2008年3月1日 星期六

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Wankel Engine in Deutsches Museum Munich, Germany

Wankel Engine in Deutsches Museum Munich, Germany

The Wankel rotary engine is a type of internal combustion engine which uses a rotor to convert pressure into a rotating motion instead of using reciprocating pistons. Its four-stroke cycle is generally generated in a space between the inside of an oval-like epitrochoid-shaped housing and a roughly triangular rotor. This design delivers smooth high-rpm power from a compact, lightweight engine.

The engine was invented by German engineer Felix Wankel. He began its development in the early 1950s at NSU Motorenwerke AG (NSU) before completing a working, running prototype in 1957. NSU then subsequently licenced the concept to other companies across the globe, who added more efforts and improvements in the 1950s and 1960s.

Because of their compact, lightweight design, Wankel rotary engines have been installed in a variety of vehicles and devices such as automobiles and racing cars, aircraft, go-karts, personal water crafts, and auxiliary power units.

[edit] History

First Wankel Engine DKM54 (Drehkolbenmotor), at the Deutsches Museum in Bonn, Germany
First Wankel Engine DKM54 (Drehkolbenmotor), at the Deutsches Museum in Bonn, Germany
Wankel Engine NSU KKM 57P (Kreiskolbenmotor), at Autovision und Forum, Germany

Wankel Engine NSU KKM 57P (Kreiskolbenmotor), at Autovision und Forum, Germany
NSU Wankel Spider, the first line of cars sold with Wankels

NSU Wankel Spider, the first line of cars sold with Wankels
Rolls Royce R6 two stage Wankel Diesel engine

Rolls Royce R6 two stage Wankel Diesel engine

In 1951, Wankel began development of the engine at NSU (NSU Motorenwerke AG), where he first conceived his rotary engine in 1954 (DKM 54, Drehkolbenmotor) and later the KKM 57 (the Wankel rotary engine, Kreiskolbenmotor) in 1957. The first working prototype DKM 54 was running on February 1, 1957 at the NSU research and development department Versuchsabteilung TX.[1]

Considerable effort went into designing rotary engines in the 1950s and 1960s. They were of particular interest because they were smooth and quiet running, and because of the reliability resulting from their simplicity.

In the United States, in 1959 under license from NSU, Curtiss-Wright pioneered minor improvements in the basic engine design. In Britain, in the 1960s, Rolls Royce Motor Car Division at Crewe, Cheshire, pioneered a two-stage diesel version of the Wankel engine.[2]

Also in Britain Norton Motorcycles developed a Wankel rotary engine for motorcycles, which was included in their Commander and F1; Suzuki also made a production motorcycle with a Wankel engine, the RE-5. In 1971 and 1972 Arctic Cat produced snowmobiles powered by 303 cc Wankel rotary engines manufactured by Sachs in Germany. John Deere Inc, in the U.S., designed a version that was capable of using a variety of fuels. The design was proposed as the power source for several U.S. Marine combat vehicles in the late 1980s.

After occasional use in automobiles, for instance by NSU with their Ro 80 model, Citroën with the M35, and GS Birotor using engines produced by Comotor, as well as abortive attempts by General Motors and Mercedes-Benz to design Wankel-engine automobiles, the most extensive automotive use of the Wankel engine has been by the Japanese company Mazda.

After years of development, Mazda's first Wankel engined car was the 1967 Mazda Cosmo. The company followed with a number of Wankel ("rotary" in the company's terminology) vehicles, including a bus and a pickup truck. Customers often cited the cars' smoothness of operation. However, Mazda chose a method to comply with hydrocarbon emission standards that, while less expensive to produce, increased fuel consumption, just before a sharp rise in fuel prices. Mazda later abandoned the Wankel in most of their automotive designs, but continued using it in their RX-7 sports car until August 2002 (RX-7 importation for North America ceased with the 1995 model year). The company normally used two-rotor designs, but received considerable attention with their 1991 Eunos Cosmo, which used a twin-turbo three-rotor engine. In 2003, Mazda introduced the RENESIS engine with the new RX-8. The RENESIS engine relocated the ports for exhaust and intake from the periphery of the rotary housing to the sides, allowing for larger overall ports, better airflow, and further power gains. The RENESIS is capable of delivering 238 horsepower (177 kW) from its 1.3 L displacement with better fuel economy, reliability, and environmental friendliness than any other Mazda rotary engine in history.[3]

VAZ, the Soviet automobile manufacturer, experimented with the design of Wankel-engine cars. In 1978 they designed an engine with two-rotors and, in 1980s started delivering versions of VAZ-2106 with Wankel engines, mostly to security services, about 200 were made.[4] Aviadvigatel, the Soviet aircraft engine design bureau, is known to have produced Wankel engines for aircraft and helicopters, though little specific information has surfaced.

