Oil burner

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An oil burner for domestic central heating Home oil furnace.jpg
An oil burner for domestic central heating

An oil burner is a heating device which burns #1, #2 and #6 heating oils, diesel fuel or other similar fuels. In the United States ultra low #2 diesel is the common fuel used. It is dyed red to show that it is road-tax exempt. In most markets of the United States heating oil is the same specification of fuel as on-road un-dyed diesel.

Contents

An oil burner is a part attached to an oil furnace, water heater, or boiler. [1] It provides the ignition of heating oil/biodiesel fuel used to heat either air or water via a heat exchanger. The fuel is atomized into a fine spray usually by forcing it under pressure through a nozzle which gives the resulting flame a specific flow rate, angle of spray and pattern (variations of a cone shape). This spray is usually ignited by an electric spark with the air being forced through around it at the end of a blast tube, by a fan driven by the oil burner motor. [2] The fuel pump is typically driven via a coupling connecting its shaft to that of the motor's. Oil burners also include combustion-proving devices to prevent out-of-control combustion - Primary Control; Safety Control; Cad Cell Control; Master Control; Fire-Eye Control are all common names for the 'combustion safety control'.

In the United States residential home heating oil market the "vaporizing gun burner" is the most common mechanical device used to heat a home or small commercial forced air space with. [3] Depending on the manufacturer these simple burners will see a lifespan if regularly maintained for decades. Currently, old installations from the 1950s and 1960s are still in operation today if they received regular maintenance.

The maintenance involved in a gun burner usually is a replacement of the nozzle used to atomize the fuel, replacing the filter located at the air handler, replacing the fuel filter on the heating oil system from the tank, cleaning out any soot or deposits in the heat exchanger of the furnace, and ensuring the system is in good working order, and also involves checking and adjusting the fuel-air mixture for efficiency with a combustion analyzer.

If a heating oil burner runs out of oil it often must be primed to be restarted. Priming involves purging any air from the fuel lines so that a steady flow of oil can find its way to the burner.

If an oil burner wears out it can usually be upgraded and replaced with a more efficient modern burner. If the heat exchanger wears out that requires a new furnace. Oil furnaces will last nearly forever if maintained regularly ensuring the heat exchanger is vacuumed out and cleaned. Oil burners deposit soot in the heat exchanger which is an un-even insulator. The heat distribution in the heat exchanger is un-even, causing wear on this critical steel part causing an eventual cracking. Annual or every other year tune-ups guarantee this wear is far reduced. Oil furnace lifespans of fifty to seventy-five years with regular service are not uncommon compared to an average wear out of natural gas furnaces every twenty years.


Fuel injection

Used nozzles from an oil burner Zerstauberduse Oelbrenner FA Steinen.jpg
Used nozzles from an oil burner

Fuel is injected into the combustion chamber by a spray nozzle.

The nozzles are usually supplied with high pressure oil. Because erosion from friction with the oil, and possible blockage due to lumps in it, they need replacement when worn. Fuel nozzles are usually rated in fuel volume flow per unit time e.g. USGal/h (U.S. Gallons per hour).

A fuel nozzle is characterized by three features:

Alternatively fuel may be passed over a tiny orifice fed with compressed air. This arrangement is referred to as Babington atomiser/nozzle, named after its inventor Robert Babington. [4] As the oil flows over the nozzle, the fuel needn't be under any great pressure. If the pump can handle such the oil may even contain lumps such as scraps of food. Because it is only compressed air that passes through the orifice hole, such nozzles do not suffer much from erosion.

Oil pump

Oil pump Internal gear pump.gif
Oil pump

A gear pump of two parts:

Gear pump assembly

This pumps the oil in and increases the pressure in the nozzles to 15 bar maximum (217.5 psi). Usually a gerotor of the sickle type is used. Gear pumps are used frequently in oil burners because of their simplicity, stability and low price.

Pressure regulator

To set the heat output of the burner, the rate of fuel delivery via the nozzle must be adjustable. This is often achieved by an adjustable pressure relief valve between the pump and the nozzle. When the set pressure is reached (usually 100psi), this valve opens and allows excess oil to flow through a bypass back to the fuel tank or the pump suction side.

Electromagnetic valve

A small two-stage industrial burner. The blue cubes are the coils of the two electromagnetic valves. Light fuel oil burner.JPG
A small two-stage industrial burner. The blue cubes are the coils of the two electromagnetic valves.

