Effectiveness of the BURNING PROCESS in NON-KNOCKING Engine Explosions - (The Use of Thermodynamic Charts in the Analysis of Flame-Picture and Pressure Data) 400175
COMBUSTION was found to be approximately 81% effective in five different explosions which were recorded by means of high-speed motion pictures and pressure cards while running the engine on iso-octane and benzene, the authors report. The term “81% effective,” they explain, means that, according to modern thermodynamic data, only 81% of the liberated heat energy is accounted for by the pressures observed during combustion; in other words, 19% of the liberated heat energy is apparently lost from the working fluid.
The flame-picture and pressure data together with the Hottel thermodynamic charts make possible a comparison of the actual rate of inflammation of the charge with the rate of combustion required by the thermodynamic analysis for developing the observed pressures. These two rates of combustion are approximately equal during the inflammation of the first 10% of the weight of the charge and during the inflammation of the last 50%. They differ markedly when the actual rate of inflammation is a maximum, and this value is attained in the present engine when from 25 to 40% of the weight of charge is burned.
As the actual rate of inflammation of the charge reaches and passes through its maximum value, most of the 19% of the liberated heat energy that is not accounted for at the end of the burning period disappears from the working fluid. The apparent energy losses occur in time intervals equivalent to from 2 to 7 crankshaft deg. in the five explosions reproduced herein. The flame pictures show that the intensity of the afterglow radiation increases sharply during the period in which the apparent energy losses occur.
Citation: WITHROW, L. and CORNELIUS, W., "Effectiveness of the BURNING PROCESS in NON-KNOCKING Engine Explosions - (The Use of Thermodynamic Charts in the Analysis of Flame-Picture and Pressure Data)," SAE Technical Paper 400175, 1940, https://doi.org/10.4271/400175. Download Citation
LLOYD WITHROW, WALTER CORNELIUS
Research Laboratories Division, General Motors Corp.