bluuebunny/crossref_metadata_2025 huggingface dataset:
A Predictive 1D Modeling Framework for Reactivity-Controlled Compression Ignition Engines, via a Chemistry-Based, Multizone Combustion Object
Authors: Kakoee Alireza , Vasudev Aneesh , Smulter Ben , Hyvonen Jari , Mikulski Maciej
Published: August 2023

Chemical-kinetics-based multizone models (MZM) are effective tools for performance-oriented simulations of low-temperature combustion concepts. It demonstrates a better trade-off between simulation speed and predictivity than both high-fidelity computational fluid dynamics (CFD) and low-fidelity data-driven models. This study applies a newly developed MZM, referred to as UVATZ, to simulate reactivity-controlled compression ignition (RCCI) combustion, fueled by natural gas (NG) and diesel. In such a concept, in-cylinder conditions at intake valve closing (IVC) largely define the kinetically dominated combustion predictions. To secure IVC predictions accurately, UVATZ is for the first time coupled with a detailed air/fuel path dynamics model created in commercial engine modeling software (GT-Suite), forming a 1D simulation framework. The direct coupling enables information exchange of initial and boundary conditions between the two models including IVC and EVO thermodynamic state, wall temperature boundary conditions, residual gas fraction, and composition. The closed part of the engine cycle is simulated using UVATZ, which has a representative zone arrangement for reactivity stratification, predictive interzonal mixing. A kinetic mechanism with 54 species and 269 reactions for combustion and emissions. The coupled model is calibrated and validated using experimental data from a single-cylinder research engine, representing the commercial Wärtsilä 31DF series marine, mid-speed engines. Model validation is performed against a selection of six test cases covering fully-premixed RCCI calibration. The results prove good conformance to in-cylinder and airpath pressure signals, and performance quantifiers within 2% error to measurements. Use of a detailed 1D airpath approach over the commonly used 0D plenum models is also justified from the perspective of chemical kinetics based LTC simulations.
Turbocharging Automotive Engines: A Decision-Making Approach for Optimal Turbocharger Selection
Authors: Amine ELHAMEUR Mohamed , Mahfoudh Cerdoun , Tarabet Lyes , Gimelli Alfredo , Ferrara Giovanni
Published: August 2023

An approach for turbocharging automotive engines to reach targeted performance was developed in which the environmental and economic aspects during the turbocharger-engine matching process were considered. Three numerical assessment levels based on output performance, exhaust emissions and techno-economic metrics are established to support users during the decision-making of adequate turbochargers that meets targeted data in terms of boosting and emissions. Satisfactory improvements are measured from a 1.5L, three-cylinders, turbocharged Diesel engine, in terms of brake specific fuel consumption, thermal efficiency and NOx concentrations of about 1.73% (decrease in fuel consumption of around 2.22ml/s), 1.76%, and 4.53% (correspond to a diminution of around 217.54ppm), respectively, at the engine’s extreme conditions (full load and rated power). In addition, for an application of another turbocharger, remarkable improvements in terms of HC and CO concentrations of about 6.23% (reduction of 41.167ppm), and 2.61% (diminution of around 1.271ppm), respectively, were found at the same engine’s extreme conditions. Furthermore, the superimposition of the engine operating area on compressor and turbine maps of all tested turbochargers ensured a secure functioning of the proposed compressor, reasonable mechanical and thermal loads of the in-cylinder chamber, and practical turbine inlet temperature at the engine’s extreme operations. Consequently, the enhanced methodology is considered a promising and helpful decision-support method that can be followed by researchers during the engine turbocharging process at both the earlier and last stages providing powerful and clean mobility of the vehicle.
Predictive 3D-CFD Model for the Analysis of the Development of Soot Deposition Layer on Sensor Surfaces
Authors: D'Orrico Fabrizio , Cicalese Giuseppe , Breda Sebastiano , Fontanesi Stefano , Cozza Ivan , Tosi Sergio , Gopalakrishnan Venkatesh
Published: August 2023

