This is about a double flash steam power plant. The turbine configuration says that it has one inlet for high pressure steam and another for low pressure steam. I don't follow how this works so I might just ask here hoping for quick, straight answers. Just 1 turbine. And if someone answers that it runs on 2 or more stages, how does multi stage happen for a turbine? I understand the entire thermodynamic cycle for this, but this turbine. I need to compute for power output from given data and diagram but then again, I don't know if these two mass flow rates of steam expand all at once or do they expand one after another or does the high pressure steam expand on the low pressure 'other steam'?
Jan,
I can offer some points in the context of geothermal applications.
The HP brine is flashed first to generate some HP steam, following which some of the fluid at relatively low pressure remains.
In double flash generation systems, the remaining fluid is separated by a separator, and flashed again - this time to produce LP steam.
Thus the geothermal source is made to work as two sources of steam - differing in enthalpy. The turbine system will accordingly admit the steam at two points or stages.
Here is an interesting document that could help you with the basics:
http://www.geothermal-energy.org/pdf/IGAstandard/SGW/2013/Pambudi.pdf
It explains the exact difference in the parts of the Rankine Cycle that each flash works with, without going into too much detail.
Hope it helps.
-Sanjay
the HP steam enters in the turbine and expands in the HP pressure stages (can be 1, or several) down to the pressure of the LP inlet. Then the HP and the LP streams mix at constant pressure (the one of the LP stream) and the whole flow rate (HP+LP) expand down to the condensing pressure. The power output is the sum of HP stages (HP flow rate*HP enthalpy drop) and LP stages ((HP +LP) flow rate*LP enthalpy drop.
When the working conditions change, the turbine is capable of self-adapting to the new conditions, by adjusting the LP pressure.
Hi, One cannot introduce two different streams at the same plane in a turbine. The flow would reverse in the low pressure one. The way something can be done is by introducing the lower pressure fluid after on or more stages of the turbine. Only works for a multistage machine but most are. Find a stage where the exit total pressure is below the low pressure air: here flow can be injected. There will still be some mixing losses due to the remaining differences.
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