No abstract

The commercially available unmanned aerial vehicles are not good enough for search and rescue flight at high altitudes. This is because as the altitude increases, the density of air decreases which affects the thrust generation of the UAV. The objective of this research work is to design thrust optimized blade for an altitude range of 3,000–5,000 m with a density of air 0.7364 kg/m3, respectively, and perform thrust analysis. The property of aluminum alloy 1,060 being lightweight is chosen for designing and testing of blade. The blade element theory-based design and analysis code was developed, and user-friendly aerodynamic inputs were used to obtain the desired outputs. The geometry designed for an altitude range of 3,000-5,000 m faced the total stress of 6.0 MPa which was at 70% of the blade span. This stress is within the limit of yield strength of the aluminum alloy, 28 MPa. The modal analysis shows the first natural frequency occurs at around 12,000 RPM which is safe for operating the blade at 0-5,000 RPM. Experimental analysis of the blade gave a thrust of 0.92 N at 2,697 RPM at 1,400 m. The analytical solution for thrust with the same conditions was 1.7 N with 85.6% efficiency. The validation of experimental results has been done by the CFD analysis. The CFD analysis was performed in ANSYS CFX which gave a thrust value of 2.27 N for the same boundary conditions. Thus, the blade designed for high altitude SAR UAV is structurally safe to operate in 0-5,000 RPM range, and its use in search missions could save many lives in the Himalayas.

Hydropower is considered as one of the most economical and stable base energy source compared with other sources of energy of Nepal. Researches coherent to this field are not new but yet it is not sufficient, lots of tiles have to be kept for better understanding of hydropower effecting elements. Sand is the most affecting element that damages the turbine blades, so research on relation of sand and turbine is most. This research is done to find out the impact of sediment on turbine material. Modi River sediment at eight different stations has been taken as sample and its erosion rate in turbine blade sample specimen has been accounted in this study. Rotating disc apparatus has been utilized to find out the total impact of sand on turbine material. Four same kind of test turbine material is used on single rotating disc all at a time at same condition to define sand impact. Thirty gram (gm) of sediment mixed with three liters of water is used to strike sample pieces for five minutes. Two different tests of sediment samples of 8 different locations were studied. After all the test it is observed that the first test sand sample of location 1 and turbine material 1 has the highest impact with a weight loss of 7.764 mg and least impact in sand sample location 1 and sand sample 3 with a weight loss of 3.5 mg. Average weight loss of turbine material in first location is 5.929 mg which is the greatest impact and 4.0083 at eight locations which is the least. Relating to turbine material first rotating disc turbine specimen P0A has been affected highly with weight loss of 9.289 mg and less eroded on P5A rotating turbine specimen with weight loss of 1.2 mg.

Siltation problem in Nepal is major and challenging in hydropower development. It degrades the reservoir capacity and hydraulic turbines' efficiency. Many researches have been carried out in this field and have proven sand as major substance that erodes the turbine material, but only few researches have accounted every parameters of sand on degradation of hydraulic turbines. This paper accounts size of sediments important parameter that has direct impact on turbine material. Sediment size impact has been studied firstly by characterizing size into six layered using sieve analyzer and testing its impact using high velocity test rig at Kathmandu University. Sand samples from 20 different stations of Roshi river were collected and tested on turbine material 18Cr4Ni. It found that greater micron sizes of sediments have great impact was than relatively smaller ones. It is depicted that 300-400 micron size sediment, have highest impact with weight loss of 0.022 milligram, 212-300 micron size has 0.013 milligram weight loss, 90-212 micron size has 0.012 and below 90 micron sizes have 0.0075 milligram of weight loss.