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The global energy crisis and drastic climate change are continuously promoting the implementation of sustainable energy sources. To meet the emission standards and carbon-neutrality targets in vehicle industry, ammonia is considered to be one of the promising carbon-neutral fuels. However, running the engines on high amounts of ammonia may lead to significantly high ammonia slip. This originates huge safety concerns. Therefore, hydrogen is added in certain ratio with ammonia to promote combustion and reduce ammonia slip. Furthermore, adding diesel as a pilot fuel further facilitates the combustion reactions. This experimental study investigated the effect of different ammonia-hydrogen blend ratios on in-cylinder pressure, heat release rate, cumulative heat release, indicated mean effective pressure (IMEP), indicated thermal efficiency (ITE), CA5 and CA50. This effect of blend ratios was tested for varied diesel pilot amounts and timings.

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.

The current transportation fuels have been one of the biggest contributors towards climate change and greenhouse gas emissions. The use of carbon-free fuels has constantly been endorsed through legislations in order to limit the global greenhouse gas emissions. In this regard, ammonia is seen as a potential alternative fuel, because of its carbon-free nature, higher octane number and as hydrogen carrier. Furthermore, many leading maritime companies are doing enormous research and planning projects to utilize ammonia as their future carbon-free fuel by 2050. Flash boiling phenomenon can significantly improve combustion by enhancing the spray breakup process and ammonia possessing low boiling point, has a considerable potential for flash boiling. However, present literature is missing abundant research data on superheated ammonia sprays.

Decarbonization of the automotive industry is one of the major challenges in the transportation sector, according to the recently proposed climate neutrality policies, e.g., the EU 'Fit for 55' package. Hydrogen as a carbon-free energy career is a promising alternative fuel to reduce greenhouse gas emissions. The main objective of the present study is to investigate non-reactive hydrogen jet impingement on a piston bowl profile at different injection angles and under the effect of various pressure ratios (PR), where PR is the relative ratio of injection pressure (IP) to chamber pressure (CP). This study helps to gain further insight into the mixture formation in a heavy-duty hydrogen engine, which is critical in predicting combustion efficiency. In the experimental campaign, a typical high-speed z-type Schlieren method is applied for visualizing the jet from the lateral windows of a constant volume chamber, and two custom codes are developed for post-processing the results.

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.

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.

A novel high pressure SCR spray system is investigated both experimentally and numerically. RANS simulations are performed using Star-CD and polyhedral meshing. This is one of the first studies to compare droplet breakup models and AdBlue injection with high injection pressure (Pinj=200 bar). The breakup models compared are the Reitz-Diwakar (RD), the Kelvin-Helmholtz and Rayleigh-Taylor (KHRT), and the Enhanced Taylor Analogy Breakup (ETAB) model. The models are compared with standard model parameters typically used in diesel fuel injection studies to assess their performance without any significant parameter tuning. Experimental evidence from similar systems seems to be scarce on high pressure AdBlue (or water) sprays using plain hole nozzles. Due to this, it is difficult to estimate a realistic droplet size distribution accurately. Thereby, there is potential for new experimental data to be made with high pressure AdBlue or water sprays.

The direct injection (DI) natural gas engine is considered as one of the promising technologies to achieve the continuing goals of the higher efficiency and reduced emissions for internal combustion engines. Shock wave phenomena can easily occur near the nozzle exit when high pressure gaseous fuel is injected directly into the engine cylinder. In the present study, high pressure gas issuing from a prototype gas injector was experimentally studied using planar laser-induced fluorescence (PLIF) technique. Acetone was selected as a fuel tracer. The effects of injection pressures on the flow structure and turbulent mixing were investigated based on a series of high resolution images. The jet macroscopic structures, such as jet penetration, cone angle and jet volume, are analyzed under different injection pressures. Results show that barrel shock waves can significantly influence the jet flow structure and turbulent mixing.

Compressed natural gas direct-injection (CNG-DI) engines based on diesel cycle combustion system with pilot ignition have ability to achieve high thermal efficiency and low emissions. Generally, underexpanded jets can be formed when the high pressure natural gas is injected into the combustion chamber. In such conditions, shock wave phenomena are the typical behaviors of the jet, which can significantly influence the downstream flow structure and turbulent mixing. In the present study, the characteristics of high-pressure transient jets were investigated using planar laser-induced fluorescence (PLIF) of acetone as a fuel tracer. The evolution of the pulsed jet shows that there are three typical jet flow patterns (subsonic, moderately underexpanded, and highly underexpanded) during the injection. The full injection process of high-pressure pulsed jets is well described with the help of these shock wave structures.

In this study, one-dimensional fluid dynamics simulation software was utilized in producing common rail diesel fuel injection for varying injection parameters with enhanced accuracy. Injection modeling refinement is motivated by improved comprehension of the effects of various physical phenomena within the injector. In addition, refined injection results yield boundary conditions for three-dimensional CFD simulations. The criteria for successful simulation results were evaluated upon experimental test run data that have been reliably obtained, primarily total injected mass per cycle. A common rail diesel fuel delivery system and its core mechanics were presented. System factors most critical to fuel delivery were focalized. Models of two solenoid-type common rail injectors of different physical sizes and applications were enhanced.

