Wankel engine: Definition from Answers.com

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Wankel engine


( väng ‘ kəl, ‘ -, wăng ‘ )

A rotary internal-combustion engine in a triangular rotor turning in a shaped housing performs the allotted to the pistons of a conventional thereby allowing great in weight and moving parts.



First KKM Engine NSU KKM 57P ( Kreiskolbenmotor ), at Autovision und Germany

In 1951, the German Felix Wankel began of the engine at NSU Motorenwerke AG. where he conceived his rotary engine in (DKM 54, Drehkolbenmotor ). The KKM 57 (the rotary engine, Kreiskolbenmotor ) was by NSU engineer Hanns Dieter in 1957 without the knowledge of Wankel, who remarked you have my race horse into a mare . [ 2 ] The first working DKM 54 was running on February 1, 1957 at the NSU and development department Versuchsabteilung TX . [ 3 ] It 21 horsepower; unlike modern engines, both the rotor and the rotated. [ 1 ] In 1960 NSU (the the inventor worked for) and the US Curtiss-Wright signed an agreement NSU would concentrate on the development of low and powered Wankel engines and would develop high Wankel Engines, including engines of which Curtiss-Wright had of experience designing and producing. [ 4 ]

effort went into rotary engines in the 1950s and They were of particular because they were and quiet running, and because of the resulting from their For a while, engineers faced they called chattered and devil’s scratches in the inner surface, they discovered the origin was in the apex seals a resonating vibration, and was solved by the thickness and weight of apex

Another early problem of of cracks in the stator surface was by installing the spark plugs in a metal piece instead of it directly into the block. [ needed ]. A later alternative to spark plug boss was provided by variable coolant scheme for water-cooled rotaries has had widespread use and was patented by Curtiss-Wright, [ 5 ] the last-listed for better air-cooled spark plug boss These approaches did not require a conductivity copper insert but did not the use.

Among the manufacturers signing agreements to develop Wankel were Alfa Romeo. Motors. Citroen. Ford. Motors. Mercedes-Benz. Nissan. Rolls-Royce.

Suzuki. and Toyota. [ 1 ] In the States, in 1959 under from NSU, Curtiss-Wright improvements in the basic engine In Britain, in the 1960s, Rolls Motor Car Division pioneered a diesel version of the Wankel [ 6 ]

Also in Britain, Norton developed a Wankel rotary for motorcycles. based on the Sachs Wankel that powered the W-2000 motorcycle, which was in their Commander and F1 ; Suzuki made a production motorcycle a Wankel engine, the RE-5, they used ferrotic apex seals and an NSU rotor in a attempt to prolong the engine’s In 1971 and 1972 Arctic Cat snowmobiles powered by 303cc rotary engines manufactured by in Germany. Deere Company a version that was capable of a variety of fuels. The design was as the power source for United Marine Corps combat and other equipment in the late [ 7 ]

Mazda and NSU signed a study to develop the Wankel engine in and competed to bring the first powered automobile to market. Mazda produced an experimental that year, NSU was first a Wankel automobile on sale, the NSU Spider in 1964; Mazda with a display of two and four Wankel engines at that Tokyo Motor Show. [ 1 ] In NSU began production of a Wankel-engined car, the Ro 80. [ 8 ] However, problems apex seal wear led to engine failure, which led to warranty costs for NSU, and further Wankel engine [ 1 ]

Mazda ‘s first engine, at the Mazda Museum in Japan

Mazda, however, to have solved the apex problem, and was able to run test at high speed for 300 hours failure. [ 1 ] After years of Mazda’s first Wankel car was the 1967 Cosmo 110S. The followed with a number of (rotary in the company’s terminology) including a bus and a pickup truck. often cited the cars’ of operation.

However, Mazda a method to comply with emission standards that, less expensive to produce, fuel consumption, just a sharp rise in fuel Mazda later abandoned the in most of their automotive but continued using it in their sports car until August (RX-7 importation for Canada with only the 1993 being sold. The USA ended the 1994 model year remaining unsold stock carried over as the ‘1995’

The company normally used designs, but the 1991 Eunos used a twin-turbo three-rotor In 2003, Mazda introduced the engine with the RX-8. The engine relocated the ports for and intake from the periphery of the housing to the sides, allowing for overall ports, better and further power gains.

Wankel engines had also intake and exhaust ports, but the was abandoned because of carbon in ports and side of rotor. The engine solved the problem by a keystone scraper side and approached the thermal distortion by adding some parts of ceramic. [ 9 ] The Renesis is capable of 238hp (177kW) with fuel economy, reliability, and friendliness than previous rotary engines, [ 10 ] all from a 1.3L displacement, however was not enough to keep up with more stringent emissions Mazda ceased production of Wankel engine in 2012 the engine failed to meet the 5 emission standard. [ 11 ]

In 1961, the Soviet research of NATI, NAMI and VNIImotoprom experimental development, and created engines with different [ 12 ]

Soviet automobile manufacturer also experimented with the use of engines in cars but without the of a license. [ 13 ] In 1974 they a special engine design which in 1978 designed an designated as VAZ-311. In 1980, the started delivering Wankel-powered (VAZ-411 engine with and Ladas. mostly to security of which about 200 were [ 14 ] [ 15 ] The next models were the and VAZ-415. Aviadvigatel. the Soviet engine design bureau, is to have produced Wankel with electronic injection for and helicopters, though little information has surfaced.

