Search Results

In the perspective of a reduction of emissions and a rapid decarbonisation, especially for compression ignition engines, hydrogen plays a decisive role. The dual fuel technology is perfectly suited to the use of hydrogen, a fuel characterized by great energy potential. In fact, replacing, at the same energy content, the fossil fuel with a totally carbon free one, a significant reduction of the greenhouse gases, like carbon dioxide and total hydrocarbon, as well as of the particulate matter can be obtained. The dual fuel with indirect injection of gaseous fuel in the intake manifold, involves the problem of hydrogen autoignition. In order to avoid this difficulty, the optimal conditions for the injection of the incoming mixture into the cylinder were experimentally investigated. All combustion processes are carried out on a research engine with optical access. The engine speed has is set at 1500 rpm, while the EGR valve is deactivated.

Water removal from Proton Exchange Membrane (PEM) Fuel Cell (FC) mainly involves two phenomena: some of the emerging droplets will roll on the Gas Diffusion Layer (GDL), others may impact channel walls and start sliding along the airflow direction. This different behaviour is linked to the hydrophobic/hydrophilic nature of the surface the water is moving on. In this paper, the walls of the channel of a FC were characterized by applying optical techniques. The deposition of droplets on the channel wall led to an evaluation of the proper range for Contact Angle Hysteresis (CAH = 55° - 45°), and due to the high wettability of the surface, droplets dimension was defined with a dimensionless parameter B/H. Under high crossflow condition (15 m/s) a sliding behaviour was observed. The channel features determined through image processing were used as boundary conditions for a 2D CFD two phase simulation employing the Volume of Fluid (VOF) model to keep track of the fluids interface.

The transport of goods and people by sea, today, must meet the need to reduce the consumption of fuel oil. In addition, it has to ensure operational reliability and vessel availability, to reduce maintenance costs and comply with emission legislation. To this end, it is necessary to apply a marine engine combustion control system already widely used in engines for land transport. This will allow the ship's engines to operate reliably and in compliance with the best performance for which it was designed. The combustion control could also ensure a more balanced operation of the cylinders and reduce the torsional vibrations of the entire engine, as well as the management of the engine according to the adopted fuel: diesel, dual fuel, methanol, ammonia. Generally, the control of combustion in engines is carried out through the use of pressure sensors that face directly into the combustion chamber.

Converting spark ignition (SI) engines to H2 fueling is an attractive route for achieving zero carbon transportation and solving the legacy fleet problem in a future scenario in which electric powertrains will dominate. The current paper looks at a small size passenger car in terms of vehicle dynamics and electronic control unit (ECU) remapping requirements, in the hypothesis of using H2 as a gasoline replacement. One major issue with the use of H2 in port fuel injection (PFI) engines is that it causes reduced volumetric efficiency and thus low power. The vehicle considered for the study features turbocharging and therefore complete or partial recuperation of lost power is possible. Other specific requirements such as injection phasing were also under scrutiny, especially as PFI was hypothesized to maximize cost effectiveness. A 0D/1D model was used for simulating engine running characteristics as well as vehicle dynamics.

In this work, a dynamic 0-D electro-thermal model of a lithium-polymer battery for automotive applications is presented. The model predicts the battery temperature during its charging/discharging phases under different environmental and operating conditions, by considering the requested power or current, the coolant flow rate and its temperature as model inputs. The model was first validated with experimental data carried out at the test bench where only the convective heat transfer between the battery and the ambient air was considered. The accuracy of the internal heat generation model was experimentally assessed for different current discharge rates. Then, a liquid cooling system was designed on purpose, assembled, and installed on the battery at the test bench for the improvement of the model predictions in liquid convection conditions.

In order to reduce fuel consumption and polluting emissions from engines, alternative fuels such as hydrogen could play an important role towards carbon neutrality. Moreover, dual-fuel (DF) technology has the potential to offer significant improvements in carbon dioxide emissions for transportation and energy sectors. The dual fuel concept (natural gas/diesel or hydrogen/diesel) represents a possible solution to reduce emissions from diesel engines by using low-carbon or carbon-free gaseous fuels as an alternative fuel. Moreover, DF combustion is a possible retrofit solution to current diesel engines by installing a PFI injector in the intake manifold while diesel is injected directly into the cylinder to ignite the premixed mixture. In the present study, dual fuel operation has been investigated in a single cylinder research engine.

The application of an alternative fuel such as hydrogen to internal combustion engines is proving to be an effective and flexible solution for reducing fuel consumption and polluting emissions from engines. An easy to use and immediate application solution is the dual fuel (DF) technology. It has the potential to offer significant improvements in carbon dioxide emissions from light compression ignition engines. The dual fuel concept (natural gas / diesel or hydrogen / diesel) represents a possible solution to reduce emissions from diesel engines by using low-carbon or carbon-free gaseous fuels as an alternative fuel. Moreover, DF combustion is a possible retrofit solution to current diesel engines by installing a PFI injector in the intake manifold while diesel is injected directly into the cylinder to ignite the premixed mixture. In the present study, dual fuel operation has been investigated in a single cylinder research engine.

