A rotary engine is an internal combustion engine, like the engine in your car, but it works in a completely different way than the conventional piston engine. In a piston engine, the same volume of space (the cylinder) alternately does four different jobs i.e. intake, compression, combustion and exhaust. A rotary engine does these same four jobs, but each one happens in its own part of the housing. It's kind of like having a dedicated cylinder for each of the four jobs, with the piston moving continually from one to the next chamber.
The rotor and housing of a rotary engine from the Mazda RX-7. These parts replace the pistons, cylinders, valves, connecting rods and camshafts founds in piston engine.
Like a piston engine, the rotary engine uses the pressure created when a combination of air and fuel is burned. In a piston engine, that pressure is contained in the cylinders and forces pistons to move back and forth. The connecting rods and crankshaft convert the reciprocating motion of the pistons into rotational motion that can be used to power a car.
In a rotary engine, the pressure of combustion is contained in a chamber formed by part of the housing and sealed in by one face of the triangular rotor, which is what the engine uses instead of pistons. The rotor follows a path that looks like something you'd create with a Spiro graph. This path keeps each of the three peaks of the rotor in contact with the housing, creating three separate volumes of gas. As the rotor moves around the chamber, each of the three volumes of gas alternatively expands and contracts. It is this expansion and contraction that draws air and fuel into the engine, compresses it and makes useful power as the gases expand and then expels the exhaust. The rotary engine (originally conceived and developed by Dr. Felix Wankel) is sometimes called a Wankel Engine or Wankel Rotary
The Parts of a Rotary Engine
A rotary engine has an ignition system and a fuel-delivery system that are similar to the ones on piston engines. But it has many different parts such as Rotor, housing, Output- shaft etc.
1) Rotor :
The rotor has three convex faces, each of which acts like a piston. Each face of the rotor has a pocket in it, which increases the displacement of the engine, allowing more space for air/fuel mixture.
At the apex of each face is a metal blade that forms a seal to the outside of the combustion chamber. There are also metal rings on each side of the rotor that seal to the sides of the combustion chamber.
The rotor has a set of internal gear teeth cut into the center of one side. These teeth mate with a gear that is fixed to the housing. This gear mating determines the path and direction of the rotor takes through the housing.
The housing is roughly oval in shape (its actually epitrochoid in shape (check out this is a Java demonstration of how the shape is derived). The shape of the combustion chamber is designed so that the three tips of the rotor will always stay in contact with the wall of the chamber, forming three sealed volumes of gas.
Each part of the housing is dedicated to one part of the combustion process. The four sections are:
- Intake
- Compression
- Combustion
- Exhaust
The intake and exhaust ports are located in the housing. There are no valves in these ports. The exhaust port connects directly to the exhaust, and the intake port connects directly to the throttle.
HOUSING OF ROTARY ENGINE
RotoThe housings provide the outer envelope of the working chambers. The shape of the housing is that of a two lobe peritrochoid, and the inner surface is coated to withstand wear from the rotor apex seals. The most apparent feature of a rotor housing is the peripheral exhaust port, which carries away spent combustion gasses. Also worth noting are the two spark plug holes. The top one is called the Trailing spark plug and the lower one is the Leading spark plug. While the leading plug does most of the "work", the trailing spark plug helps "clean-up" the combustion in the long chamber. You can read more about this in the Ignition section. All the round holes lengthwise through the housing are for Tension Bolts that hold the engine together. The larger, non-round holes through the housing are the water jacket, where coolant flows. Tubular Dowels also run through the housings lengthwise and serve as internal oil passages. The Oil Injection Bung on top of the housing provides a means for the oil injectors to lubricate the apex seals. There is a small hole in the trochoid surface through with the oil flows. This kind of lubrication is necessary because, unlike a piston in a cylinder, both sides of the seal are exposed to combustion so oil cannot be sprayed on the "back-side".
