Design and Simulation of Two Stroke Engines

ao in C02
Chapter 2 - Gas Flow through Two-Stroke Engines
co2 a 0 = VYco2RcoJo = V1.28X 189x293 = 266.2 m/s
The reference acoustic velocity for air is some 28.9% higher than that in carbon dioxide.
At equal values of pressure wave amplitude this provides significant alterations to the
motion of the pressure wave in each segment of the gas in the pipe. Consider the theory of
Sec. 2.1.4 for a compression wave with a pressure ratio of 1.3 at the above state conditions in
a 25-mm-diameter pipe, i.e., a pipe area, A, of 0.000491 m 2 .
For air the results for pressure amplitude ratio, X, particle velocity, c, propagation velocity,
a, density, p, and mass flow rate, rh, would be:
X X = P G17 = 1.3 T = 1.0382
c c = G5a0(X - 1) = 5 x 343.1 x 0.0382 = 65.5 m/s
a a = a0(G6X - G5) = 343.1 x (6 x 1.0382 - 5) = 421.7 m/s
p p = p0X G5 = 1.205 x 1.0382 5 = 1.453 kg/m 3
rh rii = pAc = 1.453 x 0.000491 x 65.5 = 0.0467 kg/s
For carbon dioxide the results for pressure amplitude ratio, X, particle velocity, c, propagation
velocity, a, density, p, and mass flow rate, rh, would be:
X X = P G17 = 1.3 01094 = 1.0291
c c = G5a0(X - 1) = 7.143 x 266.2 x 0.0291 = 55.3 m/s
a a = a0(G6X - G5) = 266.2 x (8.143 x 1.0291 - 7.143) = 329.3 m/s
p p = p0X G5 = 1.830 x 1.0291 7143 = 2.246 kg/m 3
rh rh = pAc = 2.246 x 0.000491 x 55.3 = 0.061 kg/s
The GPB finite system simulation method has no difficulty in modeling a pipe system to
include these considerable disparities in gas properties and the ensuing behavior in terms of
wave propagation. The computation is designed to include the mixing and smearing of the
gases at the interface between mesh systems which have different properties at every mesh
within the computation, and the reflections of the pressure waves at the inter-mesh bound-
189