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5 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%...
ericnutsch's user avatar
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5 votes
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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 ...
BarbalatsDilemma's user avatar
4 votes
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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 ...
mart's user avatar
  • 4,791
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 ...
Paul's user avatar
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4 votes

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 ...
Andrew's user avatar
  • 766
4 votes

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....
Da bishop's user avatar
4 votes

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, ...
NMech's user avatar
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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 ...
AndyT's user avatar
  • 3,143
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 ...
niels nielsen's user avatar
3 votes

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 ...
Solar Mike's user avatar
  • 15.9k
3 votes

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 ...
Angus Murray's user avatar
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 ...
Solar Mike's user avatar
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3 votes
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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 ...
Phil Sweet's user avatar
  • 4,820
3 votes
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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 ...
blacksmith37's user avatar
  • 6,162
3 votes

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, ...
StainlessSteelRat's user avatar
3 votes
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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 ...
NMech's user avatar
  • 24.4k
3 votes
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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 ...
kamran's user avatar
  • 22.6k
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 ...
NMech's user avatar
  • 24.4k
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 ...
Surprised Seagull's user avatar
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 ...
NMech's user avatar
  • 24.4k
2 votes
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Does the turbine outlet affect the power generated by the turbine ?

The turbine referred to, in your text book must be a specific type of turbine, namely reaction turbine. Reaction turbines utilise mainly the pressure energy of flowing water to produce Power. The ...
Pranav's user avatar
  • 349
2 votes

Estimating wind velocity behind a wind turbine

The wind behind an operating turbine is turbulent. So no, there is no straightforward formula for calculating a more realistic estimate of the wind velocity behind a turbine. The existence of such a ...
410 gone's user avatar
  • 3,771
2 votes
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What is the difference between a diffuser and a duct in turbines?

A definition of a diffuser is: "The (divergent) diffuser is a duct so shaped that the fluid flowing through it decelerates, the pressure increasing from inlet to outlet." This is from Engineering ...
Solar Mike's user avatar
  • 15.9k
2 votes

Tesla's Turbine in Real Life

An inspection of his patent reveals that his pump relies on the viscosity of the fluid to perform work- that is, the fluid is coupled to the impelling cylinder by shear forces alone. This means the ...
niels nielsen's user avatar
2 votes

Gasturbine energy balance

energy flow rate towards turbine after compression and combustion is 12MW (chemical energy of fuel + compression energy of compressor). Energy extracted by turbine is 9.3MW. Efficiency of turbine 9.3(...
SRD's user avatar
  • 187
2 votes

Do 3 blade wind turbines generate more power than a 9 blade, all else being equal?

Very basically in modern wind turbines which act as a wing and get lift, if you add too many blades because of the wake interference you will get kind of a stall in lift because you will develope a ...
kamran's user avatar
  • 22.6k
2 votes

What is the purpose of combustor in a gas turbine

The turbine blades are what turns the compressor blades in the first place. They do this by extracting work from the hot gas shooting out of the combustors at high speed, and feeding it forward on a ...
niels nielsen's user avatar
2 votes

Practicality of energy recovery from HVAC systems?

Yes, this is possible. Where I work, there are several very large fridges and freezers. The energy removed keeping them cool is pushed into a water tank that is the pre-heated water feed to the boiler,...
Solar Mike's user avatar
  • 15.9k

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