Experimental investigation on the effect of axial gap on performance and unsteady pressure pulsations of low head axial flow hydraulic turbine

The stable operation of axial flow turbines (AFTs) in the energy conversion process directly affects their safety and performance. Because of its unstable pressure features, a dynamic analysis of its internal flow characteristics is required. To analyze, evaluate, and compare the pressure variation within the turbine under the base gap ((sic) - 0.05D) and different axial gaps (sic) of 0.09D, 0.14D, and 0.18D, a reliable measurement approach is required. Pressure sensors were installed on the flow domain of the AFT to measure dynamic pressure pulsation under various (sic) and running flow conditions. Based on the experimental result, a 28% and 2.8% increase in turbine efficiency was recorded when the (sic) was increased from 0.05D to 0.09D at 0.8Q(d) (design flow rate) and 1.0Q(d), respectively. Further analysis of the frequency spectra reveals different unsteadiness in the flow structures due to changes in (sic) which resulted in various excitation signals. A decrease in the (sic) leads to an increase in pressure pulsation intensity. Consequently, AFT with (sic) of 0.09D was recommended since it provides maximum efficiency with fewer pulses compared with (sic) = 0.05D, where the vibrations are at peak value. The findings above will aid in the optimum use of energy resources since energy generated from AFT is clean and free of pollution and can lead to a sustainable energy generation process.