Wankel engine

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The Wankel engine is a type of internal combustion engine that uses an eccentric roll design to turn pressure into a rotating motion.

All parts rotate consistently in one direction, as opposed to a common reciprocating piston engine, which has a piston that changes direction roughly. In contrast to the more general reciprocal piston design, Wankel engines provide the advantage of simplicity, smoothness, compactness, high revolutions per minute, and a high power-to-weight ratio. This is primarily because three pulses of power per rotor revolution are generated compared to one per revolution in a two-stroke piston engine and one per two turns in a four-stroke piston engine. Though on the actual output axle, there is only one pulse of power per revolution, since the output shaft rotates three times faster than the actual rotor, as can be seen in the animation below, making it roughly equivalent to a two-stroke piston of the displacement same. This is also why the displacement measures only one rotor face, because only one face works for every output shaft revolution.

This machine is usually referred to as a rotary engine , although this name also applies to other completely different designs, especially aircraft engines with cylinders arranged in a circle around the crankshaft. The four-stage cycle of intake, compression, ignition, and exhaust occurs every revolution on each of the three rotor ends that move inside the oval-shaped epitrochoid housing, allowing three pulses per revolutionary power. The rotor is similar in the form of a Reuleaux triangle with a slightly flat side.

Video Wankel engine

Concepts and design

The design was conceived by German engineer Felix Wankel. Wankel received his first patent for the machine in 1929. He began development in the early 1950s at NSU, completing a working prototype in 1957. NSU then granted design licenses to companies around the world, who have been constantly adding improvements. The resulting machines are spark ignition, with a compression ignition engine built only in research projects.

The Wankel engine has a compact design advantage and low weight over the most common internal combustion engines used with reciprocating pistons. This excellence has provided rotary engine applications in a variety of vehicles and devices, including: cars, motorcycles, race cars, planes, go-karts, jet skis, snowmobiles, saws, and additional power units. The power-to-weight ratio has reached under one pound per horsepower on a particular machine.

Maps Wankel engine

History

Initial development

In 1951, NSU Motorenwerke AG in Germany started the development of the engine, with two models under construction. The first, DKM motor, was developed by Felix Wankel. Secondly, the KKM motor, developed by Hanns Dieter Paschke, was adopted as the basis of modern Wankel machines.

The basis of this type of DKM motor is that both rotors and housing rotate on a separate axis. DKM motors achieve higher revolutions per minute and are more naturally balanced. However, the machine must be disarmed to replace the spark plug and contain more parts. The KKM machine is simpler, has a fixed home.

The first working prototype, DKM 54, resulted in 21 hp (16 kW) and ran on 1 February 1957, in the research and development department of NSU Versuchsabteilung TX .

The KKM 57 (Wankel rotary engine, Kreiskolbenmotor ) was built by NSU engineer Hanns Dieter Paschke in 1957 without the knowledge of Felix Wankel, who later commented "You have turned my horse into a plow horse".

License issued

In 1960, the NSU, the company that employed two inventors, and the US company Curtiss-Wright, signed a joint agreement. NSU is concentrating on developing low power and medium-sized Wankel engines with Curtiss-Wright developing high-powered engines, including aircraft engines that Curtiss-Wright has decades of designing and producing experience. Curtiss-Wright recruited Max Bentele to head up their design team.

Many manufacturers sign licensing agreements for development, attracted by smoothness, fluency, and reliability derived from uncomplicated designs. Among these are Alfa Romeo, American Motors Company (AMC), Citroen, Ford, General Motors, Mazda, Mercedes-Benz, Nissan, Porsche, Rolls-Royce, Suzuki, and Toyota. In the United States in 1959, under license from NSU, Curtiss-Wright pioneered improvements in basic machine design. In Britain, in the 1960s, Rolls Royce Motor Car Division spearheaded a two-stage version of the Wankel engine.

CitroÃÆ'¡n did a lot of research, producing M35, GS Birotor and RE-2 helicopters, using a machine manufactured by Comotor, a joint venture of CitroÃÆ'¡n and NSU. General Motors seems to have concluded that Wankel engines are slightly more expensive to build than equivalent reciprocating machines. General Motors claims to have solved the fuel economy problem, but failed to get the same way for acceptable exhaust emissions. Mercedes-Benz installed the Wankel engine in their C111 concept car.

Deere & amp; The company designed a version capable of using various fuels. This design was proposed as a resource for United States Marine Corps fighter vehicles and other equipment in the late 1980s.

In 1961, the Soviet research organization NATI, NAMI, and VNIImotoprom initiated the development of creating experimental machines with different technologies. Soviet automaker AvtoVAZ is also experimenting in the design of the Wankel engine without a license, introducing a limited number of engines in several cars.

Despite much research and development around the world, only Mazda produces Wankel machines in large quantities.

Development for motorcycles

In the UK, Norton Motorcycles developed Wankel motorcycles for motorcycles, based on the Wankel air-cooled Sachs rotor that drives the DKW/Hercules W-2000 motorcycle. This two rotor engine is included in Commander and F1. Norton improves Sachs air cooling, introducing the courtroom. Suzuki also makes motorcycle production powered by Wankel engine, RE-5, using a ferroTiC alloy apex alloy and NSU rotor in a successful effort to extend engine life.

