IE59884B1 - Smoke reducing combustion appliance - Google Patents

Description

The present invention relates to a domestic combustion appliance. The reduction of smoke emissions to atmosphere from domestic combustion appliances is a continuing problem particularly in urban environments.

One object of the present invention is to provide a domestic combustion, appliance which minimises smoke emissions to atmosphere.

According to th® present invention there is provided a combustion appliance comprising a grate for XO supporting a firebed in a first combustion chamber, an ash receiving area defined beneath the grate, a secondary combustion chamber disposed behind said first combustion chamber, the secondary combustion chamber communicating with a flue via a discharge outlet, the first combustion chamber communicating with the secondary combustion chamber via an entry throat disposed at the bottom of th© said first and second combustion chambers, said secondary combustion chamber arranged in- the form of a parallelogram which diverges upwardly from the entry throat to the greatest width of the secondary combustion chamber and converges upwardly from the greatest width of the secondary combustion chamber towards the discharge outlet.

Embodiments of the invention will now be described, by way of example, with reference to the accompanying, drawings, in which: Figure 1 is a vertical cross-section view of a combustion appliance according to the invention? Figure 2 is a diagrammatic view of a damper means used in the apparatus of Figure 1; and Figure 3 is a perspective view of a draught control means used in the apparatus of Figure 1? and Figure 4 is e vertical cross-sectional view of a second embodiment of a combustion appliance according to th® invention.

Referring now to th® drawings and In particular to Figures 1-3 wherein similar numerals have been used to indicate like parts , there is shown therein a combustion appliance generally indicated at 10 according to the invention. The appliance 10 comprises a front upright rectangular frame 11, and a grate 12 for supporting a firebed in a first combustion chamber 13. An ash receiving area 14 is defined beneath the grate 12. A right-angled metal plate 15 Is disposed at the rear 16 of the ash receiving area 14 and supports a forwardly angled refractory brick 17. Another metal plate 18 slopes downwardly. from the brick 17 and is supported, at its lower end 19 on the grate 12.

The plate 18 defines an entry throat 20 to a secondary combustion chamber 21 disposed rearwardly of the first combustion chamber 13. The combustion chamber 21 Is defined by refractory bricks 22,23 which diverge froa the entry throat 20 and also refractory bricks 24,25 which converge towards a discharge outlet 26 at the upper end 27 of the appliance 10. Thus, the refractory bricks 22, 24 constitute a rear wall of the secondary combustion chamber and the refractory bricks 23, 25 constitute a front wall of the secondary combustion chamber. Any one or more ox th© refractory bricks 22 to 25 may be substituted for a waterway if the , appliance 10 is to heat water, as is known in the art. i As shown, the secondary combustion chamber 21 is in effect an expansion chamber which in cross-section is formed in the general shape of a symmetrical parallelogram. The entry throat 20 and discharge outlet 26 are generally disposed on a notional line 30 the angle 2 of which relative to the vertical is approximately between 1OU and SO .

The ratio of the width X of the entry throat to the greatest width Y of the chamber 21 is in the range 1:4 to 1:8, and preferably approximately 1:6.

The discharge outlet 26 of the secondary combustion chamber 21 and a discharge outlet 31 of the first combustion chamber 13 communicate with a chimney flue 32.

A damper plate 40 is pivotally mounted on a metal plate 41 fixed to the upper part 42 of the refractory brick 25. As shown, the discharge outlet 26 of the secondary combustion chamber 21 is defined between the damper plate 40 and the rear wall 43 of the flue 32. A forwardly projecting cyclindrical arm 44 is fixed to the . •damper plate 40 by means of a nut 45 which is threaded onto the end 46 of arm 44 which projects through an aperture (not shown) in the damper plate 40.

