Performance and market evaluation of the bladeless turbine

Abstract

The three-inch diameter prototype bladeless turbine was tested with air over a range of inlet pressures from 20 to 100 psia and speeds of 10, 20, 30 and 40 thousand rpm. The peak efficiency of 22.5 percent was recorded at a pressure of 98 psia and a speed of 40,000 rpm. Efficiency increased slightly with speed and inlet pressure over the range of test conditions. The test program was somewhat hindered by mechanical failures. The turbine bearings in particular were unreliable, with two instances of outright failure and numerous cases of erratic performance. A model of the bladeless turbine was developed to aid in interpreting the experimental results. A macroscopic approach, incorporating several favorable assumptions, was taken to place a reasonable upper bound on turbine efficiency. The model analytically examines the flow through the air inlet nozzles and the interaction between the fluid jet and the turbine blades. The analysis indicates that the maximum possible efficiency of a tangential flow turbine with straight axial blades is 50 percent. This is a direct consequence of turning the fluid only 90 degrees relative to the turbine blade. The adoption of the bladeless turbine as the expander in an Organic Rankine Cycle (ORC)more » will depend to a great extent on the efficiency of the turbine. The market potential for ORC technology will also impact the adoption of the bladeless turbine. Other expanders have demonstrated efficiencies of 60 to 80% in ORC systems. The Gamell turbine had a peak test efficiency of 22.5% and a maximum theoretical efficiency of 50%. Costs of the turbine are highly uncertain, relying to a great extent on cost reductions achieved through quantity production and through learning.« less