A. Sánchez Ultra-Compact Multi-Fuel Rotary Engine v2017, for Range Extenders & UAV


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This novel internal combustion rotary-cylinder engine performs 4-stroke cycle without
reversing movements and drastically reducing parts number, because it does not use a valve mechanism, and also because auxiliary lubrication and cooling systems are autonomous with simple operation.

Currently 4-stroke reciprocating engines have limited performance because losing power in moving the complex valve mechanism, and reversing the piston and connecting rod masses each stroke. Further, valves operation limits the maximum speed of rotation. Reversion produces vibrations that again subtract power. Static configuration of engine block prevents homogeneous cooling by direct air, being necessary the intermediation of a pumped water cooling system that increases build price, complicates maintenance and affects its duration. Operation with valves limits breathing capacity and increases pollutant emissions, especially nitrogen oxides. Another disadvantage of conventional engines is the difficulty of operating with hydrogen because head space limitations, that difficult placement of more than one nozzle or spark plug and because all phases are made in the same combustion chamber. On the other hand currently known rotary engines, although they do not use valves, are similar in complexity to alternative engine and have less performance. In particular Wankel rotary engine has an elongated and necessarily cooled combustion chamber, which adversely affects combustion. In addition, the rotor configuration hinders the lubrication, cooling and limits compression ratio.


This rotary-cylinder engine is specially designed for the propulsion of an electric generator in a Range Extender of electric vehicles. Engines currently used in range extender are complex as engines that propel traditional vehicles, with similar price, efficiency and volume occupied. Electric vehicle needs a very efficient range extender able to use alternative fuels, and which also does not affect its useful space, does not increase weigh, with minimal maintenance and above all that does not significantly increase its final price. That is the propulsor expected to achieve with this invention. This engine does not lose power in moving auxiliary mechanisms (valve train, lubrication and cooling pumps, fan..). The mass of the rotor is also the inertial flywheel. Intake and exhaust ports can be large and do not brake the piston by gas pressure or depression. Without a speed limit for operating valves, and without limiting the passage of gases through the intake and exhaust ports, the engine can rotate faster and be more efficient. All this is additional power on the output shaft.

fig 1


A. Sánchez Rotary Engine, is a simple and yet high performance propeller, with adequate
lubrication, combustion and cooling systems. It is free of valves and develops 4-stroke cycle. Cooling is mixed: by forced air on the external surfaces of the stator and rotor, and internally by A. Sánchez Rotary Engine (Range Extender version). pumped and cooled lubricant. As the rotor rotates, the moving parts make a non-reciprocating movement free of stopping and reversing their masses, since they are in permanent rotation. It is
built in steel and aluminum in its different alloys and treatments according to the part function. Stator (1) is a cylindrical cavity formed by a plurality of outer fins in the most heat affected sector, an intake port (1A), an exhaust port (1B) and a spark plug housing (1C), all o f which are synchronously distributed to optimize the operating phases.

fig 3

Stator houses a rotor (2). The rotor is a cylinder that houses an inner cylinder radially
oriented (2A) and openned towards the outside. In this open side is housed an airtighnes seal (3), which is strongly applied against the lips of the radial cylinder and against the stator. A plurality of fan blades (2D) are arranged between the outer cylindrical tube of the rotor and its inner radial cylinder. Radial cylinder houses an articulated assembly composed of a piston (8), a connecting rod (7) and a crankshaft (6). The rotor spins by supporting on the stator its central shaft (2E) that is divided into two half-shafts: upper and lower. To support them, stator has two attached frames (1G). Each frame consists of a central part with a bearing (1F) that supports the central axis, and with a planetary gear (1E) concentric thereto. This central part extends in three radial arms that are
attached to the stator cylinder whith bolts. The crankshaft have at each end a satellite gear (6A). Each satellite is meshed with a planetary. The number of teeth of each planetary is equal and is double in relation to the one of each satellite.

fig 4

The carter (5) rotates solidly with the rotor, being attached under it. Take advantage of the rotating movement to push the lubricant through the circuit. At rest it contains all the lubricant. The carter is formed by two cuvettes connected to each other by two segments of hollow circular crown. A cuvette has two distributed windows that communicate with the inside of the crankcase through two valves (2C). The opposing cuvette has holes that communicate with the inside of the radial cylinder seal guides. The carter also takes advantage of the pressure-depression created by the piston in the area that sweeps the crankshaft assembly, to pump lubricant, which in the suction phase is attracted directly by the piston and cylinder. The carter is cooled by the air sucked by the
rotor blades.

fig 5




Engine operation shown in Figures 7, 8, 9 and 10. When the rotor spins 1 turn on its axis, the crankshaft rotates that same turn in conjunction with the rotor. As each satellite is geared to a fixed planetary, and each planetary has double number of teeth than each satellite, one turn of the rotor produces two counterclockwise turns in the crankshaft.

