Abstract
This work presents a numerical study that investigates the optimum post-injection strategy and internal exhaust gas recirculation (iEGR) application with intake valve re-opening (2IVO) aiming to optimize the brake specific nitric oxide (bsNO) and brake specific soot (bsSoot) trade-off with reasonable brake specific fuel consumption (BSFC) via 1D engine cycle simulation. For model validation, single and post-injection test results obtained from a heavy-duty single cylinder diesel research engine were used. Then, the model was modified for 2IVO application. Following the simulations performed based on Latin hypercube DoE; BSFC, bsNO and bsSoot response surfaces trained by feedforward neural network were generated as a function of the injection (start of main injection, post-injection quantity, post-injection dwell time) and iEGR (2IVO dwell) parameters. After examining the effect of each parameter on pollutant emission and engine performance, multi-objective pareto optimization was performed to obtain pareto optimum solutions in the BSFC-bsNO-bsSoot space for 8.47 bar brake mean effective pressure (BMEP) load and 1500 rpm speed condition. The results show that iEGR and post-injection can significantly reduce NO and soot emissions, respectively. The soot oxidation capability of post-injection comes out only if it is not too close to the main injection and its efficiency and effective timing are substantially affected by iEGR rate and main injection timing. It could also be inferred that by the combination of iEGR and post-injection, NO and soot could be reduced simultaneously with a reasonable increase in BSFC if start of main injection is phased properly.
Highlights
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.license.Due to the strict pollutant emission regulations, diesel engine development studies can be carried out limitedly because of the trade-off relationships between the soot and NOx emissions which are the inevitable results of the compression-ignition combustion mechanism [1,2]
In-cylinder NOx formation is usually controlled by external exhaust gas recirculation, which is a well-known method and is applied by redirecting cooled exhaust gases to the intake manifold [4]. eEGR is effective in lowering the maximum temperature of the burned gases, which is the source of thermal NOx formation, as it leads to increased thermal capacity, decreased oxygen concentration and dilution of in-cylinder charge [5]
AsModel it canValidation be seen from Figure 7, the in-cylinder pressure (ICP), in-cylinder temperaAs it canheat be seen from Figure
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.license (https://creativecommons.org/licenses/by/4.0/).Due to the strict pollutant emission regulations, diesel engine development studies can be carried out limitedly because of the trade-off relationships between the soot and NOx emissions which are the inevitable results of the compression-ignition combustion mechanism [1,2]. Studies have been carried out on in-cylinder emission reduction techniques that have the potential to reduce the burden, size and costs of aftertreatment systems [3]. EEGR is effective in lowering the maximum temperature of the burned gases, which is the source of thermal NOx formation, as it leads to increased thermal capacity, decreased oxygen concentration and dilution of in-cylinder charge [5]. Another way to dilute in-cylinder charge and reduce NOx emission by lowering
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