Measurement of Air Flow Around an Inlet Valve Using a Pitot Probe

This paper describes a detailed study into the use of a pitot probe to measure air flow around an inlet valve under steady state conditions. The study was undertaken to assess the feasibility of the method for locating areas of a port and valve which may be contributing to a poor overall discharge coefficient. This method would provide a simple and cheap experimental tool for use throughout the industry.

The method involves mounting a miniature internal chamfer pitot tube on a slider attached to the base of the valve. The probe can traverse the appropriate area by rotating the valve and moving it along the slide. Changing the probe allows measurements in different planes, allowing the whole region around the valve to be surveyed. The cylinder head complete with instrumentation is mounted on a steady flow rig.

The paper presents the results obtained at different valve lifts on a production cylinder head. The effect of pitot tip orientation is discussed and the integrated mass flow compared with that obtained from an air flow meter. The method is shown to work well for low lifts prior to the point where tumble is initiated. The method is used to reveal the change in flow due to a port modification responsible for a small reduction in discharge coefficient.