The characterisation of diesel nozzle flow using high speed imaging of elastic light scattering

Abstract

2013). The characterisation of diesel nozzle flow using high speed imaging of elastic light scattering. This is the accepted version of the paper. This version of the publication may differ from the final published version. Permanent repository link: http://openaccess.city.ac.uk/13540/ Link to published version: http://dx. ABSTRACTTwo identical, conventional six-hole, valve-covered orifice (VCO) diesel injectors have been modified in order to provide optical access to the region below the needle, and the nozzleflow passages. This has been achieved through the removal of the metal tips, and their replacement with transparent acrylic tips of identical geometry.These two identical injectors were employed in order to offer comparability between the measurements. One of them had a dark, anodised inner surface at the base, while the other had a silvered inner surface at the base. Elastic scattering of incident white light from the internal cavitating flow inside the nozzle holes of the optically accessible diesel injector tips was captured on a high-speed electronic camera. The optical image data was obtained for three injector rail pressures ranging from 200 bar to 400 bar, and for five diesel fuels of varying density, viscosity, and distillation profile, in order to identify variations in cavitation flow behaviour inside the nozzle hole passages.A set of mean time-resolved diesel fuel flow images were obtained from thirty successive fuel injection pulses, for each operating condition, for each injector. The mean cavitation image occurring in the nozzle holes was converted to the mean proportion of nozzle hole area producing cavitation-induced optical scattering. The mean normalised area images were then 2 analysed, and were able to demonstrate the anticipated inverse relationship between injected fuel mass and cavitation volume fraction (indicated by mean normalised area), and the effect of fuel viscosity and distillation profile on cavitation volume fraction (again indicated by mean normalised area)

An Optical Characterization of Atomization in Non-Evaporating Diesel Sprays

“…The needle returned to its sealed position approximately 6.0 ms after the electronic start-of-injection signal. The needle lift was achieved using the same electronic driver unit as reported in Lockett et al [8], in order to provide the injector with the same lift profile. This needle lift profile corresponds to moderate common rail pressures, and is typical for engines operating at idle or low/part load.…”

Dynamics of post-injection fuel flow in mini-sac diesel injectors part 1: Admission of external gases and implications for deposit formation

“…Hence the needle returned to its initial position approximately 5.5 ms -6.0 ms after the electronic start-of-injection (SoI) signal. The needle lift profile was measured optically [36], and by using a magnetic induction sensor imbedded in a VCO injector of similar design [37]. The lift profiles corresponding to 350 bar accumulator pressure are shown in Figure 2.…”

“…This was also connected to a chilled water cooling system which was employed to maintain the fuel temperature in the fuel injection system at a predetermined set value of 40 o C. 1The black line needle lift profile was measured using a VCO injector with an induction sensor [36]. 2The grey line needle lift profile was measured optically using successive image frames [37].…”

A Chemical and Morphological Study of Diesel Injector Nozzle Deposits - Insights into their Formation and Growth Mechanisms

“…In each injector nozzle there was a region of rough deposit formation on the corner of the inlet and the minisac/valve seat of each injector. Here the flow of liquid fuel would be pushed away from the surface of the injector by the cavitation and the formation of a vena contracta [14] (before bubble collapse). This prevents contact with liquid fuel would have carried away the deposit pre-cursors, especially in the deposit control additive containing CD KC fuel.…”