Although manufacturers licensed the design, Citroën with their M35 and GS using engines produced by General Motors. which to have concluded that the engine was slightly more to build than an equivalent engine, although claiming solved the fuel economy but failed in obtaining acceptable emissions, and Mercedes-Benz which it for their C111 concept only Mazda has produced engines in large numbers.

Motors (AMC) was so convinced . the rotary engine will an important role as a powerplant for and trucks of the future. , according to Roy D. Chapin Jr.. that the U.S. automaker signed an in February 1973, after a negotiations, to build Wankels for passenger cars and Jeeps. as as the right to sell any rotary it produces to other companies. [ 16 ] [ 17 ] The president, William Luneburg, did not dramatic development through but Gerald C. Meyers. AMC’s of the Product (Engineering) Group, that AMC would be buying the from Curtis-Wright before its own Wankel engines and predicted a transition to rotary power by [ 18 ] Plans called for the engine to be in the AMC Pacer. but development was pushed [ 19 ] [ 20 ] American Motors designed the Pacer around the engine, though by 1974, AMC had decided to buy the engines from GM instead of them itself. [ 21 ] Both GM and AMC the relationship would benefit in the new engine, and AMC claimed that Wankel achieved good economy. [ 22 ] However, GM’s had not reached production when the was to hit the showrooms.

Part of the demise of this was the 1973 oil crisis with fuel prices, and also about proposed US emission legislation. General Motors did not in having a Wankel engine both the emission requirements and good fuel economy, so in the company canceled its development, GM claimed having solved the economy problem and having engines with a duration 530,000 miles; unfortunately just published a few papers on the of their research. This the Pacer had to be reconfigured to house venerable AMC Straight-6 engine rear-wheel drive. [ 23 ]


The cycle. The A marks one of the three of the rotor. The B marks the eccentric and the white portion is the lobe of the shaft.

The shaft turns times for each rotation of the around the lobe and once for orbital revolution around the shaft.

In the Wankel engine, the strokes of a typical Otto occur in the space between a symmetric rotor and the inside of a The expansion phase of the Wankel is much longer than of the Otto cycle. [ 24 ] In the basic Wankel engine, the oval-like -shaped housing surrounds a which is triangular with flanks (often confused a Reuleaux triangle. [ 25 ] a three-pointed of constant width. but with the in the middle of each side a bit flattened). The theoretical shape of the between the fixed corners is the of a minimization of the volume of the geometric chamber and a maximization of the compression respectively. [ 24 ] The symmetric curve two arbitrary apexes of the rotor is in the direction of the inner housing with the constraint that it not the housing at any angle of rotation (an arc is not a of this optimization problem ).

The central drive shaft, the eccentric shaft or E-shaft, through the center of the rotor and is by fixed bearings. [ 26 ] The rotors on eccentrics (analogous to cranks) to the eccentric shaft (analogous to a The rotors both rotate the eccentrics and make orbital around the eccentric shaft.

at the corners of the rotor seal the periphery of the housing, dividing it three moving combustion [ 24 ] The rotation of each rotor on its own is caused and controlled by a pair of gears [ 26 ] A fixed gear on one side of the rotor housing a ring gear attached to the and ensures the rotor moves 1/3 turn for each turn of the shaft. The power output of the is not transmitted through the synchronizing [ 26 ] The force of gas pressure on the rotor (to a approximation) goes directly to the of the eccentric, part of the output

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

Note as that points A and B on the rotor and turn at different speeds—Point B 3 times as often as point A so that one full orbit of the equates to 3 turns of the e-shaft.

As the rotates and orbitally revolves, side of the rotor is brought to and then away from the of the housing, compressing and expanding the chamber like the strokes of a in a reciprocating engine. The power of the combustion stage goes the center of the offset lobe.

While a four-… piston makes one combustion … per for every two rotations of the crankshaft is, one-half power … per rotation per cylinder), each chamber in the Wankel generates one … per driveshaft rotation, one power … per rotor revolution and three power per rotor rotation. Thus, output of a Wankel engine is higher than that of a piston engine of similar displacement in a similar state of and higher than that of a piston engine of similar dimensions and weight.

Wankel also generally have a higher redline than a engine of similar power This is in part because the inherent in circular motion, but because they do not have stressed parts such as a or connecting rods. Eccentric do not have the stress-raising internal of crankshafts.

The redline of a rotary is limited by wear of the synchronizing [ citation needed ] Hardened gears are used for extended above 7000 or 8000rpm. Wankel engines in auto are operated above 10,000rpm. In they are used conservatively, up to or 7500rpm.

However, as gas pressure in seal efficiency, racing a engine at high rpm under no conditions can destroy the engine.

agencies that tax automobiles to displacement and regulatory bodies in racing variously consider the engine to be equivalent to a four-… of 1.5 to 2 times the displacement; some series ban it altogether. [ 27 ]


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