After-treatment sensors are used in the ECU feedback control to calibrate the engine operating parameters. Due to their contact with exhaust gases, especially NOx sensors are prone to soot deposition with a consequent decay of their performance. Several phenomena occur at the same time leading to sensor contamination: thermophoresis, unburnt hydrocarbons condensation and eddy diffusion of submicron particles. Conversely, soot combustion and shear forces may act in reducing soot deposition. This study proposes a predictive 3D-CFD model for the analysis of the development of soot deposition layer on the sensor surfaces. Alongside with the implementation of deposit and removal mechanisms, the effects on both thermal properties and shape of the surfaces are taken in account. The latter leads to obtain a more accurate and complete modelling of the phenomenon influencing the sensor overall performance. The evolution of the fouling thickness is evaluated by means of the implementation of a morphing and remesh procedure based on the local conditions of both the flow and the pollutant concentration. The proposed model was tested on actual sensors by means of accelerated contamination cycles. The sensor behavior was correlated to the experimental response time to account for the decay of performance due to fouling accumulation. The response time is calculated both in the middle of the contamination cycle and at its end. Comparing the experimental data with the CFD results an error lower than the 9% is obtained.
Application of a Machine Learning Approach for Selective Catalyst Reduction Catalyst 3D-CFD Modeling: Numerical Method Development and Experimental Validation
Authors: Cozza Ivan Flaminio , Centini Maria Pia , Sapio Francesco , Gopalakrishnan Venkatesh , Buitoni Giacomo , Tabarrini Marco
Published: August 2023

Internal combustion engines (ICEs) exhaust emissions, particularly nitrogen oxides (NOx), have become a growing environmental and health concern. The biggest challenge for contemporary ICE industry is the development of clean ICEs, and the use of advanced design tools like Computational Fluid Dynamics (CFD) simulation is paramount to achieve this goal. In particular, the development of aftertreatment systems like Selective Catalyst Reduction (SCR) is a key step to reduce NOx emissions, and accurate and efficient CFD models are essential for its design and optimization. In this work, we propose a novel 3D-CFD methodology, which uses a Machine Learning (ML) approach as a surrogate model for the SCR catalyst chemistry, which aims to enhance accuracy of the simulations with a moderate computational cost. The ML approach is trained on a dataset generated from a set of 1D-CFD simulations of a single channel of an SCR catalyst. The trained model is then applied to the 3D-CFD simulation as a surrogate model for the SCR chemistry, allowing the calculation of the spatial distribution of chemical species at the catalyst’s outlet. The model is finally applied to the calculation of the SCR conversion efficiency and to the simulation of NOx sensors reading on the tailpipe. Experimental validation of the developed 3D-CFD models was performed on a dedicated test bench. An ad-hoc local sampling probe has been used to measure the spatial distribution of the chemical species downstream the SCR system, together with the reading of three commercial NOx sensors. Our findings suggest that the ML-based surrogate model for the SCR is a reliable and efficient methodology for including the SCR chemistry in a 3D-CFD simulation at a moderate computational cost. The developed numerical method could provide valuable insights into the SCR catalyst’s design and optimization and aid in the development of ultra-low NOx emission ICEs.
Energy Management System of Fuel Cell Electric Vehicles Based on Stochastic Model Predictive Control and Markov Chains
Authors: Alfieri Vincenzo , Binetti Giulio , Ruotolo Romualdo , Gandino Edoardo
Published: August 2023

In the mobility industry, Fuel Cell Electric Vehicle (FCEV) combines fuel cell technology with batteries, allowing to overcome some limitations of Battery Electric Vehicles (BEVs), such as the high recharging time and the high battery mass for applications requiring a high amount of energy (e.g., bus and heavy-duty vehicles). FCEVs have the possibility to collect several information from Intelligent Transportation Systems (ITSs) with relevant potential for vehicle efficiency improvement. Indeed, an online vehicle speed prediction inherently considering real-life factors such as traffic flow, driving path and driving style, allows for novel designs of Energy Management Systems (EMSs) for the optimal operations of the hybrid propulsion system.

