BC12D-4-85
SPONSOR
Fairbanks, AK.
MartyC asked me in a PM about my Post#24 - flame speed and burn rate vs air/fuel ratios. Here's a quote from a test paper. Less thermal energy = less power:
"The fuel air ratio has a very significant influence on the
flame speed. The highest flame velocities are obtained
with somewhat richer mixture. When the mixture is
made leaner or richer the flame speed decreases. Less
thermal energy is released in the case of lean mixtures
resulting in lower flame temperature. Very rich
mixtures lead to incomplete combustion which results
again in the release of less thermal energy [Ganeshan ,
2010]."
Also, a simplified pic that shows the ideal air/fuel ratio (Lambda; 14.7:1 A/F, 1.0) versus flame velocity in the combustion chamber. Likely not the main problem discussed here, but it can affect performance. Pre-carb heater days I was told old time pilots would lean the mixture until the slow burning fuel caused a backfire through the carb when the intake valve opened to start a new power cycle, melting some ice if lucky.
"The fuel air ratio has a very significant influence on the
flame speed. The highest flame velocities are obtained
with somewhat richer mixture. When the mixture is
made leaner or richer the flame speed decreases. Less
thermal energy is released in the case of lean mixtures
resulting in lower flame temperature. Very rich
mixtures lead to incomplete combustion which results
again in the release of less thermal energy [Ganeshan ,
2010]."
Also, a simplified pic that shows the ideal air/fuel ratio (Lambda; 14.7:1 A/F, 1.0) versus flame velocity in the combustion chamber. Likely not the main problem discussed here, but it can affect performance. Pre-carb heater days I was told old time pilots would lean the mixture until the slow burning fuel caused a backfire through the carb when the intake valve opened to start a new power cycle, melting some ice if lucky.