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Particle Image Velocimetry (PIV) here has been used to measure the instantaneous velocity field within a realistic geometry motored single cylinder engine. Through-the-piston-crown illumination of a vertical plane bisecting the inlet and exhaust valves in a four valve pent roof combustion chamber and the use of a corrective optical system has for the first time allowed the velocity field in a vertical plane within a cylindrical bore to be quantified with PIV. Techniques are described which permit accurate and repeatable camera focusing, laser to engine synchronisation and seeding density control. Large scale motion observed at 180° ATDC has been interpreted as barrel swirl. Limitations of the current technique are discussed with respect to general in-cylinder applications.

This paper describes two simple laser instruments which the automotive engineer can use in vibrational studies of diesel engines. The first is a ‘normal surface velocity’ instrument which the engineer can hand hold and simply ‘point’ at the target surface for measurement. Field tests have shown it to be quick and easy to use with excellent accuracy and reliability. It is a particular time-saver in test cell use where the necessity for many accelerometer fittings is removed. The second is a laser torsional vibrometer which can measure the torsional oscillation of rotating machinery parts. This has shown itself to be superior to the more standard techniques of slotted discs and slip rings, etc. and provides advantages of higher frequency response, greater accuracy and non-contact measurement. Conclusions drawn herald a step forward in measurement techniques and demonstrate the great potential of laser technology in heavy engineering applications.

The general problem of estimating the noise which vibrating surfaces will produce is discussed with particular application to diesel engines and their component parts. The measurement and prediction of engine noise balances using the surface vibration technique is described and the variation of engine block vibration with engine type and speed illustrated. Some measured radiation ratio’s for engine surfaces and components are given. Finally a method for measuring surface vibration on diesel engines using a laser doppler velocimeter is described.