Pressure wave supercharger

A pressure wave supercharger (also known as a wave rotor) is a type of supercharger technology that harnesses the pressure waves produced by an internal combustion engine exhaust gas pulses to compress the intake air. Its automotive use is not widespread; the most widely used example is the Comprex, developed by Brown Boveri. Valmet Tractors of Finland were one of the first to use the device when they fitted it to the 411CX engine which powered their 1203 model of 1980. Although it provided a useful increase in performance it was considered too expensive to be incorporated into later models.  Ferrari tested such a device during the development of the 126C Formula One car. The system did not lend itself to as tidy an installation as the alternative twin-turbocharger layout, and the car was never raced in this form. A more successful application was in the RF series diesel enginefound in the 1988 Mazda 626 Capella; ultimately 150,000 Mazda diesel cars were fitted with a Comprex supercharger. Other users included Peugeot and Mercedes-Benz. The Greenpeace SmILE concept car uses a Hyprex pressure wave supercharger developed by the Swiss company Wenko AG. NASA uses wave rotors in experiments attempting to increase gas turbine efficiency. The wave rotor is placed between the compressor, combustor, and turbine sections in order to extract more energy from the combustion process.   US4563997 Fig1 Pressure wave supercharger Principle The 4 cycles of operation of the Pressure Wave Supercharger. The process is controlled by a cylindrical cell rotor driven by the engine crankshaft via a belt or chain. Individual cells alternately open and close the exhaust gas and fresh air apertures. When the aperture on the exhaust gas side is reached, pressurized exhaust gas flows into the cell and compresses the fresh air there (Diagram Stage 2). As the cell rotor continues to rotate and reaches the aperture on the inlet side, the compressed air flows to the engine (3). Before the exhaust gas can flow, the aperture is closed again and the exhaust gas column is reflected before entering the engine (4). The exhaust gas exits at high speed, sucking further intake air into the cell behind it, repeating the process (1). Advantages Energy exchange in the pressure-wave supercharger occurs at sound velocity, resulting in good response even at low engine speeds, a common downfall of turbocharged engines. It combines the advantages of mechanical and exhaust gas supercharging. Disadvantages The Comprex system has two shortcomings; one, that the exhaust gases intermingles with the fresh air needed for combustion, leading to some recirculation of burnt gas. Secondly, this co-mingling also raises the temperature of the intake gas. Both of these are much...

Read

Intercooler

An intercooler is any mechanical device used to cool a fluid, including liquids or gases, between stages of a multi-stage compression process, typically a heat exchanger that removes waste heat in a gas compressor. They are used in many applications, including air compressors, air conditioners, refrigerators, and gas turbines, and are widely known in automotive use as an air-to-air or air-to-liquid cooler for forced induction (turbocharged or supercharged) internal combustion engines to improve their volumetric efficiency by increasing intake air charge density through nearly isobaric (constant pressure) cooling.   The intercooler (top) of this 1910 Ingersoll Rand air compressor extracts waste heat between the two compressor stages. Air Compressors Intercoolers are utilized to remove the waste heat from the first stage of two-stage air compressors. Two-stage air compressors are manufactured because of their inherent efficiency. The cooling action of the intercooler is principally responsible for this higher efficiency. Removing the heat-of-compression from the discharge of the first stage has the effect of densifying the air charge. This, in-turn, allows the second stage to produce more work from its fixed compression ratio. Two-stage compressor pump showing location of the intercooler. Internal combustion engines Intercoolers increase the efficiency of the induction system by reducing induction air heat created by the supercharger or turbocharger and promoting more thorough combustion. This removes the heat of compression (i.e., the temperature rise) that occurs in any gas when its pressure is raised (i.e. its unit mass per unit volume - density - is increased). A decrease in intake air charge temperature sustains use of a more dense intake charge into the engine, as a result of forced induction. The lowering of the intake charge air temperature also eliminates the danger of pre-detonation (knock) of the fuel/air charge prior to timed spark ignition. This preserves the benefits of more fuel/air burn per engine cycle, increasing the output of the engine. Intercoolers also eliminate the need for using the wasteful method of lowering intake charge temperature by the injection of excess fuel into the cylinders' air induction chambers, to cool the intake air charge, prior to its flowing into the cylinders. This wasteful practice (before intercoolers were used) nearly eliminated the gain in engine efficiency from forced induction, but was necessitated by the greater need to prevent at all costs the engine damage that pre-detonation engine knocking causes. The inter prefix in the device name originates from its use as a cooler in between compression cycles. Typically in automobiles the intercooler is placed between the turbocharger (or supercharger) and the engine (the piston compression produces the next compression cycle). Aircraft engines are sometimes built with charge air coolers that were installed between multiple stages of forced induction, thus the designation of inter. In a vehicle fitted with two-stage...

