Multidimensional Measurements of the In-Cylinder Flow of a Four-Valve Internal Combustion Engine

The non-reacting flow in a one-cylinder four-valve combustion engine is measured by means of different laser optical measurement techniques. Furthermore, a holographic tomographic interferometry setup is developed and the capability to measure threedimensional density fields was shown by applying the system to a turbulent helium free jet. The flow field within the cylinder of the optical research engine is measured via cycle-resolved particle-image velocimetry (PIV) in eight planar planes for several crank angles during the intake and compression phase, first. Then, laser Doppler anemometry (LDA) measurements are performed at two different points within the cylinder during the intake and compression phase. Finally, fully three-dimensional holographic particleimage velocimetry (HPIV) measurements were conducted at a crank angle of 160° after top dead center. A measurement volume at a diameter of about 60 mm and aheightof approximately 80 mm was captured using a resolution of 0.75 mm. A total number of 600 000 velocity vectors were obtained within the cylinder of the optical research engine operated at 1 500 rpm. The three-dimensional structure of the velocity field is analyzed in detail. Therefore, phase-averaged statistics of the PIV results are visualized for characteristic crank angles during the intake and compression stroke by plotting the results of all measurement planes for a specific crank angle in a single figure. It was found that two ring vortices evolving beneath the inlet valves are the dominant large scale structures that seem to be of major concern for the mixing process in the cylinder of a four-valve combustion engine operated at 1 500 rpm. Furthermore, the temporal evolution of the flow field within the symmetry plane of the cylinder, measured for crank angles between 40° and 320° atdc in steps of 20°, is discussed. Finally, the results of the HPIV measurements are analyzed. Turbulent characteristics, e.g., integral length scales and turbulent kinetic energy spectra, were determined and discussed. The results give new insight into the complex three-dimensional flow in the combustion chamber of aone-cylinder four-valve combustion engine and evidence the capability of holographic measurement techniques to capture complex three-dimensional flow fields.