EvoBus GmbH equips its Mercedes Benz and Setra urban and rural regular-service buses with low-emission technology to effectively counteract the much-discussed problem of environmental pollution in inner-city areas.
BlueTec diesel technology with highly efficient filter system
The first Mercedes Benz Citaro urban buses to feature the new BlueTec diesel technology from DaimlerChrysler have been taking part in field tests to prove their everyday practicality for the past six months or so. These buses already comply with the Euro 4 emission standard due to come into force in October 2006. Thanks to the new technology, particulate and soot emissions have been reduced by up to 94 % compared to exhaust-emission levels at the beginning of the 1990s, whilst nitrogen oxide emissions have been cut by up to 86 %.
There are two components at the heart of the new BlueTec diesel technology developed by DaimlerChrysler: enhanced engines and an effective exhaust-gas after-treatment system. Such is the efficiency of the combustion process at work that the levels of particulate and soot emissions are as low as in filtered exhaust gases. Working on the SCR principle, the integrated exhaust-gas aftertreatment system then helps to ensure the controlled conversion of harmful nitrogen oxides into harmless nitrogen and water vapour in a catalytic converter, with an aqueous solution being added as a reducing agent. In combination with BlueTec, this solution goes by the name of „AdBlue“. Under the supervision of the engine management system, the required amount of AdBlue is drawn from the separate AdBlue tank and injected into the hot exhaust stream where it is hydrolysed into ammonia. This process then sets in motion a chemical reaction after which, essentially, only the normal constituents of air (nitrogen, water and CO2) are released and emitted.
This technology holds much promise for the future since, as well as ensuring compliance with the Euro 4 emission standard, it is also capable of attaining the Euro 5 limits due to come into force in 2008/2009. This is illustrated by the fact that BlueTec recently received the „Goldener Öltropfen“ („Golden Drop of Oil“) energy and environment award. BlueTec diesel technology will be used in Mercedes Benz and Setra touring coaches and regular-service buses.
Enhanced diesel engines
The Mercedes-Benz diesel engines installed in the new BlueTec buses and coaches have been significantly enhanced to further boost the fuel economy of the BlueTec technology. One of the main objectives during development of the BlueTec engines was to further reduce untreated emissions by clearly focusing on achieving the cleanest possible combustion with the lowest possible amount of particulate matter whilst also ensuring lower fuel consumption than in other processes. Two of the main tasks involved increasing the compression ratio and boosting the ignition pressure. The new fully electronic pump-line-nozzle engine management system controls the selective, load point-based fuel injection by means of newly developed injection nozzles. Furthermore, the cast structure of the cylinder heads, the con-necting rod and crankshaft bearings and the entire sealing system have all been adapted to cope with the higher pressures and the resultant loads exerted on the components. O rings have been used to further optimise the intake valves, exhaust valves and the valve seals. As a result of these and other individual measures, the new generation of BlueTec engines ensures extremely low emissions and economical operation without compromising on the familiar high levels of reliability and durability.
Supply of AdBlue assured
A Europe-wide AdBlue infrastructure at public filling stations is currently being set up, whilst supplies of AdBlue are being assured by mineral oil and chemical compa-nies. Public transport companies can already refuel at their own pumps or special AdBlue filling stations without any problems. The AdBlue is added at the same time as the diesel when refuelling thanks to a second filler neck right next to the diesel filler neck. Whilst the diesel is being pumped into the main fuel tank, AdBlue simply flows into the SCR tank via the second nozzle without any loss of time.
AdBlue consumption in the new Euro 4 BlueTec engines works out at around four percent of diesel consumption. Since the AdBlue tank in the Citaro urban buses supplied to date holds 38 litres, the vehicles are generally able to carry enough AdBlue for two full tanks of diesel. If the onboard supply of AdBlue starts to run out, a light on the instrument panel comes on to inform the driver in plenty of time. Further key advantages of BlueTec include the fact that the engines are not necessarily dependent on low-sulphur diesel and can therefore be used all over Europe without any problems. BlueTec is designed to last for the entire lifespan of the vehicle and requires practically no maintenance.
More than 50 % of Germany’s urban buses equipped with particulate filter
In order to match the performance of Euro 4 and Euro 5 vehicles – which reduce particulate emissions to scarcely measurable levels by means of a complex in-engine process – today’s Euro 3 vehicles require a particulate filter. Particulate filters have been offered as special equipment for Mercedes Benz and Setra urban and rural regular-service buses fitted with Euro 3 or Euro 2 engines since 1997. More than 50 % of the urban buses already delivered in Germany, for example, are fitted with this type of filter.
Fixed-price filter retrofits
Since cutting emissions has become so important in regular-service applications, EvoBus GmbH now offers a wide range of fixed-price filter retrofit options for vehicles already in service – including all urban and rural-service buses with Euro 3 engines and some vehicles with Euro 2 engines – available through its Omniplus service network in Germany. Only particulate filters that have been tested and then approved by the manufacturer are used. Customers can obtain detailed information and advice regarding retrofit solutions by contacting one of the EvoBus GmbH
Service Centres or any of the authorised service outlets in Germany.
Low-emission natural gas drive systems have been available alongside the economical diesel powerplants for buses and coaches for many years. As part of standard specification, the M 447 hLAG natural-gas engine with lambda control and an oxidising catalytic converter ensures full compliance with the Euro 4 emission standard. EEV certification, which fulfils the requirements of the Euro 5 emission standard due to come into force in 2008/2009, is available as an option.