The rotary engine was an early type of internal combustion engine designed with an odd number of cylinders per row in a radial configuration, in which the crankshaft remained stationary in operation, with the entire crankcase and its attached cylinders rotating around it as a unit. Its main application was in aviation, although it saw use before its primary aviation role, in a few early motorcycles and automobiles; this type of engine was used as an alternative to conventional inline engines during World War I and the years preceding that conflict. It has been described as "a efficient solution to the problems of power output and reliability". By the early 1920s, the inherent limitations of this type of engine had rendered it obsolete. A rotary engine is a standard Otto cycle engine, with cylinders arranged radially around a central crankshaft just like a conventional radial engine, but instead of having a fixed cylinder block with rotating crankshaft as with a radial engine, the crankshaft remains stationary and the entire cylinder block rotates around it.
In the most common form, the crankshaft was fixed solidly to the airframe, the propeller was bolted to the front of the crankcase. This difference has much impact on design and functioning; the Musee de l'Air in Paris has on display a special, "sectioned" working model of an engine with seven "radially disposed" cylinders. It alternates between "rotary" and "radial" modes to demonstrate the difference between the internal motions of the two types of engine. Like "fixed" radial engines, rotaries were built with an odd number of cylinders, so that a consistent every-other-piston firing order could be maintained, to provide smooth running. Rotary engines with an number of cylinders were of the "two row" type. Most rotary engines were arranged with the cylinders pointing outwards from a single crankshaft, in the same general form as a radial, but there were rotary boxer engines and one-cylinder rotaries. Three key factors contributed to the rotary engine's success at the time: Smooth running: Rotaries delivered power smoothly because there are no reciprocating parts, the large rotating mass of the crankcase/cylinders acted as a flywheel.
Improved cooling: when the engine was running, the rotating crankcase/cylinder assembly created its own fast-moving cooling airflow with the aircraft at rest. Weight advantage: many conventional engines had to have heavy flywheels added to smooth out power impulses and reduce vibration. Rotary engines gained a substantial power-to-weight ratio advantage by having no need for an added flywheel, they shared with other radial configuration engines the advantage of a small, flat crankcase, because of their efficient air-cooling system, cylinders could be made with thinner walls and shallower cooling fins, which further reduced their weight. Engine designers had always been aware of the many limitations of the rotary engine so when the static style engines became more reliable and gave better specific weights and fuel consumption, the days of the rotary engine were numbered. Rotary engines had a fundamentally inefficient total-loss oiling system. In order to reach the whole engine, the lubricating medium needed to enter the crankcase through the hollow crankshaft.
The only practical solution was for the lubricant to be aspirated with the fuel/air mixture, as in a two-stroke engine. Power increase came with mass and size increases, multiplying gyroscopic precession from the rotating mass of the engine; this produced stability and control problems in aircraft in which these engines were installed for inexperienced pilots. Power output went into overcoming the air-resistance of the spinning engine. Engine controls were tricky, resulted in fuel waste; the late WWI Bentley BR2, as the largest and most powerful rotary engine, had reached a point beyond which this type of engine could not be further developed, it was the last of its kind to be adopted into RAF service. It is asserted that rotary engines had no throttle and hence power could only be reduced by intermittently cutting the ignition using a "blip" switch; this was literally true of the "Monosoupape" type, which took most of the air into the cylinder through the exhaust valve, which remained open for a portion of the downstroke of the piston.
Thus the richness of the mixture in the cylinder could not be controlled via the crankcase intake. The "throttle" of a monosoupape provided only a limited degree of speed regulation, as opening it made the mixture too rich, while closing it made it too lean. Early models featured a pioneering form of variable valve timing in an attempt to give greater control, but this caused the valves to burn and therefore it was abandoned; the only way of running a Monosoupape engine smoothly at reduced revs was with a switch that changed the normal firing sequence so that each cylinder fired only once per two or three engine revolutions, but the engine remained more or less in balance. As with excessive use of the "blip" switch: running the engine on such a setting for too long resulted in large quantities of unburned fuel and oil in the exhaust, gathering in the lower cowling, where it was a notorious fire hazard. Most rotaries had normal inlet valves, so that the fuel was taken into the cylinders mixed with air - as in a normal four-stroke engine.
