Rapid Experimentation in Complex Internal Flow Passages Using SLA and MRV

Designing complex internal cooling passages is extremely difficult without detailed information about the flow behavior due to the presence of separated flow zones and strong secondary flows. This paper describes a new approach to designing internal flow passages called Rapid Iterative Design Using Experimentation (RIDUE). RIDUE utilizes rapid prototyping (RP) manufacturing to quickly build an accurate model of a complex internal flow passage and magnetic resonance velocimetry (MRV) to measure the full three dimensional velocity field. Because both techniques offer very fast turnaround, it is feasible to conduct iterative design with a cycle time of 1–2 days. RIDUE is demonstrated using a generic turbine blade internal cooling passage with four serpentine channels. Two channels have rectangular cross-section and two are square. In each channel, two of the four walls have ribs (also called turbulators) angled at 45 degrees to the main flow direction. Two models based on the generic geometry are studied, each with different turbulator cross-sections, one square and one rounded. Both models were built using a stereo lithography apparatus. MRV provided three-component velocity vectors for flow at a Reynolds number of 10,000 based on the hydraulic diameter of the first passage. Sample vector fields are presented to illustrate the detail with which the flow can be investigated. Although little difference is seen in the flows between the two models, it is demonstrated that through its use of RP processes and the MRV measurement technique, RIDUE is a viable technique for modern internal passage design.