang
  • Wei-Gang Zhao
  • Guo-Zhong Chen
Technical Paper

Abstract

A type of non-contact mechanical face seal supported by a disc spring with high bending stiffness is proposed for actual working conditions and may be used in high-speed turbopumps with large axial loads and heavy random vibration. First, the separated speed of the seal is obtained, which shows that the initial contact mechanical seal can transform into a non-contact seal when the rotational speed is higher than the separated speed. Second, the steady-state model is proposed to describe the performance of the seal. The model includes the Reynolds equation, energy equation, lubricant temperature–viscosity relationship equation, and moment equilibrium equation, and the finite-difference method is used to solve the model. Third, with water as the sealed fluid, the effects of the geometric parameters and working parameters (e.g. spring stiffness, axial load, rotational speed) on the main performance parameters (film thickness, the maximum pressure, temperature, power loss, leakage) are obtained. The results show that with an increase in the stiffness of the spring, the film thickness and temperature increase change only slightly. With an increase in seal load, the film thickness decreases and the temperature increases. The film thickness increases and the temperature decreases with an increase in rotational speed. The results show that the proposed mechanical seal supported by such disc spring can be used in turbopump systems with higher speeds and smaller leakage requirements.

Keywords

Mechanical seal (face seal) Hydrostatic lubrication Disc spring Water Turbopump 

List of symbol

C

Coefficient (c = Ds/ds)

cp

Specific heat of the fluid

ds

Inner diameter of the disc spring

Ds

Outer diameter of the disc spring

E

Spring material elastic modulus

Fc

Close force of the seal

Fs

Spring force of one single disc spring

Gp

Tilting angle of the seal ring along the swinging pitch line

hm

Initial seal’s gap (fluid film thickness)

hmin

Minimum film thickness

I

Rotor ring’s moment of inertia

K

Axial stiffness of flexible support

Kθ

Angular stiffness of flexible support (springs)

M

Coefficient (\(m = {{\frac{1}{\pi }\left( {\frac{c - 1}{c}} \right)^{2} } \mathord{\left/ {\vphantom {{\frac{1}{\pi }\left( {\frac{c - 1}{c}} \right)^{2} } {\left( {\frac{c + 1}{c - 1} - \frac{2}{\ln c}} \right)}}} \right. \kern-0pt} {\left( {\frac{c + 1}{c - 1} - \frac{2}{\ln c}} \right)}}\))

Mf

Friction moment of the seal

Mx

Total moment of the seal in x-axis

My

Total moment of the seal in y-axis

M1

Moment acting on the seal ring from the bending spring (x-axis)

M2

Moment acting on the seal ring from the bending spring (y-axis)

M3

Moment on the seal ring from the spring compression (x-axis)

M4

Moment on the seal ring from the spring compression (y-axis)

N

Seal’s power loss

p

Fluid film pressure

pi

Fluid inlet pressure

pmax

Maximum film pressure

Q

Seal’s leakage

r

Radius of one position on the seal ring

rc

Radius of the film pressure centre position

Rdi

Inner radius of the seal dam

Rdo

Outer radius of the seal dam

Re

Equivalent radius of the sealing fluid

Re-in

Equivalent inner radius of the seal ring exerted by the fluid

Re-out

Equivalent outer radius of the seal ring exerted by the fluid

Ri

Inner radius of the seal ring

rm

Radius of the position at the minimum liquid film thickness

Ro

Outer radius of the seal ring

t

Spring thickness

t0

Maximum compression of spring

T

Temperature of the fluid film

T0

Inlet temperature of the sealed fluid

Tmax

Maximum film temperature

W

Seal’s load

α

Tilting angle or swinging angle of the seal ring

β

Viscosity coefficient

γs

Radial location of the flexible support

θ

Circumferential angle of one position on the seal ring

θc

Circumferential angle of the film pressure centre position

θm

Circumferential angle of the position at the minimum liquid film thickness

θp

Circumferential angle of the swinging pitch line

θ1

Angle between the centre line OO1 and the x-axis

ϕ

Circumferential angle of the grooves’ shape

δ

Spring deformation value (or the spring compression value)

ρ

Fluid density

μ

Fluid viscosity

μ0

Fluid viscosity at the inlet temperature T0

ν

Poisson’s ratio

ωsep

Separated speed

Ω

Rotational speed of the seal’s rotor

Tavg

Average film temperature rise

Notes

Acknowledgements

This work was supported by National Natural Science Foundation of China (Project No. 51575418) and CSC (China Scholarship Council) scholarship (No. 201606965015).

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Copyright information

© The Brazilian Society of Mechanical Sciences and Engineering 2018

Authors and Affiliations

  1. 1.School of Mechano-Electronic EngineeringXidian UniversityXi’anChina
  2. 2.Department of Design, Manufacture and Engineering ManagementThe University of StrathclydeGlasgowUK
  3. 3.Xi’an Aerospace Propulsion InstituteChina Aerospace Science and Technology Corporation (CASC)Xi’anChina

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