US2346506A - Fuel heating apparatus - Google Patents

Description

April 11, 1944. J. D. PULLIAM 2,346,506

FUEL HEATING APPARATUS Filed Feb. 1, 1943 James ZLRuZZc'am, a? ,4 W

Patented Apr. 11, 1944 FUEL HEATING APPARATUS .iames D. Pulliam, San Antonio, Tex., assignor of five per cent to Donald R. Parker; five per cent to R. W. Barnes; ten per cent to Augustus McCloskey and A. T. Stevens (jointly), and forty per cent to N. A. Saigh Application February 1, 1943, Serial No. 474,355

*7 Claims.

to the injector nozzles associated with the engine cylinder, to heat the fuel in the lines to a temperature below the vaporization point of the fuel at the pressure maintained therein, to the end that highly heated liquid fuel is sprayed under high pressure into the highly compressed air in the engine cylinders, thereby greatly facilitating the ignition of the fuel under the heat and pressure generated in the cylinders. The invention is predicated upon the discovery that starting of a Diesel engine, particularly when the engine is cold, may be greatly facilitated by preheating the fuel before its injection into the engine cylinders,

It is well understood by persons familiar with Diesel engines that the fuel is ignited when it is injected in the form of a fine spray into the highly compressed air in the cylinder, because the air has been heated to the ignition point of the oil, as a result of its high compression by the engine piston. Theoretically, the compression of the air in the cylinders should raise its temperature well above the flash point of the fuel, but in practice, particularly when the weather is cold and the cylinder walls, pistons and the fuel are cold, this temperature is not immediately reached and difficulty in starting is often encountered. Of course, after the engine has been running for a short time, the parts become sufficiently heated to maintain efiicient operation.

The present invention is predicated upon the discovery that the starting of a cold engine under the above circumstances may be effected substantially instantaneously by raising the temerature of the fuel in the fuel lines leading to the injectors, so that highly heated liquid fuel is injected into the compressed air in the cylinders, since the heat of that although some times insufiicient to ignite cold fuel oil, is entirely adequate to ignite the heated oil.

The present invention provides novel means for heating the oil in the fuel lines prior to its injection into the engine cylinders. The invention must be distinguished from attempts heretofore made to facilitate vaporization of liquid fuel by heating the fuel, prior to the mixing of the fuel vapors with air, for instance, in a carburetor or other device for mixing gaseous fuel and air prior to its introduction into the engine cylinders, since the fuel in accordance with the present invention is not vaporized in the line, but, on the contrary, is injected in the form of a highly heated liquid spray into the cylinder. In other words, the fuel, under the pressure maintained in the fuel line between the pump and the injector, remains in liquid form, as distinguished from gaseous form. Hence, a primary object of the present invention is to provide, in combination with a Diesel engine, means for facilitating starting of the engine, particularly when cold, by raising the temperature of the liquid fuel, substantially to the flash point, before it is injected under high pressure into the compressed air in the cylinders of the engine.

Another object of the invention is to heat the fuel in the fuel lines between the fuel pump and the injector nozzles or assemblies, so that compression ignition of the injected fuel is greatly facilitated, particularly when the engine is cold.

A further object of the invention is to heat the fuel in the fuel lines to a temperature below the vaporization temperature of the fuel at the pressure maintained in the lines between the pump and the injectors to the end that the ignition of the liquid fuel injected into the air in the cylinders, heated by the compression thereof, is positively assured,

A further object of the invention is to provide a device of this character which may be employed for starting and which may readily be rendered inoperative when the engine has become warmed up, by operation for a short time.

A further object of the invention is to provide a device adapted to perform these fuctions which is characterized-by extreme simplicity, low cost of manufacture, substantial absence of critical materials and ease of attachment to existing engines or to newly produced engines.

Another object is to provide a heating device of this character having novel details of construction, adapted to conserve heat, to prevent external radiation and loss of heat and to concentrate the heat upon the fuel pipe and the fuel therein, preferably immediately ahead of the injector assembly.

