Crankcase ventilation system

A crankcase ventilation system (CVS) is a one way passage for the blow-by gases to escape in a controlled manner from the crankcase of an internal combustion engine. The blow-by gases are generated when a small but continual amount of gases (air, unburned fuel, combustion gases) leak from the combustion chamber past the piston rings, that is, blow by them, and the piston ring gaps to end up inside the crankcase, causing pressure to build up in there. Additional sources of blow-by that contribute to this effect are gases leaking past the turbocharger shaft, the air compressors (if present) and in some cases the valve stem seals. The blow-by gases, if not ventilated, can condense and combine with the oil vapor present in the crankcase forming sludge or cause the oil to become diluted with unburned fuel, degrading its quality and decreasing its effective life. Additionally, excessive crankcase pressure can lead to engine oil leaks past the crankshaft seals and other engine seals and gaskets. Prolonged period of oil leaks can starve the engine of oil and damage it in a permanent way. Therefore, it becomes imperative that a crankcase ventilation system is used. This allows the blow-by gases, consisting of the combustion products and the oil vapors, to be vented through a PCV (positive crankcase ventilation) valve out of the crankcase. There are three system architectures when the blow-by gas exits the crankcase. It can either enter the air inlet manifold (closed CVS), be vented freely in the atmosphere (open CVS) or be vented in the atmosphere through a filter (filtered open CVS). Early provisions From the late 19th century through the early 20th, blow-by gases from internal combustion were allowed to find their own way out to the atmosphere past seals and gaskets. It was considered normal for oil to be found both inside and outside an engine, and for oil to drip to the ground in small but constant amounts. The latter had also been true for steam engines and steam locomotives in the decades before. Even bearing and valve designs generally made little to no provision for keeping oil or waste gases contained. Sealed bearings and valve covers were for special applications only. Gaskets and shaft seals were meant to limit loss of oil, but they were usually not expected to entirely prevent it. On internal combustion engines, the hydrocarbon-rich blow-by gases would diffuse through the oil in the seals and gaskets into the atmosphere. Engines with high amounts of blow-by (e.g., worn out ones, or ones not well...

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Crankpin

A crankpin or crank journal is a journal in an engine or mechanical device. That is, the part of a shaft or axle that rests on bearings. In a reciprocating engine, the crankpin is the part of a crankshaft where the lower end of a connecting rod attaches. In a beam engine, a single crankpin is mounted on the flywheel; In a steam locomotive, crankpins are often mounted directly on the driving wheels.  Crankpins highlighted in blue A crankpin of a ship steam engine with the lubricating system visible Application A crankpin is separated from its shaft or axle by a bearing. These are commonly bushings or plain bearings, but less commonly may be roller bearings. In a multi-cylinder engine, a crankpin can serve one or many cylinders, for example: In a in-line or opposed engine, each crankpin normally serves just one cylinder. In a V engine, each crankpin may serves one or two cylinders, depending on the design. In a radial engine, each crankpin serves an entire row of cylinders. Design considerations There are three common configurations in crankpin design: If a crankpin serves only one cylinder, then the big end (the usually larger end of a connecting rod that attaches to the crankpin, as opposed to the "small end", which is attached to the wrist/gudgeon pin in the piston, or the end of the crosshead in engines so equpped, allowing it to be articulated on both ends) is a relatively simple design, accommodating only one connecting rod. This design is the cheapest to produce, and is used in: All single-cylinder engines. Most straight engines. All boxer engines. Some V-twin engines. If a crankpin serves more than one cylinder, then the corresponding cylinders may have an offset, or may be articulated, to simplify the design of the big end bearing. This design is used in most V engines. If more than one cylinder is served by a single crankpin but there is no offset, then some or all of the connecting rods must be forked at the big end, or be articulated. This design provides better engine balance than designs with an offset, but requires extra complexity and cost in both design and manufacture, and more weight or closer manufacturing tolerances to achieve the same strength and reliability. Any extra weight added to the big end itself also carries a penalty of adding vibration and reducing balance. As the number of cylinders grows, the effect of the offset on balance becomes less important, and forked connecting rods become less common. They are mainly used in V-twin engines, notably including motorcycle engines, but in the past were found on a number of automobile and aero engines, such as the famous Rolls-Royce Merlin aero engine of the...