The People's Republic of China is also known to have experimented with Wankel engines, but even less is known in the West about the work done there, other than one paper, #880628, delivered to the SAE in 1988 by Chen Teluan of the South China Institute of Technology at Guangzhou.

Although many manufacturers licensed the design, and Mercedes-Benz used it for their C111 concept car, only Mazda has produced Wankel engines in large numbers. American Motors (AMC) was so convinced "...that the rotary engine will play an important role as a powerplant for cars and trucks of the future..." according to its Chairman Roy D. Chapin Jr., that the smallest U.S. automaker signed an agreement in 1973 to build Wankels for both passenger cars and Jeep vehicles, as well as the right to sell any rotary engines it produces to other companies.[5] It even designed the unique Pacer around the engine, even though by that time AMC had decided to buy the Wankel engines from GM instead of building them itself. However, the engines never reached production by the time the Pacer was to hit the showrooms. Part of the demise of this feature was the rising fuel crisis and concerns about emission legislation in the United States. General Motors' Wankel engine did not comply with emission levels, so in 1974 the company canceled its development. This meant that the Pacer's drivetrain design had to be reconfigured to house the venerable AMC Straight-6 engines with rear-wheel drive.

[edit] Naming

Since its introduction in the NSU Motorenwerke AG (NSU) and Mazda cars of the 1960s, the engine has been commonly referred to as the rotary engine, a name which has also been applied to several completely different engine designs.

[edit] How it works

The Wankel cycle. The "A" marks one of the three apexes of the rotor. The "B" marks the eccentric shaft and the white portion is the lobe of the eccentric shaft. The shaft turns three times for each rotation of the rotor around the lobe and once for each orbital revolution around the eccentric shaft.

The Wankel cycle. The "A" marks one of the three apexes of the rotor. The "B" marks the eccentric shaft and the white portion is the lobe of the eccentric shaft. The shaft turns three times for each rotation of the rotor around the lobe and once for each orbital revolution around the eccentric shaft.

In the Wankel engine, the four strokes of a typical Otto cycle occur in the space between a three-sided symmetric rotor and the inside of a housing. In the basic single-rotor Wankel engine, the oval-like epitrochoid-shaped housing surrounds a rotor which is similar to a Reuleaux triangle, a three-pointed curve of constant width, but with the bulge in the middle of each side a bit more flattened. From a theoretical perspective, the chosen shape of the rotor between the fixed apexes is basically the result of a minimization of the volume of the geometric combustion chamber and a maximization of the compression ratio, respectively. Thus, the symmetric curve connecting two arbitrary apexes of the rotor is maximized in the direction of the inner housing shape with the constraint not to touch the housing at any angle of rotation (an arc is not a solution of this optimization problem).

The central drive shaft, also called an eccentric shaft or E-shaft, passes through the center of the rotor and is supported by bearings. The rotor both rotates around an offset lobe (crank) on the E-shaft and makes orbital revolutions around the central shaft. Seals at the corners of the rotor seal against the periphery of the housing, dividing it into three moving combustion chambers. Fixed gears mounted on each side of the housing engage with ring gears attached to the rotor to ensure the proper orientation as the rotor moves.

The best way to visualize the action of the engine in the animation at left is to look not at the rotor itself, but the cavity created between it and the housing. The Wankel engine is actually a variable-volume progressing-cavity system. Thus there are 3 cavities per housing, all repeating the same cycle.

As the rotor rotates and orbitally revolves, each side of the rotor gets closer and farther from the wall of the housing, compressing and expanding the combustion chamber similarly to the strokes of a piston in a reciprocating engine. The power vector of the combustion stage goes through the center of the offset lobe.

