3-D velocimetry visualizes combustion engine airflow

Understanding airflow within a combustion engine is critical for improving engine operation since this can dramatically affect efficiency. However, because 3-D volumetric data are needed to fully quantify these flows and limited optical access is available, existing flow measurement techniques are ill-suited to the task.

To overcome this, Kevin Peterson, PhD, at the University of Michigan (www.umich.edu) developed a method for measuring 3-D airflow inside an optically accessible combustion engine. The single-camera, 3-D particle tracking velocimetry (SC3D-PTV) method can perform 3-D flow measurements with limited optical access over a measurement volume on the order of tens of cubic millimeters, leading to a greater understanding of in-cylinder flow and improved engine operation.

The optical element used for SC3D-PTV is similar to a stereo microscope. A single large lens and two smaller lenses are used to create two parallel imaging systems within a single housing. The two imaging systems view the same measurement volume from different angles but share a focal plane. For clarity, this is shown in the figure for two separate cameras but also applies to the single camera setup of SC3D-PTV.

The SC3D-PTV method allows the simultaneous capture of the 3-D position of numerous tracer particles suspended in a nonstationary fluid. The 3-D velocity profile of the particle field is then obtained by computing the displacement of each particle between consecutive exposures.

Peterson performed the work in partial fulfillment of the requirements for the degree of doctor of philosophy in mechanical engineering. His dissertation can be found athttp://bit.ly/TsOxbq.