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Tunnel crankcase

A tunnel crankcase, tunnel crankshaft or disc-webbed crankshaft engine is a diesel engine where the crankshaft is designed so that the main bearings (the bearings that support the crankshaft within the crankcase) are enlarged in diameter, such that they are now larger than the crank webs (the radial arms that link the big end bearings to the main bearings). They thus form the largest diameter of any part of the crankshaft. Rather than a conventional crankcase that has webs across it to support the narrow bearings of a conventional crankcase, the crankcase now has a large tunnel through it, hence the name. Tunnel crankcases appeared in the 1930s with the first high-speed diesel engines. They were favoured by some makers more than others, notably Saurer in Switzerland and Maybach-Motorenbau GmbH (now MTU) Friedrichshafen. They are described as both 'tunnel crankcases' and 'roller bearing cranks'; the two aspects are related and it is unclear as to which gave rise to the other. Origins Semi-tunnel crankshaft from a Tatra T27 This is a built-up crankshaft with bolted webs. The crank bearings (excludingthe bearing races) are smaller than the webs. The end bearings of this semi-tunnel crankshaft (not shown) are also of conventional small size. With the development of the high-speed diesel engine around 1930, powerful diesel engines became available in the sizes previously used by lower-powered petrol engines. In particular, their high BMEP and high torque led to high forces on the crankshaft bearings. These forces were greater than could be sustained by the small whitemetal bearings used for petrol engines. Although aircraft and sports car engines in the 1920s developed to have considerable power in a small space, these were high maintenance machines with regular servicing. The new diesels were intended for long commercial service where maintenance was a key cost to be reduced. The need for an improved bearing technology led to the adoption of roller bearings, rather than whitemetal. Although they might be considered esoteric today, ball and roller crankshaft bearings were already in use in the 1920s for such mundane engines as the Austin 7. Roller bearings require one-piece races for both inner and outer bearing tracks. Although split races are possible, they are expensive and difficult to fit. A simpler means of fitting roller bearings is to enlarge the diameter of the bearing, so that it becomes larger than the entire crankshaft web. Assembly is now done by putting the outer race of the bearing over the crankshaft axially from one end, rather than by assembling two pieces radially. An early development was the semi-tunnel crankshaft. This used large ball or roller bearings of the tunnel style for their centre...

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Crankcase

A crankcase is the housing for the crankshaft in a reciprocating internal combustion engine. The enclosure forms the largest cavity in the engine and is located below the cylinder(s), which in a multicylinder engine is usually integrated into one or several cylinder blocks. Crankcases have often been discrete parts, but more often they are integral with the cylinder bank(s), forming an engine block. Nevertheless, the area around the crankshaft is still usually called the crankcase. Crankcases and other basic engine structural components (e.g., cylinders, cylinder blocks, cylinder heads, and integrated combinations thereof) are typically made of cast iron or cast aluminium via sand casting. Today the foundry processes are usually highly automated, with a few skilled workers to manage the casting of thousands of parts. A crankcase often has an opening in the bottom to which an oil pan is attached with a gasketed bolted joint. Some crankcase designs fully surround the crank's main bearing journals, whereas many others form only one half, with a bearing cap forming the other. Some crankcase areas require no structural strength from the oil pan itself (in which case the oil pan is typically stamped from sheet steel), whereas other crankcase designs do (in which case the oil pan is a casting in its own right). Both the crankcase and any rigid cast oil pan often have reinforcing ribs cast into them, as well as bosses which are drilled and tapped to receive mounting screws/bolts for various other engine parts. Besides protecting the crankshaft and connecting rods from foreign objects, the crankcase serves other functions, depending on engine type. These include keeping the motor oil contained, usually hermetically or nearly hermetically (and in the hermetic variety, allowing the oil to be pressurized); providing the rigid structure with which to join the engine to the transmission; and in some cases, even constituting part of the frame of the vehicle (such as in many farm tractors). De Dion-Bouton engine from about 1905, in which can clearly be seen a discrete crankcase with upper and lower halves (each a casting), with the bottom half constituting both part of the main bearing support and also an oil sump. Two-stroke engines Small engines and crankcase compression engines Two-stroke crankcase-compression petrol engine A large number of small two-stroke engines use a sealed crankcase as a compression chamber for their mixture. These are very common as petrol or gasoline small engines for motorcycles, generator sets and garden equipment. Both sides of the piston are used as working surfaces: the upper side is the power piston, the lower side acts as a scavenging pump. As the piston rises, it pushes out exhaust gases and produces a partial vacuum in the crankcase, which draws in fuel and air. As the piston...

