|The MAN D08 CR engines meet Euro 5 and EEV limits without any SCR aftertreatment. Click to enlarge.|
At the 62nd IAA Commercial Vehicles show in Hanover, Germany (25 September - 2 October), MAN Nutzfahrzeuge will premiere a range of new diesel engines with EGR (exhaust gas recirculation) that meet Euro 5 and EEV (Enhanced Environmentally-friendly Vehicles) standards without the use of urea-based selective catalytic reduction (SCR) aftertreatment systems, as well as new hybrid models and numerous changes to its vehicles.
To achieve Euro 5 / EEV, the MAN engine designers use a Lambda-controlled exhaust gas recirculation (EGR) with recirculation rates of 30% and higher; two-stage turbocharging with indirect intermediate and main intercooling; and common rail technology with high injection pressures of up to 1,800 bar.
The new Euro 5 and EEV MAN engines are based on the 10.5-liter, 6-cylinder D20 CR and the 12.4-liter, 6-cylinder D26 CR series, while the 4.6-liter and 6.9-liter 6-cylinder light-weight and medium-weight diesel engines from the D08 CR series have been fundamentally reworked. Certain versions of the heavier-duty engines will require SCR to achieve EEV.
The high EGR rate provides a lower temperature of the fresh air/exhaust gas mixture in the combustion chamber of the cylinder in combination with an improved cooling of the recirculated exhaust gases, resulting in less NOx generated during combustion.
The optimum EGR rate is set for each operating point of the engine even under dynamic conditions thanks to the new EGR regulation with the aid of a Lambda sensor. This also improves fuel consumption.
The turbocharging of the new Euro 5 / EEV engine has been adjusted to the higher requirements on exhaust gas. The maximum charge-air pressure has been increased to 4.0 bar for the engine series D08 for trucks. With the exception of the 110 kW / 150 hp variant, which is particularly sensitive to weight and price, all MAN common rail engines with EGR now have the two-stage turbocharging.
The high-pressure stage provides a quick charge-air pressure build-up in the lower load range and engine speed range and thus a high starting torque, while the low-pressure stage in the upper load range and engine speed range is marked by a particularly high efficiency rate. In addition, the interaction of the two pressure stages results in a lower charging of the individual turbochargers.
MAN uses cooled EGR depending on the vehicle and engine model. Part of the coolant is removed from the engine’s coolant circuit behind the water pump, guided over a low-temperature radiator on the vehicle, and cooled to a few degrees Kelvin above the outside temperature. Subsequently the coolant is applied to two engine-mounted charge-air coolers (low pressure and high pressure heat exchangers) and is used for efficient cooling of the charge air. The design also removes the large charge-air pipe on the front of the truck, enabling the resulting space to be used to enlarge the radiator. Due to the high efficiency rate of air/water heat exchangers, a better charge-air cooling is achieved, according to MAN.
To maintain particulate emissions at the required 20 mg/kWh, the EGR engines for Euro 5 are equipped with an oxidizing catalytic converter. The MAN EGR engines do not need a closed particulate filter even to comply with the stricter EEV standard, according to the company.
Hybrids. A new MAN TGL distribution truck with hybrid-electric drive will make its world debut at the IAA. MAN will also showcase the series diesel-electric MAN Lion’s City Hybrid, a prototype of which was shown in 2007 and which is due to enter series production by 2010. The Lion’s City series hybrid is equipped with a D08 EEV engine offers potential savings of up to 30% as compared with a conventional EEV diesel bus.
MAN Nutzfahrzeuge is the largest company in Germany’s MAN Group, and a leading international provider of commercial vehicles and other transport solutions.