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The use of green hydrogen as a fuel for internal combustion engines is a cleaner alternative to conventional fuels for the automotive industry. Hydrogen combustion produces only water vapor and nitrogen oxides, which can be avoided with ultra-lean operation, thus, eliminating carbon emissions, from a tank-to-wheel perspective. In this context, the aim of this study is to investigate the influence of hydrogen injection timing and duration on the homogeneity of the hydrogen-air mixtures. Computational fluid dynamic (CFD) simulations were performed to analyze the distribution of air-fuel ratios along the engine's combustion chamber. The simulation software was CONVERGE 3.0, which offers the advantage of automatic mesh generation, reducing the modeling efforts to adjusting the operating conditions of the studied case. Before comparing the injection parameters, a mesh independence test was conducted along with model validation using experimental data.

The development and improvement of efficient compressed natural gas (CNG) engines align with efforts to reduce greenhouse gas and pollutant emissions. The objective of this study is to evaluate the flame structure and compare the performance characteristics of an engine powered by compressed natural gas (CNG) under stoichiometric and lean combustion in wide open throttle. CFD simulation alongside experimental tests are performed. The experimental data were obtained using a Hyundai 2.5-liter HR engine, originally a Diesel engine, adapted for spark ignition operation. Lean and stoichiometric conditions were evaluated at compression ratio 14:1, operating at 1800 rpm in MBT spark timing. The results showed that increasing lambda (λ) had a significant effect on apparent heat release rate, laminar flame speed, flame thickness and flame surface area.

In order to further explore the potential of hydrogen as an alternative fuel, this study aims to validate a computational fluid dynamics model for hydrogen combustion in a port fuel injection spark ignition engine. The engine operates at 1800 rpm with a compression ratio of 10:1, under two lean combustion conditions: excess air ratios of 2.5 and 1.7, at full and part load, respectively. The simulations were performed using the CONVERGE 3.1 software and the C3MechV3.3 reaction mechanism. The predictions were then compared with experimental data to assess the accuracy and validity of the model, enabling the comparison of different lean operating conditions to evaluate important combustion characteristics, such as flame development, apparent heat release and NOx formation. The tested model successfully validated the two experimental conditions, accurately adjusting the in-cylinder pressure profiles for both cases of lean hydrogen mixture combustion.

The increasingly strict environmental legislations require the use of strategies and technologies to achieve higher efficiencies in internal combustion engines (ICE). In Brazil, governmental programs as Rota 2030 stimulate the development of technologies to improve engine efficiency and therefore promote fleet decarbonization. Due to lower carbon footprint, the use of renewable fuels as ethanol is an effective way to reduce greenhouse gas emissions. Nowadays, direct injection (DI) and variable valve timing (VVT) technologies are also used in modern downsized engines to reach higher thermal efficiencies with advanced strategies operation. As a significant part of energy losses in a spark ignition (SI) engine is caused by pumping work due to the method used for load control, operation in lean conditions have the potential to increase engine efficiency due to less pumping work requirement.

The mathematical modeling and simulation of an SI engine combustion cycle has contributed for its development, leading to the improvement of the engine purpose to convert the chemical energy of a fuel into mechanical energy through the movement of a piston. The simulation of this models allows the efficiency evaluation of the fuel combustion by generating performance parameters. The Matlab® software, a high-level language and interactive environment, were used for the creation of an add-on based on graphical user interface (GUI), capable of simulating the combustion cycle of a SI engine fuelled by wet ethanol with user-supplied initial parameters.

Various studies previously conducted have estimated the net energy value for ethanol, but the variations of data and assumptions used caused the results to lack in precision. However, studies are unanimous in pointing out that the greatest fraction of the energy necessary for making ethanol is spent in water removal (distillation and dehydration), growing exponentially the smaller the amount of water in the final product. By using wet ethanol to avoid the energy cost of dehydration, the purposes of this work were to numerically evaluate the energy spent in the distillation process and compare the results with the efficiency in using wet ethanol as fuel. The simulation was modelled through Matlab® software environment, using as base a distillation column for batch process with a variable number of plates to obtain as a final product ethanol with different degrees of hydration.

Zero-dimensional zonal models are seen as interesting tools for engine simulation due to their simplicity and yet accuracy in fitting or predicting experimental data. For combustion, a common model is a dual zone model, in which two-zones, spatially homogeneous, are set during the combustion process. Such model take into account an interface of infinitesimal thickness for the separation between zones. The success of this simulation approach depends on the accuracy of the heat transfer model. These models aim to obtain the heat transfer coefficient from the combustion gases in contact with the cylinder walls. Several heat transfer correlations from the literature can be used to obtain the heat transfer coefficient.