Sean Trost wrote:
I stand corrected. Thanks Jim. Learned somthing new everyday.
Sean

Jim Carriere wrote:
Sean Trost wrote:

Juan
I believe that N1 is related to the velocity of the airstream
introduced. Which is good. But not related to the ignition problem
Now You have said that you have an excellent spark and good fuel. the
only other thing you need for start is the right airflow. or volumn.
Dont know about your engine specifically but most everything else runs
right around 14 to 1 on the ratio wise.


Actually, jets are a different beast from piston engines. Between about
25:1 and 50:1 is normal, even for lightoff fuel flow. Stoichiometrically
correct combustion is too hot.

50:1 would be the total airflow:fuel ratio through the engine core. Of
those 50 parts air, 15 are primary air that mixes with the fuel for
stoichiometrically correct combustion.

The other 35 parts are secondary air (not to be confused with a turbofan's
bypass air, which doesn't pass through the core). Some secondary air passes
around the exterior of the combustion chamber liner to cool it, and some
passes through holes into the chamber to shape the flame and hold it away
from the liner wall to prevent damage.

None of this is impingement starting air, which hits the turbine blades and
then goes right out the exhaust duct.