Read

Variable-geometry turbocharger

Variable-geometry turbochargers (VGTs), (also known as variable nozzle turbines/VNTs), are a family of turbochargers, usually designed to allow the effective aspect ratio (A:R) of the turbo to be altered as conditions change. This is done because optimum aspect ratio at low engine speeds is very different from that at high engine speeds. If the aspect ratio is too large, the turbo will fail to create boost at low speeds; if the aspect ratio is too small, the turbo will choke the engine at high speeds, leading to high exhaust manifold pressures, high pumping losses, and ultimately lower power output. By altering the geometry of the turbine housing as the engine accelerates, the turbo's aspect ratio can be maintained at its optimum. Because of this, VGTs have a minimal amount of lag, have a low boost threshold, and are very efficient at higher engine speeds. VGTs do not require a wastegate. VGTs tend to be much more common on diesel engines as the lower exhaust temperatures mean they are less prone to failure. The few early gasoline-engine VGTs required significant pre-charge cooling to extend the turbocharger life to reasonable levels, but advances in material technology have improved their resistance to the high temperatures of gasoline engine exhaust and they have started to appear increasingly in, e.g., gasoline-engined sports cars.   Volvo FM VGT diesel engine with EGR emission technology Most common designs The two most common implementations include a ring of aerodynamically-shaped vanes in the turbine housing at the turbine inlet. In general, for light-duty engines (passenger cars, race cars, and light commercial vehicles), the vanes rotate in unison to vary the gas swirl angle and the cross sectional area. In general, for heavy-duty engines, the vanes do not rotate, but instead the axial width of the inlet is selectively blocked by an axially sliding wall (either the vanes are selectively covered by a moving slotted shroud or the vanes selectively move vs a stationary slotted shroud). Either way, the area between the tips of the vanes changes, leading to a variable aspect ratio. Actuation The vanes are controlled by a membrane vacuum actuator, electric servo actuation, 3-phase electric actuation, hydraulic actuator or air actuator using air-brake system pressure. Main suppliers The invention introducing the VNT was developed under Garrett (Honeywell) (called Allied-Signal at the time). Several companies supply the rotating vane type of variable-geometry turbocharger, including Garrett (Honeywell), Borg Warner, and Mitsubishi Heavy Industries (MHI). The rotating vane design is mostly limited to small engines and/or to light-duty applications (passenger cars, race cars and light commercial vehicles). Main supplier...

