Research on Calculation Method of Governing Stage Off-design Conditions in Consideration of Governing Valve Overlap Degree

摘要

The calculation method of steam turbine's stage off-design conditions is an effective means to realize the security and economical efficiency, but at present, research on the calculation method of governing stage off-design conditions in consideration of overlap degree seldom can be found in documents. In order to ensure the lift-flow characteristic curve of governing valve is a continuous smooth curve and approximation to a straight line in steam turbine with nozzle governing, there will be a certain degree of overlap among each governing valve on and off. There is not any consideration about the mentioned point on the calculation method of conventional governing stage off-design conditions, and the simplification leads directly to the calculation results of governing stage off-design conditions inconsistent with the actual running process. Therefore, it is very necessary to do some improvements on methods of calculation. The calculation method of governing stage off-design conditions in consideration of overlap degree is shown in this paper, and we verify its accuracy by the calculation example basing on 600MW steam turbine.