Helsinki University of Technology

Helsinki University of Technology
Internal Combustion Engine Laboratory

Pulse Two








(in Finnish)



Project: Pulse Two - Performance of a Hydraulic Free Piston Engine

Contact: Professor Martti Larmi
Tel. +358-9-451 3459

The main project, Pulse 2001, is carried out in co-operation with Tampere University of Technology, Institute of Hydraulics and Automation (TUT/IHA) and some companies, whose products has similar features than free piston engine. The project Pulse Two is a subproject of Pulse 2001 and is carried out at the HUT/ICEL.

Prototype of the hydraulic 
free piston engine

The basic research phase, which was mainly funded by TEKES (Finnish National Technology Agency), started in the beginning of the year 1997 and was finished at the end of the 1999. The goal of this stage was to develop peripheral technologies, which are used in the hydraulic free piston engines, and to create solid base for the future studies. Such technologies are combustion, fuel injection, control, measuring and hydraulics. During the two year phase basic analysis of the concept and basic simulations was carried out, also experimental tests in the field of sensor, valve and pump technology was done. In addition to this the first prototype engine was designed and built.

The project is in its second phase. The objective of this phase is to find out the dependence of the performance characteristics and applicability of the hydraulic free piston engine on the design and operation parameters. The study has great novelty value because such studies concerning the behaviour of the performance characteristics of the hydraulic free piston engine in different operation points has not been reported before.

Mechanical system 
simulation model of the hydraulic free piston engine

The research methods are analytical studies, computer simulation and experimental tests with prototype engine. Simulations are performed with different kind of simulation software. Experimental tests with prototype engines are used to verify the simulations. During the second phase of the project a new prototype engine will be designed and built.

About the Free Piston Engine

The free piston engine is so called dual piston hydraulic free piston engine. The engine has two combustion cylinders at both ends of the engine and the hydraulic pump is located in the middle. The combustion engine is two-stroke diesel engine with direct fuel injection. The hydraulic pump is a constant displacement plunger pump. The power level is around 20 kW. The studied dual piston design is based on the patents, which are property of Sampower Ltd., which main shareholder is SITRA (Finnish National Fund for Research and Development).