Other and further objects and advantages of the invention will be apparent to those skilled in the art, from a consideration of the following description of a specific embodiment of th invention, described below and shown in the accompanying drawing, in which:

Figure l is a somewhat diagrammatic side elevation of a Diesel engine showing the devices of the present invention attached to the fuel lines thereof.

Figure 2 is a longitudinal section and partial elevation of one of the heating units, and

Figure 3 is a cross-section of the device shown in Figure 2.

A Diesel engine of conventional design is represented at in Figure 1. A fuel pump ll, driven by the cam shaft or any suitable means, i provided with four outlets l2, l3, l4 and I5, delivering fuel under pressure through lines l6, I1, I8 and I9 to injector assemblies 26, 2|, 22 and 23, respectively, associated with the four cylinders of the engine. Since the details of the fuel pump, the injector assemblies and the means for timing the injection of fuel into the cylinders form no part of the present invention, they will not be described herein.

The fuel lines I 6-! 9 are provided, in accordance with the invention, with heating devices 2 3, 25, 26 and 2?, respectively, each of which is preferably positioned immediately ahead of the associated injector assembly.

Since all of the heating units are of substantially the same construction, only one need be described in detail. Referring to Figure 2, the fuel line IS, in accordance with conventional design, comprises a copper or copper alloy pipe leading to a coupling 30 associated with the injector head 20. A layer 3| of mica or equivalent material is wrapped around the pipe l6 for a suitable length, thereby providing an electrically insulating, heat resisting layer of good heat conductin material. An electrical resistance element in the form of a metallic ribbon 32 is wrapped in a spiral coil around the mica layer 3|, with one of its ends 33 secured, as by a weld 34, in electrical contact with the pipe l6 and with its other end 35 projecting outwardly and provided with a terminal connection 36.

A second layer 31 of mica or equivalent material is wrapped around the resistance element, to maintain the convolutions thereof in predetermined position and to insulate the ribbon from the outside.

Finally, a body 38 of heat insulating material covers the entire assembly, with the exception of the terminal connection 36. This body is preferably formed of an asbestos cement composition and is moulded about the mica layers and the resistance element, to seal them from external atmosphere. Preferably, the heat insulating body 38 is sealed at its ends to the pipe I 6. Hence, substantially all of the heat generated b the resistance element is concentrated and is directed inwardly, to raise the temperature of the pipe l6 and the fuel maintained under pressure therein.

As indicated in Figure 1, the several heating units may be energized by a battery 4i! having one lead 4! grounded to the engine at 42 and the other lead 43 connected, through a circuit breaker 44, to branch lines 45, 45, 4'1, and 48, leading, respectively, to the terminals 36. of the resistance element 32. The current flows from the, battery 40 through line 43, switch 44,. branch lines 45-48 and resistance elements 32 and re.- turns through the welded connections 34, fuel pipes 16-49, connection 42 and wire 4|. The invention contemplates the us of a thermostat controlled switch, in addition to or as a substitute for the manually operated switch 44, so that the circuit will be automatically opened and the heating elements deenergized. after the engine has been operating for a suificient time to raise its temperature to a predetermined degree. In such case, the heating elements may be initially energized by manual operation of a suitable switch and automatically deenergized b a thermostat controlled device.

It is thought that the operation of the apparatus of the present invention will be apparent from the foregoing description. When it is desired to start a cold engine equipped with the devices described above, it is simply necessary to complete the circuit to the several heating elements, so that the fuel in the lines leading to the injector assemblies is rapidly heated. The engine may then be turned over by the usual means, whereupon it will start immediately, as a result of the injection of the hot fuel under high pressure into the air in the cylinder, which has been heated as a result of its compression by the engine piston. After the engine has operated for a short time, the parts will become suiiiciently heated to maintain normal operation of the engine, whereupon the heating devices may be electrically disconnected.

Although the invjention has been described with considerable particularity in this specification, it must be understood that it is not limited to the details of construction described above and shown in the accompanying drawing, but includes all modifications coming within the scope of the appended claims and their equivalents.

