Techniques for CO<sub>2</sub> Emission Reduction over a WLTC. A Numerical Comparison of Increased Compression Ratio, Cooled EGR and Water Injection

Bozza, Fabio; Bellis, Vincenzo De; Teodosio, Luigi; Tufano, Daniela; Malfi, Enrica

doi:10.4271/2018-37-0008

Cited by 22 publications

(11 citation statements)

References 44 publications

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“…This means that the maps in Figure 3a,b are also representative of efficiency with a negative torque, and the maximum absorbed torque is equal to the maximum delivered torque. Aiming at testing the robustness of the proposed control strategy, as said, some analyses are performed with a more conventional turbocharged downsized stoichiometric engine, labeled as engine 2 [24], whose BSFC map is shown in Figure 4. These maps, depicted in Figure 3a,b, are representative of typical synchronous electric motors under 400 V. The efficiency maps and the maximum torque are modeled assuming a perfect symmetry of the performance for motor/brake operations.…”

Section: Hev Architecturementioning

confidence: 99%

Development of an Efficient Thermal Electric Skipping Strategy for the Management of a Series/Parallel Hybrid Powertrain

2021

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In recent years, the development of hybrid powertrain allowed to substantially reduce the CO2 and pollutant emissions of vehicles. The optimal management of such power units represents a challenging task since more degrees of freedom are available compared to a conventional pure-thermal engine powertrain. The a priori knowledge of the driving mission allows identifying the actual optimal control strategy at the expense of a quite relevant computational effort. This is realized by the off-line optimization strategies, such as Pontryagin minimum principle—PMP—or dynamic programming. On the other hand, for an on-vehicle application, the driving mission is unknown, and a certain performance degradation must be expected, depending on the degree of simplification and the computational burden of the adopted control strategy. This work is focused on the development of a simplified control strategy, labeled as efficient thermal electric skipping strategy—ETESS, which presents performance similar to off-line strategies, but with a much-reduced computational effort. This is based on the alternative vehicle driving by either thermal engine or electric unit (no power-split between the power units). The ETESS is tested in a “backward-facing” vehicle simulator referring to a segment C car, fitted with a hybrid series-parallel powertrain. The reliability of the method is verified along different driving cycles, sizing, and efficiency of the power unit components and assessed with conventional control strategies. The outcomes put into evidence that ETESS gives fuel consumption close to PMP strategy, with the advantage of a drastically reduced computational time. The ETESS is extended to an online implementation by introducing an adaptative factor, resulting in performance similar to the well-assessed equivalent consumption minimization strategy, preserving the computational effort.

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Section: Hev Architecturementioning

confidence: 99%

Development of an Efficient Thermal Electric Skipping Strategy for the Management of a Series/Parallel Hybrid Powertrain

2021

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“…The results show a reduction of brake-specific fuel consumption for various operating conditions considering given constraints for the TIT, boost pressure and peak cylinder pressure (PCP). The same model was applied by Bozza et al 15 to analyze the combination of different technologies to reduce fuel consumption for Worldwide harmonized Light vehicles Test Cycle (WLTC) conditions. The authors stated that LP-EGR is beneficial for low-speed and low-load operating conditions, while water injection improves fuel consumption at high-speed and high-load operating conditions, enabling stoichiometric air–fuel ratios (AFRs).…”

Section: Introductionmentioning

confidence: 99%

Gasoline engine performance simulation of water injection and low-pressure exhaust gas recirculation using tabulated chemistry

Franken

Mauß

Seidel³

et al. 2020

International Journal of Engine Research

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This work presents the assessment of direct water injection in spark-ignition engines using single cylinder experiments and tabulated chemistry-based simulations. In addition, direct water injection is compared with cooled low-pressure exhaust gas recirculation at full load operation. The analysis of the two knock suppressing and exhaust gas cooling methods is performed using the quasi-dimensional stochastic reactor model with a novel dual fuel tabulated chemistry model. To evaluate the characteristics of the autoignition in the end gas, the detonation diagram developed by Bradley and co-workers is applied. The single cylinder experiments with direct water injection outline the decreasing carbon monoxide emissions with increasing water content, while the nitrogen oxide emissions indicate only a minor decrease. The simulation results show that the engine can be operated at λ = 1 at full load using water–fuel ratios of up to 60% or cooled low-pressure exhaust gas recirculation rates of up to 30%. Both technologies enable the reduction of the knock probability and the decrease in the catalyst inlet temperature to protect the aftertreatment system components. The strongest exhaust temperature reduction is found with cooled low-pressure exhaust gas recirculation. With stoichiometric air–fuel ratio and water injection, the indicated efficiency is improved to 40% and the carbon monoxide emissions are reduced. The nitrogen oxide concentrations are increased compared to the fuel-rich base operating conditions and the nitrogen oxide emissions decrease with higher water content. With stoichiometric air–fuel ratio and exhaust gas recirculation, the indicated efficiency is improved to 43% and the carbon monoxide emissions are decreased. Increasing the exhaust gas recirculation rate to 30% drops the nitrogen oxide emissions below the concentrations of the fuel-rich base operating conditions.

