The Rotary Piston Machine is a new (still in development) form of machine

Machine

A machine manages power to accomplish a task, examples include, a mechanical system, a computing system, an electronic system, and a molecular machine. In common usage, the meaning is that of a device having parts that perform or assist in performing any type of work...

. It can be used either to transform pressure into rotational motion (an engine

Engine

An engine or motor is a machine designed to convert energy into useful mechanical motion. Heat engines, including internal combustion engines and external combustion engines burn a fuel to create heat which is then used to create motion...

), or the converse - rotational motion into pressure (pump

Pump

A pump is a device used to move fluids, such as liquids, gases or slurries.A pump displaces a volume by physical or mechanical action. Pumps fall into three major groups: direct lift, displacement, and gravity pumps...

). It is still in development, but has possible applications in fields requiring oil, fuel or water pumps, as well as pumps for non-abrasive fluids when moderate or high pressure is required. For instance: Hydraulics, fluid and gas transport systems, presses, fuel injection, irrigation, heating systems, hydraulic lifts, water jet engines, hydro- and pneumatic engines, and medical pumps. The machine's inventor is Boris I. Schapiro, along with co-inventors Lev B. Levitin and Naum Kruk.

Design

All versions of the RKM incorporate a working chamber formed by smoothly conjugated circular arcs. The piston, shaped to conform to the chamber's walls, "jumps" from wall to wall, thus performing a rotary motion. The piston has an appropriately shaped aperture fitted with a gear structure, and this drives the power shaft (or two power shafts in some models).

The piston, its aperture and the working chamber of the RKMs represent, in their cross sections, multi-oval figures which, mathematically, are related to the class of figures of equal width. Those multi-ovals are non-analytical figures with a discontinuous second derivative of the contour line (the curvature). Hence, generally speaking, the trajectories of their centers of curvature are also non-analytical and, within the RKMs' geometry, have to have singular points.

In relation to the piston, the trajectory of the power shaft axis has corner points, which correspond to extreme positions of the piston as related to the working chamber. Those corners, which represent singular points of the power shaft's trajectory, cannot be avoided or rounded to provide for the kinematically closed functioning of the gear.

The reason why until now the geometry of figures of equal width could not be put to practical use in the gear design is that no conventional gear structure with the regular rolling on of the gears would permit the exact rolling-on of the singularities. The RKMs solve this problem by introducing the inversely conjugated gear system, which makes it possible to have singular trajectories of the axes of rolling-on gears and, thus, allows the transfer of the angular momentum during the passage of the piston through its stop positions.

In simple words, the gear mechanism introduces corrections to the piston's motion, correcting the axis of rotation as it leaves the stop positions, so as to create a smooth motion.

Possible configurations

In theory, there is no limit to the number of "sides" that a working chamber may have. However, in practice, it is likely that configurations incorporating no more than seven arcs will be used.

In addition, there can be either one or two power shafts in the aperture in the center of the piston.

Of course, the exact configuration of every model depends upon its use. For instance, internal combustion engines would include injection valves and after-burning chambers. These, however, are not part of the RKM concept.

Applications

Potential areas of application for the RKM engines include:

• Pumps: medium-, high-pressure, and pre-vacuum pumps for use in power machinery, refrigerators, elevators, lifts, cranes, road-building machinery, automobiles, aircraft, and other applications, including those for domestic water and heating systems,and scientific research.
• Compressors: medium- and high-pressure compressors for a wide range of industrial and consumer applications.
• "Cold" motors: hydraulic and pneumatic motors for use in automobiles, air-, space- and marine craft, and in a number of other applications in industrial and consumer products.
• Power tools: a new class of power tools for drilling, cutting and surface treatment of materials in various ranges (from super-large to micrometre).
• Internal and external combustion engines, including Diesel, for all types of wheeled or tracked motor vehicles (from motorbikes to automobiles and trucks, to Mars explorers), marine craft of all sizes (from pleasure boats to supertankers), helicopters and propeller-driven aircraft (including super-light platforms).
• Electric power generators for agriculture and industry, including oil and gas production, air & space industry, large stationary and vehicular power generators, compact emergency generators, etc.
• Compact sources of electrical power for portable computers and other electronic devices, etc.

One area where RKMs offer very high potential is in the pump market. RKM pumps can be as, or more efficient than today's preferred pump technologies, while offering overall advantages in pricing, size, reliability and energy efficiency .

Comparison to the Wankel engine

Despite their apparent geometrical similarity, the RKM and the Wankel engine

Wankel engine

The Wankel engine is a type of internal combustion engine using an eccentric rotary design to convert pressure into a rotating motion instead of using reciprocating pistons. Its four-stroke cycle takes place in a space between the inside of an oval-like epitrochoid-shaped housing and a rotor that...

 are quite different in design. The main similarities between them are the shape of the working chamber and the use of rotary motion.

However, there are many differences between the two. The Wankel engine working chamber is mobile while the RKM chamber is stationary. The axis of rotation in the Wankel engine moves in a circle while that of the RKM is fixed (in the single power shaft version, temporarily with two possible positions). In the RKM motor, the ignition takes place in a compact recess, while the Wankel's is in the work chamber itself. The RKM's sealing elements are in surface contact with the work chamber and pistons, as opposed to the Wankel's line contact. This makes for a number of advantages of the RKM motor over the Wankel:

1. Easier adaptation to diesel fuel.
2. Support of forced afterburning
   AfterBurner
   The AfterBurner is a lighting solution for the Game Boy Advance system that was created by Triton-Labs.Originally, portablemonopoly.net was a website created to petition Nintendo to put some kind of light in their Game Boy Advance system...
   
   of gases, which is not feasible with the Wankel geometry.
3. Longer life, lower fuel consumption and higher efficiency.

One application that the two may indeed have in common is miniaturization. A miniature Wankel engine has been successfully constructed , and it stands to reason that the same can be done for an RKM.

Although developed in the 1960s, today there are no runnable RKM engine demonstrated.

External links

• Movies of RKM engines and compressors
• MIT Technology Review (German edition), 7 August 2007, "Der Anti-Wankelmotor" (The anti-Wankel engine)
• Frankfurter Allgemeine Sonntagszeitung, 28 Oktober 2007, "Und er dreht sich doch noch" (And yet it turns)
• Наука и Жизнь (Science and Life), № 5 2008, "Овальные поршни, треугольные цилиндры" (Oval pistons, triangular cylinders)
• ICSAT2008: International Conference on Sustainable Automotive Technologies (see Schapiro abstract)