This allows fuel to be shut off from the sprayer by electrical control. It helps avoid drips when the valve is closed. It also eases the purging of the burner (and any boiler) of fuel mist during startup, or while restarting after a misfire. If the burner were not purged the oil/air mixture could explode.

Fan

The fan blows air into the combustion chamber. The rotor of the fan is powered by an electric motor.

Igniters

Some oil burners use glow bars which operate much like the glow plugs of a diesel engine.

Many use high voltage generated by a voltage-step up transformer to create a spark for ignition, somewhat similar to a spark plug.

Original oil burner transformers were copper wire conductors wrapped around an iron core. A standard type of transformer to this day. In the mid-90s electronic igniters replaced the copper and iron transformer, solving many problems related to the old style transformer. This new technology in igniters would soon replace all old style transformers throughout the oil burner industry. The new igniters would run cooler so the output voltage could be increased from 10,000 to 20,000 VAC.

This increase of voltage would be more reliable, reduce delayed ignition, run cooler and all while using less energy. The voltage is high, but a standard igniter will only pull around 35 milliamps.

Safety control

LDR LDR07 Light-dependent CdS photoresistor.jpg
LDR

Oil-fired burners are fitted with a safety mechanism for determining if the fuel has ignited and a flame present. The terms "primary control", "safety control", "cad cell control", "master control", and "fire-eye control" are variously used to describe a light dependent electrical resistor (LDR) which detects the flame whose value changes by the amount of light it is exposed to. The resistance decreases as the LDR is exposed to more light. The material is usually cadmium sulfide, hence the name "cad cell" for this component. In darkness the resistance is around 1 MΩ, while when exposed to light from a properly ignited flame the resistance is significantly lower, around 75–300 Ω.

Older oil burners were equipped with a primary control installed on the exhaust stack with a bimetallic heat sensing element protruding into the stack, such a control was referred to as a "stack relay" or a "stack control". It performed the same function as the newer cad-cell control but instead of sensing light from the burner flame it sensed heat from the flame exhaust gases to prove that ignition took place.

Capacitor start motor

Schematic of a capacitor start motor. Condensatormotor.svg
Schematic of a capacitor start motor.

The motor which drives the fan and the oil pump is usually a capacitor start motor. It is a single phase, squirrel cage induction motor. The difference with a three-phase motor is in the stator. Where the three phase motor has three coils aligned at 120° in the stator, the capacitor start motor holds one main winding and one auxiliary winding aligned at 90°. The phase shift of 90° between the main winding and the auxiliary winding is achieved by a connected capacitor which feeds the auxiliary winding and is connected on the single-phase AC mains. The capacitor will achieve a phase shift of 90° between the main and the auxiliary winding, producing an acceptable initial torque. This motor is intended for continuous operation.

See also

Related Research Articles

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Thermostat Component which maintains a setpoint temperature

A thermostat is a regulating device component which senses the temperature of a physical system and performs actions so that the system's temperature is maintained near a desired setpoint.

Spark gap

A spark gap consists of an arrangement of two conducting electrodes separated by a gap usually filled with a gas such as air, designed to allow an electric spark to pass between the conductors. When the potential difference between the conductors exceeds the breakdown voltage of the gas within the gap, a spark forms, ionizing the gas and drastically reducing its electrical resistance. An electric current then flows until the path of ionized gas is broken or the current reduces below a minimum value called the "holding current". This usually happens when the voltage drops, but in some cases occurs when the heated gas rises, stretching out and then breaking the filament of ionized gas. Usually, the action of ionizing the gas is violent and disruptive, often leading to sound, light and heat.

An ignition system generates a spark or heats an electrode to a high temperature to ignite a fuel-air mixture in spark ignition internal combustion engines, oil-fired and gas-fired boilers, rocket engines, etc. The widest application for spark ignition internal combustion engines is in petrol (gasoline) road vehicles such as cars and motorcycles.

Brayton cycle Thermodynamic cycle

The Brayton cycle is a thermodynamic cycle that describes the operation of certain heat engines that have air or some other gas as their working fluid. The original Brayton engines used a piston compressor and piston expander, but modern gas turbine engines and airbreathing jet engines also follow the Brayton cycle. Although the cycle is usually run as an open system, it is conventionally assumed for the purposes of thermodynamic analysis that the exhaust gases are reused in the intake, enabling analysis as a closed system.

A combustion chamber is part of an internal combustion engine in which the fuel/air mix is burned. For steam engines, the term has also been used for an extension of the firebox which is used to allow a more complete combustion process.

