In November 2011, the European Parliament and the European Commission adopted a new directive on limiting the exhaust gas emissions for the diesel engines of railway vehicles, in the eve of passing to a new phase, starting with January 1, 2012, the limit figures accepted so far.
Directive 97/68/EC refers to the measures against the emission of gaseous and particulate pollutants from internal combustion engines to be installed in non-road mobile machinery, with subsequent amendments and supplements, where the engines for multiple-units and locomotives are included in a different chapter. December 31, 2011 is a new threshold in limiting the level of gas emissions from diesel engines for railway traction. Starting with this date, the stage IIIB becomes effective which imposes an even more drastic cutting of the polluting emissions generated by diesel engines. Therefore, if in 2006, for the engines superior to 130 kW, dust emissions were limited to 0.2 g/kwh, starting with 2012, they will be limited to 0.025 g/kwh. Also the limit of hydrocarbon emissions decreases from 0.5 g/kwh in 2008 to 0.19 g/kwh from 2012.
On November 16, 2011, the European Parliament and the Council of the European Union have adopted a new directive, namely Directive 2011/88/EU that amends and completes the old directive. According to the new directive, it is possible to use the IIIA stage engines in the construction of locomotives through the flexibility programme which allows an equipment manufacturer to use a specific type of engine for another 3 years since the indicated date, but no more than 16 engines. Also, the directive assesses the possibility to approach the post-equipping with systems for the post-treatment of the gases generated or the existing fleet of railway vehicles, as well as the establishment of periodical testing methods for the rolling stock with special engines so as to make sure that their emission performance is compliant with the figures declared upon registration.
For diesel engine manufacturers, limiting the gas emissions is a constant concern for aligning to the legislative requirements of the EU and the reason why they seek innovative technical solutions. Among other requirements that have to be observed, reducing the NOx is made through the catalytic oxidation after burn, either by using a system to limit the temperatures that favour the formation of NOx or by recirculating part of the burned gases. According to the representatives of Caterpillar in Romania, the diesel engines for locomotives are equipped with the above-mentioned equipments and with filters for retaining particles (DPF – Diesel Particulate Filter), particles generated by still unburned elements coming from fuels or from the lubrication oil. “For controlling the hydrocarbons and the carbon oxide resulted from burned gases, we also apply the catalytic oxidation, the exhaust pipes including a Diesel Oxidation Catalyst (DOC). As the components included in the exhaust route of the burned gases have to occupy a reduced space, we couple the DOC with the DPF, resulting the so-called Clean Emission Module”, declared Gheorghe Robu, Sales Key Account, Eneria CAT.
An electronic system of diesel engine management is capable to interact precisely between the systems of the diesel engines and the pollution levels imposed by Directive EU 97/68/EC stage IIIB, according to the representatives of MTU Friedrichshafen in Romania. “For achieving an efficient combustion of fuel in the diesel engine, we have introduced, for the first time, the “common rail” system which realizes the combustion injection of the fuel in 3 stages and for eliminating the variation of the injection pressure in the combustion room, we have developed a new type of injector with an incorporated pressure battery. The injection pressure increased from 1,600 bar to 2,200 bar, and for the future MTU plans to increase the injection pressure to 2,500 bar”, declared Vasile Nicodim, Executive Manager, Service Faur S.R.L.
In order to align to the limits of polluting emissions regulated in the European directives and for reducing nitrogen oxides, MTU has developed new systems for supplementing the air supply of the engine. These systems are capable to reduce the temperature in the combustion room. The company has also introduced the EGR (Exhaust Gas Recirculation), which reintroduces in the suction gallery of the engine part of the exhaust gases after cooling them. The SCR (Selective Catalytic Reduction) system, relying on the injection of urea in the exhaust gases, the products being nitrogen and water, the nitrogen oxides are reduced by 90%. Also, through the DPF (Diesel Particulate Filter) system, which retains solid particles resulted from the combustion process in a ceramic filter, the electronic engine ma-nagement system increases for a specific period of time the temperature of exhaust gases so that the particles retained by the ceramic filter will burn. This method eliminates the need for the maintenance of the filter. All processes that contribute to reducing polluting emissions are efficiently controlled and monitored by the ADEC system for the management of the diesel engine for increasing the performance of engines.
[ by Teodor Turcu ]