Development for cars

Mazda and NSU signed a study contract to develop the Wankel engine in 1961 and competed to bring Wankel's first car back into the market. Although Mazda produced Wankel's experiments that year, the first NSU with Wankel cars for sale, the sporty NSU Spider in 1964; Mazda responded by displaying two Wankel engines and four rotor at the Tokyo Motor Show that year. In 1967, the NSU started production of the Wankel-engined luxury car, the Ro 80. However, the NSU has not produced a reliable peak seal on the rotor, unlike the Mazda and Curtiss-Wright. The NSU had problems with wearing apex seals, poor shaft lubrication, and poor fuel economy, leading to frequent engine failures, unsolved until 1972, leading to enormous warranty costs restricting further development of the NSU Wankel engine. The early release of the new Wankel engine provided a bad reputation for all brands and even when the issue was solved on the last machine produced by the NSU in the second half of the 70s, sales were not recovered. Audi, after the takeover of the NSU, was built in 1979, a new KKM 871 engine with a side-intake port and 750 cc per chamber, 170 hp (130 kW) at 6,500 rpm and 220 Nm at 3,500 rpm. Engine mounted on the Audi 100 hull named "Audi 200", but not mass-produced.

Mazda, however, claims to have solved the apex seal problem, and operates the test machine at high speed for 300 hours without failure. After years of development, the first Mazda Wankel engine car was the 1967 Cosmo 110S. The company was followed by a number of Wankel vehicles ("turn" in company terminology), including bus and pickup trucks. Customers often mention the smooth operation of the car. However, Mazda chose a method to comply with hydrocarbon emissions standards which, though less expensive to produce, increased fuel consumption. Unfortunately for Mazda, it was introduced shortly before the sharp rise in fuel prices. Curtiss-Wright produces an RC2-60 engine that is comparable to a V8 engine in performance and fuel consumption. Unlike the NSU, in 1966 Curtiss-Wright had solved the rotor sealing problem with a seal along the 100,000 miles (160,000 km).

Mazda then abandoned Wankel in most of their automotive designs, continuing to use the engine in their only sports car range, producing the RX-7 until August 2002. Companies typically use two rotor designs. The more sophisticated twin-turbo three-rotor engine was installed in the 1991 Eunos Cosmo sports car. In 2003, Mazda introduced the Renesis engine mounted on the RX-8. Renesis engines move ports for disposal from swivel to side edges, allowing for larger overall ports, better airflow, and further power boost. Some early Wankel engines also have side exhaust ports, a concept that was abandoned due to carbon accumulation in ports and rotor sides. The Renesis engine solves the problem by using a side seal keystone scraper, and approaches the difficulty of thermal distortion by adding some parts made of ceramic. The Renesis is capable of 238 hp (177 kW) with improved fuel economy, reliability, and lower emissions than the previous Mazda rotary engine, all from 1.3a, liter displacement. However, this is not enough to meet tighter emission standards. Mazda ended production of its Wankel engine in 2012 after the engine failed to meet the improved Euro 5 emission standards, without leaving the automotive company selling Wankel-powered vehicles. The company continues the development of the next generation Wankel engine, the SkyActiv-R with the new rear-wheel sports car model announced in October 2015 even without a given launch date. Mazda states that SkyActiv-R solves three major problems with previous rotary engines: fuel economy, emissions, and reliability. Mazda announced the introduction of the hybrid-style Mazda2 EV car using Wankel engine as a range extender; however, no introductory date was announced.

American Motors Corporation (AMC), the smallest US automaker, is so confident "... that the rotary engine will play an important role as a powerhouse for future cars and trucks...", whose chairman, Roy D. Chapin Jr., signed agreement in February 1973, after a year's negotiations, to build Wankels for both passenger cars and Jeep, as well as the right to sell any rotary machine produced to other companies. The president of American Motors, William Luneburg, did not expect dramatic developments until 1980. However, Gerald C. Meyers, AMC's vice president of product engineering group, suggested that AMC must buy engines from Curtiss-Wright before developing its own Wankel engine, and forecast the total transition to turning power in 1984. Plans called for machines to be used in AMC Pacer, but development was pushed back. American Motors designed a unique Pacer around the engine. In 1974, AMC decided to buy General Motors Wankel instead of building a machine at home. Both General Motors and AMC affirm relations will be beneficial in marketing the new engines, with AMC claiming that General Motors' Wankel achieved good fuel economy. However, the General Motors engine has not reached production when Pacer was launched into the market. The 1973 oil crisis played a role in the annoying use of the Wankel engine. Rising fuel prices and talking about proposed US emissions standards also add to concerns.

In 1974, General Motors R & amp; D did not succeed in producing Wankel engines that meet emission requirements and good fuel economy, leading the decision by the company to cancel the project. Because of the decision, the R & amp; D only partially released the latest research results, which claimed to have solved the fuel economy problem, as well as building reliable engines with a lifespan of over 530,000 miles (850,000 km). The findings were not taken into account when the cancellation order was issued. The termination of the General Motors Wankel project requires AMC to reconfigure Pacer to house a straight-six AMC-powered engine to drive the rear wheels.

In 1974, the Soviet Union created a special machine design firm, which in 1978 devised a machine designed as "VAZ-311". In 1980, the company started delivery of the Wankel twin-rotor VAZ-411 engine in the VAZ-2106s and Lada cars, with about 200 produced. Most of the production goes to security services. The next models are VAZ-4132 and VAZ-415. Aviadvigatel, the Soviet aircraft engine design agency, is known to have produced Wankel engines with electronic injection for aircraft and helicopters, although little specific information emerged.

Ford melakukan penelitian dalam mesin Wankel, menghasilkan paten yang diberikan: GB 1460229 Â , 1974, metode untuk membuat rumah; US 3833321 Â 1974, pelapis pelat samping; US 3890069 Â , 1975, pelapisan perumahan; CA 1030743 Â , 1978: Perataan rumah; CA 1045553 Â , 1979, perakitan Reed-Valve. Pada tahun 1972, Henry Ford II menyatakan bahwa rotary mungkin tidak akan menggantikan piston di "masa hidup saya".

