Wankel engine

[6] He realized that the triangular rotor of the rotary compressor could have intake and exhaust ports added producing an internal combustion engine.

[16] NSU development chief engineer Walter Froede solved this problem by using Hanns-Dieter Paschke's design and converting the DKM into what would later be known as the KKM (see figure 5.).

[4] The KKM proved to be a much more practical engine, as it has easily accessible spark plugs, a simpler cooling design, and a conventional power take-off shaft.

Richard Franz Ansdale, Wolf-Dieter Bensinger and Felix Wankel based their analogy on the number of cumulative expansion strokes per shaft revolution.

) is:[46][47][48] If power is to be derived from BMEP, the four-stroke engine formula applies: Eugen Wilhelm Huber, and Karl-Heinz Küttner counted all the chambers, since each one operates its own thermodynamic cycle.

[63] In contrast, four-stroke reciprocating engines perform these four strokes in one chamber, so that extremes of "freezing" intake and "flaming" exhaust are averaged and shielded by a boundary layer from overheating working parts.

[70] Toyota found that substituting a glow-plug for the leading site spark plug improved low rpm, part load, specific fuel consumption by 7%, and emissions and idle.

Ford tested a Wankel engine with the plugs placed in the side plates, instead of the usual placement in the housing working surface (CA 1036073 , 1978).

On a trial basis 40-octane gasoline was produced by BV Aral, which was used in the Wankel DKM54 test engine with a compression ratio of 8:1; it ran without complaint.

[94] Curtiss-Wright widened the rotor, keeping the rest of engine's architecture unchanged, thus reducing friction losses and increasing displacement and power output.

[90] Mazda's RX-8 car with the Renesis engine (that was first presented in 1999), met in 2004 the United States' low emissions vehicle (LEV-II) standard.

[113][108] As a hydrogen/air fuel mixture is quicker to ignite with a faster burning rate than gasoline, an important issue of hydrogen internal combustion engines is to prevent pre-ignition and backfire.

[122] As a rule of thumb, it may be assumed that a Wankel engine with a working chamber volume Vk of 500 cm3 and a compression of ε=9 runs well on mediocre-quality petrol with an octane rating of just 91 RON.

An injection system that allows stratified charge operation may help reduce rich mixture areas in undesirable parts of the engine, which improves fuel efficiency.

As an effect of this, the Wankel engine has slow and incomplete combustion, which results in high fuel consumption and bad exhaust gas behavior.

Flame travel occurs almost exclusively in the direction of rotor movement, adding to the poor quenching of the fuel and air mixture, being the main source of unburnt hydrocarbons at high engine speeds: The trailing side of the combustion chamber naturally produces a "squeeze stream" that prevents the flame from reaching the chamber's trailing edge, which worsens the consequences of the fuel and air mixture quenching poorly.

With the conventional one or two-spark-plug system and homogenous mixture, this squeeze stream prevents the flame from propagating to the combustion chamber's trailing side in the mid and high-engine speed ranges.

[133] Kawasaki dealt with that problem in its US patent US 3848574 ; Toyota obtained a 7% economy improvement by placing a glow-plug in the leading side, and using Reed-Valves in intake ducts.

[140] Mazda claimed to have solved the apex seal problem, operating test engines at high speed for 300 hours without failure.

The engine has petrol direct injection, exhaust gas recirculation, and an exhaust-gas treatment system with a Three-way catalyst and a particulate filter.

[153] By 1974, GM R&D had not succeeded in producing a Wankel engine meeting both the emission requirements and good fuel economy, leading to a decision by the company to cancel the project.

Because of that decision, the R&D team only partly released the results of its most recent research, which claimed to have solved the fuel-economy problem and built reliable engines with a lifespan above 530,000 miles (850,000 km).

[163] In November 2013, Mazda announced to the motoring press a series-hybrid prototype car, the Mazda2 EV, using a Wankel engine as a range extender.

[136] The car's Wankel engine is a naturally aspirated single-rotor unit with a chamber volume Vk of 830 cm3 (50.6 in3), a compression of 11.9, and a rated power output of 55 kW (74 hp).

[169] A former mechanic at Norton, Brian Crighton, started developing his own rotary engined motorcycles line named "Roton", which won several Australian races.

The first rotary engine aircraft was in the late-1960s in the experimental Lockheed Q-Star civilian version of the United States Army's reconnaissance QT-2, essentially a powered Schweizer sailplane.

[181] In Germany in the mid-1970s, a pusher ducted fan airplane powered by a modified NSU multi-rotor rotary engine was developed in both civilian and military versions, Fanliner and Fantrainer.

[182] At roughly the same time as the first experiments with full-scale aircraft powered with rotary engines, model aircraft-sized versions were pioneered by a combination of the well-known Japanese O.S.

In 1976, Road & Track reported that Ingersoll-Rand would develop a Wankel engine with a chamber volume Vk of 1,500 in3 (25 dm3) with a rated power of 500 hp (373 kW) per rotor.

[203] One of its products is the LDR (rotor recess in the leading edge of the combustion chamber) engine, which has better exhaust emissions profiles, and reed-valve controlled intake ports, which improve part-load and low rpm performance.