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Technical Paper

The influence of design operating conditions on engine coolant pump absorption in real driving scenarios.

2024-06-12
2024-37-0015
Reducing CO2 emissions in on-the-road transport is important to limit global warming and follow a green transition towards net zero Carbon by 2050. In a long-term scenario, electrification will be the future of transportation. However, in the mid-term, the priority should be given more strongly to other technological alternatives (e.g., decarbonization of the electrical energy and battery recharging time). In the short- to mid-term, the technological and environmental reinforcement of ICEs could participate in the effort of decarbonization, also matching the need to reduce harmful pollutant emissions, mainly during traveling in urban areas. Engine thermal management represents a viable solution considering its potential benefits and limited implementation costs compared to other technologies. A variable flow coolant pump actuated independently from the crankshaft represents the critical component of a thermal management system.
Technical Paper

Optimization of a Sliding Rotary Vane Pump for Heavy Duty Internal Combustion Engine cooling

2024-06-12
2024-37-0030
The benefits introduced by the replacement of conventional centrifugal pumps with volumetric machines for Internal Combustion Engines (ICEs) cooling were experimentally and theoretically proven in literature. In particular, Sliding Rotary Vane Pumps (SVRPs) ensure to achieve an interesting reduction of ICEs fuel consumption and CO2 emissions. Despite volumetric pumps are a reference technology for ICE lubrication oil circuits, the application in ICE cooling systems still not represent a ready-to-market solution. Particularly challenging is the case of Heavy-Duty ICE due to the wide operating range the pump covers in terms of flow rate delivered. Generally, SVRPs are designed to operate at high speeds to reduce machine dimensions and, consequently, the weight. Nevertheless, speed increase could lead to a severe penalization of pump performance since the growth of the friction losses.
Journal Article

Effects of Ultra-High Injection Pressure and Flash Boiling Onset on GDI Sprays Morphology

2023-04-11
2023-01-0299
Ultra-high injection pressures, as well as flash-boiling occurrence, are among the most important research fields recently explored for improving Gasoline Direct Injection (GDI) engine performance. Both of them play a key role in the enhancement of the air/fuel mixing process, in the reduction of tailpipe pollutant emissions, as well as in the investigation of new combustion concepts. Injector manufacturers are even more producing devices with ultra-high injection pressures capable of working with flashing sprays. Flash-boiling of fuel sprays occurs when a super-heated fuel is discharged into an environment whose pressure is lower than the saturation pressure of the fuel and can dramatically alter spray formation due to complex two-phase flow effects and rapid droplet vaporization. In GDI engines, typically, it occurs during the injection process when high fuel temperatures make its saturation pressures higher than the in-cylinder one.
Journal Article

Model Based Design, Prototyping and Testing of a Small Size High Speed Electrically Driven Centrifugal Pump

2022-06-14
2022-37-0025
Within automotive sector, there are several high-performance applications, like, for instance, those referred to racing and motorsport, where cooling needs are usually fulfilled by simple circuits with conventional low-efficiency pumps. The cooling needs in these applications are represented by low flow rates delivered (in the range of 10 - 50 L/min). The operating conditions of these small pumps are usually characterized by very high revolution speeds, which intrinsically cause low efficiency and critical intake phenomena (cavitation) if the design is not specifically optimized to address these concerns. Hence, in this paper a small-size pump operating in the racing sector has been designed using a model-based approach, built and tested having reached both high efficiency (aimed to 50%) and absence of intake operational problems (cavitation).
Technical Paper

Model-Based Design of Triple-Screw Pump for Automotive Engine Cooling

2022-03-29
2022-01-0186
Fuel saving and, consequently, CO2 emissions reduction are the main driver of internal combustion engine development for the transportation sector. Among the several technological options presently available for this purpose, those related to thermal management and, in particular, engine cooling optimization, seem to have additional value thanks to their easiness to be applied on board, without invasive modification of the engine and the vehicle. Typically, centrifugal pumps are adopted, but their efficiency is highly dependent on their revolution speed, suffering of it during real operation. Volumetric pumps can overcome this issue, having an efficiency ideally independent on rotational speed. In this work, triple-screw pump has been considered as a technological replacement for the centrifugal one, since it is a consolidated technology in other sectors, but never considered in engine cooling.
Technical Paper

Advanced Turbulence Model for SI Combustion in a Heavy-Duty NG Engine

2022-03-29
2022-01-0384
In the recent years, the interest in heavy-duty engines fueled with Compressed Natural Gas (CNG) is increasing due to the necessity to comply with the stringent CO2 limitation imposed by national and international regulations. Indeed, the reduced number of carbon atoms of the NG molecule allows to reduce the CO2 emissions compared to a conventional fuel. The possibility to produce synthetic methane from renewable energy sources, or bio-methane from agricultural biomass and/or animal waste, contributes to support the switch from conventional liquid fuels to CNG. To drive the engine development and reduce the time-to-market, the employment of numerical analysis is mandatory. This requires a continuous improvement of the simulation models toward real predictive analyses able to reduce the experimental R&D efforts. In this framework, 1D numerical codes are fundamental tools for system design, energy management optimization, and so on.
Technical Paper

