Radial infow turbines cover huge ranges of power, mass fow rates and rotational speeds, from the large Francis turbines used in hydroelectric power generation to the tiny closed cycle gas turbines used for space power generation (Dixon, 2005). It is this extensive range of applications which makes the procient design and manufacture of these turbines a key eld in engineering.
Typical design methodologies for these turbines often require extensive prior empirical knowledge and as a result, the designer must have considerable input, ranging from the appropriate choice of operating conditions to geometric parameters and manufacturing considerations. An improved design methodology for radial inflow turbines is one presented by Ventura (2012), the Aerodynamic Design and Performance Estimation of Radial Infow Turbines Model (ADPERITM), an automated process which considers the whole operating spectrum of rotational speeds and non-dimensional coeffcients.
As with design methods, current forms of manufacture can be time consuming and costly. Tur-bomachinery are typically manufactured using CNC machines, after the development of tool paths using CAM software, a step that generally requires an experienced operator (Heynick and Stotz, 2010). An alternative to this method of manufacturing is rapid prototyping (RP), an additive rather than subtractive manufacturing process. The advantage of RP over the CAD/CAM/CNC method is the process between CAD and RP is largely automatic and thus less expensive and time consuming (Heynick and Stotz, 2010).
This thesis explores these modern methods of design and manufacture by developing a radial infow turbine with an electrical capacity of 10 kWe and creating an accompanying rapid prototype manufacturing plan. The turbine is designed to operate as part of an organic Rankine cycle between the temperatures of 30 oC and 150 oC and utilises R245FA as the working fluid.
Using the aforementioned methods, the preliminary design of a radial infow turbine with a total- to-static eciency of 86.7% was developed, operating within an organic Rankine cycle of 8.53% efficiency. By using RITAL and AxCent, turbomachinery software packages from Concepts NREC, the three-dimensional turbine was developed. CFD simulations were subsequently performed using Pushbutton CFD, the results of which were consistent with values calculated using ADPERITM and as such the design was considered to be validated.
Research determined that direct metal laser sintering (DMLS) was an appropriate method of rapid prototyping to manufacture a functional turbine. By using ADPERITM in conjunction with other analysis it was determined that any of the powdered metals available for DMLS were satisfactory choices for the turbine material. Considering all factors including cost and availability, DirectMetal 20, a bronze alloy, was selected as the optimum choice for the turbine. In addition to the material, the selection of suitable bearings and seals was made.