Heating device for air inlet manifolds

A heating device for mounting on an air inlet manifold of a compression ignition engine to heat the air flowing to the engine comprises a thin walled tubular element closed at one end and having a fuel inlet at the other end. A ceramic plug is located in the element to direct fuel flow against the interior surface of the element. A heating element is wound about the tubular element to heat and vaporize the fuel which flows out through an opening adjacent the one end. The fuel vapor forms an air/fuel mixture which is ignited by an ignition element.

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 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.

The accompanying drawing is a sectional side elevation of the heating 
device and it will be seen to comprise a hollow body 10 which in the 
example is formed from metal, the body having a hexagonal portion 11 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 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 insulating 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 
retained therein by rolling over a thin section portion 15 of the body. A 
heat shield 14A is located against the end face of the moulding which is 
within the body, the heat shield being formed from metal or from some 
suitable ceramic material. 
The moulding 14 is formed with elongated openings through which extend a 
pair of conductive members 16, 17 which extend within the space defined 
between the inner portion of the element 13 and the body 10. The 
conductive members are integrally formed with washers 18, 19 and terminal 
members 20, 21 respectively. The washers are incorporated into a moulded 
terminal assembly 23 which maintains the washers in spaced insulating 
relationship and which is provided with a central aperture which can 
locate about an unthreaded portion of the element 13. The terminal 
assembly is retained in position by means of a bolt threaded nut 25 which 
is engaged with a threaded portion of the element 13, a metallic washer 24 
being positioned 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 
0.254 mm. Moreover, 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 1.0 mm. 
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 Bound Brook 
Green Limited and sold under the designation F366-100B LUBROOK. 
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. 
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 ignited 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 positioned 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.