Sarich orbital engine
The Sarich orbital engine is a type of internal combustion engine, invented in 1972 by Ralph Sarich, an engineer from Perth, which features orbital rather than reciprocating motion of its internal parts. It differs from the conceptually similar Wankel engine by using a prismatic shaped rotor that orbits the axis of the engine, without rotation, rather than the rotating trilobular rotor of the Wankel; the theoretical advantage is that there is no high-speed contact area with the engine walls, unlike in the Wankel engine in which edge wear is a problem. However, the combustion chambers are divided by blades which do have contact with both the walls and the rotor, are said to have been difficult to seal due to the perpendicular intersection with the moving impeller. Sarich worked on the concept for a number of years without producing a production engine. A prototype was demonstrated; the engine, which produces high revs, has eight moving parts in the six-chambered version depicted in the patent application, plus valves for each chamber.
It can be powered by compressed air or steam and can be run as a pump. In the patent, the engine is described as two-stroke internal combustion engine, but the patent claims that with a different valve mechanism it could be used a four-stroke engine. A blower is required as the two stroke cycle does not provide suction to draw the mixture into the chamber; the Sarich orbital engine has a number of fundamental unsolved problems that have kept it from becoming a usable engine. Some key components cannot be cooled and others cannot be lubricated, so it is susceptible to overheating. At one press conference at which Sarich presented the engine, automotive engineer Phil Irving pointed out a number of technical difficulties; some processes developed for the engine could be used for other engines, such as the Orbital Combustion Process, an air/fuel precompresser for injection. Orbital Corporation Powerplus supercharger
The radial engine is a reciprocating type internal combustion engine configuration in which the cylinders "radiate" outward from a central crankcase like the spokes of a wheel. It resembles a stylized star when viewed from the front, is called a "star engine" in some languages; the radial configuration was used for aircraft engines before gas turbine engines became predominant. Since the axes of the cylinders are coplanar, the connecting rods cannot all be directly attached to the crankshaft unless mechanically complex forked connecting rods are used, none of which have been successful. Instead, the pistons are connected to the crankshaft with a master-and-articulating-rod assembly. One piston, the uppermost one in the animation, has a master rod with a direct attachment to the crankshaft; the remaining pistons pin their connecting rods' attachments to rings around the edge of the master rod. Extra "rows" of radial cylinders can be added in order to increase the capacity of the engine without adding to its diameter.
Four-stroke radials have an odd number of cylinders per row, so that a consistent every-other-piston firing order can be maintained, providing smooth operation. For example, on a five-cylinder engine the firing order is 1, 3, 5, 2, 4, back to cylinder 1. Moreover, this always leaves a one-piston gap between the piston on its combustion stroke and the piston on compression; the active stroke directly helps compress the next cylinder to fire. If an number of cylinders were used, an timed firing cycle would not be feasible; the prototype radial Zoche aero-diesels have an number of cylinders, either four or eight. The radial engine uses fewer cam lobes than other types; as with most four-strokes, the crankshaft takes two revolutions to complete the four strokes of each piston. The camshaft ring is geared to spin slower and in the opposite direction to the crankshaft; the cam lobes exhaust. For example, four cam lobes serve all five cylinders, whereas 10 would be required for a typical inline engine with the same number of cylinders and valves.
