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Liquid atomisation is an important technical field for a wide range of engineering and industrial applications, particularly in the field of internal combustion engines. In these engines, in fact, the amount of pollutants at the engine-out interface is directly related to the quality of the combustion process, which is in turn determined by the quality of the air-fuel mixture preparation in Direct Injection (DI) engines. As a consequence numerical-experimental research is crucial to their development. Despite the significant amount of research that has been carried out on DI engines simulation, breakup modelling is still a challenge. In this paper we present a new numerical model for multiphase flows that could be particularly suited for liquid jet and droplet breakup simulation. The model is based on a Lattice Boltzmann (LB) solver coupled to a higher order finite difference treatment of the kinetic forces arising from non-ideal interactions (potential energy).

Spray formation and break-up are crucial phenomena for mixture formation inside diesel engines, both for combustion control and pollutant formation. Since the emission restrictions have become more and more severe in the last years, many studies have been conducted in order to improve diesel injection. Numerical simulations have proven to be reliable in producing results in a faster and cheaper way than experimental measures. The recent great progresses in computer science, then, have allowed to reach great accuracy in the simulations. In this work, a novel methodology based on Boltzmanns Kinetic Theory is applied to diesel injection. Lattice Boltzmann BGK (LBGK) provides and alternative method for solving fluid-dynamic problems and allows even superior accuracy as compared to conventional CFD. The multiphase approach used in this paper to study spray formation and primary is based on the works by Shan and Chen and their successive modifications.

Thermal comfort in the vehicle cabin environment is an important factor for passengers of both internal combustion engines and electric vehicles. Heating, Ventilation and Air Conditioning (HVAC) is a critical system for electric vehicles (EVs) as it is the second most power consumer after electric motor. Novel solutions dedicated to EV, including thermoelectric air conditioning (AC) modules, vapor compression refrigeration (VCR), cycle positive temperature coefficient (PTC) heater as well as heat pumps (HP), are being investigated to maintain a stable and comfortable interior environment under hot and cold weather conditions. At present, the mostly dominated automotive AC systems are those using R134a refrigerant characterized by high global warming potential. Therefore, an innovative and ecofriendly AC system design still must be developed to supply sufficient cooling or heating capacity while minimizing the influence of the AC system on driving ranges and environmental performance.

In the recent past, an always increasing attention have been addressed to the definition and optimization of the HVAC system for fully electric vehicles. The new vehicle layouts and the different operating temperatures of the whole powertrain ask for a re-thinking of the HVAC concept for the modern architectures. In this ballpark, the possibility to deal with a compact and efficient apparatus without moving parts and capable to provide both cold and hot fluxes is really attractive. This is the reason why this work deals with the design and optimization of a vortex tube for automotive applications. Such a component, in fact, is capable to separate a highly swirled flow in two different branches, a cold one and a hot one (one inlet - two outlets). The balance in between the two obtained mass flows can be simply realized via ruling the backpressure at the hot side, with keeping constant the cold one.

This paper describes and compares different powertrain configurations for the retrofit of a heavy-duty Class 8 truck, powered by a 12.6 liters diesel engine. The engine is firstly equipped with an electrification-oriented organic Rankine cycle (ORC) system and then coupled to a traction electric machine into a hybrid powertrain. An electrification-oriented ORC system can produce enough energy to cover the ancillary loads, which in long-haul applications for freight transportation are quite demanding. Nevertheless, only powertrain hybridization can achieve significant improvements in the overall system efficiency. Both systems may thus be implemented in the same vehicle, but an efficiency improvement is guaranteed only if the system is carefully managed so as to reach a trade-off between the requirements and potential benefits of the ORC system and those of the hybrid powertrain.

Turbulence modeling is a key aspect for the accurate simulation of ICE related fluid flow phenomena. RANS-based turbulence closures are still the preferred modeling framework among industrial users, mainly because they are robust, not much demanding in terms of computational resources and capable to extract ensemble-averaged information on a complete engine cycle without the need for multiple cycles simulation. On the other hand, LES-like approaches are gaining popularity in recent years due to their inherent scale-resolving nature, which allows the detailed modeling of unsteady flow features such as cycle-to-cycle variations in a DI engine. An LES requires however a large number of simulated engine cycles to extract reliable flow statistics, which coupled to the higher spatial and temporal resolution compared to RANS still poses some limits to a wider application of such methodology on realistic engine geometries.

