Twin Fluid Atomizers
5. Combustion of liquid fuels
5.1 Atomization of fuel
Liquid fuels such as gasoline, diesel, fuel oil light, fuel oil heavy or kerosene have to be atomized and well mixed with the combustion air before burned. Therefor nozzles are used.
Nozzles are divided into two groups: Pressure atomizers and twin-fluid atomizers.
5.1.1 Pressure atomizers
Pressure atomizers are differed into turbulence nozzles and liquid sheet nozzles. At both types of nozzles the energy from the liquid pressure is converted into kinetic energy and a small part of it into forming new surface. To increase the flow rate at a pressure atomizer, the liquid pressure has to be increased. This influences the drop properties of the spray generated.
Turbulence nozzles
Turbulence nozzles are used for fuel injection at diesel engines. The turbulence is generated by the high fuel velocity. The fuel jet leaving the nozzle breaks up into small drops very soon in a short distance after the nozzle outlet. The smaller the nozzle outlet is, the smaller the generated drops are. Thereby is has also taken into account that the flow rate at a constant fuel pressure decreases with smaller outlet diameter. Usual fuel pressures are above 1400 bar. The spray pattern of such a nozzle is a full cone.
In 1974 Hiroyasu and Katoda found the equation
0
− d 32 = 2330 ⋅ ρ 0,121 ⋅ VB ,131 ⋅ Δp B0,135 ,
L
(5-1)
for calculating the Sauter-Mean-Diameter for diesel injection nozzles. Thereby ρa is the air density, Vf the fuel volumetric flow and Δpf the pressure difference at the nozzle. The fuel volumetric flow can be replaced by the equation
VB = u ⋅ A =
2 ⋅ Δp B π 2
⋅ ⋅D ρB 4
(5-2)
Thereby ρf is the fuel density and D the nozzle outlet diameter. The following equation achieved d 32 = 2362 ⋅
ρ 0,121 D 0, 262
L
⋅ 0,0695 .
0 , 0655 ρB Δp B
(5-3)
The variables has to be used in SI-units. The Sauter-Mean-Diameter is the diameter of a drop whose ratio of volume to surface area
5.1 Atomization of fuel
Liquid fuels such as gasoline, diesel, fuel oil light, fuel oil heavy or kerosene have to be atomized and well mixed with the combustion air before burned. Therefor nozzles are used.
Nozzles are divided into two groups: Pressure atomizers and twin-fluid atomizers.
5.1.1 Pressure atomizers
Pressure atomizers are differed into turbulence nozzles and liquid sheet nozzles. At both types of nozzles the energy from the liquid pressure is converted into kinetic energy and a small part of it into forming new surface. To increase the flow rate at a pressure atomizer, the liquid pressure has to be increased. This influences the drop properties of the spray generated.
Turbulence nozzles
Turbulence nozzles are used for fuel injection at diesel engines. The turbulence is generated by the high fuel velocity. The fuel jet leaving the nozzle breaks up into small drops very soon in a short distance after the nozzle outlet. The smaller the nozzle outlet is, the smaller the generated drops are. Thereby is has also taken into account that the flow rate at a constant fuel pressure decreases with smaller outlet diameter. Usual fuel pressures are above 1400 bar. The spray pattern of such a nozzle is a full cone.
In 1974 Hiroyasu and Katoda found the equation
0
− d 32 = 2330 ⋅ ρ 0,121 ⋅ VB ,131 ⋅ Δp B0,135 ,
L
(5-1)
for calculating the Sauter-Mean-Diameter for diesel injection nozzles. Thereby ρa is the air density, Vf the fuel volumetric flow and Δpf the pressure difference at the nozzle. The fuel volumetric flow can be replaced by the equation
VB = u ⋅ A =
2 ⋅ Δp B π 2
⋅ ⋅D ρB 4
(5-2)
Thereby ρf is the fuel density and D the nozzle outlet diameter. The following equation achieved d 32 = 2362 ⋅
ρ 0,121 D 0, 262
L
⋅ 0,0695 .
0 , 0655 ρB Δp B
(5-3)
The variables has to be used in SI-units. The Sauter-Mean-Diameter is the diameter of a drop whose ratio of volume to surface area