Combined Miller/Atkinson Strategy for Future Downsizing Concepts

Scheidt, Martin; Brands, Christoph; Kratzsch, Matthias; Günther, Michael

doi:10.1007/s38313-014-0144-6

Cited by 19 publications

(19 citation statements)

References 2 publications

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“…To model turbulence, it was used the Re-Normalization Group (RNG) k- model by Yakhot et. al [7], which is a variation of the k- model where it was added two transport equations, one for turbulent dissipation and one for turbulent kinetic energy.…”

Section: Numerical Methodologymentioning

confidence: 99%

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In-Cylinder Gas Exchange Control Process for Maximizing Fuel Conversion Efficiency

Radicchi¹,

Silva²,

Baêta³

et al. 2017

Blucher Engineering Proceedings

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The use of exhaust gas recirculation in internal combustion engines, obtained by means of variable valve timing techniques, has represented a good alternative to reduce in-cylinder gas emission and the specific fuel consumption, consequently improving thermal efficiency. The control of valves opening and closing times, especially when keeping some overlapping, may permit the residual gases trapping, what makes the cylinder temperatures lower and reduce engine-out emissions, mainly of nitrogen oxides. Besides that, these techniques allow load control, what can eliminate the necessity of throttling and hence pumping losses. Based on this, this paper presents an analysis of the use of variable valve timing focused on trapping some residual gases in a spark ignition engine. It has been used a four valve Single Cylinder Research Engine-SCRE with direct injection. It was adopted a volumetric ratio equal to 15:1, an engine speed of 2500 rpm and the ethanol as fuel. Valves timing were changed taking into account the maximum fraction of exhaust gases which could be used without compromising mixture inflammability. Changes in performance were analyzed and the importance of controlling the amount of recycled exhaust gases was finally evidenced.

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Section: Numerical Methodologymentioning

confidence: 99%

“…[5] Although the EIVC and LIVC methods are known to reduce pumping work and improve fuel consumption, it is shown that each strategy can cause heat losses [6]. However, the LIVC when compared to EIVC reduces the turbulence conversion into heat and presents less disadvantages due to turbulence at ignition timing [7].…”

Section: Introductionmentioning

confidence: 99%

In-Cylinder Gas Exchange Control Process for Maximizing Fuel Conversion Efficiency

Radicchi¹,

Silva²,

Baêta³

et al. 2017

Blucher Engineering Proceedings

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“…Miller cycle engines use Late-Intake-Valve-Closing (LIVC) or Early-Intake-Valve-Closing (EIVC) to reduce effective compression in order to enable a higher geometric compression ratio (CR) or expansion ratio (ER), which has shown to effectively improve engine thermal efficiency while controlling knock and abnormal combustions on downsized boosted spark-ignition (SI) engines. 2–12…”

Section: Introductionmentioning

confidence: 99%

Development of an aggressive Miller Cycle engine with extended Late-Intake-Valve-Closing and a two-stage turbocharger

Liu

Sun

Zhu

2017

Proceedings of the Institution of Mechanical Engineers, Part D:

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This paper describes the development of an aggressive Miller cycle gasoline engine with stoichiometric combustion, a high expansion ratio of 12.5:1, a 65 crank angle degrees (CAD) longer duration Late-Intake-Valve-Closing (LIVC) cam, and a two-stage turbocharger. The full-load performance and part-load fuel consumption of the baseline and Miller cycle engines were assessed through engine dynamometer testing. The aggressive Miller cycle engine achieved the maximum Brake Mean Effective Pressure (BMEP) of 22 bar at 1500 rpm, which was enabled by the 65 CAD longer duration LIVC cam to further reduce the effective compression for controlling knock and by the two-stage turbocharger to provide significantly higher boost for maintaining and increasing trapped mass. It was shown that the more aggressive Millerization was realized while maintaining the specific output and advantages of current downsized boosted engines, such as lower friction and lower pumping losses. The aggressive Miller cycle engine achieved above 6% brake-specific fuel consumption (BSFC) reduction over the baseline turbocharged spark-ignition engine on average. The 65 CAD longer duration LIVC cam provided the benefit of pumping loss reduction with delayed intake valve closing and the benefit of hot residual dilution with relatively advanced intake cam phasing simultaneously, which provided the significant fuel economy improvement at non-knocking light-load conditions. Even without the latest technology enhancements and friction reduction methods on its base engine hardware, the aggressive Miller cycle engine achieved a very broad BSFC island of 230 g/kWh or lower, with the lowest BSFC of 223 g/kWh at 2000 rpm and 10 bar BMEP.

