GB2197454A

GB2197454A - Heating device

Info

Publication number: GB2197454A
Application number: GB08724551A
Authority: GB
Inventors: Peter John Woolcott
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1986-11-15
Filing date: 1987-10-20
Publication date: 1988-05-18
Anticipated expiration: 2007-10-20
Also published as: FR2606834A1; GB2197454B; JPS63134848A; GB8627383D0; GB8724551D0; IT8722637A0; ES2005689A6; US4849604A; IT1223125B; DE3736742A1

Description

1 GB2197454A 1

SPECIFICATION

Heating device f. 15 This invention relates to a heating device for mounting on an air inlet manifold of a compression ignition engine and of the kind in which liquid fuel is heated and vaporized to form an air/fuel mixture which is ignited to provide a flame which heats the air flowing to the engine.

The object of the present invention is to provide a heating device of the kind specified in a simple and convenient form.

According to the invention a device for the purpose specified comprises a thin walled tubular element, one end of said element being closed and the other end of the element being connected in use to a source of liquid fuel, an aperture formed in the wall of the element adjacent said one end thereof, an electric heating element wound about the tubular element, said element in use acting to heat the tubular element so that the fuel therein is va- porized, the vaporized fuel passing through said aperture and forming an air/fuel mixture, an ignition element for igniting said mixture and a plug located within the portion of the tubular element said plug being shaped to al- low fuel flow to said aperture and to direct the fuel against the inner surface of the wall of the tubular element.

The accompanying drawing is a sectional side elevation of the heating device and it will be seen to comprise a hollow body 10 which 100 in the example is formed from metal, the body having a hexagonal portion and an annular portion 12 the periphery of which is provided with a screw thread for engagement in use in a mounting on the engine inlet manifold. Also 105 provided is a tubular element 13 which is of stepped cylindrical form and which is formed from stainless steel. The element is retained relative to the body by an electrically insulat ing and heat resisting moulding 14 which is moulded about the intermediate portion of the element. The moulding is shaped to locate against a step defined in the body and is re tained therein by rolling over a thin section portion 15 of the body. A heat shield 14A is 115 located against the end face of the moulding which is within the body, the heat shield be ing formed from metal or from some suitable ceramic material.

The moulding 14 is formed with elongated openings through which extend a pair of con ductive members 16, 17 which extend within the space defined between the inner portion of the:element and the body. The conductive members are integrally formed with washers 18, 19 and terminal members 20 21 respec tively. The washers are incorporld into a moulded terminal assembly 23 which main tains the washers in spaced insulating relation ship and which is provided with a central 130 aperture which can locate about an unthreaded portion of the element 13. The terminal assembly is retained in position by means of a screw threaded nut 25 which is engaged with a threaded portion of the element, a metallic washer being positoned between the nut and the terminal assembly.

The threaded end of the tubular element forms a fuel inlet 26 for connection in use to a source of fuel under pressure and the opposite end portion 28 of the tubular element projects beyond the end of the body 10 and is of reduced diameter and also has a wall thickness of approximately 0.254mm. More- over, the end of the element is closed and at least one aperture 27 is formed adjacent the closed end of the element. In the example two apertures are provided having a diameter of 1.Omm.

The outer surface of the portion 28 of the element is coated with an electrically insulating frit and wrapped tightly around the outer surface is a heating element 30 formed from wire. One end of the element is secured, as by welding, to the conductive member 16 and the other end of the element is secured to an intermediate conductive member 29 which is supported by the moulding 14 being a force fit therein. Conveniently the material forming the wire is NICHROME.

The conductive member 29 is also connected to one end of a single turn ignition -element 31 which is formed from the same section wire as the heating element. The -other end of the ignition element is connected to the conductive member 17. The ignition element is spaced outwardly from the heating element and is located about halfway between the apertures 27 and the shield 14A. - Within the end portion 28 of the element 13 there is located a plug 32 which conveniently is formed from ceramic material and which is so constructed as to permit fuel to flow to the aperture or apertures 27. The plug may be fluted and its ends chamfered. Also located in the bore in the element 13 is a porous plug or plugs 33. The plugs are located in end to end relationship and the purpose of the plugs is to filter the fuel flowing through the inlet 26 on its way to the apertures 27 and also to control the flow of fuel. The plug or plugs are formed from sintered bronze material a convenient material being manufactured by Sound Brook Green Limited and sold under the designation F366-100B LUSROOK.

