Читать книгу Internal Combustion Engines - Allan T. Kirkpatrick - Страница 63

The above parameters are entered into the computer program BurnFraction.m as shown below, and the resulting plots are shown in Figures 2.16 and 2.17.

Comment: Note the asymmetry of the burn rate, as a result of the form factor value, and the peak value of the burn rate at 18 atdc. As discussed in more detail in the next example, optimal work from an engine usually occurs with a peak burn rate a few degrees after top dead center, so a significant fraction of the combustion will occur during the expansion process.

function [ ]=BurnFraction( ) This program computes and plots the cumulative burn fraction and the instantaneous burn rate. a = 5; Wiebe efficiency factor n = 4; Wiebe form factor thetas = -20; start of combustion thetad = 60; duration of combustion ....Burn fraction curve for Example 2.4. Rate of energy release curve for Example 2.4.