Design and Simulation of Two Stroke Engines

0.35 •
0.34
LU
° 0.33 -
c
03
DC 0.32
Q
0.31
0.30
Chapter 7 - Reduction of Fuel Consumption and Exhaust Emissions
11
Delivery Ratio
\
i
12
Charging Efficiency
/
—v
—r~ —r
13 14
-
15
AIR-TO-FUEL RATIO
LOOP
DEFLECTOR
DEFLECTOR
LOOP
—i
16
Fig. 7.24 Airflow and charging of a low emissions engine.
1.0 n
US
h-
°a 0.9
LU
CO
>
O 0.8 H
z
LU
o LL
LU
0.7 -
0.6
11
Trapping Efficiency
Scavenging Efficiency
DEFLECTOR
LOOP
DEFLECTOR
B=SJ-B-B—B_fl LOOP
—r-
12
—r~
13
—r -
14
—r -
15
AIR-TO-FUEL RATIO
Fig. 7.25 Scavenging and trapping efficiencies of a low emissions engine.
tor piston and cross scavenging, yielded a bmep of 2.7 bar at the same fueling level (see Fig.
7.21). Thus, to achieve equality of power output at the same engine speed, the low bmep
design would need to have a larger swept volume in direct proportion to these bmep levels,
which would mean an engine displacement increase from 65 cm 3 to 91 cm 3 . The specific
hydrocarbons emitted would be reduced from 128 g/kWh to 25 g/kWh, which is over five
times lower. In terms of energy emitted into the exhaust system, the total hydrocarbon emissions
are reduced from 370 g/h to 72.3 g/h.
If the engine is operated at an air-to-fuel ratio of 14, the bsCO emission is 25 g/kWh. The
energy content, Qex, released into the exhaust system as calculated from Eq. 7.2.1, is 1.1 kW.
The original design rejected 4.8 kW into the exhaust system at the same air-to-fuel ratio. The
489
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16