US2635423A

US2635423A - Igniter for internal-combustion engines

Info

Publication number: US2635423A
Application number: US181836A
Authority: US
Inventors: Edward J Oakes; Ralph K Rothrock
Original assignee: Individual
Current assignee: Individual
Priority date: 1950-08-28
Filing date: 1950-08-28
Publication date: 1953-04-21
Anticipated expiration: 1970-04-21

Description

April 21, 1953 E. J. OAKES ET AL 2,635,423

IGNITER FOR INTERNAL-COMBUSTION ENGINES F iled Aug. 28, 1950 INVENTORE EZZWQWJJO%$ Patented Apr. 21, 1953 OFFICE IGNITER FOR INTERNAL-COMBUSTION ENGINES Edward J. Oakcs and Ralph K. Rothrock, New Oricans, La.

Application August 28, 1950, Serial No. 181,836

10 Claims.

The present invention relates to igniters for in= ternal combustion. engines, and more especially those of the gas turbine type employing an air compressor which supplies air for combustion to a combustion chamber or a set of combustion chambers in which fuel is burned and the burned or combusted gases are utilized to drive a turbine or to otherwise develop useful power.

A primary object of the invention is to provide an igniter for internal combustion engines which is capable of igniting efficiently and with certainty the combustible fuel supplied to such an engine.

A more particular object is to provide an igniter for internal combustion engines of the gas turbine type for eiiiciently igniting the combustible mixture of fuel and air in the combustion chamber or chambers thereof. A further object of the invention is to provide an igniter for the gas turbine of an airplane, and especially those of the jet propelled type, which will provide efficient and reliable combustion of fuel supplied thereto at very high altitudes and very low temperatures.

The preferred embodiments of the invention are shown in the accompanying drawing, wherein- Figure 1 is a side elevation, partly in section, of a gas turbine power plant for an airplane provided with fuel igniters according to the present invention. 7

Figure 2 is a detail sectional view, on an enlarged scale, of an igniter embodying the present invention.

Figure 3 is a detail view of an igniter provided with means for supplying a combustible gas and air thereto.

Figure 4 is a detail view, partly in section, showing another form of igniter embodying the present invention, having means for supplying a combustible gas and air thereto.

Figure 5 is a diagrammatic view showing the form of the are produced by the igniter.

In the present instance in which the invention is shown applied to a gas turbine power plant for propulsion of an airplane, ill represents the casing of the plant within which are mounted the rotor l I of an axial flow compressor having rotor blades 12 mounted on its periphery to cooperate with stator blades i3 fixed on the casing, the rotor and stator blades having appropriate pitch to provide a multistage air compressor of the axial flow type, and [4 represents the rotor of a gas turbine which is connected to the rotor l I of the compressor by a coupling 15 whereby the compressor will bedriven by the turbine, the compressor and turbine rotors being mounted rotatably and in alinement in the casing b bearings Hi. The turbine rotor carries rows of blades I? which cooperate with stator blades Is in the casing, these rows of blades of the turbine having appropriate pitch to provide a multistage turbine which is driven by the burned or combusted gases from the combustion chamber or chambers. The compressorturbine unit may be connected through appropriate reduction gearing l9 to a propeller 20 for propelling the airplane, and the turbine may discharge the spent products of combustion through an annular passage 2| for jet propulsion of the airplane. Compressed air from the compressor is received in an annular duct 22 which communicates with a combustion chamber 23 which may be of annular form and extending around the axis of the unit or may comprise a set of separate combustion chambers spaced around the circumference of the unit, the combustion chamber or chambers being supplied with fuel, such a kerosine or similar liquid hydrocarbon, from a header or manifold 24 connected to a suitable source of supply, and by jet nozzles 25 connected thereto and extending into the combustion chamber or chambers, and which spray the fuel into the body of compressed air from the compressor. The gas turbine unit as shown and described is of a well known type, and its mode of operation is well known to those skilled in the art.

