A reliable operation and reducing the power consumption of the feed pumps of the ORC systems are highly important as the feed pump is one of the main components affecting the ORC power plant operating pressures, controllability, and the cycle net power output. Especially in small-scale and high -temperature ORC systems, the design of an efficient feed pump can be challenging because the required pressure increase over the pump is high and on the other hand, the working fluid flow rates are small. In this paper, the design and experimental investigation on the operation of a small-scale and high pressure ratio ORC feed pump are presented and analyzed. The investigated feed pump is of partial emission type and it is connected to a single shaft with a high-speed generator and a supersonic radial turbine. The design rotational speed of the turbogenerator is 31 000 rpm and the rated electric power output of the system is below 10 kW. The operation of the feed pump was investigated with different rotational speeds and under different flow rate conditions. In the experiments, the pump was capable to be operated at the target rotational speed range of 12 000 rpm to 31 000 rpm and the target pressure increase as well as the target working fluid flow rate were reached. This study presents the design method that was used for defining the partial emission pump geometry and analyses the operation of the pump under various operating conditions and rotational speeds. In addition, the methods for avoiding cavitation in this type of pumps are discussed. The results of the study shed light on the most important aspects in designing high pressure ratio – low flow rate feed pumps for ORC applications and discuss the specific operational characteristics of this type of pumps.      «

A reliable operation and reducing the power consumption of the feed pumps of the ORC systems are highly important as the feed pump is one of the main components affecting the ORC power plant operating pressures, controllability, and the cycle net power output. Especially in small-scale and high -temperature ORC systems, the design of an efficient feed pump can be challenging because the required pressure increase over the pump is high and on the other hand, the working fluid flow rates are small...     »