GB2190182A - Burner/injector arrangement - Google Patents

Abstract

A burner/injector arrangement for use with oil fired boilers comprises a pair of air suction fans (11,25) arranged in tandem and each coupled to a compressor (20,27) so that air can be blown into the compressor (20,27) to create an axially disposed vortex air flow pattern issuing from each compressor (20,27). A fuel injector head (30) is arranged in-line with the two-stage compressor (20,27) to inject fuel into the centre of the air vortex along the common longitudinal axis and means are provided to cause ignition of the air/fuel mixture. A transfer chamber (22) enclosing arcuate blades (23) is provided between the outlet of the first compression stage (20) and the inlet of the fan (25) of the second compression stage (27) which causes a change in the direction of the pressurized air outflowing from the first compression stage (20) so as to deliver a rotating mass of pressurized air into the fan inlet of the second compression stage (27). <IMAGE>

Description

SPECIFICATION A burner/injector arrangement This invention relates to a burner/injector arrangement suitable for use with boilers burning for example oil or gas.

In our U.K. Patent No. 1553767 we disclose a burner/injector arrangement comprising an air suction fan axially coupled to a compressor whereby air can be blown into the compressor to create an axially disposed vortex air flow pattern issuing from the compressor, a fuel injector head arranged in-line with the compressor and the fan to inject fuel into the centre of the vortex along the common longitudinal axis, and means for cuasing ignition of the air/fuel mixture.

It is an object of the present invention to provide an improved burner/injector arrangement.

According to the present invention there is provided a burner/injector arrangement for use especially but not exclusively with oil fired boilers and comprising a pair of air suction fans arranged in tandem and each axially coupled to a compressor whereby air can be blown into the compressor to create an axially disposed vortex air flow pattern issuing from each compressor, the tandem fan and compressor arrangements thus defining a twostage compressor with a fuel injector head arranged in-line with the two-stage compressor to inject fuel into the centre of the air vortex along the common longitudinal axis, means being provided to cause ignition of the air/fuel mixture, and with a transfer chamber between the outlet of the compressor of the first compression stage and the inlet of the fan of the second compression stage, which transfer chamber causes a change in the direction of the pressurized air outflowing from the first compression stage so as to deliver a rotating mass of pressurized air into the fan inlet of the second compression stage.

As a result of the present invention no energy of the second compression stage is absorbed in starting the air in motion and there is an improved pressure to diameter characteristic of the second stage of the two-stage compressor.

Preferably, the transfer chamber includes vanes which cause the pressurized air outflowing from the first compression stage to take up a swirl or vortex pattern before entering the second stage of the two-stage compressor. This ensures that little or not energy of this second stage is absorbed in starting the entry air in motion and giving improved pressure to diameter characteristics for the second stage.

Preferably, the two fans are driven by a common motor interposed therebetween. The motor is thus subjected to the outgoing air from the first compression stage which serves to cool the motor and thus dispense with the need for a separate cooling fan.

Preferably, a ratio of two to three exists between the number of blades on the fan of the first compression stage and the number of blades on the fan of the second compression stage.

Preferably, the relative settings of the fans on a common shaft are predetermined to provide a relativity between the air flow characteristics and the tip speed and pressure produced by the respective fans.

Both the ratio between the number of blades on each fan and the relativity produce a balance of sound pressure from each fan to provide a degree of mutual pressure wave cancellation. As a result the burner/injector arrangement according to the present invention is unusually quiet in operation. For example, it may have a sound spectrum in octaves between 31.5 hertz and 8K hertz to produce a low noise rating.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a half sectional view through a burner/injector arrangement according to the present invention; Figures 2, 3 and 4 are respectively a side view, a plan view and an end view of the burner/injector arrangement according to the present invention; and Figure 5 is a part sectional view through a second embodiment of burner/injector arrangement according to the present invention.

As shown in Fig. 1, a burner/injector arrangement comprises a casing 10 mounting a two-stage compressor, namely a first stage A and a second stage B.

The first stage A comprises a suction fan 11 connected by a flanged plate 12 to a motor 13. The suction fan is connected to a rear output shaft 14 of the motor 13 by a central sleeve 15 of the flanged plate 12 and a clamp 16.

The suction fan 11 has an integral air inlet chamber or entry eye 17 into which the rear of the fan blades 18 extend. The suction fan may comprise any convenient number of blades but it is preferred that there should be between eight and twelve blades inclusive.

The inlet chamber or eye 17 registers with an air inlet duct 19 connected to the casing 10.

The first compression stage also comprises a compressor 20 rigid with the casing 10 and comprising a series of arcuate blades 21.

Again there can be any convenient number of these blades but it is preferred that there should be either ten or twelve.

The outlet from the compressor of first compression stage A comprises an air transfer chamber 22 which registers with the inlet of the second compression stage B as will be shortly described.

A swirl or vortex producing device is operational within this transfer chamber and comprises a series of arcuate blade 23 fixed to the body of the motor 13 by a mounting arrangement 24. These blades 23 are arced in the sense opposite to the blades 21 of the compressor 20.

