International Railway Journal - October 2008 - (Page 30) Advertisement Railway Diesel Drives by MTU: Clean & Economic Solutions The efficiency and specific power output of diesel engines has increased dramatically since the Flying Hamburger the first high-speed diesel-electric railcar - 75 years ago. Despite electrification, diesel engines will continue to play an important role in rail transport. MTU Friedrichshafen will continue to provide solutions for the railway industry that comply with exhaust gas regulations, and the economic and technical requirements of train operators. During the last few years, railway engine technology has taken a fascinating turn. Modern railcars for local services are furnished with low-emission diesel power units, offering outstanding efficiency. Significantly lower emission readings can be achieved on older locomotives through repowering. Despite performance enhancements, it has been possible to significantly reduce exhaust gas emissions through numerous internal engine design features. Since 1990, diesel emissions have been reduced by more than 80% within Deutsche Bahn AG. Fuel-saving and clean injection systems, powerful turbo-chargers, electronic engine control systems and exhaust gas after-treatment systems are the key technologies for powerful, fuel-efficient and low-emission diesel engines. Future emission tiers with extremely stringent limits will come into force at a rapid pace, which is why MTU is working closely with train manufacturers and operators. According to the German Railway Industry Association (VDB), the railway industry will have the required technical solutions for trains and locomotives with a power output of less than 560 kW. However, the industry has identified a conflict for diesel locomotives with a power output of more than 560 kW. Further reductions of particle and NOx emissions can only be achieved at the price of greater weight resulting in higher fuel consumption leading to increased CO2 emissions. Entirely new vehicle concepts are needed and a technological leap to produce reliable, tried and tested solutions quickly while keeping costs down. As a leader in engine research and development, MTU Friedrichshafen has geared up for this technological leap through a number of important projects. The “Taunusbahn” Project: first diesel railcar with particulate filters Since 2006, Hessische Landesbahn has been using 10 Coradia Lint type 41 diesel trains on behalf of Verkehrsverband Hochtaunus (VHT). These are the first trains in the world to be equipped with diesel particulate filters (DPF) and offer emission readings significantly below current legal limits. MTU Friedrichshafen has developed these particulate filters in cooperation with Hug Engineering and integrated them into the exhaust silencers of the PowerPack power unit. Two MTU 6H 1800 R82P PowerPacks power the Taunusbahn trains. The DPF is made from ceramic material. In the flow filter, all the exhaust gases are expelled by the diesel engine flow through the porous filter wall within an entirely enclosed system. Soot is separated and adheres to the filter material. This way, the amount of soot particles is reduced by more than 90%. With particle emissions of less than 0.025g/kWh, which corresponds to the particle mass emitted per hour of engine power output, these new regional trains not only fall below the current exhaust gas emission limits for railcars (0.20g/kWh), but they already comply with future EU exhaust gas regulations regarding soot particles coming into force in 2012. To prevent the filter from clogging up, the soot is burned off to end up as CO2 with the help of the engine waste heat and the residual oxygen in the exhaust gas (regeneration). Thanks to its catalytic coating, the regeneration process of the particulate filter can take place with normal exhaust gas temperatures of around 350°C. The non-combustible part of the separated particles is blown out by the help of pressurised air during regular maintenance. The “AERA” Project: exhaust gas recirculation successfully tested in shunting locomotives In November 2007, MTU successfully completed a research project by conducting trials with a Series 4000 railway engine with exhaust gas recirculation (EGR). MTU and Deutsche Bahn, the partners within this Advanced Engine for Future Rail Applications (AERA) project, are using a heavy V294 shunting locomotive to test pre-production technology in a 5,000-hour continuous test under normal operating conditions. Intake air is mixed with cooled exhaust gas within the exhaust gas recirculation process which lowers the combustion peak temperature and, subsequently, results in lower levels of nitrous oxides (NOx). The trial engine managed to achieve NOx readings of 5.4g/kWh and thus falls below the EU tier IIIA limits applicable in 2009. Trials were based on an 8-cylinder Series 4000 1,000kW rail engine. The next step towards standard production is the integration of the cooled exhaust gas recirculation into the design of the next generation of engines. The LOCEX Project: sophisticated exhaust gas after-treatment on trial Diesel engines with high injection pressures, multi-stage exhaust gas turbocharging and high exhaust gas recirculation rates are able to reach fairly low emission levels. However, increasingly stringent emission regulations also require a cleansing function for the exhaust gases that are being generated during the combustion process: exhaust gas aftertreatment (EGA). The core element is a structure consisting of highly efficient oxidation and NOx catalysts in combination with a diesel particulate filter. EGA systems must be robust, space-efficient and regenerative, and be economically viable. Within the Locomotive with Clean Exhaust Project (LOCEX), MTU, in cooperation with Deutsche Bahn, is developing an exhaust gas aftertreatment system that is feasible in terms of practicality, which can be retrofitted and comes with a low weight and a small footprint. The objective is to reduce soot particle and NOx emissions at low operating temperatures below the Tier IIIB emission levels while avoiding a significant rise in fuel consumption. A prototype EGA system integrated in a Series 4000 8V R41 engine in a V294 heavy shunting locomotive has been under test near Stuttgart for two years. Hybrid PowerPack: research for lower fuel consumption Generally, a decrease in noxious substance emissions causes a rise in fuel consumption and CO2 emissions. MTU has managed to optimise the combustion process so that fuel consumption has almost remained at the same level despite compliance with stringent emission limits. Nevertheless, we still want to reduce fuel consumption. Trials will be conducted from mid-2009 on a Series VT612 DMU equipped with an MTU 390 kW hybrid 6H 1800 PowerPack. Braking power will be stored and reused for accelerating when starting. The braking power will be stored in accumulators or “ultracaps” (capacitors) and converted into traction power by an electrical drive unit. http://www.mtu-online.com
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