Abstract
Abstract The Narrow Groove Theory (NGT) is commonly used to simulate and design grooved gas bearing. However, measurements of dynamic force coefficients of Herringbone Grooved Journal Bearings (HGJBs) is missing, hence the validation historic NGT has never been performed, despite its importance. A test rig was built in order to identify stiffness and damping coefficients of HGJBs of a rotor perturbed by piezo-electric shakers. Results indicate that the NGT captures the qualitative behavior of HGJB well but tends to overestimate the stiffness and damping coefficients by 23 and 29% respectively. Gravity led to a eccentricity ratio in excess of 15% without significant effect. The direct damping coefficient was found to be mildly non-linear with the excitation amplitude.
Highlights
Herringbone grooved journal bearings (HGJB) are suited for the devel3 opment of small-scale turbomachinery for decentralized energy conversion, 4 including waste heat recovery [1], heat pumping [2, 3], fuel cell gas recircu5 lation [4, 5] and fuel cell pressurization [6]
The modelling tools 8 have been only partially validated with experimental data and the proper 9 evaluation of dynamic force coefficients is non-existent
In order to assess the dynamic predictions of the Narrow Groove The272 ory commonly employed in the design of spiral groove bearings, a test rig consisting in a rotor supported on two Herringbone grooved journal bearings and excited with shakers was built
Summary
Herringbone grooved journal bearings (HGJB) are suited for the devel opment of small-scale turbomachinery for decentralized energy conversion, 4 including waste heat recovery [1], heat pumping [2, 3], fuel cell gas recircu lation [4, 5] and fuel cell pressurization [6]. Hirs [10] investigated the load capacity of HGJB using a grooved test rotor supported on two rolling elements bearings where the external load was applied on the floating bushing He found a good agreement between the predictions and the experiment. The first one, pioneered on gas bearings by Heshmat and Ku [25], consist of a rotor supported on two stiff bearing (often oil lubricated or on rolling elements) where the test bearing, floating on the rotor, is perturbed by a force of known amplitude Recent applications of this approach include Wang and Kim [23] and Etras and Delgado [26] for foil and hybrid bearings respectively. The precise knowledge of these properties can be diffi cult to evaluate due to the complex motion of the bushing on its compliant 64 support (flexible blades, o-rings, etc) and can be frequency-dependent
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