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Pressure Ratio Management model
 The pressure ratio management was developed by Matekunas [1983] and is a
computationally efficient method to determine an approximation of the mass
fraction burned trace xb(θ) at every crank angle θ.
 The pressure ratio is defined as the ratio of the cylinder pressure from a firing
cycle p(θ) and the corresponding motored cylinder pressure p0(θ):
 The pressure ratio is then normalized by its maximum
 The PR has unity value before combustion and rises to a final pressure ratio
during combustion and the increase in the final pressure ratio is called the
modified pressure ratio (MPR)
Pressure Ratio Management model
 The fractional rise in the PR (normalized with its maximum) may be used as an
estimate of the MFB:
 Results:
* Produces traces that are similar to the
mass fraction burned profiles
* The difference between them has
been investigated in [Eriksson, 1999], and
for position PRN(θ)=0.5 the difference
was in the order of 1-2 degrees. This
suggests PRN(θ) can be used as the mass
fraction burned trace xb.