While a four-stroke piston engine makes one combustion stroke per cylinder for every two rotations of the crankshaft (that is, one half power stroke per crankshaft rotation per cylinder), each combustion chamber in the Wankel generates one combustion stroke per each driveshaft rotation, i.e. one power stroke per rotor orbital revolution and three power strokes per rotor rotation. Thus, power output of a Wankel engine is generally higher than that of a four-stroke piston engine of similar engine displacement in a similar state of tune and higher than that of a four-stroke piston engine of similar physical dimensions and weight. Wankel engines also generally have a much higher redline than a reciprocating engine of similar size since the strokes are completed with a rotary motion as opposed to a reciprocating engine which must use connecting rods and a crankshaft to convert reciprocating motion into rotary motion.

National agencies that tax automobiles according to displacement and regulatory bodies in automobile racing variously consider the Wankel engine to be equivalent to a four-stroke engine of 1.5 to 2 times the displacement; some racing regulatory agencies ban it altogether.[6]

[edit] Advantages

Wankel engines have several major advantages over reciprocating piston designs, in addition to having higher output for similar displacement and physical size.

Wankel engines are considerably simpler and contain far fewer moving parts. For instance, because valving is accomplished by simple ports cut into the walls of the rotor housing, they have no valves or complex valve trains; in addition, since the rotor is geared directly to the output shaft, there is no need for connecting rods, a conventional crankshaft, crankshaft balance weights, etc. The elimination of these parts not only makes a Wankel engine much lighter (typically half that of a conventional engine of equivalent power), but it also completely eliminates the reciprocating mass of a piston engine with its internal strain and inherent vibration due to repeated acceleration and deceleration, producing not only a smoother flow of power but also the ability to produce more power by running at higher rpm.

In addition to the enhanced reliability by virtue of the complete removal of this reciprocating stress on internal parts, the engine is constructed with an iron rotor within a housing made of aluminium, which has greater thermal expansion. This ensures that even a severely overheated Wankel engine cannot seize, as would likely occur in an overheated piston engine. This is a substantial safety benefit in aircraft use since no valves can burn out.

A further advantage of the Wankel engine for use in aircraft is the fact that a Wankel engine can have a smaller frontal area than a piston engine of equivalent power. The simplicity of design and smaller size of the Wankel engine also allows for savings in construction costs, compared to piston engines of comparable power output.

Of perhaps the most importance is that Wankel engines are almost immune to catastrophic failure. A Wankel that loses compression, cooling or oil pressure will lose a large amount of power, and will die over a short period of time, however it will usually continue to produce some power during that time. Piston engines under the same circumstances are prone to seizing or breaking parts that almost certainly results in complete internal destruction of the engine and instant loss of power. For this reason Wankel engines are very well suited to aircraft.

Due to a 50% longer stroke duration compared to a four stroke engine, there is more time to complete the combustion. This leads to greater suitability for direct injection. A Wankel rotary engine has stronger flows of air-fuel mixture and a longer operating cycle than a reciprocating engine, so it realizes concomitantly thorough mixing of hydrogen and air. The result is a homogeneous mixture, which is crucial for hydrogen combustion.[7]

[edit] Advantages of the Wankel Stratified Charge Aircraft Engine

Multi-fuel Capability. Small frontal Area. Low engine weight. Reduced engine cooling drag. Improved reliability due to fewer parts. Lower exhaust gas temperatures. No valves or lifters or cams. Safer cabin heat. Coolant coolers can be wing de-icing. More rapid flight descents permissible. Small exhaust and intake manifold volumes benefit turbocharging. Low exhaust emissions. Low fuel consumption. Smooth - balanced operation. Low noise level. Lower airflow than turbine engines. [8]

[edit] Disadvantages

Compared to four stroke piston engines, the time available for fuel to be injected into a Wankel engine is significantly shorter, due to the way the three chambers rotate. The fuel-air mixture cannot be pre-stored as there is no intake valve.

In terms of fuel economy, Wankel engines are less efficient than four stroke piston engines[citation needed].

