Comparatively analyzing the rich and lean combustion of ammonia-oxygen in the Wankel rotary engine

<div>The Wankel engine is an eccentric rotary internal combustion engine known for its simplicity, compactness, reliability, and efficiency. However, issues related to sealing, efficiency, and emissions have hindered its widespread use. Recent advancements in sealing technology, novel designs, material coatings, and alternative fuels have addressed some of these problems, leading to improvements in Wankel engine performance. This study examines these advancements in Wankel engine technology and proposes three potential applications for future automotive use. The first application involves utilizing a Wankel engine with a continuously variable transmission to replace the powertrain in conventional vehicles. The second application suggests replacing the engine in a series-parallel electric-hybrid architecture with a Wankel engine. Lastly, the third application explores using a Wankel engine as a range extender for electric vehicles. To evaluate the benefits in terms of fuel consumption for different drive cycles, each of these applications was modeled using the Future Automotive System Technology Simulator (FASTSim). The models were assessed with both standard Wankel engines and those incorporating recent advancements. The results indicate a potential reduction in fuel consumption when utilizing improved Wankel engine designs compared to traditional piston-based engines. However, it should be noted that these improved Wankel engines still face significant challenges regarding hydrocarbon emissions. Furthermore, the study identified a promising application for Wankel engines as range extenders in electric vehicles, suggesting their potential to enhance the overall efficiency of electric transportation.</div>

During the decades past, the engine industries have witnessed a remarkable upsurge in the research and development (R&D) of modern technologies due to factors such as energy security and environmental concerns. Focus is on improved engine performance, sustainable energy, fuel economy, and minimal harmful exhaust emissions. Even though globally large database now captures modern engine technologies, a skillful presentation of those data is a demanding task. Based on this analogy, the authors made a conscious effort to brief audience on the various fuels used in Wankel rotary engine (RE) which is a type of internal combustion engine (ICE). Wankel REs various operating models, their merits, and demerits regarding modern engine technologies, the type of fuels and their utilization methods, and the future prospect of biofuel as its engine fuel has been made accessible in a subtle manner in this paper. In summary, this paper provides a wide scope review of basic principles that govern practical Wankel RE design and operation, the widely used single fuels and multi fuels in Wankel RE operation with their properties as well as emissions, and the practical Wankel RE design and operation in the present era and the prospects in the near future. It also outlines simplified frameworks of modern Wankel RE technologies structured in a systematic way to contribute to enhanced engine performance, sustainable energy, reduce fuel consumption, and reduce exhaust emissions in this pragmatic field.

<div class="section abstract"><div class="htmlview paragraph">Internal combustion engines are generally reciprocating or, to a less extent, Wankel rotary engine types. Reciprocating engines are bulky, heavy and complex, mainly due to the need for intake and exhaust valves and their associated cam-train, and their complicated crankshaft. Wankel rotary engines overcome these deficiencies but have other undesirable features. An alternative to the Wankel engine is the Szorenyi Three Chamber Rotary Engine concept created by the Rotary Engine Development Agency (REDA). This paper analyses the design features of the two rotary engine types and directly compares the merits of the designs. The paper analyses the Wankel engine’s geometry which causes an excessive eccentric shaft deflection due to the centrifugal force of the rotor that is eccentric to the engine centreline and which results in limiting the engine rotor to low revs; a combustion chamber shape that causes a high-speed transfer of the combusting gases (the ‘squish’ effect) which results in incomplete combustion; and a large overlap of intake and exhaust timing which results in excessive leakage between chambers. The analysis reveals that these deficiencies are inherent to the geometry of the engine and cannot be practically overcome. The analysis of the Szorenyi engine reveals that, whilst also geometrically based, it has a balanced rotor which will not result in a need to limit the engine revs; a combustion chamber which does not exhibit the same squish effect; and has ideal Otto cycle port timing. The paper concludes that the Szorenyi engine concept has significant advantages over the Wankel and reciprocating engines and can replace it in a broad range of applications.</div></div>

Numerical study of compound intake on mixture formation and combustion process in a hydrogen-enriched gasoline Wankel rotary engine

Potential improvement in performance and emissions of air-cooled rotary engine using novel enhanced cooling fins

