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Diesel engine is presently facing the challenge of controlling NOx and soot emissions on transient cycles, to meet stricter emission norms and to control emissions during field operations. Development of a simulation tool for NOx and soot emissions prediction on transient operating cycles has become the most important objective, which can significantly reduce the experimentation time and cost required for tuning these emissions. Hence, in this work, a 0D comprehensive predictive model has been formulated with selection and coupling of appropriate combustion and emissions models to engine cycle models. Selected combustion and emissions models are further modified to improve their prediction accuracy in the full operating zone. Responses of the combustion and emissions models have been validated for load and “start of injection” changes. Model predicted transient fuel consumption, air handling system parameters, and NOx and soot emissions are in good agreement with measured data on a turbocharged high power density common rail engine for the “nonroad transient cycle” (NRTC). It can be concluded that 0D models can be used for prediction of transient emissions on modern engines. How the formulated approach can also be extended to transient emissions prediction for other applications and fuels is also discussed.

<div class="section abstract"><div class="htmlview paragraph">Air pollution in India and also global warming are two major concern in the country. To address this situation, India is moving from BS-IV to BS-VI for on-road applications with 90% reduction in NOx and 50% in PM with limit on particulate number. Also moving to Trem-IV and Trem-V for off-road applications subsequently. It needs higher efficiency after-treatment systems like SCR and DPF to achieve such lower emission levels. Addition of these complex after-treatment system, severely increase the cost of diesel power plant with heavy penalty on fuel economy. Hence, it is challenge to auto industry to reduce the complexity and cost, so that it requires an alternate solution to reduce NOx and PM emissions at source to reduce cost and system complexity. Low Temperature Combustion (LTC) is a potential concept to reduce the NOx and PM emissions simultaneously. LTC concept was experimentally demonstrated on engines of passenger car and light commercial segments, but not much work carried out for heavy duty engines.</div><div class="htmlview paragraph">The current research work focused on development of LTC concept to reduce both NOx and PM emissions to a required low levels with fuel efficiency improvement so that aftertreatment system cost and complexity will be reduced to a great extent for BS-VI norms. Extensive simulation work carried out in this research for selecting the combustion system including fuel injection system (nozzle configuration, injection pressures and multiple injection), air handling system (air-fuel ratio, EGR%, and swirl) and piston bowl (combustion bowl geometry, compression ratio) suitable to run the engine on both LTC and conventional modes. Engine was built with all modified features and experiments were performed as per BS-VI cycles (WHSC and WHTC).</div><div class="htmlview paragraph">Experiments carried out over entire engine operating zone with smooth transition between LTC modes in part loads and conventional combustion mode in high load zone. Cycle engine out emissions reduced up to 2.1 g/kWh NOx and ~0.03 g/kWh PM with ~5% overall cycle BSFC improvement in steady state WHSC cycle. Encouraging results have been achieved on transient WHTC cycle also. The lowest BSFC noticed during experiments was close to 191 g/kWh at optimized engine out NOx levels. Utmost important is reduced engine out emissions and improved fuel economy which reduces after-treatment system cost &amp; complexity, operating, maintenance cost and improved field performance with increased regeneration intervals. This result in lower urea and fuel consumption. In summary, LTC is a cost effective solution for BS-VI.</div></div>

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