The influence of radial positioning accuracy on LDA velocity measurements in a valve gap

Abstract

In this paper, the effect of radial positioning of the measurement plane on the measured velocity profiles in a stationary valve gap under unsteady flow conditions is discussed for three velocity components. As shown, positioning of the measurement plane significantly influences all measured velocity component distributions across the valve gap, as well as the temporal velocity behaviour, particularly in the upper part of the valve gap where a high radial gradient of velocity was observed. This effect relates to the azimuthal position of the measurement point around the valve axis. A generalization of the LDA measurement control volume positioning problem and practical considerations are also discussed in the paper. In the case of high-velocity gradients in areas remote from the wall, minimization of the LDA measuring control volume dimensions is not sufficient, and several well-defined positions of the measurement plane must be chosen. This choice has to take into account the object geometry, flow conditions and the methodology.

Potential of Porous-Media Combustion Technology as Applied to Internal Combustion Engines

“…For air flow processes, three groups of parameters have to be considered: volumetric efficiency, which represents the mass of air supplied to the cylinder and pumping losses, flow structure in the cylinder which represents a macrostructure of the in-cylinder flow field (e.g., swirl, tumble, tipped), and turbulence level and its scales which represents a microstructure of the in-cylinder Journal of Thermodynamics flow field. An intake valve timing and lift, geometry of the port/valve assembly, and valve location in the engine head significantly influence the flow properties of the intake system [16][17][18][19][20][21]. Especially attractive are throttle-free systems with variable valve timing and variable valve lift.…”