3) Output Shaft
The output shaft has round lobes mounted eccentrically, meaning that they are offset from the centerline of the shaft. Each rotor fits over one of these lobes. The lobe acts sort of like the crankshaft in a piston engine. As the rotor follows its path around the housing, it pushes on the lobes. Since the lobes are mounted eccentric to the output shaft, the force that the rotor applies to the lobes creates torque in the shaft, causing it to spin.
How It's Put Together
A rotary engine is assembled in layers. The two-rotor engine we took apart has five main layers that are held together by a ring of long bolts. Coolant flows through passageways surrounding all of the pieces. The two end layers contain the seals and bearings for the output shaft. They also seal in the two sections of housing that contain the rotors. The inside surfaces of these pieces are very smooth, which helps the seals on the rotor do their job. An intake port is located on each of these end pieces.
One of the two end pieces of a two-rotor Wankel engine
The next layer in from the outside is the oval-shaped rotor housing, which contains the exhaust ports. This is the part of the housing that contains the rotor.
The part of the rotor housing that holds the rotors and shows the exhaust port location
In the center of each rotor is a large internal gear that rides around a smaller gear that is fixed to the housing of the engine. This is what determines the orbit of the rotor. The rotor also rides on the large circular lobe on the output shaft.
Rotary engines use the four-stroke combustion cycle, which is the same cycle that four-stroke piston engines use. But in a rotary engine, this is accomplished in a completely different way.
The heart of a rotary engine is the rotor. This is roughly the equivalent of the pistons in a piston engine. The rotor is mounted on a large circular lobe on the output shaft. This lobe is offset from the centerline of the shaft and acts like the crank handle on a winch, giving the rotor the leverage it needs to turn the output shaft. As the rotor orbits inside the housing, it pushes the lobe around in tight circles, turning three times for every one revolution of the rotor. As the rotor moves through the housing, the three chambers created by the rotor change size. This size change produces a pumping action. Let's go through each of the four stokes of the engine looking at one face of the rotor.
1) Intake
The intake phase of the cycle starts when the tip of the rotor passes the intake port. At the moment when the intake port is exposed to the chamber, the volume of that chamber is close to its minimum. As the rotor moves past the intake port, the volume of the chamber expands, drawing air/fuel mixture into the chamber. When the peak of the rotor passes the intake port, that chamber is sealed off and compression begins.
2) Compression
As the rotor continues its motion around the housing, the volume of the chamber gets smaller and the air/fuel mixture gets compressed. By the time the face of the rotor has made it around to the spark plugs, the volume of the chamber is again close to its minimum. This is when combustion starts.
3) Combustion
Most rotary engines have two spark plugs. The shape of the combustion chamber is long, so the flame would spread too slowly if there were only one plug. When the spark plugs ignite the air/fuel mixture, pressure quickly builds, forcing the rotor to move.
The pressure of combustion forces the rotor to move in the direction that makes the chamber grow in volume. The combustion gases continue to expand, moving the rotor and creating power, until the peak of the rotor passes the exhaust port.
4) Exhaust
Once the peak of the rotor passes the exhaust port, the high-pressure combustion gases are free to flow out the exhaust. As the rotor continues to move, the chamber starts to contract, forcing the remaining exhaust out of the port. By the time the volume of the chamber is nearing its minimum, the peak of the rotor passes the intake port and the whole cycle starts again.
The neat thing about the rotary engine is that each of the three faces of the rotor is always working on one part of the cycle in one complete revolution of the rotor, there will be three combustions stokes. But remember, the output shaft spins three times for every complete revolution of the rotor, which means that there is one combustion stroke for each revolution of the output shaft.
