An advanced Laser-based Airflow Sensor for Non-intrusive Diesel Engine Characterization

This porposal is concerned with the development of a rugged, accurate and non-intrusive electro-optical device to reliably measure the unsteady airflow into a reciprocating internal combustion engine. The principle of operation of the proposed sensor is laser Doppler velocimetry, a technique that allows for velocity measurements without interfering with the flow. The proposed sensor presents the following advantages when compared to other methodologies: it is robust; it requires no calibration; its sensitivity to changes in environmental conditions is minimal; presents no fouling problems; it can be used to measure both the inlet and exhaust streams; it is highly accurate; and has a very high frequency response. The sensor can be used for both laboratory and inflight tests. New processing techniques, and recent advances in solid- state technology make the construction of this rugged sensor possible. It is expected to be competitve with existing airflow measurement technology, both in terms of performance and price. Since laser Doppler velocimetry is an interferometrtic tschnique, the presence of contaminants or other substances in the inlet stream will only affect the signal-to-noise ratio of the signals, but not the velocity measurements. Also, since the technique is optical in nature, no obstructions or foreign objects are present in the inlet stream path. These features make this unique sensor to be highly reliable and accurate, while not affecting the engine's performance.