Investigation of flow in hydrodynamic converters: Interdependence of measurement and calculation

It is crucial to exactly know the flow field of the relevant machine if one wants to optimize the rating of turbo machinery. A reasonable supplement to experimental work by numerical examinations could be achieved based on the required understanding of flow. Modern measurement techniques permit the recording of unsteady flows and thus not only offer a detailed insight into the examined measurement planes, but also allow the review of complicated calculation procedures. The possibilities of numerical flow simulation which are increasing thanks to the further development of computers and calculation procedures permit not only the verification of experimental results, but also convey an insight into flow processes that are not accessible for measurement. Within the scope of this publication, the successful cooperation of measurement-related and numerical examinations of a turbo machine is documented by reference to a flow examination in a hydrodynamic torque converter. Pressure curves varying as a function of time were measured between the two impellers of the converter. A minitiaturized rapidly responsive pressure-sensitive probe developed to replace sensitive hot film probes forms the basis of the utilized measuring system. Parallel to this, a finite volume procedure has been developed which permits the calculation of incompressible, three-dimensional and unsteady flow in components that are moving relative to each other within a turbo machine. With the help of this procedure, the flow within the area of the pump and the turbine was simulated. Comparison of calculated torques with the values of a measured characteristic line as well as the juxtaposition of the calculated meridian and tip speeds to the measured values match each other well. Calculation and measurement in the level between pump and turbine prove, that the experimental analysis can be replaced by numerical examinations.