POD-based analysis of cycle-to-cycle variations in an optically accessible diesel engine

This paper reports on cycle-resolved, 2D measurements of combustion chamber luminosity made using an optically accessible diesel engine equipped with a common rail (CR) injection system. Images of combustion were acquired with a complementary metal oxide semiconductor (CMOS) camera at various stages during multiple fuel injection events. Images from consecutive cycles are analyzed with proper orthogonal decomposition (POD) to extract a relatively small number of characteristic scalar coefficients from the pixel patterns. These coefficients are then used to characterize the cyclic variability in terms of coherent and incoherent components of the luminosity field.