Engineering Analysis for Group 26
Revision as of 14:28, 7 December 2009 by MAE277 26 09
- During the analysis of the engine the many parts made it difficult to choose which to use. After the analysis problem, the key component of the engine that would require a lot of analysis is the Piston and Cylinder of the engine. There are many important parts that require discussion about the chosen design and testing that would need to be done to make this part work efficiently.
- As an engine runs the piston moves up and down the cylinder constantly driving the camshaft and converting chemical energy into usable mechanical energy. As the gas expands in the chamber a large amount of pressure is exerted onto the piston forcing it down. Despite this large pressure none of the gas leaks around the sides of the piston thanks to the piston rings. Because of the sizable force pushing the piston down the piston rings must fit tightly against the sides of the cylinder. This tight fit causes friction along the sides of the cylinder. This is a place where some of the largest energy loss occurs.
- The equation for friction ( Ff=μ*Fn ) shows that the force of the piston pushing into the wall (Fn) greatly affects the amount of friction. One way to test Fn is to measure the force needed to pull the piston out of the cylinder. Once you find the force of movement using the equation F=ma it is possible to solve and find Ff (friction force). After this data tables readily supply the coefficient of friction (μ) and it is simple to solve for Fn. As can be seen a large amount of force can be lost from the system due to friction.
- Two ways in which to decrease the Ff are usually the easiest to pursue. The most obvious is to decrease the coefficient of friction by changing the material or adding oil into the system. The other way to decrease Ff is to change the Fn which can be done by decreasing the pressure of the piston rings.
- The point of these tests is to bring the efficiency of the engine closer to that of a perfect engine that does not lose energy due to friction.