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This paper presents the first results towards experimentally resolving the local three-dimensional (3D) flame propagation and turbulence-chemistry-interaction in a spark-ignition engine using temporally resolved multi-planar laser diagnostics. The experimental method utilizes simultaneous dual-plane laser induced fluorescence (LIF) of OH and stereoscopic PIV (SPIV) to locally resolve 3D flame displacement speed during the early flame development when less than 5% of the mass has been consumed. OH-LIF is used to track the reaction-zone position and flame normal direction in 3D space, while SPIV measures the convection of the identified flame contours. Based on the vectorial difference of the 3D convection and absolute propagation of the reaction-zone, the 3D displacement speed (s T) is calculated. An instantaneous flame realization shows a large dynamic range of local s T and local flow transport, while also revealing the importance to resolve these quantities in 3D. Several flame-flow configurations are shown along the flame surface and each uniquely defined the local flame transport along the individual flame realization. A detailed uncertainty and sensitivity analysis is performed, confirming the validity of the s T distribution resolved for the methodology and operating conditions. A discussion on the different mechanisms leading to the large distribution of s T for the given operations is included and testifies to complex nature of the in-cylinder flame development in this early stage. The limitations of the presented methodology are discussed particularly in the need for improved spatial resolution and additional volumetric information. The merits and limitations of the presented work provides an improved understanding of what is further needed to better resolve local 3D flame transport in engines for both experimental and numerical methodologies.

Magnetic resonance velocimetry (MRV) measurements are performed in a 1:1 scale model of a singlecylinder optical engine to investigate the volumetric flow within the intake and cylinder geometry during flow induction. The model is a steady flow water analogue of the optical IC-engine with a fixed valve lift of 9:21 mm to simulate the induction flow at crank-angle 270 bTDC. This setup resembles a steady flow engine test bench configuration. MRV measurements are validated with phaseaveraged particle image velocimetry (PIV) measurements performed within the symmetry plane of the optical engine. Differences in experimental operating parameters between MRV and PIV measurements are well addressed. Comparison of MRV and PIV measurements is demonstrated using normalized mean velocity component profiles and showed excellent agreement in the upper portion of the cylinder chamber (i.e., y ! À 20 mm). MRV measurements are further used to analyze the ensemble average volumetric flow within the 3D engine domain. Measurements are used to describe the 3D overflow and underflow behavior as the annular flow enters the cylinder chamber. Flow features such as the annular jet-like flows extending into the cylinder, their influence on large-scale in-cylinder flow motion, as well as flow recirculation zones are identified in 3D space. Inlet flow velocities are analyzed around the entire valve curtain perimeter to quantify percent mass flow rate entering the cylinder. Recirculation zones associated with the underflow are shown to reduce local mass flow rates up to 50 %. Recirculation zones are further analyzed in 3D space within the intake manifold and cylinder chamber. It is suggested that such recirculation zones can have large implications on cylinder charge filling and variations of the in-cylinder flow pattern. MRV is revealed to be an important diagnostic tool used to understand the volumetric induction flow within engine geometries and is potentially suited to evaluate flow changes due to intake geometry modifications.

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