In such context, this paper proposes an EMS based on Stochastic Model Predictive Control with Learning (SMPCL) to optimize the hydrogen consumption of a Fuel Cell Electric Vehicle (FCEV), while guaranteeing the fulfillment of constraints on battery state of charge (SOC) and available power ranges, as well as maximizing the lifetime of fuel cell and battery. The proposed approach combines a scenario-based Stochastic Model Predictive Control (SMPC) for the propulsion system optimization with novel fuzzy Markov Chains (MCs) for short-term vehicle speed prediction. The effectiveness of this approach has been evaluated considering real driving speed acquisitions of a city bus operating in Turin (Italy) in different traffic flows and with different drivers. For comparison, several algorithms have been applied to a high-fidelity simulation plant representative of the FCEV propulsion system developed in GT-SUITE. The results show that SMPCL allows for relevant reduction of hydrogen consumption compared to classic rule-based approach, while getting also important benefits in terms of fuel cell and battery lifetimes. Moreover, hydrogen consumption is very close to the results of a global offline optimization algorithm used as benchmark (i.e., Dynamic Programming). Finally, next steps will include experimental validation of proposed approach on a real propulsion system in a test bench located in Turin (Italy).
Experimental Investigation of Ion Formation for Auto-Ignition Combustion in a High-Temperature and High-Pressure Combustion Vessel
Authors: Golc Dominik , Esposito Stefania , Pitsch Heinz , Beeckmann Joachim
Published: August 2023

One of the main challenges in internal combustion engine design is the simultaneous reduction of all engine pollutants like carbon monoxide (CO), total unburned hydrocarbons (THC), nitrogen oxides (NOx), and soot. Low-temperature combustion (LTC) concepts for compression ignition (CI) engines, e.g., premixed charged compression ignition (PCCI), make use of pre-injections to create a partially homogenous mixture and achieve an emission reduction. However, they present challenges in the combustion control, with the usage of in-cylinder pressure sensors as feedback signal is insufficient to control heat release and pollutant emissions simultaneously. Thus, an additional sensor, such as an ion-current sensor, could provide further information on the combustion process and effectively enable clean and efficient PCCI operation. This study performed experiments in a high-temperature, high-pressure, constant-flow combustion vessel to verify the ion-current application for premixed charge compression ignition (PCCI) engine control approaches. In this vessel, a metallic plate has been installed with a 40° orientation in front of the injector. A positively charged ion-current probe has been positioned close to the plate in the region where the fuel is injected. The electrons formed in the combustion process are drained to the probe because of the generated electrical field between the probe and the plate. The number of electrons is quantified as an ion-current signal. N-dodecane, representing a single-component surrogate fuel, has been used in the measurements to facilitate model validation. Additionally, diesel and a corresponding surrogate fuel formulation for diesel fuel have been investigated to validate the concept for a more complex fuel. The ion-current signal is measured at various conditions. These ion-current measurements will then serve as validation targets to correlate the combustion process with pollutant formation. Additionally, the local inhomogeneity of the mixture around the ion-current sensor head is analyzed regarding its impact on the measured ion-current signal. The results show promising evidence that ion-current sensors can control PCCI.
Development of a 5-Component Diesel Surrogate Chemical Kinetic Mechanism Coupled with a Semi-Detailed Soot Model with Application to Engine Combustion and Emissions Modeling
Authors: Yang Shiyou , Yang Ruicheng
Published: August 2023

In the present work, five surrogate components (n-Hexadecane, n-Tetradecane, Heptamethylnonane, Decalin, 1-Methylnaphthalene) are proposed to represent liquid phase of diesel fuel, and another different five surrogate components (n-Decane, n-Heptane, iso-Octane, MCH (methylcyclohexane), Toluene) are proposed to represent vapor phase of diesel fuel. For the vapor phase, a 5-component surrogate chemical kinetic mechanism has been developed and validated. In the mechanism, a recently updated H2/O2/CO/C1 detailed sub-mechanism is adopted for accurately predicting the laminar flame speeds over a wide range of operating conditions, also a recently updated C2-C3 detailed sub-mechanism is used due to its potential benefit on accurate flame propagation simulation. For each of the five diesel vapor surrogate components, a skeletal sub-mechanism, which determines the simulation of ignition delay times, is constructed for species C4-Cn. The five skeletal sub-mechanisms are coupled with the new C2-C3 and H2/O2/CO/C1 detailed sub-mechanisms. In order to simulate soot, a semi-detailed soot model is coupled with the 5-component diesel vapor surrogate chemical kinetic mechanism. Together with a reduced NOx (oxides of nitrogen) sub-mechanism, the final version of the diesel mechanism has 119 species and 488 reactions, which are feasible currently for simulating diesel engine combustion and emissions. The reaction rate constants of the five skeletal sub-mechanisms were optimized in this work to match available experimental data of either pure fuels or fuel blends, including ignition delay times, laminar flame speeds, and important species profiles in the literature. Using the new models developed in this work, simulations of the combustion and emissions of several diesel engines under typical operating conditions were carried out. The simulated in-cylinder pressures and emissions including unburned hydrocarbons, nitrogen oxides, carbon monoxide, and soot were compared with the experimental data, showing good agreements between simulations and experiments.
Evaluation of Different Gasoline Formulations on a High-Performance Engine
Authors: Graßmeyer Marius , Atzler Frank
Published: August 2023

