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Fundamental Investigation of Jet Fuel Spray and Ignition Process in an Optically Accessible Piston Engine

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Final rept. 17 Oct 2011-16 Oct 2014

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Effects of transient rate-of-injection ROI fuel sprays on jet development and combustion were measured in a compression-ignition direct injection optical engine. Jet penetration, liquid length, jet dispersion angle, liftoff length, and engine cylinder pressure data were simultaneously acquired over a range of engine operating conditions relevant to the design of Army engines. Tests were performed using 2 diesel fuel, jet fuel JP8, and a hydroprocessed renewable jet fuel HRJ. Ambient thermodynamic conditions and fuel injection parameters had similar effects on combustion and jet performance in the optical engine as in previous results from constant volume chambers. The ramp-on transient from the opening of the fuel injector caused the scaling of jet parameters with time during the transient ROI to be modified from relationships expected from the literature. Similarities were seen in a comparison between the jet velocity, the derivative of the ROI and the derivative of a curve fit created to model the data taken. In the long-time limit, these injections were seen to return to their quasisteady forms, with the changes in jet parameters occurring during the initial opening of the injector. The results show the need to resolve the initial transient injection process in small bore diesel engines.

Subject Categories:

  • Thermodynamics
  • Combustion and Ignition
  • Fuels
  • Reciprocating and Rotating Engines

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