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Press release MAN Nutzfahrzeuge Gruppe, Engines and Components______________________________________________________ 4 MAN engines and their innovative technology Common-rail injection system MAN uses the common-rail injection system throughout its range of engines for mobile machinery. MAN was the first engine manufacturer to introduce this technology and has been using it successfully for many years. The targeted direct fuel injection under high pressure reduces the exhaust-gas emissions and has a positive effect on the fuel consumption too. In the common-rail system every injection nozzle has the same pressure potential thanks to the common rail (fuel distributor). Targeted atomisation of the fuel through the electromagnetically actuated eight-hole nozzles is achieved in the injection process. As the injection pressure is built up independently of the load and the engine speed, a freely selectable common-rail system pressure can be provided over the engine's entire operating range. Even at low speeds optimum injection with practically ideal atomisation under a high injection pressure is possible. The injection timing and duration are determined by the EDC control unit via electrically triggered solenoid valves according to the machinery's operating mode. For this the machinery's power and speed requirements for the engine are set via the CAN control system. The injection quantity is split into a pilot and a main injection, by which a more favourable rise in the combustion pressure is achieved. This multiple injection makes for a much softer combustion. This results in a further advantage: noise emissions are significantly reduced, particularly during idling and under partial load. However, the decisive advantage of common-rail injection is that the system pressure, injection time and injection quantity can be ideally matched to the engine's operating mode at any time. High injection pressures at low engine speeds permit a high torque with low smoke values, while low injection pressures under partial load lead to optimised NOx values and optimum fuel consumption. At full load high injection pressures allow high exhaust-gas recirculation rates and low particulate emissions while the fuel consumption remains favourable. Two-stage turbocharging with external exhaust-gas recirculation (EGR) Two-stage turbocharging makes it possible to achieve low emissions without any loss of power. For this the thermal energy in the exhaust gas is used in the turbochargers to drive the turbines. At low speeds the first (high-pressure) stage receives 100 % of the exhaust gas, which increases the volumetric efficiency in the cylinders and leads to a very fast torque increase. At higher engine speeds some of the exhaust gas is conducted past the high-pressure turbine via a waste gate, which increases the amount of exhaust gas reaching the turbine in the second (low-pressure) stage. The main advantage is that two-stage
Press release MAN Nutzfahrzeuge Gruppe, Engines and Components______________________________________________________ 5 turbocharging makes it possible to retain the maximum torque over a wide speed range. To reduce emissions of nitrogen oxides, external exhaust-gas recirculation (EGR) is used. Here part of the exhaust gas is conducted back to the combustion chamber via an EGR cooler, through which coolant flows. In the combustion chamber it is mixed with the charge air in the intake tract via avalve. The oxygen surplus in the cylinder charge is thus reduced, the peak combustion temperature falls and fewer nitrogen oxides are formed. If the injection time is adjusted accordingly the fuel consumption can be reduced further. The D08, D20 and D26 engines are equipped with two-stage turbocharging and EGR. EGR is continuously controlled, has a recirculation rate of up to 30 % and reliably cuts the oxides of nitrogen inside the engine, bringing them down below the statutory limits. SCR exhaust-gas cleaning system For the D28 V engines and the D20/D26 series MAN offers an SCR (Selective Catalytic Reduction) exhaust-gas cleaning system under the name of MAN AdBlue®. To reduce emissions of nitrogen oxides the reducing agent AdBlue® – a non-toxic and odourless urea-water-solution – is sprayed into the exhaustgas flow. In the reducing catalyst the AdBlue® converts the nitrogen oxides into water vapour and elementary nitrogen, a natural constituent of the ambient air. This technology cuts NOx by over 80%. Engine design and materials If break mean effictive pressures and ignition pressures are to be achieved, high-strength materials and a rigid engine block design are needed. The crankcases of the D20, D26 and D28 engine ranges are made of high-quality CGI-450 (compacted graphite iron). This material is much stronger than grey cast iron. Beside this, the main bearings in the D20 and D26 engines are cracked, i.e. subjected to controlled breaking. In the crack system the bearing points are notched at both sides in a laser station and in the next step blasted off by means of a hydraulic mandrel. No further machining is necessary, but exact fixing of the bearings with positive locking is achieved. Transverse loads can be optimally absorbed thanks to the rough contact faces. The D08, D20 and D26 engine ranges have one-piece cylinder heads, which leads to extremely high rigidity. Engine components where strength is critical, such as pistons and conrods, are made of light but high-strength materials and thus provide sufficient reserves for the higher ignition pressures and break mean effective pressures. Another special feature in the design of the D20 and D26 ranges is that they have overhead camshafts with four valves per cylinder,
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