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A growing number of electric vehicles (EV) and hybrid electric vehicles (HEV) in the present market depicts the rapid growing demand for energy storage systems. The battery’s main peculiarities must be the power density and reliability over time. The temperature strongly affects battery performance for low and high intensity. In particular, the management of the heat generated by the battery itself is one of the main aspects to handle to preserve the performance over time. The objective of this paper is to compare the surface temperature of the lithium-ion polymer battery at different discharging rates by infrared thermography. Thermal imaging is performed to detect the battery surface temperature distribution, focusing on its variation over time and the local inhomogeneity. Temperature measurements are then used to estimate the contributions of the different heat transfer mechanisms for the dissipation of the heat generated by the battery.

Within the context of distributed power generation, small size systems driven by spark ignition engines represent a valid and user-friendly choice, that ensures good fuel flexibility. One issue is that such applications are run at part load for extensive periods, thus lowering fuel economy. Employing an inverter (fitted between the generator and load) allows engine operation within a wide range of crankshaft rotational velocity, therefore improving efficiency. For the purpose of evaluating the benefits of this technology within a co-generation framework, two configurations were modeled by using the GT-Power simulation software. After model calibration based on measurements on a small size engine for two-wheel applications, the downsized version was compared to a larger power unit operated at constant engine speed for a scenario that featured up to 10 kW rated power.

Quasi-dimensional modeling is used on a wide scale in engine development, given its potential for saving time and resources compared to experimental investigations. Often it is preferred to more complex CFD codes that are much more computationally intensive. Accuracy is one major issue of quasi-dimensional simulations and for this reason sub-models are continuously developed for improving predictive capabilities. This study considers the use of equivalent fluid velocity and characteristic length scales for simulating the processes of fresh charge entrainment and oxidation behind the flame front. Rather than dividing combustion into three different phases (i.e. laminar kernel, turbulent flame propagation and oxidation near the walls), the concept of turbulent heat and mass transfer is imposed throughout the entire process.

The management of multiple injections in compression ignition (CI) engines is one of the most common ways to increase engine performance by avoiding hardware modifications and after-treatment systems. Great attention is given to the profile of the injection rate since it controls the fuel delivery in the cylinder. The Injection Rate Shaping (IRS) is a technique that aims to manage the quantity of injected fuel during the injection process via a proper definition of the injection timing (injection duration and dwell time). In particular, it consists in closer and centered injection events and in a split main injection with a very small dwell time. From the experimental point of view, the performance of an IRS strategy has been studied in an optical CI engine. In particular, liquid and vapor phases of the injected fuel have been acquired via visible and infrared imaging, respectively. Injection parameters, like penetration and cone angle have been determined and analyzed.

Multi-fuel operation is one of the main topics of investigative research in the field of internal combustion engines. Spark ignition (SI) power units are relatively easily adaptable to alternative liquid-as well as gaseous-fuels, with mixture preparation being the main modification required. Numerical simulations are used on an ever wider scale in engine research in order to reduce costs associated with experimental investigations. In this sense, quasi-dimensional models provide acceptable accuracy with reduced computational efforts. Within this context, the present study puts under scrutiny the assumption of spherical flame propagation and how calibration of a two-zone combustion simulation is affected when changing fuel type. A quasi-dimensional model was calibrated based on measured in-cylinder pressure, and numerical results related to the two-zone volumes were compared to recorded flame imaging.

Gasoline direct injection (GDI) allows flexible operation of spark ignition engines for reduced fuel consumption and low pollutants emissions. The choice of the best combination of the different parameters that affect the energy conversion process and the environmental impact of a given engine may either resort to experimental characterizations or to computational fluid dynamics (CFD). Under this perspective, present work is aimed at discussing the assessment of a CFD-optimization (CFD-O) procedure for the highest performance of a GDI engine operated lean under both single and double injection strategies realized during compression. An experimental characterization of a 4-stroke 4-cylinder optically accessible engine, working stratified lean under single injection, is first carried out to collect a set of data necessary for the validation of a properly developed 3D engine model.

Present work investigates both experimentally and numerically the benefits deriving from the use of split injections in increasing the engine power output and reducing the tendency to knock of a gasoline direct injection (GDI) engine. The here considered system is characterized by an optical access to the combustion chamber. Imaging in the UV-visible range is carried out by means of a high spatial and temporal resolution camera through an endoscopic system and a transparent window placed in the piston head. This last is modified to allow the view of the whole combustion chamber almost until the cylinder walls, to include the so-called eng-gas zones of the mixture, where undesired self-ignition may occur under some circumstances. Optical data are correlated to in-cylinder pressure oscillations on a cycle resolved basis.

The present paper deals with a comprehensive analysis of the knocking phenomenon through experiments and numerical simulations. Conventional and non-conventional measurements are performed on a 4-stroke, 4-cylinder, turbocharged GDI engine. The engine exhibits optical accesses to the combustion chamber. Imaging in the UV-visible range is carried out by means of a high spatial and temporal resolution camera through an endoscopic system and a transparent window in the piston head. This last is modified to allow the view of the whole combustion chamber almost until the cylinder walls, to include the so-called eng-gas zones. Optical data are correlated to in-cylinder pressure-based indicated analyses in a cycle resolved approach.

In recent years, several studies on the efficiency of modern diesel engines have focused on the modeling of combustion process in its different phases. Here, analytical equations are used to describe the physical phenomena that occur in the cylinder. The good agreement between the experimental and simulated data could improve the predictive capabilities of the computational code and reduce the cost of experimental activities. For the modeling of a diesel spray, the first step has been to investigate its behavior in a non-combusting environment; in particular, Musculus and Kattke proposed a model for the simulation of the injection of fuel in non-reacting still environment. Starting from that knowledge, the authors apply the injection model to a compression ignition research engine. By means of an optical engine, injection phase has been investigated via 2D digital imaging. The main jet characteristics like penetration and dispersion angle have been measured.

This paper is focused on the development and application of a CFD methodology that can be applied to predict the fuel-air mixing process in stratified charge, sparkignition engines. The Eulerian-Lagrangian approach was used to model the spray evolution together with a liquid film model that properly takes into account its effects on the fuel-air mixing process into account. However, numerical simulation of stratified combustion in SI engines is a very challenging task for CFD modeling, due to the complex interaction of different physical phenomena involving turbulent, reacting and multiphase flows evolving inside a moving geometry. Hence, for a proper assessment of the different sub-models involved a detailed set of experimental optical data is required. To this end, a large experimental database was built by the authors.

The paper investigates the idle operating condition of a current production turbocharged Gasoline Direct Injected (GDI) high performance engine both from an experimental and a numerical perspective. Due to the low engine speed, to the low injection pressure and to the null contribution of the turbocharger, the engine condition is far from the standard points of investigation. According to the low heat flux due to combustion, temperature levels are low and reduced fuel evaporation is expected. Consequently, fuel spray evolution within the combustion chamber and spray/wall interaction are key points for the understanding of the combustion process. In order to properly investigate and understand the many complex phenomena, a wide set of engine speeds was experimentally investigated and, as far as the understanding of the physics of spray/wall interaction is concerned, many different injection strategies are tested.