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Desain

In the Wankel engine, four blows of Otto cycle piston engines occur in the space between the three-sided symmetrical rotor and the interior of the housing. In every Wankel engine rotor, an oval-like epitrochoid housing surrounds a triangular rotor with arc-shaped sides (often confused with the Reuleaux triangle, a constant three-point width curve, but with a bulge in the center of each side a bit more flat). The theoretical form of the rotor between fixed angles is the result of minimizing the volume of the geometric combustion chamber and the maximization of the compression ratio, respectively. The symmetric curve connecting the two improper apexes of the rotor is maximized toward the inner form of the house with the limitation that it does not touch the housing at any rotation angle (the arc is not the solution of this optimization problem).

The central drive shaft, called the "eccentric shaft" or "axis E", passes through the center of the rotor and is supported by a fixed bearing. The rotor rises on the eccentric (analog to crankpins) integral to the eccentric shaft (analogous to the crankshaft). The rotor both revolves around the eccentric and makes an orbital revolution around the eccentric shaft. Seal at the rotor angle of the seal against the housing edge, divide it into three combustion chamber moves. The rotation of each rotor on its own axis is caused and controlled by a pair of synchronized tooth gears fixed to one side of the housing rotor attaching the ring gear attached to the rotor and ensuring the rotor is moving exactly 1/3 of a turn for each rotor. turn of the eccentric shaft. Engine power output is not transmitted through synchronized gears. The rotor moves in a rotary motion guided by an eccentric gear and shaft, not guided by external space; The rotor should not rub against the external housing engine. The extended gas pressure force on the rotor provides pressure to the eccentric central portion of the output shaft.

The easiest way to visualize the action of the machine in the animation on the left is to not see the rotor itself, but a cavity is created between it and the housing. The Wankel machine is actually a progressive cavity system with variable volumes. So, there are three cavities per house, all repeating the same cycle. Points A and B on the rotor and the E-shaft rotate at different speeds - point B is circular three times more often than point A, so that a full rotor orbit equals three rounds of E-shaft.

When the rotors rotate horizontally, each side of the rotor is brought closer to and then away from the housing wall, compressing and expanding the combustion chamber like a piston stroke in a reciprocating piston engine. The power vector of the combustion stage passes through the center of the offset hole.

While a four-stroke piston engine completes one stroke of combustion per cylinder for every two crankshaft rotations (ie, one-half stroke power per crankshaft rotation per cylinder), each combustion chamber in Wankel produces one combustion blow per driveshaft rotation, which is one power stroke per rotor orbital revolution and three stroke forces per rotation of the rotor. Thus, the power output of the Wankel engine is generally higher than that of a four-stroke piston engine of the same engine displacement in the same aligned state; and higher than a four-stroke piston engine that has similar physical dimensions and weights.

Wankel engines are generally capable of achieving much higher engine speeds than reciprocating engines with the same power output. This is partly due to the smoothness attached to the circular motion, and the fact that the "engine" rpm is an output shaft 1.5 times faster than the oscillating part. Eccentric axes do not have the stress contours associated with crankshafts. The maximum revolution of the rotary engine is limited by the load of the tooth on the synchronization equipment. Hardened steel gears are used for extended operations above 7000 or 8000 rpm. Mazda Wankel engine in racing cars operated above 10,000 rpm. On the plane they are used conservatively, up to 6500 or 7500 rpm. However, since the gas pressure participates in seal efficiency, racing the Wankel engine at high rpm in no-load conditions can damage the engine.

National agencies that impose vehicle taxes according to the movements and regulatory bodies in auto racing in various ways assume Wankel engines are equivalent to four-step piston engines of 1.5 to 2 times the displacement of one chamber per rotor, although there are three lobes per rotor (since the rotor only completes the rotation 1/3 per 1 rotation of the output shaft, so that there is only one power that works per output revolution, the other two lobes simultaneously incur costs incurred and incorporate new ones, rather than contributing to the power output of the revolution). Some racing series have banned Wankel altogether, along with all other alternatives to traditional four-stroke piston reciprocating designs due to the perceived advantages of design in racing applications.

Engineering

Felix Wankel managed to overcome most of the problems that made the previous rotary engine fail by developing a configuration with a propeller seal that has a radius of the tip equal to the number of "greatness" of the rotor housing, compared with theoretical epitrokoid, to minimize radial apex seal motion plus by inserting apex gas-loaded cylinder pin that binds all the sealing elements to seal about three planes on each apex rotor.

In the early days, dedicated dedicated production machines had to be built for different residential dimensions arrangements. However, patented designs such as AS. Patent 3,824,746 , G.. J. Watt, 1974, for "Wankel Machine Cylinder Machine", AS. Patent 3,916,738 , "Equipment for machining and/or surface treatment trochoidal" and AS. Patents 3,964,367 , "Devices for machining the inside walls of trochoidal", and others, solving the problem.

The rotary engine has problems that are not found on a four-step reciprocating piston engine because the block houses have intake, compression, combustion, and disposal that occur in fixed locations around the housing. Instead, the reciprocating engine performs these four blows in one space, making it the extreme of "freezing" the intake and "light up" the average exhaust and shielded by the boundary layer of the overheated work section. The use of heat pipes in the air-cooled Wankel was proposed by the University of Florida to address the uneven warming of the block house. Pre-heating certain housing parts with exhaust gases improves performance and fuel economy, also reduces wear and emissions.