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“…5 On the other hand, the Miller cycle gasoline engine uses late intake valve closing (LIVC) or early intake valve closing to reduce the effective compression; this enables the geometric CR to increase, which improves the thermal efficiency of the engine while controlling knock and abnormal combustion in downsized-boosted gasoline engines. [4][5][6][7][8][9][10][11][12][13] In this study, a 2.2 l four-cylinder Miller cycle engine with a geometric CR from 11.5:1 to 12.5:1, a LIVC cam with an opening duration 40°crank angle (CA) longer than the baseline and a single-stage twin-scroll turbocharger was developed. To improve the fuel economy further at part load, external cooled EGR was considered and implemented on the Miller cycle engine.…”

Section: Introductionmentioning

confidence: 99%

“…On the other hand, the Miller cycle gasoline engine uses late intake valve closing (LIVC) or early intake valve closing to reduce the effective compression; this enables the geometric CR to increase, which improves the thermal efficiency of the engine while controlling knock and abnormal combustion in downsized-boosted gasoline engines. 4–13…”

Section: Introductionmentioning

confidence: 99%

Development of a Miller cycle engine with single-stage boosting and cooled external exhaust gas recirculation

Liu

Zhu

Sun

2016

Proceedings of the Institution of Mechanical Engineers, Part D:

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In this paper, the development of a Miller cycle gasoline engine which has a high compression ratio from 11.5:1 to 12.5:1, single-stage turbocharging and external cooled exhaust gas recirculation is described. The improvement in the fuel economy by adding external cooled exhaust gas recirculation to the Miller cycle engine at different geometric compression ratios were experimentally evaluated in part-load operating conditions. The potential of adding external cooled exhaust gas recirculation in full-load conditions to mitigate pre-ignition in order to allow higher geometric compression ratios to be utilized was also assessed. An average of 3.2% additional improvement in the fuel economy was achieved by adding external cooled exhaust gas recirculation to the Miller cycle engine at a geometric compression ratio of 11.5:1. It was also demonstrated that the fuel consumption of the engine with external cooled exhaust gas recirculation was reduced by 3-7% in a wide range of part-load operating conditions and that the engine output of the Miller cycle engine at a geometric compression ratio of 12.5:1 increased at 2000 r/min in the full-load condition. The Miller cycle engine with external cooled exhaust gas recirculation at a geometric compression ratio of 12.5:1 achieved a broad brake specific fuel consumption range of 220 g/kW h or lower, with the lowest brake specific fuel consumption of 215 g/kW h. While there are still challenges in implementing external cooled exhaust gas recirculation, the Miller cycle engine with single-stage turbocharging and external cooled exhaust gas recirculation showed its potential for substantial improvement in the fuel economy as one of the technical pathways to meet future requirements in reducing carbon dioxide emissions.

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Combined Miller/Atkinson Strategy for Future Downsizing Concepts

Cited by 19 publications

References 2 publications

In-Cylinder Gas Exchange Control Process for Maximizing Fuel Conversion Efficiency

In-Cylinder Gas Exchange Control Process for Maximizing Fuel Conversion Efficiency

Development of an aggressive Miller Cycle engine with extended Late-Intake-Valve-Closing and a two-stage turbocharger

Development of a Miller cycle engine with single-stage boosting and cooled external exhaust gas recirculation

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