The temperature measurement system uses the established technology of Tunable Diode Laser Absorption Spectroscopy (TDLAS).
To measure temperature, a laser beam, carried by optical fibres through a probe having the form of a spark plug, is transmitted across a short segment of the cylinder of an engine. The laser beam is then partially absorbed by gases in the cylinder at two discrete wavelengths. And by determining the ratio of absorbance of the laser at the two wavelengths, the gas temperature can be calculated.
Nissan’s specific role was in the optical design of temperature probe and overall project management, while
Previous methods to measure the temperature required modifications to the engine. But it was difficult to acquire useful data from methods such as attaching sensors inside the cylinder wall or estimating the temperature from camera images of the flame obtained in a specially modified optical-access engine.
Detailed results from the system will be published by the