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A dual-piston, two-stroke, compression ignition free piston engine has been simulated with zero- and one-dimensional performance simulation codes. The simulation models used in the codes have been developed to analyze and improve the internal combustion engine process of a hydraulic free piston engine prototype. The prototype was designed and constructed in Tampere University of Technology at the Institute of Hydraulics and Automation. Performance simulation analyses were conducted in Helsinki University of Technology at the Internal Combustion Engine Laboratory. The zero-dimensional model is used for the simulation of piston dynamics. The one-dimensional model is used for performance simulation, especially for the simulation of gas exchange process. The simulation results were verified through prototype engine measurements.

A hydraulic free piston engine (HFPE) 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 containing three parts, combustion and hydraulic pistons and piston rod. The piston assembly moves during operation linearly back and forth between left and right extremes by means of the fuel energy. Simultaneously hydraulic piston produces directly hydraulic energy. The HFPE enables higher power density and lower manufacturing costs than a conventional engine-pump combination. These are consequence of simpler design. This paper presents experimental results of Dual Hydraulic Free Piston Engine. The presented results contain measured data from a running engine and analysis based on the results of the operation. The handled results include piston motion, pumping and combustion processes. Shown results are unique, because such results have not been presented before.