The red line is a three lobe epitrochoid, which is the shape of the LiquidPiston's swept volume
The X-engine is a type of
pistonless rotary engine manufactured by LiquidPiston of
Bloomfield, Connecticut.
The X engine is a hybrid cycle rotary engine.
Design
This is geometrically an inverted
Wankel engine
The Wankel engine (, ) is a type of internal combustion engine using an eccentric (mechanism), eccentric Pistonless rotary engine, rotary design to convert pressure into rotating motion. The concept was proven by German engineer Felix Wankel, f ...
that operates on the
high-efficiency hybrid cycle. In the Wankel, the only successful pistonless rotary engine to date, a figure-eight-like
epitrochoid housing surrounds a
curved sided triangular rotor. The rotor revolves around a fixed gear in a
hula-hoop motion. The output shaft revolves at three times the speed of the rotor. One power pulse is delivered in one revolution of the output shaft. For comparison a single cylinder
four-stroke piston engine delivers one power pulse for two rotations of the output shaft. The three operating chambers of the Wankel formed by the triangular rotor are separated by seals installed on the three apexes of the rotor. They require elaborate lubrication, and in older designs have been a weak point for the engine's durability. The LiquidPiston design reverses the shapes: a figure-eight-shaped rotor moves within a triangular housing. The required seals (both face and apex) are mounted on the stationary housing, which makes lubrication much easier.
Common to both concepts is the use of
ports Ports collections (or ports trees, or just ports) are the sets of makefiles and Patch (Unix), patches provided by the BSD-based operating systems, FreeBSD, NetBSD, and OpenBSD, as a simple method of installing software or creating binary packages. T ...
to supply air and remove exhaust gas, thereby eliminating the need for
valves.
Operating principle
This cycle consists of compressing air (with no fuel) to a very high ratio, as is typical in the
Diesel cycle. The air is then isolated in a constant volume chamber. Fuel is directly injected being allowed to combust fully under constant volume conditions, which is how
Otto cycle combustion is modelled. Finally, the combustion products are expanded to
atmospheric pressure
Atmospheric pressure, also known as air pressure or barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equivalent to 1,013. ...
, utilizing the
Atkinson cycle
The Atkinson-cycle engine is a type of internal combustion engine invented by James Atkinson (inventor), James Atkinson in 1882. The Atkinson cycle is designed to provide Energy conversion efficiency, efficiency at the expense of power density.
...
.
Feasibility
In order to use the Diesel cycle efficiently, high
compression ratio
The compression ratio is the ratio between the maximum and minimum volume during the compression stage of the power cycle in a piston or Wankel engine.
A fundamental specification for such engines, it can be measured in two different ways. Th ...
s are required: Typical engines use between 15:1 and 24:1. The LiquidPiston engine was demonstrated on the Diesel cycle with a compression ratio as high as 26:1.
This would generally rule out the use of
low-octane fuels like
gasoline
Gasoline ( North American English) or petrol ( Commonwealth English) is a petrochemical product characterized as a transparent, yellowish, and flammable liquid normally used as a fuel for spark-ignited internal combustion engines. When for ...
. Therefore a
spark-ignited variant with lower compression was developed. This so-called "X-Mini" is a 70
cc air-cooled naturally aspirated four-stroke X-Engine, and has been demonstrated on gasoline, kerosene,
Jet A fuel, propane and hydrogen.
References
External links
LiquidPiston, Inc. official siteIntegza tour of the engine
Proposed engines
Pistonless rotary engine
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