Pre-chamber combustion (PCC) has re-emerged in recent last years as a potential solution to help to decarbonize the transport sector with its improved engine efficiency as well as providing lower emissions. Research into the combustion process inside the pre-chamber is still a challenge due to the high pressure and temperatures, the geometrical restrictions, and the short combustion durations. Some fundamental studies in constant volume combustion chambers (CVCC) at low and medium working pressures have shown the complexity of the process and the influence of high pressures on the turbulence levels. In this study, the pre-chamber combustion process was investigated by combustion visualization in an optically-accessible pre-chamber under engine relevant conditions and linked with the jet emergence inside the main chamber. The pre-chamber geometry has a narrow-throat. The total nozzle area is distributed in two six-hole rows of nozzle holes.

Many aspects of battery electric vehicles are very challenging from the engineering point of view in terms of safety, weight, range, and drivability. Commercial vehicle engines are often subjected to high loads even at low speeds and this can lead to an intense increment of the battery pack temperature and stress of the cooling system. For these reasons the optimal design of the battery pack and the relative cooling system is essential. The present study deals with the challenge of designing a battery pack that satisfies both the conditions of lowest weight and efficient temperature control. The trade-off between the battery pack size and the electrical stress on the cells is considered. The electric system has the aim to substitute a 3.0 liters compression ignition engine mainly for commercial vehicles.

Methane supply in diesel engines operating in dual fuel mode has demonstrated to be effective for the reduction of particulate matter and nitric oxides emissions from this type of engine. In particular, methane is injected into the intake manifold to form a premixed charge with air, while a reduced amount of diesel oil is still directly injected to ignite the mixture inside the cylinder. As a matter of fact, the liquid fuel burns following the usual diffusive combustion, so activating the gaseous fuel oxidation in a premixed flame. Clearly, the whole combustion process appears to be more complex to be described in a CFD simulation, mainly because it is not always possible to select in the 3-dimensional codes a different combustion model for each fuel and, also, because other issues arise from the interaction of the two fuels.

In the last few years, concern about the environmental impact of vehicles has increased, considering the growth of the dangerous effects on health of noxious exhaust emissions. For this reason, car manufacturers are moving towards more efficient combustion systems for Spark Ignition (SI) engines, aiming to comply with the increasingly stringent regulation imposed by EU and other legislators. Engine operation with very lean air/fuel ratios has demonstrated to be a viable solution to this problem. Stable ultra-lean combustion can be obtained with a Pre-Chamber (PC) ignition system, installed in place of the conventional spark plug. The efficiency of this configuration in terms of performance and emissions is due to its combustion process, that starts in the PC and propagates in the main chamber in the form of multiple hot turbulent jets.

High-pressure internal combustion engines promise high efficiency, but a proper injection strategy to minimize heat losses and pollutant emissions remain a challenge. Previous studies have concluded that two injectors, placed at the piston bowl's rim, simultaneously improve the mixing and reduce the heat losses. The two-injector configuration further improves air utilization while keeping hot zones away from the cylinder walls. This study investigates how the two-injector concept delivers even higher efficiency by providing additional control of spray -and injection angles. Three-dimensional Reynolds-averaged Navier-Stokes simulations examined several umbrella angles, spray-to-spray angles, and injection orientations by comparing the two-injector cases with a reference one-injector case. The study focused on heat transfer reduction, where the two-injector approach reduces the heat transfer losses by up to 14.3 % compared to the reference case.

Pre-chamber Combustion (PCC) extends the lean operation limit operation of spark ignition (SI) engines, thus it has been of interest for researchers as a pathway for increased efficiency and reduced emissions. Optical diagnostic techniques are essential to understand the combustion process, but the engine components such as the piston geometry, are often different from real engines to maximize the optical access. In this study, ignition and subsequent main chamber combustion are compared in an optically accessible PCC engine equipped with a “flat” and a real engine-like “bowl” piston geometry. An active fueled narrow throat pre-chamber was used as the ignition source of the charge in the main-chamber, and both chambers were fueled with methane. Three pre-chamber fuel effective mean pressure (FuelMEP) ratios (PCFR) namely 6%, 9% and 11% of the total amount of fuel were tested at two global excess air ratios (λ) at values of 1.8 and 2.0.

