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In a message dated 1/2/2002 6:40:26 AM Pacific Standard Time, glcasey@gte.net writes:
<<<...FMEP reduction, while desirable, is difficult to accomplish and has only a small
effect...>>>
Gary:
Beg to differ. Agreed, it is (a) desirable; (b) often not so difficult, but (c) CERTAINLY NOT insignificant. Example: by redesigning the oiling system on our development engine, we were able to gain about 15 HP (cruise) and 17.5 HP (takeoff). In another development, a redesigned coolant pump provided an increase of about 4 HP (cruise) with the same (high) coolant flow rate as before. There are more examples. I don't really think those kind of increases are insignificant. 19 HP without any increase in fuel consumption or heat rejection? I'll take that anytime. (And I know certain Winston Cup engine guys who would sell their sainted mothers into slavery for a definitive 4 HP increase.)
That being said, the point of my statement about FMEP was not to present it as an preferable alternative to raising combustion yield. THE POINT was, as stated, to demonstrate that BMEP is not directly related to the combustion process. (George was trying to make a similar point in a different way.)
<<<..the theoretical thermal efficiency of the Otto cycle is inherently linked to the peak pressure since it assume constant-volume combustion...>>>
Actually, the efficiency of a cycle with combustion at constant volume is a function of the ratio V1/V2, the calculated compression ratio (C.F.TAYLOR, IC Engine...., Thermodynamics, Volume 1, Chapter 2). And remember that these discussions relate to an isentropic process with reversible, adiabatic compression and expansion events. Look at the expressions which define the theoretical operation of the combustion-at-constant-volume cycle, and the proposed improvements become more clear.
THanks for your interest.
Jack Kane
LML website: http://members.olsusa.com/mkaye/maillist.html
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