Delphi Multec 3.5, Руководство по применению

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Multec 3.5 Fuel Injector Application Manual Product Description
Delphi Energy and Chassis Systems Revision: 11/05-1 3-23
•
Retracting the injector long distances inside the manifold/head
bore increases the potential for fuel at the fringes of the spray to
collect in the bore and shelters the injector tip from fuel stripping
forces generated by the inlet air flow velocity.
•
Positioning the injector tip out into the inlet air stream reduces the
risk of fuel puddling but also provides surfaces for water to
condense on the injector tip. This can lead to injector icing (see
section 2.2.7.4) and poor or no start conditions on some
applications. Intake manifolds made of low thermally conductive
materials (i.e. plastic) may increase the risk of icing (for injector
tip in manifold designs). Vehicle level icing tests should be
conducted to validate proper operation.
•
Injection timing within the engine cycle can have a significant effect
on fuel targeting and puddling of fuel.
•
For dual intake-valve engines, dual spray injectors may provide some
benefits, especially in meeting more stringent emissions requirements.
With the appropriate intake/cylinder head design, a single spray
injector may also be acceptable for dual intake-valve engines.
•
The interaction of the injector spray with intake mixture motion
control devices need to be considered. Specific injector spray
parameters may be required to take advantage of intake mixture
motion control.
•
Systems testing with Delphi support may be necessary to determine
the optimum spray configuration to meet specific engine performance
and emissions goals. This may include high speed video recording of
fuel injection events in the running application engine, cold start
emissions, steady state emissions, and transient response.
3.8.3 Spray Atomization
Spray atomization is defined by the droplet size distribution of the fuel
spray. Small fuel spray particles will increase the percentage of fuel
vaporized in the cylinder improving combustion of the fuel. Vaporization
can also be improved by increasing the heat input to the fuel: This is
achieved by targeting the fuel at the hotter intake valve area, and by
maximizing the fuel residence time in the port prior to the intake valve
opening.
Spray atomization parameters typically used to describe the distribution of
droplet sizes are the Sauter Mean Diameter (D
32
), and DV
90
. D
32
describes the ratio of volume to surface area for the entire spray. It relates
to the physics of droplet evaporation and is useful in the study of
combustion.