looking for help from the wise (turbo guys, engineers)

[americanjebus]

ok i have a hefty size physics project im taking on and i was allowed to pic my subject, of coarse turbo chargers came up.

now i have to make a presentation explaining all of the physics principles that apply to the turbocharger and the workings of it.

i dotn want people to help write this, im just looking for sites that discuss this, i am having trouble finding writeups of turbocherger physics.

i want to be able to show how a/f ratios directly affect performance and the various applications turbos can be applied to.

im just looking for links to good sites cus damn theres allot of turbo crap i dont need online. i WILL have questions too.

 

[shaeff]

this should give you a headstart:

http://auto.howstuffworks.com/turbo4.htm

-shaeff

 

[americanjebus]

this should give you a headstart:

http://auto.howstuffworks.com/turbo4.htm

-shaeff

already read it over twice, im down to the fundamentals but theres allot that doesnt cover, like how the temperature in a small turbo is rleated to the compressor size at a certain psi vs a bigger turbo running the same psi at a different temp, how could i calculate the temp for a certain size compressor at a certain rpm??? is there a table out there that covers it??

i narrowed down the ingredients for a turbo to work down to:
thermal energy Ie: exhaust gases
centrifugal force: compressor spinning air and throwing it otwards
intertia ; thermal energy having to fight the mass of the turbine + compressor
friction: bearings

wut am i leaving out, my plan is to do a write up for each principle and how it applies to the turbo, am i missing something?

 

[7MGTEJoe]

If you're talking about turbos look in your textbook first. Flip to the chapter on inertia then skip ahead to thermo and look at adiabatic efficiency and the ideal gas law. You can use these concepts to explain how you trade turbo response for compressor efficiency and peak flow.

A/F ratio affects the burn rate. From a chemist's pov you want a stoichiometric ratio so you extract the maximum amount of heat from the reaction. The problem is it's never a homogeneous mixture so you get pockets of air and fuel across the combustion chamber. Where you get a high concentration of air you get a very fast, hot burn. It's efficient but hard on the thin components, namely the rings and valves. Get enough of these air pockets and you can damage the engine so engines run slightly rich to minimize air pockets. In a forced induction application the likelihood of forming these pockets increases so turbocharged engines are run richer than a NA engine.

Turbos are useful any time you wish to radically increase power without adding much weight, significantly increasing the required space or increasing the engine operating speed.

 

[7MGTEJoe]

already read it over twice, im down to the fundamentals but theres allot that doesnt cover, like how the temperature in a small turbo is rleated to the compressor size at a certain psi vs a bigger turbo running the same psi at a different temp, how could i calculate the temp for a certain size compressor at a certain rpm??? is there a table out there that covers it??

i narrowed down the ingredients for a turbo to work down to:
thermal energy Ie: exhaust gases
centrifugal force: compressor spinning air and throwing it otwards
intertia ; thermal energy having to fight the mass of the turbine + compressor
friction: bearings

wut am i leaving out, my plan is to do a write up for each principle and how it applies to the turbo, am i missing something?

Too slow with my first post. The heat issue is tied to the adiabatic efficiency of the compressor at that shaft speed.

 

[Justin]

go buy the book 'Maximum Boost' by corkey bell... its about 30 bucks and I think its exactly what you need.... its FAR over my head

 

[Suprawannabe]

This specificaly fo the 3000 GT turbo but it still give a lot of usefull info.
http://www.stealth316.com/2-3s-compflowmaps.htm

 

[americanjebus]

Too slow with my first post. The heat issue is tied to the adiabatic efficiency of the compressor at that shaft speed.

is this what you were getting at?
http://www.stealth316.com/2-adiabat1.htm

i got that part down and adding it to my applications.

yea im in general phys 101 right now, i read over the whole adiabatic efficiency section and well i'll talk to my teacher if i should get THAT in depth. all i know is im actually gettin into the whole physics thing now. anyway so far all i have resource wise is this.

http://auto.howstuffworks.com/frame...l=http://members.aol.com/TurboHonda/info.html
http://www.stealth316.com/2-3s-compflowmaps.htm

and this is helping ALLOT
http://www.turbobygarrett.com/turbobygarrett/tech_center/turbo_tech103.html

my goal is to come up with a final product/ writup worthy of being in a faq.

 

[Ckanderson]

Do your own HW!!!!!!!!!!!!!!!!............

i kid...

read the corky bell book... thats got graphs and shit....

 

[americanjebus]

Do your own HW!!!!!!!!!!!!!!!!............

i kid...

read the corky bell book... thats got graphs and shit....

i plan on gettin the book, and i AM doing my own homework, note how i said "dont help me write this" im just looking for a direction to read up on, its allot easier to learn something when you have a chance to discuss it rather than just have a book put it ONE way and try to figure it out that way.

imagine having to learn everything about your car having only the haynes manual to read, and no forum to ask questions on or a car to take appart.