<div class="htmlview paragraph">A computer simulation which models engine performance of Direct Injection Stratified Charge (DISC) rotary engines has been used to study the effect of variations in engine design and operating parameters on engine performance and efficiency of an experimental Outboard Marine Corporation (OMC) rotary combustion engine. Engine pressure data have been used in a heat release analysis to study the effects of heat transfer, leakage and crevice flows. Predicted engine data is compared with experimental test data over a range of engine speeds and loads. An examination of methods to improve the performance of the rotary engine using advanced heat engine concepts such as faster combustion, reduced leakage and turbocharging is also presented.</div> <div class="htmlview paragraph">THE DIRECT-INJECTION stratified-charge (DISC) Wankel rotary engine is currently being evaluated by NASA as a future advanced powerplant for light commercial and similar applications. The Wankel rotary engine offers attractive advantages over the reciprocating engines for use in small aircraft. These advantages include higher power to weight ratio, simpler and more compact shape, fewer moving parts, lower noise levels and less vibration. In addition, using direct-injection stratified-charge operation, the rotary engine can be designed for operation with jet-fuel or multi-fuel capability (<span class="xref">1</span>,<span class="xref">2</span>)<span class="xref">*</span>.</div> <div class="htmlview paragraph">The purpose of this study is to examine the combustion rate and performance loss mechanisms of an experimental Outboard Marine Corporation (OMC) DISC Wankel rotary engine. The test program was conducted using an OMC single rotor experimental engine at NASA Lewis Research Center to obtain engine performance data and to investigate the stratified-charge concept. To support these testing activities, numerical simulations were used to examine heat release and heat loss mechanisms (such as heat transfer, crevice volumes and gas leakage). These simulations were also used to investigate how DISC Wankel engine performance varies with changes in engine design and operating conditions. Experimental pressure data obtained from the OMC rotary test engine were used with the heat release rate computer model to compute the fuel burning rate and loss mechanisms. Performance predictions of the OMC engine were compared with experimental data. The performance improvements of the DISC Wankel rotary engine were also investigated.</div>

A review: Centurial progress and development of Wankel rotary engine

Realizing high-efficiency and low-emission load control of Wankel rotary engine by CH4/H2 synergy

Effectiveness of hydrogen enrichment strategy for Wankel engines in unmanned aerial vehicle applications at various altitudes

Recently, hydrogen has been considered as an alternative for conventional fuels which is used for a transportation sector. The Wankel rotary engine is more adaptable for running on hydrogen fuels than traditional reciprocating engines possessing lower preignition and backfire probability. Experimental and numerical data are presented for the Wankel rotary engine performance on hydrogen blends with hydrocarbon fuel. For the experimental study of the hydrogen addition effect on the engine performance, the Wankel engine test bench VAZ-311 (Russia) was used. The hydrogen and gasoline supply were carried out by injectors mounted in the Wankel rotary engine inlet manifold. The experiments showed that a 5% hydrogen mass fraction in the fuel mixture increases peak pressure in the Wankel rotary engine combustion chamber for partial loads. For the theoretical study, a numerical model of the flame propagation in the Wankel rotary engine combustion chamber was developed. Numerical research revealed the possibility of a complete air–fuel mixture combustion due to hydrogen addition for a number of operating conditions.

An experimental investigation of hydrogen-enriched gasoline in a Wankel rotary engine