The outflowing pressurized air from compression stage A is caused by these blades 23 to swirl in a vortex air flow pattern and as a result of this and the fact that the air enters the second compression stage B as a rotating mass (no energy absorbed in compression stage B in starting the air in motion) the pressure to diameter characteristic of compression stage B is substantially improved.

Compression stage B also comprises a suction fan 25 havin an inlet chamber or eye 26 in register with an immediately adjacent the transfer chamber 22. The suction fan 25 is secured to an output shaft 27 at the front of the motor 13 by a similar arrangement to that securing the suction fan 11 to the shaft 14 of the motor 13 and like parts are indicated by the same references with the suffix "A".

The second compression stage B also comprises a compressor 27 provided with arcuate blades 28. Here again the numbers of the blades 29 of the suction fan 25 and the blades 28 of the compressor 27 conform with those of suction fan 11 and compressor 20.

The fuel injector head and ignition means of the burner/injector arrangement is indicated at 30 and the fuel injector inlet at 31.

The two-stage compressor is hinged to the fuel injector head 30 at 32 so that these two parts of the arrangement can be separated for cleaning and maintenance purposes.

The common motor 13 which is preferably an electric motor lies in the air stream egressing from compression stage A and entering compression stage B so that there is no requirement for a separate cooling fan to be attached to the motor.

It is to be noted that if the capacity of the burner/injector arrangement is reduced there is a reduction of the volume of air passing over the motor 13 and consequently a reduction in cooling with the result that there is an increase in the power factor of the motor.

However, in a second embodiment of the invention, as shown in Fig. 5, a motor 35 is located externally of the casing 10B of the burner/injector arrangement. This arrangement of components enables higher fan pressures to be produced from the same size of components of the arrangem,ent by increasing the fan speed. Apart from this change in the location of the motor 35, all the other components of the burner/injector arrangement are similar to those described with reference to Fig. 1 and like parts are indicated by the same references with the suffix "B".

With the arrangement according to the present invention the position of the fan blades 18 and 29 can be indexed relative to one another and preset to provide a relativity between the air flow characteristics, the blade tip speed and the air pressure produced in compression stages A and B. This relativity produces a balance of sound pressure from each suction fan 11 and 25 to provide a degree of mutual pressure wave cancellation which causes the burner/injector arrangement to be especially quiet in operation. For example, its sound spectrum when measured analytically by octaves between 31.5 hertz and 8K hertz produces a low noise rating.

A low noise rating can also be achieved in a different way by altering the length of the blades 18 and 29 relative to one another and the diameter of the air inlet eye 17. It has been found that if the length of the blades 18 of the suction fan 11 are made approximately 10% longer than the length of the blades 29 of the suction fan 25 that the noise level of the arrangement is significantly reduced. The diameter of the air inlet eye 17 need to be adjusted to cope with the corresponding variation in the size of the fan 11.

It has also been found that the use of dissimilar blade numbers for the fans 11 and 25 will also produce a significant reduction in the noise level, without the need necessarily to index the fan blades 18 and 29 relative to one another. A ratio of 2:3 between the number of blades 18 on the first suction fan 11 and the number of blades 29 on the second suction fan 25 has been found to give the best results. For example, the first suction fan 11 can be provided with eight blades 18 and the second suction fan 25 with twelve blades 29.

Finally, the burner/injector arrangement according to the present invention provides a wide range of desirable combinations of volume air flow and high output pressure for oil fired boilers and furnaces with which the arrangement can be used.

Claims (7)

1. A burner/injector arrangement for use especially but not exclusively with oil fired boilers and comprising a pair of air suction fans arranged in tandem and each axially coupled to a compressor whereby air can be blown into the compressor to create an axially disposed vortex air flow pattern issuing from each compressor, the tandem fan and compressor arrangements thus defining a twostage compressor with a fuel injector head arranged in-line with the two-stage compressor to inject fuel into the centre of the air vortex along the common longitudinal axis, means being provided to cause ignition of the air/fuel mixture, and with a transfer chamber between the outlet of the compressor of the first compression stage and the inlet of the fan of the second compression stage, which transfer chamber causes a change in the direction of the pressurized air outflowing from the first compression stage so as to deliver a rotating mass of pressurized air into the fan inlet of the second compression stage.

2. An arrangement as claimed in claim 1, in which the transfer chamber includes vanes which cause the pressurized air outflowing from the first compression stage to take up a swirl or vortex pattern before entering the second stage of the two-stage compressor.

3. An arrangement as claimed in claim 1 or claim 2, in which the two fans are driven by a common motor interposed therebetween.

4. An arrangement as claimed in any one of claims 1 to 3, in which the relative settings of the two fans on a common shaft are predetermined to provide a relativity between the air flow characteristics and the tip speed and pressure produced by the respective fans.

5. An arrangement as claimed in any one of claims 1 to 4, in which a ratio of two to three exists between the number of blades on the fan of the first compression stage and the number of blades on the fan of the second compression stage.

6. An arrangement as claimed in any one of claims 1 to 5, in which the length of the blads on the fan of the first compression stage is approximately 10% longer than the length of the blades on the fan of the second compression stage.

7. A burner/injector arrangement for use especially but not exclusively with oil fired boilers substantially as hereinbefore described with reference to Figs. 1 to 4 or with reference to Fig. 5 of the accompanying drawings.