The surface/volume-ratio problem is so complex that one cannot make a direct comparison between a reciprocating piston engine and a Wankel engine in relation to the surface/volume-ratio. The flow velocity and the heat losses behave quite differently. Surface temperatures behavior absolutely different, the film of oil in the Wankel engine acts as isolator. Engines with higher compression ratio have a worse surface/volume-ratio. The surface/volume-ratio of a Diesel engine is much worse than a gasoline engine, but Diesel engines are well known for a higher efficiency factor than gasoline engines. Thus should we compare equal engines with equal power: a natural aspirated 1,3 liter Wankel engine with a natural aspirated 1.3 liter four stroke reciprocating piston engine with equal power. But such a engine is not possible and a four stroke reciprocating piston engine need twice time more displacement for the same power as a wankel engine. The empty stroke should we not ignore, a cylinder produce only ever second rotation a power stroke. This doubled the real surface/volume-ratio for the four stroke reciprocating piston engine in reality. [9]

Also, problems occur with exhaust gases at a peripheral port exhaust, where the prevalence of hydrocarbon can be higher than from the exhausts of four stroke piston engines.

The trailing side of the rotary engine’s combustion chamber develops a squeeze stream which pushes back the flamefront. With the conventional two-spark-plug or one-spark-plug system, this squeeze stream prevents the flame from propagating to the combustion chamber's trailing side in the mid and high engine speed ranges. This is why there can be more carbon monoxide and unburnt hydrocarbons in a Wankel's exhaust stream. A side port exhaust, as is used in the Mazda Renesis, avoids this because the unburned mixture cannot escape. The Mazda 26B avoided this issue through a 3-spark plug ignition system. (As a result, at the Le Mans 24 hour endurance race in 1981, the 26B had significantly lower fuel consumption than the competing reciprocating piston engines. All competitors had only the same amount of fuel available, because of the Le Mans 24h limited fuel quantity rule.[10])

All Mazda-made Wankel rotaries, including the new Renesis found in the RX8 burn a small quantity of oil by design; it is metered into the combustion chamber in order to preserve the apex seals. Owners must periodically add small amounts of oil, slightly increasing running costs; though it is still reasonable when compared to many reciprocating piston engines.

[edit] Engineering

Apex seals, left NSU Ro80 Serie and Research  and right Mazda 12A and 13B

Apex seals, left NSU Ro80 Serie and Research and right Mazda 12A and 13B
left Mazda old L10A Camber axial cooling, middle Audi NSU EA871 axial water cooling only hot bow, right Diamond Engines Wankel radial cooling only in the hot bow.

left Mazda old L10A Camber axial cooling, middle Audi NSU EA871 axial water cooling only hot bow, right Diamond Engines Wankel radial cooling only in the hot bow.

Felix Wankel managed to overcome most of the problems that made previous rotary engines fail by developing a configuration with vane seals that could be made of more durable materials than piston ring metal that led to the failure of previous rotary designs.[11]

Rotary engines have a thermodynamic problem not found in reciprocating four-stroke engines in that their "cylinder block" operates at steady state, with intake, compression, combustion, and exhaust occurring at fixed housing locations for all "cylinders". In contrast, reciprocating engines perform these four strokes in one chamber, using a cast iron block and aluminum pistons, so that extremes of freezing intake and flaming exhaust are averaged and shielded by a boundary layer from overheating working parts. Freezing temperatures from evaporating fuel prevail at the intake, while ignition reaches temperatures of about 2,300 K (3,700 °F/2,000 °C)[12][verification needed][citation needed], a range that is wider than lubricants and most engine materials can withstand.[citation needed]

The boundary layer shields and the oil film act as thermal insulation, leading to a low temperature of the lubricating film (max ~200°C/400°F) on a water-cooled Wankel engine. This gives a more constant surface temperature. The temperature around the spark plug is about the same as the temperature in the combustion chamber of a reciprocating engine. With circumferential or axial flow cooling, the temperature difference remains tolerable.[13][14][15][16]

Four-stroke reciprocating engines are less suitable for hydrogen. The hydrogen can misfire on hot parts like the exhaust valve and spark plugs. Another problem concerns the hydrogenate attack on the lubricating film in reciprocating engines. In a Wankel engine this problem is circumvented by using a ceramic apex seal against a ceramic surface: there is no oil film to suffer hydrogenate attack. Since ceramic piston rings are not available as of 2008, the problem remains with the reciprocating engine. The piston shell must be lubricated and cooled with oil. This substantially increases the lubricating oil consumption in a four-stroke hydrogen engine.

