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31

The exhaust gasses are compressible fluids, whereas liquid water is not. Here's an animation of how a gas turbine works: https://www.youtube.com/watch?v=gqNtoy2x5bU At the combustion stage, the gas and compressed air are mixed together, already at high pressure. The burning releases the energy stored in the gas, heating up the released gasses (exhaust). ...

19

Actually the turbine method is very efficient. The Turgo turbine is up to 90% efficient at extracting the energy from the water. Large-scale hydro plants using Francis Turbines can be as high as 95% efficient (see here). Electrical generators typically use high RPMs, so you need speed as well as torque to drive it round. Low RPM generators are possible too, ...

13

There are two different ways for the water flow to transmit energy. One is the pressure difference between the water entering and leaving the turbine. The other the kinetic energy change of fast flowing water entering the turbine and slow flowing water leaving it. Your bucket idea seem to be like a http://en.wikipedia.org/wiki/Pelton_wheel which works by ...

6

What's missing so far is an explanation why you can't expand from high pressure to atmospheric in a single stage gas turbine. There are two types of gas turbines - impulse and reaction turbines. Both face the same problem but it's easier to understand in the impulse turbine. An impulse turbine accelerates the gas through a nozzle from high pressure P1 to a ...

6

The presence of tension in an arch is not really dependent on the curvature but on how well the arch matches a catenary shape. Robert Hooke famously stated: As hangs a flexible cable so, inverted, stand the touching pieces of an arch. So a catenary arch will have only compression stresses (since a flexible cable can only have tension stresses). Notice ...

3

The answer has nothing to do with Bernoulli's equation. A large dam across a steep canyon will define a large catchment volume. It is not uncommon for such a catchment to take as long as ten years to fill to capacity. Even if some of the stored water is spilled each season to furnish some downstream flow, as long as the catchment is in the process of filling,...

3

Shielding them by a dam would have been more costly. And being hidden under a 65 meters deep wall into the water of the Aswan dam would make them visually disappear, and lose their glory. As it is now they preserve the same commanding view and show the perspective the original artisans who designed these monuments had envisioned. . A scale model showing the ...

3

The reason why a hydroelectric generator is fundamentally different to a gas turbine is because water under pressure is not a gas, and does not change size significantly as energy is extracted from it. A gas engine has to account for considerable thermal and volume changes of the gases inside the engine, so multiple parts and multiple materials are ...

3

Water turbines are a major source of electric power. A water turbine generally has only one rotor disk. (from Old Moonraker at Wikipedia) Gas turbines are used in natural gas electric power generators, jet aircraft, and a few other vehicles. A gas turbine generally have lots of rotor disks, which can be divided into two groups: compressor rotor disks and ...

3

Water is going to have to leave the turbine at a speed. That what you've referred to as its residual mechanical power. The thing is, the turbine has already slowed down the water as much as can reasonably be done, while still allowing the water to leave the plant and not flood it. So slowing it down further with an extra stage of turbine just isn't an option....

2

If a dam collapses catastrophically, the entire volume of the lake is released in one 'pulse.' This means the downstream area will be subjected not only to a wave of great height but also of great peak power (energy per unit time). That's a BadThing(TM) . You could look up info on what happened eons ago when Ice-Age ice dams gave way in the Northwest ...

2

Spillways are designed to control the water flow (and excess waterflow) past a dam. Spillway failure could mean a variety of things, but the primary difference is that the spillway is most always located at the upper level of the dam. Water that escapes this area may be damaging, but unlike dam failure, not all the water in the reservoir is going to be ...

2

I suggest that this is not an engineering problem, but a political one. Yes, dams reduce flow downstream when they are filling up, but this isn't a long-term issue. The issue is that once a dam is put in, the dam owners control the flow, and those owners may have different priorities than people downstream. Those priorities include flood prevention, ...

2

Some dams are designed to even out the natural river flow so that the level or height of the river is relatively constant. The natural change in rainfall over time causes a natural change in river height which is fine for nature but, since we have built in many of the floodplains that nature designed then people get upset when they get flooded.

1

This question cannot be answered as it is (without numerical values). The main reason is that you need to determine the pressure Losses due to the pipe length. However the pressure losses are dependent on the type of flow (Laminar or turbulent), which will be dependent on the actual velocity and the roughness in the pipe. Having said the above, the process ...

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