US3138924A

US3138924A - Ignition system for a gas turbine engine

Info

Publication number: US3138924A
Application number: US39898A
Authority: US
Inventors: John J Lawser
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1960-06-30
Filing date: 1960-06-30
Publication date: 1964-06-30
Anticipated expiration: 1981-06-30

Description

June 30, 1964 J. .1. LAWSER 3,133,924

IGNITION SYSTEM FOR A GAS TURBINE ENGINE Filed June 30, 1960 CK/HMBER JOHN J. 419 W651? IN V EN TOR.

BY y. we. 7

. Fix.

ATTOR/V'f United States Patent 3,138,924 IGNITION SYSTEM FOR A GAS TURBINE ENGINE John J. Lawser, Dearbom, Mich, assignor to Ford Motor Company, Dearborn, Mich, a corporation of Delaware Fiied June 30, 1960, Ser. No. 39,898

. 1 Claim. (Cl. 6039.14)

This invention relates to a starting and ignition system for a gas turbine engine and more particularly to a starting and ignition system for a gas turbine engine in which an igniter is energized from a low voltage-high current source simultaneously with the energization of an electrical power means connected to start said gas. turbine engine.

In gas turbine engines a need exists for a simple and inexpensive means for supplying low voltage-high current electrical energy to an igniter positioned in the combustion chamber of a gas turbine engine at the time the engine is started. This type of source provides suflicient power for the igniter and assures long igniter life since the igniter operates at low voltage. The igniter should preferably be energized simultaneously with the energization of the electrical power means that are connected to rotate the compressor or turbine of the engine.

The applicant has provided a novel solution to this problem by providing a starting and ignition circuit in which an igniter, preferably of the glow plug type, is connected across an electrical conductor connected between a source of electrical energy and an electrical power means connected to said gas turbine engine. This arrangement provides a low Voltage-high current source for the igniter since the voltage drop across this conductor is quite small and since the high current drawn by the electrical power means during starting is available.

An object of the invention is the provision of a starting and ignition system for a gas turbine engine that is simple, uncomplicated and inexpensive.

Another object of the invention is the provision of a starting and ignition system for a gas turbine engine in which an igniter is energized from a low voltage-high current source simultaneously with the energization of a starting circuit for said engine.

A further object of the invention is the provision of a starting and ignition system for a gas turbine engine that assures long life for a glow plug igniter employed with the engine.

Other objects and attendant advantages of the present invention will become more readily apparent as the specification is considered in connection with the attached drawing in which the single figure thereof shows the invention is schematic form.

Referring now to the drawing, there is shown a gas turbine engine of conventional design generally designated by the numeral 11. The gas turbine engine includes a compressor and turbine (not shown). An electrical power means preferably starting motor 12 of conventional electrical design is adapted to be connected to the gas turbine engine, preferably the compressor thereof, through a coupling, designated by the numeral 13. The gas turbine engine also includes a combustion chamber 14 of conventional construction such as those shown in United States Patents 2,768,497, issued October 30, 1956, to C. F. Hayes, and 2,872,971, issued February 10, 1959, to I. S. Clarke et al. An igniter 15 of the glow plug type is positioned within the combustion chamber 14. This glow plug may be of the type disclosed in my copending application Serial No. 693,059, filed October 29, 1957, or the types disclosed in my copending application Serial No. 693,060, also filed October 29, 1957. These applications have matured into Patents No. 3,017,540 and No. 3,017,541, respectively, both issued January 16, 1962.

3,138,924 Patented June 30, 1964 The starting motor 12 and the igniter 15 are adapted to be energized from a source of electrical energy, for example, a storage battery or a plurality of storage batteries, designated by the numeral 16, through an ignition switch 17 that preferably takes the form of a relay. The battery includes a negative terminal 21 connected to ground through a lead 22, and a positive terminal 23 connected to a first terminal 24 of switch or relay 17 through a lead 25. The positive terminal 23 of the battery 16 is also connected to one terminal of relay winding 26 through a hand switch 27 and a lead 28. The other end of the relay winding 26 is connected to ground through a lead 29. The other terminal 31 of the switch or relay 17 is connected to a first terminal 32 of starting motor 12 through a low resistance electrical conductor 33. The other terminal 34 of the starting motor 12 is connected to ground through a lead 35.

