A Bladeless Turbocompressor Concept: Shear Driven Gas Compression With Deformable Structures: Part 1 — Experimental Proof of Concept
Authors: Heshmat Hooshang , Walton James F. 
Published: September 2017

A novel concept for shear flow driven gas compression that could enable next generation turbomachinery has been designed and experimentally demonstrated. In order to achieve this, a prototype proof-of-concept compliant foil-based bladeless turbo-compressor device was developed and used to conduct a gas compression parametric study. The principle underpinning the operation of this device is the conversion of shaft power into hydrodynamically generated pressure that occurs in the shear flow between a smooth rotating disk and a compliant surface. The present compliant foil bladeless turbocompressor (CFBT) is an evolutionary derivative of self-acting compliant foil bearings and seals, which operate in the hydrodynamic regime. Thus, as in these devices, the process of compression induced by shear flow is dominated by the balance between pressure and viscous forces, which are in turn enhanced and controlled by tribological effects arising between the shear layer and the deformable geometry of the compliant surface. The single shaft foil bearing based proof-of-concept CFBT presented is powered by a permanent magnet motor capable of reaching speeds up 360,000 rpm, and consists of two independent compression stages mounted on opposite ends of the shaft. Each compression stage consists of a smooth disk with the effective corresponding counterface of radii 7.6 mm < r < 14.1 mm, with one of each disk’s surfaces facing a four-pad compliant foil surface mounted on the housing. The nominal initial gap separating each of the disks from their corresponding compliant foils is nominally h0 = 0.025 mm and 0.4 mm, respectively. In this configuration, air is entrained from opposite directions through axial intakes and turned 90° as it undergoes shear between the rotating disk and the compliant foil pads of each of the stages, inducing a net radially-oriented outward flow, which is then collected in the quasi-volute of the respective stage. The system is heavily instrumented, with each of the quasi-volutes fitted with thermocouples, pressure probes and a flow meter. An experimental parametric study was performed compressing standard temperature and pressure air for varying speeds up to 360,000 rpm. Performance curves reporting flow vs. pressure as well as compression power requirements vs. speed were obtained for the individual compression stages. The experimental results on the proof of concept turbocompressor are analyzed in the context of the theoretical foundations presented in a companion paper (Heshmat and Cordova, 2017), showing excellent correlation. It is anticipated that due to its simple bladeless geometry, application of this novel technology in conjunction with foil bearings will result in low cost, ultra-high speed, high efficiency, high specific power, miniaturized turbocompressors and high power density oil-free and maintenance-free machines, such as compressors, meso-scale gas turbines, or turbogenerators. Attractive applications for this technology range from military micro-UAV propulsion and portable power systems, to domestic combined heat and power (CHP) turboalternators and medical devices such as portable oxygen concentrators and CPAP (Continuous Positive Air Pressure) machines.