Nonvgt turbines

[09stroker]

A fan doesn't get spun by pressure flowing through the blades. They get spun my a motor....

 

[strokin6L]

Yes i know that.

 

[09stroker]

Then you would agree a fan and an exhaust turbine do not operate the same.

 

[windrunner408]

I would kinda agree, but what about a windmill?? They look almost identical to a fan and they operate like an exhaust turbine. They take movement of a gas and make power. Right?? Why are they 3 bladed vice 2?? Just something I thought about that kind of correlates.

 

[strokin6L]

nope

 

[strokin6L]

I'm not talking about how they are powered. I'm talking about how they move air. A turbine wheel...hell, even a compressor wheel...is nothing more than a multi bladed fan. I was mearly saying how they act similar by moving air with their blades....again, not how they are both powered.

 

[strokin6L]

i guess you can also look at it like this....take the shaft of the turbo with only the turbine wheel still on it. Then stick the other end of the shaft into the chuck of a drill. Pull the trigger and guess what happens....it's gonna move air like a fan will.

 

[09stroker]

The exhaust turbine does not move the exhaust, the engine does. What do you think is gonna happen when you have a 30 blade turbine? Is it still gonna flow more with all else constant?

 

[strokin6L]

If the turbine wheel doesn't do that like you're sayin... then why do turbo's have one?

 

[faster6.0]

Is turbine spool based on drive psi, heat, or both? That's a good one

 

[windrunner408]

Turbine spool is going to be based on how much energy is efficiently transfered from the exhaust gases to the turbine wheel. So while there are A LOT of factors that contribute to the energy possessed in the exhaust gases, I think that heat and straight up flow (lb/min) are going to be two most prominent factors. Of course there really isn't anyway to measure true flow so I guess drive pressure could be used. I would just be careful about that because if the exhaust has a horrible delivery system (i.e. stock up-pipes) then the drive pressure might not be a good indicator for that. Just some thoughts.

 

[faster6.0]

What's going to make more Boost(shaft rpm) nate, 50 psi of drive psi @1600 degrees or 50 psi of drive psi at atmospheric temp?

 

[windrunner408]

50 psi of drive @ 1600F will spin the shaft faster (of course this is with all other things being equal) because as the hot gases go over the blades, the energy contained in the heat of the exhaust gas will be transferred to the blade and the temp coming out of the turbo will be lower than 1600F. This is why it is better to monitor EGTs pre-turbo than post turbo.

 

[faster6.0]

Are the volumes of gases equivalent to spool the turbo however between the two temperature examples? Does the Room temperature 50 psi contain the same amount of volume as 50 psi at 1600? Which pressure/temperature combo is most efficient at flowing the most volume Is my question.

 

[TooMuch03]

I would kinda agree, but what about a windmill?? They look almost identical to a fan and they operate like an exhaust turbine. They take movement of a gas and make power. Right?? Why are they 3 bladed vice 2?? Just something I thought about that kind of correlates.

Why do they have 3 blades and not 4?

I think there is more to it than just blade count, but I find it very difficult to believe that the 13 blade wheel would flow better than a 10 blade wheel. It makes sense that it spools better, but then the drive pressure is also higher, so it wouldn't flow better. I'd have to see flow numbers to be convinced otherwise.

 

[windrunner408]

I wouldn't think that the volume of gases are equal at all (gas laws); but in general, hotter gases are going to contain more energy in them than the colder ones at a given volume and pressure (even though the mass of gas will be different between the two). Any time you do an energy balance calculation there is always some energy transferred due to temperature. It may be small in comparison to the volume/mass of gas flow but like I said, the difference in the amount of mass of gas (for the given volume) is also small and I believe it is a smaller contributing factor than the temperature and therefore you will gain more from a higher temperature gas at a relatively higher temperature than a lower temperature gas. Again this is all just a general rule of thumb. As far as what pressure is more efficient at spinning a turbo than any other pressure goes, it is my opinion that that has more to do with blade design and wheel trim than anything else. As pressure is really just a measure of the velocity of the gases hitting the turbine where the wheel trim is going to determine how efficient that turbine is at transferring that energy into rotating the wheel.

 

[windrunner408]

Why do they have 3 blades and not 4?

I think there is more to it than just blade count, but I find it very difficult to believe that the 13 blade wheel would flow better than a 10 blade wheel. It makes sense that it spools better, but then the drive pressure is also higher, so it wouldn't flow better. I'd have to see flow numbers to be convinced otherwise.

Couldn't tell you but since it was mentioned the talk about fans, I just brought up a similar application.

Again, I too would agree that fewer blades are going to allow for more flow to slip past them than more blades and therefore be less efficient at transferring the energy from the exhaust gases than a higher blade count wheel. This means that a higher blade count wheel will, in general, spin easier than a lower blade count wheel of the same dimensions and mass. I mean let's face it, if you have more blades then you have more surface area and if you have more surface area, you are going to have more interaction with the exhaust gases and more opportunity to get the wheel to spin sooner and depending on the efficiency of the wheel, the difference in top end flow, and drive pressure may very well be nominal at best. I'll tell you what. I think I may have a way to test this to see what is what. I will get an 03/Pmax turbine housing and will build a turbo that can be manipulated to be either a regular 10 bladed Pmax, 13 bladed Pmax, 10 bladed LLY turbo, or a 13 bladed LLY wheel. I will monitor peak drive pressure, peak boost, peak EGTs, peak IAT, and peak MAF. Anything else I should monitor??

 

[09stroker]

Why do they have 3 blades and not 4?

I think there is more to it than just blade count, but I find it very difficult to believe that the 13 blade wheel would flow better than a 10 blade wheel. It makes sense that it spools better, but then the drive pressure is also higher, so it wouldn't flow better. I'd have to see flow numbers to be convinced otherwise.

Because engineers don't mind a 30 min spool up