The present invention provides an ignlter for igniting the mixture of air flowing from the compressor and the atomized fuel sprayed into the combustion chamber or chambers from the jet nozzle or nozzles which will produce efficient ignition of the mixture, and which will withstand the high temperature of the gases burning in the combustion chamber or chambers. The improved ignited, in its preferred form, comprises a tubular outer member 38 having a pipe or other suitable connection 3| for the supply of compressed air thereto, and a central electrode 32 which is secured in a porcelain or other suitable ceramic high tension insulator 33 which has a collar thereon which is clamped against an annular shoulder 34 in the member 30 by a sleeve 35 threaded into the end of said member. The tubular member which forms one electrode, and the central electrode, are composed of metal, the central electrode being preferably composed of a non-mag netic material such as bronze and having a terminal 36 for connection thereto of a source of electric current of a potential and current strength such as that hereinafter described, and the tubular member is threaded at one end 3'! for insertion through the Wall of the casing into the combustion chamber for completing the circult for the ignition current which may be grounded on the casing. The air supply pipe 3! of each igniter is connected to a header 3S, and the latter is connected by a pipe 4| to receive compressed air from a booster pump 39 which may be driven by suitable gearing 40 from the propeller reduction gearing i9, and is connected by a pipe 42 to receive compressed air from the duct 22, which may be at a pressure of about pounds per square inch, and increases the air pressure to about 52 pounds per square inch in order that the air thus supplied to the tubular member 33 of each igniter may overcome the pressure in the combustion chamber, and to flow into the combustion chamber at the downstream side of the respective fuel jet nozzle in the path of the spray of fuel therefrom. Compressed air is thus supplied at a suitable pressure to each igniter from the header 38 which is supplied from the booster pump 39.

In operating a gas turbine power plant equipped with igniters embodying the present invention, the outer tubular electrode 30 and central electrode 32 of each igniter are connected to the respective terminals of the secondary of a transformer T which is capable of providing an electric current of a sufliciently high Voltage and amperage to develop and sustain a high tension high temperature are between the inner ends of the outer and

inner electrodes

30 and 32 and blown beyond the inner ends of these electrodes by a current of air flowing through the igniter from the supply pipe 3|, the velocity of which air flow may be adjusted by a valve 3la which may be provided in this pipe, so that the arc formed between the outer and inner electrodes is elongated into a loop and i flame-like in form, and extends into the fuel sprayed into the combustion chamber from the respective jet nozzle, causing instantaneous ignition of the atomized fuel.

It has been found that in operating an igniter of this type with a gap of about one-half inch between the central and outer electrodes and these electrodes supplied with current at about 20,000 volts and 100 milliamperes, by adjusting the air current through the outer tubular electrode, an are A may be blown in the form of a loop beyond the electrodes to an extent of from 1 to 4 inches and that blue electrical discharges appear between the legs of the loop, substantially as indicated in Fig. 5. When the volume and velocity of air flow through the igniter is adjusted to extend the are about one inch beyond the electrodes, the temperature in the loop of the arc is about 400 F., and as the air flow through the igniter is increased, the arc is extended to an increased distance beyond the electrodes and appears to increase in thickness or cross-section and to become more dense, and the temperature within the loop of the arc increases until the arc is extended about 4 inches beyond the electrodes and the temperature in the loop of the arc reaches l,000 to 1,200 E, when the optimum ignition eificiency appears to be attained. Increase of air flow through the igniter to further extend the are beyond the electrodes results in a drop in temperature in the loop of the are. Satisfactory ignition of atomized fuel is attained when the electrodes are supplied with current of from 50 to 100 milliamperes, the air current through the igniter is adjusted to extend the are beyond the electrodes to an extent ranging between 1 to 4 inches, and the temperature in the loop of the arc ranges between 400 and 1,000 F.

When the are produced by passage of the electric current between the electrodes is blown in its extended, flame-like form, ionization takes place which results in separation of the elements of the atmosphere, principally nitrogen and oxygen, and under the influence of the heat developed by the current flowing in the arc, nitrogen, nitric oXide and free oxygen are present in the vicinity of the elongated arc. When the free oxygen comes into contact with the mixture of oil and air, instantaneous ignition and combustion of the fuel takes place, comparable with the well known phenomena of explosion whenever free oxygen comes into contact with hydrocarbons in any state.

After the fuel spray from each jet nozzle has been ignited, the supply of electric current to the igniters may be cut off as the flames from the jet nozzles will be sustained under normal conditions by the incoming fuel and compressed air, but the flow of air through the tubular member of the igniter is continued, thereby cooling the igniter, and especially the insulator for the central electrode, from the destructive effect of the high temperature of the burning gases in the combustion chamber.