P The. other end 47 of the ana 44 is engaged in an aperture (not shown) in a flange member 48 which -is fixed to and projects at right angles to an operating lever 49. The operating lever 49 is pivotally mounted on the upright f* ,me 11 of the appliance by means of stud 50. A part 51 of the operating lever 49 projects forwardly and externally of the appliance 10 so that a user can safely operate th® damper 40. The part 51 may be of a non-heat conducting, or heat insulating material.

The aperture in the flange 48 which accommodates the end 47 of the arm 44, is of a greater diameter than the et® 44 so that the operating lever 49 can b® manually moved upwards and downwards to vary the position of the damper 40. The position of th® damper 40 with the operating lever 49 in its upper position is shown in dotted outline in Figure 2» In operation, a fuel bed is built on the grate 12 and combustion commenced. Th® volatiles which are produced from th® combustion in th© fuel bed, pass through the entry throat 20 and are drawn into the secondary combustion chamber 21» Further, air is drawn into the appliance from the front 60 and can also pass into th® chamber 21 via the entry throat 20. Xn addition, secondary heated air say be drawn into the chamber 21 through suitably located apertures SI in the plates 15 and 18 which may communicate with apertures 62 In the frame 11.

As the chamber 21 is of a greater volume than that of the entry throat 20, the hot air and volatiles entering the chamber 21 undergo a decrease in velocity which allows‘turbulence and mixing within the chamber 21. Of particular importance, th® gases entering the chamber 2i, can expand on either side of the notional line 30 extending between the entry throat 20 and outlet 26. This all round expansion ensures a substantial reduction in gas velocity and enhances the combustion of the gases. In particular, the .ratio of -the width of the entry throat X to the greatest width ¥ of the chamber when within the ratio 1:4 to 1:8, but more preferably approximately 1:6, results in optimal combustion of the gases and thus reduction of smoke emission front th.® appliance. i Further, the damper 40, when in the vertical position shown in Figures 1 and 2, reduces the sire of the outlet 26 to a minimum to also Increase th® residence time of the gases in th® chamber 21» The parallelogram shape of the chamber 21 has also been found to optiai.se the combustion of gases and reduce smoke emission from th® appliance» As explained above the firebricks 22 to 25 may be substituted for waterways so that water is heated in the appliance 10.

In Figure 3 another embodiment of the invention is illustrated, and it will be understood that this embodiment is identical with that described in relation to Figures 1 and 2 except in relation to the modification now fo be described. As shown in Figure 3, the damper plate 40 is pivotally mounted on a support plate 70 which is fixed fo the plate 41 at the top 42 of the refractory brick 25. The support plate 70 has a series of apertures 71. In use, th® influence of the chimney flue 32 on the combustion chamber 21 is substantially reduced, because air will be drawn into the chimney flue 32 through the apertures 71, and thus the velocity of the gases in the chamber 21 will he further reduced, resulting in enhanced combustion and reduced smoke emission. Th® lower the velocity of gases in the chamber 21 the greater will be the tire for combustion of -the gases, and thus the reduction in smoke emission. When desired the apertures 71 may be closed by slidable plate (not shown).

• Witts reference now to Figure 4 of the Drawings, there is shown a second embodiment of a combustion appliance generally indicated at 10a according to the invention.* The combustion appliance 10a is similar to the appliance 10 previously described. However, for reasons of clarity, the bricks 23, 25 are not shown. Further, th© bricks 22, 24 have been replaced by a metal plate 90 which, together with the bricks 23, 25 (not shown) form the combustion chamber 21. The appliance 10a may be fitted within a chamber defined at the sides and back by suitable incombustible or heat resistant material 91. The appliance 10a together with sides and back 'of the chamber form a convection chamber 92. In this particular embodiment, the material 91 constitutes a pre-existing fireback such as may be used with a conventional open fire. The chamber 92 is closed at th© top by a sealing plate 93 thereby providing an air gap or clearance above the appliance 10a. Th© sealing plate 93 lies above or within the chamber 92 and at the base of the chimney 94» A flue or smoke pipe 95 passe© through the sealing plate 93 which pipe 95 carries combustion products from the appliance 10a to the chimney 94A duct 96 in communication with the chamber 92 Xs provided which duct opens at the front of the appliance or above the appliance via a grill or louvre 97. At the base of the appliance is provided a duct 98 which is in communication with the chamber 92 and which is open at the front of the appliance at the opening 98a.

