Abstract
The paper introduces the improved LDA flow rate meter to measure the fuel injection rate in the internal combustion engine. LDA flow rate meter is based on laser Doppler anemometer, it only measures one point time-series velocity on the center of circular pipe. After then, it provides instantaneous flow rate and integral mass of the flow. In this paper, it measured the high pressure injection system of the direct-injection engine. In the measurement, the fuel pressure is changed from 5MPa to 20MPa and injection time is changed from 0.5ms to 5ms.