FIELD OF THE INVENTION

The present invention relates generally to a thermocouple system and more particularly to a method for optimizing a thermocouple system being used with gas turbine engines.

BACKGROUND OF THE INVENTION

In the operation of turbo-fan, turbo-shaft, turbo jet or jet aircraft, the temperature of the aircraft gas or jet stream must be maintained and controlled within a critical range; below which insufficient thrust or efficiency is indicated, and above which damage to the engine and aircraft may be caused.

Modern aircraft that are operating at high speeds are known to be subjected to great stress, strain and shock. Accordingly, the thermocouple apparatus must not only be adapted to elevated states and rapid changes of temperature, it must also be characterized by robust design and construction to reliably operate at these severe environmental conditions. Additionally, the thermocouples have to be located at points spaced about the periphery of the gas turbine tail cone or pipe in order to obtain meaningful temperature measurements. Furthermore, the thermocouples are mounted about the tail cone or pipe of a gas turbine in such a way that the failure of any one or more of the thermocouples does not affect or nullify the functioning of any other of the thermocouples, and so that their total or average indication is utilized as the significant value or measurement of gas stream temperature. These multiple thermocouple arrangements are conventionally characterized still further, and in one type by the connection of resistors in series with the thermocouples to balance or equalize their influence on the indicated output. In another form, the averaging may be carried out by circuitry or parallel connection of the thermocouples. In either case, the multiple or combined thermocouple arrangement must be capable of continuously operating notwithstanding any damage or single point failures.

Moreover, the design of the thermocouple apparatus, such as here concerned, may be governed further by the fact that the temperatures obtained in any of the several cross-sections of the aircraft gas stream may vary considerably, whereby a meaningful measurement may require the averaging of a number of readings taken at a number of locations. The thermocouple signal is transmitted through common terminals to the desired recording, indicating and controlling instruments, which are typically remotely located and which are capable of deriving and measuring a net electromotive force (E.M.F.). Thus, the thermocouples and harness apparatuses here concerned typically include a set of heat sensing probes arranged about the tail cone or pipe of a gas turbine, and an assembly of coupled thermocouple wire segments constructed and arranged as electrical connections to the thermocouples. These may serve to transmit the aforementioned signal to the cockpit, EEC and/or other aircraft equipment.

SUMMARY OF THE INVENTION

Briefly stated, conventional thermocouple harness technology employs equal wire length as a means of balancing the series resistance of thermocouple channels. This invention utilizes a scientific model to analyze thermocouple systems and take advantage of the systems' degrees of freedom to optimize designs, which in turn allows significant savings in wire, weight, size and cost of manufacturing the complete thermocouple harnesses.

A Thermocouple System (TCS) is provided and includes a junction box, a first thermocouple probe, wherein the first thermocouple probe includes a first positive terminal connected with the junction box via a first positive leg having a First Positive Harness Wire and a first positive probe wire, and a first negative terminal connected with the junction box via a first negative leg having a First Negative Harness Wire and a first negative probe wire. Additionally, a second thermocouple probe is provided, wherein the second thermocouple probe includes a second positive terminal connected with the junction box via a second positive leg having a Second Positive Harness Wire and a second positive probe wire, and a second negative terminal connected with the junction box via a second negative leg having a Second Negative Harness Wire and a second negative probe wire, wherein the TCS includes a total system resistance and wherein the First Positive Harness Wire includes a first positive harness wire length, the First Negative Harness Wire includes a first negative harness wire length, the Second Positive Harness Wire includes a second positive harness wire length and the Second Negative Harness Wire includes a second negative harness wire length, and wherein at least one of the first positive harness wire length, second positive harness wire length, first negative harness wire length and second negative harness wire length are configured such that the total system resistance is balanced between the first thermocouple probe and the second thermocouple probe.

A Thermocouple System (TCS) is provided and includes a junction box, a first thermocouple probe, wherein the first thermocouple probe includes a first positive terminal connected with the junction box via a first positive leg and a first negative terminal connected with the junction box via a first negative leg, wherein the first positive leg includes a first positive leg resistance and a First Positive Harness Wire having a First Positive Harness Wire length, and the first negative leg includes a first negative leg resistance and a First Negative Harness Wire having a First Negative Harness Wire length, and at least one additional thermocouple probe, wherein the at least one additional thermocouple probe includes a second thermocouple probe having a second positive terminal connected with the junction box via a second positive leg and a second negative terminal connected with the junction box via a second negative leg, wherein the second positive leg includes a second positive leg resistance and a Second Positive Harness Wire having a Second Positive Harness Wire length and the second negative leg includes a second negative leg resistance and a Second Negative Harness Wire having a Second Negative Harness Wire length, and wherein the First Negative Harness Wire length and Second Negative Harness Wire length are configured to be minimized and wherein the sum of the second positive leg resistance and the second negative leg resistance is substantially equal to the sum of the first positive leg resistance and the first negative leg resistance.

A method of optimizing a thermocouple system having a plurality of thermocouple probes and a junction box is provided and includes examining the thermocouple system to identify a first thermocouple probe of the plurality of thermocouple probes, wherein the first thermocouple probe includes a first positive leg and a first negative leg and is located electrically farthest from the junction box, calculating a first loop resistance between the first thermocouple probe and the junction box and configuring a second thermocouple probe of the plurality of thermocouple probes having a second positive leg, a second negative leg and a second loop resistance such that the second loop resistance is substantially equal to the first loop resistance.

