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Abstract |
A specific heat ratio model for single-zone heat release models
The objective is to investigate models of the specific heat ratio for the single-zone heat
release model, and find a model accurate enough to introduce a
modeling error less than
or in the order of the cylinder pressure measurement noise, while
keeping the computational complexity at a minimum.
Based on assumptions of frozen mixture for the unburned mixture and
chemical equilibrium for the burned mixture, the
specific heat ratio is calculated using a full equilibrium program
for an unburned and a burned air-fuel mixture, and compared to already existing and newly proposed approximative models of $\gamma$. A two-zone mean temperature model, Matekunas pressure ratio management and the \Wiebe function are used to parameterize the mass fraction burned. The mass fraction burned is used to
interpolate the specific heats for the unburned and burned mixture,
and then form the specific heat ratio, which renders a small enough modeling error in $\gamma$. The specific heats for the unburned mixture is captured within 0.2 \% by a linear function, and the specific heats for the burned mixture is captured within 1 \% by a higher-order
polynomial for the major operating range
of a spark ignited (SI) engine.
Marcus Klein and Lars Eriksson
SAE Technical paper series SP-1830, 2004
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