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Title: DURABILITY OF VERY LOW CAPACITY PRESSURE ATOMIZED FUEL NOZZLES USED WITH LOW FIRING RATE RESIDENTIAL OIL BURNERS.

Abstract

Brookhaven National Laboratory (BNL), working for the United States Department of Energy (DOE), has conducted a preliminary evaluation of the potential of very low fuel input capacity Simplex type pressure atomizing nozzles for use with oil burners designed for residential boilers, furnaces and water heaters. These nozzles under suitable conditions can be sufficiently reliable to enable new heating system designs. This would allow for the design of heating appliances that match the smaller load demands of energy efficient homes built with modern components and architectural systems designed to minimize energy use. When heating systems are installed with excessive capacity, oversized by three to four times the load, the result is a loss of up to ten percent as compared to the rated appliance efficiency. The use of low capacity nozzles in systems designed to closely match the load can thereby result in significant energy savings. BNL investigated the limitations of low flow rate nozzles and designed long-term experiments to see if ways could be determined that would be beneficial to long-term operation at low input capacities without failures. In order to maximize the potential for success the best possible industry practices available were employed. Low flow rate nozzles primarily failmore » by blockage or partial blockage of internal fuel flow passages inside the nozzle. To prevent any contaminants from entering the nozzle BNL investigated the geometry and critical dimensions and the current sate of the art of fuel filter design. Based on this investigation it was concluded that the best available filters should be more than capable of filtering contaminants from the fuel prior to entering the oil burner itself. This position was indeed validated based on the long-term trials conducted under this study no evidence resulted to change our position. It is highly recommended that these filters rated at 10 microns and with large filter capacity (surface area), should be used with all oil burner installations. The other possible failure mode had been attributed to fuel degradation and this became the main focus of the evaluation. The degradation of fuel usually occurs faster under higher temperature conditions. To preclude this as much as possible controls that provided for a post-purge of combustion airflow after burner shut down were selected. This provided a short period of time where the burner's combustion air blower continues to operate after the flame has gone out. This tends to cool the nozzle and in turn the fuel inside the small flow pathways inside the nozzle components. This study concludes that the use of low capacity nozzles is possible but only when the temperature and thermal mass environment of the combustion chamber result in a relatively ''cool'' condition. This was accomplished in one long-term experiment that essentially operated for a full heating season equivalent with no evidence of nozzle plugging or failure. The nozzle body surface temperature was kept at or below 150 F during the duration of the trial. On the other hand, a second system was studied that ended in a partial nozzle blockage and a system failure. In this ''hot environment'' system the nozzle body temperature reached 210 F. This occurred at close to a full heating season equivalent, yet it still would have resulted in a no-heat complaint by the homeowner.« less

Authors:
Publication Date:
Research Org.:
Brookhaven National Lab. (BNL), Upton, NY (United States)
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
912626
Report Number(s):
BNL-79185-2007-IR
R&D Project: 13745; BT0101000; TRN: US200801%%1110
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
02 PETROLEUM; APPLIANCES; BLOWERS; BODY TEMPERATURE; BOILERS; BURNERS; CAPACITY; COMBUSTION; COMBUSTION CHAMBERS; EFFICIENCY; FLOW RATE; FURNACES; HEATING; HEATING SYSTEMS; NOZZLES; OIL BURNERS; THERMAL MASS; WATER HEATERS

Citation Formats

MCDONALD,R.J.. DURABILITY OF VERY LOW CAPACITY PRESSURE ATOMIZED FUEL NOZZLES USED WITH LOW FIRING RATE RESIDENTIAL OIL BURNERS.. United States: N. p., 2007. Web. doi:10.2172/912626.
MCDONALD,R.J.. DURABILITY OF VERY LOW CAPACITY PRESSURE ATOMIZED FUEL NOZZLES USED WITH LOW FIRING RATE RESIDENTIAL OIL BURNERS.. United States. doi:10.2172/912626.
MCDONALD,R.J.. Tue . "DURABILITY OF VERY LOW CAPACITY PRESSURE ATOMIZED FUEL NOZZLES USED WITH LOW FIRING RATE RESIDENTIAL OIL BURNERS.". United States. doi:10.2172/912626. https://www.osti.gov/servlets/purl/912626.
@article{osti_912626,
title = {DURABILITY OF VERY LOW CAPACITY PRESSURE ATOMIZED FUEL NOZZLES USED WITH LOW FIRING RATE RESIDENTIAL OIL BURNERS.},
author = {MCDONALD,R.J.},
abstractNote = {Brookhaven National Laboratory (BNL), working for the United States Department of Energy (DOE), has conducted a preliminary evaluation of the potential of very low fuel input capacity Simplex type pressure atomizing nozzles for use with oil burners designed for residential boilers, furnaces and water heaters. These nozzles under suitable conditions can be sufficiently reliable to enable new heating system designs. This would allow for the design of heating appliances that match the smaller load demands of energy efficient homes built with modern components and architectural systems designed to minimize energy use. When heating systems are installed with excessive capacity, oversized by three to four times the load, the result is a loss of up to ten percent as compared to the rated appliance efficiency. The use of low capacity nozzles in systems designed to closely match the load can thereby result in significant energy savings. BNL investigated the limitations of low flow rate nozzles and designed long-term experiments to see if ways could be determined that would be beneficial to long-term operation at low input capacities without failures. In order to maximize the potential for success the best possible industry practices available were employed. Low flow rate nozzles primarily fail by blockage or partial blockage of internal fuel flow passages inside the nozzle. To prevent any contaminants from entering the nozzle BNL investigated the geometry and critical dimensions and the current sate of the art of fuel filter design. Based on this investigation it was concluded that the best available filters should be more than capable of filtering contaminants from the fuel prior to entering the oil burner itself. This position was indeed validated based on the long-term trials conducted under this study no evidence resulted to change our position. It is highly recommended that these filters rated at 10 microns and with large filter capacity (surface area), should be used with all oil burner installations. The other possible failure mode had been attributed to fuel degradation and this became the main focus of the evaluation. The degradation of fuel usually occurs faster under higher temperature conditions. To preclude this as much as possible controls that provided for a post-purge of combustion airflow after burner shut down were selected. This provided a short period of time where the burner's combustion air blower continues to operate after the flame has gone out. This tends to cool the nozzle and in turn the fuel inside the small flow pathways inside the nozzle components. This study concludes that the use of low capacity nozzles is possible but only when the temperature and thermal mass environment of the combustion chamber result in a relatively ''cool'' condition. This was accomplished in one long-term experiment that essentially operated for a full heating season equivalent with no evidence of nozzle plugging or failure. The nozzle body surface temperature was kept at or below 150 F during the duration of the trial. On the other hand, a second system was studied that ended in a partial nozzle blockage and a system failure. In this ''hot environment'' system the nozzle body temperature reached 210 F. This occurred at close to a full heating season equivalent, yet it still would have resulted in a no-heat complaint by the homeowner.},
doi = {10.2172/912626},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue May 01 00:00:00 EDT 2007},
month = {Tue May 01 00:00:00 EDT 2007}
}

Technical Report:

