Thermocouple Probe Cooling Jacket for Jet Engine Temperature Sensing
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Solution Overview
Problem
High-temperature thermocouples used in jet engines face challenges in accurately measuring temperatures in extreme environments due to material limitations, leading to increased costs and complexity in using more expensive platinum-rhodium thermocouples, and existing high-temperature probes require knowledge of gas composition, making them unsuitable for unknown or varying gases.
Innovation Solution
A thermocouple probe arrangement with a closed loop phase-change refrigeration cooling system and a method for determining temperature using a compensation factor, allowing cheaper thermocouples to operate in hotter environments by cooling the probe and accounting for coolant effects, enabling more accurate temperature sensing in high-temperature and hostile conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If platinum-rhodium thermocouples are used to operate at high temperatures up to 1600°C, then the thermocouple can withstand higher temperatures, but the cost increases significantly
Solution Approach 1:
A cooling jacket acts as an intermediary between the hot gas environment and the thermocouple, allowing cheaper K-type thermocouples to operate in high-temperature environments by mediating thermal exposure through active cooling
Solution Approach 2:
The thermocouple operating temperature is changed from direct exposure to high temperature to controlled lower temperature through the cooling system, enabling use of cheaper thermocouple materials
2Measurement precision
If the thermocouple is placed closer to the combustor to improve temperature measurement accuracy, then the measurement accuracy improves, but the thermocouple is exposed to higher temperatures requiring more expensive materials
Solution Approach 1:
The cooling jacket serves as a mediator that enables the thermocouple to be positioned close to the combustor for accurate measurement while protecting it from excessive heat through active cooling
Solution Approach 2:
The system separates the measurement function (thermocouple close to combustor) from the thermal protection function (cooling jacket), allowing the thermocouple to operate in a protected thermal environment while maintaining measurement accuracy
3Temperature
If a cooling arrangement is added to protect the thermocouple, then the thermocouple can operate in higher temperature environments, but the device complexity increases
Solution Approach 1:
A fluid-based cooling system is used to protect the thermocouple, leveraging hydraulic/pneumatic principles to circulate coolant through the cooling jacket and remove heat from the thermocouple environment
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables improved accuracy and cost-effectiveness in temperature sensing by allowing the use of cheaper thermocouples in high-temperature environments, while maintaining reliability and accuracy through the use of a cooling system and compensation factor, reducing the need for extensive qualifying tests and complex processing.
Implementation Method 1
A thermocouple probe arrangement with a closed loop phase-change refrigeration cooling system
Implementation Method 2
The cooling arrangement may be defined by a first intermediate tube immediately adjacent and around the thermocouple probe, and an outer tube surrounding the intermediate tube
Implementation Method 3
a thermocouple having a first sensing end with a hot junction for sensing the temperature in the jet engine
Implementation Method 4
passing a coolant through an area in thermal communication with at least a portion of the thermocouple probe inside the jet engine
Data Source
Figure 1
Figure 2~3b
Figure 4
AI summary
A cooled thermocouple arrangement (1) including a thermocouple (2) comprising two wires (3,4) joined at a first sensing end (5) to define a hot thermocouple function. At least a portion of the wires (3,4) are in thermal communication with a cooling arrangement, and the cooling arrangement has an inlet (14) for coolant and an outlet (15) for coolant. The thermocouple probe arrangement (1) includes a first inlet temperature sensor (21) for determining the temperature of the coolant as it enters the cooling arrangement, and a flow rate sensor (20) for determining the flow rate of coolant passing through the cooling arrangement. The thermocouple probe arrangement (1) includes connectors for connecting the outputs from the thermocouple (2), first inlet temperature sensor (21) and the flow rate sensor (20) to a correction data processor (23) whereby the data processor can correct the temperature sensed by the thermocouple to take account of the effect of the cooling arrangement. The pair of thermocouple wires (3,4) are arranged inside a sheath or casing, and a cooling jacket (12) is provided around the thermocouple probe. The cooling jacket (12) includes a pair of concentric tubes (16,17) defining a return coolant circuit from the end of the probe proximal the connectors (8), to a portion of the probe distal from the connectors, and then back to the proximal end (8) of the probe, and the portion of the thermocouple probe containing the sensing end (5) of the thermocouple projects from the distal end of the cooling jacket (12).