Accordingly, when the appliance 10a is in operation, the heat from the plate 90 and the appliance 10a in general will heat the air in the chamber 92. A convection current will thus be set up resulting ih relatively cool air being drawn into the chamber 92 via the opening 98a and heated air exiting through the louvre 97» If desired, sir fro® the convection chamber 92 may be admitted, to the combustion chamber 21. A transfer chamber 99 is provided integral with the metal plate 90.

The plate 90 has an opening 100 in communication with . the transfer chamber 99 and the transfer chamber has an .(. opening 101 in communication with the convection chamber 92. It is important that the opening 100 be disposed at a level above that of the opening 101 to ensure that there is no contamination ox the air in th© convection chamber 92 by gases passing from the combustion chamber 21 into the chamber 92.

The appliance 10 or 10a may he provided in the form of a frss standing stov® (not shown). In the case of th© appliance IQa, the convection chamber 92 and related components as described above are provided as an integral part of the stove.

Claims (12)

CLAIMS:

1. A combustion appliance comprising a grate for . supporting & firebed in a first combustion chamber, en ash receiving area defined beneath tbe grate, a second combustion chamber disposed behind said first combustion chamber, th© secondary combustion chamber communicating with a flue via a discharge outlet,, the first combustion chamber communicating with the secondary combustion chamber via an entry throat disposed at the bottom ox said first and second combustion chambers, said secondary combustion chamber arranged in the form of a parallelogram which diverges upwardly from th© entry throat to the greatest width of tbe secondary combustion chamber and converges upwardly from the greatest width of the secondary combustion chamber towards th© discharge outlet.

2. A combustion appliance as claimed in Claim 1, wherein there is provided means for introducing preheated air into the secondary combustion chamber.

3. - A combustion appliance as claimed in Claim 1 or 2, wherein the ratio of the width of the entry throat to greatest width of the secondary combustion chamber is approximately 1:4 to 1:8.

4. A combustion appliance as claimed in Claim 3, wherein the ratio of the width of the entry throat to the greatest width of th© secondary combustion chamber is approximately 1:6.

5. A combustion appliance as claimed in any preceding claim, wherein th© entry throat and the discharge outlet ere disposed on a notional line having a forward inclination of approximately between 10° ©nd 50° relative to vertical.

6. A combustion appliance as claimed in any preceding Claim, wherein a convection chamber Is disposed behind said secondary combustion chamber, and the rear wall of the secondary combustion chamber comprises heat conductive material, the convection chamber 4 communicating with the exterior of th® appliance for providing heated air to th© external environment

7. A combustion appliance as claimed in. Claim 6, wherein a duct communicating with the convection, chamber is provided at the base of the appliance for supplying air to the convection chamber.

8. A combustion appliance as claimed in Claim 6 or 7, wherein a transfer chamber is provided on the rear surface of the rear wall of the secondary combustion chamber, the transfer chamber having first opening in communication with the convection chamber, and a second opening disposed above the first opening In communication with the secondary combustion chamber.

9. A combustion appliance as claimed in any preceding claim, wherein a damper plat® is pivotally mounted at the.upper end of the secondary combustion chamber.

10. A combustion chamber as claimed in Claim 9 wherein the damper plate is pivotally mounted on a support plate, the support plate having a plurality of closable apertures.

11. A combustion appliance as claimed in Claim 9 or 10, wherein the damper plate is connected to an operating lever which projects externally of the appliance. v • *

12. » A combustion appliance substantially as described herein with reference to and as illustrated in Figures 1, 2, 3 or 4. '