Analysis of cycle-to-cycle variations in IC engines using highspeed Tomographic Particle-Image Velocimetry

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The development of modern combustion engines focuses on the increase of the energy efficiency by simultaneously reducing pollutant emissions and fuel consumption. Novel combustion concepts like controlled auto ignition (CAI) and homogeneous charge compression ignition (HCCI) require a homogeneous air-fuel mixture which is generated during the inlet and compression stroke, hence prior to ignition. However, the three-dimensional unsteady large-scale flow structures that evolve during those strokes are subject to variations from cycle to cycle with respect to their spatial and temporal development. On the one hand, the reasons for these cycle-to-cycle variations (CCV) and their influencing factors are not completely analyzed, yet. On the other hand, the suppression and controlled influence of these cyclic variations is an indispensable prerequisite for the successful application of the aforementioned combustion concepts. Hence, a detailed analysis of the three-dimensional and time-dependent cyclic variations in internal combustion engines demands for a volumetric measurement technique with high spatial and temporal resolution. The objective of this proposal is to prove that high-speed tomographic particle-image velocimetry (HS-TPIV) is capable of analyzing these cyclic variations by investigating the CCV during the inlet and compression stroke for an exemplary parameter set with defined inlet conditions. For this purpose, the three-dimensional flow field in the cylinder will be measured using HS-TPIV and analyzed on the basis of three-dimensional POD-algorithms to determine the influencing factors for the development of cycle-to-cycle variations.