The interest in Unsteady Reynolds-Averaged Navier-Stokes (URANS)/Large Eddy Simulation (LES) hybrids, for the simulation of turbulent flows in Internal Combustion Engines (ICE), is consistently growing. An increasing number of applications can be found in the specialized literature for the past few years, including both seamless and zonal hybrid formulations. Following this trend, we have already developed a Detached Eddy Simulation (DES)-based zonal modeling technique, which was found to have adequate scale-resolving capabilities in several engine-like reference tests. In the present article we further extend our study by evaluating the effects of the underlying turbulence model and of the grid quality/morphology on the scale-resolved part of the flow. For that purpose, we consider DES formulations based on an enhanced version of the k-g URANS model and on the URANS form of the popular RNG k-ε model.

The main objective of the paper is to describe the optimization work performed to adjust direct injection (DI)-technology to SI-engines running at high (8000 to 10000 rpm.) and extremely high speeds (more than 18000 rpm). In the first category are located a certain number of small and middle displacement two-stroke series produced engines. In the second category are the typical high power racing engines used for competitions like the formula 1. The first part of the paper describes the particular requirements that an in-cylinder fuelling and mixture preparation will have to fulfill with the extremely short period available for introduction and vaporization of the fuel. The paper continues with a description of the different spray shapes, spray penetration velocities and atomization capabilities, which are optimal for the different combustion chamber architectures.

The first part of the paper gives an overview of the current results obtained with the first-generation of GDI-powered vehicles launched on the European market. In view of the rather limited success in fuel consumption gain the second-generation of very lean stratified layouts has begun, but this process requires the development and application of new high-level analysis tools. A possible high performance approach is the multi-purpose use of 3-D numerical simulation both in the development and the engine control strategy calibration phases. The development of a small 1.6 liter lean stratified engine project was chosen to demonstrate the dual application capability of the NCF-3D simulation tool. The paper continues with a description of the engine application frame, the basic features of the NCF-3D simulation tool and the latest enhancements made to combustion and fuel composition models within the software frame.

A hybrid model for the atomization of Diesel sprays was developed [1]. The model was added to the KIVA code to better simulate spray evolution. Different implementation for low-medium and high injection pressure sprays are performed. It has already been validated for the low-pressure case [1,2] and in this work it was tested for high injection pressure systems, in a vessel at ambient conditions. It distinguishes between jet primary breakup and droplet secondary breakup. For the latter distinct models are used, as the droplet Weber number changes in the various regimes, in order to take into account the effects of the different relevant forces. For high pressure Diesel spray the effects of jet turbulence, cavitation and nozzle flow on liquid core primary breakup must be considered. Due to the high droplet velocity the catastrophic secondary breakup regime may occur.

The recent innovations on automotive Diesel engines require significant research efforts. The new generation of fully electronically controlled injection systems have opened new ways to reduce emissions and improve the efficiency of the engine. The free mapping of injection law together with the enhanced injection pressures favor, in fact, the optimization of mixture formation. In this field, the 3D simulation is playing a substantial role to support the design of combustion chamber. This paper presents a computational model to simulate the multi-injection process, the mixture formation and the combustion of DI diesel engines with high-pressure injection systems. The main code is a modified version of the KIVA 3V and the modifications presented in this work are a high pressure break up model and a multi component evaporation model. The code has been validated through experimental data on a 4-cylinder, 1910 cc, DI turbocharged Diesel engine (Fiat 1.9 JTD).

In the present paper are examined the consequences of a substantial rise in the injection pressure for Gasoline Direct Injection (GDI) injector assemblies. The paper presents a comparative study of the spray behavior of two different injector nozzle layouts submitted to current 10 Mpa rail-pressure as well as to a 30 Mpa injection pressure. To evaluate the differences in the fundamental physical spray parameters are used several specially developed optical visualization techniques, which enable phase-Doppler, PIV, Laser-sheet and high-speed recordings of dense high pressure fuel sprays. A recently developed injector actuator and the necessary modifications to existing high-pressure pumps to reach a 30 MPa pressure level in the fuel system are presented. The change in basic spray parameters (time-resolved droplet distribution and spray momentum) caused by the rail-pressure rise is examined.

The paper presents a study of a key-element in the mixture preparation process. A typical common-rail (CR) high-pressure fuel injector was fitted with a prototype injector nozzle with atomizer bores of a particular conical layout. It is demonstrated within certain layout limits, that a considerable enhancement can be obtained for the secondary break-up of the hard-core fluid sprays produced by the nozzle. The impact on the combustion process is examined in terms of pressure and heat release as well as of the engine-out pollutant emission. The results are compared to those of an earlier developed CR high-pressure injector nozzle. The atomization behavior of the prototype nozzle is illustrated through experimental results in terms of engine-out emissions from a 1.3-liter turbo-charged passenger car diesel engine. The detailed spray behavior is visualized on a component test rig by use of specially developed optical visualization techniques.