Firing Circle of the Wankel Rotary Engine
In the Wankel engine all the cycle goes on in all three chambers simultaneously. Fig shows the suction, compression, power and exhaust cycles considering the single inlet of air-fuel mixture.
| | | | |
| Suction: As the tip of the rotor passes the inlet port, the petrol/air mixture enters the following chamber, which is increased in size because of the rotors eccentric orbit as the rotor rolls around the central gear. | Compression: As the rotor continues to revolve, the chamber containing the mixture decreases in size and the mixture is compressed. | Power: Spark plugs ignite the mixture. Ignition causes the mixture to burn and expand, imparting energy to the rotor for its power `stroke' as the size of the chamber increases. | Exhaust: The leading lobe passes the exhaust port and leaves it open for the burnt out gases to escape. |
Wankel has a fixed casing. The output shaft turns at 3 times the rotor speed. The three rotor tips are continuously in touch with the internal surface. Between the three sides of the rotor and the inside of the casing are three working spaces, or chambers, each of which alternately expands and contracts in size as the rotor orbits'. Hence there are three power strokes for each rotor revolution. Although most Wankel engines have a carburettor, some have been operated with fuel injection. The Wankel is essentially a water-cooled engine with oil-cooling for the rotor.
The Principle:
The principle of working is similar to the 4 stroke car engine. The petrol/air mixture enters and is compressed. Into this compression is ignited a spark (power stroke) which burns the mixture causing it to expand as gas. This energy of expansion turns the triangular rotor, which in turn turns the central gear. The central gear turns the shaft which turns the flywheel. The turning of the flywheel goes through various gears and finally turns the wheels. All these combined with the fact that there are three power strokes for each revolution (since the cycle goes on in all three chambers simultaneously) makes the Wankel engine tremendously powerful for its size.
In order to make the rotary engine work as an internal combustion engine, the four processes of intake, compression, combustion and exhaust had to be performed in succession in the working chamber. Suppose that the triangular shaped rotor were concentrically placed inside a true circular housing. In this case, the working chamber would not vary in volume as the rotor turned inside the housing. Even if the fuel-air mixture were ignited there, the expansion pressure of combustion gas would merely work toward the center of the rotor and would not result in rotation. That was why the inner periphery of the housing was contoured as a trochoid-shape and assembled with the rotor installed on an eccentric shaft. As such, the working chamber changes in volume twice per revolution and the four processes of the internal combustion engine could be achieved.
| Typical Wankel Engine with twin rotors | ||
| | Two rotors are combined in an engine to develop greater power. They are correctly phased for smoothest running. Rotors are 180 degrees to each other for best mechanical balance. | |
Key Differences
There are several defining characteristics that differentiate a rotary engine from a typical piston engine.
Fewer Moving Parts:
The rotary engine has far fewer moving parts than a comparable four-stroke piston engine. A two-rotor rotary engine has three main moving parts: the two rotors and the output shaft. Even the simplest four-cylinder piston engine has at least 40 moving parts, including pistons, connecting rods, camshaft, valves, valve springs, rockers, timing belt, timing gears and crankshaft
This minimization of moving parts can translate into better reliability from a rotary engine. This is why some aircraft manufacturers (including the maker of Skycar) prefer rotary engines to piston engines.
Smoother:
All the parts in a rotary engine spin continuously in one direction, rather than violently changing directions like the pistons in a conventional engine do. Rotary engines are internally balanced with spinning counterweights that are phased to cancel out any vibrations.
The power delivery in a rotary engine is also smoother. Because each combustion event lasts through 90-degrees of the rotor's rotation, and the output shaft spins three revolutions for each revolution of the rotor, each combustion event lasts through 270-degrees of the output shaft's rotation. This means that a single-rotor engine delivers power for three-quarters of each revolution of the output shaft. Compare this to a single-cylinder piston engine, in which combustion occurs during 180-degrees out of every two revolutions, or only a quarter of each revolution of the crankshaft (the output shaft of a piston engine).
Slower:
Since the rotors spin at one-third the speed of the output shaft, the main moving parts of the engine move slower than the parts in a piston engine. This also helps with reliability.
Challenges
There are some challenges in designing a rotary engine:
- Typically, it is more difficult (but not impossible) to make a rotary engine meet U.S. emissions regulations.
- The manufacturing costs can be higher, mostly because the number of these engines produced is not as high as the number of piston engines.
- They typically consume more fuel than a piston engine because the thermodynamic efficiency of the engine is reduced by the long combustion-chamber shape and low compression ratio and high emission of exhaust gases..
