I. Etsion

A Laser Surface Textured Hydrostatic Mechanical Seal

A mechanical seal subjected to laser surface texturing over an annular portion of one of its mating rings is theoretically and experimentally investigated. The partial surface texturing provides a mechanism for hydrostatic pressure build up in the sealing dam similar to that of a radial step or face coning. Optimization of the surface texturing parameters to obtain maximum hydrostatic pressure effect is performed on a theoretical model. A test rig that allows friction torque and temperature measurements in a back-to-back double seal arrangement is used to validate the surface texturing effect. It is found that optimally textured seals generate substantially less friction and heat. Moreover, a simple unbalanced seal, limited in its pressure capacity, can be easily transformed by surface texturing to an equivalent balanced seal with much higher pressure capability. Presented at the 57th Annual Meeting Houston, Texas May 19–23, 2002

Experimental Investigation of Partial Laser Surface Texturing for Piston-Ring Friction Reduction

An experimental study is presented to evaluate the effect of partial laser surface texturing (LST) on friction reduction in piston rings. In a previous study, 30% friction reduction was obtained with full LST where the full width of the piston ring is textured with a very large number of microdimples that act individually as microhydrodynamic bearings. In partial LST, only a portion of the piston-ring width is textured with high dimple density, producing a “collective” effect of the dimples that provides an equivalent converging clearance even with nominally parallel mating surfaces. Experimental results obtained with flat and parallel test specimens with partial LST are presented, confirming a previously published theoretical model and the advantage of partial over full LST. Friction reduction by LST with actual production-crowned piston rings and cylinder liner segments is not straightforward and needs further investigation. Presented at the STLE Annual Meeting in Las Vegas, Nevada May 15-19, 2005 Review led by Gray Barber

Stability Threshold and Steady-State Response of Noncontacting Coned-Face Seals

The dynamic behavior of a noncontacting coned-face seal is analyzed. Stiffness and damping properties of the fluid film and flexible support including elastomeric secondary seal are fully accounted for. Stability threshold and steady-state response in the presence of rotor axial runout and assembly misalignment are investigated. An expression is provided for the critical speed above which the seal becomes dynamically unstable. For stable operation, the relative misalignment between the mating faces is given as a function of rotor runout, assembly misalignment, design parameters, and operation conditions. An expression is provided for the critical rotor runout above which the seal will fail due to face contact. Although the analysis is based on small perturbation assumption, it is shown to be valid in many practical cases. Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Lubrication Conference in San Diego, California, October 22–24, 1984

Dynamic Analysis of Noncontacting Face Seals

The dynamic behavior of a noncontacting coned face seal is analyzed taking into account various design parameters and operating conditions. The primary seal ring motion is expressed by a set of nonlinear equations for three degrees of freedom. These equations, which are solved numerically, allow identification of two dimensionless groups of parameters that affect the seal dynamic behavior. Stability maps for various seals are presented. These maps contain a stable-to-unstable transition region in which the ring wobbles at half the shaft frequency. The effect of various parameters on seal stability is discussed and an empirical expression for critical stability is offered.

A Model for Static Sealing Performance of End Face Seals

The effect of face loading, surface roughness and material properties on the static sealing performance of mechanical face seals is analyzed. The analysis combines the problems of contact and flow between two rough surfaces. The results are compared with available experimental data and are found to be reasonable. Based on many numerical results, a simple empirical expression is derived which enables easy and quick evaluation of the effect of the various parameters on seal performance

Nonlinear Dynamic Analysis of Noncontacting Coned-Face Mechanical Seals

The complete nonlinear equations of motion of a flexibly mounted stator in a noncontacting coned-face mechanical seal are solved numerically. The solution utilizes a transient dynamic analysis and takes into account rotor axial runout and assembly tolerances in the form of initial stator misalignment. Cavitation of the fluid film is also accounted for. A parametric investigation is performed and the effect of various design parameters and operation conditions on the seal dynamics is presented and discussed. A critical shaft speed is found above which the seal becomes dynamically unstable. A critical rotor runout is found which, if exceeded, will cause seal failure due to local face rubbing contact. A comparison is made between the numerical results and those of a simpler analytical solution. It is found that the analytical solution is valid for most practical applications of mechanical seals. Presented at the 40th Annual Meeting in Las Vegas, Nevada May 6–9, 1985

Performance of End-Face Seals with Diametral Tilt and Coning–Hydrodynamic Effects

Hydrodynamic effects in end-face seals with diametral tilt and coning are analyzed. A closed-form solution for the axial separating force and the restoring and transverse moments is presented that covers the whole range from zero to full angular misalignment at various degrees of coning. Both low-pressure seals with cavitating flow and high-pressure seals with full fluid film are considered. The effect of coning is to reduce the axial force and the restoring and transverse moments compared to their magnitude in flat-face-seals. Strong coupling between diametral tilt and transverse moment is demonstrated. This transverse moment which is entirely due to hydrodynamic effects can be the source of dynamic instability in the form of seal wobble. Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Lubrication Conference in Dayton, Ohio, October 16–18, 1979

Enhancing Sealing and Dynamic Performance with Partially Porous Mechanical Face Seals

A partially porous mechanical face seal is analyzed. The Reynolds equation is solved analytically and the pressure distribution, leakage, and dynamic coefficients are presented in closed form analytical expressions. It is shown that a partially porous seal has an axial stiffness even in cases of flat parallel faces when solid face seals have no such stiffness at all. A comparison is made between optimally designed partially porous and coned face seals. It is shown that the former give substantial improvement. Presented as a Society of Tribologists and Lubrication Engineers paper at the STLE/ASME Tribology Conference in New Orleans, Louisiana, October 24-27, 1993

The accuracy of the narrow seal approximation in analyzing radial face seals

The accuracy of the narrow seal approximation which enables closed form analytical solutions for radial face seals is examined in this paper. Both hydrostatic and hydrodynamic effects in a flat, misaligned seal are considered. Analytical, results obtained from a simplified Reynolds equation, based on the neglect of circumferential pressure gradient and seal curvature, are compared with accurate results from numerical solution of the complete Reynolds equation. The agreement between the approximate and accurate solutions is quite reasonable over a wide range of a seals inner-to-outer radius ratio. For radius ratios greater than 0.8, the accuracy of the narrow seal approximation is better than 1 percent over most of the range of angular misalignment. Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Lubrication Conference in Minneapolis, Minnesota, October 24–26, 1978

A thermohydrodynamic analysis of a misaligned mechanical face seal

A thermohydrodynamic analysis is performed for a misaligned mechanical face seal. Temperature variations both across the sealing gap and along its radial and circumferential extent are considered. The energy equation is solved analytically and temperature distribution is presented in an implicit form. It is shown that, in most practical cases, the amplitude of temperature variation along the seal circumference due to misalignment is negligible compared to the mean temperature. The radial temperature distribution can be obtained by solving an equivalent aligned seal whose face separation is reduced by a factor that contains the effect of misalignment. Presented at the 47th Annual Meeting in Philadelphia, Pennsylvania May 4–7, 1992