Effect of Fuel Properties on Spray Development from a Multi-Hole DISI Engine Injector

Abstract

Extensive literature exists on spray development, mixing and combustion regarding engine modeling and diagnostics using single-component and model fuels. However, often the variation in data between different fuels, particularly relating to spray development and its effect on combustion, is neglected or overlooked. By injecting into a quiescent chamber, this work quantifies the differences in spray development from a multi-hole direct-injection spark-ignition engine injector for two single-component fuels (iso-octane and n-pentane), a non-fluorescing multi-component model fuel which may be used for in-cylinder Laser Induced Fluorescence experiments, and several grades of pump gasoline (with and without additives). High-speed recordings of the sprays were made for a range of fuel temperatures and gas pressures. It is shown that a fuel temperature above that of the lowest boiling point fraction of the tested fuel at the given gas pressure causes a convergence of the spray plumes. Increasing the fuel temperature increases this convergence, whilst an associated increased rate of evaporation tends to reduce the penetration of individual plumes. The convergence increases gradually with increasing fuel temperature until all plumes combine to form a single wider plume with a penetration rate greater than that of the individual plumes. When all plumes are converged to form a single plume along a central axis to all the plumes, any further increase in fuel temperature at the given gas pressure acts to increase the rate of evaporation of the fuel. At experiments up to 180 °C fuel temperature and down to 0.3 bar absolute gas pressure, none of the tested fuels were found to spontaneously vaporize; all observed spray formations being a gradual evolution. Increasing the gas pressure at any given fuel temperature, leads to an increase in the boiling temperature of all components of that fuel and, hence, diminishes these effects.

Numerical investigation of VOC levels in the area of petrol stations

“…It should be also be mentioned here for completeness that high-volatility components like n-pentane have been found to be suitable single components to mimic gasoline's spray behaviour at relevant conditions (e.g. see van Romunde et al, 2007;van Romunde and Aleiferis, 2009). Additionally ethanol has shown similar behaviour to gasoline in terms of spray effects related to temperature and pressure conditions (e.g.…”

“…Figure 3 shows the distillation curve of a typical pump-grade gasoline, as well as the boiling points of some single components which are found in high concentration in gasoline, and thus the focus of the present study (more details about the curves can be found in van Romunde et al, 2007;van Romude and Aleiferis, 2009;Aleiferis et al, 2010a-b;Serras-Pereira et al, 2012. In particular, some of the vapour properties of n-pentane, ethanol, iso-octane, toluene, o-xylene and benzene are presented in Table 2 at 298 K and 315 K (Yaws, 2003); density values are also shown from ideal gas calculations.…”

Cavitation, primary break-up and flash boiling of gasoline, iso-octane and n-pentane with a real-size optical direct-injection nozzle

“…The investigation used the same injection system and facilities described in previous publications by the authors [22][23][24][25][26][27]. Therefore primarily deviations from standard equipment, i.e.…”

“…This was achieved using a real-size optical nozzle to simulate the flow in one of 8 the holes of a real multi-hole injector previously used by the authors for macroscopic spray imaging and related engine studies [22][23][24][25][26][27]. These studies showed that the geometry and break-up of sprays from such injectors is significantly affected by operating conditions, which result in a high degree of superheating of the fuel components, i.e.…”

“…The six nozzle holes have different turning angles that direct fuel to different areas of the combustion chamber but they are symmetric with respect to a centerline, therefore, only 3 'sprays' can be seen from the main imaging view corresponding to the 3 plume pairs (1,6; 2,5; 3,4). Further details can be found in [22][23][24][25][26][27].…”