Exhaust Gas Recirculation (EGR) in combination with Turbocharging Technology is one of the decisive enablers for the Diesel engine to meet today's emission regulations. the cost/benefit ratio of SCR for example, or NO(x)-traps and the performance of EGR-Boost systems will determine the future Diesel engine system configurations. The Diesel Particulate Filter (DPF) can be seen as an essential element herein. Based on this basic question this lecture deals with different engine breathing systems taking into account the special needs of turbochargers and the interaction between EGR and boosting technology. The investigation has been made with a calibrated simulation model. HP-EGR-systems take the exhaust before the turbine via an ECU controlled EGR valve to the air intake. For better breathing efficiency, EGR-coolers are being applied. These devices can deal with high temperature differences and particulate load in the exhaust. In addition, the application of gas/water charge air coolers may meet special package requirements. For advanced EGR-concepts like US 07 or EU 5 the turbocharger may not be able to deliver the necessary mixture of fresh air and exhaust to the combustion engine. Low pressure loop EGR is a well known technology that offers an alternative to meet the requirements mentioned above. Before the market introduction of the Diesel particulate filter (DPF), the entire air intake system including the compressor would have been subject to deposit formation. This was one of the main reasons that limited the application of this kind of system. The DPF can be therefore seen as the enabler of LP-EGR. Air mass flow is increased when replacing HP-EGR by LP-EGR. The turbine flow (not shown) is also influenced positively; better compressor efficiencies are obvious. EGR-systems will enable Diesel engines to breathe even more exhaust than today. LP-systems will allow lower NO(x) emissions without any after treatment, which will help to keep system costs, weight and complexity down. The single stage cooled LP-system offers the most advantages based on the number of points and parameters. The established HP-system offers advantages like compact packaging, low compressor intake temperatures even at high power outputs, and a low exposure of components to water and acid. The thermodynamic disadvantages have been explained and limit the HP-capabilities significantly. The LP-System, just enabled by the DPF, is new and seem to consume package volume, which can be limited by smart designs like closed coupled filters and catalysts. Water and acid precipitation are subject to current development to limit or exclude their impact in the future.
Future breathing system requirements for clean diesel engines
Der schadstoffarme Dieselmotor und seine zukünftigen Anforderungen an moderne Beatmungssysteme
2005
16 Seiten, 20 Bilder, 4 Quellen
Conference paper
English
Future breathing system requierements for clean diesel engines
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