Expansion of external EGR effective region and influence of dilution on boosted operation of a downsized turbocharged GDI engine

Proceedings of the Institution of Mechanical Engineers, Part D:

et al. 2021

The combination of a growing number of complex technologies in internal combustion engines (ICE) is commonplace, due to the need of complying with the tight pollutant regulations and achieving high efficiencies. Hence the work of calibration engineers is led by a constant increase in degrees of freedom in ICE design. In this research work, a wide analysis on the optimization of combined variable valve timing (VVT) and exhaust gases recirculation (EGR) strategies is developed, in order to reduce fuel consumption in a EURO 6 1.3l 4-stroke 4-cylinder, gasoline, turbocharged, direct-injection engine, also equipped with a variable nozzle turbine (VNT). For that purpose, a methodology which combines 1D engine simulations with limited experimental work was applied. First, the data from 25 experimental tests distributed into three steady engine operating conditions was used to calibrate a 1D model. Then, modeling parametric studies were performed to optimize VVT and EGR parameters. A total of 150 cases were simulated for each operating point, in which VVT settings and EGR rate were varied at iso-air mass flow and iso-intake manifold temperature. The optimization was based on finding the configuration of VVT and EGR systems which maximizes the indicated efficiency. All different cases modeled were also evaluated in terms of pumping and heat losses. Moreover, a deep assessment of instantaneous pressure traces and mass flows in intake and exhaust valves was given, to provide insights about the optimization procedure. Finally, the findings obtained by simulation were compared with the results from a design of experiments (DOE) composed of more than 300 tests, and the impact on engine fuel consumption was analyzed.

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Section: Methodsmentioning

confidence: 99%

Experimental and modeling analysis on the optimization of combined VVT and EGR strategies in turbocharged direct-injection gasoline engines with VNT

Proceedings of the Institution of Mechanical Engineers, Part D:

et al. 2021

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“…12,13 On this matter, advanced ignition systems have been developed in the last years, to extend the EGR tolerance in SI engines. Shimura et al 14 and Pilla and Francqueville 15 reported that EGR rate could be increased up to 27% and 31%, at high and low load conditions respectively, by means of high-energy dual-coil ignition systems, thus decreasing fuel consumption.…”

Section: Introductionmentioning

confidence: 99%

Assessment of air-management strategies to improve the transient performance of a gasoline engine under high EGR conditions during load-decrease operation

International Journal of Engine Research

et al. 2021

Advanced gasoline engines in hybrid powertrains are currently regarded as the most widespread solution for passenger cars in the upcoming years, due to the strong commitment of many countries to reduce greenhouse gas emissions and the limitations of pure electric vehicles at present. At the same time, it is widely proven that exhaust gas recirculation (EGR) through the low pressure (LP) configuration allows reducing fuel consumption and, consequently, CO2 emissions in gasoline engines. However, it is challenging to extract the full EGR potential, since it means operating close to the EGR tolerance, and this can compromise the engine transient response because of the long transport delays associated with LP EGR systems. Hence the paper presents an analysis on the capability of three strategies to accelerate the transient response of a gasoline engine operating with high LP EGR levels during tip-out maneuvers, while guaranteeing the combustion stability. Such strategies are the optimization of valve synchronization (based on applying different delays between the throttle actuation and pedal demand), the integration of a secondary air-path which bypasses the compressor, and the use of a pressurized air tank directly connected to the intake manifold. Both experimental and modeling data were utilized to assess the advantages and drawbacks of these strategies: engine tests for the validation of 1D model transient performance and the evaluation of combustion stability and torque evolution, while the fluid-dynamics and transport phenomena were analyzed by simulation.

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Assessment of air management strategies to improve the transient response of advanced gasoline engines operating under high EGR conditions

et al. 2023

Energy