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New measurements have been done in order to obtain information concerning the effect of EGR and a paraffinic hydrotreated fuel for the smoke and NO emissions of a heavy-duty diesel engine. Measured smoke number and NO emissions are explained using detailed chemical kinetic calculations and CFD simulations. The local conditions in the research engine are analyzed by creating equivalence ratio - temperature (Phi-T) maps and analyzing the CFD results within these maps. The study uses different amount of EGR and two different diesel fuels; standard EN590 diesel fuel and a paraffinic hydrotreated vegetable oil (HVO). The detailed chemical kinetic calculations take into account the different EGR rates and the properties of the fuels. The residence time in the kinetical calculations is used to explain sooting combustion behavior within diesel combustion. It was observed that NO emission trends can be well captured with the Phi-T maps but the situation is more difficult with the engine smoke.

The engine fueled with methane/diesel is a promising and highly attractive operation mode due to its high performance-to-cost ratio and clean-burning qualities. However, the combustion process and chemical reactions in dual fuel combustion are highly complex, involving short transient pilot-fuel injection into the premixed gaseous fuel charge, autoignition, and combustion mode transition into premixed flame propagation. The motivation of the current investigation is to gain an insight into the combustion dynamics in dual fuel combustion engine based on chemical radicals and thermal radiation. The chemiluminescence (CL) and natural luminosity (NL) are expected to provide specific characteristics in combustion control and monitoring. To visualize the highly unsteady combustion process in terms of OH*, CH2O* radicals and natural luminous emissions, the band pass filters with 308 nm, 330 nm combined with an image doubler are employed to visualize the OH* and CH2O* CL simultaneously.

Spray evolution in diesel engines plays a crucial role in fuel-air mixing, ignition behavior, combustion characteristics, and emissions. There is a variety of phenomenological spray models and computational fluid dynamics (CFD) simulations have been applied to characterize the spray evolution and fuel-air mixing. However, most studies were focused on the spray phenomenon under a limited range of injection and ambient conditions. Especially, the prediction of spray geometry in multi-hole injectors remains a great challenge due to the lack of understanding of the complicated flow dynamics. To overcome the challenges, a series of spray experiments were carried out in a constant volume spray chamber (CVSC) coupled with high-speed Mie-scattering imaging to obtain the spray characteristics at various injection and ambient conditions.

This study presents a novel crank mechanism which enables easy and fast compression ratio adjustment. The novel crank mechanism and piston travel are explained and highlighted. The basic idea is that eccentric gear is installed on a crankshaft web. Eccentric gear is fitted to the big end of the connection rod and eccentricity is controlled by rotating the control gear a discrete amount. Thus the position of eccentricity is varied and controls an effective stroke length. The compression ratio is adjusted to best fit current load demand, either optimizing fuel efficiency or engine power and torque. Adjustments are individual to each cylinder. The system is capable of adjusting from min to max within 10 milliseconds [ms]. Emphasis is on reduction of CO2 emissions and reducing fuel consumption, especially at part load condition. The governing mechanical equations are presented.

The present-day transport sector needs sustainable energy solutions. Substitution of fossil-fuels with fuels produced from biomass is one of the most relevant solutions for the sector. Nevertheless, bringing biofuels into the market is associated with many challenges that policymakers, feedstock suppliers, fuel producers, and engine manufacturers need to overcome. The main objective of this research is an investigation of the impact of alternative fuel properties on light vehicle engine performance and greenhouse gases (GHG). The purpose of the present study is to provide decision-makers with tools that will accelerate the implementation of biofuels into the market. As a result, two models were developed, that represent the impact of fuel properties on engine performance in a uniform and reliable way but also with very high accuracy (coefficients of determination over 0.95) and from the end-user point of view.

This paper aims to study numerically the influence of the number of fuel sprays in a single-cylinder diesel engine on mixing and combustion. The CFD simulations are carried out for a heavy-duty diesel engine with an 8 hole injector in the standard configuration. The fuel spray mass-flow rate was obtained from 1D-simulations and has been adjusted according to the number of nozzle holes to keep the total injected fuel mass constant. Two cases concerning the modified mass-flow rate are studied. In the first case the injection time was decreased whereas in the second case the nozzle hole diameter was decreased. In both cases the amount of nozzle holes (i.e. fuel sprays) was increased in several steps to 18 holes. Quantitative analyses were performed for the local air-fuel ratio, homogeneity of mixture distribution, heat release rate and the resulting in-cylinder pressure.

