Pressure-Time Curve and Work Done for a Compression-Ignition (CI) Engine

by LeeMarie Bocanegra

Submitted : Spring 2012

This project is broken into two parts to analyze certain quantities of a compression-ignition (CI) engine given, recorded pressure data from an electromagnetic pick-up. In order to determine the pressure-angle graph from the recorded values of dp/dθ and θ an approximation had to be made with the application of Riemann Sums. It can be concluded from the data given (dp/dθ and θ) that when graphed, the area under this curve will give the pressure at any angle between -120 ° to 120 °. Then, each measured angle and its corresponding calculated pressure is graphed in an excel sheet to produce the pressure vs. angle graph.

The second part of the project evaluates the work done by the combustion engine between the angles of -120 °and 120 °. The first step is determining the volume of the crankshaft at each angle with the given equation. Once those values are obtained, they are graphed versus the calculated pressures in the first part; representing the pressure vs. Volume graph .The work done by the engine can be analyzed by approximating the area under the p vs. V graph. Essentially the work of the combustion engine is the summation of all the products of the individual pressures and the changes in volume of the combustion engine. The change in volume of the crankshaft is calculated by differentiating the given equation of volume in terms of θ. Riemann sums are used again to approximate the work done by the engine. Once the total work is approximated, it can be converted to horsepower by the conversion factor of 1 hph is equal to 1.98 x 10⁶ ft. lb_f.

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