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The performance of engine intake ports is traditionally characterized by pressure drop and in-cylinder swirl or tumble ill steady flow at discrete valve lifts. These characteristics are often complemented by velocity profiles in the cylinder and the valve gap, but the influence of valve and piston motion cannot be represented. In this work the intake stroke simulation was improved with a moving piston, although the valve remained motionless. A simple port geometry was chosen, since it was not the intention to optimize the port design for a particular engine. Measurements of three mean velocity components and the corresponding turbulence intensities around the intake valve showed complex flow patterns, including separation from the valve seat and sealing faces and back-flow into the intake port near the cylinder wall. Assuming quasi-steady flow conditions, i.e. a constant flow coefficient, flow velocities should scale with the instantaneous piston speed.

PDA-measurements of gasoline injection in a flow chamber and a simplified manifold-intake port configuration under constant air velocity have been performed. An acrylic glass model of an intake port without valves was mounted to a production manifold, equipped with a commercial plate-type gasoline injector. The PDA was set up in a 30° forward scatter arrangement to obtain dominant first order refracted light from the test gasoline droplets. The PDA-measurements could be synchronized with the injection cycle, thus achieving a simulated crank angle resolution in the engine. Measurements were made 70 mm downstream of the injection nozzle in both the chamber and the intake port experiments. Due to the geometry of the intake port and the near forward scatter set-up of the PDA, the probe volume could be traversed through the center of the port to obtain radial profiles of mean droplet sizes and velocities. For the profile measurements 5000 samples were taken at each point.

Advanced experimental techniques have been developed for application in the Volkswagen automotive wind tunnels. Such procedures are: laser-Doppler anemometry (LDA) for detailed flow-field measurements; laser-light-sheet technique for flow visualization; probe positioning by a robot; and frontal-area determination by a laser-reflection system. Experiences with these advanced experimental techniques are reported in some detail. Examples of test results are shown, and the different application areas as well as the usefulness of the various methods for the advancement of automotive aerodynamics are discussed.