Session: 19-03 Radial High Speed Compressors & Turbines

Paper Number: 101192

101192 - Performance Investigation of Stator-Less and Blade-Less Radial Expander 

Interests in small-scale turbomachinery are gaining momentum, particularly around waste heat recovery using Organic Rankine Cycle (ORC), energy harvesting, pico-hydro, refrigeration and heat pumps and small-scale power generation. These applications demand to have economical, simple construction, and reasonable efficient machines. The performance of bladed turbomachine at a small scale is poor mainly due to viscous losses. In some cases, like ORC, it requires a lubrication system which makes it complex and costly. Bladeless or Tesla turbomachinery is seen as one of the solutions for these applications due to its simple construction and cost-effectiveness. However, the experimental efficiency of the bladeless turbines/compressors is found lower, < 40%. In the literature, one of the main reasons for its lower performance is identified in the losses in stator and stator-rotor interaction.

In this article, the performance of a bladeless turbine is investigated using a vaneless volute configuration which makes the turbine stator-less (vaneless volute) and bladeless (vaneless rotor). The vaneless volute accelerates the working fluid to the leading edge of the rotor and distributes the fluid uniformly around the periphery of the rotor. These conditions in volute are achieved with minimum loss in the stagnation pressure. In this study, a volute design methodology is presented for the bladeless rotor. A steady, incompressible 3D numerical analysis is carried out using commercial software Ansys Fluent with air as a working fluid. The 3D model simulated consists of a volute and rotor disk for one gap between disks. The simulation is performed for a wide range of inlet pressures and rotational speeds. At the design condition of the turbine i.e., 30000 rpm, 10.6 g/s and 124 W power, 65.4% total to static efficiency is obtained, which is highest recorded 3D numerical efficiency for bladeless turbines till now, considering the whole stator-rotor control volume. The improvement in the performance with volute is discussed in comparison with nozzle configuration. The overall turbine performance expected by the actual turbine is estimated based on empirical ventilation losses and mechanical losses from past air bladeless turbine models and prototypes.

In the second part of the article, turbine components, assembly and test set-up are discussed. Experimental performance is carried out in the design cases simulated in the 3D simulation. The overall turbine performance from 3D numerical simulation with ventilation and mechanical losses is compared with experimental results. It is found that the improvement in the turbine performance is mainly due to the reduced losses between stator and rotor interaction and uniform distribution of the flow around the rotor periphery. Moreover, due to the full admission of fluid into the rotor disk pack, the disk tip generates positive torque, ultimately adding to the overall turbine power, unlike in the case of discrete nozzles where there is viscous friction between the disk tip and the casing. This work demonstrates that the proposed stator-less/volute configuration provides an efficient way for bladeless or Tesla turbines, particularly for low-head applications.

Presenting Author: Avinash Renuke Malardalen University

Presenting Author Biography: Avinash Renuke has completed, PhD, from University of Genoa, Italy. He is currently working as a Post-Doc Researcher at Malardalen University, Sweden. He did his masters studies from the Indian Institute of Technology, Bombay in Thermal and Fluids engineering. He has worked in General Electric ( Oil and Gas - Now Baker Hughes) for more than 4.5 years as compressor design and NPI engineer. His overarching interests lies in energy efficiency and sustainable energy solutions in turbo-machinery domain or likewise.

Authors:

Avinash Renuke Malardalen University
Alberto Traverso University of Genoa
Federico Reggio University of Genoa
Matteo Pascenti SIT Technologies srl
Paolo Silvestri University of Genoa