The shield boundary layer and the oil film act as thermal insulation, leading to low-temperature lubricant film (maximum ~ 200 ° C or 392 ° F on water-cooled Wankel machine) providing a more constant surface temperature. with the temperature in the engine combustion chamber reciprocating.With cooling circular or axial flow, the temperature difference can still be tolerated.

Problems arose during research in the 1950s and 1960s. For a while, the engineers were confronted with what they called "chats of chatter" and "demon strokes" on the surface of the inner epithrocho. They found that the cause was the apex seal reaching resonant vibrations, and the problem was solved by reducing the thickness and weight of the apex seal. Scratches disappeared after the introduction of more compatible materials for seals and housing coatings. Another initial problem is the buildup of cracks in the surface of the stator near the plug hole, which is removed by plugging spark plugs on the metal sleeves/copper sleeves separated in the house instead of spark plugs screwed directly into the block house. Toyota found that replacing light plugs for leading site sparks boosted low rpm, partial loads, specific fuel consumption by 7%, as well as emissions and idle. An alternative solution later for boss spark plug coolers is provided with a variable cooling speed scheme for water-cooled rotary, widely used, patented by Curtiss-Wright, with the latter listed for better air-cooled engine boss spark plugs. cooling. This approach does not require high conductivity copper inserts, but does not preclude its use. Ford tested a rotary engine with plugs placed in the side plate instead of the usual placement on the housing work surface ( CA 1036073 Ã, , 1978).

The four-stroke reciprocating engine is not very suitable for use with hydrogen fuel. Hydrogen can be jammed in hot parts such as exhaust valves and spark plugs. Another problem concerns the hydrogenic attack on the lubricant film in the reciprocating machine. In the Wankel engine, this problem is circumvented by using apical ceramic seals on the ceramic surface, so that no oil film is subjected to hydrogenation. Piston shells should be lubricated and cooled with oil. This substantially increases lubricant oil consumption in four-stroke hydrogen engines.

Improving the displacement and rotary engine power by adding more rotor to the base design is simple, but the limit may exist in the number of rotor, since the power output is channeled through the last rotor shaft, with all the pressure of the entire engine present at that time. For machines with more than two rotor, the installation of two rotor bi-rotor by a jagged coupling between two sets of rotor has been successfully tested.

Research in the UK under the SPARCS (Self-Pressurizing-Air Rotor Cooling System) project, found that stability and economy were secretly obtained by supplying a combustible mixture only to one rotor in a multi-rotor engine in a forced air-forced rotors. , similar to Norton air-cooled design.

Wankel engine weaknesses of inadequate lubrication and cooling in ambient temperatures, short engine life, high emissions and low fuel efficiency are handled by rotary engine specialist David Garside, who developed three patented systems in 2016.

• SPARCS
• Compact-SPARCS
• CREEV (Rotary Machine Compound for Electric Vehicles)

SPARCS and Compact-SPARCS provide superior heat rejection and efficient thermal equilibrium to optimize lubrication. The problem with a rotary engine is that the engine house has a cold, hot surface permanently when walking. It also generates excessive heat inside the engine that breaks the lubricant quickly. The SPARCS system reduces this widespread difference in the heat temperature in the metal from the engine house, and also cools the rotor from within the engine body. This results in reduced wear and tear of the machine to extend engine life. As described in Unmanned Systems Technology Magazine, "SPARCS uses a closed rotor cooling circuit composed of circulating centrifugal fans and heat exchangers to reject heat, this is self-pressure by catching the blow-by across the rotor-side gas rotor from the workspace." CREEV is a 'disposal reactor', containing a shaft & amp; rotor inside, from different shapes to Wankel rotor. The reactor, located in the exhaust stream outside the engine combustor, consumes non-combustible waste products without using a second ignition system before directing the burning gas into the exhaust pipe. Horsepower is given to the reactor shaft. Lower emissions and better fuel efficiency are achieved. All three patents are currently licensed to UK-based engineers, AIE (UK) Ltd.

Materials

Unlike piston engines, where the cylinder is heated by the combustion process and then cooled by the incoming charge, the Wankel rotor housing is constantly heated on one side and cooled on the other, leading to high local temperatures and unequal heat expansion. While this places great demands on the materials used, Wankel's simplicity makes it easier to use alternative materials, such as exotic alloys and ceramics. With cooling water in the direction of radial or axial flow, and hot water from the hot arc heats the cold arc, thermal expansion remains tolerable. The highest engine temperature has been reduced to 129 ° C (232 ° F), with the maximum temperature difference between engine parts of 18 ° C (32 ° F) by using heat pipes in the vicinity of the housing and on the side plate as a means cooler.

Among the alloys cited for the use of Wankel housing are A-132, Inconel 625, and 356 which are handled with T6 violence. Some materials have been used for residential work surface plating, Nikasil into one. Citroen, Mercedes-Benz, Ford, A P Grazen and others apply for patents in this field. For apex seals, material choices have evolved with experience gained, from carbon alloys to steel, ferrotik, and other materials. The combination of residential coating and apex and side seal materials was determined experimentally, to get the best duration of both seals and house cover. For the shaft, alloy steel with slight deformation at the load is preferred, the use of Maraging steel has been proposed for this.

Leaded gasoline is the dominant type available in the first years of Wankel engine development. Lead is a solid lubricant, and leaded petrol is designed to reduce seal and home use. The first machine has an oil supply calculated by considering the quality of the gasoline lubricant. When leaded petrol is being removed, the Wankel engine requires an increased oil mix in gasoline to provide lubrication to important engine parts. Experienced users advise, even in machines with electronic fuel injection, add at least 1% of the oil directly to gasoline as a precaution if the pumps supplying the oil to the associated parts of the combustion chamber fail or are inhaled in the air. An SAE paper by David Garside extensively describes the choice of material and the Norton cooling fins.