Advantages of wankel-Engine over piston Engine
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 with equivalent power), but it also completely eliminates the reciprocating mass of a piston engine with its internal strain and inherent vibration due to repetitious 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 due to the elimination of this reciprocating strain on internal parts, the construction of the engine, with an iron rotor within a housing made of aluminum which has greater thermal expansion, ensures that even when grossly overheated the Wankel engine will not seize, as an overheated piston engine is likely to do; this is a substantial safety benefit in aircraft use.
The simplicity of design and smaller size of the Wankel engine also allow for a savings in construction costs, compared to piston engines of comparable power output.
As another advantage, the shape of the Wankel combustion chamber and the turbulence induced by the moving rotor prevent localized hot spots from forming, thereby allowing the use of fuel of very low octane number without preignition or detonation, a particular advantage for Hydrogen cars. This feature also led to a great deal of interest in the Soviet Union, where high octane gasoline was rare.
Disadvantages of wankel Engine over piston Engine
The design of the Wankel engine requires numerous sliding seals and a housing that is typically built as a sandwich of cast iron and aluminum pieces that expand and contract by different degrees when exposed to heating and cooling cycles in use. These elements led to a very high incidence of loss of sealing, both between the rotor and the housing and also between the various pieces making up the housing. Further engineering work by Mazda brought these problems under control, but the company was then confronted with a sudden global concern over both hydrocarbon emission and a rise in the cost of gasoline, the two most serious drawbacks of the Wankel engine.
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. At first, 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 paradoxically enriching the air/fuel mixture enough to produce an exhaust stream which was rich enough in hydrocarbons to actually support complete combustion in a 'thermal reactor' (just 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.
Unfortunately for Mazda, their switch to this solution was immediately followed by a sharp rise in the cost of gasoline worldwide, so that not only the added fuel cost of their 'thermal reactor' design, but even the basically lower fuel economy of the Wankel engine caused sales to drop alarmingly.
A related cause for unexpectedly poor fuel economy involves an inherent weakness of the Wankel rotor design when used with conventional fuels. Some studies have indicated that at high speeds, the rate at which the volume of the combustion chamber increases in the moments after ignition actually outpaces the expansion of the burning fuel. The result is that, at high speeds, less useful energy is extracted from the same volume of fuel, as the exhaust has to expend time and energy "catching up" to the rotor before it can accomplish any work.
A typical production two-rotor Wankel engine does not utilise a bearing between the two rotors, allowing a one-piece eccentric shaft to be used. This tradeoff allows for cheaper manufacture at the expense of peak engine rpm, due to eccentric shaft flex. In engines having more than two rotors, or two rotor race engines intended for high-rpm use, a multi-piece eccentric shaft must 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.
Many disadvantages of the Wankel engine have been solved in the Renesis engine of the RX-8. 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. Fuel consumption is now within normal limits while passing California State emissions requirements
Comparison with a traditional reciprocating engine
In order to get the turning force, both the reciprocating engine and the rotary engine rely on the expansion pressure created by the combustion of the fuel-air mixture. The difference between the mechanisms of the two engines is in the way that the expansion pressure is used. In the reciprocating engine, the expansion pressure generated above the piston's top surface forces the piston down and the mechanical force is transferred to the connecting rod that causes rotation of the crankshaft.
In the case of the rotary engine, however, the expansion pressure is applied to the flank of the rotor. One of the three sides of a triangle is forced toward the center of the eccentric shaft as a result. (PG in the figure). This movement consists of two divided forces. One being the force toward the output shaft center (Pb in the figure) and the other is the tangential force (Ft) that rotates the output shaft.
The inside space of the housing (or the trochoid chamber) is always divided into three working chambers. Due to the turning of the rotor, those three working chambers are always in motion and successively execute the four processes of intake, compression, ignition (or combustion) and exhaust inside the trochoid chamber. Each process is carried out in a different place in the trochoid chamber. This is significantly different from the reciprocating engine, where the four processes are carried out within each cylinder.
