Innovative EGR management with charge air valve

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Stuttgart, September 2008—With optimal exhaust gas recirculation, the raw emissions of diesel engines can be significantly and sustainably reduced. An innovative, fast-switching charge air valve specifically affects the pressure ratios in the charge air line.

The exhaust gas standard Euro 6 and the US 2010 emissions limits for diesel engines in commercial vehicles are targeting a future decrease in nitrogen oide and particle emissions of more than 97 percent. These limits can be met only by achieving low raw emissions, due to the limited conversion rates of modern exhaust gas treatment systems.

Externally cooled exhaust gas recirculation is extremely efficient for engine-internal reduction of nitrogen oide (NOx) emissions. However, small pressure differentials between the exhaust and intake sides, as well as pressure drops in the exhaust gas recirculation, prevent high EGR rates. MAHLE engineers have therefore developed a technology that allows high EGR rates with optimal reliability and, at the same time, low fuel consumption.

Innovative charge air valve
The charge air valve consists of a continually rotating flap in the charge air line, above the inlet location for the exhaust gas recirculation. The flap is driven by an electric motor. Because the recirculating exhaust flow does not impinge on it, there is no relevant risk of contamination.

Closing the valve briefly causes a temporary loss of pressure in the charge air line. This increases the pressure differential between the exhaust gas and charge air line, and a significantly greater mass flow of exhaust gas can be mixed into the charge air.
The flap is freely controllable, and can thus be opened or closed as a function of the speed or the intake valve control times. In this manner, the innovative MAHLE charge air valve increases the EGR rate, and thus reduces both specific nitrogen oide emissions and fuel consumption. Depending on the design of the turbo-charger system, the charge exchange work and the peak cylinder pressure are reduced.

According to successful tests in various commercial vehicle engines, MAHLE has begun series production development of the innovative charge air valve. Meanwhile, MAHLE is developing a charge air valve that controls two air flaps with just one electric motor. The vehicle and engine manufacturers will thereby have a product that is optimized for cost and package constraint, to fulfill current and future emissions standards.

The MAHLE Group is one of the 30 largest companies in the automotive supply industry worldwide. As a leading manufacturer of components and systems for the combustion engine and related products, MAHLE ranks among the top 3 systems suppliers for piston systems, cylinder components, valve train systems, air management systems, and liquid management systems. MAHLE employs around 48,000 people at 110 production plants and eight research and development centers. In 2007, MAHLE achieved sales of over EUR 5 billion (USD 7.5 billion).


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