Each turn of the crankshaft on its own axis produces two strokes of the piston outward and back. A complete turn of the rotor produces four strokes in the piston, passing each of them in 90º A. Sánchez Rotary Engine (Range Extender version). of rotor rotation. At each stroke, the piston moves towards or away from the stator alternately, thereby varying the volume therebetween.

Figure 7 shows the start of the intake stroke. The rotor is rotating, while the piston is
separated from the stator by developing the intake stroke. At the beginning of this stroke, the radial cylinder discovers the intake port, through which it draws air and fuel mixture. Intake stroke ends when the piston reaches its maximum point away from the stator.


At this point starts the compression stroke that shown in figure 8. The piston starts the stroke that approach it to the stator. Then, the rotor in its advance covers intake port and begins to compress the previously admitted mixture into the radial cylinder. At the end of this compression stroke, the radial cylinder discovers the spark plug port, and simultaneously an electric spark jumps between the electrodes thereof, which causes the ignition of the now compressed fuel mixture. Inmediatelly afterwards power stroke begins shows in figure 9.

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The piston receives the thrust of the fuel explosion, which is converted into positive thrust on the rotor and output shaft, by means of the mechanical conversion carried out by the connecting rod on the crankshaft, which in turn applies its gears on the planetary, driving and rotate the rotor. At the end of the power stroke, the radial cylinder discovers the exhaust port.

Then starts exhaust stroke that shown in Figure 10, in which the piston approaches the stator by pushing the gases from the inside of the radial cylinder to the outside of the engine. At the end of this stroke the four operating phases have been completed, which will be repeated successively and uninterruptedly, keeping the rotor spinning.


Heat generated by the power strokes is mainly carried out by the fan blades of the rotor,
which when rotated with this, impel fresh air that is admitted by the upper part, and is expelled by the lower one after having completely cooled it. The stator dissipates heat in two ways: by radiation from its outer fins, and by permanent and complete contact of its internal cylindrical surface with the outer cylindrical surface of the rotor, which, when rotating, distributes heat, cools and regularises the temperature throughout its cylindrical surface, guaranteeing the thermal homogenization of the stator-rotor assembly.


The carter rotates, imparting lubricant on all the inner walls of the rotor and soaking the parts that it contains. The cylinder seal is constantly applied against the cylindrical interior of the stator and against the open lips circumference of the radial cylinder, guaranteeing the tightness of the cylinder and also lubricating the cylindrical surfaces of the stator and rotor that spinning in permanent contact, since the oil reaches the seal pins, traversing them and filling the outer grooves of the seal in contact with the stator.



4-Stroke reciprocating engine is complex because it needs valves to operate. Valves and their associated mechanics are expensive in relation to the rest of the engine. It is necessary to lubricate. Moving them also consumes power. But in addition they occupy, with the spark plug, almost all the surface of the cylinder head. When installing 4 valves, a spark plug and an injector it is not possible to sufficiently size these devices for their optimal operation. For some alternative fuels this is a disadvantage. Likewise the surface limitations of the valve channels limit intake and exhaust flow, and therefore the maximum efficient speed of operation. Even more important is that valves have mechanically limited operation speed.

A. Sánchez Rotary Engine purpose is to get a simpler, cheaper and more efficient engine.
The surface available for intake and exhaust ports, spark plugs or injectors is extraordinarily wide, as most stator circular inner surface is available. Have an extraordinary breathing capacity and the possibility of installing several nozzles and spark plugs (i.e. for hydrogen combustion). The high valveless breathing capacity allows for more efficient operation at high speeds with no limitations on the use of alternative fuels.

On the other hand, an alternative engine cooled by direct air does not homogenize the
temperature in the combustion chamber-piston-cylinder assembly, alternating hot and cold areas. This adversely affects compression and combustion, and therefore, efficiency. Cooling with water corrects these drawbacks, but makes the engine more complex and bulky, more expensive to build and maintain. Moving the water through the different cavities of the engine consumes power.