The future of the combustion engine will to some extent depend on the use of CO2-neutral eFuels to avoid further fossil CO2 emissions. Also, the use of synthetic fuels offers the possibility to improve various engine properties, such as thermodynamics, EGR compatibility or emissions, through targeted influence on specific fuel properties. To this end, a methodology was generated to attribute various engine effects to particular fuel properties. Therefore, the Chair of Combustion Engines (LVAS) at the TU Dresden developed a fully automated testbed for motorcycle engines, including clutch and gear switching mechanisms. Hitherto, emissions measurements for motorcycles were done mostly on chassis dynamometers, with the disadvantage of a large spread of results. Due to the lack of consistency the analysis of fuel properties was not possible. To prove the developed methodology, a test campaign including 15 different gasoline fuels was elaborated in cooperation with KTM R&D GmbH. Before measuring over 200 WTMC cycles on this new engine test stand, a fast conditioning system was devised for the coolant, engine oil and catalyst. This allows for cycle times of just over an hour with subsequent cold start. The experiments demonstrate the detailed effects of the fuel on engine behaviour. The highly dynamic engine test stand showed a much better reproducibility and a massively decreased test interval, compared to the conventional dyno testing. During the evaluation of engine measurement data, differences between fuels were established regarding various characteristics. These include starting behaviour, CO2 emissions and fuel consumption in correlation with varying C-H-O ratios, CO and NOx as well as particle emissions. Recommendations for future engine application and adaptation for synthetic fuels can be drawn from the findings.
Optical Diagnostic Study on Improving Performance and Emission in Heavy-Duty Diesel Engines Using a Wave-Shaped Piston Bowl Geometry and Post Injection Strategies
Authors: Gong Miaoxin , Derafshzan Saeed , Richter Mattias , Hemdal Stina , Eismark Jan , Andersson Oivind , Lundgren Marcus
Published: August 2023

This study explores the potential benefits of combining a wave-shaped piston geometry with post injection strategy in diesel engines. The wave piston design features evenly spaced protrusions around the piston bowl, which improve fuel-air mixing and combustion efficiency. The 'waves' direct the flames towards the bowl center, recirculating them and utilizing the momentum in the flame jets for more complete combustion. Post injection strategy, which involves a short injection after the main injection, is commonly used to reduce emissions and improve fuel efficiency. By combining post injections with the wave piston design, additional fuel injection can increase the momentum utilized by the flame jets, potentially further improving combustion efficiency. To understand the effects and potential of the wave piston design with post injection strategy, a single-cylinder heavy-duty compression-ignition optical engine with a quartz piston is used. The piston bowl is modified to remove waves on one side, allowing for a direct comparison between the wave and non-wave piston designs under identical engine operating conditions. Natural Luminosity is used as an optical diagnostic technique to visualize flame-piston and flame-flame interactions. The engine is operated under mid-load conditions (~9 bar IMEP) with different post injection strategies. The study provides insights into the potential benefits of combining the wave piston design with post injection strategy for improving combustion efficiency and engine performance in heavy-duty diesel engines.
Study of Higher Alcohol Potential as a Drop-In Fuel for a High Thermal Efficiency Heavy-Duty Diesel Engine
Authors: Uchida Noboru , Kawaharazuka Fumihiro
Published: August 2023