 

[Ckanderson]

ha... im just kidding... thats what they say on SF ALL the time!

ill help anyway i can.

 

[souprat]

go buy the book 'Maximum Boost' by corkey bell... its about 30 bucks and I think its exactly what you need.... its FAR over my head

exactly what i was just going to write. the first chapter is all stuff that you can use and after this assignment its just a good book to have anyway. i love it.

 

[americanjebus]

problem is that this thing is due next thurs and i want my research done by this thurs and the book will take an unknown amount of time to get here. im hoping my local libraries will have it otherwise i'll have it ordered overnight shipping by tonight if i can.

 

[7MGTEJoe]

is this what you were getting at?
http://www.stealth316.com/2-adiabat1.htm

i got that part down and adding it to my applications.

yea im in general phys 101 right now, i read over the whole adiabatic efficiency section and well i'll talk to my teacher if i should get THAT in depth. all i know is im actually gettin into the whole physics thing now. anyway so far all i have resource wise is this.

That was what I was getting at, but I was in a hurry and didn't have time to explain very well. A simple way of describing adabatic efficency is how much of you pressure increase is an increase in flow and how much is heat. If you pull up a compressor map there are efficency "islands" (concentric elipses) with the adiabtic efficency written on them. As you move up and to the right (flow and pressure ratio increasing) you'll move up in efficency, peak then fall off. The compressor map for a larger turbo has it's islands shifted up and to the right, meaning they're more efficient at high flow (more air mass, less heat per Kpa).

 

[Ckanderson]

order it on amazon.. youll have it next day....

 

[americanjebus]

order it on amazon.. youll have it next day....

i did, i'll have it in less than 24 hours hopefully,

7mgtejoe: after doing all of the reading on the compressor wheel, i understand the basics of that, but while i wait for the book i have a question about hte turbine wheel, im having trouble puttin the forces used into words, i am at a loss at how to explain how certain engine displacement of air per time is needed in order to spin a turbine of a certain mass to that certain compressor efficiency precentage. hope that made sense.

also where the hell does this compressor efficiency value come from, i am assuming 100% is at the highest psi the turbo is capable of but how can i determine what CE a turbo is running based on its psi and dimensions?

 

[7MGTEJoe]

i am at a loss at how to explain how certain engine displacement of air per time is needed in order to spin a turbine of a certain mass to that certain compressor efficiency precentage. hope that made sense.

Conservation of momentum would be the place to start here. Collisions between the exhaust gas and the turbine transfers momentum. You need a certain number of collisions to get the wheel up to the desired speed. To increase the collisions you need more exhaust flow. This is where engine size and operating speed comes into play.

also where the hell does this compressor efficiency value come from, i am assuming 100% is at the highest psi the turbo is capable of but how can i determine what CE a turbo is running based on its psi and dimensions?

Adiabatic efficiency has very little to do with the highest psi the turbo is capable of. You're on the least efficient island when you're getting the most boost a turbo is capable of making. Adiabatic efficiency is describing the relationship between how much of your pressure increase is due to an increase in temperature and how much is mass. The higher the percentage the more your boost is "worth". If you want to determine CE at a given shaft speed you'd look at the pressure ratio across the turbine and the inlet and outlet temperature.

 

[americanjebus]

ok this should be a generic question but how often does a 4cylinder or a 6 cylinder engine usually go through an exhaust stroke like at idle and at WOT. is like a 1 sec between exhaust strokes at idle or less? and at WOT how many exhaust strokes could there be at say 6k rpm per second???

also approximatly how much would a turbine+shaft+compressor wheel proabably weigh on a standard size say 60 trim turbo?

 

[7MGTEJoe]

ok this should be a generic question but how often does a 4cylinder or a 6 cylinder engine usually go through an exhaust stroke like at idle and at WOT. is like a 1 sec between exhaust strokes at idle or less? and at WOT how many exhaust strokes could there be at say 6k rpm per second???

also approximatly how much would a turbine+shaft+compressor wheel proabably weigh on a standard size say 60 trim turbo?

4 stroke engines have an exhaust stroke every other revolution. You get 1 exhaust pulse per cylinder every 2 revolutions and these are phased to give even power delivery but it's not really necessary to get that detailed if we're just looking at gross flow (V/t).

Engine speed is measured in revolutions per minute, there's 60 sec in a minute and it takes 2 revolutions to get 1 exhaust stroke so you get 1 exhaust cycle per second for every 120 RPM.

I don't know what a turbine weighs; your guess would be as good as mine.

 

[americanjebus]

Engine speed is measured in revolutions per minute, there's 60 sec in a minute and it takes 2 revolutions to get 1 exhaust stroke so you get 1 exhaust cycle per second for every 120 RPM.

durr srry i could have figured that out, but thanks holly hell you know your shit.

just out of curiosity, what do you do for a living? teach physics?? cus your good at it.