How do liquid fuel physical properties affect liquid jet development in atomisers?

Abstract

The influence of liquid fuel properties on atomisation remains an open question. The droplet sizes in sprays from atomisers operated with different fuels may be modified despite the small changes of the liquid properties. This paper examines experimentally the development of a liquid jet injected from a plain orifice in order to evaluate changes in its behaviour due to modifications of the liquid properties, which may influence the final atomisation characteristics. Two aviation kerosenes with similar, but not identical physical properties are considered, namely standard JP8 kerosene as the reference fuel and bio-derived Hydro-processed Renewable Jet (HRJ) fuel as an alternative biofuel. The corresponding density, dynamic viscosity, kinematic viscosity and surface tension change by about +5%, -5%, -10% and +5% respectively, which are typical for ‘drop-in’ fuel substitution. Three aspects of the liquid jet behaviour are experimentally considered. The pressure losses of the liquid jet through the nozzle are examined in terms of the discharge coefficient for different flowrates. The morphology of the liquid jet is visualised using high magnification Laser Induced Fluorescence (LIF) imaging. Finally, the temporal development of the liquid jet interfacial velocity as a function of distance from the nozzle exit is measured from time-dependent motion analysis of dual-frame LIF imaging measurements of the jet. The results show that for the small changes in the physical properties between the considered liquid fuels, the direct substitution of fuel did not result in a drastic change of the external morphology of the fuel jets. However, the small changes in the physical properties modify the interfacial velocities of the liquid and consequently the internal jet velocity profile. These changes can modify the interaction of the liquid jet with the surroundings, including air flows in coaxial or cross flow atomisation, and influence the atomisation characteristics during changes of liquid fuels

Spray Characteristics of Alternative Aviation Fuel Blends

“…The present work is in line with several contemporary efforts to assess the influence of composition and physical properties on the atomization characteristics of alternative fuels [19][20][21][22][23]. The work was part of a larger effort to investigate the applicability of fuels that can be processed to look like kerosene, as practical alternatives to fossil fuels by the Virtual Fuel Centre of the Environmentally Compatible Air Transport System project (ECATS) [24][25][26].…”

Experimental Investigation of the Effect of Biodiesel Blends on a DI Diesel Engine’s Injection and Combustion

“…The results of spray tip penetration and spray area of biodiesel blends and diesel showed that higher injection pressure result in a longer spray tip penetration and larger spray area than that at lower injection pressures at same elapsed time after the start of injection. Even small changes in the physical properties of the fuels are known to modify the interfacial velocities and consequently the internal injected jets velocity profiles [9]. Furthermore, the use of biodiesel blends in modern engines interferes in a complex way with the fuel injectors, since the injection orifices in the nozzles are created by electro-erosion machining, (electrical discharge machining, EDM) to produce diameters of the order of 100 µm, with their leading edges rounded off by hydro-erosion machining [10].…”

Spinning disk atomization: Theory of the ligament regime

“…1). It should be noted that, as the last term in (15) indicates, expressions (14)- (16) are for the components of velocity in the observer's reference frame so that, to obtain the corresponding components in the coordinate frame rotating with the disk, the last term on the right-hand side of (15) should be taken out. Thus, to find the dominating wave solution for a given wave frequencyω, one needs, first, to calculate the characteristic film thickness H from (5) and the local values of the similarity parameters δ and E from (6) and (7).…”

“…Once the dominating wave is found, one can use the film thicknessh obtained as part of the solution and the velocity profile (14)- (16) as the inlet conditions at S 1 . As already mentioned, in (14)-(16), we drop the last term on the right-hand side of (15) to have the azimuthal velocity component in the rotating frame.…”

“…It should be noted also that small variations of the physical properties of the fluid, i.e., density, viscosity, and the surface tension, can affect the development of the velocity profile and thus the overall atomization process. 16 On the other hand, a head-on numerical simulation of the entire SDA process with the accuracy, especially in tracking the free surface, required for the outcome to be of practical use is well beyond what can be achieved even in the foreseeable future as it would involve computing a three-dimensional unsteady free-boundary flow on vastly disparate length and time scales.…”