Turbocharger kit

[akirby]

Please stop arguing this, it is a matter of thermodynamics.

 

PV = nRT

 

Pressure * Volume = Average Moleculer Kinetic Energy.

 

P = absolute pressure

V = Volume

n = number of moles of molecules

R = universal gas constant = 8.3145 J/mol K

T = absolute Temperature

 

V has not changed.

n has not change

R is a constant and cannot change

 

So P is directly related to T under our discussion. As temperature decreases the pressure decreases. Thus the turbo is less efficient due to the decreased temperature of the gas when it reaches the turbine. The pressure is a direct result of the temperature.

 

The inverse is true on the intake side of things as we try to increase the volume of gas inside the combustion chamber by maintaining the Pressure and decreasing the Temperature via an intercooler.

 

Or if you prefer we could solve the same via Maxwell Speed Distribution:

 

Vrms = SQRT(3RT/M)

 

Vrms = velocity [root mean square]

R = universal gas constant = 8.3145 J/mol K

M = molar mass

T = Temperature

 

Again the velocity is directly related to the temperature because the mass is held constant under this scenario and R is a constant.

 

The temperature and pressure of the exhaust is based on the initial combustion. Once that leaves the cylinder it's the velocity of the exhaust stream that determines how fast the turbo impeller turns and therefore how much compression is achieved on the intake side.

 

The point was that it's the velocity of the exhaust that turns the turbine and not the heat from the exhaust. You can get the same power from the turbo given a fixed exhaust velocity regardless of the heat of the exhaust.

[BlazedUp]

Hot air or cold air being blown into the pipe to turn the impeller flows at the same rate. The airs velocity is greater at the headers. You want the air entering the engine to be cool, that is why turbo systems require intercoolers. Heat has absolutely nothing to do with the velocity of the exhaut gasses spinning the turbine

[Splitpi]

The temperature and pressure of the exhaust is based on the initial combustion.

 

Which does not change the volume of the gas after it leaves the combustion chamber. It is at peak temperature. Any point after that it is cooling and loosing pressure/velocity.

 

Once that leaves the cylinder it's the velocity of the exhaust stream that determines how fast the turbo impeller turns and therefore how much compression is achieved on the intake side.

 

Once again the velocity is a direct result of the temperature. The mass/volume of the gas is not changing once it leaves combustion chamber. The turbine produces power from the energy. The loss of heat energy leads to reduced velocity which leads to less power generated by the turbine. This is by definition conservation of energy: "The increase in the internal energy of a system is equal to the amount of energy added by heating the system, minus the amount lost as a result of the work done by the system on its surroundings."

 

You and I are saying the results are the same. You are arguing from incorrect stance that violates the laws of thermodynamics however. What I am discussing which IS what is occurring is that power delivered by the turbocharger is result of an isochoric process. I.e. a volume of gas held constant with heat applied [via previous combustion] to increase pressure/velocity. By moving the turbo away from the point of combustion the gas cools and looses energy because the heat energy is lost. NOT because it changed velocity. Velocity is a resultant of the lost heat energy.

 

The point was that it's the velocity of the exhaust that turns the turbine and not the heat from the exhaust. You can get the same power from the turbo given a fixed exhaust velocity regardless of the heat of the exhaust.

 

The point I am making is that the energy in the exhaust that drives the turbine is the temperature of the gas and volume/mass of the gas that left the combustion chamber. The velocity of that gas is derived from that and IS tied to it. Volume does not change so the velocity is a direct result of the temperature.

 

I have shown you the math proving my case. If you disagree please produce a different equation solve it.

 

Heat has absolutely nothing to do with the velocity of the exhaut gasses spinning the turbine

 

That is horribly incorrect. The velocity of the gas is because of the temperature. The reason why the velocity of the gas as it exits the tail pipe is lower than when it exits the combustion chamber is because the heat energy has decreased and there by the resultant velocity decreases. Temperature has everything to do with it.

Edited April 2, 2009 by Splitpi

[BlazedUp]

The reason the exhaust velocity is slower at the tail-pipe is because it is further down the line from the headers. The energy did decrease due to longer travel time! The energy doesn't decrease due to heat loss !!!

 

What type of career field do you work Split...?

Edited April 2, 2009 by BlazedUp

[akirby]

Ok, one more time. Yes, the expansion of the air-fuel mixture in the combustion chamber when it ignites does generate the exhaust pressure (along with some help from the piston compressing the exhaust mixture on the upstroke). So I'll agree with you from that standpoint.

 

However, once the exhaust reaches the turbo, it's the velocity of the exhaust that determines how fast the turbo spins and therefore how much it compresses the incoming air. If you have 10 psi at 40 CFM coming into the turbo then you'll get the same output regardless of whether the incoming exhaust is 400 degrees or 32 degrees.

 

And exhaust velocity is dependent on volume and friction. The smoother the pipes and the less obstructions (bends, mufflers, etc.) the faster the exhaust will flow. But changing the pipe diameter also changes the velocity - smaller makes it go faster and larger makes it go slower. Temperature is one factor that affects volume, so from that standpoint cooling the exhaust will reduce the volume slightly but it's not the only factor.

[BlazedUp]

Cooler air is more dense !!!!!! Stop this discussion now !!!!!!!!!!!

[Splitpi]

The reason the exhaust velocity is slower at the tail-pipe is because it is further down the line from the headers. The energy did decrease due to longer travel time! The energy doesn't decrease due to heat loss !!

 

Time is only relevant to dissipation rate of the temperature. If we had some wonderful miraculous pipe that allows no heat to be lost whether the gas travels 1 inch or 1000 miles in the pipe, the pressure will remain the same. PV = nRT. Anything else will violate the first law of Thermodynamics. It is not a matter of distance. It is a matter of the cooling of the gas in the pipe.

 

What type of career field do you work Split...?

 

Engineer.

[weasel]

Thank you, Splitpi. I was going to dig out my books for this, but you nailed it exactly right. I took Marine Engineering and currently work in the Nuclear industry.

[akirby]

Apparently I was wrong and while I still don't quite understand the concept, I'll yield on this one.

Carry on.