Pressure after a water turbine

[Pim_Verwoerd]

Homework Statement

Pressure loss due to turbine

Relevant Equations

P = Q * dP. Bernoulli

For an engineering project we have to make an energy storage system. We thought of something like a hydro dam. We were having a discussion about the pressure after the turbine in the hydro dam. The water immediately flows into the atmosphere ( so it falls down into a lake ). Can we then safely assume that the pressure over there is the atmospheric pressure? Or is there a different pressure field because of the turbine?

 

[gmax137]

I think it depends on the actual configuration. Does it have a submerged tailrace? Then not Patm.

 

[berkeman]

I think it depends on the actual configuration. Does it have a submerged tailrace? Then not Patm.

That's interesting. Why would you discharge below the surface of the river? It seems like you'd want to maximize the pressure drop across the turnbine...

 

[Pim_Verwoerd]

I think it depends on the actual configuration. Does it have a submerged tailrace? Then not Patm.

View attachment 289165

No it doesn't have a submerged tailrace. The water that comes out of the turbine comes out into 'clean' air.

 

[gmax137]

No it doesn't have a submerged tailrace. The water that comes out of the turbine comes out into 'clean' air.

Then the pressure (in the clean air) is atmospheric. It can't be anything else.

 

[Tom.G]

That's interesting. Why would you discharge below the surface of the river? It seems like you'd want to maximize the pressure drop across the turnbine...

If the discharge is in the river then the pressure difference would be the difference between the reservoir water level and the river water level.

The head increase from a lower discharge is offset by the river water above the discharge.

If the discharge is above the river, the pressure difference is the difference between the reservoir water level and the discharge level.