Steam explosion Explosion created from a violent boiling of water

A steam explosion is an explosion caused by violent boiling or flashing of water or ice into steam, occurring when water or ice is either superheated, rapidly heated by fine hot debris produced within it, or heated by the interaction of molten metals. Pressure vessels, such as pressurized water (nuclear) reactors, that operate above atmospheric pressure can also provide the conditions for a steam explosion. The water changes from a solid or liquid to a gas with extreme speed, increasing dramatically in volume. A steam explosion sprays steam and boiling-hot water and the hot medium that heated it in all directions, creating a danger of scalding and burning.

Ignition coil Automobile fuel ignition system component

An ignition coil is an induction coil in an automobile's ignition system that transforms the battery's voltage to the thousands of volts needed to create an electric spark in the spark plugs to ignite the fuel. Some coils have an internal resistor, while others rely on a resistor wire or an external resistor to limit the current flowing into the coil from the car's 12-volt supply. The wire that goes from the ignition coil to the distributor and the high voltage wires that go from the distributor to each of the spark plugs are called spark plug wires or high tension leads. Originally, every ignition coil system required mechanical contact breaker points and a capacitor (condenser). More recent electronic ignition systems use a power transistor to provide pulses to the ignition coil. A modern passenger automobile may use one ignition coil for each engine cylinder, eliminating fault-prone spark plug cables and a distributor to route the high voltage pulses.

Pilot light

A pilot light is a small gas flame, usually natural gas or liquefied petroleum gas, which serves as an ignition source for a more powerful gas burner. Originally a pilot light was kept permanently alight, but this wastes gas. Now it is more common to light a burner electrically, but gas pilot lights are still used when a high energy ignition source is necessary, as in when lighting a large burner.

Thermal power station Power plant that generates electricity from heat energy

A thermal power station is a power station in which heat energy is converted to electricity. Typically, heat is used to boil water in a large pressure vessel to produce high-pressure steam, which drives a steam turbine connected to an electrical generator. The low-pressure exhaust from the turbine passes through a steam condenser and is recycled to where it was heated. This is known as a Rankine cycle. Natural gas can also be burnt directly in a gas turbine similarly connected to a generator.

Forced-air HVAC system

A forced-air central heating system is one which uses air as its heat transfer medium. These systems rely on ductwork, vents, and plenums as means of air distribution, separate from the actual heating and air conditioning systems. The return plenum carries the air from several large return grills (vents) to a central air handler for re-heating. The supply plenum directs air from the central unit to the rooms which the system is designed to heat. Regardless of type, all air handlers consist of an air filter, blower, heat exchanger/element/coil, and various controls. Like any other kind of central heating system, thermostats are used to control forced air heating systems.

Hot-bulb engine Internal combustion engine

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Coal burner

A coal burner is a mechanical device that burns pulverized coal into a flame in a controlled manner. Coal burner is mainly composed of pulverized coal machine, host of combustion machine control system, ignition system, the crater and others.

Internal combustion engine Engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber

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Pellet heating is a heating system in which wood pellets are combusted. Other pelletized fuels such as straw pellets are used occasionally. Today's central heating system which run on wood pellets as a renewable energy source are comparable in operation and maintenance of oil and gas heating systems.

Industrial furnace Device used for providing heat in industrial applications

An industrial furnace, also known as a direct heater or a direct fired heater, is a device used to provide heat for an industrial process, typically higher than 400 degrees Celsius. They are used to provide heat for a process or can serve as reactor which provides heats of reaction. Furnace designs vary as to its function, heating duty, type of fuel and method of introducing combustion air. Heat is generated by an industrial furnace by mixing fuel with air or oxygen, or from electrical energy. The residual heat will exit the furnace as flue gas. These are designed as per international codes and standards the most common of which are ISO 13705 / American Petroleum Institute (API) Standard 560. Types of industrial furnaces include batch ovens, vacuum furnaces, and solar furnaces. Industrial furnaces are used in applications such as chemical reactions, cremation, oil refining, and glasswork.

References

  1. "Thermopride Oil Furnaces". thermopride.com. March 28, 2018. Retrieved March 28, 2018.
  2. James L. Kittle (1990). Home Heating & Air Conditioning Systems. McGraw-Hill Professional. ISBN   0-8306-3257-3.
  3. "Beckett Burner Corp". beckettcorp.com/. March 28, 2018.
  4. "Robert S. BABINGTON Nebulizer Fuel Burner". 1976.