The objective of this investigation was to compare the results of metallurgical temperature sensors and thermocouples when used to measure piston temperatures in a running engine. Type J thermocouples and a microwave wireless telemetry system were used to gather real time temperature data on the piston in the vicinity of each metallurgical sensor. Eight pairs of metallurgical temperature sensors were installed in the piston with a thermocouple junction in-between. The engine was ramped up to steady state quickly and then held for approximately 4 h at 1800 rpm and 1980 Nm before being quickly ramped back down in accordance with the metallurgical sensors' recommended test cycle. During the test, continuous temperature data at each of the sensor locations were monitored and recorded using the telemetry system. After the test was complete, the metallurgical temperature sensors were removed and independently analyzed. The results indicate that readings from the metallurgical temperature sensors were similar to those of the embedded thermocouples for locations without large thermal gradients. However, when thermal gradients were present, the metallurgical sensor's reading was influenced measurably. TempiugsTempiugs were developed in the early 1970s through a joint effort between Testing Engineers Inc. (TEI) and Shell Research Ltd. They are made from one of two types of hardened alloy steels. They utilize the process of thermal tempering (thermal softening). Calibration curves of the alloy steels were originally developed by Shell; however, a new manufacturer, Vemolab, has created revised alloys and corresponding calibration curves which are used to calculate the maximum sustained temperature of the Templug. An example calibration curve is shown in Fig. 1.Two versions of Tempiugs are available for different temperature ranges. The No. 2 steel Templug has a usable range of 74-649°C, while the No. 3 steel version has a usable range of Journal of Engineering for Gas Turbines and Power

The objective of this investigation was to compare the results of metallurgical temperature sensors and thermocouples when used to measure piston temperatures in a running engine. Type J thermocouples and a microwave wireless telemetry system were used to gather real time temperature data on the piston in the vicinity of each metallurgical sensor. Eight pairs of metallurgical temperature sensors were installed in the piston with a thermocouple junction in-between. The engine was ramped up to steady state quickly and then held for approximately four hours at 1800 RPM and 1980 N-m before being quickly ramped back down in accordance with the metallurgical sensors’ recommended test cycle. During the test, continuous temperature data at each of the sensor locations was monitored and recorded using the telemetry system. After the test was complete, the metallurgical temperature sensors were removed and independently analyzed. The results indicate that readings from the metallurgical temperature sensors were similar to those of the embedded thermocouples for locations without large thermal gradients. However, when thermal gradients were present, the metallurgical sensor’s reading was influenced measurably.

Wireless microwave telemetry addresses the difficult issue of obtaining transducer outputs from reciprocating and rotating components through the use of advanced electronic components. This eliminates the requirements of a direct link between the transducer and the acquisition system. Accuracy of the transducer signal is maintained through the use of a double frequency modulation technique which provides temperature stability and a 20 point calibration of the complete system. Multiple transmitters can be used for larger applications and multiple antennas can be used to improve the signal strength and reduce the possibility of dropouts. Examples of automotive torque converter and piston temperature measurements are provided, showing the effectiveness of the wireless measuring technique.

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Wireless microwave telemetry addresses the difficult issue of obtaining transducer outputs from reciprocating and rotating components through the use of advanced electronic components. This eliminates the requirements of a direct link between the transducer and the acquisition system. Accuracy of the transducer signal is maintained through the use of a double frequency modulation (FM) technique which provides temperature stability and a 20 point calibration of each, complete system. Multiple transmitters can be used for larger applications and multiple antennas can be used to improve the signal strength and reduce the possibility of dropouts. Examples of piston temperature and automotive torque converter measurements are provided, showing the effectiveness of the wireless measuring technique.