# Salinity Effect in Seawater Thermoelastohydrodynamic Lubrication of Double Spiral Groove Face Seals

## TL;DR

This paper studies how seawater salinity affects the performance of face seals used in deep-sea equipment, showing that double spiral grooves can enable zero-leakage designs even under high pressure.

## Contribution

The study introduces a TEHL model for double spiral groove face seals that incorporates salinity and cavitation effects for deep-sea applications.

## Key findings

- Salinity increases opening force by about 5% and causes leakage to shift direction with ±100% variation.
- Double spiral grooves allow for zero-leakage designs in seawater face seals under pressures exceeding 4 MPa.
- The seal design shows excellent adaptability to varying pressure, speed, and temperature conditions.

## Abstract

A rise in seawater salinity results in an increase in its viscosity, which presents a coupled influence on the distribution of fluid pressure, temperature and deformation at the sealing face, leading to fluctuations in sealing performance and forming the salinity effect in seawater thermoelastohydrodynamic lubrication (TEHL). Here, for a double spiral groove face seal, a TEHL model is established and numerical analysis is carried out, taking account of the salinity effect and cavitation effect, with the aim to ensure that the seal maintains stable performance under varying conditions of sea depth and speed. It is found that the effect of salinity on the opening force and leakage rate exhibits obvious nonlinear variations. As salinity rises from 0 to the standard 35 g/kg, the opening force changes by about 5%, and there is a transition between forward and reverse leakage, with variations of approximately ±100%. More importantly, the double spiral grooves offer the potential for a zero-leakage design in seawater face seals, even under pressures exceeding 4 MPa, through precise design. Additionally, the double spiral groove face seal shows excellent adaptability under multipoint conditions and can facilitate a zero-leakage design in varying pressure, speed and temperature conditions. This provides theoretical support for deep-sea equipment and applications in other extreme environments.