Hot-Wire Anemometry in the Engine Cylinder

Abstract

In order to measure the air flow velocity in the cylinder of internal combustion engine by means of a hot-wire anemometer (constant temperature type), it is necessary to compensate the output of anemometer for the variations of air temperature and pressure and the conductive heat loss to the supports of hot-wire. The conductive heat loss to the wire supports depends on the temperature of the tip of support. In the engine cylinder, the support temperature varies with the crankangle.
The previous report had described a practical compensation method of the hot-wire anemometer output for the variation of air temperature and the heat loss to the hot-wire supports in the steady flow.
In this study, the effects of the pressure on the convective heat flow to the air and the conductive heat loss to the supports were investigated. Further, the behavior of the support temperature in the engine cylinder was studied, and a prediction method of the support temperature in the engine cylinder was discussed. As the result of this study, a practical compensation method of the hot-wire anemometer output for the variations of air temperature and pressure and the heat loss to the hot-wire supports was proposed.