Atomization fuel pressure effects

Abou-Ellail, M. M. M., Elkotb, M. M. and Rafat, N. M. (1978). Effects of fuel pressure, air pressure and air temperature on droplet size distribution in hollow cone kerosene sprays. Proc. 1st Inter. Conf. on Liquid Atomization and Spray Systems (ICLAS 78), Tokyo, 85-99. 

The influence of design and operating variables on spray formation for pressure swirl atomizers has been well studied (e.g., Effects of fuel pressure and nominal flow rate... 

Effects of Atomizer Size and Fuel Pressure on Spray Formation. Atomizer is Delavan 60A. Fuel is SRC II Middle Distillate. 

The effect of higher fuel injection pressures (better atomization and higher turbulence) for a HSDl-TCl diesel engine with EGR is shown in Fig. 7. The introduction of a high pres.sure commron rail (HPCR) fuel injection system with flexible fuel pressure levels makes it possible to shift the NOx/particulate trade-off towards substantially lower levels, since better ftiel atomization improves the EGR tolerance of the combustion system. 

Optical methods of observation allow specifying a pattern of physico-chemical processes which accompany an explosion. In a number of cases, errors probably occurred because incomplete data which was obtained by other methods of measurement (spectroscopic, thermal, pressure etc.) were corrected. In this regard, it is useful to visualize the effect of physico-chemical processes on external gas dynamic phenomena which occur when gaseous fuel or atomized fuel self-ignites in the flow of a gaseous oxidizer (most often - air or oxygen). 

Detergent Additives. Diesel engine deposits ate most troublesome in the fuel dehvery system, ie, the fuel pump and both fuel side and combustion side of the injectors. Small clearances and high pressures mean that even small amounts of deposits have the potential to cause maldistribution and poor atomization in the combustion chamber. The same types of additives used in gasoline ate used in diesel fuel. Low molecular weight amines can also provide some corrosion inhibition as well as some color stabilization. Whereas detergents have been shown to be effective in certain tests, the benefit in widespread use is not fully agreed upon (77). 

Droplet size, particularly at high velocities, is controlled primarily by the relative velocity between liquid and air and in part by fuel viscosity and density (7). Surface tension has a minor effect. Minimum droplet size is achieved when the nozzle is designed to provide maximum physical contact between air and fuel. Hence primary air is introduced within the nozzle to provide both swid and shearing forces. Vaporization time is characteristically related to the square of droplet diameter and is inversely proportional to pressure drop across the atomizer (7). 

Of course, all the appropriate higher-temperature reaction paths for H2 and CO discussed in the previous sections must be included. Again, note that when X is an H atom or OH radical, molecular hydrogen (H2) or water forms from reaction (3.84). As previously stated, the system is not complete because sufficient ethane forms so that its oxidation path must be a consideration. For example, in atmospheric-pressure methane-air flames, Wamatz [24, 25] has estimated that for lean stoichiometric systems about 30% of methyl radicals recombine to form ethane, and for fuel-rich systems the percentage can rise as high as 80%. Essentially, then, there are two parallel oxidation paths in the methane system one via the oxidation of methyl radicals and the other via the oxidation of ethane. Again, it is worthy of note that reaction (3.84) with hydroxyl is faster than reaction (3.44), so that early in the methane system CO accumulates later, when the CO concentration rises, it effectively competes with methane for hydroxyl radicals and the fuel consumption rate is slowed. 

Atomizers Atomization is the process oT breaking up a continuous liquid phase into discrete droplets. Figure 27-24 shows the idealized process by which the surface area or a liquid sheet is increased until it forms droplets. Atomizers may be classified into two broad groups (see Fig. 27-25) pressure atomizers, in which fuel oil is injected at high pressure, and twin-fluid atomizers, in which fuel oil is injected at moderate pressure and a compressible fluid (steam or air) assists in the atomization process. Low oil viscosity (less than 15 mmVs) is required for effective atomization (i.e., small droplet size). Light oils, such as No. 2 fuel oil, may be atomized at ambient temperature. However, heavy oils must be heated to produce the desired viscosity. 

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