In-cylinder air flow structures are known to play a major role in mixture preparation and engine operating limits for DISI engines. In this paper PIV was undertaken on in-cylinder flow fields for three different planes of measurement in the intake and compression strokes of a DISI engine for a lowload engine operating condition at 1500 RPM, 0.5 bar inlet plenum pressure (World Wide Mapping Point). One of these planes was vertical, cutting through the centrally located spark plug (tumble plane); the other two planes were horizontal, one close to TDC (10 mm below fire face) and the other one close to mid stroke (50 mm below fire face). Statistical analysis was undertaken on the numbers of cycles needed to determine ensemble average flow-field and turbulent kinetic energy maps with up to 1200 cycles considered. The effect of engine head temperature was also examined by obtaining flow fields using PIV with the engine head coolant held at 20 °C and 80 °C. LDV measurements were also performed and compared to the data obtained by PIV. Finally comparisons were made between the experimental data and results from CFD simulations using two different turbulence models on a grid of 1 million cells.
One of the latest advancements in injector technology is laser drilling of the nozzle holes. In this context, the spray formation and atomisation characteristics of gasoline, ethanol and 1-butanol were investigated for a 7-hole spark eroded (SE) injector and its 'direct replacement' Laser-drilled (LD) injector using optical techniques. In the first step of the optical investigation, high-speed spray imaging was performed in a quiescent injection chamber with global illumination using diffused Laser light. The images were statistically analyzed to obtain spray penetration, spray tip velocity and spray 'cone' angles. Furthermore, droplet sizing was undertaken using Phase Doppler Anemometry (PDA). A single spray plume was isolated for this analysis and measurements were obtained across the plume at a fixed distance from the nozzle exit. The droplet measurements were grouped into bins and maps were created showing droplet sizes and velocities against time and position during and post injection. All tests were performed at 120 bar fuel pressure, two injection chamber 'back' pressures (0.5 bar and 1 bar) and two injector temperatures (20 °C and 80 °C), to examine effects relevant to typical engine operating conditions with early intake stroke injection strategies, including fuel flash boiling.
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