This video shows the nett transient effect of rapid closure of the turbine inlet valves and extended opening of the turbine bypass valves, in response to a steam turbine power failure event. At a time of 0.1s into the simulation the turbine inlet valves commence closure with a stroke time of 90ms, whilst at the same time the turbine bypass valves commence opening with a stroke time of 2.50s.
The steam hammer system extends from the outlet of the boiler superheater to the inlet of the steam turbine. The superheated steam exits the boiler at a temperature of 550 degC and a pressure of 260 bar abs and passes through the system at 2400 t/hr and a density of 85 kg/m3. In sections of the system the steam velocity is as high as 50m/s.
It can be seen that there is a pronounced Joukowsky-type peak pressure rise on the upstream side of the turbine inlet valves consequent to their rapid closure, which is subsequently followed by further peak pressure rises due to linepack in the pipeline as the boiler continues to input steam into the system. Due to the extended opening stroke time of the turbine bypass valves they offer little in the way of surge relief for this system. Their main function is to limit the effects of continued linepack in the pipeline and therefore prevent excessive over-pressurisation.
Simulation Summary: Key Transient Information
- Turbine power failure event at 0.1s
- Turbine Inlet Valves commence rapid closure at 0.1s (stroke time = 90ms)
- Turbine Bypass Valves commence extended opening at 0.1s (stroke = 2.50s)
- Single phase mathematical model with full transient heat transfer calculations
- High Pressure / High Temperature Superheated Steam
- Steam properties and Equation of State consistent with IAPWS – IF97
- Surge analysis included determination of peak pressure envelope and out of balance loads