Supercharged Expander to Enhance Waste Heat Recovery Through ORC-Based Recovery Unit in Vehicle Applications

2021-09-05
2021-24-0092
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.
Technical Paper

Laminar Flame Speed Based Optimization of Efficiency and Emissions for Methane-Hydrogen Fueled SI Micro-Generators

2021-09-05
2021-24-0047
Within the context of environmental impact reduction for small size spark ignition (SI) engines, especially green-house gas emissions, this study looked at laminar flame speed as an optimization parameter for hydrogen-methane fueled micro-generators. To this aim, SI engine operation was modeled in a 0D/1D simulation framework, so as to identify the best choice of methane-hydrogen ratios in different conditions. Starting from experimental data recorded on a small size engine, an optimization method was implemented for achieving the proposed goal. One of the main conclusions is that high concentrations of hydrogen and resulting fast burn rates are beneficial at high engine speed settings, while the opposite is true at low engine speed. Hydrogen addition was also considered as an additional control margin during lean operation, given that stable combustion can be achieved even with very low equivalence ratios.
Technical Paper

Experimental and Numerical Investigation of a Lean SI Engine To Be Operated as Range Extender for Hybrid Powertrains

2021-09-05
2021-24-0005
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.
Technical Paper

Numerical Investigation of Water Injection Effects on Flame Wrinkling and Combustion Development in a GDI Spark Ignition Optical Engine

2021-04-06
2021-01-0465
The new real driving emission cycles and the growing adoption of turbocharged GDI engines are directing the automotive technology towards the use of innovative solutions aimed at reducing environmental impact and increasing engine efficiency. Water injection is a solution that has received particular attention in recent years, because it allows to achieve fuel savings while meeting the most stringent emissions regulations. Water is able to reduce the temperature of the gases inside the cylinder, coupled with the beneficial effect of preventing knock occurrences. Moreover, water dilutes combustion, and varies the specific heat ratio of the working fluid; this allows the use of higher compression ratios, with more advanced and optimal spark timing, as well as eliminating the need of fuel enrichment at high load. Computational fluid dynamics simulations are a powerful tool to provide more in-depth details on the thermo-fluid dynamics involved in engine operations with water injection.
Technical Paper

CFD Numerical Reconstruction of the Flash Boiling Gasoline Spray Morphology

2020-09-27
2020-24-0010
The numerical reconstruction of the liquid jet generated by a multi-hole injector, operating in flash-boiling conditions, has been developed by means of a Eulerian- Lagrangian CFD code and validated thanks to experimental data collected with schlieren and Mie scattering imaging techniques. The model has been tested with different injection parameters in order to recreate various possible engine thermodynamic conditions. The work carried out is framed in the growing interest present around the gasoline direct-injection systems (GDI). Such technology has been recognized as an effective way to achieve better engine performance and reduced pollutant emissions. High-pressure injectors operating in flashing conditions are demonstrating many advantages in the applications for GDI engines providing a better fuel atomization, a better mixing with the air, a consequent more efficient combustion and, finally, reduced tailpipe emissions.
Technical Paper

Turbulent Jet Ignition Effect on Exhaust Emission and Efficiency of a SI Small Engine Fueled with Methane and Gasoline

2020-09-27
2020-24-0013
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.
Technical Paper

Toward Predictive Combustion Modeling of CNG SI Engines in 1D Simulation Tools

2020-09-15
2020-01-2079
In the recent years, the interest in heavy-duty engines fueled with Compressed Natural Gas (CNG) is increasing due to the necessity to comply with the stringent CO2 limitation imposed by national and international regulations. Indeed, the reduced number of carbon atoms of the NG molecule allows to reduce the CO2 emissions compared to a conventional fuel. The possibility to produce synthetic methane from renewable energy sources, or bio-methane from agricultural biomass and/or animal waste, contributes to support the switch from conventional fuel to CNG. To drive the engine development and reduce the time-to-market, the employment of numerical analysis is mandatory. This requires a continuous improvement of the simulation models toward real predictive analyses able to reduce the experimental R&D efforts. In this framework, 1D numerical codes are fundamental tools for system design, energy management optimization, and so on.
Technical Paper

