to pressure P |
Introduction
The work produced is due to the gas pressure on the piston. Figure 3 represents the process the piston experiences. Assuming that the pressure in the crank case is atmospheric, then the
gas pressure will be relative to the crank case pressure. _{gas} - P_{crank case}For a small displacement, dx, the work is dW. The following relationship
for dW can be developed: For a finite volume change, work is given by: The work is can also be represented per unit mass of fuel and air,
the specific work. The specific volume is also given by: This work, W, is called the indicated work and will be represented
as W _{b} = W_{i} - W_{f}The mechanical efficiency,,
is defined as: _{b}/W_{i} = 1 - W_{f}/W_{i}The pressure in the cylinder changes during the expansion stroke. First
increasing due to the heat addition, and then decreasing due to the increase
in cylinder volume. We can define a mean effective pressure to determine
the work. A mean effective pressure can be found for the indicated, friction
and brake work. P P P A naturally aspirated Otto cycle engine has a P |

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