It's lucky we've got so many experts on this forum especially in the field of chemisty. I on the other hand have only the basic high school level.
If you look at the first minute of so of this video, you'll see the flame changing colour due to the mixture of the fuel and air being burnt. If there is exess fuel in the mixture it will be a highly visible yellow flame, if it's the mixed fuel/air at the correct ratio it will be blue but almost invisible.
In Olegs video we a an engine that has just been started. From the video shown the engine is barely ticking over.
Now the merlin engine had what's called a high overlap cam shaft, which means that the inlet and outlet valves are open at the same time for a long time durring the otto cycle. (It allows fresh fuel air mix to enter the combustion chamber at the same time as the last of the exahust gasses leave the combustion chamber.) This makes the engine more efficient within the engines power band BUT at low revs the engine engine runs rough due to incomplete burning of the fuel air mix in the combustion chamber. It's what known as a 'Lumpy Cam' in automotive circles. It means at low revs there is a lot of unburnt fuel in the exhaust gasses.
Now I know some people here want Oleg to demonstrate a 'Blue Flame' in an update video. I for one, most emphatically, do not want to see this!
Cheers!
