Restrictor-based studies of hybrid hole-entry conical journal bearings

Purpose This paper aims to describe how successfully a particular restrictor delivers its best in increasing the conical journal bearing performance. The restrictors are used in the hole-entry conical journal bearing subjected to hybrid mode. Thus, the restrictors, like constant flow valve (CFV), orifice and capillary, are studied comparatively. Design/methodology/approach Numerical simulation for the bearing results with the three restrictors are obtained by using finite element method (FEM) under the well-known modified Reynolds equation. Findings When the hole-entry conical journal bearings, with the restrictor design parameter range C¯s2 = 0.03 – 0.09, are operated, the results obtained are quite distinctive and significant. It indicates that the CFV restrictor-based conical bearing gives enhanced performance in comparison to orifice and capillary restrictors. Moreover, it suggests the performance-wise sequence of the restrictors in hybrid bearings as CFV > Orifice > Capillary. Originality/value The outcome of the research paper will give insight to help the bearing designer to choose the particular restrictor in hybrid conical bearing depending on the industrial need.

Characterization of Nothacrobeles lanceolatus Abolafia & Peña-Santiago, 2003 (Rhabditida, Cephalobidae), a typical species of coastal dunes from Spain

The nematode Nothacrobeles lanceolatus was described in arid soils from Cabo de Gata-Níjar Natural Park, province of Almería (Spain). Since then this species has not been found again. In this study, new data on the distribution and morphological, morphometrical and molecular characteristics (based on 18S and 28S ribosomal DNA) of N. lanceolatus is provided. This species is characterized by having a tessellated cuticle, with its inner layer bearing two rows of cuticular punctations per annulus, lips quadrangular with eight pinnae, labial probolae bifurcate with divergent prongs surrounded by pinnae, pharynx with corpus 2.5–4.0 times isthmus length, post-vulval uterine sac 1.4–2.2 times the corresponding body diameter, and female and male tails conical, bearing a conical mucro with acute terminus. The phylogenetic position of this and related species of the genus Nothacrobeles is discussed. Additionally, bacteria (Pasteuria) and fungi (Catenaria, Nematocida) feeding on N. lanceolatus are showed including light microscopy and scanning electron microscopy illustrations.

Analytical Study of Non-Recessed Conical Hole Entry Hybrid/Hydrostatic Journal Bearing with Constant Flow Valve Restrictor

The present work studies the analysis of a non recessed hole entry conical hybrid/hydrostatic journal bearing adjusted for constant flow valve (CFV) restriction. The paper provides effectiveness between the conical bearings with hole entry operating in hybrid and hydrostatic mode. The Reynolds formulae, for the flow of fluid through the mating surfaces of a conical journal and bearing, are numerically worked out in both the modes considering the finite element analysis (FEA) and the necessary boundary preconditions. Holes in double row are marked on conical bearing circumference to accommodate the CFV restrictors, the angular distance between two holes are 30o apart from the apex. Qualitative features of the conical journal bearing system with hole entry have been elaborated to analyze bearing performance for radial load variation Wr = 0.25-2. Numerical results obtained from the present study indicate that load carrying capacity of conical bearing, operating in hydrostatic mode, is enhanced by the maximum pressure, direct fluid film damping and direct film stiffness coefficients vis-a-vis corresponding hybrid mode.

Effect of taper error on the performance of gas foil conical bearing

Purpose This paper aims to study the bearing performance with different cone angle errors, to study the effect law of manufacturing taper error on the properties of gas foil conical bearing (GFCB). Design/methodology/approach For the GFCB supported by separated bump foil strips, a nonlinear structure stiffness model considering Coulomb friction and arch characteristics was proposed. The finite element method and finite difference method were used to solve the Reynolds equation and the film thickness equation by coupling, and the properties of the GFCB were obtained. The effect of foil and bearing structure parameters on the static and dynamic performance under different taper error cases was analyzed. Moreover, a test on the air compressor supported by GFCBs was conducted to verify the practicability. Findings The taper error has a largely adverse effect on the load capacity of GFCB. When the taper error is −0.03°, the radial load capacity Fr and axial load capacity Fz decrease by 37.5 and 58.3%, respectively. The taper error decreases the direct stiffness and cross-coupled damping of GFCB, which will weaken the bearing stability. Moreover, the performance of GFCB is closely related to the foil and bearing parameters. Originality/value The taper error adversely affects the static and dynamic characteristics of GFCB, which should be concerned by bearing designers, researchers and academicians. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-03-2020-0089/

Study on the performance of novel gas foil conical bearings

To reduce the mass and size of low-power turbine machinery, a new type of gas foil conical bearing was proposed, and its static and dynamic performance was systematically studied. Based on a nonlinear bump stiffness model considering rounding and friction, the structural stiffness distribution, load capacity, dynamic stiffness, and damping coefficients of gas foil conical bearing were calculated, and the influence of bearing parameters on its static and dynamic characteristics was studied. In addition, a pair of gas foil conical bearings was used to replace the traditional radial-thrust foil bearing support scheme on an air compressor to explore the practicability of the novel bearing. The results show that the new gas foil conical bearing has an excellent supporting performance and broad prospects for application. The bump radius, rounding radius, friction coefficients, and foil thickness will significantly influence the bump foil stiffness. The bearing parameters such as structural stiffness, nominal clearance, cone angle, and eccentricity have a large effect on its static and dynamic performance, and we can obtain the desired bearing characteristics by tailoring these parameters.