Development of Flow Measuring Instrumentation for Turbo Machines - Design Aspects for the AM Based Manufacturing

摘要

Measurements with probes or rakes in turbo machines always create the dilemma between the demand for highly accurate results and a non-avoidable disturbance of the flow field by the probes and rakes themselves. Blockage effects might influence the flow characteristic in the stages and interactions with airfoil leading and trailing edges can result in significant angle deviations. These issues will affect the accuracy and value of the measuring results. Especially measurements in turbomachines with small flow passages and axial gaps between rotors and stators demand small probe sizes in order to minimize these effects. However, the potential for a reduction in size is quite limited because of the necessary channels to be implemented for the connection of the pressure taps and temperature measuring devices with the regarding scanners and transducers. With increasing number of measuring devices the demand for space for the transmission lines increases. In order to avoid long measuring times the channels should have a sufficient diameter so that the resistance inside remains low. All these issues result in a minimum size of the probe heads and rake stems.