Fuel Oil Burner Nozzles: What They Are and How They Work

Fuel oil burner nozzles are devices that spray fuel oil into the combustion chamber of a burner, where it mixes with air and ignites to produce heat. Fuel oil burner nozzles are designed to atomize the fuel oil, which means breaking it up into tiny droplets that can burn more efficiently and completely.

There are different types of fuel oil burner nozzles, depending on the flow rate, spray angle, spray pattern, and droplet size of the fuel oil. These parameters affect the performance, efficiency, and emissions of the burner, as well as the shape and size of the flame.

Flow Rate

The flow rate of a fuel oil burner nozzle is the amount of fuel oil that passes through the nozzle per hour, measured in gallons per hour (GPH) or liters per hour (LPH). The flow rate depends on the size of the nozzle orifice, the pressure of the fuel oil, and the viscosity of the fuel oil. The flow rate is usually stamped on the nozzle tip, along with the spray angle and spray pattern.

The flow rate determines the heat output of the burner, which should match the heat demand of the appliance or system. A nozzle with a higher flow rate will produce more heat, but also consume more fuel oil and generate more emissions. A nozzle with a lower flow rate will produce less heat, but also save fuel oil and reduce emissions. Therefore, it is important to select the proper flow rate for the burner and the application.

Spray Angle

The spray angle of a fuel oil burner nozzle is the angle of the cone-shaped spray of fuel oil that exits the nozzle, measured in degrees. The spray angle depends on the shape of the nozzle orifice and the swirl slots, which are grooves that cause the fuel oil to swirl in the nozzle chamber before exiting the orifice. The spray angle is usually stamped on the nozzle tip, along with the flow rate and spray pattern.

The spray angle affects the shape and size of the flame, which should fit the combustion chamber of the burner. A nozzle with a larger spray angle will produce a wider and shorter flame, while a nozzle with a smaller spray angle will produce a narrower and longer flame. Therefore, it is important to select the proper spray angle for the burner and the combustion chamber.

Spray Pattern

The spray pattern of a fuel oil burner nozzle is the shape of the cross-section of the spray of fuel oil that exits the nozzle. The spray pattern depends on the distribution of the fuel oil droplets in the spray cone, which is influenced by the design of the nozzle orifice and the swirl slots. The spray pattern is usually stamped on the nozzle tip, along with the flow rate and spray angle, and indicated by a letter code.

The most common spray patterns are:

• A or H: Hollow cone. The fuel oil droplets are concentrated on the outer edge of the spray cone, leaving a hollow space in the center. This spray pattern is suitable for most applications, as it provides good atomization and combustion.
• B or ES: Solid cone. The fuel oil droplets are evenly distributed throughout the spray cone, filling the entire space. This spray pattern is suitable for applications that require a stable and compact flame, such as high-pressure burners.
• SS: Semi-solid cone. The fuel oil droplets are distributed in a ring-shaped pattern, leaving a small hollow space in the center. This spray pattern is a compromise between the hollow and solid cone, and is suitable for applications that require a moderate flame stability and size, such as low-pressure burners.
• W: Multipurpose. The fuel oil droplets are distributed in a variable pattern, depending on the pressure and viscosity of the fuel oil. This spray pattern is suitable for applications that use different types of fuel oil, such as waste oil or biodiesel.

Droplet Size

The droplet size of a fuel oil burner nozzle is the average diameter of the fuel oil droplets that exit the nozzle, measured in microns. The droplet size depends on the pressure and viscosity of the fuel oil, as well as the design of the nozzle orifice and the swirl slots. The droplet size is not usually stamped on the nozzle tip, but it can be estimated from the flow rate and the spray angle.

The droplet size affects the quality of the atomization and the combustion of the fuel oil. A nozzle with a smaller droplet size will produce a finer spray, which can burn more completely and cleanly. A nozzle with a larger droplet size will produce a coarser spray, which can burn less completely and cleanly. Therefore, it is important to select the proper droplet size for the burner and the fuel oil.

Table of Common Nozzle Types

The following table summarizes some of the common nozzle types and their characteristics, based on the information from InspectAPedia, Beckett Corporation, HVAC School, Delavan, and Keith Specialty.