Sam Grucky

5/7/09

Footnote 18

Fake Turbo

The idea behind this footnote 18 is to start a hands on project involving my car that could eventually turn into my honors thesis/creative project. I have always dreamed of building a completely new chassis, suspension and power train for my 1992 Volvo 240. Even though I am a long way away from making these modifications it is very interesting to see how so many concepts learned in MAT 276 can be applied to the engineering behind a car. The focus of this project is to calculate the work a particle does as it travels around an idealized path within a made up turbo charger. The dimensions of this fake turbo are based on the maximum volume under the hood with the existing sized engine. This

A turbo charger uses the air pressure from exhaust gases to rotate a fan attached to a compressor. The goal of this mechanism is to increase the amount of fuel per unit volume. Basically, the compressor makes the air denser which allows more fuel molecules mixed with the air molecules to enter the combustion chamber. By doing this, the power yield from an engine can be greatly increased.

To apply the skills learned in this class, I have simplified the design of the turbo charger to make the work calculations easier. Not only this but the force relationship between the air molecules from the exhaust spinning the fan and the amount of air molecules sucked in through the compressor will be modeled using arbitrary functions. In real life, as time increases, the amount of exhaust pressure from the engine increases, thus the whole system will experience some net change in power according to some function that depends on exhaust flow. Not only this but another assumption is that fan blades and the compressor blades are mass-less and therefore do not resist the force of the air molecules. Though many parts about this project have been simplified, the only part of this project that would change is the force function for the air flow. So even though this system has been greatly simplified, the overall concepts of how to calculate the amount of work within a turbo stay the same.

For the exhaust section of the turbo charger, I chose to model the amount of force from the engine exhaust gases as r₄=2t²+4t. This parabolic relationship is an arbitrary assumption based on the fact that as time increases the amount of pressure from the exhaust gases will increase according to some mathematical model. Furthermore, the function r₂= e^t was chosen to model the force of the compressor as time increases just to make the integrals in this project a little more interesting.

After computing the work integrals the results were 10.75 lb*in for the two inch linear section of the exhaust, 366.5 lb*in for the complete circle section of the exhaust, 493.2 lb*in for the section of circle of the intake part and 6.87 lb*in for the linear section of the intake. Though these results don’t apply to anything in real life it is interesting to see the vast difference in the amount of work a particle does traveling in a straight line compared to one that travels in a circular path.

In the end, this project has made me think realistically about the actual processes that take place within a turbo charger in order to increase the power output of an engine. At this point in time there are a plethora of turbo chargers on the market that have been specifically designed to maximize the output of an engine. In my project the only part this system that was maximized was the volume that the turbo could take up underneath the hood. In the future this project may be used as a platform for creating an actual 1992 240 turbo charged bio-diesel.

Below are the design layouts and calculations for work: