DURABILITY OF VERY LOW CAPACITY PRESSURE ATOMIZED FUEL NOZZLES USED WITH LOW FIRING RATE RESIDENTIAL OIL BURNERS.
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.
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States)
- Sponsoring Organization:
- Doe - Office Of Science
- DOE Contract Number:
- DE-AC02-98CH10886
- OSTI ID:
- 912626
- Report Number(s):
- BNL-79185-2007-IR; R&D Project: 13745; BT0101000; TRN: US200801%%1110
- Country of Publication:
- United States
- Language:
- English
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