Most radial engines use overhead poppet valves driven by pushrods and lifters on a cam plate, concentric with the crankshaft, with a few smaller radials, like the Kinner B-5 and Russian Shvetsov M-11, using individual camshafts within the crankcase for each cylinder. A few engines use sleeve valves such as the 14-cylinder Bristol Hercules and the 18-cylinder Bristol Centaurus, which are quieter and smoother running but require much tighter manufacturing tolerances. C. M. Manly constructed a water-cooled five-cylinder radial engine in 1901, a conversion of one of Stephen Balzer's rotary engines, for Langley's Aerodrome aircraft. Manly's engine produced 52 hp at 950 rpm. In 1903–1904 Jacob Ellehammer used his experience constructing motorcycles to build the world's first air-cooled radial engine, a three-cylinder engine which he used as the basis for a more powerful five-cylinder model in 1907; this was made a number of short free-flight hops. Another early radial engine was the three-cylinder Anzani built as a W3 "fan" configuration, one of which powered Louis Blériot's Blériot XI across the English Channel.
Before 1914, Alessandro Anzani had developed radial engines ranging from 3 cylinders — early enough to have been used on a few French-built examples of the famous Blériot XI from the original Blériot factory — to a massive 20-cylinder engine of 200 hp, with its cylinders arranged in four rows of five cylinders apiece. Most radial engines are air-cooled, but one of the most successful of the early radial engines was the Salmson 9Z series of nine-cylinder water-cooled radial engines that were produced in large numbers during the First World War. Georges Canton and Pierre Unné patented the original engine design in 1909, offering it to the Salmson company. From 1909 to 1919 the radial engine was overshadowed by its close relative, the rotary engine, which differed from the so-called "stationary" radial in that the crankcase and cylinders revolved with the propeller, it was similar in concept to the radial, the main difference being that the propeller was bolted to the engine, the crankshaft to the airframe.
The problem of the cooling of the cylinders, a major factor with the early "stationary" radials, was alleviated by the engine generating its own cooling airflow. In World War I many French and other Allied aircraft flew with Gnome, Le Rhône, Bentley rotary engines, the ultimate examples of which reached 250 hp although none of those over 160 hp were successful. By 1917 rotary engine development was lagging behind new inline and V-type engines, which by 1918 were producing as much as 400 hp, were powering all of the new French and British combat aircraft. Most German aircraft of the time used water-cooled inline 6-cylinder engines. Motorenfabrik Oberursel made licensed copies of the Gnome and Le Rhône rotary powerplants, Siemens-Halske built their own designs, including the Siemens-Halske Sh. III eleven-cylinder rotary engine, unusual for the period in being geared through a bevel geartrain in the rear end of the crankcase without the crankshaft being mounted to the aircraft's airframe, so that the engine's internal working components (fully in
Internal combustion engine
An internal combustion engine is a heat engine where the combustion of a fuel occurs with an oxidizer in a combustion chamber, an integral part of the working fluid flow circuit. In an internal combustion engine, the expansion of the high-temperature and high-pressure gases produced by combustion applies direct force to some component of the engine; the force is applied to pistons, turbine blades, rotor or a nozzle. This force moves the component over a distance, transforming chemical energy into useful mechanical energy; the first commercially successful internal combustion engine was created by Étienne Lenoir around 1859 and the first modern internal combustion engine was created in 1876 by Nikolaus Otto. The term internal combustion engine refers to an engine in which combustion is intermittent, such as the more familiar four-stroke and two-stroke piston engines, along with variants, such as the six-stroke piston engine and the Wankel rotary engine. A second class of internal combustion engines use continuous combustion: gas turbines, jet engines and most rocket engines, each of which are internal combustion engines on the same principle as described.
Firearms are a form of internal combustion engine. In contrast, in external combustion engines, such as steam or Stirling engines, energy is delivered to a working fluid not consisting of, mixed with, or contaminated by combustion products. Working fluids can be air, hot water, pressurized water or liquid sodium, heated in a boiler. ICEs are powered by energy-dense fuels such as gasoline or diesel fuel, liquids derived from fossil fuels. While there are many stationary applications, most ICEs are used in mobile applications and are the dominant power supply for vehicles such as cars and boats. An ICE is fed with fossil fuels like natural gas or petroleum products such as gasoline, diesel fuel or fuel oil. There is a growing usage of renewable fuels like biodiesel for CI engines and bioethanol or methanol for SI engines. Hydrogen is sometimes used, can be obtained from either fossil fuels or renewable energy. Various scientists and engineers contributed to the development of internal combustion engines.