Some approaches involving solid lubricants are tested, and even the addition of MoS2, at a rate of 1 cc (1 mL) per liter of fuel, is recommended (LiquiMoly). Many engineers agree that the addition of oil to gasoline as in the old two-stroke engine is a safer approach to engine reliability than an oil pump injected into the intake system or directly to parts that require lubrication. A combined oil pump plus fuel oil is always possible.

Sealing

Early machine designs have a high sealing loss incident, both between the rotor and the housing and also among the various pieces that make up the housing. Also, in the previous Wankel engine model, carbon particles could be trapped between seals and casing, jamming the engine and requiring partial redevelopment. It is common for early Mazda engines that require rebuilding after 50,000 miles (80,000 km). Further sealing problems arise from uneven heat distribution within the home causing distortion and loss of sealing and compression. This thermal distortion also causes uneven wear between apex seals and rotor housing, seen in higher mileage engines. The problem is compounded when the machine is pressed before it reaches the operating temperature. However, Mazda's rotary engine solves this initial problem. The machine currently has nearly 100 sections associated with the seal.

The cleaning problem for the apex heat rotor passing between the axial side houses closer to the cold intake lobe area is handled by the axial rotor pilot axial radial inboard oil seal, plus an increase in oil cooling inertia from the interior rotor (CW US 3261542 Ã, , C. Jones, 5/8/63, US 3176915 Ã, , M. Bentele, C. Jones, AH Raye, 7/2/62), and a slightly crowned "peak seal" (different heights in the middle and at the extremes of the seal).

Fuel economy and emissions

Wankel's combustion chamber is more resistant to preignition operations on gasoline with lower octane values ​​than comparable piston engines. The shape of the combustion chamber can also cause relatively incomplete combustion of air fuel. This will produce large amounts of unburned hydrocarbons released into the exhaust. However, the exhaust is relatively low in NOx emissions, because combustion temperatures are lower than in other machines, and also due to some inherent flue gas recirculation (EGR) on the starting engine. Sir Harry Ricardo pointed out in 1920 that for every 1% increase in the proportion of flue gas in admixture, there is a 7 Â ° C flame temperature reduction. This allowed Mazda to comply with the United States Clean Air Act of 1970 in 1973, with its simple and inexpensive "thermal reactor", which is an enlarged space in the exhaust manifold. By reducing the air-fuel ratio, the unburned hydrocarbon (HC) in the exhaust will support combustion in the thermal reactor. A piston engine car requires an expensive catalytic converter to handle hydrocarbons and non-combustible NOx emissions. This inexpensive solution increases fuel consumption, which is already a weak point for Wankel's engine, and the 1973 oil crisis raises the price of gasoline. Toyota found that air injection into the exhaust port zone improves fuel economy and reduces emissions. The best results are obtained with a hole in the side plate; doing it in the sewer has no real effect. The use of a three-stage catalyst, with a central air supply, such as for two-stroke piston engines, also proved useful.

Mazda has improved thermal reactor fuel system efficiency by 40% when the RX-7 was introduced in 1978. However, Mazda has finally switched to a catalytic converter system. According to the Curtiss-Wright study, the factor that controls the amount of unburned hydrocarbons in the exhaust is the rotor surface temperature, with higher temperatures producing less hydrocarbons. Curtiss-Wright also shows that the rotor can be widened, keeping the rest of the machine architecture unchanged, thus reducing friction losses and increasing displacement and power output. The limiting factor for this widening is mechanical, especially the deflection of the shaft at high rotation speed. Quenching is the dominant source of hydrocarbons at high speed, and leaks at low speeds.

Automobile Wankel rotary engine capable of performing high-speed operation. However, it does show that early opening of intake ports, longer intake tracts, and greater rotor eccentricity can increase torque at low rpm. The shape and position of the recess in the rotor, which forms the bulk of the combustion chamber, affects emissions and fuel economy. Outcomes in terms of fuel economy and exhaust emissions vary depending on the shape of the combustion alcove determined by the placement of spark plugs per individual engine booths.

Mazda RX-8 cars with Renesis engines meet California State's fuel economy requirements, including California's low emissions vehicle (LEV) standards. This is achieved by a number of innovations. The exhaust port, which at the beginning of Mazda's rotation is located in the rotor house, is moved to the combustion side of the chamber. This solves the problem of the previous ash buildup in the machine, and the problem of thermal distortion from the side of the intake and exhaust port. The scraper seal is added at the rotor side, and some ceramic parts are used in the machine. This approach allows Mazda to eliminate the overlap between the input openings and the exhaust openings, while simultaneously increasing the exhaust port area. The side port traps unburned fuel in the chamber, reduces oil consumption, and improves stability of combustion in low-speed and light load ranges. The HC emission from the Wankel Engine port exhaust side is 35-50% less than that coming from the Wankel engine peripheral disposal port, since virtually zero intake and flue ports open overlap. Peripheral ported rotary engines have significantly better effective pressures, especially at high rpm and with rectangular intake ports. However, the RX-8 is not fixed to meet the Euro 5 emission regulations and was discontinued in 2012.

Mazda is continuing development of next generation Wankel engine. The company is researching the engine's ignition ignition, which removes conventional plugs, direct fuel injection, and light-weight HCCI ignition. This leads to greater rotor excentricity (equivalent to longer strokes in reciprocating engines), with reduced elasticity and low spin-per-minute torque. The study by T. Kohno proved that installing a light plug in the combustion chamber increases the partial load and the low revolution per minute fuel economy by 7%. This innovation promises to increase fuel consumption and emissions. To improve fuel efficiency further, Mazda sees Wankel using as a range-extender in series hybrid cars, announcing the prototype, Mazda2 EV, for a press evaluation in November 2013. This configuration improves fuel efficiency and emissions. As a further advantage, running a Wankel engine with a constant speed gives the engine a larger life. Keeping constant, or narrow, constant, or greatly reducing waves, many losses from the Wankel machine.