Numerical Investigation on GDI Spray under High Injection Pressure up to 100 MPa

2020-09-15
2020-01-2108
In recent years, the increase of gasoline fuel injection pressure is a way to improve thermal efficiency and lower engine-out emissions in GDI homogenous combustion concept. The challenge of controlling particulate formation as well in mass and number concentrations imposed by emissions regulations can be pursued improving the mixture preparation process and avoiding mixture inhomogeneity with ultra-high injection pressure values up to 100 MPa. The increase of the fuel injection pressure in GDI homogeneous systems meets the demand for increased injector static flow, while simultaneously improves the spray atomization and mixing characteristics with consequent better combustion performance. Few studies quantify the effects of high injection pressure on transient gasoline spray evolution. The aim of this work was to simulate with OpenFOAM the spray morphology of a commercial gasoline injected in a constant volume vessel by a prototypal GDI injector.
Technical Paper

Modeling of Soot Deposition and Active Regeneration in Wall-flow DPF and Experimental Validation

2020-09-15
2020-01-2180
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.
Technical Paper

A Novel Option for Direct Waste Heat Recovery from Exhaust Gases of Internal Combustion Engines

2020-06-30
2020-37-0004
Among the different opportunities to save fuel and reduce CO2 emissions from internal combustion engines, great attention has been done on the waste heat recovery: the energy wasted is, in fact, almost two thirds of the energy input and even a partial recovery into mechanical energy is promising. Usually, thermal energy recovery has been referred to a direct heat recovery (furtherly expanding the gases expelled by the engine thanks to their high pressure and temperature) or an indirect one (using the thermal energy of the exhaust gases - or of any other thermal streams - as upper source of a conversion power unit, which favors a thermodynamic cycle of a suitable working organic fluid).
Technical Paper

A Power Split Hybrid Propulsion System for Vehicles with Gearbox

2020-06-30
2020-37-0014
New internal combustion engines (ICE) are characterized by increasing maximum efficiency, thanks to the adoption of strategies like Atkinson cycle, downsizing, cylinder deactivation, waste heat recovery and so on. However, the best performance is confined to a limited portion of the engine map. Moreover, electric driving in urban areas is an increasingly pressing request, but battery electric vehicles use cannot be easily spread, due to limited vehicle autonomy and recharging issues. Therefore, hybrid propulsion systems are under development, in order to reduce vehicle fuel consumption, by decoupling the ICE running from road load, as well as to permit energy recovery and electric driving. This paper analyses a new-patented solution for power split hybrid propulsion system with gearbox. The system comprises an auxiliary power unit, adapted to store and/or release energy, and a planetary gear set, which is interposed between the ICE and the gearbox.
Technical Paper

Analysis of the Combustion Process of SI Engines Equipped with Non-Conventional Ignition System Architecture

2020-06-30
2020-37-0035
The use of lean or ultra-lean ratios is an efficient and proven strategy to reduce fuel consumption and pollutant emissions. However, the lower fuel concentration in the cylinder hinders the mixture ignition, requiring greater energy to start the combustion. The prechamber is an efficient method to provide high energy favoring the ignition process. It presents the potential to reduce the emission levels and the fuel consumption, operating with lean burn mixtures and expressive combustion stability. In this paper the analysis of the combustion process of SI engines equipped with an innovative architecture and operating in different injection modes was described. In particular, the effect of the prechamber ignition on the engine stability and the efficiency was investigated in stoichiometric and lean-burn operation conditions. The activity was carried out in two parts.
Journal Article

Experimental Study of Additive-Manufacturing-Enabled Innovative Diesel Combustion Bowl Features for Achieving Ultra-Low Emissions and High Efficiency

2020-06-30
2020-37-0003
In recent years the research on Diesel engines has been increasingly shifting from performance and refinement to ultra-low emissions and efficiency. In fact, the last two attributes are key for the powertrain competitiveness in the propulsion electrified future, especially in the European market where 95gCO2/km fleet average and Euro6D RDE Step2 are phasing in at the same time. The present paper describes some of the most innovative research that GM and Istituto Motori Napoli are performing in the field, exploring how the steel-based additive manufacturing can be used to create innovative combustion bowl features that optimize the combustion process to a level that was not compatible with standard manufacturing technologies.
Technical Paper

Experimental and 1D Numerical Investigations on the Exhaust Emissions of a Small Spark Ignition Engine Considering the Cylinder-by-Cylinder Variability

2020-04-14
2020-01-0578
This paper reports a numerical and experimental analysis on a twin-cylinder turbocharged Spark Ignition engine carried out to investigate the cylinder-to-cylinder variability in terms of performance, combustion evolution and exhaust emissions. The engine was tested at 3000 rpm in 20 different steady-state operating conditions, selected with the purpose of observing the influence of cylinder-by-cylinder A/F ratio variations and the EGR effects on the combustion process and exhaust emissions for low to medium/high loads. The experimental outcomes showed relevant differences in the combustion evolution (characteristic combustion angles) between cylinders and not negligible variations in the emissions of the single cylinder exhaust and the overall engine one. This misalignment resulted to be due to differences in the injected fuel amount by the port injectors in the two cylinders, mainly deriving from the specific fuel rail geometry.
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