This report describes a thermometric method utilizing an infrared fiber. The method is used for monitoring the piston temperature of the two-stroke cycle engine mounted on an outboard motor while the engine is in testing operation. The piston temperature measurement is an essential part of the engineering work for developing the reliability of the piston.
Traditionally, the piston temperature measurement was performed utilizing a thermocouple embedded in the piston. Every time the piston reaches the bottom dead center, the electrical signal from the thermocouple was picked up intermittently via a mechanical contact. However, uncertainty associated with the durability of the mechanical contact has restricted the running time of continuous measurement. The method described in this report was developed to address such difficulty.
In principle, the infra-red energy emitted by the piston depending on its temperature is detected via the infra-red fiber. Thus, the need for providing the contact was eliminated. The appropriate structure was configured for mounting the infrared fiber in the cylinder block, and the reproducibility tests have demonstrated the effectiveness of the method as the practically viable tool.
The method allows real-time measurement of the piston temperature with assured durability. The piston temperature measurements are taken in the form of ample mapped data, which enables quick and accurate evaluation for proper settings as well as their optimization.