Pressure wave supercharger

pressure wave supercharger (also known as a wave rotor[1]) 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.[2][3][4] 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. [5] 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.[6] 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.[4] 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.[7][8]

 

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 less of a problem in a diesel than a petrol engine, hence the Comprex’s rarity in petrol-engined applications.[9][10]

Control system

A control system, to optimise performance, was patented in 1986 by Hachiro Aoki for Diesel Kiki Co. Ltd., Tokyo, Japan – United States Patent 4563997.[11]

References

  1. What is a Wave Rotor
  2. EP 0286931 Mayer, Andreas: “Freilaufender Druckwellenlader”, issued 1988-10-19, assigned to BBC Brown Boveri AG, Baden, Switzerland
  3. US 4838234 Mayer, Andreas: “Free-running pressure wave supercharger”, issued 1989-07-13, assigned to BBC Brown Boveri AG, Baden, Switzerland
  4. a b A Review of Wave Rotor Technology and its Applications including details of Comprex supercharger
  5. Hannu Niskanen ‘From Munktells to Valtra’
  6. Ferrari, Hans Tanner & Doug Nye, 1985
  7. Wave Rotor Topping Cycles for Gas Turbine Engine
  8. Wave Rotor Technology Tested Successfully
  9. Renaux, Jean-Jacques (1984-02-23). “Volkswagen soulève un coin du voile: Wunderbar!” [VW raises the veil: Wunderbar!]. Le Moniteur de l’Automobile (in French). Brussels, Belgium: Editions Auto-Magazine. 35 (789): 6–7.
  10. Chen, Jay (May 2007). “The Comprex: The Other Compressor”. Modified Mag. Retrieved Nov 2012. Check date values in: |accessdate= (help)
  11. http://www.freepatentsonline.com/4563997.html
Supercharger A supercharger is an air compressor that increases the pressure or density of air supplied to an internal combustion engine. This gives each intake cycle of the engine more oxygen, letting it burn more fuel and do more work, thus increasing power. Power for the supercharger can be provided mechanically by means of a belt, gear, shaft, or chain connected to the engine's crankshaft. Common usage restricts the term supercharger to mechanically driven units; when power is instead provided by a turbine powered by exhaust gas, a supercharger is known as a turbocharger or just a turbo - or in the past a turbosupercharger. Roots type supercharger on AMC V8 engine for dragstrip racing History In 1848 or 1849, G. Jones of Birmingham, England brought out a Roots-style compressor. In 1860, brothers Philander and Francis Marion Roots, founders of Roots Blower Company of Connersville, Indiana, patented the design for an air mover for use in blast furnaces and other industrial app...
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 ...
Turbocharger A turbocharger, or colloquially turbo, is a turbine-driven forced induction device that increases an internal combustion engine's efficiency and power output by forcing extra air into the combustion chamber. This improvement over a naturally aspirated engine's power output is due to the fact that the compressor can force more air—and proportionately more fuel—into the combustion chamber than atmospheric pressure (and for that matter, ram air intakes) alone. Turbochargers were originally known as turbosuperchargers when all forced induction devices were classified as superchargers. Today the term "supercharger" is typically applied only to mechanically driven forced induction devices. The key difference between a turbocharger and a conventional supercharger is that a supercharger is mechanically driven by the engine, often through a belt connected to the crankshaft, whereas a turbocharger is powered by a turbine driven by the engine's exhaust gas. Compared with a mechanically driven ...
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 efficie...
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 typicall...