High-Speed PIV: Applications in Engines and Future Prospects

Abstract

In this chapter we present the development of a high-speed imaging system for the measurement of automotive in-cylinder flows and sprays. High-speed imaging devices with framing rates of 12000 images per second or more produce engine data at a resolution of at least one crank angle degree crankshaft rotation with engine speeds of up to 2000. In combination with high repetition rate pulsed lasers synchronized with the camera it is shown that data on liquid-fuel distribution can be obtained and analyzed. With the introduction of artificial tracer particles and appropriate data-processing techniques planar vector fields are obtained at the same temporal resolution. For both the spray and flow image sequences the data is considered as 4-dimensional: two spatial axes in the measurement volume, one temporal axis within an engine cycle and a further temporal axis from one engine cycle to another. A statistical analysis of the data produces information on the cyclic variability of the spray and flow fields that are critical to modern combustion system design. Whilst a high volume of information can readily be created, the industrial requirements are for validation of computational models or to provide insight into the mixture-preparation mechanisms as a means of evolving the design process. Therefore, an emphasis of this chapter is to show how the large quantities of detailed optical measurement data may be reduced in such a way as to pass on the most significant performance data to powertrain specialists.