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New ACE Diesel Engine with Biodiesel Cuts NOx Emissions 80%

The Nikkei Business Daily reports that New ACE Institute Co. and the National Traffic Safety and Environment Laboratory have developed diesel engine technology that reduces emissions of oxides of nitrogen from engines fueled by rapeseed-based biodiesel blends by 80%.

The engine uses a combination of Exhaust Gas Recirculation (EGR) and a high-boost strategy that runs combustion at triple the pressure of naturally aspirated diesel engines. New ACE, founded in 1992, is a consortium funded by Hino Motors, Ltd.; Isuzu Motors Ltd.; Mitsubishi Fuso Truck & Bus Corp.; and Nissan Diesel Motor Co., Ltd. to pursue new diesel combustion strategies aimed at reducing the exhaust emissions and increasing thermal efficiency for future heavy duty diesel engines.

New ACE has been investigating engine technologies using a combination of EGR, high-boost, high-pressure injection and flexible intake and exhaust valve strategies.

In August 2006, New ACE recognized Sturman Industries—the digital valve company—for its cooperation in research. Sturman Industries has supplied New ACE with Hydraulic Valve Actuation and intensified fuel injection systems. These proprietary technologies rely on the miniature, ultra fast, and energy efficient Sturman Digital Valves. The Digital Valves, when integrated with advanced hydraulics control systems and intelligent electronics, are an enabling technology to control the combustion process.

Earlier this year, New ACE researchers published a paper describing their use of a high-boost (5x naturally aspirated pressure) and high-pressure (200 MPa or 2,000 bar) fuel injection in a single-cylinder engine to deliver improvements in combustion and brake thermal efficiency with low PM and NOx.




GM also cojured up a similar hydraulically actuated valve system, but for Otto engines. Thusfar, it has come to Cylinder Deactivation, and not camless IVVT/CVVT for Otto or diesel.

Rafael Seidl

Hydraulic valve actuation is used on very large marine diesels but was considered too expensive for automotive applications. The technology competes with electromagnetic camless systems. Both systems couple the valve timing and crankshaft angle via flexible software, analogous to the way common rail technology affects the fuel injection timing.

Hydraulic valve actuation is particularly good at rapid transitions between the open and closed states, hence the "digital valve" tag. The motion does need to be slowed considerably just prior to closing to avoid overly hard contact between the poppets and the valve seats. With that proviso, rapid valve actuation permits far more precise control of EGR rates, a key requirement for the effective reduction of engine-out NOx. Raising the boost pressure makes the combustion process far more tolerant of high EGR levels as the mean average distance between molecules that can react with one another is shorter. This also helps reduce the residual PM found in the exhaust gas, an undesirable side effect of high EGR concepts.

The main difficulty lies in constructing an engine that can withstand the very high thermal and mechanical loads of a high boost concept and still achieve the desired life expectancy. In addition, single-stage turbochargers max out between boost ratios of 4-5 due to thermal load on the compressor wheel. Such extreme turbos also exhibit a very narrow area of high efficiency, so they only make sense in HDV drivetrains featuring high gear counts and a high fraction of near-maximum load operation.

In diesel passenger cars, a similar high boost concept would require dual turbo systems such as those implemented by BMW for inline sixes and proposed by Peugeot for inline fours.

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