Jet driven airplanes employing a gas turbine power plant operate most efiiciently at very high altitudes, but it has been found that at such high altitudes where the temperature of the atmosphere may be many degrees below zero Fahrenheit, the flame in the combustion chamber is liable to become extinguished or fail to burn properly, due probably to the cooling effect of such very cold air on the flame in the combustion chamber. In order to remedy or relieve such a condition, means may be provided for the introduction of an inflammable gas through the igniter to be ignited by the arc. Such an inflammable gas as butane or propane may be stored in a tank 50 and connected to a header 5|, the latter being connected by branch pipes 52 with the respective igniters, each of the branch pipes being preferably provided with a valve 53 for regulating the supply of such an inflammable gas. As shown in Fig. 3, the branch pipe 52 for the supply of inflammable gas is connected to the air supply pipe 3|, and by appropriately adjusting the valves 3 la and 53 an appropriate proportion of the gas to air may be obtained.

Fig. 4 shows a modification in which the pipe 52a for the supply of inflammable gas is connected, through an electrical insulating sleeve 54, to the central electrode 32a which in this instance is hollow or tubular, so that the gas in passing through the hollow electrode will cool it and the surrounding insulator.

In either of the arrangements shown in Figs. 3 and 4, the highly inflammable supplemental gas supply to the electric are produced between the electrodes of the igniter, when ignited by the arc, provides a very hot flame which will ignite the fuel sprayed in the combustion chamber, notwithstanding the cooling effect of very cold and rarefied air at high altitudes to ensure easy starting of combustion of the fuel on which the plant operates, and to overcome or prevent flame failure in the combustion chamber. Adjustment of the proportion of oxygen to inflammable gas ensures efiicient burning of this supplemental inflammable gas supply, as such gases burn most efficiently when mixed with an appropriate percentage of oxygen.

The invention is shown applied in the present instance to a conventional type of gas turbine power plant for propulsion of aircraft employing an axial flow compressor which is driven from assume a a gas turbine axially alined therewith and which takes in air through an annular opening at its forward end and compresses the air and delivers it to an annular combustion chamber or an annular series of combustion chambers in which liquid fuel is sprayed and the sprayed liquid is ignited by an annular series of igniters in the annular combustion chamber or in the respective combustion chambers of the series, but it is to be understood that the invention is also applicable to aircraft of the so-called ram-jet type in which the forward speed of the aircraft in flight is sufficient to compress the air sufflciently for com- .bustion of the fuel supplied thereto without requiring the use of a comprsseor.

It is also to be understood that although the invention is shown in the present instance as applied to a turbine power plant of a conventional type in which the power developed is used for driving a propeller at its forward end and the combusted gases exhausting from the turbine at its rear end are utilized for jet propulsion, the power plant may be of the type in .or No. 6 fuel oil (bunker C, 6-16B.), which can not be ignited by an ordinary spark plug supplied as usual with an electric current of from 5,000 to 10,000 volts and a current strength of about 20 milliamperes, thereby enabling such available and less expensive heavier grades of oil to be used economically as fuel.

By maintaining flow of a current of air through the igniter during operation of the plant, the igniter is cooled and thereby protected from the destructive effects of the high temperature of combustion in the combustion chamber.

We claim:

1. The method of igniting fuel in an internal combustion engine, comprising atomizing the fuel and spraying the atomized fuel in the form of a jet into a current of compressed air to form a flowing current of combustible mixture, forming a high tension electric arc in proximity to the flowing current of combustible mixture, and directing another current of air against the arc in sufficient volume and velocity to elongate the arc and extend it into the flowing current of combustible mixture.

2. The method of igniting fuel in a gas turbine plant of the type comprising a combustion chamber, a compressor for supplying compressed air to said chamber to flow therethrough, means for feeding fuel to the combustion chamber for combustion therein, and a gas turbine arranged to receive combusted gases from the combustion chamber, which method comprises spraying atomized fuel into the air flowing through the combustion chamber to form a flowing current of combustible mixture, forming a high tension electric arc in the combustion chamber in proximity to the path of the flowing current of combustible mixture, and directing another current of air against the arc in sufficient volume and velocity in a direction transverse to the current of combustible mixture to elongate the arc and extend it into the flowing current of combustible mixture.

3. The method of igniting fuel in a gas turbine plant of the type comprising a combustion chamber, a compressor for inducing flow of a current of compressed air through the combustion chamber, means for feeding fuel to the combution chamber for combustion therein, and a gas turbine arranged to receive combusted gases from the combustion chamber, which method comprises spraying atomized fuel into the current of air flowing through the combustion chamber to form a flowing current of combustible mixture, producing a high tension electric are between electrodes adjacent to the path of the flowing current of combustible mixture, and directing another current of air past the electrodes in sufficient volume and velocity and in a direction transversely of said current of combustible mixture to extend the are beyond the electrodes and into the flowing current of combustible mixture.

