Royce Wise wrote:

Paul, anyone else know how many degrees ATDC (ATC) on the power

stroke that the

combustion process is pretty much spent? Put another way, how many

degrees ATC

before the power of the charge is no longer propelling the rotor.
Royce

Never mind, I found the answer on Paul Yaw's site.
Royce

What was the answer Royce?

Paul Lamar

90ø ATDC The expansion cycle has started, and is already 45ø past the

point of maximum

torque transfer to the eccentric shaft, which occured at 45ø ATDC.

 135ø ATDC The expansion stroke continues, but the torque transferred to

the output

shaft is now down to about 35% of its peak.

 180ø ATDC The exhaust port is still closed, and the torque transfer to

the eccentric

shaft is approximately 15% of its peak.

 225ø ATDC At this point, the exhaust port has been open for

approximately 30ø, and

exhaust flow is quite high.

Royce

In the theoretical Otto cycle (classic spark ignited 4 stroke) the
combustion process
is complete, instantaneous, at TDC. In an actual engine the combustion has
started before TDC, and is probably complete after about 15 to 20 degrees
of crank angle (1.5 times that for eccentric rotation). All of this
combustion
time reduces cycle efficiency (the Diesel cycle is less efficient than the
Otto cycle because of the assumed constant pressure heat addition - ie
combustion as the injection process continue). In the real world the P/V
curves are very similar  - about between the two theoretical cycles.
It would be benificial if you could continue work extraction expansion
to a greater volume thab BDC - but mechanizing this is quite difficult.
It would be like the second expansion cylinder of a steam engine -
and a compromise is the turbo compound engines. _- Vance J

 
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