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Hybrid turbocharger

A hybrid turbocharger is an electric turbocharger consisting of a high speed turbine-generator and a high speed electric air compressor. The turbine and compressor are high-speed aeromachines, as in a conventional turbocharger. The electrical motors run at speeds in excess of 120,000 rpm and when used as generators, generate electricity at up to 98.5% electrical efficiency. High electrical efficiency is paramount, because there is no mechanical link between the turbine and compressor. In other words, hybrid turbocharger refers to a series hybrid setup, in which compressor speed and power are independent from turbine speed and power. This design flexibility leads to further improvements in turbine and compressor efficiency, beyond a conventional turbocharger. Basic schematic of an Aeristech Hybrid Turbocharger Aeristech 2009 prototype electric compressor Physical arrangement The electric motors utilize permanent magnets which have a higher efficiency than standard high speed induction motors. Induction motors induce an electro-magnetic field into a solid rotor core. Operating modes Acceleration mode for an HTT Turbocharger Acceleration When the driver depresses the throttle, the HTT initially acts like an electric supercharger. The compressor motor is powered from the energy storage medium allowing it to accelerate to full operating speed in <500 ms. This rate of acceleration eliminates the turbo lag which is a major limiting factor on the performance of standard turbocharged engines. During this transient stage, the engine control unit (ECU) on a standard turbocharged engine uses a combination of sensors such as lambda sensors and air mass flow sensors to regulate the fuel flow rate. In an HTT equipped engine the ECU can deliver the precise fuel flow rate for complete combustion more accurately. This is achieved by directly controlling the air flow rate and boost pressure via control of the compressor speed. Charging Charging mode for an HTT Turbocharger At high engine speeds there is more energy generated by the turbine than is required by the compressor. Under these conditions, the excess energy can be used to recharge the energy storage for the next acceleration phase or used to power some of the auxiliary loads such as an electric air conditioning system. When combined with a variable geometry turbine, the back pressure on the engine can be varied according to the electrical demands of the vehicle and charge state of the energy storage medium. Development is underway for replacing battery energy storage with a super capacitor which can be charged and discharged very quickly. Steady state For the majority of the time the hybrid turbocharger is operating, the compressor and turbine power (not necessarily speed) will be matched. This gives an extra degree...

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Internal combustion engine

An internal combustion engine (ICE) is a heat engine where the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is 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 typically 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 (see Otto engine). The term internal combustion engine usually 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 previously described. Firearms are also 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 even liquid sodium, heated in a boiler. ICEs are usually powered by energy-dense fuels such as gasoline or diesel, 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, aircraft, and boats. Typically 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 compression ignition engines and bioethanol or methanol for spark ignition engines. Hydrogen is sometimes used, and can be obtained from either fossil fuels or renewable energy. Diagram of a cylinder as found in 4-stroke gasoline engines.: C – crankshaft. E – exhaust camshaft. I – inlet camshaft. P – piston. R – connecting rod. S – spark plug. V – valves. red: exhaust, blue: intake. W – cooling water jacket. gray structure – engine block. Diagram describing the ideal combustion cycle by Carnot History 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. Also in 1794, Robert Street patented an internal combustion engine, which was also the first to use liquid fuel, and built an engine around that time. In 1798, John Stevens built the first American internal combustion engine. In 1807, French engineers Nicéphore (who went on to invent photography) and Claude Niépce ran a prototype internal combustion engine, using controlled dust explosions, the Pyréolophore. This engine powered a boat on the Saône river, 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...

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Diesel engine

The diesel engine (also known as a compression-ignition or CI engine), named after Rudolf Diesel, is an internal combustion engine in which ignition of the fuel which is injected into the combustion chamber is caused by the elevated temperature of the air in the cylinder due to mechanical compression (adiabatic compression). Diesel engines work by compressing only the air. This increases the air temperature inside the cylinder to such a high degree that atomised diesel fuel that is injected into the combustion chamber ignites spontaneously. This contrasts with spark-ignition engines such as a petrol engine (gasoline engine) or gas engine (using a gaseous fuel as opposed to petrol), which use a spark plug to ignite an air-fuel mixture. In diesel engines, glow plugs (combustion chamber pre-warmers) may be used to aid starting in cold weather, or when the engine uses a lower compression-ratio, or both. The original diesel engine operates on the "constant pressure" cycle of gradual combustion and produces no audible knock. A diesel engine built by MAN AG in 1906   Detroit Diesel timing Fairbanks Morse model 32 The diesel engine has the highest thermal efficiency (engine efficiency) of any practical internal or external combustion engine due to its very high expansion ratio and inherent lean burn which enables heat dissipation by the excess air. A small efficiency loss is also avoided compared to two-stroke non-direct-injection gasoline engines since unburned fuel is not present at valve overlap and therefore no fuel goes directly from the intake/injection to the exhaust. Low-speed diesel engines (as used in ships and other applications where overall engine weight is relatively unimportant) can have a thermal efficiency that exceeds 50%. Diesel engines may be designed as either two-stroke or four-stroke cycles. They were originally used as a more efficient replacement for stationary steam engines. Since the 1910s they have been used in submarines and ships. Use in locomotives, trucks, heavy equipment and electricity generation plants followed later. In the 1930s, they slowly began to be used in a few automobiles. Since the 1970s, the use of diesel engines in larger on-road and off-road vehicles in the US increased. According to the British Society of Motor Manufacturing and Traders, the EU average for diesel cars accounts for 50% of the total sold, including 70% in France and 38% in the UK. The world's largest diesel engine put in service in 2006 is currently a Wärtsilä-Sulzer RTA96-C Common Rail marine diesel, which produces a peak power output of 84.42 MW (113,210 hp) at 102 rpm. History Diesel's prototype engine Diesel's first experimental engine 1893 Hot bulb engine The definition of a "Diesel" engine to many has become an engine that uses compression ignition. To some it may be an engine that uses heavy fuel oil. To others an engine that does not use spark ignition....

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