HYDRAULIC FREE PISTON ENGINE-THE POWER UNIT OF THE FUTURE?

Abstract

During last decade research in the field of hydraulic free piston engines has increased. There are at least three projects developing hydraulic free piston engines (HFPE) in Europe and in the USA and Japan some activities have been reported in this area. A hydraulic free piston engine combines a diesel engine and a hydraulic pump into one compact component. In practical view there is only one linearly moving part in the HFPE, the piston assembly, which contains combustion and hydraulic piston and piston rod. The piston assembly moves during operation linearly back and forth between left and right extreme by means of the fuel energy. Simultaneously hydraulic piston produces directly hydraulic energy. This paper deals with aspects of the hydraulic free piston engine concepts compared to conventional engine pump combination. The paper includes description and comparison of different HFPE concepts and their features. The paper deals with recent development of the engine concepts and some future aspects as well.