# Tag Info

## Hot answers tagged turbines

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, ...

14

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 ...

12

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; the turbine doesn't have a way to extract the heat energy directly from the fluid. The total work done by the fluid is typically expressed as a change in ...

7

While "conventional turbines operate by imparting impulse or reaction energy from an incoming fluid using "buckets" or spiral surfaces on the turbine "runner", a "Tesla Turbine" is a bladeless or "drag turbine". A Tesla turbine's disks are bladeless and essentially smooth and the "drag" from boundary ...

6

You are describing a very interesting engineering problem. The requirement of a turbine is to convert fluid-energy into mechanical energy over a range conditions. Since the flow around the airfoils is governed by the (elliptic) Navier-Stockes-Equations, an easy answer to your question is not possible in general. Only in certain edge cases it is possible ...

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 ...

5

Given that water is roughly 1000× as dense as air, and incompressible besides, it should be fairly obvious: A wind turbine would be destroyed by the forces that water would put on it, and a water turbine wouldn't even notice the forces created by wind.

5

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-Stokes (RANS) equations. As an example, the steady incompressible momentum equation can be written as follows (in Einstein tensor notation): $$\rho \frac{\... 5 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 combustion engine (it burns fuel). Air is sucked in the front, compressed by a compressor, then mixed with fuel and burned in a combustion section. A turbine ... 5 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% 180degree jet reversal) A dry wheel (no water is spun off) Not counting the gravitational potential to drop the water away from the wheel in the efficiency ... 4 It's a trade-off between the simplicity of the sensor and how comprehensive the reported data is. The locked rotor sensor only reports whether or not the motor is spinning, not how fast it's spinning or how much resistance is on the fan. It is a very simple signal though, it's either on or off. On the other hand, the tachometer signal is a bit more ... 4 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, they do this in bursts and use liquid and carefully engineered fuel, which makes the implementation more practical. In a continuous system as you describe, the ... 4 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 end of the plate. So, the end of the plate has more fluid slowed down than the front. The width of the boundary layer must necessarily increase with the ... 4 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 harder it becomes to turn the generator. If it's harder to turn the generator then you need to push harder on the turbine driving it. The way you push harder on the ... 4 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 Exhaust HX/Boiler Steam turbine with condensor and other aux. parts Transmission For the following, I will not match components exactly, but pick stuff that ... 4 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, if you use a turbine to "suck" energy out the air then it tends to slow down. So then you would probably need to use bigger fans to push the air. So ... 3 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 enough, given its efficiency. At C_p=0.3 and v=10\ \mathrm{m/s}, you simply need an area of:$$A=\frac{2P_T}{C_pv^3\rho}=7.07\ \mathrm{m^2}\...

3

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 that is used to turn a turbine. And, that is a different combustion cycle from a steam cycle.

3

The design looks like a Savonius turbine, but horizontally mounted, instead of the typical vertical mounting that you see with this design. I'm really not sure why this would be mounted this way either, as one of the key benefits of the Savonius design is that it's never not facing the wind. The bottom of the Wikipedia article mentions that the horizontal ...

3

Reading through the site I would say no. Using the exhaust gas as input for the turbine will have horrible efficiencies for powering everything he listed. Also, on the "How turbochargers work" page he stated that he uses the compressed air from the turbocharger to directly power a turbine. A turbine and a compressor can be thought of as opposite cycles of ...

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....

3

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 top and bottom bearings. The engineering complications of VAWTs make the 3-bladed HAWT much more popular also due to the power output, rotating mass and visual ...

3

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 little drag. It would be hard to imagine an orientation that would allow the anemometer-type design to avoid this.

3

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 tunnel, the first naca section was tested in 1935 .... http://www.flyingmag.com/technicalities/technicalities-short-history-airfoils And this link to Sir Frank ...

3

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 accomplish this is by furnishing what is called a return path for the lines of force, so as to "close" the magnetic circuit inside the device. For things ...

3

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 to pick up more wind, i.e. the blades need to be longer. How does this affect cost? Answer - a longer blade needs more material for its extra length. But then ...

3

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 fluid with a uniform free stream flow field, from Momentum Theory, the induced flow field associated with optimum performance has slowly been specified in ever ...

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