To reduce carbon dioxide (CO2) emissions from heavy-duty diesel engines down to zero until 2050, alternative powertrain strategies have been proposed in lieu of the improvements in internal combustion engines (ICEs). However, total amount of renewable electricity could be limited for the constructing infrastructure, the production of new battery and/or fuel cell vehicles and the operation of them compared with the growing demand of transportation in the future. Therefore, drastic improvement in transport efficiency with suppressing the increase of total CO2 emissions is essential. From these points of view, extremely high efficiency ICEs, combined or at least compatible with carbon neutral or renewable fuels having the capability of drop-in into the conventional fuels, should be attracted attention. Nevertheless, there have been few studies on the effects of fuel properties for further improving fuel consumption of diesel ICEs. This study focused on the prerequisite fuel properties for the high efficiency diesel engines which we have been developing. Since the compression ratio of the engine is much higher than that of conventional engines, in-cylinder temperature and density are quite high and cavity volume is very small. In such severe conditions, engine performance and exhaust emissions by fueling conventional diesel fuel were deteriorated by the poor mixture formation, whereas 1-octanol of 50vol% mixing diesel fuel achieved significant improvements in both NOx-soot trade-offs and thermal efficiency and much lower cooling loss under higher compression ratio without any engine optimizations dedicated to the fuel.
Experimental Investigation on a DI Diesel Engine Fuelled with Diesel-Like Fuel Obtained by Waste Lubricant Oil Pyrolysis
Authors: Tarabet Lyes
Published: August 2023

In the last decades, waste lubricating oil (WLO) has attracted a great attention due to its strong effect on the environment degradation. Due to the high content of hydrocarbons in the WLO, these huge quantities could be interesting for recovery as a fuel for internal combustion engines. In the present work, an experimental study is conducted on a DI diesel engine operating with a diesel-like fuel (DLF) obtained by converting WLO via a catalytic pyrolysis process. The DLF physicochemical properties have shown a good agreement with those of diesel fuel, except for the viscosity which is slightly higher than that the values recommended by the international standards. For the engine tests, a single cylinder DI diesel engine, operating at a constant speed (1500 rpm) and under various engine load conditions, is fuelled with either DLF or its blends supplemented with various diesel fuel ratios (10, 20 and 30 % by volume). The combustion parameters, engine performance and its exhaust emissions are evaluated. The results show that all tested fuel present a significant improvements in the exhaust emissions accompanied with an equivalent performance to those of diesel fuel.
Experimental and 3D-CFD Analysis of Synthetic Fuel Properties on Combustion and Exhaust Gas Emission Characteristics in Heavy-Duty Diesel Engines
Authors: Shimizu Kunihiro , Narushima Tomoki , Sok Ratnak , Kusaka Jin
Published: August 2023

Synthetic fuels can significantly improve the combustion and emission characteristics of heavy-duty diesel engines toward decarbonizing heavy-duty propulsion systems. This work analyzes the effects of engine operating conditions and synthetic fuel properties on spray, combustion, and emissions (soot, NOx) using a supercharging single-cylinder engine experiment and KIVA-4 code combined with CHEMKIN-II and in-house phenomenological soot model. The blended fuel ratio is fixed at 80% diesel and 20% n-paraffin by volume (hereafter DP). Diesel, DP1 (diesel with n-pentane C5H12), DP2 (diesel with n-hexane C6H14), and DP3 (diesel with n-heptane C7H16) are used in engine-like-condition constant volume chamber (CVC) and engine experiments.

Boosted engine experiments (1080 rpm, common-rail injection pressure 160 MPa, multi-pulse injection) are performed using the same DP fuel groups under various main injection timings, pulse-injection intervals, and EGR = 0-40%. Once the 3D-CFD model is validated with the CVC and experimental engine data, in-cylinder combustion and emissions are analyzed. The CVC experiments show that DP2 and DP3 liquid penetrations are shorter than diesel oil. In engine tests, NOx did not change much for all DP fuels for the same engine operating condition. However, shorter-penetrated DP2 and DP3 reduce soot emissions by more than 60% and CO without worsening brake-specific fuel consumption compared to diesel oil. The 3D-CFD results show that n-hexane shifts the penetration of the high-carbon number to the low-carbon fuel. Vapor penetrations are found to be shortened by blending low-volatility fuels with diesel oil. Visualizations of the in-cylinder confirmed a decrease in the amount of soot formation near the wall for DP2 and DP3 fuels. In addition, equivalence ratio – temperature (phi-T) maps of these fuels indicate that at 40% EGR, soot emissions are reduced at lower equivalence ratios than diesel oil.
Experimental Analysis of a Single-Cylinder Large Bore Engine with External Supercharging in Diesel/CNG Dual-Fuel Mode
Authors: De Simio Luigi , Iannaccone Sabato , Pennino Vincenzo , Marchitto Luca
Published: August 2023