The present paper focuses on gaining a deeper understanding about the turbulent flow inside an engine cylinder using large eddy simulation. While the main motivation of the current study is to gain a deeper understanding of the flow patterns and especially about the swirl, the background motivation of this study is the development and testing of suitable methods for the large eddy simulation of combustion engines and the validation of the used simulation methodology. In particular, we study the swirl and other flow features generated by the intake jets inside the cylinder. The simulated geometry is the Sisu Diesel 84 engine cylinder where the exhaust valves are closed and the intake valves have constant valve lifts. Furthermore, the piston has been removed so that the flow is able to exit from the opposite end of the cylinder.

The aim of current study was to compare the global fuel spray characteristics between renewable hydrotreated vegetable oil (HVO) and crude oil-based EN 590 diesel fuel. According to previous studies, the use of HVO enables reductions in carbon monoxide (CO), total hydrocarbon (THC), nitrogen oxide (NOx) and particle matter (PM) emissions without any changes to the engine or its controls. Fuel injection strategies and global fuel spray characteristics affect on engine combustion and exhaust gas emissions. Due to different physical properties of two different fuels, fuel spray characteristics differ. Fuel spray studies were performed with backlight imaging using a pressurized test chamber imitating real engine conditions at the end of compression stroke. However, the measurements were made in non-evaporative conditions. Various injection parameters such as injection pressures and orifice diameter were tested.

This study focuses on gaining a deeper understanding on the formation of turbulence and other in-cylinder flow structures caused by the intake jets during the intake stroke in internal combustion engines. This is important as the in-cylinder turbulence has a large effect on the mixing of fuel and oxidizer. A fine resolution large eddy simulation (LES) is carried out on an incompressible flow (Re is equivalent to 100,000) over a static valve (lift d = 7 mm) alongside with three other simulations using coarser meshes. The problem is studied in a simplified valve-cylinder geometry on which experimental data by Yasar et al., (2006) is available. The vortex cores, produced by the shear layer of the intake jets, are visualized using the λ₂ definition for vortex cores. The governing flow structures are identified and some features of the flow's mixing capabilities are observed. Additionally, the mixing is studied by releasing a passive scalar into to the flow.

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.

Two different medium-speed diesel engine cylinder head designs have been studied. The focus of the study has been the effect of intake channel design in the in-cylinder flow. The study has been carried out by CFD. The first cylinder head is a standard Wärtsilä 20 cylinder head and the second one is a specially designed head for a single cylinder research engine, called Extreme Value Engine (EVE). The CFD boundary conditions have been simulated by the help of a 1-d simulation code. In the full load cases the maximum cylinder pressure was 300 bar. Simulations have been done at lower load level too. One simulation with the new cylinder head was carried out with one intake valve closed in order to get an idea of the swirl to be generated by this approach. In the study the in-cylinder flow field, the cylinder charge and turbulence kinetic energy have been examined.

Experimental spray tip penetrations obtained from a large-bore medium-speed optical diesel engine were compared to CFD simulations. The optical spray results are unique as they are obtained from a running large-bore (200mm) diesel engine. The experimental spray tip penetration measurements were obtained during the early spray development period when the spray evaporation had not yet reached the quasi steady-state phase. The CFD simulations were conducted in both static chamber environment and in engine conditions. The fuel injection boundary conditions were obtained from 1-D simulations. Within the error margins associated with the experimental and computational data, relatively good accuracy was obtained between measured and simulated spray tip penetration. It was also observed that it is very important to have accurate fuel injection mass flow rate data. This was observed after a sensitivity analysis was made for the injection duration and fuel mass quantity.

The objective of this study is to achieve high reduction of NOx emissions in a medium-speed single-cylinder research engine. The main feature of this research engine is that the gas exchange valve timing is completely adjustable with electro-hydraulic actuators. The study is carried out at high engine load and using a very advanced Miller valve timing. Since the engine has no turbocharger, but a separate charge air system, 1-D simulations are carried out to find the engine setup, which would be close to the operating points of a real engine. The obtained NOx reduction is over 40% with no penalty in fuel consumption.

Fuel spray mixing has been analyzed numerically in a single-cylinder optical research engine with a flat piston top. In the study, a narrow spray angle has been used to align the sprays towards the piston top. Fuel spray mass flow rate has been simulated with 1-D code in order to have reliable boundary condition for the CFD simulations. Different start of fuel injections were tested as well as three charge air pressures and two initial mixture temperatures. Quantitative analysis was performed for the evaporation rates, mixture homogeneity at top dead center, and for the local air-fuel ratios. One of the observations of this study was that there exists an optimum start of fuel injection when the rate of spray evaporation and the mixture homogeneity are considered.

The objective of this study was to build up an optical access into a large bore medium-speed research engine and carry out the first fuel spray Particle Image Velocimetry (PIV) measurements in the running large bore medium-speed engine in high pressure environment. The aim was also to measure spray penetration with same optical access and apparatus. The measurements were performed in a single-cylinder large bore medium-speed research engine, the Extreme Value Engine (EVE) with optical access into the combustion chamber. The authors are not aware of any other studies on optical spray measurements in large bore medium-speed diesel engines. Successful optical measurements of the fuel spray penetration and the velocity fields were carried out. This confirms that the exceptional component design and laser sheet alignment used in this study proved to be valid for optical fuel spray measurements in large-bore medium-speed diesel engines.