EVALUATION OF DIFFERENT VELOCITY MEASUREMENT METHOD OF TURBINE TESTING

Abstract

The Hydropower is the outcome of utilization of energy of water using water turbines into useful mechanical power, and this (power) is converted into electricity with the help of electric generators. The amount of waterpower available depends upon the amount of water flowing through the turbine. Discharge is the volume of water per unit time flowing through any section in the system. Measuring discharge is a critical need in hydro power Plants. The flow measurement is vital parameter in estimating the relative efficiency of the plant. There are many flow measurement methods, but none gives satisfactory results.. The measurement of discharge in a hydroelectric plant can be performed- with desired accuracy only when the specific requirements of the choosen methods are satisfied. It is therefore in the interest of the parties involved to select the methods to be used for an acceptance test at an early stage in the design of the plant because later provision may be expensive or even impracticable. For the measurement of flow we either require flow meters, or may calculate the discharge by measuring velocity of flow through a known area [17,19]. A current meter is an instruments used to measure the velocity of flowing water or liquid. Current meters are being used since decades for velocity measurement in large pipe diameters apart from rivers and open channels. The principle of operation is based on the proportionality between the velocity of the water and the resulting angular velocity of the rotor. By placing a current meter at a point in a stream and counting the number of revolutions of the rotor during a measured interval of time, the velocity of water at that point is determined. The propeller current meter consists of a propeller mounted in a .bearing and a shaft. The fluid to be measured is passed through the current meter, causing the propeller to spin with a rotational speed proportional to the velocity of the flowing fluid. A device to measure the speed of the propeller is employed to make the actual flow measurement H-Horizontal Acoustic Doppler Current Profiler (H-ADCP) measures horizontal Velocity profile across a channel by its two horizontal acoustic beams. H-ADCP also measures water level by its up-looking acoustic beam. When using H-ADCP for flow monitoring, H-ADCP collects horizontal velocity profile data and water level data in real-time. Users need to select an appropriate method for discharge iii 'calculation using the velocity and water level data. Index-velocity method and Numerical method are two independent methods for calculating discharge. These two methods are based on different approaches and are independent. A major difference between the two Methods is that Index-velocity method requires rating or calibration, while numerical method does not. Another major difference is that Index-velocity method does not require H-ADCP profiling range cover the majority of channel cross-section. Therefore it can be used not only for small streams, but also for large rivers with its width much greater than H-ADCP profiling range. Numerical method in principle requires H-ADCP profiling range to cover the majority of channel cross-section. This Dissertation work involves Study of Two Velocity measurement method namely current meter & Acostic of Turbine Testing according to IEC-41 and the measurement of discharge using the two Instruments. The techniques applied in such measurements are of great significance for more efficient utilization of capital and the manpower involved. The main objectives of this Dissertation work are: (1) To Make Comparison of Velocity measurement by two methods using the propeller current meter & Horizontal acoustic Current profiler meter (H-ADCP) in an open-channel that involves the tasks such as: (a) Study of current meters. (b) Study of Velocity measurement method (Acoustic method & ultrasonic transit time Flow meter) according to IEC 41 Standard. (c) Study of national & international standards for open-channel Discharge Measurement. (d) Proper number & locations of current meters are worked out in channel Where discharge is to be measured. (2) Discharge calculation by Graphical method (improved scheme using Cubic Spline Interpolation, Cubic Interpolation & Power Law Extrapolation as per ISO-748. (3) Calculating discharge using Propeller Current meter and Horizontal Acoustic Doppler Current Profile meter in open channel at same time. Based on this discharge calculation a comparative study between these two methods.