4. The method of igniting fuel in a gas turbine plant of the type comprising a combustion chamber, a compressor for supplying a current of compressed air to flow through the combustion chamber, means for supplying fuel to the combustion chamber, and a gas turbine arranged to receive combusted gases from the combustion chamber, which method comprises spraying atomized fuel into the combustion chamber to continuing the flow of the current of air past the electrodes.

5. The method of igniting fuel in a gas turbine plant of the type comprising a combustion chamber, a compressor for inducing flow of a current of compressed air through the combustion chamber, means for feeding fuel to the combustion chamber for combustion therein, and a gas turbine arranged to receive combusted gases from the combustion chamber, which comprises spraying atomized fuel into the current of compressed air fiowing through the combustion chamber to form a flowing current of combustible mixture, producing a high tension electric are between electrodes adjacent to the path of the flowing current of combustible mixture, and directing a current of air at a pressure higher than that of said current of compressed air past the electrodes in suflicient volume and velocity to extend the arc beyond the electrodes and into the flowing current of combustible mixture.

6. An igniter for an internal combustion engine having means for producing a current of air and means for spraying atomized fuel in a combustion chamber to form a flowing current of combustible mixture, comprising electrodes in proximity to the path of the flowing current of combustible mixture, means for supplying electric current to the electrodes sufficient in intensity to produce an electric arc between them and to maintain such are in elongated form, and means for directing a current of air past the electrodes to elongate the arc beyond them and 7 into the :fiowing current of combustible mixtur '7. An igniter for a :gas turbine plant of the type having a combustion chamber openat rbOth ends, a compressor for applying .a current 01' compressed air 'to one .end :of the .combustion -rent to the electrodes to establishan :electric are between them and to maintain such are in extended relation to the electrodes, and means-for conducting a current of air past the electrodes in a direction transverse :to the current of combustible mixture to elongate the arc and extend it from the .electrodes and into the current of combustible mixture.

8. An igniter for a gas turbine .plant of the type having a combustion chamber open-at both ends and adapted to receive a current of compressed air and a supply 'of fuel to ;form a current of combustible.mixturefor flow through and to discharge from the combustion chamber, comprising electrodes .located in a wall of the com- .bustion chamber adjacent to the path of the current of combustible mixture and downstream from-the jet nozzle, means for supplying anelec- .tric current to the electrodes toproduce anelectrio are between them, and means for conducting .a. current of air at a pressure higher than that ofsaid current of compressed'air past the electrodes into the combustion chamber in a direction transverse to the flowing current .of combustible mixture to elongate the arc and extend it into said flowing current of combustible mixture.

9. A gas turbine power plant comprising a combustion chamber,a compressor for supplying a current of compressed air to said chamber,

:means for spraying fuel in the combustion cham- :ber :to produce a current .of combustible mixture for combustion therein, a turbine arran ed to receive combusted gases from the combustion chamber and connected to the compressor :or driving it, a .fuel 'igniter comprising electrodes positioned in a wall of the combustion chamber .a'longwhich the current of combustible mixture flows, means for supplying an electric current to :the electrodes of .suflicient intensity to produce an electric are between the electrodes and "to maintain such an arc in extended relation thereto, means driven by the turbine and separate from the compressor for compressing air to a pressure higher than the pressure :in thecombus- 'tion chamber, and means for conducting 0, current of such higher pressure air past the electrodes to elongate the arc and extend it beyond the electrodes and into the current of combustible .mixture.

10. A .gas turbine power plant as defined in claim-9, wherein said means for compressing air to a higher pressure comprises a pump connected to receive compressed air discharged by said compressor, and is operative to increase the pressure thereof.

EDWARD J. CAKES. RALPH K. ROTHROCK.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,695,152 Martindale Dec. 11, 1928 1,920,460 Bruns Aug. 1, 1933 1,948,663 Irwin Feb. 27, 1934 2,326,072 Seippel Aug. 3, 19.43 2,465,092 Harkness Mar. 22, 1949 2,493,743 Benson Jan. 10, 1950 2,581,999 Blatz Jan. 8, 1952 FOREIGN PATENTS Number Name Date 134,368 Austria July 25, 19,33