Southwest Research Institute® (SwRI®) News

Telemetry-based Piston Temperature Measurement System

San Antonio (Sept. 19, 1991) — A telemetry-based piston temperature measurement system designed for service inside operating reciprocating engines, developed by Southwest Research Institute® (SwRI®), has been selected to receive an R&D 100 Award in a competition conducted annually by R&D Magazine.

The award, recognizing the development as one of the 100 most significant new technical advances of the year, was announced Thursday by R&D Magazine in Chicago during ceremonies at the Museum of Science and Industry. Award winners were chose by a panel of 21 judges, including the editors.

The self-powered system uses a lightweight (31 grams), compact (1.5 X 0.625 X 0.562 inch) telemetry package bolted to the bottom of a piston, explained SwRI Project Manager Robert Burrahm. From sensors mounted at several points, temperature signals are sent to multiplexing circuitry, and then are radioed by a transmitter circuit (a single-transistor blocking oscillator) to a loop antenna in the engine crankcase. The signals then go by cable to a radio receiver and a computer for data storage and analysis.

The sensors are capacitive, responding to change in temperature by change in an electrical property, and differences in temperature are indicated by differences in the transmitting radio frequency. 

A key element is the power generator, which uses piston acceleration forces to move a steel slug back and forth through a magnetic field, producing alternating current to operate the system without need of a battery or external connections. 

The system was developed by a team including Project Manager Burrahm, a senior research scientist, and Research Engineer J. Keith Davis, both of the SwRI Engine, Fuel and Vehicle Research Division; and Assistant Director William Perry, Manager Armando de los Santos, and Group Leader William Tomlinson, all of the SwRI Instrumentation and Space Research Division. 

Development of this system is regarded as a significant technical innovation, research team members note, because it combines compact design using thick-film hybrid circuit construction with a novel power generation source to provide a practical solution to a difficult problem of obtaining critical data needed for design of tomorrow’s engines.

Many of today’s automobile and truck engines are power-limited by the ability of the piston to dissipate heat from the crown to surrounding surfaces. In the engines of two-stroke cycle design now being developed for future service, pistons are exposed to about 50 percent more heat than their four-stroke counterparts. Piston design is therefore an important parameter for new-fuel-efficient, low-emission engines.

The mapping of piston temperatures for that purpose requires instrumentation that functions practically and provides reliable data under severe conditions, including acceleration forces that approach 200 Gs, and piston temperatures near 600 F. The new system meets the requirements for this service, the team reports. 

For more information about the CIBLE Automatic Bearing Inspection System, contact Joe Fohn, Communications Department, Southwest Research Institute, P.O. Drawer 28510, San Antonio, Texas, 78228-0510, Phone (210) 522-4630, Fax (210) 522-3547.

SwRI News separate.gif (834 bytes) SwRI Home