The industrial Airo Nozzle is an air atomizing nozzle designed to handle #2, #4, and preheated #5 and #6 fuels. Air is supplied at relatively low pressure to provide the energy for atomization. Air atomizing nozzles provide good atomization of fuels too viscuous for pressure atomizing nozzles. They can also provide finer breakup if sufficient air is available. The Airo Nozzle is of the internal mixing type. That means that the air and fuel are piped separately to the nozzle and are mixed just before they enter the atomizing slots. The air under pressure is mixed thoroughly with the fuel in the swirl chamber so that a uniform emulsion is discharged through the orifice. The resultant spray is well atomized in a solid cone pattern. The cost of equipment with air atomizing nozzles is higher than for equivalent pressure atomizing nozzles because of the addition of the compressor. The power requirement is also higher because of the extra power required to compress air. These disadvantages are offset, however, by the advantages in handling of heavy fuels.
- The Airo Nozzle may be used as a fixed discharge nozzle. (Fuel metering is discussed in a following heading.)
- This nozzle may be arranged for two-stage firing if desired.
- This type of nozzle may be arranged for complete modulating over the desired flow range.
- The Airo Nozzle will handle light fuels at any flow rate from 2 GPH and up. The proper nozzle must be selected for each range.
- The Industrial Airo Nozzle will handle #5 oil or #6 oil preheated to approximately 100 SSU. Above 20 GPH, higher viscosities
- Uniform solid cone-spray angle varies with air pressure and flow. A separate metering device, such as an orifice, metering pump or valve is required.
- Large flow passages greatly reduce clogging.
- With the internal mixing type of nozzle, the spray angle changes with the fuel-air ratio (pounds of fuel per pound of atomizing air). The spray angle is wider at high fuel-air ratios. For example, if the spray angle is 750 at a fuel-air ratio of 30 to 1, it may be reduced to 600 at a fuel-air ratio of 10 to 1.
- Higher air pressures produce narrower spray angles.
- Droplet size is smaller at higher air pressures and narrower spray angles.
- Constant spray angles may be obtained by modulating air pressure with the fluid flow.
- A fixed firing rate may be obtained by supplying fuel by a pressure pump through a fixed metering orifice to the nozzle.
- Two stage operation may be obtained by the use of two metering orifices in the fuel line, one of them in series with a solenoid valve. This solenoid valve will be actuated by pressure or temperature.
- A positive fuel metering pump of the piston type is satisfactory for single stage operation.
- Modulating metering may be obtained by the use of a fuel pump in combination with a modulating valve.
- Metering cannot be done with this type of nozzle by balancing fuel pressure against air pressure.
METHODS OF METERING FUEL
- Metering pump.
- Constant pressure pump and metering orifice in the line.
- Constant pressure pump and motorized modulating valve actuated by steam pressure, water or process temperature. AIR COMPRESSOR
- May be rotary type for pressures up to 25 PSI or as rated by manufacturer.
- May be piston type for higher pressure.
- May have built in pressure relief valve.
- Must have enough capacity for the nozzle requirement.
It may be necessary when burning residual fuels to provide some means for heating the nozzle and fuel line before starting. It may also be advantageous to provide air purge of the fuel line to the nozzle on shut-down. It is always advisable to make certain that air flow through the nozzle is established before fuel is supplied. This will prevent backing up of fuel into the air line and equipment. It will also insure good atomization at the start.
- Since the fuel and air passages in this type of nozzle are quite large, clogging is not a serious problem. It is recommended, however, that both the air and the fuel be filtered to remove lint and large particles of foreign matter. Clogging of air passages or fuel passages will result in off-center fires.
- Damage to the orifice may result in a streaky fire, an off-center fire, or drooling
CONSTRUCTION AND MATERIALS:
The Airo nozzle is made up of three basic parts, available in the following materials:
- NOZZLE BODY – Brass or stainless steel. Thread sizes: 3/4”-20 UNEF on #30615 and 1-1/8”-18 UNEF on #30616.
- DISTRIBUTOR – Brass, stainless steel, or tungsten carbide (requires special body with replaceable tungsten carbide orifice disc, integral with body.)
- SCREW PIN – Brass or stainless steel. NOTE: Contact factory for other material requirements.