Heavy-duty vehicles face increasing demands of emission regulations. Reduced carbon-dioxide (CO2) emission targets motivate decreased fuel consumption for fossil fuel engines. Increased engine efficiency contributes to lower fuel consumption and can be achieved by lower heat transfer, friction and exhaust losses. The double compression expansion engine (DCEE) concept achieves higher efficiency, as it utilizes a split-cycle approach to increase the in-cylinder pressure and recover the normally wasted exhaust energy. However, the DCEE concept suffers heat losses from the high-pressure approach. This study utilizes up to three injectors to reduce the wall-gas temperature gradient rendering lower convective heat losses. The injector configuration consists of a standard central injector and two side-injectors placed at the rim of the bowl. An increased distance from side-injector to the wall delivered lower heat losses by centralizing hot gases in the combustion chamber.

Pollutant emission of vehicle cars is nowadays a fundamental aspect to take into account. In the last decays, the company have been forced to study new solutions, such as alternative fuel and learn burn mixture strategy, to reduce the vehicle’s pollutants below the limits imposed by emission regulations. Pre-chamber ignition system presents potential reductions in emission levels and fuel consumption, operating with lean burn mixtures and alternative fuels. As alternative fuels, methane is considered one of the most interesting. It has wider flammable limits and better anti-knock properties than gasoline. Moreover, it is characterized by lower CO2 emissions. The aim of this work is to study the evolution of the plasma jets in a different in-cylinder conditions. The activity was carried out in a research optical small spark ignition engine equipped alternatively with standard ignition system and per-chamber.

Engine knock is an abnormal phenomenon, which places barriers for modern Spark-Ignition (SI) engines to achieve higher thermal efficiency and better performance. In order to trigger more controllable knock events for study while keeping the knock intensity at restricted range, various spark strategies (e.g. spark timing, spark number, spark location) are applied to investigate on their influences on knock combustion characteristics and pressure oscillations. The experiment is implemented on a modified single cylinder Compression-Ignition (CI) engine operated at SI mode with port fuel injection (PFI). A specialized liner with 4 side spark plugs and 4 pressure sensors is used to generate various flame propagation processes, which leads to different auto-ignition onsets and knock development. Based on multiple channels of pressure signals, a band-pass filter is applied to obtain the pressure oscillations with respect to different spark strategies.

Pre-chamber combustion (PCC) allows an extension on the lean limit of an internal combustion engine (ICE). This combustion mode provides lower NOx emissions and shorter combustion durations that lead to a higher indicated efficiency. In the present work, a narrow throat pre-chamber was tested, which has a unique nozzle area distribution in two rows of six nozzle holes each. Tests were carried out in a modified heavy-duty engine for optical visualization. Methane was used as fuel for both the pre-chamber and the main chamber. Seven operating points were tested, including passive pre-chamber mode as a limit condition, to study the effect of pre- and main-chamber fuel addition on the pre-chamber jets and the main chamber combustion via chemiluminescence imaging. A typical cycle of one of the tested conditions is explained through the captured images. Observations of the typical cycle reveal a predominant presence of only six jets (from the lower row), with well-defined jet structures.

Growing concerns about the emissions of internal combustion engines have forced the adoption of aftertreatment devices to reduce the adverse impact of diesel engines on health and environment. Diesel particulate filters are considered as an effective means to reduce the particle emissions and comply with the regulations. Research activity in this field focuses on filter configuration, materials and aging, on understanding the variation of soot layer properties during time, on defining of the optimal strategy of DPF management for on-board control applications. A model was implemented in order to simulate the filtration and regeneration processes of a wall-flow particulate filter, taking into account the emission characteristic of the engine, whose architecture and operating conditions deeply affect the size distribution of soot particles.

Stringent emission regulations and the anticipated climate change call for a paradigm shift in the design of the conventional internal combustion engines. One way to combat this problem is oxy-fuel combustion in which the combustion products are mainly water vapor and carbon dioxide. Water vapor can be easily separated by condensation and carbon dioxide is then easily captured and stored. However, many technical challenges are associated with this mode of combustion. There are many challenges facing oxy-fuel combustion before it find its way to commercial production especially for internal combustion engines. One such challenge is the relatively high temperature of the oxy-fuel combustion. A solution to this problem is the recirculation of the generated CO2 to moderate the in-cylinder temperature. Therefore, careful study of the effect of recirculating the CO2 back to combustion chamber is needed before the implementation of such a concept.

Pre-chamber combustion (PCC) enables leaner air-fuel ratio operation by improving its ignitability and extending flammability limit, and consequently, offers better thermal efficiency than conventional spark ignition operation. The geometry and fuel concentration of the pre-chamber (PC) is one of the major parameters that affect overall performance. To understand the dynamics of the PCC in practical engine conditions, this study focused on (i) correlation of the events in the main chamber (MC) with the measured in-cylinder pressure traces and, (ii) the effect of fuel concentration on the MC combustion characteristics using laser diagnostics. We performed simultaneous acetone planar laser-induced fluorescence (PLIF) from the side, and OH* chemiluminescence imaging from the bottom in a heavy-duty optical engine. Two different PC Fueling Ratios (PCFR, the ratio of PC fuel to the total fuel), 7%, and 13%, were investigated.