The displacement volume of the rotary engine is generally expressed by the unit chamber volume and by the number of rotors. For example, with the model 13B two-rotor engine, the displacement volume is shown as "654cc × 2".
The unit chamber volume means the difference between the maximum volume and the minimum volume of a working chamber, while the compression ratio is defined as the ratio between the maximum volume and the minimum volume. The same definitions are used for the reciprocating engine.
In the figure shown on the last page, the changes of the working chamber volume of the rotary engine and the four-cycle reciprocating engine are compared. Although, in both engines, the working chamber volume varies smoothly in a wave shape, there are two distinctive differences between the two engines. One difference is the turning angle per process. The reciprocating engine turns 180 degrees while the rotary engine turns 270 degrees, one and half times that of the reciprocating engine. In other words, in the reciprocating engine, the crankshaft (output shaft) makes two turns (720 degrees) during the four processes, while in the rotary engine, the eccentric shaft (output shaft) makes three turns (1080 degrees) while the rotor makes one turn. In this way, the rotary engine has a longer process time, causes less torque fluctuation and results in smooth operation.
Furthermore, even in high-speed running, the rotor's rpm is comparatively slower, thus, the more relaxed timing constraints of the intake and the exhaust processes facilitate the development of systems aimed at attaining higher performance.
Unique attributes of the Wankel-type rotary engine
1) Small size and lightweight: The rotary engine has several advantages but the most important ones are reduced size and weight. Where the two-rotor layout is considered equivalent to the inline six-cylinder reciprocating engine in quietness and smoothness of operation, the rotary engine can be designed to be two-thirds of the weight and size while achieving the same level of output. This advantage is very attractive to automobile designers especially in light of the recent trends toward stricter requirements in crashworthiness (collision safety), aerodynamics, weight distribution and space utility.
2) A simple structure: As the rotary engine converts the expansion pressure of the burnt fuel-air mixture directly into the turning force of the triangular rotor and the eccentric shaft, there is no need for connecting rods. The intake and exhaust ports are opened and closed by the rotor movement itself. The valve mechanism which includes the timing belt, the camshaft, the rocker arm, the valve, the valve spring, etc. required in the reciprocating engine is not required, and a rotary engine can therefore be built with far fewer parts.
3) Flat torque characteristics: The rotary engine has a rather flat torque curve throughout the whole speed range. According to research results, torque fluctuations during operation are at the same level as an inline six-cylinder reciprocating engine even with the two-rotor design, and a three-rotor layout is smoother than a V8 reciprocating engine.
4) Quieter, with less NVH: With the reciprocating engine, piston motion itself is a source of vibration, while the valve train generates unwanted mechanical noises. The smooth turning motions of the rotary engine generate considerably less vibration and the absence of a valve actuating mechanism contributes to smooth and quiet operation.
5) Reliability and Durability: The rotor turns at one-third of the engine speed. Therefore, when the rotary engine runs at speeds of 9000 rpm, the rotor is turning at approximately one third that rate. In addition, since the rotary engine doesn't have such high-speed moving parts as rocker arms and connecting rods, it is more reliable and durable under high load operations. This was demonstrated by the overall win at Le Mans in 1991.
Types of Rotary Engines made by Mazda:
All Mazda Wankel "rotary" engines are essentially a single family - they all derive from the first Wankel experiments in the early 1960s (Wankel was a German Engineer). Over the years, displacement has been increased (somewhat), and turbo charging has been added to great effect. This is the engine family that made Mazda famous.
Wankel engines can be classified by their rotor size in terms of width (diameter) and depth (thickness). These metrics function similarly to the bore and stroke measurements of a piston engine. Nearly all Mazda production Wankel engines share a single rotor diameter: 105 mm (4.1 in) with a 15 mm (0.6 in) crankshaft offset. The only engine to diverge from this formula was the rare 13A, which used a 120 mm (4.7 in) diameter and 17.5 mm (0.7 in) offset.
