Experimental Investigation on Early and Late Intake Valve Closures for Knock Mitigation through Miller Cycle in a Downsized Turbocharged Engine

Luisi, Sabino; Doria, Vittorio; Stroppiana, Andrea; Millo, Federico; Mirzaeian, Mohsen

doi:10.4271/2015-01-0760

Cited by 57 publications

(24 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The main characteristics of the powertrains are highlighted in Table 3 and will be described in the following paragraph. [29]. The valve closure delay of the intake valve was actuated keeping the valve open at the full lift for a specified angle duration and it was defined to maximize the brake torque at full load without exceeding the knock limit and the maximum T3 in the high load region.…”

Section: Analysed Powertrain Configurations and Simulation Matrixmentioning

confidence: 99%

Numerical Investigation of 48 V Electrification Potential in Terms of Fuel Economy and Vehicle Performance for a Lambda-1 Gasoline Passenger Car

et al. 2019

Self Cite

View full text Add to dashboard Cite

Real Driving Emissions (RDE) regulations require the adoption of stoichiometric operation across the entire engine map for downsized turbocharged gasoline engines, which have been so far generally exploiting spark timing retard and mixture enrichment for knock mitigation. However, stoichiometric operation has a detrimental effect on engine and vehicle performances if no countermeasures are taken, such as alternative approaches for knock mitigation, as the exploitation of Miller cycle and/or powertrain electrification to improve vehicle acceleration performance. This research activity aims, therefore, to assess the potential of 48 V electrification and of the adoption of Miller cycle for a downsized and stoichiometric turbocharged gasoline engine. An integrated vehicle and powertrain model was developed for a reference passenger car, equipped with a EU5 gasoline turbocharged engine. Afterwards, two different 48 V electrified powertrain concepts, one featuring a Belt Starter Generator (BSG) mild-hybrid architecture, the other featuring, in addition to the BSG, a Miller cycle engine combined with an e-supercharger were developed and investigated. Vehicle performances were evaluated both in terms of elasticity maneuvers and of CO 2 emissions for type approval and RDE driving cycles. Numerical simulations highlighted potential improvements up to 16% CO 2 reduction on RDE driving cycle of a 48 V electrified vehicle featuring a high efficiency powertrain with respect to a EU5 engine and more than 10% of transient performance improvement.Energies 2019, 12, 2998 2 of 21 gases at a higher level, eliciting a further enrichment of the mixture. What is more, the use of mixture enrichment (i.e., moving from a stoichiometric to rich combustion) while cooling the in-cylinder charge and the exhaust gases, increases the CO emissions during high engine load operation, as highlighted by Clairotte et al. [3]. Moreover, future Regulation may prescribe a conformity factor for CO [4] limiting the exploitation of the fuel enrichment and pushing the development of the gasoline engines towards stoichiometric operation [5,6]. This aim can be achieved with the adoption of different powertrain technologies, like cooled exhaust manifold, high temperature resistant turbine as well as water injection, Miller cycle and advanced turbocharging, as explained by Glahn et al. [6].On the other hand, concerning the greenhouse emissions, the average fleet target value for CO 2 has been set to be 95 g/km from 2021 [7], measured according to the new Worldwide Harmonized Light-Duty Vehicles Test Procedure (WLTP) and correlated to the value of the New European Driving Cycle (NEDC). Moreover, recently the European Parliament and the Council adopted Regulation (EU) 2019/631 [8] setting CO 2 emission performance standards for new passenger cars in the EU for the

show abstract

Section: Analysed Powertrain Configurations and Simulation Matrixmentioning

confidence: 99%

Numerical Investigation of 48 V Electrification Potential in Terms of Fuel Economy and Vehicle Performance for a Lambda-1 Gasoline Passenger Car

et al. 2019

Self Cite

View full text Add to dashboard Cite

show abstract

“…Turbocharging technique, along with downsizing, Variable Valve Actuation systems, and Gasoline Direct Injection are today considered an effective way to reduce CO2 emissions in automotive gasoline engines, especially for the European and US markets [1,2,3]. The successful application of exhaust turbocharging to downsized engines must overcome various difficulties, related both to the specific operating environment (exhaust gas temperature level) and to engine performance, focusing on low-end torque and transient response.…”

Section: Introductionmentioning

confidence: 99%

Direct Evaluation of Turbine Isentropic Efficiency in Turbochargers: CFD Assisted Design of an Innovative Measuring Technique

Marelli¹,

Usai²,

Capobianco³

et al. 2019

SAE Technical Paper Series

View full text Add to dashboard Cite

Turbocharging is playing today a fundamental role not only to improve automotive engine performance, but also to reduce fuel consumption and exhaust emissions for both Spark Ignition and Diesel engines. Dedicated experimental investigations on turbochargers are therefore necessary to assess a better understanding of its performance. The availability of experimental information on turbocharger steady flow performance is an essential requirement to optimize the engine-turbocharger matching, which is usually achieved by means of simulation models. This aspect is even more important when referred to the turbine efficiency, since its swallowing capacity can be accurately evaluated through the measurement of mass flow rate, inlet temperature and pressure ratio across the machine. However, in the case of a turbocharger radial inflow turbine, isentropic efficiency, directly evaluated starting from measurement of thermodynamic parameters at the inlet and outlet sections, can give significant errors. This inaccuracy is mainly related to the difficulty of a correct evaluation of the turbine outlet temperature due to the non-uniform distribution of flow field and temperature at the measuring section. This work is the follow up of a previous publication where an intensive measurement campaign was performed to obtain a reliable measurement of the turbine outlet temperature. To this aim, a handmade 3-hole probe (unlike most of the measuring probes available on the market, which are considered as intrusive) was adopted to perform measurement of the flow field, pressure and temperature downstream the turbine with special reference to different radial and tangential positions in two sections located near and far from the outlet machine, allowing the evaluation of the efficiency through local enthalpy fluxes across the turbine in cold and hot conditions upstream the turbine. The comparison between results obtained through the local measurements and those achieved through a direct measurement of turbine outlet temperature by three probes inserted in pipe with a different protrusion, have highlighted that heat transfer effects across the pipes and across the turbocharger components play an important role on the estimation of temperature profile at the outlet section. In order to put some light on this aspect, CFD simulations have been performed to estimate the impact of the heat transfer and flow distribution on the estimation of the isentropic efficiency. The OpenFOAM ® code has been adopted to simulate the actual turbine geometry resorting to multi reference frame (MRF) strategies, instead of mesh motion strategies, to characterize the flow pattern downstream of the turbine. Moreover, CFD analysis was used to design a specific device, whose goal was the dissipation of flow structures dominated by vorticity, achieving in this way a uniform distribution of the flow and temperature fields at the measuring section. This will result in a much more reliable evaluation of the turbine efficiency

show abstract

“…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:

View full text Add to dashboard Cite

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.

show abstract

Experimental Investigation on Early and Late Intake Valve Closures for Knock Mitigation through Miller Cycle in a Downsized Turbocharged Engine

Cited by 57 publications

References 6 publications

Numerical Investigation of 48 V Electrification Potential in Terms of Fuel Economy and Vehicle Performance for a Lambda-1 Gasoline Passenger Car

Numerical Investigation of 48 V Electrification Potential in Terms of Fuel Economy and Vehicle Performance for a Lambda-1 Gasoline Passenger Car

Direct Evaluation of Turbine Isentropic Efficiency in Turbochargers: CFD Assisted Design of an Innovative Measuring Technique

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

Contact Info

Product

Resources

About