A turbomachinery is presented to provide stable operation at fluid flow rates much lower than the design flow rate without introducing surge in the device. This is achieved by providing a diffuser with variable angle vanes. The vane angle at low flow rates is adjusted so as to minimize the diffuser loss of the exiting fluid stream from the impeller. Since the flow angle of the exit flow of the impeller is a function only of the non-dimensional flow rates, and does not depend on the flow angle at the inlet the impeller, therefore, the vane angles can be regulated to achieve a stable operation of the impeller without producing surge of the turbomachinery at flow rates lower than the design flow rate. To optimize the performance of the turbomachinery, in addition to the variable angle vanes, an inlet guide vane having variable vane angle is provided so that the turbomachinery can be operated at the required flow rate and head pressure. The concept is demonstrated in a turbomachinery provided with variable diffuser vanes and an inlet guide vane.