Vapor formation in a flooded lubrication turbine bearing

Vapor formation in a flooded lubrication turbine bearing

Roks, G.M.

Pecnik, R. (mentor)

Mechanical, Maritime and Materials Engineering

Process & Energy

2016-02-16

In this research a case study is performed to vapor formation in a turbine bearing. As a result of centrifugal forces in the rotating lubricant flow, low pressure regions occur in the bearing chamber. It is expected that vapor starts to form above a certain rotor speed. The formation of gaseous lubricant is presumed detrimental to the operation of the bearing. The specific case in this research is the turbine bearing of a commercially available Organic Rankine Cycle (ORC), operating at rotor speed up to 430 Hz. The ORC is a thermodynamic process, applied to recover energy from waste heat. In the machine of the case study the cycle medium is toluene. For technical reasons toluene is also used in the turbine bearing for lubrication purposes. In order to model the flows and heat transfer in the bearing, a two dimensional CFD model is created. The model output is validated against experimental data. After analysis of the results, a clear operating limit is found at 450 Hz. At this condition just outside the normal operating regime of the turbine, vapor formation sets on. Design changes proposed by the company are taken into account as well. The main alteration, moving the feed hole of the bearing chamber inward, proved to be effective. Simulation results show that bearing pressure at high speed is increased by more than 1 bar. The limit of the rotor speed in the alternative design is above 500 Hz.

bearing
turbine
lubrication
cavitation
tilting pad
ORC
CFD

http://resolver.tudelft.nl/uuid:dbd143ca-7908-4447-9cf0-193011e81984

2019-01-31

Student theses

master thesis

(c) 2016 Roks, G.M.