Read

Turbocharged direct injection

Turbocharged direct injection or TDI is a design of turbodiesel engines featuring turbocharging and cylinder-direct fuel injection that was developed and produced by the Volkswagen Group (VW AG). These TDI engines are widely used in all mainstream Volkswagen Group marquesof passenger cars and light commercial vehicles made by the company (particularly those sold in Europe). They are also used as marine enginesin Volkswagen Marine and Volkswagen Industrial Motor applications. TDI engines installed in 2009 to 2015 model year Volkswagen Group cars sold through 18 September 2015 had an emissions defeat device,which activated emissions controls only during emissions testing. The emissions controls were suppressed otherwise, allowing the TDI engines to exceed legal limits on emissions. VW has admitted to using the illegal device in its TDI diesel cars. In many countries, TDI is a registered trademark of Volkswagen AG. The TDI designation has also been used on vehicles powered by Land Rover-designed diesel engines. These are unrelated to Volkswagen Group engines. TDI badge TDI embossed on the engine cover Volkswagen Marine 3.0-litre V6 TDI 265-6 marine engine Volkswagen Group products which feature a TDI engine display a TDI badge Overview The TDI engine uses direct injection, where a fuel injector sprays atomised fuel directly into the main combustion chamber of each cylinder, rather than the pre-combustion chamber prevalent in older diesels which used indirect injection. The engine also uses forced induction by way of a turbocharger to increase the amount of air which is able to enter the engine cylinders, and most TDI engines also feature an intercooler to lower the temperature (and therefore increase the density) of the 'charged', or compressed air from the turbo, thereby increasing the amount of fuel that can be injected and combusted. These, in combination, allow for greater engine efficiency, and therefore greater power outputs (from a more complete combustion process compared to indirect injection), while also decreasing emissions and providing more torque than the non-turbo and non-direct injection petrol engined counterpart from VAG. Similar technology has been used by other automotive companies, but "TDI" specifically refers to these Volkswagen Group engines. Naturally aspirated direct-injection diesel engines (those without a turbocharger) made by Volkswagen Group use the Suction Diesel Injection (SDI) label. Because these engines are relatively low displacement and quite compact, they have a low surface area. The resulting reduced surface area of the direct injection diesel engine reduces heat losses, and thereby increases engine efficiency, at the expense of slightly increased combustion noise. A direct injection engine is also easier to start when cold, because of more efficient placing and usage of glowplugs. Direct injection turbodiesel engines are frequent winners of various prizes in the International Engine of the Year Awards. In 1999 in particular, six out of twelve categories were won by direct injection engines: three were Volkswagen, two were BMW, and one Audi. Notably that year, the Volkswagen Group 1.2 TDI 3 L beat the Toyota Prius to...

Read

Turbo-diesel

Turbo-diesel, also written as turbodiesel and turbo diesel, refers to any diesel engine equipped with a turbocharger. Turbocharging is common in modern car and truck diesel engines to produce higher power outputs, lower emissions levels, and improved efficiency from a similar capacity of engine. Turbo-diesels in automobiles offer a higher refinement level than their naturally aspirated counterparts. A diesel engine turbocharger History The turbocharger was invented in the early 20th century by Alfred Büchi, a Swiss engineer and the head of diesel engine research at Gebruder Sulzer engine manufacturing company in Winterthur. Büchi specifically intended his device to be used on diesel engines. His patent of 1905 noted the efficiency improvements that a turbocharger could bring to diesel engines  which in 1922 had first been developed for use in road transportation. At the time, metal and bearing technology was not sufficiently advanced to allow a practical turbocharger to be built. The first practical turbodiesels were marine engines fitted to two German passenger liners - the Danzig and the Preussen in 1923, each having two 10-cylinder engines of 2,500 horsepower (the naturally aspirated version of the same engine produced 1,750 HP). By the late 1920s, several diesel engine builders were making large turbodiesels for marine and stationary use, such as Sulzer Bros., MAN, Daimler-Benz, and Paxman. Turbocharger technology was improved greatly by developments during World War II and subsequent development of the gas turbine. It was now possible to use smaller turbochargers on smaller, higher-speed engines. Diesel locomotives with turbodiesels began appearing in the late 1940s and 1950s. In 1951 MAN presented a turbocharged version of their MK26 truck, although it was never put into mass production. Series production of turbocharged diesel trucks commenced in 1954, when both MAN 750TL1 and Volvo Titan Turbo were introduced to the markets. The building of the Interstate Highway System in the USA from 1956 made long-distance road transportation of goods more attractive. To keep up with general traffic, more powerful engines came in increasing demand. Cummins, Detroit, and CAT all had turbo-charging as an option by the late-1960s. In Europe, legislation was introduced in Germany mandating a minimum power-to-weight ratio for trucks; by the late 1960s, a 38-tonne consist had to have at least 304 hp. Most manufacturers met these requirement with large-displacement natural aspiration engines, some with the option of large-displacement or turbo-charging, while Scania and Volvo where among those that only provided turbocharged trucks that met the demands. Turbo-charging was not preferred initially as the engines were perceived to be less reliable, however the method won a decisive victory by the mid-1970s as the 1973 oil crisis increased fuel costs. The last market to see the absolute penetration of turbo diesels was Japan, where legislation on particle emissions effectively mandated natural aspiration engines until effective particle filters...

