Abstract
Simultaneous measurements of the cylinder wall temperature at different locations are required to elucidate the heat transfer mechanisms on the cylinder wall of IC engines. In this paper, we present the development of a flexible wireless wall temperature sensor and its performance evaluation using a 4-stroke engine with a glass cylinder. The sensor, corresponding to an LCR resonant circuit, is attached on the inner surface of the cylinder, and its coil is inductively coupled with an external read-out coil that is located outside of the cylinder to measure the resonant frequency wirelessly. A Cu-laminated-polyimide film is used as the substrate of the sensor, on which a 1 mm-wide sensing resistor is sputtered. The resonant frequency is measured in a steady state from the room temperature to 200 °C, showing the mean sensitivity of 6.22 kHz/°C. Instantaneous measurement synchronized with the piston movement with a time interval of 1.2 ms is carried out for an optical engine operated at around 700 rpm. Change of permeability with the piston motion is compensated, and the crank angle-resolved cylinder temperature measurement has been made. Near the ignition timing, temperature increase by 44 °C is observed, which corresponds to the oncoming flame to the wall. Preliminary simultaneous multipoint measurement is also made with three sensors on the engine cylinder.