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“…Among the various pathways to improve the thermal efficiency of ICEs, various knock mitigation measures were attempted, such as the variable compression ratio [7], the cooled exhaust gas recirculation (EGR) [8], and the water injection [9]. Benefits of fuel consumption highly depend on the considered operating condition [10]. An increasing research work is nowadays devoted to ultra-lean combustion systems since they have the potential of simultaneously reducing the cylinder-out NOx emissions and the fuel consumption in the whole engine operating domain.…”

Section: Introductionmentioning

confidence: 99%

Optimal Calibration Strategy of a Hybrid Electric Vehicle Equipped with an Ultra-Lean Pre-Chamber SI Engine for the Minimization of CO2 and Pollutant Emissions

et al. 2020

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The complexity of modern hybrid powertrains poses new challenges for the optimal control concerning, on one hand, the thermal engine to maximize its efficiency, and, on the other hand, the vehicle to minimize the noxious emissions and CO2. In this context, the engine calibration has to be conducted by considering simultaneously the powertrain management, the vehicle characteristics, and the driving mission. In this work, a calibration methodology for a two-stage boosted ultra-lean pre-chamber spark ignition (SI) engine is proposed, aiming at minimizing its CO2 and pollutant emissions. The engine features a flexible variable valve timing (VVT) control of the valves and an E-compressor, coupled in series to a turbocharger, to guarantee an adequate boost level needed for ultra-lean operation. The engine is simulated in a refined 1D model. A simplified methodology, based on a network of proportional integral derivative (PID) controllers, is presented for the calibration over the whole operating domain. Two calibration variants are proposed and compared, characterized by different fuel and electric consumptions: the first one aims to exclusively maximize the brake thermal efficiency, and the second one additionally considers the electric energy absorbed by the E-compressor and drained from the battery. After a verification against the outcomes of an automatic optimizer, the calibration strategies are assessed based on pollutant and CO2 emissions along representative driving cycles by vehicle simulations. The results highlight slightly lower CO2 emissions with the calibration approach that minimizes the E-compressor consumption, thus revealing the importance of considering the engine calibration phase, the powertrain management, the vehicle characteristics, and its mission.

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Techniques for CO₂ Emission Reduction over a WLTC. A Numerical Comparison of Increased Compression Ratio, Cooled EGR and Water Injection

Cited by 22 publications

References 44 publications

Development of an Efficient Thermal Electric Skipping Strategy for the Management of a Series/Parallel Hybrid Powertrain

Development of an Efficient Thermal Electric Skipping Strategy for the Management of a Series/Parallel Hybrid Powertrain

Gasoline engine performance simulation of water injection and low-pressure exhaust gas recirculation using tabulated chemistry

Optimal Calibration Strategy of a Hybrid Electric Vehicle Equipped with an Ultra-Lean Pre-Chamber SI Engine for the Minimization of CO2 and Pollutant Emissions

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Techniques for CO2 Emission Reduction over a WLTC. A Numerical Comparison of Increased Compression Ratio, Cooled EGR and Water Injection

Cited by 22 publications

References 44 publications

Development of an Efficient Thermal Electric Skipping Strategy for the Management of a Series/Parallel Hybrid Powertrain

Development of an Efficient Thermal Electric Skipping Strategy for the Management of a Series/Parallel Hybrid Powertrain

Gasoline engine performance simulation of water injection and low-pressure exhaust gas recirculation using tabulated chemistry

Optimal Calibration Strategy of a Hybrid Electric Vehicle Equipped with an Ultra-Lean Pre-Chamber SI Engine for the Minimization of CO2 and Pollutant Emissions

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Techniques for CO₂ Emission Reduction over a WLTC. A Numerical Comparison of Increased Compression Ratio, Cooled EGR and Water Injection