Read

Blowoff valve

A blowoff valve (BOV), dump valve or compressor bypass valve (CBV) is a pressure release system present in most turbocharged engines. Its main purpose is to take the strain off the turbo when the throttle is suddenly released. Characteristics A typical piston-type dump valve, used in auto racing. Unlike a blowoff valve, this one does not vent to the atmosphere. The small hose at the top is a feed from the intake manifold. A compressor bypass valve (CBV), also known as a pressure relief valve or diverter valve, is a manifold vacuum-actuated valve designed to release pressure in the intake system of a turbocharged vehicle when the throttle is lifted or closed. This air pressure is re-circulated back into the non-pressurized end of the intake (before the turbo) but after the mass airflow sensor. A blowoff valve, (sometimes "hooter valve" or BOV) performs the same task but releases the air into the atmosphere instead of recirculating it. This type of valve is typically an aftermarket modification. The blowoff action produces a range of distinctive hissing sounds, depending on the exit design. Some blowoff valves are sold with a trumpet-shaped exit that intentionally amplifies the sound. Some turbocharged vehicle owners may purchase a blowoff valve solely for the auditory effect even when the function is not required by normal engine operation. Motor sports governed by the FIA have made it illegal to vent unmuffled blowoff valves to the atmosphere. Blowoff valves are used to prevent compressor surge, a phenomenon that readily occurs when lifting off the throttle of an unvented, turbocharged engine. The sound produced is called turbo flutter (the slang term "choo-choo" is sometimes used). When the throttle plate on a turbocharged engine closes, the high pressure air in the intake system is trapped by the throttle and a pressure wave is forced back into the compressor, the resulting collision of pressure waves creates an effect similar to cavitation producing the unique noise. Operation When the throttle plate is open, the air pressure on both sides of the piston in the blow-off valve is equal and the spring keeps the piston down. When the throttle is closed, a vacuum forms in the manifold. This in combination with the pressurized air from the turbocharger moves the piston in the valve up, releasing the pressure into the inlet of the turbo (Recirc.) or the atmosphere (BOV). A blowoff valve is connected by a vacuum hose to the intake manifold after the throttle plate. When the throttle is closed, the relative manifold pressure drops below atmospheric pressure and the resulting pressure differential operates the blowoff valve's...

Read

Boost gauge

A boost gauge is a pressure gauge that indicates manifold air pressure or turbocharger or supercharger boost pressure in an internal combustion engine. They are commonly mounted on the dashboard, on the driver's side pillar, or in a radio slot. Turbochargers and superchargers are both engine-driven air compressors (exhaust-driven or mechanically driven, respectively) and provide varying levels of boost according to engine rpm, load etc. Quite often there is a power band within a given range of available boost pressure and it is an aid to performance driving to be aware of when that power band is being approached, in the same way a driver wants to be aware of engine rpm. A boost gauge is used to ensure excessive pressure is not being generated when boost pressure is being modified to levels higher than OEM standard on a production turbocharged car. Simple methods can be employed to increase factory boost levels, such as bleeding air off the wastegate diaphragm to 'fool' it into staying closed longer, or installing a boost controller. To prevent the Air-fuel ratio from going lean (caused by increasing the boost beyond the fuel systems capacity) care must be taken to monitor boost pressure levels, along with oxygen levels in the exhaust gas, using an air-fuel ratio meterthat monitors the oxygen sensor. A boost gauge will measure pressure in either psi or bar; many also measure manifold vacuum pressure in inches of mercury (in. Hg) or mm of mercury(mm Hg). Boost gauge on a Ford Focus RS (left) 30 psi Boost gauge Top: Turbo/APC boost gauge in a Saab 900 Notes Goodsell, Don. Dictionary of Automotive Engineering. ISBN 1-56091-683-4.

Read

12