Several new type hydrocyclones were designed for fine particles removal from the liquid by adding internals to the underflow section of the typical solid-liquid hydrocyclone. Both separation efficiency and energy consumption of these hydrocyclones were verified experimentally, aiming to determine whether adding internals could make the hydrocyclone more compact and energy-saving. The results indicated that adding an inner cylinder to the under flow pipe can reduce the Euler number remarkably and has little influence on the separation efficiency. The fixing method of the inner cylinder on the underflow pipe could influence the performance of hydrocyclones in some specific feed flow rates, and it is better to fix the inner cylinder using two crossed thin rods. When the conical section length was reduced by about 1/3, the separation efficiency of the hydrocyclone with an inner cylinder decreased only 1.1%-2.0% and was similar to the traditional one under high feed flow rates. Under low feed flow rates, the separation efficiency of this shortened hydrocyclone decreased as high as 5.8%. Meanwhile, both the overflow and underflow Euler number decreased significantly when the conical section length was shortened. In addition, it is shown that the separation efficiency under low feed flow rates can be enhanced by adding a short inner cone at the bottom of the hydrocyclone's conical section. New conceptions proposed in this work can be used to design compact industrial hydrocyclones for fine particles separation under low inlet pressure. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.