**ABSTRACT**

The Tesla turbine seems to offer several points of attractiveness when applied to low-power applications. Indeed, it is a simple, reliable, and low cost machine. The principle of operation of the turbine relies on the exchange of momentum due to the shear forces originated by the flow of the fluid through a tight gap among closely stacked disks. This turbine was firstly developed by Tesla at the beginning of the 20th century, but it did not stir up much attention due to the strong drive towards large centralized power plants; on the other hand, in recent years, as micro power generation gained attention on the energy market place, this original expander raised renewed interest. The mathematical model of the Tesla turbine rotor is revised in this paper, and adapted to real gas operation. The model is first validated by comparison with other assessed literature models. The optimal configuration of the rotor geometry is then investigated running a parametric analysis of the fundamental design parameters. High values of efficiency (isolated rotor) were obtained for the optimal configuration of the turbine, which appears interesting for small-scale power generation. The rotor efficiency depends on the configuration of the disks, particularly on the gap and on the outlet diameter, which determines largely the kinetic energy at discharge.

**KEYWORDS**

PAPER SUBMITTED: 2016-06-01

PAPER REVISED: 2018-03-09

PAPER ACCEPTED: 2018-05-13

PUBLISHED ONLINE: 2018-06-03

- Tesla, N., Turbine, U.S. Patent No. 1 061 206, (1913).
- Armstrong, J.H., An Investigation of the Performance of a Modified Tesla Turbine, M.S. Thesis, Georgia Institute of Technology, (1952).
- Rice, W., An analytical and experimental investigation of multiple-disk turbines, ASME Journal of Engineering for Power, 87, (1965), 1, pp. 29-36.
- Hoya, G.P. and Guha, A., The design of a test rig and study of the performance and efficiency of a Tesla disc turbine, Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy, (2009), 223, pp. 451-465.
- Guha, A., and Smiley, B., Experiment and analysis for an improved design of the inlet and nozzle in Tesla disc turbines, Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy, (2009), 224, pp. 261-277.
- Neckel A.L., and Godinho, M., Influence of geometry on the efficiency of convergent-divergent nozzles applied to Tesla turbines, Experimental Thermal and Fluid Science, 62, (2015), pp. 131-140.
- Carey, V.P., Assessment of Tesla Turbine Performance for Small Scale Rankine Combined Heat and Power Systems, Journal of Eng. for Gas Turbines and Power, (2010), 132.
- Carey, V.P., Computational/Theoretical Modeling of Flow Physics and Transport in Disk Rotor Drag Turbine Expanders for Green Energy Conversion Technologies, Proceedings of the ASME 2010 International Mechanical Engineering Congress and Exposition, (2010), 11, pp. 31-38.
- Guha, A., and Sengupta S., The fluid dynamics of the rotating flow in a Tesla disc turbine, European Journal of Mechanics B/Fluids, 37, (2013), pp. 112-123.
- Sengupta, S., and Guha, A., A theory of Tesla disc turbines, Proceedings of the Institution of Mechanical Engineers, Part A; Journal of Power and Energy, (2012).
- Lemma, E., Deam, R.T., Toncich, D., Collins, R., Characterisation of a small viscous flow turbine, Experimental Thermal and Fluid Science, 33, (2008), pp. 96-105.
- Sengupta, S. and Guha A., Analytical and computational solutions for three-dimensional flow-field and relative pathlines for the rotating flow in a Tesla disc turbine, Computers & Fluids, (2013), 88, pp. 344-353.
- Romanin, V.D., Krishnan, V.G., Carey, V.P., Maharbiz, M.M., Experimental and Analytical study of Sub-Watt Scale Tesla Turbine Performance, in: Proceedings of the ASME 2012 International Mechanical Engineering Congress & Exposition, (2012), 7, pp. 1005-1014.
- Krishnan, V.G., Romanin, V.D., Carey, V.P., Maharbiz, M.M., Design and scaling of microscale Tesla turbines, Journal of Micromechanics and Microengineering, (2013), 23, pp. 1-12.
- Guha, A., and Sengupta S., Similitude and scaling laws for the rotating flow between concentric discs, Proceedings of the Institution of Mechanical Engineers, Part A; Journal of Power and Energy, (2014), 28, pp. 429-439.
- Guha, A., and Sengupta S., The fluid dynamics of work transfer in the non-uniform viscous rotating flow within a Tesla disc turbomachine, Physics of Fluids, (2014), 26.
- Sengupta, S. and Guha A., Flow of a nanofluid in the microspacing within co-rotating discs of a Tesla turbine, Applied Mathematical Modelling, 40, (2016), 1, pp. 485-499.
- Klein, S.A. and Nellis, G.F., Mastering EES, f-Chart software, (2012).
- Dixon, S., L., Fluid Mechanics and Thermodynamics of Turbomachinery, 5th ed., Pergamon Press, (2005).