12
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Why is using steam to rotate a turbine more efficient?
The main reason is that a turbine requires a pressure drop to extract energy from the working fluid. The drop in temperature that is observed in a turbine is a result of the expansion of the fluid; ...
- 3,044
5
votes
What is the Boussinesq approach?
To take into account the effect of turbulent fluctuations on a flow field, the Navier-Stokes equations are modified to include such effects. The obtained equations are called Reynolds-averaged Navier-...
- 2,160
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votes
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What is the theoretical maximum energy efficiency of hydro turbines?
Something can only be 100% efficient when a lot of generous assumptions are taken into account.
If you assume:
No friction (turbine surface, turbulence, nozzle, or bearings)
Perfect cup design (100%...
- 7,904
5
votes
Accepted
What prevents the use of electric engines to assist with spacecraft launches? (Space Shuttle Booster Supplement)
Electric turbine engines
First off, "electric turbine engines" don't really exist. What you're probably thinking of is an electric version of the jet turbine engine, which is a type of ...
- 1,220
4
votes
Why is using steam to rotate a turbine more efficient?
You are almost describing a gas turbine engine. These are used to generate electrical power, and also to power aircraft. But, in a gas turbine the output of the combustor is at high pressure, and ...
- 257
4
votes
Why is using steam to rotate a turbine more efficient?
Heating water to make steam is not necessarily more efficient, but a lot more practical. What you describe is how internal combustion engines work, for example, so it's a valid concept. However, ...
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4
votes
Question about bounday layer thickness?
The greater the length of the flat plate, the more contact area there is with the fluid. Consequently, the fluid near the start of the plate has had less viscous friction forces acting on it than the ...
- 2,539
4
votes
Accepted
Can combined cycle turbines be small enough for trains?
We can try to answer this question by looking at existing equipment in terms of size and weight and make an educated guess from there if all this fits on a train. Our CC will consist of:
Gas turbine
...
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4
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Why is more steam required to turn a steam turbine when electric power consumption is higher
Because you can't get something for nothing?
If the generator is generating more electrical power then that energy has to come from somewhere.
The more power you try to pull from a generator the ...
- 766
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Practicality of energy recovery from HVAC systems?
So, if I understand correctly you are proposing to use a turbine in the exhaust vents in order to reclaim the energy from the flowing air.
However, in most cases the air is flowing due to forced flow, ...
- 24.3k
3
votes
Why not design a Wind Turbine like an Anemometer?
Because the back of the cups create a lot of drag thereby reducing the power produced.
The blade profile used in classic 3-bladed HAWTs is also used in VAWTs and they look like "egg beaters" needing ...
- 15.5k
3
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Accepted
Why does my model of a wind turbine show high RPM with low power output?
I don't think you really designed a 1300 W wind turbine. You assumed your generator would be able to produce the necessary current but to be able to produce 1300 W you have to build a wind turbine big ...
- 181
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Why don't hydroelectric plants use cascades of turbines instead of single turbines?
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....
- 31
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Why not design a Wind Turbine like an Anemometer?
One other reason is that the propeller-type turbine allows it to be rotated to avoid damage in high winds. When the air is flowing transverse to the axis of the propeller it encounters relatively ...
- 47
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When were airfoil cross-sections first used in turbine blades?
Good description in the link, but curved surfaces were in use as sails around 800 years ago and Bernoulli came up with his formula , Ludwig Prandtl was testing sections in 1017 in his large wind ...
- 15.5k
3
votes
Generating practical power without an iron core, but with high RPM
the iron structure(s) inside a generator serve the purpose of minimizing flux leakage, which maximizes the utilization of the magnetic field in generating electricity. One of the ways in which they ...
- 14.3k
3
votes
What determines the cost of the wind turbines?
Where does the power for a wind turbine come from? Answer - the wind.
So how do you get 15kW from the wind rather than 11kW? Answer - you either need a location with a higher wind speed, or you need ...
- 3,135
3
votes
Accepted
Do 3 blade wind turbines generate more power than a 9 blade, all else being equal?
Because in the real world, all else is never equal, but let's start there analytically.
What does "all else being equal" actually mean?
With respect to a flat swept disk perpendicular to an ideal ...
- 4,607
3
votes
Accepted
How should one clean the blades of a turbomolecular pump
Acetone or other ketones are used to clean auto engine internals of "varnish"( which looks similar to your deposits). This is for research purposes ,not general engine cleaning. The material ...
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3
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Practicality of energy recovery from HVAC systems?
Energy recovery works best when it is a key component of the design. Solar Mikes example. From planning, design, operation and maintenance. Lose one of the four and it will fail.
But as an addon, ...
- 2,467
3
votes
Accepted
Is transmitting windmills' mechanical power to ground level that complex?
TL;DR:IMHO, the driver for keeping the electrical generation closer to the hub is for primarily for eliminating -as much as possible- moving parts for safety concerns. The secondary benefit is the ...
- 24.3k
3
votes
Accepted
Could the St. Louis Gateway Arch be used as a support structure for a giant vertical axis wind turbine?
The arch has been designed to resist wind loads but just the wind load its 630 feet arch can cause.
The motto of not over designing the structure to reduce the weight of the structure to a manageable ...
- 22.1k
3
votes
Doubt on a shaft-turbine-generator system
I am not entirely certain about your question but I think, it basically boils down to this equation
$$M = I \alpha $$
where:
M is the torque applied
I is the mass moment inertia of all rotating ...
- 24.3k
3
votes
Expected power increase when replacing old (>20 years) wind turbines
Wind turbune efficiency is limited to 59% by Betz law
Modern turbines are close to this limit, about 75% of optimum. Older turbines, that are also of the same type, will have almost the same ...
3
votes
Why not build a wind turbine like a vertical Kaplan turbine?
Another reason, is that with hydroplants the water's natural motion is downwards, and its flow can naturally continue.
In the case of air the natural flow is horizontal. Diverting the air would be ...
- 24.3k
2
votes
Which type of Turbine (Pelton, Francis, etc.) is most suitable to be driven by high velocity forced-air jet?
Pelton, Kaplan, and Francis turbines are designed for non-compressible fluids (aka water not air). While they will certainly spin, they would be very inefficient and not what you are after. You will ...
- 7,904
2
votes
Accepted
What is the Boussinesq approach?
The basic assumption of the RANS approach (see the answer by @Algo) is that there is an overall steady solution to the problem. This overall steady solution features small scale oscillations around ...
- 1,192
2
votes
Calculating water turbine mass based on head and flow
For world building purposes, quick interpolation would be sufficient. Fortunately, I have a textbook with some data points.
A 125 MW (HP/LP) two stage turbine has 26" long blades, with a 14' x 14' ...
- 5,343
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Calculating water turbine mass based on head and flow
I am not sure why you would want rotor mass as it much more material dependent than design or power dependent. I have seen kaplan turbines built from both plastic, brass, and steel. Obviously the mass ...
- 7,904
2
votes
How many blades for a steam turbine?
The reason wind turbines use three blades is because it reduces the load fluctuations (fatigue) on the turbine shaft an bearings. Wind at high altitude is faster than the wind at low altitude. A two ...
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