The glow plug igniter 15 is connected across or in parallel with the conductor 33. This is preferably accomplished by having one terminal 36 thereof connected through lead 37 to one end of the conductor 33, at the terminal 31 of switch 17, and by having the other terminal 38 connected through lead 39 to the other end of the conductor 33, by a connection to the terminal 32 of starting motor 12.

In the operation of the device the hand switch 27 is closed thereby energizing the Winding 26 and closing switch or relay 17. This action energizes the starter motor 12 from the battery 16 via lead 25, relay or switch 17, and electrical conductor 33. Although the electrical resistance of the electrical conductor is low, a small voltage drop will occur between

terminals

31 and 32. This causes a current to flow in the glow plug igniter 15 to bring it to its incandescent point where it is capable of igniting a fuelair mixture present in combustion chamber 14. The starting motor 12 rotates the compressor of the gas turbine engine 11 to supply the air for the combustion chamber 14 and fuel is fed to the combustion chamber from any suitable source (not shown).

When the gas turbine engine is capable of running under its own power, the starting motor 12 and the glow plug igniter 15 may be deenergized by opening the hand switch 27.

The present invention may employ components having the following values which are given by way of example only. For example, the starting motor 12 and the battery 16 may be of such size that the motor will draw from 1300 to 1850 amperes when it is energized. The electrical conductor 33 may be a low resistance cable having a resistance of approximately 0.001 ohm while the glow piling igniter may have a resistance of approximately 0.04 o

The following table discloses the starting motor current, the voltage drop across the conductor 33, and the power dissipated by the glow plug 15 during the first twelve seconds of a starting cycle.

Voltage drop Power dissipa- Starting across contion of glow Time, seconds motor ductor 33, lug igniter current, having 0.001 aving 0.04

amps ohm resistance ohm resistance in watts It is apparent from an inspection of the table that the transient current drawn by the motor at the beginning of the starting cycle provides higher power dissipation and hence enables the igniter to reach higher operating temperatures faster than if the igniter were operated at a constant voltage. A good igniter can operate at steady state over a 2:1 extreme voltage ratio, and as is apparent from an inspection of the table, the peak voltage supplied to the igniter is less than two times the voltage after near steady state conditions have been reached in twelve seconds.

The present invention thus provides a simple and inexpensive starting and ignition system for a gas turbine engine in which an igniter is energized from a low voltage-high current source simultaneously with the energization of an electrical power means connected to start the gas turbine engine.

It will be understood that the invention is not to be limited to the exact construction shown and described, but that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claim.

I claim:

In an ignition system for a gas turbine engine, a starting motor, a source of electrical energy for energizing said starting motor, an'ignition switch having a first terminal connected to said source of electrical energy, an electrical conductor connected to a second terminal of said ignition switch and to a terminal of said starting motor, said gas turbine engine including a combustion chamber, a glow plug igniter positioned in said combustion chamber and being connected across said electrical conductor with one terminal thereof connected to said second terminal of said ignition switch and with the other terminal thereof connected to said terminal of the starting motor.

References Cited in the file of this patent UNITED STATES PATENTS 2,443,648 Austin et al. June 22, 1948 2,613,499 Lawter Oct. 14, 1952 2,717,581 Edwards Sept. 13, 1955 2,730,862 Lamy Ian. 17, 1956 2,808,702 Dotson Oct. 8, 1957 2,924,935 Moore Feb. 16, 1960 2,928,240 Burton et a1 Mar. 15, 1960 2,935,843 Haviland May 10, 1960 2,962,597 Evans -2 Nov. 29, 1960