In A. Sánchez Engine design, cylinder, piston, connecting rod and crankshaft assembly operates exactly as in a conventional engine. The manufacturing process and reliability is the same. The difference is that this assembly rotates with the rotor. Piston never stops. Then, piston mass is not critical, reduces vibrations and, together with the large intake and exhaust ports, will undoubtedly allow higher turning speeds without difficulties with gas loading and combustion, to increase efficiency. The combustion chamber is very similar to a conventional engine. It is possible to advance ignition in relation to the position of the piston in the TDC up to 40º in the designed prototype. The rotor also acts as a fan by driving air through it as it rotates. As in a fan’s propellers, the airflow performs a complex turbulent movement that cools and ensures the homonegeization of the temperature throughout the mass of the rotor. The circular faces of the rotor and stator that contact permanently will equal their temperature with the particularity that the inner circular face of the stator exposed to the flame will transfer its heat excess to the entire circular face of the rotor. It is to be expected that a stable temperature will be maintained without major differences in the entire mass of the stator and the rotor. Also is expected high capacity to evacuate heat.

avance encendido

There are many rotary engine designs. Wankel engine is really more complex than alternative, more expensive to build and maintain and less efficient. Parts are difficult to machine and require special treatments. The main technical problem of the Wankel engine is inherent in its basic design. The rotor spins supported on the stator inner guide. This is not completely circular (epitrochoid). Then, the rotor mass applies its sharp vertex against the stator. This pressure strikes hard at medium-high speed when the vertex are pushed in by the stator. This necessarily causes compression leaks, seizures and wear.

Cooling is complex and expensive in Wankel engine. The rotor is completely interior and
exposed to the power flame on its three faces. To cool it properly it is necessary to use liquid pumped inside. Stator must also be liquid cooled, to homogenize temperature throughout its mass and avoid deformations that harms compression and combustion more.

Lubrication in this engine is even more problematic, complex and expensive. The three rotor vertex with their seals not only continuously contact the stator, but are pressed and hit. It is then necessary for the seals to apply oil continuously to the stator surface. Each vertex must have a single seal, so the applied oil can not be collected and is burned at each combustion. Really, the pressure exerted by power strokes on the seals and the vibrations, prevent to obtain a minimum airtightness between the three chambers, with the associated problems.

In A. Sánchez engine, tolerances between rotor-stator cylindrical surfaces in contact are similar as conventional piston-cylinder assembly. At all times there is a sheet of oil between these two bodies although the oil is isolated from the combustion chamber. The configuration of the seal ensures the tightness of the cylinder, mouth keeps oil continuously out. The lubricant that reaches this seal is subjected to consecutive pressures and depressions by the action of the piston on the carter. This implies that there must be no leakage to the cylinder or to the intake or exhaust ports.

Incomplete combustion is another disadvantage of Wankel engine. Power stroke start is
mechanically critical and mismatches. Combustion chamber has a large surface area in relation to its volume. This difficult combustion and harms efficiency. Combustion in A. Sanchez engine is similar to conventional piston engine. If, on the above basis, we obtain combustion efficiency similar to alternative piston engine, then final performance of A. Sánchez engine will be increased by:

– Elimination of losses by valves actuation.
– Elimination of losses by pumping liquids.
– Elimination of losses by vibrations (reversion of the piston, valves, etc).
– More efficient because can spin at high r.p.m.
– Can operate with hydrogen and other cheap fuels.

Compared to Wankel engine, has these advantages:
– Much simpler design: More reliable and easier to maintain, assemble, disassemble, etc.
– Lower weight, less parts, cheap and easy to machining. It can have significantly lower
final cost.
– Good fuel combustion. Gets more fuel efficiency.
– No burning oil. No need to add oil to the fuel. Less contamination.
– Good sealing. It can achieve high compression ratios.

combustion chamber

A range extender is a reserve engine that can run every day, but it may not run in months or years. When it is more complex it has more possibility of failure. So simplicity in design and reliability after long periods of non-use become a priority. Also is important that the addition of a range extender in an electric car does not significantly increase price.

For a single cylinder engine, 600 c.c. displacement, is estimate dimensions of 35cm.
diameter by 25cm. Height without ignition, exhaust, and carburetor devices. Electric generator, would be directly coupled to the output shaft (there is a 2:1 gear demultiply between the crankshaft and the output shaft). Weight reduction in relation to a single-cylinder engine 600c.c. air-cooled 4- stroke will reach 50%.

dimensionesSimilar combustion efficiency that conventional 4-stroke, water-cooled piston engine is
expected. Vibrations & reversions in piston and valve are supressed, in addition to not consuming power in moving oil & water pumps, and valves, power available on the output shaft must be higher. The rotary configuration of all moving parts and counterweight of rotor mass should almost eliminate vibrations. Cylinder and piston spins and are housed in stator. Noise must be less than conventional air-cooled engine.