In this paper a numerical analysis is carried out of the flow characteristics in the intake system of a high performance engine. To this aim, the experimental flow bench results - obtained in tests performed on a Ducati Corse 4 valves racing engine head and presented in the parallel work [1] - are compared with the numerical ones. In [1] an experimental analysis was performed to evaluate the influence, on the flow characteristics in the intake system of a high performance 4 stroke - 4 valve internal combustion engine Notwithstanding the macroscopic meaning of the measured global coefficients Cd (Discharge Coefficient) and Nt (Tumble Number), the comparative analysis of their respective trends allowed some hypotheses to be drawn on the flow development internally to intake system ducts. In order to confirm the conclusions drawn in [1] and to reach a deeper insight in the flow characteristics, numerical simulations were performed.

A two-equation Zonal-DES (ZDES) approach has been recently proposed by the authors as a suitable hybrid URANS/LES turbulence modeling alternative for Internal Combustion Engine flows. This approach is conceptually simple, as it is all based on a single URANS-like framework and the user is only required to explicitly mark which parts of the domain will be simulated in URANS, DES or LES mode. The ZDES rationale was initially developed for external aerodynamics applications, where the flow is statistically steady and the transition between zones of different types usually happens in the URANS-to-DES or URANS-to-LES direction. The same “one-way” transition process has been found to be fairly efficient also in steady-state internal flows with engine-like characteristics, such as abrupt expansions or intake ports with fixed valve position.

Computational Fluid Dynamics is nowadays largely employed as an effective optimization tool in the automotive industry, especially for what concerns aerodynamic design driven by critical factors such as the engine cooling system optimization and the reduction of drag forces, both limited by continuously changing stylistic constraints. The Ahmed reference model is a generic car-type bluff body with a slant back, which is frequently used as a benchmark test case by industrial as well as academic researchers, in order to investigate the performances of different turbulence modeling approaches. In spite of its relatively simple geometry, the Ahmed model possesses many of the typical aerodynamic features of a modern passenger car - a bluff body with separated boundary layers, recirculating flows and complex three-dimensional wake structures.

An engine head for microcar applications has been analysed and optimized by means of uncoupled CFD and FEM simulations in order to assess the strength of the component. This paper deals with a structural stress analysis of the cylinder head considering the thermal loads computed through an uncoupled CFD simulations of cylinder combustion and in cooling flow passages. The FE model includes the contact interaction between the main parts of the cylinder head assembly and it also considers the effects of bolts tightening and valve springs. Temperature dependent non-linear material properties are considered. The results, in term of temperature field, are validated by comparing with those obtained by means of experimental analyses; the engine has been instrumented with thermocouples on crank case and on cylinder head.

Though CFD methods have become very popular and widespread tools in the early as well as more advanced automotive design stages, they are still not so common in the motorcycle industry branch. The present work aims at the development of a comprehensive simulation environment, based on the open-source finite volume toolbox OpenFOAM®, for the aerodynamic and thermal fluxes optimization of a full motorcycle-and-rider geometry. The paper is divided in two parts: in the first one, the OpenFOAM® code is evaluated for a cold flow aerodynamic analysis, using a slightly simplified version of the Aprilia RSV4 motorbike geometry; in the second one, a mixed reduced scale-full scale methodology is proposed for the simultaneous assessment of aerodynamic forces and heat transfer performances of the engine cooling system. Results have been compared against other well established commercial CFD packages and, where available, with experimental measurements.

An engine head of a common rail direct injection engine with three in line cylinders for Light Transportation Vehicle (LTV) applications has been analyzed and optimized by means of uncoupled CFD and FEM simulations in order to assess the strength of the components. This paper deals with a structural stress analysis of the cylinder head considering the thermal loads computed through an CFD simulation and a detailed FV heat-transfer analysis. The FE model of the cylinder head includes the contact interaction between the main parts of the cylinder head assembly and it is subjected to the gas pressure, thermal loads and the effects of bolts tightening and valve springs. The results, in term of temperature field, are validated by comparing with those obtained by means of experimental analyses. Then a fatigue assessment of the cylinder head has been performed using a multi-axial fatigue criterion.

The present paper describes a study, which can enable a small displacement (1.3 liter) turbocharged European CR-diesel engine to tolerate an important increase in EGR-level. The analysis is performed by use of a 3D virtual numerical engine model, which isolates the main parameters that must be optimized within the perimeter of the combustion chamber. The paper gives a short introduction to the physical background for NOx and soot-formation as well as a recall of the main issues related to the simulation models used in the virtual engine simulation. The analysis is performed in a 9 points load/speed test matrix. Several EGR-rates are studied as well as the impact of a precise temperature control of the exhaust gas re-introduced in the intake manifold. The paper concludes by an analysis of the cumulated impact on the EGR-level tolerated by the engine after the introduction of the suggested optimization measures.