Types os rotary engine:
Latest Research on Rotary Engine
1) Renesis: The future of the rotary engine
RENESIS, which stands for "The RE (rotary engine)'s GENESIS( origin or mode formation).
For rotary engine enthusiasts, the next exciting phase in the great engine's history has already begun. At the Tokyo Motor Show in October 1999, Mazda unveiled the RX-Evolv, a concept vehicle which later evolved into the MAZDA RX-8 four-door, four-seat sports car unveiled in January 2001 at the North American International Auto Show (NAIAS) in Detroit. The Evolv and the MAZDA RX-8 shared many advances in common, not the least of which was the latest version of the rotary engine called "RENESIS."
The MAZDA RX-8 with its RENESIS rotary engine will make its debut in 2003.
When developing the RENESIS, Mazda's engineers aimed to retain power output on a par with the turbocharged 13B-REW, the rotary engine that powers the Mazda RX-7, while offering improved fuel economy and reduced emissions
The RX-8 is built to accommodate Mazda's RENESIS rotary engine, an ideal power plant for sports cars. It is powerful, smooth, lightweight and compact, and it has a low center of gravity.
"RENESIS," derived from the word "genesis," suggests the beginning of a new type of rotary engine. Mazda's work on rotary engines began in 1961 and, six years later, we introduced the Cosmo Sport, powered by the world's two-rotor engine. Over the years, we made countless improvements. Today The rotary engine is used in the turbocharged RX-7 that we sell in Japan. Through 2000, we have sold about 1.8 million cars rotary engine-powered cars.
The RENESIS is an advanced version of the MSP-RE(multi side port rotary engine) concept rotary engine featured in the RX-01 concept sports car exhibited at the 1995 Tokyo Motor Show. This new-generation rotary engine was employed in the RX-EVOLV four-passenger sports car shown first at the 1999 Tokyo Motor Show.
When developing the RENESIS, we aimed to retain power output on a par with the turbocharged 13B-REW, the rotary engine that powers the RX-7, while offering improved fuel economy and reduced emissions.
Side Intake and Exhaust Ports :Unlike previous mass-production rotary engines, which employed side exhaust ports and peripheral intake ports, the naturally aspirated RENESIS has intake and exhaust ports in the side housings. This configuration eliminates overlap between the opening of the intake and exhaust ports, enhancing combustion efficiency. The intake ports are 30% larger and their timing has been changed to make them open sooner than in previous designs. Moreover, the exhaust ports open later, resulting in a longer power (expansion) stroke and providing radically improved heat efficiency.
At the same time, the RENESIS uses a six-port induction (6PI) design, in which each rotor employs three intake ports, and a variable intake timing mechanism. Under this system, dedicated high-speed intake ports begin to operate when the engine operates at high-rev levels. This makes it possible to use the intake's dynamic effect at high and low speeds to maximize compression efficiency.
Unlike the single peripheral port per rotor of previous designs, the RENESIS uses two exhaust ports per rotor. This produces a combined exhaust port opening area nearly twice as large and results in a substantial reduction in exhaust resistance.
The rotors have also been made lighter for better performance at high-rev levels. The rotors used in the RENESIS weigh approximately 14% less than those used in the engine that powers the RX-7, which we sell in Japan.
These enhancements provide high output rivaling the power of turbocharged rotary engines with linear power characteristics from the low- to the high-rev range.
Fuel Efficiency :The increased heat efficiency resulting from zero overlap between the opening of the intake and exhaust ports makes it possible for the RENESIS to run on a leaner fuel mixture than conventional rotary engines. When idling, the RENESIS consumes 40% less fuel than the current production rotary engine.
