Combustion – Process of combustion or burner operation – Starting or shutdown procedure
Patent
1991-07-16
1992-11-24
Yeung, James C.
Combustion
Process of combustion or burner operation
Starting or shutdown procedure
431 22, 431 76, 431 78, 431302, 126 96, F23N 520
Patent
active
051658836
DESCRIPTION:
BRIEF SUMMARY
FIELD AND BACKGROUND OF THE INVENTION
The invention relates to a process of monitoring and ensuring the safe operation of unvented stoves, particularly of kerosene heaters, within enclosed spaces both in the normal heating condition in which the height of the flame produced by the burner is within a predetermined range, and when radiation-responsive means detect flame heights outside said range, and in operation outside the normal heating condition, with flame heights higher or lower than the predetermined range causing corresponding control signals to be generated and to be coupled to an electronic control circuit so as to cause the normal heating condition to be restored, on the one hand, and to cause a warning signal to be generated and the burner to be shut down on the other, after a corresponding timeout in case the burner consistently operates outside the predetermined flame height range for a predetermined period of time.
Further, the invention relates to apparatus for practicing the inventive process.
The European countries have recently tightened safety regulations relative to indoor air pollution caused by unvented ovens and particularly by kerosene heaters; they require such unvented ovens--such as kerosene heaters with one- or two-stage burners--to be monitored strictly for safe operation (see U.S. Pat. No. 4,390,003).
There have been known safety systems for ovens and particularly for kerosene heaters (WO 86/05860) in which, once the oven or heater has attained its normal operation, the height of the flames the burner produces may exceed a predetermined range and/or the heating means as well as the burner head and the associated piping may heat up to the point where the oven assumes an undesirable operating condition. The prior safety apparatus includes sensing means for detecting flame heights higher than a predetermined maximum and for providing a corresponding measuring and/or control signal which is coupled to actuating means responsive thereto to return the kerosene heater to the desired operating state or to shut it down. For a kerosene heater with a one-stage burner, the sensing means in the prior safety apparatus comprises two light sensors or thermal radiation detecting sensors each associated with an upper or lower limit of said predetermined range of flame heights in the normal operation of the kerosene heater. The burner's wick is re-adjusted manually or in accordance with the measuring signals generated by the light sensors as the flame height exceeds the predetermined flame height range; alternatively, the burner is shut down positively by means of a drop bar as soon as the flame height has exceeded the predetermined flame height range continuously for a pre-determined period of time.
This prior safety apparatus is based solely on a radiation-responsive detection of flame height. However, it does not satisfy the latest safety regulations as it has a number of inherent uncertainties. For example, if the burner is operated from the beginning at the lowest possible flame height, this condition will not be detected by the light sensor associated with the lower limit of the predetermined flame height range. Once the burner has burned at its lowest flame height for an extended period of time because the user has forgotten to shut down the heater, for example, there exists a great danger of the indoor space air containing inadmissible levels of CO.sub.2 since the absence of a light-responsive minimum flame height detection feature prevents the heater from being shut down automatically.
Since the wick fabric always includes irregularities, it is possible for the burner flame during normal heater operation to temporarily exceed the top limit of the predetermined flame height range--which may cause the prior safety apparatus to prematurely automatically shut down the burner although the maximum permissible CO.sub.2 level in the indoor air has not yet been reached. In an oven or heater equipped with the prior safety device, such preliminary burner shut down results in the emission of foul
REFERENCES:
patent: 4392813 (1983-07-01), Tanaka et al.
patent: 4412809 (1983-11-01), Yamaguchi et al.
patent: 4451228 (1984-05-01), Wada et al.
patent: 4534727 (1985-08-01), Imajima
patent: 4770628 (1988-09-01), Ohkura
Toyotomi Co. Ltd.
Yeung James C.
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