دانلود رایگان مقاله تاثیر سرعت چرخشی و قطر پروانه موتور بر عملکرد پمپ

Abstract

The major limitations of mini/micro hydropower schemes is the higher cost of small capacity hydro turbines. Also, it is very cumbersome, time consuming and expensive to develop the site specific turbines corresponding to local site conditions in mini/micro hydro range. In such plants, small centrifugal pumps can be used in turbine mode by running in the reverse direction. The efficiency of pump as turbines (PATs) is usually lower than the conventional hydro turbines; however, there may be substantial decrease in the capital cost of the plant. Hydropower plants usually runs at part load for several months in a year due to insufficient water availability for the power generation. The application range of PAT can be widened if its part load and/or maximum efficiency can be improved. In the present study, experimental investigations are carried out on centrifugal pump running in turbine mode to optimize its geometric and operational parameters e.g. impeller diameter and rotational speed. The experiments were performed in the wide range of rotational speeds varying from 900 to 1500 rpm with original (∅ 250 mm), 10% trimmed (∅ 225 mm) and 20% trimmed (∅ 200 mm) impellers. Impeller trimming led to improvement in efficiency at part load operating conditions. The performance of PAT was found better at the lower speeds than that at the rated speed. The effects of blade rounding were studied in all the cases and it led to 3–4% rise in efficiency at rated speed with the original impeller. The empirical correlation is also developed for prediction of efficiency in terms of impeller diameter and rotational speed in non-dimensional form.

6. Conclusions

In the present study, experimental investigations are carried out to improve the PAT performance by optimizing its geometric and operational parameters e.g. impeller diameter, and rotational speed. The experiments were performed in the wide range of rotational speeds varying from 900 to 1500 rpm with original (£ 250 mm), 10% trimmed (£ 225 mm) and 20% trimmed (£ 200 mm) impellers before and after blade rounding. As a conclusion, three options are recommended for the performance enhancement of PAT e.g. use of original impeller after blade rounding, running the PAT at 1100 rpm with blade rounded impeller and use of 10% trimmed-blade rounded impeller at 1100 rpm. The maximum efficiency was obtained as 76.93% with 10% trimmed impeller at 1100 rpm. The empirical correlation was developed between gBEP, D/Dr (range: 0.8–1) and N/Nr (range: 0.64–1.07) and applied for the present analysis. The predicted gBEP was found to be within ±10% range of the experimental results.