Comparative Evaluation of Joint Leak Tightness for Two Steam Turbine Casing Geometries
Homann, Jochen (2015)
Kymenlaakson ammattikorkeakoulu
2015
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Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:amk-2015090314280
https://urn.fi/URN:NBN:fi:amk-2015090314280
Tiivistelmä
MAN Diesel & Turboe SE is a subsidiary of the MAN concern and is specialized on building turbomachinery and diesel engines. The location in Hamburg develops and produces steam turbines with a power range of 1 - 40 MW. Steam turbines are turbomachines which transduce highly heated steam (potential energy) at first into flow (kinetic energy) and afterwards into work (mechanical energy) or by using a gear box with connected generator into electric power (electric energy). Steam turbines are applicable for driving a generator in industry and biomass power plants as well as a drivetrain for pumps, ships or compressors.
The current casing of steam turbines usually consists of an upper and under casing, which is shaped cylindrical. These halves are connected by using bolted flanges. An essential value, which affects the tightness of the flange joint, is the distance between the bolt axis and the point where the resultant force – caused by pressure – is transferred via the cylindrical casing into the flange. The greater distance the more inconvenient is the lever arm for the sealing effect of the bolt. In the case of insufficient bolt force, the flanges will gape on the inner surface of the casing and cause a leakage.
Results from a previous bachelor thesis have shown that the current shape of the casing geometry has only a slightly positive influence on the lever arm and can be improved by modifications of the geometry.
The purpose of the present bachelor thesis is to reduce the distance between the point of origin of the resulting compression force and the bolt axis by improving the casing geometry. Due to this modification the leak tightness will be improved without reducing the bolt force. The mechanical and thermal highly stressed region of the turbine – called wheel chamber – is used representatively for the entire turbine.
The thesis is structured as follows. First of all there is part 2 which puts the problem into the overall context and specifies the evaluation criteria for the analysis. The subsequent chapter 3 is presenting the current geometry together with the investigated variations based on FE-calculation models. Part 4 shows the method for the analysis and the evaluation of the results. Lastly, this thesis is concluding with a perspective in chapter 5.
The current casing of steam turbines usually consists of an upper and under casing, which is shaped cylindrical. These halves are connected by using bolted flanges. An essential value, which affects the tightness of the flange joint, is the distance between the bolt axis and the point where the resultant force – caused by pressure – is transferred via the cylindrical casing into the flange. The greater distance the more inconvenient is the lever arm for the sealing effect of the bolt. In the case of insufficient bolt force, the flanges will gape on the inner surface of the casing and cause a leakage.
Results from a previous bachelor thesis have shown that the current shape of the casing geometry has only a slightly positive influence on the lever arm and can be improved by modifications of the geometry.
The purpose of the present bachelor thesis is to reduce the distance between the point of origin of the resulting compression force and the bolt axis by improving the casing geometry. Due to this modification the leak tightness will be improved without reducing the bolt force. The mechanical and thermal highly stressed region of the turbine – called wheel chamber – is used representatively for the entire turbine.
The thesis is structured as follows. First of all there is part 2 which puts the problem into the overall context and specifies the evaluation criteria for the analysis. The subsequent chapter 3 is presenting the current geometry together with the investigated variations based on FE-calculation models. Part 4 shows the method for the analysis and the evaluation of the results. Lastly, this thesis is concluding with a perspective in chapter 5.