Research on Face Fluid Field and Seal Performance of T-shape Groove Dry Gas Seal
To obtain more details about the fluid field and high stability of dry gas seal, according to Reynolds equation of compressible perfect gas, on isothermal condition, the controlling equation of gas between the T-shape groove dry gas seal faces is established, and the controlling equation is converted into a non-dimensional equation. The gas flow capacity of T-shape groove dry gas seal is reached with computer simulation in Fluent software, on the basis of numerical simulation, the working parameters (such as, rotating speed, pressure, viscosity of medium, etc.) and the geometric parameters (such as, groove number, groove deep, groove width ratio, balance clearance, etc.) which affect seal performance, are discussed in detail, and the affecting curves are gained. The parameters ( such as, groove deep, balance clearance) which affect seal performance mostly should be chosen correctly in design. The general principle for selecting geometric parameters and working parameters of T-shape groove dry gas seal are obtained, for example, the groove number should be chosen within 12¿16, the groove deep should be chosen within 4¿6 μm, the balance clearance should be chosen within 0.8¿1.4 μm. It offers theoretical support for engineering design and application of T-shape groove dry gas seal.
Dry gas seal simulation with different spiral tapered grooves
The fl ow and performance analysis for a dry gas seal (DGS) with a standard and tapered spiral grooves is developed using a verifi ed FLUENT CFD model. A comprehensive analysis is proposed to resolve the effect of modifying the seal grooves geometry on gas fi lm pressure distribution and the seal performance. The effect of the fl uid state and the rotational speed on the gas seal performance and internal fl ow fi eld are studied and presented. The fl uid state effect on the gas seal internal fl ow and performance is studied, Laminar and turbulent fl ow with RNG K-ε turbulence model and LES is examined for the same geometrical and operating conditions. Also different rotational speed effect on gas seal Artkl V11(1).indd 1 24/12/2014 15:41:10 2 Journal of Mechanical Engineering performance is examined for 0, 2500, 5000, 7500 and 10380 rpm. Three taper spiral grooves are studied each with three different angles, including taper grooves in the radial, circumferential and combined radial-circumferential directions. The laminar fl ow simulation for the dry gas seal agree well with the experimental results more than the turbulent fl ow simulation which overestimate the pressure distribution inside the seal. The results indicate that as the rotational speed increase the seal open force and leakage increase. The use of tapered type spiral groove causes a reduction in the seal open force and the leakage rate. Increasing the angle of radial taper groove reduces the temperature distribution inside the gas fi lm. The Reduction in seal open force and leakage rate is higher when use combined Radial-circumferential taper more than radial and circumferential taper used.
An Experimental Investigation of Molecular Rarefaction Effects in Gas Lubricated Bearings at Ultra-Low Clearances
Abstract : The experimental investigation discussed here gives experimental confirmation of the slip-flow theory for modeling hydrodynamic gas bearings with clearances below 0.25 microns. An interferometric technique employing two CW lasers is used to measure the small clearances with an accuracy of 0.025 microns. The effects of molecular rarefaction are studied by operating the slider bearing in different gas media of different mean free paths. Bearings operating at extremely high local Knudsen numbers are studied without approaching excessively high bearing numbers. Experimentally measured trailing edge clearances and pitch angles are compared with theoretical predictions using the modified Reynolds equation with velocity slip boundary conditions. Excellent agreement between experiment and theory is found for clearances as high as 1.60 microns to as low as 0.075 microns with corresponding ambient Knudsen numbers of 0.04 and 2.51, respectively.