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Most modern high-pressure common rail diesel fuel injection systems employ an internal pressure equalization system in order to support needle lift, enabling precise control of the injected fuel mass. This results in the return of a fraction of the high-pressure diesel back to the fuel tank. The diesel fuel flow occurring in the injector spill passages is expected to be a cavitating flow, which is known to promote fuel ageing. The cavitation of diesel promotes nano-particle formation through induced pyrolysis and oxidation, which may result in deposits in the vehicle fuel system. A purpose-built high-pressure cavitation flow rig has been employed to investigate the stability of unadditised crude-oil derived diesel and paraffin-blend model diesel, which were subjected to continuous hydrodynamic cavitation flow across a single-hole research diesel nozzle.

High-speed planar laser Mie scattering and Laser Induced Fluorescence (PLIF) were employed for the determination of Sauter Mean Diameter (SMD) distribution in non-evaporating diesel sprays. The effect of rail pressure, distillation profile, and consequent fuel viscosity on the drop size distribution developing during primary and secondary atomization was investigated. Samples of conventional crude-oil derived middle-distillate diesel and light distillate kerosene were delivered into an optically accessible mini-sac injector, using a customized high-pressure common rail diesel fuel injection system. Two optical channels were employed to capture images of elastic Mie and inelastic LIF scattering simultaneously on a high-speed video camera at 10 kHz. Results are presented for sprays obtained at maximum needle lift during the injection. These reveal that the emergent sprays exhibit axial asymmetry and vorticity.

Control of inlet valve deposit (IVD) formation in port fuel injected (PFI) gasoline spark ignition (SI) engines has been an on-going concern due to the deleterious impact that this material can have on engine performance (power, acceleration times, drivability and fuel consumption). However, decoupling the effects of IVD formation from the multiplicity of other changing engine parameters whilst quantifying the impacts on engine behavior has remained a challenging task to accomplish. A dedicated experimental methodology is presented that has been specifically designed to address this issue. It successfully decouples and quantifies those engine performance impacts that are attributable to IVD formation. Results are presented demonstrating the deleterious impact of IVD formation on fuel consumption in a PFI SI engine.