2 PhD Candidate Positions Division of Machine Elements Department of Applied Physics and Mechanical Engineering
*1. JOB DESCRIPTION: *
One of the positions is within the project *"Dynamic behaviour of low viscosity fluid film bearings with compliant linings"*
The second position is within the project *"Determination of dynamic characteristics of hydrodynamic journal bearings"*
Journal bearings are used to transmit loads from rotating shafts to surrounding structures in most medium to large rotating machinery such as electric motors, generators, turbines, pumps etc and thus in many aspects define the dynamics of the machinery. The high demand for journal bearings is due to their long term performance, quietness of operation, exceptional damping properties, smaller outside diameter compared to rolling element bearings and low cost.
Nowadays, many power plants operate in harsh conditions with regular stops and start-ups, a factor brought about by the deregulation of the Nordic energy market. These machines were not designed for such severe operating conditions. To avoid malfunction and failures, much better understanding of bearing dynamic behaviour is required.
Continuous modernisation of old machinery results in the introduction of new lubrication and bearing technologies. Both performance and environmental issues are now of importance. Environmental concerns have led to a strong interest in environmentally adapted lubricants such as some synthetic oils and even water. These lubricants have lower viscosity than the mineral turbine oils currently used. A decrease in lubricant viscosity will have a significant effect on bearing dynamic characteristics. Furthermore, in some fluid film bearings a layer of soft material is used to improve bearing tribological performance. The extent to which dynamic characteristics are affected by the layer will depend on the soft material properties.
It is important to understand how lubricant and material properties affect bearing dynamics. An efficient way to investigate this issue and to obtain some optimised solutions is to use analytical software tools. The existing bearing computer models used by bearing manufacturers and end users are simplified and do not take into account many important parameters. Moreover, most of the models available are linearised. In hydropower applications the motion of the journal axis often has a large amplitude. The non-linearity encountered in these circumstances is not negligible and can bring about a different system motion.
The first project deals with the development of non-linear fluid-film journal bearing models. The models will account for various lubricant viscosities and lining properties. The models will be verified in the dynamic bearing test rig developed within the second project.
The second project deals with the development of an automated test rig for the dynamic evaluation of hydrodynamic journal bearings to provide the essential experimental data. Such data will be produced for different bearings so that more accurate and efficient models can be developed within the first project.
*2. REQUIREMENTS: *
Required education and skills: University Graduate.
The Candidates should have a Masters or equivalent degree in Physics or
Mechanical Engineering, strong analytical skills and/or practical experience
with machine design. Candidate for the first project should have an interest
in modelling and simulation of multi-physics phenomena. It is of great
advantage if the Candidates have fundamental understanding in some of the
following fields: machine dynamics, machine design, rotordynamics, scientific computing, and/or tribology.
Fluency in English is required.
*3. ORGANISATION:
*Luleå University of Technology, Sweden
Department of Applied Physics and Mechanical Engineering
Division of Machine Elements
*4. CONDITIONS OF EMPLOYMENT:
*Estimated maximum salary per month is €2400. This salary is taxable in Sweden. Duration of the employment contract is 36 months. The contract type is for a specified period. The start date is September 1st 2007.
*5. HOW TO APPLY AND ADDITIONAL INFORMATION:
*Candidates should email a detailed CV and a letter of motivation to the project contact person: Associate Professor Sergei Glavatskih, +46 920 492022, email: segla@ltu.se *not later than 12-August-2007. *
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