Saugrohr
Mechanical
- Aug 6, 2008
- 2
Dear all,
I am sure that someone could explain me what is the physic behind the following case (see doc enclosed).
I am doing transient calculations on a pump storage powerplant (2x170 MW Francis pump-turbine). This is a variable speed pump-turbine and in pump mode we can adjust the operating point with its wicket gates.
In pump direction I have a problem with the pressure in the suction side (inlet of pump) during trip-off (wicket gates closing quickly to avoid overspeed). It reaches excessive pressure.
In order to down the pressure in the pump inlet, I tried several closing times of the wicket gates in order to find an optimum closing law to prevent high pressures in the suction side. But, closing the wicket gates in 10 sec, 20 sec,30 sec, 40 sec give me similar pressure peak and no improvement is found.
By checking the change of the discharge in the pump (dQ/dt), for every closing time I found that this slope is constant for every closure until the discharge stops and goes in turbine direction.
According to these results I suppose that the waterway dimensions is governing the pressure, and no modification of closing time will have influence on these pressure peaks.
Somebody has an explanation?
Bye friends.
I am sure that someone could explain me what is the physic behind the following case (see doc enclosed).
I am doing transient calculations on a pump storage powerplant (2x170 MW Francis pump-turbine). This is a variable speed pump-turbine and in pump mode we can adjust the operating point with its wicket gates.
In pump direction I have a problem with the pressure in the suction side (inlet of pump) during trip-off (wicket gates closing quickly to avoid overspeed). It reaches excessive pressure.
In order to down the pressure in the pump inlet, I tried several closing times of the wicket gates in order to find an optimum closing law to prevent high pressures in the suction side. But, closing the wicket gates in 10 sec, 20 sec,30 sec, 40 sec give me similar pressure peak and no improvement is found.
By checking the change of the discharge in the pump (dQ/dt), for every closing time I found that this slope is constant for every closure until the discharge stops and goes in turbine direction.
According to these results I suppose that the waterway dimensions is governing the pressure, and no modification of closing time will have influence on these pressure peaks.
Somebody has an explanation?
Bye friends.
