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A computational study to investigate the effects of insulation and EGR in a diesel engine

Author(s): Syed Yousufuddin, K.Venkateswarlu, Naseeb Khan

Journal: International Journal of Energy and Environment
ISSN 2076-2895

Volume: 3;
Issue: 2;
Start page: 247;
Date: 2012;
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Keywords: Adiabatic; Emission; Indirect injection; NOx; Soot

Higher heat losses and brake specific fuel consumption (BSFC) are major problems in an indirect injection (IDI) diesel engine, which can be overcome by means of insulation. However, insulation increases combustion temperature by about 200-2500 compared to an identical standard IDI diesel engine. Consequently, the NOx emission increases extremely due to this temperature increment. With the proper adjustment of cold EGR mass fraction, it is possible to partially offset the adverse effect of insulation on heat release rate and hence to obtain improved performance and lower NOx than the baseline engine. At the first step of this work, the effects of insulation (without heat flux) on the performance and emissions are studied at both part and full loads by a three dimensional model. The results show that in the adiabatic case, BSFC is approximately 18% and 23% lower than baseline at the full and part loads respectively. Also, soot emission shows 36% reduction at full load, while at the part load, the value of which remains unchanged. At the second step of the present work, for reduction of NOx production in the insulated engine, cold exhaust gas recirculation (EGR) method is utilized. Thus, the model is studied at various cold EGR mass fractions, in which the EGR mass fraction increases from 0% to 30% at the same speed and operating loads. The optimum cold EGR mass fraction is obtained as 10% for part load operation. Results show that with adding this optimum EGR, the BSFC and NOx decrease by 15% and 6.5 % respectively at full load compared to the baseline and these reductions are reached to 21% and 29% in the case of part load respectively, while it causes increment in soot emission at full load operation and decreases slightly in the part load compared to the baseline engine. As an engine is generally operated for a short time interval at full load condition, this increment can be omitted when improvements in BSFC and decrease in NOx are considered together. The results of the model for baseline engine are in good agreement with the corresponding experimental data. This agreement makes the model a reliable tool that can be used for exploring new engine concepts.

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