Patent GB-670757-A (GB)
Title: Improvements in or relating to heating devices of the internal combustion type
IPC: B60P3/22
Filed: 1949-09-29
Abstract: 670,757. Vapour burners; igniting burners. PLESSET, E. H. Sept. 29, 1949 [Sept. 30, 1948]. No. 25071/49. Classes 75(i) and 75(iii) [Also in Group XIII] An internal combustion heater comprises a sealed combustion chamber supplied with air under pressure and containing a vapour burner disposed near the air inlet, an electric heating element for vaporizing fuel collected in a pan beneath the burner on initiating the fuel supply to the latter, and means for shielding the vaporized fuel from the air flow while permitting a sufficient air supply to form a combustible mixture for ignition by the electric heating element or by an independent igniter. In an internal combustion heater for use in aircraft the air to be heated is passed over the wall of a combustion chamber 12, Fig. 2, mounted in a duct 10, and provided with external longitudinal heat transfer fins 13, and is discharged through a register 11a. The combustion chamber 12 contains a vapour burner 23, supported by a liquid fuel supply pipe 24, and having internal baffles 27 for diverting the fuel against its walls at least one portion of which is permeable to liquid fuel and consists of porous material, e.g. porous metal, or of a reticulated metal plate or screen. At start the liquid fuel drips from the burner 23 on to a tray 46, Fig. 6, having a fuel-collecting well 39 through which passes a plug 33 mounting an electric heating coil 29. The lower end of the latter vaporizes the fuel which is then ignited at the upper end which may be adapted to provide a higher temperature. A perforated cylindrical guard 48 surrounds the ignition coil 29 and directs a flame upwardly to ignite the fuel issuing from the burner 23. Air for combustion is supplied by a blower 17, through a pipe 19, in which it is preheated when the burner is in operation by the hot air in the duct 10, and passes into a plenum chamber 16 and from thence through an aperture 21 in the combustion chamber wall 14 provided with a baffle 22. One or more additional air openings 49 may be provided. To assist in maintaining a flame the burner 23 may be formed of ceramic material so as to be heated to a high temperature during the burner operation, or if the burner 23 is of metal a button or ring 51 of ceramic material may be mounted thereon; and in addition the tray 46 may contain a T- shaped member 52 of a material of low specific heat and thermal conductivity. In a modified construction the burner 23 is provided with a downwardly tapered extension having a small aperture for discharging fuel on to the electric heating' element during the igniting operation. In this modification the heating coil vaporizes the fuel but does not attain the ignition temperature, and a small electric igniting coil is mounted beside the vaporizing coil beneath a hood extending over the tray 46. An alternative vapour burner 68, Fig. 11, is provided with an electric heating element 72 held between grooved plates 69, 71 of a material of low specific heat and thermal conductivity so that they are heated by the element 72 to a temperature sufficient to vaporize the fuel. The said temperature may be sufficient to ignite the fuel or a separate igniter element may be provided.