In 2015 the new system to reduce emissions and improve fuel efficiency with Wankel Engines was developed by UK-based engineer AIE (UK) Ltd, after a licensing agreement to utilize the patent of rotary engine maker Norton, David Garside. The CREEV system uses a secondary rotor to extract energy from the exhaust, consumes non-combustion products while expansion occurs at the secondary rotor stage, thereby reducing overall emissions and fuel costs by recovering the exhaust energy it should become defeated. By extending exhaust gases to near atmospheric pressure, Garside also ensures the engine drain will remain cooler and quieter. AIE (UK) Ltd is now using this patent to develop hybrid power units for cars and unmanned aerial vehicles.

Laser ignition

The traditional spark plugs need to be inserted into the wall of the combustion chamber to allow the top of the rotor to sweep past. When the rotor peak seal passes through the spark plug, a small amount of compressed charge can disappear from the cargo space to the exhaust chamber, feeding the fuel into the exhaust, reducing efficiency, and producing higher emissions. These points have been overcome by using laser ignition, eliminating the traditional spark plugs and removing narrow gaps in the motor housing so that the apex rotor seals can be fully swept without loss of compression from adjacent spaces. This concept has precedents in the incandescent plug used by Toyota (SAE paper 790435), and SAE 930680 paper, by D. Hixon et al., On 'Plug Glow Catalytic in JDTI Stratified Charge Rotary Engine'. The laser plug can shoot through a narrow gap. Laser plugs can also shoot deep into the combustion chamber using multiple lasers. Direct fuel injection, compatible with Wankel engines, combined with laser ignition on single or dual laser plugs, has been shown to increase motor further reduce losses.

Ignition of homogeneous charge compression

The ignition of homogeneous charge compression (HCCI) involves the use of a mixture of pre-mixed air fuel that is compressed to the point of automatic ignition, so that the ignition of the electronic spark is removed. The gasoline engine combines a homogeneous charge (HC) with spark ignition (SI), abbreviated as HCSI. The diesel engine combines a stratified charge (SC) with compression ignition (CI), abbreviated as SCCI. HCCI engines achieve engine-like gasoline emissions with efficiency compression such as engine ignition, and low nitrogen oxide (NO x) emission levels without catalytic converters. However, unburned hydrocarbon and carbon monoxide emissions still require treatment to conform to automotive emission regulations.

Mazda has conducted research on HCCI ignition for its SkyActiv-R rotation engine project, using research from SkyActiv Generation 2. The rotary engine constraint is the need to find spark plugs outside the combustion chamber to allow the rotor to pass through. Mazda confirmed that the problem has been solved in the SkyActiv-R project. Rotary generally has a high compression ratio, making it particularly suitable for HCCI use.

Rotary ignition compression

There has been research on compression ignition engines and diesel fuel combustion in rotation using spark ignition. The basic design parameters of the Wankel engine prevent a higher compression ratio of 15: 1 or 17: 1 in practical machines, but continuous efforts are made to produce Wankel ignition compression. The Rolls-Royce and Yanmar compression-ignition approach is using a two-stage unit, with one rotor acting as a compressor, while combustion takes place in the other. Conversion of standard 294 cc spark plug unit per chamber to use heavy fuel is described in SAE 930682 paper, by L. Louthan. The SAE 930683 paper, by D. Eiermann, produces the SuperTec Wankel line from the compression ignition rotary engine.

Research of compression ignition engine is being done by Pratt & amp; Whitney Rocketdyne, commissioned by DARPA to develop the Wankel ignition compression engine for use in the prototype VTOL flying car called "Transformer". The engine, based on a previous concept involving an unmanned aerial vehicle called "Endurocore", is supported by Wankel's diesel. plans to use Wankel rotors of various sizes on a common eccentric shaft to improve efficiency. This machine is claimed as a full compression engine, full expansion, ignition-compression engine. Patents October 28, 2010 by Pratt & amp; Whitney Rocketdyne, describes a shallow Wankel engine similar to the early Rolls-Royce prototype, requiring an external air compressor to achieve sufficiently high compression for cycle-burning combustion. The design is different from rotary-ignition rotary Rolls-Royce, mainly by proposing injectors both in the drain between the rotor combustor and the rotor expansion stage, and the injector in the expansion rotor expansion chamber, for 'afterburning'.

The British company Rotron, which specializes in unmanned engine engine applications (UAVs) from Wankel engines, has designed and built a unit to operate on heavy fuel for NATO purposes. The engine uses ignition spark plugs. The main innovation is fire propagation, ensuring the flame burns smoothly throughout the combustion chamber. The fuel is heated to 98 degrees Celsius before being injected into the combustion chamber. Four spark plugs are used, aligned in two pairs. Two spark plugs light the fuel charge on the front of the rotor as it moves into the burning part of the house. When the rotor drives the fuel charge, two seconds of second fraction flame behind the first pair of plugs, triggering near the back of the rotor behind the fuel charge. The drive shaft is water cooled which also has a cooling effect on the internal rotor. Cooling water also flows around the external engine through a gap in the housing, thereby reducing engine heat from outside and inside removing hot spots.