[edit] Materials

Unlike a piston engine, where the cylinder is cooled by the incoming charge after being heated by combustion, Wankel rotor housings are constantly heated on one side and cooled on the other, leading to high local temperatures and unequal thermal expansion. While this places high demands on the materials used, the simplicity of the Wankel makes it easier to use alternative materials like exotic alloys and ceramics. With water cooling in a radial or axial flow direction, with the hot water from the hot bow heating the cold bow, the thermal expansion remains tolerable.[17]

[edit] Sealing

Early engine designs had a high incidence of sealing loss, both between the rotor and the housing and also between the various pieces making up the housing. Also, in earlier model Wankel engines carbon particles could become trapped between the seal and the casing, jamming the engine and requiring a partial rebuild. (This can be prevented in older Mazda engines by always allowing the engine to reach operating temperature.) It was common for very early Mazda engines to require rebuilding after 50,000 miles (80,000 km). Modern Wankel engines have not had these problems for many years. Further sealing problems arise from the uneven thermal distribution within the housings causing distortion and loss of sealing and compression. This thermal distortion also causes uneven wear between the apex seal and the rotor housing, quite evident on higher mileage engines. Attempts have been made to normalize the temperature of the housings, minimizing the distortion, with different coolant circulation patterns and housing wall thicknesses.

[edit] Fuel consumption and hydrocarbon emissions

Just as the shape of the Wankel combustion chamber prevents preignition, it also leads to incomplete combustion of the air-fuel charge, with the remaining unburned hydrocarbons released into the exhaust. While manufacturers of piston-engine cars were turning to expensive catalytic converters to completely oxidize the unburned hydrocarbons, Mazda was able to avoid this cost by enriching the air/fuel mixture and increasing the amount of unburned hydrocarbons in the exhaust to actually support complete combustion in a 'thermal reactor' (an enlarged open chamber in the exhaust manifold) without the need for a catalytic converter, thereby producing a clean exhaust at the cost of some extra fuel consumption. World gasoline prices rose sharply at the time Mazda introduced their Wankel engine, making the cleaner exhaust/increased fuel consumption tradeoff an unwelcome one for consumers.[citation needed]

In Mazda's RX-8 with the Renesis engine, fuel consumption is now within normal limits while passing California State emissions requirements. The exhaust ports, which in earlier Mazda rotaries were located in the rotor housings, were moved to the sides of the combustion chamber. This approach allowed Mazda to eliminate overlap between intake and exhaust port openings, while simultaneously increasing exhaust port area. The Renesis engine even meets California's Low Emissions Vehicle or LEV standards.

[edit] Automobile racing

3-Rotor Eunos Cosmo engine

3-Rotor Eunos Cosmo engine
Powerplant from a Schleicher ASH 26e self-launching motor glider, removed from the glider and mounted on a test stand for maintenance at the Alexander Schleicher GmbH & Co in Poppenhausen, Germany. Counter-clockwise from top left: propeller hub, mast with belt guide, radiator, Diamond Engines Wankel engine, muffler shroud.

Powerplant from a Schleicher ASH 26e self-launching motor glider, removed from the glider and mounted on a test stand for maintenance at the Alexander Schleicher GmbH & Co in Poppenhausen, Germany. Counter-clockwise from top left: propeller hub, mast with belt guide, radiator, Diamond Engines Wankel engine, muffler shroud.

In the racing world, Mazda has had substantial success with two-rotor, three-rotor, and four-rotor cars. Private racers have also had considerable success with stock and modified Mazda Wankel-engine cars, see video clip.[18]

The Sigma MC74 powered by a Mazda 12A engine was the first engine and team from outside Western Europe or the United States to finish the entire 24 hours of the 24 Hours of Le Mans race, in 1974. Mazda is the only team from outside Western Europe or the United States to have won Le Mans outright and the only non-piston engine ever to win Le Mans, which the company accomplished in 1991 with their four-rotor 787B (2,622 cc/160 cu in- actual displacement, rated by FIA formula at 4,708 cc/287 cu in). The following year, a planned rule change at Le Mans made the Mazda 787B ineligible to race anymore. Mazda is also the most reliable finisher at Le Mans (with the exception of Honda, who has entered only three cars in only one year), with 67% of entries finishing.[citation needed]

The Mazda RX-7 has won more IMSA races in its class than any other model of automobile, with its one hundredth victory on September 2, 1990. Following that, the RX-7 won its class in the IMSA 24 Hours of Daytona race ten years in a row, starting in 1982. The RX7 won the IMSA Grand Touring Under Two Liter (GTU) championship each year from 1980 through 1987, inclusive.