The need for a quick reduction in greenhouse gasses and noxious emissions is pushing maritime transportation to increase the use of alternative fuels. Natural Gas (NG) is well recognized as an effective solution to limit the use of marine diesel oil in the short/mid-term. In this scenario, dual-fuel technology is used to enable a conventional diesel engine to operate with a share of gaseous fuel while retaining the capability to run in full diesel mode. Dual-fuel (DF) engines allow the use of natural gas, or biomethane from renewable sources, as the main fuel, with advantages over CO2, SOx and PM emissions with the same levels of NOx.

This paper presents an experimental study investigating the effects of the diesel injection strategy on performance and emissions of a dual-fuel, single-cylinder, large bore, 4-stroke engine for marine applications. The engine is equipped with an external supercharging system; NG is injected in the port, while a Common Rail system injects the diesel pilot. Measurements were performed at 1500 rpm speed and Brake Mean Effective Pressure (BMEP) of 8.4 bar: the full diesel engine point representative of commercial Electronic Control Unit (ECU) map is chosen as reference. Further investigations will be performed to estimate the influence of dual-fuel combustion on the loss linked to the external supercharging. The performance of an externally supercharged and a turbocharged engine may differ: when working with turbocharged engines, boost and exhaust backpressure simultaneously increase. In contrast, when reproducing external supercharging behavior, an increase in the exhaust backpressure could alter the internal exhaust gas recycling and energy balances.
Thermodynamics of Lean Hydrogen Combustion by Virtual Investigations on a Single-Cylinder Engine with Port Fuel Injection and Pre-Chamber Ignition
Authors: Gal Thomas , Vacca Antonino , Chiodi Marco , Schmelcher Robin , Kulzer Andre , Bucherer Sebastian , Rothe Paul , Sobek Florian , Gottwald Theo , Kraljevic Ivica
Published: August 2023

In order to achieve the climate targets, a mix of different powertrain technologies must be pursued to effectively reduce emissions. By producing hydrogen based on renewable energy sources, it becomes a reasonable choice for fueling internal combustion engines. The specific molecular properties of hydrogen thereby open up new possibilities for favorably influencing the combustion process of engines. The present paper deals with the analysis of a single-cylinder engine with passive pre-chamber ignition and a port fuel injection system, which was adapted for lean hydrogen operation. In this way, the test unit was operated in various load and speed ranges with lambda values from 1.5 to 2.5 and achieved up to 23 bar indicated mean effective pressure. The focus of this work is on the numerical investigation of the hydrogen combustion and its effects on the engine system. Special attention is hereby paid to the influence of different lambda operations. Simulations were carried out to evaluate the heat transfer towards the cooling system and to determine energy losses dependent on the gas temperatures. The validated 3D-CFD simulation illustrates the thermodynamic properties, as well as the interaction of injection strategies and mixture formation inside the cylinder and pre-chamber. The analysis points out that lean operation across all loads is advantageous in terms of indicated efficiency and particularly in lower loads up to 6 %-pts can be achieved by applying a de-throttling strategy. By going beyond test bench limitations, the virtual environment shows that the engine is knock-limited with lambda 1.5 and increased combustion temperatures imply high NOx emissions at high loads. In contrast, with lambda 2.5, the pressure gradient and turbulence level decrease sharply, so that a boost pressure of 4.5 bar is required to achieve the maximum load with a peak cylinder pressure of 180 bar.
CFD Analysis of the Injection Strategy of a Dual Fuel Compression Ignition Engine Supplied with Hydrogen
Authors: De Robbio Roberta , Cameretti Maria Cristina , Palomba Marco , Tuccillo Raffaele , Mancaruso Ezio
Published: August 2023

