Exhaust Gas Recirculation in Diesel Engine Systems
Summary
Exhaust Gas Recirculation (EGR) is a cornerstone technology in modern diesel engines aimed at reducing nitrogen oxide (NOx) emissions by redirecting a portion of exhaust gases back into the intake stream. By diluting the intake charge, EGR lowers peak combustion temperatures and inhibits NOx formation. Contemporary systems deploy both high-pressure (HP) and low-pressure (LP) EGR loops, often in combination, to optimise performance across varying engine loads and speeds. Integration with turbocharging—frequently via variable geometry turbochargers (VGT)—and intercoolers enhances charge density and thermal management but introduces challenges such as condensation in heat-exchange components and soot formation. System controls balance trade-offs between NOx reduction, particulate emissions, fuel consumption and transient responsiveness, while sensor-based and model-based estimation techniques underpin closed-loop regulation. Applications extend from heavy-duty road engines to marine propulsion, responding to ever-tighter global emissions regulations and driving research into advanced control algorithms, novel sensor architectures and predictive thermal models.
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Exhaust Gas Recirculation in Diesel Engine Systems publication trend
The graph below shows the total number of articles in exhaust gas recirculation in diesel engine systems across all publications each year (not limited to Nature Index journals).
Technical terms
Exhaust Gas Recirculation (EGR): A mechanism that recirculates a portion of exhaust gases to the intake manifold to reduce combustion temperatures and NOx formation.
High-pressure EGR (HP-EGR): An EGR loop that taps exhaust gases upstream of the turbocharger turbine, delivering higher-temperature recirculated gas.
Low-pressure EGR (LP-EGR): An EGR loop that extracts exhaust downstream of the exhaust aftertreatment, returning cooled gas to the compressor inlet.
Variable Geometry Turbocharger (VGT): A turbocharger whose turbine geometry can be adjusted to optimise boost pressure and transient response across engine operating conditions.
Intercooler: A heat exchanger that cools compressed intake air (or recirculated exhaust) to increase density and reduce combustion temperatures.
Nitrogen Oxides (NOx): A collective term for nitrogen monoxide (NO) and nitrogen dioxide (NO2), pollutants formed at high combustion temperatures that contribute to smog and acid rain.
References
- Prediction of Condensation in the Heat Exchangers of Engine Intake Systems according to External Environmental and Operating Conditions. International Journal of Energy Research (2023).
- Verification and Comparison of Nine Exhaust Gas Recirculation Mass Flow Rate Estimation Methods. Sensors (2020).
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