Formula Mazda Racing features open-wheel race cars with Mazda Wankel engines, adaptable to both oval tracks and road courses, on several levels of competition. Since 1991, the professionally organized Star Mazda Series has been the most popular format for sponsors, spectators, and upward bound drivers. The engines are all built by one engine builder, certified to produce the prescribed power, and sealed to discourage tampering. They are in a relatively mild state of racing tune, so that they are extremely reliable and can go years between motor rebuilds.[1]

The Malibu Grand Prix chain, similar in concept to commercial recreational kart racing tracks, operates several venues in the United States where a customer can purchase several laps around a track in a vehicle very similar to open wheel racing vehicles, but powered by a small Curtiss-Wright rotary engine.

In engines having more than two rotors, or two rotor race engines intended for high-rpm use, a multi-piece eccentric shaft may be used, allowing additional bearings between rotors. While this approach does increase the complexity of the eccentric shaft design, it has been used successfully in the Mazda's production three-rotor 20B-REW engine, as well as many low volume production race engines. (The C-111-2 4 Rotor Mercedes-Benz eccentric shaft for the KE Serie 70, Typ DB M950 KE409 is made in one piece! Mercedes-Benz used split bearings.)

[edit] Aircraft engines

Diamond DA20 with Diamond Engines Wankel

Diamond DA20 with Diamond Engines Wankel
Sikorsky Cypher UAV powered with a UEL AR801 Wankel engine

Sikorsky Cypher UAV powered with a UEL AR801 Wankel engine

The first Wankel rotary-engine aircraft was the experimental Lockheed Q-Star civilian version of the United States Army's reconnaissance QT-2, basically a powered Schweizer sailplane, in 1968 or 1969. It was powered by a 185 hp (138 kW) Curtiss-Wright RC2-60 Wankel rotary engine.[19]

Aircraft Wankels have made something of a comeback in recent years. None of their advantages have been lost in comparison to other engines. They are increasingly being found in roles where their compact size and quiet operation is important, notably in drones, or UAVs. Many companies and hobbyists adapt Mazda rotary engines (taken from automobiles) to aircraft use; others, including Wankel GmbH itself, manufacture Wankel rotary engines dedicated for the purpose.[20][21]

Wankel engines are also becoming increasingly popular in homebuilt experimental aircraft, due to a number of factors. Most are Mazda 12A and 13B automobile engines, converted to aviation use. This is a very cost-effective alternative to certified aircraft engines, providing engines ranging from 100 to 300 horsepower at a fraction of the cost of traditional engines. These conversions first took place in the early 1970s. With a number of these engines mounted on aircraft, as of 10 December 2006 the National Transportation Safety Board has only seven reports of incidents involving aircraft with Mazda engines,[citation needed] and none of these is of a failure due to design or manufacturing flaws. During the same period they have issued several thousand reports of broken crankshafts and connecting rods, failed pistons and incidents caused by other components which are not found in the Wankel engines. Rotary engine enthusiasts derisively refer to piston aircraft engines as "reciprosaurs," and point out that their designs have remained essentially unchanged since the 1930s, with only minor differences in manufacturing processes and variation in engine displacement.

Peter Garrison, Contributing Editor for FLYING Magazine, has said that "the most promising engine for aviation use is the Mazda rotary." Mazdas have indeed worked well when converted for use in homebuilt aircraft. However, the real challenge in aviation is producing FAA-certified alternatives to the standard reciprocating engines that power most small general aviation aircraft. Mistral Engines, based in Switzerland, is busy certifying its purpose-built rotaries for factory and retro-fit installations on certified production aircraft. With the G-190 and G-230-TS rotary engines already flying in the experimental market, Mistral Engines hopes for FAA and JAA certification in 2007 or early 2008. Mistral claims to have overcome the challenges of fuel consumption inherent in the rotary, at least to the extent that the engines are demonstrating specific fuel consumption within a few points of reciprocating engines of similar displacement. While fuel burn is still marginally higher than traditional engines, it is outweighed by other beneficial factors.[22][23]

Since Wankel engines operate at a relatively high rotational speed with relatively low torque, propeller aircraft must use a Propeller Speed Reduction Unit (PSRU) to keep conventional propellers within the proper speed range. There are many experimental aircraft flying with this arrangement.

