Development of the pressure-time method for low-head machines

Many hydropower plants were built several decades ago and now require major refurbishments. The efficiency of the turbine is an important factor to verify both before and after a turbine upgrade. In most methods used for this purpose, the flow rate must be determined.

The pressure-time method is one such efficiency measurement method and is relatively inexpensive and simple to apply compared to other methods. In this method, the flow rate is estimated by integrating the measured differential pressure and pressure loss between two cross-sections in a water system during the deceleration of the fluid mass, when the flow is throttled using a valve or guide vanes. The pressure-time method has limitations specified in the IEC-60041 standard, which makes it difficult to apply to turbines with low heads due to the short water passages where the flow field develops.

The main focus of this project is to improve the accuracy of the pressure-time method and extend its applicability to low-head turbines. Numerical simulations and an experimental study are being conducted. A laboratory setup has been designed and built to test the pressure-time method. The method is being tested in cases with pipes of variable cross-section, bends, and shorter lengths than those recommended by IEC-60041.