Discussion on the potential of methane-hydrogen dual-fueled Wankel rotary engine

Reviewed by: Wankel auf dem Prüfstand: Ursprung, Entwicklung, und Niedergang eines innovativen Motorenkonzeptes Ulrich Wengenroth (bio) Wankel auf dem Prüfstand: Ursprung, Entwicklung, und Niedergang eines innovativen Motorenkonzeptes. By Ulrich Ch. Knapp . Münster: Waxmann, 2006. Pp. 213. €25.50. This book by Ulrich Ch. Knapp is a history of the Wankel rotary engine from a German perspective. Instead of reciprocating pistons, the Wankel uses a rotor for the conventional four-stroke process of most gasoline-powered engines. Beginning in the mid-1960s, Wankel engines were used in cars, boats, and pumps. But the only Wankel-powered automobile today is a Mazda sports car. While the Wankel engine is very compact, delivers unparalleled smooth power, and easily revs up, its shortcomings are low mileage and serious exhaust pollution. Both are consequences of the oddly shaped, moving combustion chamber that does not allow for efficient combustion. Felix Wankel (1902–1988) was a school dropout with no engineering education. In 1922 he organized a militant forerunner to the SA, and in 1926 he formally joined the Nazi Party. Upset by the personal vanities of some Nazi fat cats, he left the party in 1932 and was even a political prisoner for a few months after the Nazis' rise to power in 1933. This did not affect his anti-democratic attitude, and throughout the Nazi years he courted party leaders all the way up to Hitler to find support for his engineering experiments. His main supporter and advisor from the early 1930s until well after World War II was Wilhelm Keppler, economic adviser to the Nazi government, SS leader, undersecretary of state "for special tasks," and in the end a convicted war criminal. Bored by his job as an insurance agent, Wankel began developing rotary engines in the late 1920s in a small workshop. His experience with rotary valves earned him a number of research contracts for aircraft engines. The breakthrough for a workable rotary engine only came in the 1950s. While major automobile firms turned a cold shoulder, Wankel found support at NSU, a small manufacturer of motorcycles and subcompact cars. NSU was to develop the Wankel engine into an automobile power plant, first in a little "spider" and eventually in a (European) full-size limousine. Financially more important—and certainly more profitable—was licensing by NSU and Wankel. Virtually all major engine and auto manufacturers took a Wankel license in the late 1960s and early 1970s. The first licensee in America was Curtiss-Wright; the most promising was General Motors. But with the exception of Mazda, all of this came to nothing. The rise of oil prices after 1973 killed the low-mileage Wankel. And, more than Knapp admits, tightening pollution restrictions eventually sealed the fate of this ingenious little engine. Felix Wankel himself had been smart enough to sell his engineering firm in 1972—a year before gas prices skyrocketed—to Lonrho, a British conglomerate, for 100 million deutschmarks. There is a school of Wankel enthusiasts who claim that a "piston cartel" [End Page 652] among major car manufacturers obstructed the development of a superior technology. Knapp debunks all the conspiracy theories. He convincingly shows that it was the fundamental shortcomings of the rotary engine and the simultaneous improvement of traditional piston engines that made auto manufacturers turn away as they had previously done with gas turbines. Knapp is very good in showing how it took an innovative group of engineers at the periphery of auto manufacture to venture into a groundbreaking new technology in the first place. He follows this group and eventually finds some of them at Audi, designing a small diesel engine for Volkswagen. Diesels yield the best mileage in cars and were felt to be a godsend in the face of rising oil prices. America quickly gave up on diesel-powered autos, but in continental Europe they currently have a market share of more than 50 percent. Diesels were the answer to high fuel costs, while Wankels gave an idea of how silent a car could be. The combination of the two characteristics was the R&D path of the European car industry. Wankel engines were not ineffective, as Knapp shows, they just turned up...

<div class="section abstract"><div class="htmlview paragraph">The X engine is a non-Wankel rotary engine that allies high power density and high efficiency by running a high-pressure Atkinson cycle at high speeds. The X engine overcomes the gas leakage issue of the Wankel engine by using two axially-loaded face seals that directly interface with three stationary radially-loaded apex seals per rotor. The direct-interfacing of the apex and face seals eliminates the need for corner seals of the typical Wankel engine, significantly reducing rotary engine blowby. This paper demonstrates the sealing performance that can be achieved by this new type of seal configuration for a rotary engine based on dynamics models and experiments. The dynamics models calculate the displacement and deformation of the face and apex seals for every crank angle using a time implicit solver. The gas leakage is then calculated from the position of the seals and pressure in the chambers and integrated over a rotor revolution. An “effective leakage orifice” area can be determined, to compare blowby between different engine types. Model results show that the X engine equivalent leakage area could be around 35% that of the leakage area of a similarly sized Wankel engine obtained from the same modeling method, which brings the X engine leakage closer to the piston engine’s leakage range. Initial experimental results support the findings from the model, as the X engine shows an equivalent leakage area of about 65% that of a scaled Wankel engine. This result demonstrates the potential of the X engine to achieve gas sealing improvements through additional seal development.</div></div>

The Wankel engine is suited to be used to drive hybrid propulsion systems. The main disadvantage of hybrid propulsion systems is the complexity that causes a high weight and large dimensions. For these reason hybrid systems are more suitable for large size vehicle (buses, vans) rather than for small passenger cars. A considerable reduction of hybrid systems weight and dimensions can be obtained using a Wankel rotary engine instead of a conventional engine. The Wankel engine is light, compact, simple, and produces low noise and low vibrations. Therefore a Wankel engine powered hybrid system is suited to be used on small cars. In this paper a 1,000 kg parallel hybrid car with continuously variable transmission and a 6,000 kg series hybrid minibus both equipped with Wankel engines are considered. The Wankel engine works at steady state to minimize fuel consumption and exhaust emissions. The simulation of the behavior of these two vehicles during a ECE + EUDC test cycle is presented in order to evaluate the performances of the systems.