[edit] Other uses

Norton Interpol 2 Wankel prototype

Norton Interpol 2 Wankel prototype
Van Veen OCR1000

Van Veen OCR1000
UEL UAV-741 Wankel engine for UAV

UEL UAV-741 Wankel engine for UAV

Small Wankel engines are being found increasingly in other roles, such as go-karts, personal water craft and auxiliary power units for aircraft. The Graupner/O.S. 49-PI is a 1.27 hp (947 W) 5 cc Wankel engine for model airplane use which has been in production essentially unchanged since 1970; even with a large muffler, the entire package weighs only 380 grams (13.4 ounces).

The simplicity of the Wankel makes it ideal for mini, micro, and micro-mini engine designs. The MicroElectroMechanical Systems (MEMS) Rotary Engine Lab at the University of California, Berkeley has been developing Wankel engines of down to 1 mm in diameter with displacements less than 0.1 cc. Materials include silicon and motive power includes compressed air. The goal is to eventually develop an internal combustion engine that will deliver 100 milliwatts of electrical power; the engine itself will serve as the rotor of the generator, with magnets built into the engine rotor itself.

The largest Wankel engine was built by Ingersoll-Rand; available in 550 hp (410 kW) one rotor and 1100 hp (820 kW) two rotor versions, displacing 41 liters per rotor with a rotor approximately one meter in diameter, it was available between 1975 and 1985. It was derived from a previous, unsuccessful, Curtiss-Wright design, which failed because of a well-known problem with all internal combustion engines; the fixed speed at which the flame front travels limits the distance combustion can travel from the point of ignition in a given time, and thereby the maximum size of the cylinder or rotor chamber which can be used. This problem was solved by limiting the engine speed to only 1200 rpm and use of natural gas as fuel; this was particularly well chosen, as one of the major uses of the engine was to drive compressors on natural gas pipelines.

From 1974 to 1977 Hercules produced a limited number of motorcycles powered by Wankel engines. The tooling was later used by Norton to produce the Norton Commander model in the early 1980s. The best-known example of a Wankel-powered motorcycle, however, was the Suzuki RE5, produced in 1975 and 1976. This 500cc (actual) displacement motorcycle could have been a great touring bike except for the poor fuel mileage of 32-36 mpg. Examples are still frequently found on online auction sites.

Aside from being used for internal combustion engines, the basic Wankel design has also been utilized for air compressors, and superchargers for internal combustion engines, but in these cases, although the design still offers advantages in reliability, the basic advantages of the Wankel in size and weight over the four-stroke internal combustion engine are irrelevant. In a design using a Wankel supercharger on a Wankel engine, the supercharger is twice the size of the engine.

Perhaps the most exotic use of the Wankel design is in the seat belt pre-tensioner system of some Mercedes-Benz cars.[24] In these cars, when deceleration sensors sense a potential crash, small explosive cartridges are triggered electrically and the resulting pressurized gas feeds into tiny Wankel engines which rotate to take up the slack in the seat belt systems, anchoring the driver and passengers firmly in the seat before any collision.[25]

歡迎來到Bewise Inc.的世界,首先恭喜您來到這接受新的資訊讓產業更有競爭力,我們是提供專業刀具製造商,應對客戶高品質的刀具需求,我們可以協助客戶滿足您對產業的不同要求,我們有能力達到非常卓越的客戶需求品質,這是現有相關技術無法比擬的,我們成功的滿足了各行各業的要求,包括:精密HSS DIN切削刀具協助客戶設計刀具流程DIN or JIS 鎢鋼切削刀具設計NAS986 NAS965 NAS897 NAS937orNAS907 航太切削刀具,NAS航太刀具設計超高硬度的切削刀具醫療配件刀具設計汽車業刀具設計電子產業鑽石刀具木工產業鑽石刀具等等。我們的產品涵蓋了從民生刀具到工業級的刀具設計;從微細刀具到大型刀具;從小型生產到大型量產;全自動整合;我們的技術可提供您連續生產的效能,我們整體的服務及卓越的技術,恭迎您親自體驗!!

