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Technical Paper

Transient Phenomena in One-Dimensional Ducts

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.
Technical Paper

Optimization of the Engine Intake Air Temperature through the Air Conditioning Unit

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.
Technical Paper

On-line Identification of Fuel Dynamics for a Model-based Injection 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.
Technical Paper

Inverted Brayton Cycle as an Option for Waste Energy Recovery in Turbocharged Diesel Engine

Energy recovery in reciprocating internal combustion engines (ICE) is one of the most investigated options for the reduction of fuel consumption and GHG emissions saving in the transportation sector. In fact, the energy wasted in ICE is greater than that converted in mechanical form. The contribution associated to the exhaust gases is almost one third of the fuel energy, calling for an urgent need to be recovered into mechanical form. An extensive literature is oriented toward this opportunity, strongly oriented to ORC (Organic Rankine Cycle)-based power units. From a thermodynamic point of view, one option, not extensively explored, is certainly represented by the Inverted Brayton Cycle (IBC) concept and by the corresponding components which make possible this recovery.
Journal Article

Experimental Analysis of an Organic Rankine Cycle Plant Bottoming a Heavy-Duty Engine Using Axial Turbine as Prime Mover

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.
Technical Paper

Engine oil Thermal Management: Oil Sump Volume Modification and Heating by Exhaust Heat During ICE Warm Up

In the perspective of fuel saving and emissions reduction, engine oil thermal management has not yet received the attention it deserves. Lubricating oil, in fact, should be the focus of a specific warmup action: the expected benefits is on friction reduction – mechanical efficiency improvement – but also on a positive interaction with the cooling fluid thermal dynamics. The lower thermal capacity of the circulating oil (with respect to the cooling fluid) and the instantaneous reduction of the viscosity due to temperature increase produces a faster engine overall efficiency benefit: this invites to focus specific actions on its thermal management in the direction of speeding up the temperature rise during a cold engine starting.
Technical Paper

Effects of an ORC Based Heat Recovery System on the Performances of a Diesel Engine

A smart way to reduce CO2 emission in transportation sector is to recover energy usually wasted and re-use it for engine and vehicle needs. ORC plant on exhaust gas of ICE is really interesting, but it has a significant impact on the exhaust line and vehicle's weight. The backpressure realized in the exhaust and the weight gain, in fact, produce a specific fuel consumption increase as well as an increase in the propulsion power: both terms could vanish the energy recovered. The paper discusses the effects of the pressure losses produced by an ORC plant mounted on the exhaust line of an IVECO F1C test bench engine. The interactions produced on the turbocharged engine have been experimentally investigated: the presence of an IGV turbocharger makes the effect of the backpressure not straightforward to be predicted and needed a full experimental testing of the group in order to understand its reaction and the net effect in terms of specific fuel consumption.
Technical Paper

Development of Thermal Modeling in Support of Engine Cooling Design

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.
Technical Paper

Control-Oriented Modeling and Fuel Optimal Control of a Series Hybrid Bus

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.
Technical Paper

A/F and Liquid-Phase Control in LPG Injected Spark Ignition ICE

Many advantages are related to the use of LPG as fuel in SI injected ICE. Most of them regard the lower environmental impact with respect to gasoline. The liquid-phase injection is one of the most important aspects of these engines, being able to guarantee the maintenance (and even an increase) of the more traditional engine performances (power, acceleration, driveability, etc) and to match the 3-way catalytic converter A/F specifications. In this paper the transient phenomena occurring in an LPG injection system have been studied, focusing the attention on the problems related to A/F and liquid-phase control.
Technical Paper

A Theoretical and Experimental Activity on the Dynamical Behavior of ICE Varying Area Manifolds

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.
Technical Paper

A New Modeling to Predict the Fluid Dynamic Transient Phenomena in Ice Ducts

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.
Journal Article

A Model Approach to the Sizing of an ORC Unit for WHR in Transportation Sector

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.