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Dániel Szőllősi and Peter Prof. Kiss
Diesel engines are commonly found in off-road, agricultural and forestry equipment because of giving the best option in terms of weight, range and fuel storage. Given the current potential of electric powertrains, in this area, electrification does not seem to be competitive in the near future. Regulations tighthening for on road (EURO7) and non-road vehicles (Tier 4, Stage V) in many parts of the world and tends increasingly focusing on to ensure that as many as possible of the vehicles with low or no emission standard can be retrofitted to reach decreasing emissions. The overwhelming majority of vehicles fall into this category, around the world. Retrofitting should be as simple and cost-effective as possible. One such option could be the retrofitting with water injection systems. The exhaust gas recirculation (EGR) achieves the lower temperature required for reduced nitrogen-oxide (NOx) emissions by reducing the oxygen content and thus impairing combustion, water injection achieves this essentially by enriching the charge air and thus increasing its heat capacity and by the heat dissipation effect of the liquid-vapour phase change. Contrary to common belief, the two techniques are not only able to reduce NOx separately, but also together they cause further emission reductions on NOx and on other emission components. This has been shown through the use of practical applications, as the operation of EGR and water injection is linked to different engine operating conditions. This is also an important achievement, as it means that when the water injection system is installed in an existing vehicle, after that only software intervention is needed to make the system work properly and reach the emission reductions.
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