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Waste Heat Recovery is one of the major opportunities to increase the engine efficiency in internal combustion engines (ICE) for the transportation sector and to meet the emissions targets. ORC-based units are widely investigated, in particular for heavy duty vehicles and light commercial ones. However, when a typical operation of the ICE on a vehicle is considered, working temperature and exhaust flow rates are not always suitable for recovery, being characterized by low-grade enthalpy. Volumetric expanders are among the most suitable technological solutions for small scale ORC-based power units, but they can suffer of low efficiency in real operation. A way to improve its performances is represented by a supercharging technique, which involves a further intake port.

The use of reciprocating internal combustion engines (ICE) dominates the sector of the on-road transportation, both for passengers and freight. CO2 reduction is the present technological driver, considering the major worldwide greenhouse reduction targets committed by most governments in the western world. In the near future (2020) these targets will require a significant reduction with respect to today’s goals, reinforcing the importance of reducing fuel consumption. In ICEs more than one third of the fuel energy used is rejected into the environment as thermal waste through exhaust gases. Therefore, a greater fuel economy could be achieved if this energy is recovered and converted into useful mechanical or electrical power on board. For long haul vehicles, which run for hundreds of thousands of miles per year at relatively steady conditions, this recovery appears especially worthy of attention.

Internal combustion engines are actually one of the most important source of pollutants and greenhouse gases emissions. In particular, on-the-road transportation sector has taken the environmental challenge of reducing greenhouse gases emissions and worldwide governments set up regulations in order to limit them and fuel consumption from vehicles. Among the several technologies under development, an ORC unit bottomed exhaust gas seems to be very promising, but it still has several complications when it is applied on board of a vehicle (weight, encumbrances, backpressure effect on the engine, safety, reliability). In this paper, a comprehensive mathematical model of an ORC unit bottomed a heavy duty engine, used for commercial vehicle, has been developed.

The theoretical evaluation of the thermal fields in a cylinder liner of Reciprocating Internal Combustion Engines (I.C.E.) requires some attention due the characteristics of the real boundary conditions. For small engines, in fact, these conditions may strongly differ from an axisymmetrical state due to the influence of the thermofluodynamic disuniformities at the gas and, more importantly, at the cooling fluid side. The paper brings together an experimental research on the temperatures at the boundaries with a theoretical analysis on the three-dimensional thermal fields occurring on the liner of a small one cylinder spark ignition research engine operating up to 5000 RPM. The differences found in calculating the heat exchanged using an axisymmetric analysis with respect to the real situation demonstrate the importance of considering the disuniformitites that really occur under working conditions.

The prediction of the transient phenomena in reciprocating internal combustion engine (ICE) manifolds is of great importance in engine design (torque, power, etc…) as well as for the air fuel ratio (A/F) engine control. Those phenomena are dominated by the capacitive and inertial properties of a compressible flow, leading to the propagation of pressure waves traveling upstream and downstream the intake and exhaust manifolds. These can produce benefits or drawbacks in cylinder filling or emptying, so influencing the thermodynamical and environmental performances of the engine. A new method for calculating the transient phenomena in engine manifolds is here presented in a form which is an improvement of a previous formulation presented by one of the author [1]. Following an electric analogy between voltage-speed of sound and current-fluid velocity, the method presents a wider formulation for the solution of the non-homoentropic 1-D advected wave equation in the Laplace domain.

Fuel cells are widely accepted to be the alternative powertrain with the highest potential to compete with the internal combustion engine for a mean-long future sustainable prospective for passenger mobility: Proton Exchange Membrane Fuel Cells (PEMFC) seem to be the most promising technology. Anyway, the final goal is still far to be reached, since often the great potential advantages connected with fuel cells are not completely obtained, due to the difficulties encountered in component design and optimization. Moreover, H2 availability still appears to be one of the most important limitations. Taking the lead by these considerations the authors derived a physically consistent integrated mathematical model of a PEM propulsion system: the model is fully modular and is aimed both to gain a deeper insight of the complex chemical and thermo-fluid-dynamical processes involved, and to the development of control strategies for the propulsion system and all its auxiliaries.

