| Author | Chaiyaphol Kaewprakaisaengkul |
| Call Number | AIT Diss. no.AE-96-04 |
| Subject(s) | Irrigation pumps
|
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Engineering, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. AE-96-04 |
| Abstract | More than one million irrigation pumps are now being used by Thai framers. Most of them are portable types. The pumping requirement is mostly low head and high discharge, since these pumps are used for rice cultivation with water from natural resources i.e. rivers, lakes, and canals, Three main types of Thai-made pumps in general use are axial flow, mixed flow and radian flow. However, performance characteristics for any of these pumps were not available, since they were never tested in detail by the manufacturers of government agencies or universities. Therefore, this study was conducted to evaluate the performance of different types of Thai-made low head and high discharge pumps. A standard test rig was designed and built for pump testing at the Asian Institute of Technology. Initial evaluation of the performance and comparison of the Thai-made pumps were conducted. It was also observed that the useful life of existing pumps is very low due to corrosion of pump parts submerged in the water. One possibility ot extend the service life of these pumps is by coating submerged parts with porcelain enamel. Results of the tests at total static head of 1.0 m showed that the axial flow pump had an maximum efficiency of 16.8% when it was running at 2300 rpm with a discharge rate of 25.6 1/s and shaft power input of 2.54 kW. The mixed flow pump had maximum efficiency of 56% when operated at 1000 rpm, a discharge of 51.1 1/s and power input of 2.37 kw. The radial flow pump had a maximum efficiency of 13.36% at 1150 rpm with a discharge of 20.1 1/s and power in of 2.0 kW. Different power losses of the three pumps were measured and compared. The mechanical power loss was found to be the drive shaft. Use of long drive shafts with insufficient stiffness or use of bent shafts caused mechanical vibration and finally resulted in the breakdown of support bearings and drive shaft. Shaft misalignment was partly due to the use of too many supporting bearings. Mechanical power loss of the three pumps namely external, internal and semi-immersed drive shaft had the highest mechanical power loss of 52.4% and the external drive shaft had the lowest mechanical power loss of 16.5% A new externa. drive shaft was designed in order to reduce the mechanical power loss. Proper alignment of the shaft was obtained by separating the drive shaft into two parts which were connected by flexible coupling. The shaft was carefully machined and the maximum static deflection of the shaft was measured to ensure that the shaft rotated without torsional vibration. The impeller, diffusion vanes and pump casing of the Thai-made axial flow, mixed flow and radial flow pumps were modified in order to improve the discharge. A new 3-blade axial flow impeller with new diffusion vanes, vane cascades and airfoil profiles were developed. The original radial flow impeller and volute casing was designed and fabricated. The mixed flow pump casing was also modified and fabricated for use with the new external drive shaft. Performance characteristics of the axial flow and mixed flow pumps with enamel-coating on pump casings and diffusion vanes were compared with the non-coated ones. The three new pumps with the newly designed external drive were tested at five total static heads of 1.0, 1.5, 2, 2.5, and 3 m. The empirical equations of the characteristic curves of all the pumps tested agreed well with the theoretical equations derived from the affinity law. Results indicated a three fold improvement in efficiency of the axial flow pumps from 16.8% to 59.2% due to modifications The discharge rate was increased 2.25 times from 25.6 1/s to 50.7 1/s while the power input decreased from 2.54 to 2.385 kW. From the comparison of the performance, the efficiency of the pump with enamel coated casing was 2 to 5% higher than the non-coated pump due to less power requirement. The mixed flow pump also showed the same improvement in the pump performance as the pump discharge was slightly increased from 51.1 to 52.2 1/s the total head was increased by 8% from 2.64 to 2.86 m and there was no difference in power input. This resulted in an improvement of efficiency from 56% to 61.6%. The power input of the non-coated pump was slightly higher than the enamel coated pump, this resulted in the increase of the efficiency of the enamel coated pump by 2 to 7%. Enamel coating of the submerged part of the pump will help to reduce corrosion. At 1200 rpm, the radial flow pump with a newly designed impeller and volute casing showed an increase in the pump efficiency from 13.2 % to 30.25% which was twice the efficiency of the original radial flow pump. The discharge rate increased from 21.35 to 29.69 1/s the total head was increased from 1.43 to 1.82 m while the power input was reduced from 2.3 to 1.7 kW. This work indicates the large improvements in performance of Thai-made irrigation pumps which can be obtained by rigorous research and development. It is believed that locally made irrigation pumps other Asian countries can be improved in a similar fashion. |
| Year | 1996 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. AE-96-04 |
| Type | Dissertation |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Food, Agriculture and Natural Resources (Former title: Department of Food Agriculture, and BioResources (DFAB)) |
| Academic Program/FoS | Agricultural and Food Engineering (AE) |
| Chairperson(s) | Gee-Clough, D.; |
| Examination Committee(s) | Singh, Gajendra;Gupta, C.P.;Salokhe, V.M.;Tawatchai Tingsanchali; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 1996 |