Session: 18-07 Advanced Turbomachinery Manufacturing - Design, Materials & Processes

Paper Number: 83489

83489 - Additive Manufacturing of Centrifugal Impellers for Solid Oxide Fuel Cell Anode Offgas Recycle Blowers 

Recent advances have brought solid oxide fuel cell (SOFC) technology closer to viability for grid and transportation deployment. However, typical SOFC process gas operating conditions present durability challenges to balance of plant (BOP) subsystems and components, which result in costly design customization and/or the use of expensive materials manufacture. Such is the case of centrifugal anode gas recycle blowers (ARCBs) that directly handle SOFC anode exhaust, which is typically hot (>100^OC) and consists of mixtures of water vapor, hydrogen, and other potentially corrosive/reactive gases. As a result, centrifugal blowers that are specifically designed for SOFC service present a series of stringent design and manufacturing requirements, for example the use oil free bearings, motor encapsulation, and extensive use of nickel base (corrosion resistant) superalloys in the fabrication of their aerodynamic and gas path components. In particular, the impeller of a high speed centrifugal ARCB operates in extremely challenging mechanical stress and temperature conditions, and therefore is one of the highest cost parts of the system. This is due to the three factors: 1) high strength nickel base superalloys, such as Inconel 718 or Rene 41, are difficult to machine and cast, 2) high aerodynamic efficiency requires complex three-dimensional geometry, and 3) fuel cell BOP component prototype or early production runs (low count) cannot take full advantage of economies of scales for cost control. For these reasons, the incorporation of innovative manufacturing processes, such as additive manufacturing (AM) or 3D printing, is needed to reduce the cost of centrifugal impellers and other ARCB parts, and in general, of the overall BOP of SOFCs.

Currently, most parts fabricated by additive manufacturing are used for static, non-rotating components, with relatively few instances of experimental applications in small high speed/temperature turbomachinery. This paper presents the results of the early stages of an effort to produce low cost Inconel 718 centrifugal impellers by the laser powder bed fusion (LPBF) additive manufacturing method. During the development of this project, the authors identified the LPBF method as capable of providing the geometric precision necessary to produce impellers comparable to those produced by traditional methods like 5-axis CNC, but also the design flexibility to achieve parts with advanced geometries for higher aerodynamic efficiency. The paper includes: 1) A discussion of the potential for aerodynamic performance gains derived from eliminating traditional tooling constraints and from the general design flexibility provided by 3D printing, 2) Specific examples of reductions of cost, material waste, and manufacturing time that are achievable from the 3D printing, 3) Results of different iterations of the AM process, including images detailing the process improvement from early trials to final impellers, and 4) Comparisons of the impellers produced by AM methods to their traditionally manufactured counterparts.

In addition to demonstrating a reduction of manufacturing costs and complex rotating part manufacturability, a key driver of this effort is to increase confidence that AM methods can yield safe/reliable high speed rotating components. Successful demonstration of these methods with impellers would pave the way for their use not only in fabrication of other ARCBs parts like housings and other SOFC BOP components, but also for use in more general applications like microturbines, turbochargers, and other general centrifugal turbomachinery.

Presenting Author: Jose Luis Cordova Mohawk Innovative Technology, Inc.

Presenting Author Biography: Jos&#233; Luis C&#243;rdova is Vice President of Engineering at Mohawk Innovative Technology, Inc. (MITI), where he heads a team that analyzes and designs turbomachinery and other power conversion and energy generation systems. He received his degree in Mechanical Electrical Engineering from the Universidad Nacional Aut&#243;noma de M&#233;xico, and both MS and PhD in Mechanical Engineering Science from the University of California at Berkeley. He has a background in mechanical engineering science that spans multiple fields, including combustion, fluid mechanics, heat transfer, thermodynamics, and applied engineering mathematics.<br/>During his tenure at MITI, Dr. C&#243;rdova has collaborated on the design of multiple MITI engines, including gas turbine engines, turbogenerators, blowers, compressors, and turbochargers. His current focus is the development of blowers for solid oxide fuel cell power plants and supercritical CO2 turbomachinery for green energy, and he is leading MITI’s incorporation of 3D printing technology into its turbomachinery integration workflow.

Authors:

Jose Luis Cordova Mohawk Innovative Technology, Inc.