In reciprocating IC engines, very precise predictions of the mass of air inducted are required in order to improve engine design. To achieve this goal, a deeper knowledge of the boundary conditions on intake and exhaust manifolds must be obtained. A set of very accurate experimental data is also needed to perform model validation. In this paper an experimental activity was performed on a pipe test-rig which guarantees high reproducibility of the fluid-dynamic transients. Based on the obtained data, the authors introduced two parameters, which are able to improve the precision of the dynamic models of the flow past valves and through sudden enlargements.

The Quasi-Propagatory Model (QPM), a new approach to simulate fluid transients in duct systems, is presented in this paper. The model fills the gap existing between lumped-parameter and distributed-parameter models, allowing the simulation of propagatory effects, even in a compact, lumped-parameter framework. The model, previously developed for homentropic flows, is extended here to include the presence of section variations, friction and heat flows. This is done without substantially altering the model architecture. A theoretical and an experimental validation of the QPM have been carried out. Test cases have been run and the results compared with those yielded by the Method of Characteristics, which was taken as a reference model. Moreover, the model predictions were also compared with experimental data measured in a pipe test rig.

The design optimization of Continuously Variable Transmission (CVT) belts requires the characterization of actual operating conditions for a correct description of the boundary conditions to be applied in a belt structural analysis. The complex phenomena involved (friction and dynamical contact between belt and pulleys) determine uncertainties on the load distribution along the belt. With the aim of offering a contribution in this direction, this paper presents a theoretical and experimental procedure. It allows for the description of stress and strain state along the belt. This procedure has been applied on a prototype and gives results in good agreement with experimentally observed belt life time.

In modern turbocharged internal combustion engines the cooling of the air after the compression stage is the standard technique to reduce temperature of the engine intake air aimed at improving cylinder filling (volumetric efficiency) and, therefore, overall global efficiency. At present, standard values for the intake air temperature are in the range 30-70°C, dependently on engine load, external air conditions and vehicle speed and the adoption of a dedicated cooling fluid operating at low temperatures (-10-0°C) is addressed as the most viable option to achieve an effective temperature reduction. This paper investigates a pilot engine set-up, featuring an evaporator on the intake line of a turbocharged diesel engine, tested on a high speed dynamometer bench: the evaporator was a part of an air refrigeration unit – the same used for cabin cooling - composed also by a compressor, a condenser and a thermostatic expansion valve.

In the last years, the design of internal combustion engines (ICE) has evolved significantly, mainly because of the changing demand of mobility, the need to limit the pollution produced by vehicles, and recently, the opportunity to reduce emissions of climate-altering gases. Among the more interesting technologies, those connected to a revision of the engine cooling, as well as, in general, of the thermal needs on board vehicle (oil cooling, intercooling of the turbocharging air, EGR cooling, cabin conditioning...) appear very promising, also because characterized by a lower cost increase per unit of CO₂ saved. In this paper, the Authors present a mathematical model of an internal combustion engine physically consistent that appraises the performances of conventional and unconventional engine cooling systems and the integration of vehicle thermal needs.

The growing interest on environmental issues related to vehicles is pushing up the research on reciprocating internal combustion engines which seems to be endless and able to insure to combustion engines a long future. Euro standards imposed a significant reduction of pollutant emissions and were the stimulus to favor the conception of technologies which represented real breakthroughs; the recent directives on greenhouse gases emissions further reinforced the concept of reducing fuel consumption and, consequently, carbon dioxide emissions. So, new technological efforts have to be made on internal combustion engines in order to achieve this additional target: several technological options are already available or under studying, but only a few of these are suitable, in particular, in terms of costs attendance per unit of CO2 saved. Among these technologies, a revision of engine cooling system seems to have good potentiality.

To further the knowledge of the unsteady heat transfer in reciprocating Internal Combustion Engines (ICE) it reveals of great interest to deepen the modeling of the thermal interactions between cylinder and piston in motion, to remove the hypothesis of the quasi-steady gas-to-wall heat transfer process and to improve the calculation of the stabilized periodical thermal state. In this paper some observations on these aspects are presented and some procedures to perform deeper analyses are proposed.

