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Direct Injection (DI) System |
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Direct Injection |
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Direct Injection systems are
used on two-stroke engines to dramatically reduce the level of unburned
fuel escaping from the exhaust port during the exhaust scavenging
cycle by injecting only when the exhaust port is closed and scavenging
with charge air only. This allows two-stroke engines to be able to
meet stringent emissions levels mandated for engines in such regions
as Europe, North America, Taiwan and India. Further, Synerject’s
air-assist system produces a stratified charge spray plume (see figure
1) directly inside the combustion chamber with high evaporation rates
which limits fuel impingement on the cylinder walls and thereby
reduces hydrocarbon emissions by at least 75% while operational fuel
consumption benefits of 35-50% are achievable. |
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Figure
1 |
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A simplified control
system diagram is shown in figure 2, which is very similar to that
used in a Port Injected engine and in fact, Synerject’s
single-cylinder PI and DI systems use effectively the same Engine
Control Unit (ECU). However, control strategies are very different
between the two systems due to the intrinsically different combustion
systems, homogeneous for PI and stratified for DI.
The electronically operated Air Injector (see Figure 3) is
controlled by the ECU and allows the fuel metered by the Fuel Injector
(see Figure 3) to be propelled directly into the combustion chamber by
an air blast action. Compressed air is used to finely atomize and
vaporize fuel and create a stable, easily ignited air/fuel spray.
Air-assist Direct Injection can also be used on traditional
four-stroke non-automotive and automotive engines. Four-stoke
air-assist direct injection benefits include meeting current and
proposed emissions standards while obtaining a significant fuel
consumption benefit (10 to 20%) over same engine with port injection.
The system can use low risk, low cost, catalyst system options that
can be staged in parallel with fuel quality improvements around the
world to meet ultra stringent emissions regulations and additionally
the fuel consumption benefit provides reductions in greenhouse
emissions. |
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Figure 2 |
Figure
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