Benefits

The main advantages of Wankel engine are:

• The power-to-weight ratio is much higher than the piston engine
• About one-third the size of a piston engine of equivalent power output
• It's easier to pack in a small machine room than an equivalent piston machine
• No reciprocating section
• Can achieve higher revolutions per minute than piston engines
• Operates almost without vibration
• Not vulnerable to machine taps
• It's cheaper to mass-produce, because the machine contains fewer sections
• Superior breathing, burning power in 270 degree rotation mainshaft rather than 180 degree in piston machine
• Supply torque about two-thirds of the combustion cycle rather than a quarter for a piston engine
• Wider range of speeds provide greater adaptability
• Can use wider octane rating fuel
• Does not suffer from a "scale effect" to limit its size.
• On some Wankel engines, the fl ows remain uncontaminated by the combustion process, so no oil changes are required. The oil in the main shaft is completely enclosed from the combustion process. Oil for Apex seal and separate karter lubrication. In a piston engine, crankcase oil is contaminated by blow-by combustion through a piston ring.

The Wankel engine is much lighter and simpler, containing far fewer moving parts than a piston engine with equivalent power output. Valve valves or complex valves are eliminated by using simple ports cut into the rotor house wall. Since the rotor runs directly on a large bearing on the output shaft, there is no connecting rod and no crankshaft. Mutual mass recall, and removal of the most stressed and failed piston engine parts, provide high reliability of Wankel engine, smoother power flow, and a higher power-to-weight ratio.

The surface-to-volume ratio in the combustion chamber moves so complex that direct comparisons can not be made between a reversed piston engine and a Wankel engine. The flow rate and heat loss are very different. The characteristics of surface temperature are completely different; oil film in Wankel machine acts as an isolation. Machines with higher compression ratios have a worse surface to volume ratio. The surface-to-volume ratio of the reciprocating piston piston engine is much poorer than the reciprocating piston gasoline engine, but the diesel engine has a higher efficiency factor. Therefore, comparing power output is a realistic metric. The reciprocating piston engine with the same power as Wankel will be approximately twice that of the displacement. When comparing power-to-weight ratio, physical size or physical weight with piston engine of equal power output, Wankel is superior.

The four-stroke cylinder generates power only on each round of the crankshaft, with three punch pumping losses. This doubles the real surface-to-volume ratio for four-stroke reciprocating and increased displacement piston engines. The Wankel, therefore, has higher volumetric efficiency and pumps lower losses through the absence of a choking valve. Due to the quasi-overlap of stroke forces, which leads to the smoothness of the engine and avoid the four-stroke cycle in the reciprocating engine, Wankel's engine very quickly reacts to increasing power, delivering fast power delivery. when demand arises, especially at higher rpm. This difference is more pronounced when compared to the four-cylinder reciprocating engine and less prominent when compared with the higher number of cylinders.

In addition to the removal of internal reciprocating pressure by the complete removal of the internal parts of reciprocating normally found in piston engines, the Wankel engine is built with an iron rotor in an aluminum housing, which has a larger thermal expansion coefficient. This ensures that even Wankel's overheated engines can not be confiscated, as is possible with overheated piston engines. This is a substantial safety benefit when used in airplanes. In addition, the absence of valves and valve trains improves security. GM tested iron rotor and iron house in their prototype Wankel machine, which works at higher temperatures with lower specific fuel consumption.

A further advantage of the Wankel engine for use in an aircraft is that it generally has a smaller frontal area than an equivalent power piston engine, allowing a more aerodynamic nose to be designed around the engine. The advantage of cascade is that the smaller size and lower weight of the Wankel engine allow savings in the cost of airframe construction, compared to piston engines with comparable strength.

Wankel engines operating within their original design parameters are almost immune to catastrophic failure. Wankel engines that lose compression, or cooling or oil pressure, will lose a significant amount of power and fail in a short time. However, it will usually continue to generate some power during that time, allowing a safer landing when used in aircraft. Piston engines under the same conditions tend to grab or break parts, which will almost certainly lead to engine failure, and the loss of all forces instantly. For this reason, the Wankel machine is perfect for snowmobiles, which often leads users to remote places where failure can lead to frostbite or death, and on airplanes, where sudden failure is likely to cause accidents or forced landings in remote areas.

From the shape and features of the combustion chamber, Wankel engine octane fuel requirements are lower than reciprocal piston engines. The maximum number of octane path requirements is 82 for the intake-peripheral wankel port machine, and less than 70 for the side-inlet port engine. From the point of view of oil refiners this might be an advantage in fuel production costs.

Because the stroke duration is 50% longer than the four-lap engine, there is more time to complete the combustion. This leads to greater suitability for direct fuel injection and multilevel filling operations. The Wankel rotary engine has a stronger air-fuel mixture and longer operating cycles than the reciprocating engine, achieving complete mixing of hydrogen and air. The result is a homogeneous mixture and no hot spots in the machine, which are essential for hydrogen combustion.

Losses

Although in two dimensions the Wankel seal system looks simpler than the corresponding multi-cylinder piston engine, in three dimensions, the reverse is true. As well as the apex rotor seal clearly in the conceptual diagram, the rotor must also be sealed against the end of the chamber.

The piston ring in the reciprocating engine is not a perfect seal; each has a gap to allow for expansion. Sealing at the top of Wankel's rotor is less important, due to leakage between adjacent spaces in adjacent strokes of the cycle, not to the case of the main shaft. Although sealing has increased over the years, ineffective Wankel sealing, largely due to lack of lubrication, remains a factor that reduces efficiency.

