Design and Simulation of Two Stroke Engines

Design and Simulation of Two-Stroke Engines
(a) An enlargement, Ar = 2, for an incident compression wave where Pu = 1.2 and Xu =
1.02639
From Eqs. 2.9.7 and 2.9.8, Xri = 0.9912 and Xr2 = 1.01759. Hence, the pressure ratios,
Prl and Pr2, of the reflected waves are:
Pd =0.940 and Pr2= 1.130
The sudden enlargement behaves like a slightly less-effective "open end," as a completely
open-ended pipe from Sec. 2.8.1 would have given a reflected pressure ratio of 0.8293 instead
of 0.940. The onward transmitted pressure wave into pipe 2 is also one of compression, but
with a reduced pressure ratio of 1.13.
(b) An enlargement, Ar = 2, for an incident expansion wave where Pu = 0.8 and Xu = 0.9686
From Eqs. 2.9.7 and 2.9.8, Xri = 1.0105 and Xr2 = 0.97908. Hence, the pressure ratios,
Prl and Pr2, of the reflected waves are:
Prl = 1.076 and Pr2 = 0.862
As above, the sudden enlargement behaves as a slightly less-effective "open end" because
a "perfect" bellmouth open end to a pipe in Sec. 2.8.2 was shown to produce a stronger
reflected pressure ratio of 1.178, instead of the weaker value of 1.076 determined here. The
onward transmitted pressure wave in pipe 2 is one of expansion, but with a diminished pressure
ratio of 0.862.
(c) A contraction, Ar = 0.5, for an incident compression wave where Pu = 1-2 and Xu =
1.02639
From Eqs. 2.9.7 and 2.9.8, Xrl = 1.0088 and Xr2 = 1.0352. Hence, the pressure ratios, Pri
and Pr2, of the reflected waves are:
Pri = 1.063 and Pr2= 1.274
The sudden contraction behaves like a partially closed end, sending back a partial "echo"
of the incident pulse. The onward transmitted pressure wave is also one of compression, but
of increased pressure ratio 1.274.
(d) A contraction, Ar = 0.5,for an incident expansion wave where Pu = 0.8 and Xu = 0.9686
From Eqs. 2.9.7 and 2.9.8, Xri = 0.9895 and Xr2 = 0.9582. Hence, the pressure ratios, Pri
and Pr2, of the reflected waves are:
Pri = 0.929 and Pr2 = 0.741
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