BW Bewise Inc. Willy Chen willy@tool-tool.com bw@tool-tool.com www.tool-tool.com skype:willy_chen_bw mobile:0937-618-190 Head &Administration Office No.13,Shiang Shang 2nd St., West Chiu Taichung,Taiwan 40356 http://www.tool-tool..com / FAX:+886 4 2471 4839 N.Branch 5F,No.460,Fu Shin North Rd.,Taipei,Taiwan S.Branch No.24,Sec.1,Chia Pu East Rd.,Taipao City,Chiayi Hsien,Taiwan

Welcome to BW tool world! We are an experienced tool maker specialized in cutting tools. We focus on what you need and endeavor to research the best cutter to satisfy users demand. Our customers involve wide range of industries, like mold & die, aerospace, electronic, machinery, etc. We are professional expert in cutting field. We would like to solve every problem from you. Please feel free to contact us, its our pleasure to serve for you. BW product including: cutting toolaerospace tool .HSS DIN Cutting toolCarbide end millsCarbide cutting toolNAS Cutting toolNAS986 NAS965 NAS897 NAS937orNAS907 Cutting Tools,Carbide end milldisc milling cutter,Aerospace cutting toolhss drillФрезерыCarbide drillHigh speed steelMilling cutterCVDD(Chemical Vapor Deposition Diamond )’PCBN (Polycrystalline Cubic Boron Nitride) Core drillTapered end millsCVD Diamond Tools Inserts’PCD Edge-Beveling Cutter(Golden FingerPCD V-CutterPCD Wood toolsPCD Cutting toolsPCD Circular Saw BladePVDD End Millsdiamond tool Single Crystal Diamond Metric end millsMiniature end millsСпециальные режущие инструментыПустотелое сверло Pilot reamerFraisesFresas con mango PCD (Polycrystalline diamond) ‘FreseElectronics cutterStep drillMetal cutting sawDouble margin drillGun barrelAngle milling cutterCarbide burrsCarbide tipped cutterChamfering toolIC card engraving cutterSide cutterNAS toolDIN or JIS toolSpecial toolMetal slitting sawsShell end millsSide and face milling cuttersSide chip clearance sawsLong end millsStub roughing end millsDovetail milling cuttersCarbide slot drillsCarbide torus cuttersAngel carbide end millsCarbide torus cuttersCarbide ball-nosed slot drillsMould cutterTool manufacturer.

Bewise Inc. www.tool-tool.com

ようこそBewise Inc.の世界へお越し下さいませ、先ず御目出度たいのは新たな

情報を受け取って頂き、もっと各産業に競争力プラス展開。

弊社は専門なエンドミルの製造メーカーで、客先に色んな分野のニーズ

豊富なパリエーションを満足させ、特にハイテク品質要求にサポート致します。

弊社は各領域に供給できる内容は:

(1)精密HSSエンドミルのR&D

(2)Carbide Cutting tools設計

(3)鎢鋼エンドミル設計

(4)航空エンドミル設計

(5)超高硬度エンドミル

(6)ダイヤモンドエンドミル

(7)医療用品エンドミル設計

(8)自動車部品&材料加工向けエンドミル設計

弊社の製品の供給調達機能は:

(1)生活産業~ハイテク工業までのエンドミル設計

(2)ミクロエンドミル~大型エンドミル供給

(3)小Lot生産~大量発注対応供給

(4)オートメーション整備調達

(5)スポット対応~流れ生産対応

弊社の全般供給体制及び技術自慢の総合専門製造メーカーに貴方のご体験を御待ちしております。

BW специализируется в научных исследованиях и разработках, и снабжаем самым высокотехнологичным карбидовым материалом для поставки режущих / фрезеровочных инструментов для почвы, воздушного пространства и электронной индустрии. В нашу основную продукцию входит твердый карбид / быстрорежущая сталь, а также двигатели, микроэлектрические дрели, IC картонорезальные машины, фрезы для гравирования, режущие пилы, фрезеры-расширители, фрезеры-расширители с резцом, дрели, резаки форм для шлицевого вала / звездочки роликовой цепи, и специальные нано инструменты. Пожалуйста, посетите сайт www.tool-tool.com для получения большей информации.

BW is specialized in R&D and sourcing the most advanced carbide material with high-tech coating to supply cutting / milling tool for mould & die, aero space and electronic industry. Our main products include solid carbide / HSS end mills, micro electronic drill, IC card cutter, engraving cutter, shell end mills, cutting saw, reamer, thread reamer, leading drill, involute gear cutter for spur wheel, rack and worm milling cutter, thread milling cutter, form cutters for spline shaft/roller chain sprocket, and special tool, with nano grade. Please visit our web www.tool-tool.com for more info.

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