Reciprocating piston engines generally use a richer fuel mixture under high-speed and high-load conditions to prevent knocking. In contrast, rotary engines do not require a particularly rich fuel mixture under these conditions due to their special combustion characteristics. In addition, the RENESIS achieves nearly complete combustion over the entire speed range thanks to its high compression ratio and the use of new fuel injectors designed for improved fuel atomization. These enhancements allow the RENESIS to run on a leaner fuel mixture than conventional rotary engines from the low to the high-rev range. The result is the power and performance of a sports car engine and reduced fuel consumption. Low Emissions
Due to their configurations, rotary engines produce less nitroxide (NOx) than reciprocating piston engines, but they also tend to produce large amounts of unburned hydrocarbons. The side exhaust layout used in the RENESIS prevents unburned hydrocarbons of the combustion chamber housing from escaping to the exhaust ports.
Instead, they are carried over and burned in the next combustion cycle, dramatically reducing emissions. In addition, air injection directed into the combustion chamber increases the efficiency of the exhaust reaction, significantly over Mazda's existing system during engine startup. Together with the double-skin exhaust manifold, the new layout makes the exhaust much hotter when it reaches the catalytic converter, speeding the converter reaction for clean emissions from the moment the engine is started.
Reduced Oil Consumption:In a rotary engine, oil is supplied directly to the interior walls of the combustion chamber to lubricate the "apex" and "corner" seals. We've kept the paths which supply oil in the RENESIS as small as possible, and we have redesigned the oil supply nozzles to improve their efficiency. With these enhancements, the RENESIS consumes about half as much oil as a conventional rotary engine.
Superb Response and Sound to Thrill the Senses:The RENESIS achieves a sophisticated balance between high revolutions and high output on the one hand and fuel economy and low emissions on the other. In addition, we are working to enhance the performance and to realize the high degree of reliability and durability required in a mass-production sports car. We want to achieve output of 250 horsepower.
Unlike rotary engines equipped with peripheral exhaust ports, the side layout of the RENESIS produces clear, transparent high tones and powerful low tones. We recognize engine sound as a key element in any sports car, and we are working to ensure that the engine produces a satisfying roar as you depress the accelerator.
2) Mazda RX-8 Renesis Hybrid
Mazda debuted its RX-8 RE hybrid stands for Renesis Hydrogen Rotary Engine at the 2003 Tokyo Motor Show. The Renesis is an electronically-controlled direct-injection rotary engine with a high-pressure hydrogen fuel tank. The RX-8 Renesis also runs on gasoline as well, making the Mazda car the first and only rotary hybrid as well as the first and only rotary hydrogen-gasoline hybrid in the world.
| Pictured right is the Mazda RX-8 RE. | |
According to Mazda, "The RENESIS Hydrogen Rotary Engine incorporates an electronically-controlled hydrogen injector system (the hydrogen is injected in a gaseous state). The system draws air from the side port during the induction cycle and uses dual hydrogen injectors in each of the engine's twin rotor housings to directly inject hydrogen into the intake chambers. By virtue of its construction, with separate chambers for induction and combustion, the rotary engine is ideally suited to burn hydrogen without inviting the backfiring that can occur when hydrogen is burned in a traditional piston engine. The separate induction chamber also provides a safer temperature for fitting the dual hydrogen injectors with their rubber seals, which are susceptible to the high temperatures encountered in a conventional reciprocating engine."
The Mazda RX-8 RE hybrid car also employs a couple of other environmentally friendly features of which one would not normally think. For instance, the RX-8 uses a water-based paint, applied wet three times, which reduces the emission of organic solvents, speeds drying time and reduces CO2 gases. The RX-8 also uses plant-based plastic parts on the interior that are not derived from petroleum unlike other plastics.
Other environmentally-friendly and efficiency-friendly systems that Mazda is working on for future generations include regenerative braking, idle-stop systems and electric acceleration assistance systems. An electric motor assist turbocharger is being developed to enhance the efficiency of hydrogen combustion and regeneration of energy from the car's exhaust. Mazda also plans to merge the hydrogen-gasoline hybrid system with an electric motor counterpart, or tribrid technology, in order to create even greater efficiency and cleaner running systems than ever before. This tribrid technology will feature an electric motor, inverter and 144v battery and H2ICE engine. Tribrid technology will likely replace hybrid technology for other vehicles as well in the transition to all-hydrogen technology when the hydrogen economy starts to take hold.
