Experimental measurement of squeeze flow in bearings

• Main Author: Low, Alan Xuan Yi
• Other Authors: Wong Yew Wah
• Format: Final Year Project
• Language: English
• Published: 2014
• Subjects: DRNTU::Engineering::Mechanical engineering::Fluid mechanics
• Online Access: http://hdl.handle.net/10356/60927
• Institution: Nanyang Technological University

This project investigates for the presence of positive pressure generation with the use of two extended spiral grooves bearings (SGB), namely 10 and 15 grooves with new geometries. As mentioned in the literature, these new geometries were designed and manufactured based on the optimum point obtained from the simulation results done by Loh [17] because the previous SGB geometries failed to generate positive pressure at the film thickness above 0.1mm. Furthermore, the area of interest in an axial clearance gap between the centrifugal rotating impeller and the stationary housing is to maintain at about 0.2mm in order to keep the power required to drive the impeller to a minimum and create a hydrodynamic lifting simultaneously. Thus, the experimental measurements were conducted for both extended SGBs in an open system, simulating the operation of ventricular assisted device (VAD) with an outflow rate of 0.01 L/min at various rotating speeds and film thicknesses. The rotating speed ranges from 300 to 2100rpm with an increment of 300rpm each time and four different film thicknesses ranges from 0.1 to 0.2mm. From the measurements, both extended SGBs had generated positive pressure at a film thickness between 0.1 and 0.15mm which has shown significant improvement as compared to the previous experimental results. However, a common trait which was observed for both the current and previous experiment is the drop in pressure when the film thickness increases. Moreover, two new traits were observed in the current experiment. One of which is the pressure from both extended SGBs rises with the rotating speed to a maximum magnitude occurring only at 1200rpm and descends subsequently. The other new traits noticed is the K10 extended SGB generally generates greater pressure than K15 at a similar film thickness. These new traits are probably due to the difference in geometries where all parameters are inter-related and have an effect on the overall pressure generation. In a nutshell, by utilizing each optimum point from the effect of varying single parameter such as spiral angle, α, the ratio of inner radius to outer radius, λ, the ratio of film thickness to groove depth, δ and the ratio of ridge width to groove width, γ, the new spiral groove geometries are able to generate positive pressure with the film thickness heightens up to 0.15mm.