Re: cr equation

["Nick Pashley" <NickPashley@xxxxxxxxxxxxxxxx>]

Internal combustion engine compression processes are modelled as isentropic
(constant entropy), sub models will account for heat transfer and leakage
(modelled by an isentropic efficiency).  The equation for isentropic
compression is:

PV^k = constant

P = pressure (absolute)
V = volume
k = ratio of specific heats = 1.4 for air or approximately 1.3 for
combustion products (on the expansion stroke) or between 1.3 and 1.4 for
idle cos there is a high proportion of exhaust gas.  The ratio of specific
heats is a function of atoms per molecule, close to 2 for air (O2 and N2),
higher for fuel air mixtures (including CxHx for a fuel - for gasoline
C8H10ish [18 per molecule]) and decreasing after combustion (CO2, H2O, N2,
O2, CO, CxHx).  Whatever the cycle, the dominant molecule is nitrogen.

Interesting books to read on the subject are:

Internal Combustion Engine Fundamentals        J Heywood        McGraw-Hill
Introduction to Internal Combustion Engines    C R Stone
Macmillan
Internal Combustion Engines                            C R Ferguson
John Wiley and Sons

This is second year engineering degree thermodynamics, there must be course
notes on the net somewhere.

Nick Pashley

> Date: Fri, 26 Jan 2001 22:12:19 -0500
> From: Brian Mentiplay <bmentiplay@domain.elided>
> Subject: cr equation
>
> >From: tedcrum@domain.elided
> >Subject: cr equation
> >To: bmw@domain.elided (bmw group submissions)
> >Date: Fri, 26 Jan 2001 09:09:17 -0800 (PST)
> >
> >Nobody's gotten close yet. There's an exponential term.
>
>            k                        aP
> Not like PV ?  A term of the form Ce   perhaps?  Don't leave us hanging.
:-)

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