Libralato Engine Overview
THE LIBRALATO ENGINE - Invented by Dr. Ruggero Libralato; a teacher of electrical engineering by trade, Dr. Libralato’s keen interest in combustion engines from a young age led him to design a new combustion engine at the age of 27. Over 25 years, through various design iterations, the profound study of thermodynamics and theory of machines, Ruggero Libralato has invented a completely new design and a new thermodynamic cycle which deserves to rank alongside the names of Otto, Diesel and Wankel.
A proof of concept first prototype was built in 2005.
The Libralato rotary engine is a potential breakthrough technology – an eco-engine for the 21st century, with an asymmetrical geometry of expansion and compression volumes, which does not need to convert the linear motion of pistons into the rotary motion of the output shaft. The Libralato engine is predicted to demonstrate: a power phase in every revolution (giving it twice the power density of a reciprocating engine), exceptionally high mechanical and thermal efficiency, beyond Euro 6 standards of emissions, high and constant levels of torque, very low vibration, low exhaust gas noise and temperature with no need for valves, pistons, con-rods, crankshafts, cam shafts etc.
Comparison of Libralato engine with piston engine and Wankel engine
The proof of concept engine mechanism has been rotated at 3,000 rpm, demonstrating the dynamic balance of the engine and the integrity of its aspiration / expiration mechanism. It has not run as a hot engine yet since without the proper lubrication and cooling systems it would seize very quickly.
The engine design is exceptionally compact and robust, approximately half the size and weight of a conventional reciprocating engine. It is ideally suited to a wide range of applications 1kW - 200kW, particularly where space, weight, emissions, noise and vibration restrictions apply; constant speeds are required and the engine is able to operate in its peak efficiency zone.
Libralato engine schematic
Exploded View of Libralato Engine Principal Parts
The Libralato engine design is very different from the Wankel engine and avoids the problems of the Wankel engine by: large sealing surface areas of the rotors (equivalent in size to pistons), short flame paths acting against an acute angle working surface area, good thermal dispersion via fresh air scavenge phase and low bearing wear due to dynamic balance.
The Libralato engine has only four principal moving parts: two rotors fixed by their own bearings, connected by a sliding rod and a rotating exhaust. The rotors have different (overlapping) diameters of circumference and their motion forms and reforms three separate chambers within the engine each revolution.
The engine comprises a unique combination of two rotors, with different rotational diameters and separate centres, fixed by their own bearings and joined by a connecting piece that has a quasi-circular orbit. The motion of the rotors forms and reforms three distinct chambers within the engine each rotation, with asymmetrical expansion and compression volumes, two stage compression and low pressure scavenge. Induction air enters at the centre of the engine and compression/expansion occurs at the periphery producing uniform heat flow characteristics as air circulates around the two sides of the engine.
New Thermodynamic Cycle - The engine does not have a traditional Otto or Diesel cycle. There are two compression phases. The inlet phase is compressed at a low ratio and then controls the later scavenge of the residual exhaust gases. In the second compression phase, the air is compressed at a higher compression ratio where the fuel is added. It is this fuel/air mixture that ignites to form the expansion phase. This all provides for an extremely efficient handling of the gases, with a significant reduction of exhaust emissions and excellent fuel economy.
The main advantages of the engine can be summarized as:
- Mechanically simple design leading to 30% lower production and maintenance costs
- 100% better power to weight ratio than a reciprocating engine; due to compact shape
- 30% greater efficiency (relative) than conventional 4-stroke engine
- 5% greater mechanical efficiency (absolute) / low vibration due to rotary design
- 4% greater thermal efficiency (absolute) due to asymmetrical expansion and compression
- Exceeding Euro 6 emissions standards due to highly turbulent fuel-air mixing and complete scavenge of residual exhaust gases.
- Very quiet and lower temperature exhaust gases, due to low exhaust pressure
- Good sealing and thermal dispersion characteristics, avoids problems of Wankel engines
- Geometry easily adaptable for biofuels (ethanol and biodiesel)
- Ideally suited for HEVs and PHEVs - space and weight savings from engine allow all hybrid components to fit within existing engine cavities, with little/ no bodywork redesign
Libralato Engine stages