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Automotive Control Systems
Published in William S. Levine, Control System Applications, 2018
J. A. Cook, J. W. Grizzle, J. Sun, M. K. Liubakka, D.S. Rhode, J. R. Winkelman, P. V. Kokotović
Exhaust gas recirculation (EGR) systems were introduced as early as 1973 to control (NOx) emissions. The principle of EGR is to reduce NOx formation during the combustion process by diluting the inducted air-fuel charge with inert exhaust gas. In electronically controlled EGR systems, this is accomplished using a metering orifice in the exhaust manifold to enable a portion of the exhaust gas to Bow from the exhaust manifold through a vacuum-actuated EGR control valve and into the intake manifold. Feedback based on the difference between the desired and measured pressure drop across the metering orifice is employed to duty cycle modulate a vacuum regulator controlling the EGR valve pintle position. Because manifold pressure rate and engine torque are directly influenced by EGR, the dynamics of the system can have a significant effect on engine response and, ultimatdy, vehicle drivability. Such dynamics are dominated by the valve chamber filling response time to changes in the EGR duty cycle command.
The technology of bus and coach systems
Published in Peter White, Public Transport, 2017
Very substantial benefits have also been obtained by the general adoption of ultra-low sulphur fuel (ULSD), and by retrofitting older engines with particulate traps. Under EU Directive 98/79 standard diesel has in any case been subject to lower sulphur content – from 500 mg/kg to 350 from January 2000, and 60 since 2005. To meet the standards of Euro 4 onward for NOx, two alternative approaches have been offered by manufacturers – Selective Catalytic Reduction (SCR), using a urea-based additive at the exhaust stage; and Exhaust Gas Recirculation (EGR), the former being more widely adopted.
Internal Combustion Engines
Published in Mehrdad Ehsani, Yimin Gao, Ali Emadi, and Fuel Cell Vehicles, 2017
Mehrdad Ehsani, Yimin Gao, Ali Emadi
Exhaust gas recirculation (EGR) consists in readmitting some of the exhaust gases into the combustion chamber in order to reduce the effective displacement of the engine. This technique is used in conventional vehicles to decrease the fuel consumption at partial torque output, while preserving the acceleration capabilities of the engine. The greatest benefit of EGR is in emission reduction because it reduces the amount of fuel burned in the chamber and therefore the temperature of the exhaust gases. The nitric oxide emissions are greatly reduced.
Experimental analysis of diesel engine behaviours using biodiesel with different exhaust gas recirculation rates
Published in International Journal of Ambient Energy, 2022
S. Prakash, M. Prabhahar, M. Saravana Kumar
Figure 11 depicts the smoke opacity with load for diesel and PME20 with and without EGR. It is noticed that a higher amount of smoke is observed in the exhaust when the engine is operated with EGR compared to without EGR using PME20. The smoke opacity increases with the application of different EGR rates for POME20 at full load. This is due to the incomplete combustion of biodiesel blend with the dilution of the air fuel mixture by the exhaust gases and there by increases the formation of smoke emission. EGR reduces the availability of oxygen for combustion of fuel, which results in relatively incomplete combustion and increased formation of smoke opacity and reduces NOx emissions in engines. The smoke emissions obtained for POME20 with 10%, 20% and 30% EGR are 67%, 74.8% and 82.8%, respectively, whereas for diesel and PME20 are 64.9% and 57.4%, respectively, at full load. PME20 showed 5.5% higher smoke opacity compared to diesel oil at full load operation due to the higher viscosity of PME20 without EGR operation resulting in incomplete combustion of the biodiesel. Similar trends of results were obtained by researchers (Saravanan and Lakshmi Narayana Rao 2014).
Effects of exhaust gas recirculation on the particulates structure characteristics of diesel engine fueled with diesel/biodiesel blend
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2021
Li Ruina, Wang Zhong, Ni Peiyong, Jiang Haobin
Table 5 shows that when the EGR was not used, Tig of particulates was the highest compared with the particulates used the EGR, which was 770.3 and 775.5 K, respectively. It indicated that the particulate oxidation was more difficult when EGR was not used. With the increase of the EGR rate, Tig of the particulates was reduced. Tig of particulates for B100 was reduced by about 19.0 and 42.7 K, and Tig of particulates for B0 was reduced by about 14.4 and 35.5 K compared with when the EGR rate was 15% and 30%. It indicated that Tig of particulates was reduced and the particulate oxidation was easier, and the regeneration temperature of DPF can be effectively reduced. Tig for B100 was lower than that of B0 and B50. When the EGR rate was 0%, 15% and 30%, Tig of particulates for B100 was reduced by about 5.2, 9.8, and 12.4 K compared to B0, respectively. It was shown that EGR was a benefit for reducing the combustion temperature of diesel engine particulates and make the combustion of the diesel engine particulates easier.
Parametric investigation of particulate matter emissions in a gasoline direct injection engine using computational fluid dynamics modelling
Published in Australian Journal of Mechanical Engineering, 2022
Jing Yang Tan, Fabrizio Bonatesta, Hoon Kiat Ng, Suyin Gan
EGR is defined as the percentage of mass flow rate of recirculated exhaust gas to the total mass flow rate of fresh air and recirculated exhaust gas. By recycling a fraction of exhaust gas back to the intake system where it mixes with fresh air before entering the combustion chamber, EGR acts as a diluent in the unburned gas mixture and lowers the peak combustion temperature in the cylinder (Heywood 1988). To examine the effect of EGR on PM emissions, it is hence applied at two different rates of 5% and 10% to the current GDI engine as tabulated in Table 3 without altering the operating parameters of the reference case.