Design-for-Additive-Manufacturing Approach for Support-Free, Pre-Assembled Micro Gas Turbines

This study presents a preliminary design approach for pre-assembled micro gas turbine engines intended for direct metal laser sintering, demonstrating the feasibility of additively manufacturing nested, self-supporting turbomachinery systems from Inconel718 in their operational configuration. The layout consists of two primary components: a monolithic rotor integrating compressor and turbine connected by a shaft serving as the fuel-driven journal, and a stationary casing incorporating turbomachinery stators, bearing housing, and a porous inert media combustor. Each component is designed to be self-supporting within powder bed fusion constraints and to facilitate the build of connected geometries above it, enabling the entire engine to be formed in a single uninterrupted process. Using a multidisciplinary gradient-based optimization framework, the radial compressor and mixed-flow turbine are parametrically designed to maximize mass flow and aerodynamic efficiency while maintaining structural integrity. The porous inert media combustor comprising of isotruss lattices achieves lean premixed combustion with minimal pressure drop. A fluidic conical hybrid bearing is considered with effective surface scaling, providing sufficient axial/radial load capacity at reduced power requirements. To ensure printability, pre-compensation optimization mitigates residual process stress-induced deformations, resulting in a pre-assembled architecture with manufacturing deviations of 70µm and surface roughness of 3µm for all critical surfaces. This work demonstrates a scalable, system-level AM approach that eliminates post-assembly and significantly simplifies the production of complex turbomachinery, offering a practical pathway toward integrated AM-driven propulsion systems.