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  • This report describes technical advances made to the concept of a low pressure, air atomized oil burner for home heating applications. Currently all oil burners on the market are of the pressure atomized, retention head type. These burners have a lower firing rate limit of about 0.5 gallons per hour of oil, due to reliability problems related to small flow passage sizes. High pressure air atomized burners have been shown to be one route to avoid this problem but air compressor cost and reliability have practically eliminated this approach. With the low pressure air atomized burner the air required formore » atomization can be provided by a fan at 5-8 inches of water pressure. A burner using this concept, termed the Fan-Atomized Burner or ''FAB'' has been developed and is currently being commercialized. In the head of the FAB, the combustion air is divided into three parts, much like a conventional retention head burner. This report describes development work on a new concept in which 100% of the air from the fan goes through the atomizer. The primary advantage of this approach is a great simplification of the head design. A nozzle specifically sized for this concept was built and is described in the report. Basic flow pressure tests, cold air velocity profiles, and atomization performance have been measured. A burner head/flame tube has been developed which promotes a toroidal recirculation zone near the nozzle for flame stability. The burner head has been tested in several furnace and boiler applications over the firing rate range 0.2 to 0.28 gallons per hour. In all cases the burner can operate with very low excess air levels (under 10%) without producing smoke. Flue gas NO{sub x} concentration varied from 42 to 62 ppm at 3% O{sub 2}. The concept is seen as having significant potential and planned development efforts are discussed.« less
  • This report describes technical advances made to the concept of a low pressure, air atomized oil burner for home heating applications. Currently all oil burners on the market are of the pressure atomized, retention head type. These burners have a lower firing rate limit of about 0.5 gallons per hour of oil, due to reliability problems related to small flow passage sizes. High pressure air atomized burners have been shown to be one route to avoid this problem but air compressor cost and reliability have practically eliminated this approach. With the low pressure air atomized burner the air required formore » atomization can be provided by a fan at 5--8 inches of water pressure. A burner using this concept, termed the Fan-Atomized Burner or FAB has been developed and is currently being commercialized. In the head of the FAB, the combustion air is divided into three parts, much like a conventional retention head burner. This report describes development work on a new concept in which 100% of the air from the fan goes through the atomizer. The primary advantage of this approach is a great simplification of the head design. A nozzle specifically sized for this concept was built and is described in the report. Basic flow pressure tests, cold air velocity profiles, and atomization performance have been measured. A burner head/flame tube has been developed which promotes a torroidal recirculation zone near the nozzle for flame stability. The burner head has been tested in several furnace and boiler applications over the tiring rate range 0.2 to 0.28 gallons per hour. In all cases the burner can operate with very low excess air levels (under 10%) without producing smoke. Flue gas NO{sub x} concentration varied from 42 to 62 ppm at 3% 0{sub 2}. The concept is seen as having significant potential and planned development efforts are discussed.« less
  • The residential oil burner market is currently dominated by the pressure-atomized retention head burner. At low firing rates, pressure-atomizing nozzles suffer rapid fouling of the small internal passages, leading to bad spray patterns and poor combustion performance. To overcome the low input limitations of conventional burners, a low-pressure air-atomized burner has been developed that can operate at firing rates, as low as 0.25 gallons of oil per hour (10 kW). In addition, the burner can be operated in a high/low firing rate mode. Field tests with this burner have been conducted at a fixed input rate of 0.35 gph (14more » kW) with a sidewall vented boiler/water storage tank combination. At the test home, instrumentation was installed to measure fuel and energy flows and record trends in system temperatures. Laboratory efficiency testing with water heaters and boilers has been completed using standard single-purpose and combined appliance test procedures. The tests quantify benefits due to low firing rates and other burner features. A two-stage oil burner gains a strong advantage in rated efficiency while maintaining capacity for high domestic hot water and space-heating loads.« less
  • The residential oil burner market is currently dominated by the pressure-atomized, retention head burner. At low firing rates pressure atomizing nozzles suffer rapid fouling of the small internal passages, leading to bad spray patterns and poor combustion performance. To overcome the low input limitations of conventional burners, a low pressure air-atomized burner has been developed watch can operate at fining rates as low as 0.25 gallons of oil per hour (10 kW). In addition, the burner can be operated in a high/low fining rate mode. Field tests with this burner have been conducted at a fixed input rate of 0.35more » gph (14 kW) with a side-wall vented boiler/water storage tank combination. At the test home, instrumentation was installed to measure fuel and energy flows and record trends in system temperatures. Laboratory efficiency testing with water heaters and boilers has been completed using standard single purpose and combined appliance test procedures. The tests quantify benefits due to low firing rates and other burner features. A two stage oil burner gains a strong advantage in rated efficiency while maintaining capacity for high domestic hot water and space heating loads.« less