The Rotary Piston Machine (german: Rotationskolbenmaschine (RKM)) is a proposed (still in development) form of

machine A machine is a physical system using Power (physics), power to apply Force, forces and control Motion, movement to perform an action. The term is commonly applied to artificial devices, such as those employing engines or motors, but also to na ...

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

engine An engine or motor is a machine designed to convert one or more forms of energy into mechanical energy. Available energy sources include potential energy (e.g. energy of the Earth's gravitational field as exploited in hydroelectric power gen ...

), or the converse - rotational motion into pressure (

pump A pump is a device that moves fluids (liquids or gases), or sometimes slurries, by mechanical action, typically converted from electrical energy into hydraulic energy. Pumps can be classified into three major groups according to the method they u ...

). 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.Schapiro, B., "The RKM Rotary Piston Maschines" In: Vernetzte Wissenschaften, Eds: Peter Jörg Plath und Ernst-Christoph Haß, Logos Verlag, Berlin 2008 The machine's inventor is Boris I. Schapiro, along with co-inventors Lev B. Levitin and

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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 Figure may refer to: General *A shape, drawing, depiction, or geometric configuration *Figure (wood), wood appearance *Figure (music), distinguished from musical motif *Noise figure, in telecommunication *Dance figure, an elementary dance patte ...

. 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

curves of constant width In geometry, a curve of constant width is a simple closed curve in the plane whose width (the distance between parallel supporting lines) is the same in all directions. The shape bounded by a curve of constant width is a body of constant 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.RKM's – Rotating Piston Machines – Scientific and Technical Comments
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:RKM's – Rotating Piston Machines – Project Summary
/ref> *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.Schapiro, B. and Terlitsky, L., "The RKM (RKM) Rotary Piston Machines with the Jumping Momentously Axis", Proceedings of the International Conference on Sustainable Automotive Technologies 2008 (ICSAT2008), 4th to 9th November 2008 in Melbourne, Australia

Comparison to the Wankel engine

Despite their apparent geometrical similarity, the RKM and the

Wankel engine The Wankel engine (, ) is a type of internal combustion engine using an Eccentric (mechanism), eccentric rotary combustion engine, rotary design to convert pressure into rotating motion. It was invented by German engineer Felix Wankel, and desi ...

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: #Easier adaptation to diesel fuel. #Support of forced

afterburning An afterburner (or reheat in British English) is an additional combustion component used on some jet engines, mostly those on military supersonic aircraft. Its purpose is to increase thrust, usually for supersonic flight, takeoff, and combat ...

of gases, which is not feasible with the Wankel geometry. #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,Fu, K., Knobloch, A., Cooley, B., Walther, D., Fernandez-Pello, A. C., Liepmann, D., and Miyasaka, K., Microscale Combustion Research for Applications to MEMS Rotary IC Engine, Proc. 2001 National Heat Transfer Conference, Anaheim, CA, June 10–12, 2001. 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.

References

External links