GB2174456A

GB2174456A - Gas injection devices

Info

Publication number: GB2174456A
Application number: GB08510967A
Authority: GB
Inventors: Arthur Chesworth; James Stanford
Original assignee: Robinson Willey Ltd
Current assignee: Robinson Willey Ltd
Priority date: 1985-04-30
Filing date: 1985-04-30
Publication date: 1986-11-05
Also published as: GB2174456B; GB8510967D0

Abstract

A gas injector (13) directs gas into a mixing tube. Over-size opening (15) allows air to be entrained into the gas stream. The position of injector (13) relative to opening (15) can be varied by sliding shroud (17) along to effectively extend the injector. This alters the distance between the opening (15) and injector (13) and thus alters the amount of air entrained. The degree of aeration of flames fed from the mixing tube may be thus varied by manual control (18, 19) adjusting the position of the shroud. Gas fires of the kind in which flames pass through coal or log simulations may have an injector of this kind, allowing the user to select from low aeration floppy yellow flames to fully aerated hot blue flames. <IMAGE>

Description

SPECIFICATION Gas injection devices This invention relates to gas injection devices of the kind in which flowing gas is used to entrain a supply of combustion air.

The invention provides a gas injection device comprising an injector, an air inlet distanced from said injector by a gap such that gas flowing through the injector entrains air through said air inlet in a proportion which is affected by the length of said gap and the characteristics of the gas stream, and means for varying the length of said gap whereby to vary the proportion of entrained air to gas.

Preferably said means for varying the length of the gap comprises extension means for varying the effective length of the injector.

The said extension may comprise a thin-walled sleeve which is a sliding fit over the injector, the said gap being varied by moving the sleeve beyond the end of the injector into the throat of the mixing tube.

There may be a manual control for extending and retracting the sleeve.

The invention also extends to a gas fire of the kind in which flames pass through a realistic simulation of coal or logs, having a gas injection device as set forth above, whereby the degree of aeration of the flames can be varied.

A specific embodiment of the invention is shown diagrammatically in the accompanying drawing.

A gas supply tube (11) is directed into a mixing tube (12) and terminates in a fixed injector (13) directing gas in the direction of arrow A along the mixing tube. An end plate (14) of the mixing tube has an over-size opening (15) through which the injector passes allowing air to pass into the mixing tube in the direction of arrow B. The gas flowing in the direction of arrow A pulls air into the mixing tube through openings (15). As the gas and air pass along the mixing tube (12) they mix.

The mixing tube leads to one or more gas burners (not shown) where the mixture burns.

The embodiment shown is intended for use in a gas fire of the kind in which flames pass through a realistic simulation of coal or logs, which simulation does not burn, but becomes hot and radiates heat. As is well known, gas flames which result from burning gas either unmixed with air or mixed with an inadequate supply of air burn with a floppy yellow flame which is closely similar to the flames of a coal or log fire. Such flames, however, heat the simulated coal or logs only inefficiently. A heat output efficiency only of the order of 12% to 15% may be achieved. Better efficiencies are achieved by burning fully aerated gas, which, however, provides a hot blue flame which does not much resemble the flames of a real coal or log fire.

The arrangement shown in the drawing places the degree of aeration of the gas under the control of the user, by providing a variable aeration control. This comprises a tubular shroud (17) which is a sliding fit over the outside of the injector (13). Secured to the shroud is a control rod (18) which ends in a knob (19). Push and pull motion of knob (19), as indicated by arrows C, moves the shroud back and forth along the injector (13) in the manner indicated by arrows D. The shroud is formed of material thin enough not to interfere seriously with the air flowing through opening (15) when lying inside said opening.

As can be seen from the drawing, when the shroud is pushed forward so that it extends a distance X beyond the end of injector (13), it effectively lengthens the gap between the air inlet and the gas inlet by distance X. Since it is the action of the flowing gas which pulls air into the air inlet it is found that the greater the gap the smaller the amount of air which is entrained. It is found that when the injector is designed to provide a fully aerated gas/air mixture, a shroud which extends the gap by 25 mm reduces the aeration to such a degree as to change the resulting flame from a hard blue flame to a floppy yellow one. Intermediate types of flame are obtainable from values of X less than 25 mm.Thus the user can at will push or pull knob (19) to obtain blue flames heating the coal or log simulation to a higher temperature, at which more heat is radiated, or floppy yellow flames giving a lower heat output but a more realistic fire simulation, or something between. This control is achieved using only very simple components, not needing any calibration or close tolerances. No index is actually needed for positioning knob (19), since the effect of alteration can be seen very rapidly. However, for the guidance of the user, a simple index can be supplied.

While the embodiment described uses a shroud sliding over a fixed injector, it is within the invention to use an internal extension piece within the injector. Other methods of moving the shroud may also be used, for instance, a rack and pinion drive.

1. A gas injection device comprising an injector, an air inlet distanced from said injector by a gap such that gas flowing through the injector entrains air through said air inlet in a proportion which is affected by the length of the gap and the characteristics of the gas stream, and means for varying the length of said gap whereby to vary the proportion of entrained air to gas.