In 1791, John Barber developed the gas turbine. In 1794 Thomas Mead patented a gas engine. In 1794, Robert Street patented an internal combustion engine, the first to use liquid fuel, built an engine around that time. In 1798, John Stevens built the first American internal combustion engine. In 1807, French engineers Nicéphore and Claude Niépce ran a prototype internal combustion engine, using controlled dust explosions, the Pyréolophore; this engine powered a boat on France. The same year, the Swiss engineer François Isaac de Rivaz built an internal combustion engine ignited by an electric spark. In 1823, Samuel Brown patented the first internal combustion engine to be applied industrially. In 1854 in the UK, the Italian inventors Eugenio Barsanti and Felice Matteucci tried to patent "Obtaining motive power by the explosion of gases", although the application did not progress to the granted stage. In 1860, Belgian Jean Joseph Etienne Lenoir produced a gas-fired internal combustion engine. In 1864, Nikolaus Otto patented the first atmospheric gas engine.
In 1872, American George Brayton invented the first commercial liquid-fuelled internal combustion engine. In 1876, Nikolaus Otto, working with Gottlieb Daimler and Wilhelm Maybach, patented the compressed charge, four-cycle engine. In 1879, Karl Benz patented a reliable two-stroke gasoline engine. In 1886, Karl Benz began the first commercial production of motor vehicles with the internal combustion engine. In 1892, Rudolf Diesel developed compression ignition engine. In 1926, Robert Goddard launched the first liquid-fueled rocket. In 1939, the Heinkel He 178 became the world's first jet aircraft. At one time, the word engine meant any piece of machinery—a sense that persists in expressions such as siege engine. A "motor" is any machine. Traditionally, electric motors are not referred to as "engines". In boating an internal combustion engine, installed in the hull is referred to as an engine, but the engines that sit on the transom are referred to as motors. Reciprocating piston engines are by far the most common power source for land and water vehicles, including automobiles, ships and to a lesser extent, locomotives.
Rotary engines of the Wankel design are used in some automobiles and motorcycles. Where high power-to-weight ratios are required, internal combustion engines appear in the form of combustion turbines or Wankel engines. Powered aircraft uses an ICE which may be a reciprocating engine. Airplanes can instead use jet engines and helicopters can instead employ turboshafts. In addition to providing propulsion, airliners may employ a separate ICE as an auxiliary power unit. Wankel engines are fitted to many unmanned aerial vehicles. ICEs drive some of the large electric generators, they are found in the form of combustion turbines in combined cycle power plants with a typical electrical output in the range of 100 MW to 1 GW. The high temperature exhaust is used to superheat water to run a steam turbine. Thus, the efficiency is higher because more energy is extracted from the fuel than what could be extracted by the co
The Bourke engine was an attempt by Russell Bourke, in the 1920s, to improve the two-stroke engine. Despite finishing his design and building several working engines, the onset of World War II, lack of test results, the poor health of his wife compounded to prevent his engine from coming to market; the main claimed virtues of the design are that it has only two moving parts, is lightweight, has two power pulses per revolution, does not need oil mixed into the fuel. The Bourke engine is a two-stroke design, with one horizontally opposed piston assembly using two pistons that move in the same direction at the same time, so that their operations are 180 degrees out of phase; the pistons are connected to a Scotch Yoke mechanism in place of the more usual crankshaft mechanism, thus the piston acceleration is sinusoidal. This causes the pistons to spend more time at top dead center than conventional engines; the incoming charge is compressed in a chamber under the pistons, as in a conventional crankcase-charged two-stroke engine.