In the Wankel engine, the air-fuel mixture can not be stored before because there is a consecutive cycle of intake. The engine has a stroke duration 50% longer than the reciprocating piston engine. Otto Otto last cycle 1080 Â ° for Wankel engine (three output shaft rotation) versus 720 Â ° for four-stroke reciprocating engine, but four strokes still the same proportion of total.

There are various methods of calculating engine displacement from Wankel. The Japanese regulation to calculate displacements for engine ratings uses the displacement of one rotor volume only, and the automotive industry typically accepts this method as a standard for calculating rotation. When compared to the specific output, however, the convention produces a large imbalance in favor of the Wankel motor. The initial revision approach is to assess the displacement of each rotor as twice the space.

Wankel rotary engine and piston engine displacement, and the corresponding power, output can be more accurate than the displacement per eccentric shaft revolution. A calculation of this form specifies that two Wankel rotors replacing 654 cc per face will have a displacement of 1.3 liters per each eccentric shaft rotation (only two total faces, one face per rotor with full power strike) and 2.6 liters after two rounds (four total faces, two faces per rotor have full power strokes). The result is directly proportional to the 2.6 liter piston engine with the same number of cylinders in the conventional combustion order, which will also replace 1.3 liters through its power after one round of the main shaft, and 2.6 liters through its strength after two revolutions of the mainshaft. A Wankel rotary engine is still a four-cycle engine, and pumping losses from non-power strokes is still valid, but the absence of throttling valves and 50% longer stroke duration result in significantly lower pumping losses compared to four-stroke reciprocating piston engines. Measuring Wankel's rotary engine in this way more accurately describes its specific output, since the volume of air fuel mixture introduced through a complete power stroke per revolution is directly responsible for the torque, and thus the power generated.

The back side of the engine combustion chamber develops a squeeze stream that pushes the back of the flame. With one or two conventional spark-plug systems and homogeneous mixtures, this flue stream prevents the flame from spreading to the trailing side of the combustion chamber at medium and high engine speed ranges. Kawasaki deals with the issue in US patent US 3848574 , and Toyota gets a 7% economic boost by placing plug-glow on leading sites, and using Reed-Valves on intake channel. This poor combustion on the back side of the chamber is one of the reasons why there is more unburned carbon monoxide and hydrocarbon in the Wankel waste stream. A port-side exhaust, as used in Mazda Renesis, avoids one of these causes because an unburned mixture can not escape. Mazda 26B avoids this problem through the use of three spark plug ignition systems. (At 24 hours Le Mans endurance race in 1991, 26B has significantly lower fuel consumption than competing reciprocating piston engines.All competitors have the same amount of fuel due to the Le Mans limited fuel supply rule.)

Peripheral intake ports provide the highest average effective pressure; however, the introduction of the side intake results in a more stable idle, as it helps prevent blow-back of the burning gas into the intake tract causing "misfirings", caused by alternating cycles in which the mixture converges and fails to ignite. Peripheral porting (PP) provides the best average effective pressure across the entire range of rpm, but PP is also associated with worse idle stability and partial load performance. Toyota's initial work led to the addition of fresh air supply to the exhaust port, and it proved also that the Reed-valve on the port or intake channel enhances the performance of the rpm rotation and partial load of the Wankel engine, preventing blow-back from exhaust gas into the ports and intake tract, and subtract the wrong EGR from pressing, at the expense of a slight loss of power at the top rpm. David W. Garside, the developer of the Norton rotary engine, which proposed the earlier opening of the intake port before the upper dead center (TDC), and longer inclusion channels, increased the low rpm torque and Wankel engine elasticity. It was also described in Kenichi Yamamoto's book. Elasticity is also enhanced by greater rotor eccentricity, analogous to longer strokes in reciprocating engines. Wankel machines operate better with low pressure exhaust systems. Higher exhaust pressure back reduces meaningful, more severe pressure in peripheral intake port machines. The Mazda RX-8 Renesis engine improves performance by doubling the exhaust port area compared to the previous design, and there are specific studies on the effect of intake and exhaust piping configuration on Wankel engine performance.

All Mazda's Wankel rotaries, including Renesis found on the RX-8, burn a small amount of oil by design, measured into the combustion chamber to maintain the apex seal. Owners should periodically add a small amount of oil, thus increasing operational costs. Some sources, such as rotaryeng.net, claim that better results come with the use of an oil-in-fuel mix rather than an oil metering pump. Liquid-cooled engines require multigrade mineral oil for cold starters, and Wankel engines require heating time before full load operation as performed by reciprocating engines. All engines show oil loss, but rotary engines are engineered with sealed motors, unlike piston engines that have oil film splashed on cylinder walls to lubricate them, then oil "control" rings. The oil-losing machine has been developed, eliminating many oil lubrication problems.

src: paul-ryan.info

Apps

Auto racing

In the racing world, Mazda has had great success with two rotor cars, three rotor, and four rotor. The personal racer also has success with stocking and modifying the Mazda Wankel-engine car.

The Sigma MC74 powered by the Mazda 12A engine is the first and only engine team from outside Western Europe or the United States to complete the entire 24 hours of the 24 Hour race of Le Mans, in 1974. Yojiro Terada is the driver of the MC74. Mazda is the only team from outside Western Europe or the United States that has won Le Mans directly and the only non-piston machine that ever won Le Mans, which the company achieved in 1991 with four of their 787B rotor (2,622 L or 160 cuÃ, in - displacement actual, rated by FIA formulas at 4,708 L or 287 cuÃ, in).

Formula Mazda Racing has an open wheel racing car with Mazda Wankel engine, which can be adapted to oval tracks and road courses, at several levels of competition. Since 1991, the professionally managed Star Mazda Series has become the most popular format for sponsors, viewers, and driving drivers

Source of the article : Wikipedia