Hydrogen (H2), a potential carbon-neutral fuel, has attracted considerable attention in the automotive industry for transition toward zero-emission. Since the H2 jet dynamics play a significant role in the fuel/air mixing process of direct injection spark ignition (DISI) engines, the current study focuses on experimental and numerical investigation of a low-pressure H2 jet to assess its mixing behavior. In the experimental campaign, high-speed z-type schlieren imaging is applied in a constant volume chamber and H2 jet characteristics (penetration and cross-sectional area) are calculated by MATLAB and Python-based image post-processing. In addition, the Unsteady Reynolds-Averaged Navier-Stokes (URANS) approach is used in the commercial software Star-CCM+ for numerical simulations.

Ammonia (NH3), as a carbon-free fuel, has a higher optimization potential to power internal combustion engines (ICEs) compared to hydrogen due to its relatively high energy density (7.1MJ/L), with an established transportation network and high flexibility. However, the NH3 is still far underdeveloped as fuel for ICE application because of its completely different chemical and physical properties compared with hydrocarbon fuels. Among all uncertainties, the dynamics of the NH3 spray at engine conditions is one of the most important factors that should be clarified for optimizing the fuel-air mixing. To characterize the evolution and evaporation process of NH3 spray, a high-speed Z-type schlieren imaging technique is employed to estimate the spray characteristics under different injection pressure and air densities in a constant volume chamber.

Dual-fuel technology is suggested as a solution for effectively utilizing alternative fuel types in the near future. Charge air mixed methane combined with a compression ignition engine utilizing a small diesel pilot injection seems to form a worthwhile compromise between good engine efficiency and low emission outcome. Problems concerning dual-fuel technology profitableness seems to be related to fully control the combustion in relation to lean conditions. Lean operating conditions solves the problems concerning pumping losses, but brings challenges in controlling the slow heat release of the premixed methane-air mixture. In the present work, a single cylinder ‘free parameter’ diesel engine was adapted for dual-fuel (diesel-methane) usage. A parameter study related to lambda window widening possibilities was carried out.

Dual fuel (DF) combustion technology as a feasible approach controlling engine-out emissions facilitates the concept of fuel flexibility in diesel engines. The abundance of natural gas (90-95% methane) and its relatively low-price and the clean-burning characteristic has attracted the interest of engine manufacturers. Moreover, with the low C/H ratio and very low soot producing tendency of methane combined with high engine efficiency makes it a viable primary fuel for diesel engines. However, the fundamental knowledge on in-cylinder combustion phenomena still remains limited and needs to be studied for further advances in the research on DF technology. The objective of this study is to investigate the ignition delay with the effect of, 1) methane equivalence ratio, 2) intake air temperature and 3) pilot ratio on the diesel-methane DF-combustion. Combustion phenomenon was visualized in a single cylinder heavy-duty diesel engine modified for DF operations with an optical access.

In the present study, a new approach for modelling emissions of coke particles or cenospheres from large diesel engines using HFO (Heavy fuel oil) was studied. The model used is based on a multicomponent droplet mass transfer and properties model that uses a continuous thermodynamics approach to model the complex composition of the HFO fuel and the resulting evaporation behavior of the fuel droplets. Cenospheres are modelled as the residue left in the fuel droplets towards the end of the simulation. The mass-transfer and fuel properties models were implemented into a cylinder section model based on the Wärtsilä W20 engine in the CFD-code Star CD v.4.24. Different submodels and corresponding parameters were tuned to match experimental data of cylinder pressures available from Wärtsilä for the studied cases. The results obtained from the present model were compared to experimental results found in the literature.

The distribution of spray droplet sizes plays a pivotal role in internal combustion engines, directly affecting fuel-air mixing, evaporation, and combustion. To gain a precise understanding of droplet size distribution in a two-dimensional space, non-intrusive optical diagnostics emerge as a highly effective method. In the current investigation, two-dimensional (2D) diesel spray droplet sizes mapping using a simultaneous combination of planar laser-induced fluorescence (PLIF) and Mie-scattering techniques is introduced. The assessment of droplet diameter relies on the interplay between fluorescent and scattered light intensities which correspond the light based on volumetric droplets and surface area of the droplets. This calculation is made possible through the LIF/Mie technique. However, traditional LIF/Mie methods are plagued by inaccuracies arising from multiple light scattering.