Experimental Investigation on a 3 kW Air Tesla Expander With High Speed Generator

Abstract Tesla bladeless turbomachines are recently being investigated due to many advantages such as its simple design and ease of manufacturing. If an efficient design is achieved, this will be a promising machine in the area of small-scale power generation and energy harvesting. This paper focuses on the experimental performance investigation of 3 kW (rated power) Tesla bladeless expander. The Tesla expander and electric generator are housed in a single casing making it first of its kind being tested with such configuration. The expander is fed with air and operated at high rotational speeds up to 40000 rpm. The test is carried out with different number of nozzles to understand its effect on the performance. Results show that the peak efficiency for two nozzles is better than one nozzle and four nozzle configurations for the same inlet pressure conditions. Experimental tests revealed that this turbine is most efficient Tesla turbine till now with air as a working fluid. Furthermore, one of the most important losses in Tesla turbomachines, nozzle loss, is experimentally characterized. Specific vibrational tests were carried out to obtain complete machine dynamical characterization. The vibrational response characterization of the turbine enabled us to recognize a disk mode family solicited by the air flow and to perform a proper machine maintenance and balancing aiming to reduce the energy of its operational vibration.