The connecting-rod seal prevents the fuel from contaminating the bottom-end lubricating oil. The operating cycle is similar to that of a current production spark ignition two-stroke with crankcase compression, with two modifications: The fuel is injected directly into the air as it moves through the transfer port; the engine is designed to run without using spark ignition. This is known as auto-ignition or dieseling, the air/fuel mixture starts to burn due to the high temperature of the compressed gas, and/or the presence of hot metal in the combustion chamber; the following design features have been identified: Scotch yoke instead of connecting rods to translate linear motion to rotary motion Fewer moving parts and the opposed cylinders are combinable to make 2, 4, 6, 8, 10, 12 or any number of cylinders The piston is connected to the Scotch yoke through a slipper bearing Mechanical fuel injection. Ports rather than valves. Easy maintenance with simple tools; the Scotch yoke does not create lateral forces on the piston, reducing piston wear.
O-rings are used to seal joints rather than gaskets. The Scotch Yoke makes the pistons dwell slightly longer at top dead center, so the fuel burns more in a smaller volume. Low exhaust temperature so metal exhaust components are not required, plastic ones can be used if strength is not required from exhaust system 15:1 to 24:1 compression ratio for high efficiency and it can be changed as required by different fuels and operation requirements. Fuel is vaporised when it is injected into the transfer ports, the turbulence in the intake manifolds and the piston shape above the rings stratifies the fuel air mixture into the combustion chamber. Lean burn for reduced emissions; this design uses oil seals to prevent the pollution from the combustion chamber from polluting the crankcase oil, extending the life of the oil as it is used for keeping the rings full of oil to hold and use to lubricate. Oil was shown to be used by the dropfull as needed, but checking the quantity and cleanness of it was still recommended by Russell Bourke, its creator.
The lubricating oil in the base is protected from combustion chamber pollution by an oil seal over the connecting rod. The piston rings are supplied with oil from a small supply hole in the cylinder wall at bottom dead center. Efficiency 0.25 /hp is claimed - about the same as the best diesel engine, or twice as efficient as the best two strokes. This is equivalent to a thermodynamic efficiency of 55.4%, an exceedingly high figure for a small internal combustion engine. In a test witnessed by a third party, the actual fuel consumption was 1.1 hp/, or 0.9 /hp, equivalent to a thermodynamic efficiency of about 12.5%, typical of a 1920s steam engine. A test of a 30 cubic inch Vaux engine, built by a close associate of Bourke, gave a fuel consumption of 1.48 lb/, or 0.7 /hp at maximum power. Power to weight The Silver Eagle was claimed to produce 25 hp from 45 lb, or a power to weight ratio of 0.55 hp/lb. The larger 140 cubic inch engine was good for 120 hp from 125 lb, or 1 hp/lb; the Model H was claimed to produce 60 hp with a weight of 95 lb, hence giving a power to weight ratio of 0.63 hp/lb.
The 30 cu in twin was reported to produce 114 hp at 15000rpm while weighing only 38 lb, an incredible 3 hp/lb However a 30 cu in replica from Vaux Engines produced just 8.8 hp at 4000 rpm after substantial reworking. Other sources claim 0.9 to 2.5 hp/lb, although no independently witnessed test to support these high figures has been documented. The upper range of this is twice as good as the best four-stroke production engine shown here, or 0.1 hp/lb better than a Graupner G58 two-stroke. The lower claim is unremarkable exceeded by production four-stroke engines, never mind two strokes. Emissions Achieved no hydrocarbons or carbon monoxide in published test results, however no power output was given for these results, NOx was not measured. Low Emissions The engine is claimed to be able to operate on hydrogen or any hydro-carbon fuel without any modifications, producing only water vapor and carbon dioxide as emissions; the Bourke Engine has some interesting features, but the extravagant claims for its performance are unlikely to be borne out by real tests.
Many of the claims are contradictory. Seal friction from the seal between the air compressor chamber and the crankcase, agai