In reciprocating IC engines, very precise predictions of the mass of air inducted are required in order to improve both manifold design and fuel injection control. To achieve this goal, a deeper knowledge of the boundary conditions on intake and exhaust manifolds must be obtained, and a set of very accurate experimental data is needed to perform model validation. In this paper an experimental activity is reported, which has been performed on a pipe test-rig which guarantees high reproducibility of the fluid-dynamic transients. Based on the obtained data, the authors validated a modified non-isentropic version of the method of characteristics, specifically conceived for the simulation of varying area engine manifolds.

In literature, particular interest is directed toward procedures allowing for accurate predictions of thermal fields in Internal Combustion Engines (ICE) components facing gases. While the calculation of the steady part is straightforward, the evaluation of the unsteady temperatures is complex, time consuming and still calls for further refinement. The possibility of obtaining these predictions only in single portions of the components (without solving the whole thermal field, but keeping the same accuracy), reveals an even greater interest. In this paper a suggestion for reaching this goal is given. It is based on isolating a portion of the component on which a suitably defined steady calculation were firstly performed.

The paper describes the derivation of a real-time controller for the energy management of a series hybrid city bus. The controller is based on Optimal Control theory and on a control-oriented model of the propulsion system. The model is of the quasi-stationary, backward type, and it is derived from tabulated data of the single components provided by the manufacturers and basic, first-principle equations. The fuel consumption obtained with the optimal controller is compared with that yielded by a conventional controller tracking the battery state-of-charge.

Cooling system design has a crucial role in defining engine performance and operational limits. Many further improvements can be obtained both in the precision in controlling temperatures of the various engine parts (especially during transient operation), and in the energy consumption of the system. Moreover, the warm-up transient can be relevantly reduced producing benefic effects on vehicle emissions and interior conditioning and comfort. Taking the lead by these considerations, the authors developed an integrated model of an engine cooling system, which is characterized by a complete modularity and permits the simulation of any possible design configuration. The model acts as a “virtual engine cooling system”: its coupling with simple ECU models permits an off-line evaluation of the efficiency of new control strategies, model-based too. In this work a novel model for the engine thermal behavior is proposed to be included in the described modeling architecture.

One of the most promising near-future alternatives to traditional gasoline and Diesel Internal Combustion Engines is the utilization of alternative fuels. Among these, Liquefied Petroleum Gases (LPG) play a key role for its wide availability and high energetic density. The adoption of liquid phase injection systems would permit the highest achievable performances from both a traditional (power output, acceleration, …) and an environmental (pollutants and greenhouse emissions) point of view. Those systems, however, still present many unsolved problems, substantially limiting their use. The authors here report the results of an intense research activity aimed to the realization of a model-based A/F controller to be used on-board for liquid-phase LPG injected engines. All the main dynamical phenomena involved were modeled: it was so possible to analyze in detail the efficiency of the system in terms of A/F control (strictly related to pollutant emissions) and power output of the engine.

Hybrid propulsion systems can give an effective contribution to compensate the low on-board energy storage capability of pure electric vehicles. The prediction of the performance of a hybrid thermal-electric vehicle is complex, due to the interaction of several components exchanging different kind of energy among them. A detailed model is required for the components selection, sizing and optimization, as well as for a model based control. This paper describes the theoretical and experimental activities developed at DOE for setting up a Hybrid City Minibus. A preliminary model validation has been carried out with in field data, evidencing the possibility to obtain a fully model based vehicle control.

Literature showed quite clearly that the efficiency of Air to Fuel Ratio (AFR) control for Spark Ignition (SI) Internal Combustion Engines (ICE) strongly depends on its capacity to deal with the fuel-flow phenomena inside intake manifolds. Moreover, engine performances (such as power output, specific fuel consumption, and exhaust gas emissions) are directly related to the efficiency of the combustion process, which, on its turn, can be affected substantially by the air/fuel ratio variations related to the fuel-film dynamics. In this work a comprehensive model-based air/fuel ratio control technique is proposed: this is based on a dynamical model of the air dynamics inside inlet manifolds and on the online identification of the fuel-film parameters. Here the identification procedure is illustrated in detail and validated basing on experimental data regarding a single-cylinder engine.