Experimental and numerical investigation of an innovative non-combustion impulse gas turbine for micro-scale electricity generation

Fulfilling electricity demand in a remote platform has been a great challenge for oil and gas industry. With only pressurized gas line available, the choice of technology that can be implemented is limited; one of it is impulse gas turbine. At the moment, no studies investigating the performance of a compact impulse gas turbine which utilizes pressurized gas line has been reported, hindering the wide adoption of this technology. This study is therefore conducted with the main objective to investigate the performance of small scale impulse gas turbine for electricity generation by using computational fluid dynamics (CFD) approach in tandem with experimental validation. Three-dimensional computational model for the turbine is developed. Concurrently, an experimental set-up, consisting of micro impulse gas turbine, electric generator, flow loop and control system, is prepared to validate the model prediction. The effect of several key parameters, such as working fluid, rotational speed, mass flow rate and input pressure are evaluated to obtain operating envelope of the turbine. Overall, good agreement is achieved between numerical model prediction and experimental measured value. On the effect of working fluid, the results indicate that the impulse gas turbine driven by natural gas at 69 bar produce maximum power output of 1743.81 W at lower speed of 4500 RPM while maximum power of 1084.04 W can be achieved when driven by compressed air at 19 bar at rotational speed of 7000 RPM. In addition, a complete operating envelope for the turbine operating with either compressed air or natural gas has been developed. Furthermore, the effect of distance between nozzle outlet and turbine blade has been evaluated for which the optimum distance within studied range is obtained: 49.62 mm for one with compressed air and 54.62 mm for one with natural gas. The result from this study is expected to serve as a guideline in designing micro impulse gas turbine for electricity generation especially for remote offshore platform.