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FPE Concept
Hydraulic/Electric Synergy
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FPE Concept
 As serial hybrid concept, without direct mechanical connection between internal combustion engine and wheels, it allows utilization of the 'free piston engine' (FPE) insted of the standard Diesel engine. Free piston engine has only half the parts of the standard internal combustion engine that will result with further mechanical simplification of the hybrid drive. Aditionally, providing the synergy between hydraulic and electric technology it will offer new posibilites in the hybrid driveline optimisation. Schematic presentation of the concept is given by the next figure. 


Most important benefits introduced by the synergy 
Hydraulics can provide the compact, efficient and cost effective hybrid drive capable to store/restore the energy during braking/acceleration at alomst half the price of the full electric hybrid drive.

Having source of the electrical energy that can cover around 20% of the nominal engine power, equally small electric motor (20% of nominal power) will be sufficient to cover power demand during the highway drive (cca 100 km/h ), providing efficiency and low noise operation at higher speeds. As the energy recovery is performed with the hydraulic accumulators, more expensive battery pack isn’t needed. This will reduce overall price of the system and recycling needs of the technology.

As the linear electric actuators can generate power burst equal to 4 times of the nominal power, full power stroke (around 20 % of energy is already stored as compressed air in combustion chamber) can be provided without fuel combustion. Therefore, uninterrupted work of the free piston engine will be maintained even in case of the misfire of the diesel engine. In this case, electric actuator can be seen as the electric fly-wheel of the free piston engine.

As the electric systems has faster response time than variable displacement hydraulic machines, linear electric actuator can be used for fine tuning of the force balance between forces acting on to the free piston engine moving part. This will allow the precise control of the combustion process of the free piston engine;

To start hydraulic free piston engine it is necessary to build up the pressure in hydraulic accumulator. This has to be done with additional pump powered with additional electric motor and often with additional valve for flow control. Having hydraulic/electric free piston engine, electric linear actuator can be used as the starter without need for the additional systems, previouslly mentioned. Again, overall system can be simplified and total cost reduced.

The synergy between hydraulics and electrics can offer some additional interesting possibilities but those five points have been seen as the most important ones.
Full potential of the synergy between hydraulic and electric technology is possible only with the complete control of the energy flow in both technologies. In order to provide mentioned control a new variable displacemnew variable displacement linear vane hydraulic pump ent linear vane hydraulic pump has to be developed. Development of this new vane pump technology is the most important part of the Volumtran project. Still, some additional aspects, needed for creation of the fully successful hybrid drive concept are also considered such as; piston lubrication in free piston engine, vibration compensation etc. Once, all systems presented, full meaning of the Volumtran project will became evident. In order to show working approach under the project more details about development of the new hydraulic pump (pat. pending) will be given through this site, while other due to the development in progress will be maintained confidential at this stage of the project.