The heating device is also provided with a tubular thin walled shroud 34 which is secured to the end of the annular portion 12 of the body as by welding and adjacent the end of the body the shroud is provided with a plurality of openings 35 through which, in use, air can enter into the annular space between the element and the shroud. The shroud extends beyond the closed end of the element 13.

2 GB2197454A 2 In use when the terminal members 20, 21 are connected to a source of electric supply, the heating element will rapidly heat the thin walled end portion 28 of the element 13 and fuel supplied through the inlet 26 will be vaporized during its passage to the apertures 27. The fuel vapour emerging from the apertures 27 is mixed with air flowing through the openings 35 and the resultant mixture is ig- nited by the ignition element 31. A flame is therefore produced which heats the air flowing in the inlet manifold.

It will be noted that the ignition element 31 is spaced from the openings 27. The purpose of this is to protect the ignition element from the intense heat produced when the fuel is burnt. It has been found that ignition of the air/fuel mixture can be attained in a satisfactory manner with the ignition element posi- tioned as shown. The plug or plugs 33 control the rate of fuel flow through the device in an extremely convenient manner and also act to retain any particles of dirt which might otherwise tend to block the apertures 27. The thin walled section of the end portion 28 of the element 13 ensures that a flame is achieved very quickly after switching on the electric supply and supplying fuel through the inlet 26.

Claims

1. A heating device for mounting on an air inlet manifold of a compression ignition engine comprising a thin walled tubular element, one end of said element being closed and the other end of the element being connected in use to a source of liquid fuel, an aperture formed in the wall of the element adjacent said one end thereof, an electric heating ele- ment wound about the tubular element, said element in use acting to heat the tubular element so that the fuel therein is vaporized, the vaporized fuel passing through said aperture and forming an air/fuel mixture, an ignition element for igniting said mixture and a plug located within the portion of the tubular element said plug being shaped to allow fuel flow to said aperture and to direct the fuel against the inner surface of the wall of the tubular element.

2. A device according to Claim 1 including a hollow body, means mounting the tubular element within the body, the body defining an annular portion extending about the tubular element, a hollow shroud secured to the annular portion of the body and extending beyond said one end of the tubular element, openings formed in said shroud and through which air can flow to form the air/fuel mixture, said ignition element being removed from said aperture in the direction away from said one end of the tubular element.

3. A device according to Claim 2 including a further plug located in said tubular element, said further plug being porous so as to act as a filter and to control the rate of fuel flow through the tubular element.

4. A device according to Claim 3 in which said first mentioned plug is formed from cera- mic material and said further plug is formed from sintered metal.

5. A device according to Claim 3 in which said means comprises a heat resisting moulding which is moulded about an intermediate portion of the tubular element and is retained against a step in the body by rolling a thin section of the body.

6. A device according to Claim 6 including a heat shield disposed against the end face of the moulding facing towards said one end of the tubular element.

7. A device according to Claim 3 in which the tubular element is formed from metal and is coated with an electricaliy insulating frit over at least that portion about which the heating element is wound, the heating element being formed from round section wire.

8. A device according to Claim 1 in which the tubular element is formed from stainless steel and the wall thickness of that portion of the element which is surrounded by the heating element is approximately 0.254mm, the diameter of said aperture being 1.0mm.

9. A heating device for mounting on an air inlet manifold of a compression ignition engine comprising the combination and arrangement of parts substantially as hereinbefore described with reference to the accompanying drawing.

Published 1988 at The Patent Office, State House, 66/71 High Holborn, London WC 1 R 4TP. Further copies may be obtained from The Patent Office, Sales Branch, St Mary Cray, Orpington, Kent BR5 3RD. Printed by Burgess & Son (Abingdon) Ltd. Con. 1/87.

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