Design and Simulation of Two Stroke Engines

Design and Simulation of Two-Stroke Engines
particle flow direction
(a) non-isentropic expansion
s1
s2
s1
O/
^
s2
(b) isentropic contraction
Fig. 2.10 Particle flow in simple expansions and contractions.
turn equation. The properties and composition of the gas particles are those of the gas at the
upstream point. Therefore, the various functions of the gas properties are:
Y = Yi R = Rj G5 = G5i G7 = G7j , etc.
The continuity equation for mass flow in Eq. 2.9.5 is still generally applicable and repeated
here, although the entropy gain is reflected in the reference acoustic velocity and
density at position 2:
This equation becomes:
m1-m2=0 (2.10.1)
.G5
rG5
Pol** A^saoi&i " Xrl) + Po2X£ > A2G5a02(Xi2 - Xr2) = 0 (2.10.2)
The First Law of Thermodynamics was introduced for such flow situations in Sec. 2.8.
The analysis required here follows similar logical lines. The First Law of Thermodynamics
for flow from superposition station 1 to superposition station 2 can be expressed as:
2 2
u , c sl _ u . c s2
sl ~2~ ~ 2 T"
or, (4+G5ari)-(c?2+G5a?2) = 0 (2.10.3)
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