2. A gas injection device as claimed in claim 1, wherein said means for varying the length of said gap comprises extension means for varying the effective position of the injector.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Gas injection devices This invention relates to gas injection devices of the kind in which flowing gas is used to entrain a supply of combustion air. The invention provides a gas injection device comprising an injector, an air inlet distanced from said injector by a gap such that gas flowing through the injector entrains air through said air inlet in a proportion which is affected by the length of said gap and the characteristics of the gas stream, and means for varying the length of said gap whereby to vary the proportion of entrained air to gas. Preferably said means for varying the length of the gap comprises extension means for varying the effective length of the injector. The said extension may comprise a thin-walled sleeve which is a sliding fit over the injector, the said gap being varied by moving the sleeve beyond the end of the injector into the throat of the mixing tube. There may be a manual control for extending and retracting the sleeve. The invention also extends to a gas fire of the kind in which flames pass through a realistic simulation of coal or logs, having a gas injection device as set forth above, whereby the degree of aeration of the flames can be varied. A specific embodiment of the invention is shown diagrammatically in the accompanying drawing. A gas supply tube (11) is directed into a mixing tube (12) and terminates in a fixed injector (13) directing gas in the direction of arrow A along the mixing tube. An end plate (14) of the mixing tube has an over-size opening (15) through which the injector passes allowing air to pass into the mixing tube in the direction of arrow B. The gas flowing in the direction of arrow A pulls air into the mixing tube through openings (15). As the gas and air pass along the mixing tube (12) they mix. The mixing tube leads to one or more gas burners (not shown) where the mixture burns. The embodiment shown is intended for use in a gas fire of the kind in which flames pass through a realistic simulation of coal or logs, which simulation does not burn, but becomes hot and radiates heat. As is well known, gas flames which result from burning gas either unmixed with air or mixed with an inadequate supply of air burn with a floppy yellow flame which is closely similar to the flames of a coal or log fire. Such flames, however, heat the simulated coal or logs only inefficiently. A heat output efficiency only of the order of 12% to 15% may be achieved. Better efficiencies are achieved by burning fully aerated gas, which, however, provides a hot blue flame which does not much resemble the flames of a real coal or log fire. The arrangement shown in the drawing places the degree of aeration of the gas under the control of the user, by providing a variable aeration control. This comprises a tubular shroud (17) which is a sliding fit over the outside of the injector (13). Secured to the shroud is a control rod (18) which ends in a knob (19). Push and pull motion of knob (19), as indicated by arrows C, moves the shroud back and forth along the injector (13) in the manner indicated by arrows D. The shroud is formed of material thin enough not to interfere seriously with the air flowing through opening (15) when lying inside said opening. As can be seen from the drawing, when the shroud is pushed forward so that it extends a distance X beyond the end of injector (13), it effectively lengthens the gap between the air inlet and the gas inlet by distance X. Since it is the action of the flowing gas which pulls air into the air inlet it is found that the greater the gap the smaller the amount of air which is entrained. It is found that when the injector is designed to provide a fully aerated gas/air mixture, a shroud which extends the gap by 25 mm reduces the aeration to such a degree as to change the resulting flame from a hard blue flame to a floppy yellow one. Intermediate types of flame are obtainable from values of X less than 25 mm.Thus the user can at will push or pull knob (19) to obtain blue flames heating the coal or log simulation to a higher temperature, at which more heat is radiated, or floppy yellow flames giving a lower heat output but a more realistic fire simulation, or something between. This control is achieved using only very simple components, not needing any calibration or close tolerances. No index is actually needed for positioning knob (19), since the effect of alteration can be seen very rapidly. However, for the guidance of the user, a simple index can be supplied. While the embodiment described uses a shroud sliding over a fixed injector, it is within the invention to use an internal extension piece within the injector. Other methods of moving the shroud may also be used, for instance, a rack and pinion drive. CLAIMS

3. A gas injection device as claimed in claim 2, wherein said injector comprises the end of a cylindrical gas supply tube and said extension means comprises a sleeve which is slideable along the tube.

4. A gas injection device as claimed in claim 3, wherein said gas supply tube is directed into a mixing tube through an over-size opening, the over-size opening comprising the air inlet, the distance the supply tube extends from the over-size opening defining said gap.

5. A gas injection device as claimed in claim 4, wherein said sleeve slides on the outer surface of the tube and is thin enough not to interfere seriously with the air flow.

6. A gas injection device as claimed in any of claims 1 to 5, having a manual control for operating said means for varying the length of said gap.

7. A gas injection device as claimed in any of claims 3 to 5, having a manual control for moving said sleeve along the tube.

8. A gas injection device as claimed in claim 7, wherein said manual control comprises a control rod ending in a control knob.

9. A gas injection device substantially as described hereinbefore with reference to the accompanying drawing.

10. A gas fire of the kind in which flames pass through a realistic simulation of coal or logs, having a gas injection device as claimed in any of claims 1 to 9, whereby the degree of aeration of the flames can be varied.