Technologies for CO2 Reductions in ICEs

Nowadays the fast development of the internal combustion engine technologies together with the day by day more stringent issues raised by the environmental concerns, there is a strong demand for an improvement in combustion efficiency as well as in terms of pollutant emissions to the environment. Alternative fuels such as natural gas has been taken into account and applied on the commercial vehicles. Natural gas is primarily composed of methane and has several alternative features such as a high number of hydrogen to carbon ratio and high research octane number, which means it is possible to give higher boost to the fuel air mixture with less risk to have knock phenomenon. On the other hand, variable valve actuation (VVA) has been proved to be an effective way to increase engine efficiency by decreasing pumping losses at partial load conditions. In this context, research work has been proceed with CORE (CO2 reduction for long distance transport) project, which is a collaborative large-scale integrating project for a call within FP7-SUSTAINABLE SURFACE TRANSPORT of the EC. The project consortium consists of three truck manufactures in Europe: Volvo, Daimler and IVECO, together with 13 other partners in the automotive industry and universities and it aims to demonstrate a substantial reduction of CO2 emissions, 15\% improved fuel efficiency compared to a EURO V engine and fulfilling EURO VI emission legislation at the same time. The project is inserted in a series of research projects, which have been performed by the EC with the aim of boosting the cooperation among car manufactures, suppliers and technical universities as well as of defining enhanced and feasible solutions for the market. During this thesis research work within the CORE Project, a heavy duty engine fuelled with compressed natural gas (CNG) using VVA technology has been numerically modelled using 0/1D commercial tool GT Power. Since with VVA technology, it results lower exhaust temperatures which is not favoured by considering the aftertreatment working conditions. The advanced combustion management, thus the retarding combustion strategy combined with different valve profiles, has been numerically simulated in order to reach a good condition for aftertreatment working conditions both at steady state and transient conditions. Retarding combustion strategies have been numerically tested in order to increase the turbine outlet temperature by limiting the fuel consumption increment. At the same time, the upper limit of the turbine inlet temperature has also been taken into account. In order to obtain more opportunities to increase the model accuracy and to extend its applicability, based on the engine model built with GT Power, a user defined combustion based on fractal approach has been embedded. This user defined combustion is composed of several submodels (flow submodel, CAD submodel, flame submodel, combustion submodel...etc). The validation of these submodels' coupling is done by comparing simulated and experimental data over a complete engine operating map after the calibration work. The model has shown its ability to reproduce the experimental data under the same working conditions with very high accuracy. Thus with this embedded combustion approach, it makes the model from a non-predictive one to a predictive one. Several applications have been numerically proceeded with this new model under transient condition tests with advanced combustion management and it demonstrates its good applicability and accuracy. Then this newly developed user combustion approach has been applied on the other two light duty engines: 1.4l T-jet PFI natural gas engine and 1.4l T DI natural gas engine. The engine models built in GT power have been carefully calibrated and they are able to reproduce the experimental data under the same working conditions with very high accuracy. A new application has been tested based on the engine models in which it is able to produce a spark advance value by targeting a proper MFB50 value. The models are able to give comparable spark advance results once the users target the experimental MFB50 values. This again further proves the robustness of the predictive model the developed user combustion approach. Meanwhile doing the predictive modelling for both engines, the flow submodel of the user combustion approach has also been improved with a available set of flow data obtained from 3D CFD simulations.The simulated turbulence intensity over the engine revolution has reached a comparable level of the results coming from 3D CFD data. The outcome of the work during the Ph.D study has been published in the following list. 1. Mirko Baratta, Roberto Finesso, Daniela Misul, Ezio Spessa, Yifei Tong, and Cesare Peletto. Potential of the variable valve actuation (VVA) strategy on a heavy duty cng engine. In ASME 2014 12th Biennial Conference on Engineering Systems Design and Analysis, American Society of Mechanical Engineers, 2014. 2. Mirko Baratta, Roberto Finesso, Daniela Misul, Ezio Spessa, Yifei Tong, and Cesare Peletto. Optimization of a user-defined fractal combustion model and its application to the assessment of the behavior of a heavy-duty NG engine equipped with VVA under steady-state and transient conditions. Int J of Mech and Control vol. 18 no.1 (2017)