Matthew B. Parkinson and Dr. Jordan J. Cox, Mechanical Engineering
The design, manufacture, and testing of turbines involves many aspects of engineering: fluid mechanics, computer-aided design, computer-aided manufacturing, instrumentation, heat transfer, and optimitization. This project encapsulates these and provides for rapid design, manufacture, and testing of a prototype turbine wheel (figure 1). Although the models are simplified and do not address countless design considerations, they do provide a feel for the many issues encountered.
The encapsulation of the turbine is achieved through the use of a product “template”—a generic representation of all the formulae, geometry, processes, and documentation that represent a part. In this case, it is the turbine wheel that is defined by a set of parameters which, when taken as a whole, define all aspects of the geometry and performance. These parameters are used to create the generic, parametric, models within Pro/ENGINEER (a geometric solid modeler), Pro/MANUFACTURING (an NC machining environment), and OptdesX (an optimization package). These generic models can then be instantiated to generate a specific design.
While many of the parameters must remain constant to accommodate the shroud and platform (figure 2), many are variables which the designer may select and change. The template user is presented with a graphical user interface or “gui” that manages these parameters, restricts the values they may hold, and predicts the design’s performance (figure 3) using basic flow equations. Since OptdesX serves as the gui, the template also provides for the optimization of the turbine to specific performance standards (maximizing output rpm, for example). Through optimization or other design techniques, the parameters defining the turbine wheel are all assigned values and a specific design is created.
Once values are assigned to all the parameters, the design is passed to Pro/E where the solid model and NC toolpaths are updated automatically. The toolpaths may then be postprocessed and used to mill a new turbine wheel. The prototype turbine is then easily mounted and tested with the scroll and platform. The whole process, from design inception to testing of the part, may be accomplished in less than an hour (a time savings of days or weeks).
The Mechanical Engineering Department will use the template in its Fall 1996 Elementary Instrumentation course, finally providing a “hands on” opportunity to the student, who will design his own product (the turbine wheel) and the method of instrumentation to test it. It will also be used to demonstrate the feasibility of the template concept to potential industry partners. Although several designs have already been created, manufactured, and tested up to 15,000 rpm, improvements to the template will continue to be made as its use is expanded.