I claim:

1. The combination with an engine of the Diesel type having a fuel injector associated with its cylinder, a fuel pump and a pipe for delivering fuel under pressure from the pump to the injector, of means for heating the fuel in said pipe, for starting purposes, to an elevated temperature below the point of vaporization of the fuel at the pressure maintained in the pipe, said means comprising an electric resistance element positioned exteriorly of the pipe in heat exchange relation thereto, and means for conducting current therethrough, to heat the element, the pipe and the fuel therein.

2. The combination with an engine of the Diesel type having a fuel injector associated with its cylinder, a fuel pump and a pipe for delivering fuel under pressure from the pump to the injector, of means positioned adjacent the injector for heating the fuel in said pipe, for starting purposes, to an elevated temperature below the point of vaporization of the fuel at the pressure maintained in the pipe, said means comprising an elongated electric resistance element wound around the pipe in heat exchange relation thereto and electrically insulated therefrom except at one end, said end being connected to the pipe, and means for conducting current through the element and for return through the pipe, to heat the element, the pipe and the fuel therein.

3. The combination with an engine of the Diesel type having a fuel injector associated with its cylinder, a fuel pump and a pipe for delivering fuel under pressure from the pump to the injector, of means positioned adjacent the injector for heating the fuel in said. pipe, for starting purposes, to an elevated temperature below the point of vaporization of the fuel at the pressure maintained in the pipe, said means comprising a layer of heat conducting and electrically insulating sheet material covering a portion of the pipe, an electric resistance element disposed exteriorly of said layer, a covering of heat insulating material surrounding the resistance element, and means for conducting current through the element, whereby the heat generated thereby is transmitted through the first-mentioned layer to the pipe and the fuel therein.

4. The combination with an engine of the Diesel type having a fuel injector associated with its cylinder, a fuel pump and a pipe for delivering fuel under pressure from the pump to the injector, of means positioned adjacent the injector for heating the fuel in said pipe, for starting purposes, to an elevated temperature below the point of vaporization of the fuel at the pressure maintained in the pipe, said means comprising a layer of heat conducting and electrically insulating material surrounding a portion of the pipe, an electric resistance element wrapped spirally around the layer and connected at one end to the pipe, a covering of dielectric heat insulating material surrounding the resistance element and in contact therewith, and means for conducting current through the resistance element for return through the pipe, thereby to heat the element, the pipe and the fuel therein.

5. A heater for the fuel line of a Diesel engine, positioned between the fuel pump and the fuel injector and adjacent the injector to heat the fuel in the line to facilitate starting, said heater comprising a layer of dielectric material of good heat transmitting character surrounding the line ahead of and adjacent the injector assembly, an electric resistance element disposed in heat exchange relation upon the layer, a body of dielectric heat insulating material covering the element and the first-mentioned layer and substantially sealed at its ends to the line, whereby the heat from the resistance element is directed inwardly to raise the temperature of the line and the fuel therein, and an electrical connection disposed exteriorly of said body and leading to said element.

6. A heater for the fuel line of a Diesel engine, positioned between the fuel pump and the fuel injector, to heat the fuel in the line to facilitate starting, said heater comprising a layer of resistant, heat transmitting, electrically insulating sheet material surrounding the line directly ahead of the injector assembly, an electric resistance element coiled about the layer in heat exchange relation thereto and having one of its ends connected to the line and its other end projecting outwardly therefrom, another layer of resistant electrically insulating material covering the resistance element, and a body of heat insulating material covering the last-mentioned layer, but exposing the outwardly projecting end of the resistance element for connection to a source of current, said body serving to direct the heat from the resistance element inwardly to raise the temperature of the line and the fuel therein.

7. A heater for the fuel line of a Diesel engine, positioned between the fuel pump and the fuel injector, to heat the fuel in the line to facilitate starting, said heater comprising a layer of mica surrounding the line ahead of the injector assembly, an electric resistance element coiled about the layer in heat exchange relation thereto and having one of its ends connected to the line and its other end projecting outwardly therefrom, another layer of mica covering the resistance element, and a body of asbestos-cement composition covering the last-mentioned layer and sealed at its ends to the outer surface of said line, but exposing the outwardly projecting end of the resistance element for connection to a source of current, said body serving to direct the heat from the resistance element inwardly to raise the temperature of the line and the fuel therein.

JAMES D. PULLIAM.

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