SGT-600 Lube Oil System Simulation

Klooster, S. (2016) SGT-600 Lube Oil System Simulation.

Abstract:The lube oil system in the SGT 600 has to supply oil of the correct pressure and temperature to the gas turbine bearings, the gear and the compressor bearings for lubrication and cooling. The lubrication oil used in the system is mineral based turbine oil ISO VG 46. The oil in the system goes through multiple components before the bearings and gear are reached. Two centrifugal pumps, which are driven by electric motors, pump the oil through a cooler, bypass line, 3 way temperature valve and a filter before the oil enters the bearings. All these components have a pressure loss (resistance) which depends on the flow that goes through the component. On the other side, the flow that is present in the system depends on the resistance of the total system. To show this dynamic behaviour of the system, a simplified mathematical simulation model is required for the start-up of the lube oil system of the SGT 600. This model must calculate the flow and pressure in each part of the lube oil system. Furthermore, the bypass line over the cooler has an orifice plate which must take care of a pressure loss that is equal to the pressure drop of the cooler. The simulation model must provide a suitable selection tool for the orifice bore diameter of the bypass line. The simulation tool used for this model is Matlab Simulink. To simulate the total lube oil system, the model is split into an iterative part and an integration part. For the total model, these two parts are coupled after both models are tested. The iterative part finds the flow in the total lube oil system and the integration part takes care of the coupling between the electric motors and the centrifugal pumps. This way, the start-up behaviour can be described. From available datasheets it can be seen that the desired pressure upstream the bearings in the system does not correspond to the design flow and speed of the centrifugal pumps. So the centrifugal pumps do not operate at their best efficiency point. The simulation tool described in this report will predict the flow and the pressure at every component in the system. The final model described in this report is capable of finding the pressure and flow at each component in the system. However, the final model contains a lot of assumptions which cannot be validated due to a lack of data. Also, the model is capable of showing the physical behaviour. This physical behaviour contains the distribution of the flow over parallel components, where the components with the lowest resistance gets the most flow. It also contains the dynamic behaviour where the resistance determines the flow in the system and the flow on its turn determines the resistance. The final model is also capable of predicting the mentioned orifice diameter in the bypass line over the cooler. The model runs a script which calculates the desired diameter to get the same pressure loss over the bypass line as over the cooler.
Item Type:Internship Report (Master)
Siemens, the Netherlands
Faculty:ET: Engineering Technology
Subject:52 mechanical engineering
Programme:Mechanical Engineering MSc (60439)
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