Features / FAQ
Features and advantages of free piston engines
- High power-to-weight ratio
The absence of crankshaft and flywheel and thus a much more compact housing allows the highest imaginable power-to-weight ratio for internal combustion engines.
A simple design with few moving parts allows a compact integration of two machines in a common housing (e.g. internal combustion engine and alternator).
High thermal efficiency
The piston acceleration is not restricted respectively determined by the crankshaft, it is therefore up to 4 times higher. This allows a much higher combustion pressure and combustion temperature, because the high piston acceleration avoids excessive heat transfer loss through the cylinder wall.
Homogeneous charge compression ignition (HCCI)
The free-piston engine is perfectly suited for the realization of the HCCI concept, not only in the partial load range: No knocking can occur because of the lack of a crankshaft.
The arrangement of several free-piston engines enables a cascade connection. At part load operation, individual engines are switched on and off as needed. This improves the (already very high) efficiency of these engines under part load operation significantly.
Frequently asked questions FAQ
- Does the engine stop after misfiring?
In a free-piston engine, the kinetic energy is stored in the relatively heavy piston(s). The piston(s) take over the function of the non-existent flywheel. Therefore, misfiring does not stop the engine immediately.
- What about lubrication?
Unlike conventional engines, there is no piston side force due to inclination of the connecting rod, and no overturning moment. Thus the friction is reduced considerably. Furthermore, no bearings have to be lubricated. Using appropriate coatings and/or materials, the engines can be operated without lubrication.