Alternative Experimental Engines

Alternative Experimental Engines
Other experimental engines are under development. However, none of them combines all the advantages of the Libralato engine.

Liquidpiston Engine Novel design with separated expansion chamber Very high thermal loading on combustion chamber device which will make sealing a significant problem Friction losses very high Cooling of the expander may also be an issue
RAD Max Novel rotary 12-vane positive displacement device that produces 48 pump actions every revolution Excessive number of moving parts needed Excessive number of sliding components Force translation performed by sliding components
Lontra Engine Novel design based on two separate cylinders with a ceramic coated conduit joining them Two cylinder design is not very compact – lower power to weight ratio Conduit is vulnerable to vibration and could fracture; so the design is not so appropriate for vehicle applications Company targeting different markets for compressors and gensets
Astremo Engine Novel opposed 2 stroke technology Exceptionally higher power to weight ratio Uses piezo electric direct injection Requires development of new lubrication system Inherent low fuel efficiency and high emissions of two stroke design compensated for by use of piezo electric direct injection, but this is a high pressure, high manufacturing tolerance, high cost, high maintenance approach. Questionable whether it will meet Euro 6 emission standards
REVETEC Engine Novel 4-stroke design uses two counter rotating tri lobular cams and rollers to produce the reciprocating motion normally generated by a crankshaft and connecting rod Independently verified to achieve 38.5% efficiency (BSFC 212g/kWh @ BMEP 4.5 bar, 2000 rpm, lean-air ratio 15.2: 1) Claimed to be the most efficient gasoline engine in the world Licensing with Chinese manufacturers being negotiated Engine itself does not represent substantial size/ weight/ cost savings
Ox2 Engine The Ox2 engine is a circular engine block containing 8 cylinders which exert their force on a bevel shaped cam. While a camshaft rotates on a 4-stroke engine, the entire engine block rotates on the Ox2 engine Pistons are connected by rings (called "plates") that move via rollers along a fixed cam (track) At higher rpm (1,000<) the centrifugal force lifting the pistons from the track increases, therefore the size and power of the engine is limited
STAR ROTOR Engine The Star Rotor engine is based on a recuperated Brayton cycle gerotor, which has separate compressor and expander units. This is predicted to have exceptionally high efficiency (up to 50% at full load) because: The recuperator captures thermal energy from the expander exhaust and recycles it into the engine The rotors do not touch thereby reducing friction Speed control is accomplished without throttling losses Fuel combustion is complete thus reducing the amount of fuel required to operate Spraying atomized liquid water into the compressor allows nearly isothermal compression, reducing compression work significantly This engine shares many of the advantages of the Libralato engine and even possibly exceeds them through the use of a Brayton cycle approach However at full load, the engine consumes 2 gallons of water for every gallon of gasoline. This extra requirement limits the application of the engine in an automotive context
Anyoon Rotary Engine The Anyoon rotary engine is a novel concept with some of the advantages of the Libralato engine and the Star Rotor engine: Like the Libralato engine it uses a greater expansion volume than the compression volume Like the Star Rotor engine it uses injected water to cool the combustion chamber Sealing is a major problem for this design and very expensive diamond like composite materials are being investigated to counter the problem Stoppers held by rollers in a track of parabolic spirals, are subject to fatigue, seal wear and maintenance issues Use of injected water limits the application of the engine in an automotive context
Lotus Range Extender Engine (series hybrid) Three cylinder 1.2L, 56 kg gasoline engine optimized between two power generation points: 15kW @ 1,500 rpm and 35 kW @ 3,500 rpm Innovative architecture comprising an aluminum monoblock, integrating the cylinder block, cylinder head and exhaust manifold in one casting This engine is not powerful enough to power a mid sized vehicle at more than about 85 mph / 140 kph Engine efficiency is estimated to be significantly less than the Libralato engine, in the region of 240 g/kWh
Hefley Engine The Hefley engine is a variable displacement engine with opposed pistons acting on a central cam, similar to the REVETEC engine The design is not space efficient Potential fatigue issues on the central connecting shaft The usefulness of variable displacement for different fuels is questionable
Scuderi Engine The Scuderi engine is a split cycle engine which divides the four strokes of a conventional combustion cycle over two paired cylinders, with one intake/compression cylinder and one power/exhaust cylinder The design is not space efficient The design involves extremely high pressures which require extremely high tolerances and high manufacturing costs
GO Engine The Go engine is a conventional engine which incorporates eccentric bearings with a planetary gear. This allows variable compression ratios and use of Atkinson cycle greater expansion volume compared to compression volume The engine does not offer significant advantages in terms of size, weight, vibration, noise, cost etc
Moller Engine The Moller engine is a Wankel type engine with improved combustion surface coating and incoming fuel-air charge cooling. This allows it to avoid the disadvantages of the oil cooling system used by Mazda The Moller engine achieves a similar power to weight ratio as the Libralato engine, but is less efficient at about 255g/kWh BSFC

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