Supercharging is the age-old method of increasing horsepower by forcing air into an engine under pressure, supplying it with more oxygen to burn more fuel and generate more power. It also has another use: that of supplying excess air to promote cleaner combustion (rather than increasing power), and in this role, as an air pump, one of the last examples of its use is by Mazda on its Skyactiv gasoline engines. .
The latest application of supercharging technology as a “blower” is that of Tenneco, which has partnered with supercharger maker Eaton to develop a Cold Start Thermal Unit (CSTU) for diesel cars and trucks. The focus here is not on internal combustion but on the exhaust system, and with Euro 7 regulations looming, the pressure remains to reduce emissions.
Even if ultra-low carbon synthetic fuels were to take off to reduce CO2 (and that’s a big ‘if’), there are still unwanted regulated emissions to get rid of, such as carbon oxides. nitrogen.
NOx is produced when hydrocarbons are burned with air, then oxygen and nitrogen combine to form nitrogen oxides. More NOx is produced at higher temperatures, and diesel engines produce more because they are lean burned and generate high temperature hot spots in the combustion chamber.
Ironically, a lot of heat is also needed to get rid of NOx, but that heat is needed in the exhaust rather than the engine. Catalytic converters, including the latest diesel Selective Catalytic Reduction (SCR) systems and Diesel Particulate Filters (DPFs) all need to reach high temperatures to operate, but the diesel exhaust is much cooler than the diesel exhaust. a gasoline engine due to the high efficiency of diesel.
More of the fuel is converted into torque, rather than wasted as heat of combustion. One way around this problem is to use direct-coupled catalytic converters, mounted as close to the engine as possible to capture the exhaust gases before they can cool. It works well, but packing a one-piece cat in the engine bay is inconvenient, and systems are still below peak efficiency in the first few seconds after cold cranking.
The new system combines a Roots mini-burn fan. “TVS” stands for Twin Vortices, and the Roots brothers were the original inventors of the twin-rotor positive displacement pump concept.
(Incidentally, the Roots blower was not invented to force-feed motors for increased power; it was originally designed as a blower for blast furnaces in the steel industry.) The blower pumps air through the CSTU burner, which injects and burns a small amount of fuel in the air stream, rapidly heating the catalysts and the DPF further downstream.
After the SCR catalyst reaches 200-250 ° C, it can effectively convert NOx to harmless nitrogen and water.
The system works well during the crucial cranking and warm-up phases, when most emissions are being generated and also when the engines are left at idle and begin to cool. It can work in both light vehicles (cars and vans) and heavy trucks, all of which will be subject to the much stricter Euro 7 rules when they come into effect in 2024 and 2027 for cars and trucks respectively.
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A consortium led by Chippenham Carbon ThreeSixty is developing the Acrim-Wheel, the first low-cost lightweight all-composite wheel commercially viable for niche and electric vehicles. The wheel is intended for testing on Gordon Murray Design’s Motiv autonomous vehicle and on a conventional car. A 15-inch wheel should weigh 50% less, reducing fuel consumption and CO2 emissions by 5%.
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Source: www.autocar.co.uk
This notice was published: 2021-04-25 23:01:23
