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Fuel Injection Systems with a focus on Fuel atomization

Fuel Injection Systems with a focus on Fuel atomization. By: David Shamrell. Overview. Fuel Injection Systems Speed Density EFI Fuel Injector Design Fuel Atomization Swirl Injectors Electrospray. Speed Density Fuel Injection Sys. Fuel Flow Path:

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Fuel Injection Systems with a focus on Fuel atomization

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  1. Fuel Injection Systems with a focus on Fuel atomization By: David Shamrell

  2. Overview • Fuel Injection Systems • Speed Density • EFI • Fuel Injector Design • Fuel Atomization • Swirl Injectors • Electrospray

  3. Speed Density Fuel Injection Sys. • Fuel Flow Path: • Pump → Filter → Regulator → Branch Lines → Injector. • Air Flow Path • Air Filter →Throttle Plate →Intake Manifold • Determines Air Flow Via: • Engine Speed • Manifold Pressure • Air Temperature

  4. EFI System • Fuel Flow Path • Same as Speed Density • Air Flow Path • Air Filter →Air Flow Sensor→ Throttle Plate→ Intake Manifold • Determine Air Flow Via: • Measured Air Flow • Engine Speed Air Flow Sensor

  5. Fuel Injector • Electromagnetically actuated valve • Can cycle several times a second • Controlled by Electronic Control Unit (ECU) • Nozzle design affect atomization • Needle helps minimize dribble (secondary injection)

  6. Fuel Atomization • Fuel Atomization is a function of: • Fuel injector geometry • Fuel jet velocity • Function of fuel system pressure • Spray type (turbulent or laminar) • Function of nozzle type (Swirl, etc) • Fuel delivery temperature • Fuel electrical charge

  7. Swirl Nozzle Injectors • Multiple types, one pictured from patent 6029913 • Filed by Cummins Engine Company 1998 • 6 curvilinear spray holes • 90 degree curvature orientation • “flow through tangential flow path causing rapid spreading and breakup of fuel jet spray upon exiting spray hole”

  8. Electrospray Injection • Installed Electrode: • Downstream fuel injector • Upstream orifice • Benefits • Reduces surface tension of liquid • Shortens breakup length • Enlarges the cone angle of the spray

  9. Electrospray Experimental Results 0 KV Fuel jet No jet 30 KV Wider more homogenous spray

  10. Electrospray Issues • Charge To Mass Ratio (of droplet) • Inversely proportional to droplet size • Step increase around 20µm (droplet diameter) • Modern techniques w/out electrode can achieve 10µm • Charge Used in Experimental = 30KV • Hard to obtain in a mobile platform • Injection velocity vs. charge (Competing Factors) • Charge imparted is a function of time • Slower velocity = more charge • However atomization is proportional to injection velocity • Thus slower velocity = less atomization

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