Rotary kinetic fluid motors or pumps – Working fluid passage or distributing means associated with... – Casing having tangential inlet or outlet
Patent
1983-09-21
1985-10-29
Garrett, Robert E.
Rotary kinetic fluid motors or pumps
Working fluid passage or distributing means associated with...
Casing having tangential inlet or outlet
415208, F04D 2944
Patent
active
045498482
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an arrangement for radial fans, particularly for use in oil-burners or in other applications with corresponding performance requirements. More specifically, the invention relates to a fan arrangement comprising a fan housing which, considered radially from the axial line of the fan, is in the form of a spiral with one end wall developed into an air intake; a drum-shaped wheel which is concentric with the axial line, is designed to rotate in the direction in which the spiral becomes larger, and has a plurality of forward-curving blades arranged in a ring and extending in the axial direction of the wheel from an inner end plate located at the base of the fan housing up to the outer end of the wheel where the latter has an opening facing towards the intake through which the air flows into the inside of the ring of blades.
For fans which are to be used in oil-burners, especially those for domestic boilers and other smaller appliances which operate intermittently, intensive development work has been carried out in recent times in an attempt to satisfy the demand for better performance. This concerns above all the pressure which a fan of a certain size should produce at the quantity of air suited to the appliance--the normal operating level of the fan. The fan pressure is very significant for rapid and effective combustion of the finely-dispersed oil which is delivered by the nozzle of the oil-burner, and it is also an important aim that the quantity of air delivered by the fan should vary as little as possible with the counter-pressure prevailing in the combustion chamber. The demand for keeping the quantity of air as constant as possible consequently means that the characteristic curve of the oil-burner fan (pressure as a function of quantity) should rise sharply through the operating level specified for the appliance.
The demand for a high fan pressure in the said type of appliance is motivated especially by the influence which the outside atmospheric conditions have on the starting-up function of an oil-burner. It is well-known that if the weather is damp and cold it becomes more difficult than in more favourable weather conditions to drive out the air which remains behind in the chimney and the combustion chamber after a stoppage. Even if ignition of the burner is preceded by a special venting phase, overcoming the counter-pressure which this "cold block" presents accentuates the need for a fan which, when the quantity of air flowing out is small or approaches nil, is able to produce a pressure many times greater than that which is maintained during operation at or around the operating level.
Since a radial fan produces a pressure which is proportional to the peripheral speed of the wheel, that is, is dependent on the diameter of the wheel, any improvement in relation to the pressure means that it is possible to avoid an otherwise inevitable increase in the diameter, or expressed another way, that it is possible to allow an oil-burner fan of a specific size to operate at a higher operating level, i.e. up to a higher capacity of oil per unit of time, than formerly. The solution which satisfies the demand for high fan pressure is consequently also valuable from the point of view of saving space and money.
A factor which makes matters more difficult in this connection is the noise which the fan produces and which normally increases with the pressure. However, for appliances in houses and similarly sensitive surroundings a fan design which produces an increased air pressure at the sacrifice of a low noise-level is not an acceptable solution. A higher noise-level also betrays an unnecessarily high consumption of energy in the fan and it is therefore appropriate to find a design which combines an improvement of the pressure/quantity of air performance of the fan while maintaining, or if possible reducing, the noise-level and keeping the consumption of energy low.
A large number of different designs have been produced over the years with the object of improving radial fans for oil-
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Garrett Robert E.
Li H. Edward
Nilles James E.
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