Although in the latest years the use of compression ignition engines has been a thread of discussion in the automotive field, it is possible to affirm that it still will be a fundamental producer of mechanical power in other sectors, such as naval and off-road applications. However, the necessity of reducing emissions requires to keep on studying new solutions for this kind of engine. Dual fuel combustion concept with methane has demonstrated to be effective in preserving the performance of the original engine and reducing soot, but issues related to the low flame speed forced researcher to find an alternative fuel at low impact of CO2. Hydrogen, thanks to its chemical and physical properties, can be a perfect candidate to ensure a good level of combustion efficiency; however, this is possible only with a proper management of the in-cylinder mixture ignition by means of a pilot injection, preventing uncontrolled autoignition events as well. Moreover, an effective injection strategy can be beneficial for a further reduction of carbonous pollutants from the diesel fuel pilot. Therefore, this work is aimed to numerically analyze the sensitivity of the combustion development in a diesel engine converted to operate in dual fuel mode, where hydrogen is injected in the intake manifold and diesel pilot is directly injected in the cylinder. Starting from a test case at a constant engine speed of 2000 rpm experimentally validated, numerical simulations are carried out with the software ANSYS Forte, using a Turbulence-Kinetics interaction model and the Autoinduced Ignition Flame Propagation model for diesel and hydrogen, respectively. Lookup tables were specifically implemented for the evaluation of the laminar flame speed through H2/air mixtures.
Conversion of a Small Size Passenger Car to Hydrogen Fueling: Focus on Vehicle Dynamics and ECU Remapping Requirements
Authors: Martinez Santiago , Merola Simona , Curto Pedro , Vaglieco Bianca Maria , Irimescu Adrian
Published: August 2023

Converting spark ignition (SI) engines to H2 fueling is an attractive route for achieving zero carbon transportation and solving the legacy fleet problem in a future scenario in which electric powertrains will dominate. The current paper looks at a small size passenger car in terms of vehicle dynamics and electronic control unit (ECU) remapping requirements, in the hypothesis of using H2 as a gasoline replacement. One major issue with the use of H2 in port fuel injection (PFI) engines is that it causes reduced volumetric efficiency and thus low power. The vehicle considered for the study features turbocharging and therefore complete or partial recuperation of lost power is possible. Other specific requirements such as injection phasing were also under scrutiny, especially as PFI was hypothesized to maximize cost effectiveness. A 0D/1D model was used for simulating engine running characteristics as well as vehicle dynamics. One of the main conclusions is that at low rpm there should be only a minor influence on vehicle dynamics, while at the higher end completely comparable performance is achievable. In terms of acceleration, the small passenger car considered for the study loses around 10% performance between 0-100 km/h, but it is possible to have same dynamic response when accelerating from 70-120 km/h. After optimizing the gear shift strategy, the energy consumption between gasoline and H2 version are the same, with zero tailpipe CO2 emissions for the hydrogen.
Influence of the Injection Timing on the Mixture Formation Process in a Spark-Ignition Hydrogen Fuelled ICE
Authors: Anaclerio Giuseppe , Capurso Tommaso , Torresi Marco , Camporeale Sergio
Published: August 2023

In the context of reducing carbon-dioxide (CO2) emissions, the increasing exploitation of renewable sources is expected to improve the availability of green hydrogen, which can be considered a valid alternative to gasoline and diesel fuels in the mobility sector (particularly for long-haul and heavy-duty missions).

The air-hydrogen mixing plays a significant role, particularly in direct-injection spark-ignition engines. As a matter of fact, the onset of zones featuring an equivalence ratio greater than 0.5 should be avoided, since this would lead to an increased risk of self-ignition and NOx production. The presence of wide ultra-lean volumes (over the lean flammability limit) due to imperfect mixing is negative too, yielding to irregular combustion. Therefore, the calibration of the direct injection timing is a crucial task.

In this work, the authors numerically explore the influence of the injection timing, for a fixed total amount of fuel (global equivalence ratio equal to 0.25), on the hydrogen-air mixing process. Using the SOpHy cylinder geometry as a test engine, different combinations of the Start of Injection (SOI) and Duration of the Injection (DOI) have been tested. In particular, two early SOI, 137° and 125.5° before Top Dead Center (bTDC), have been compared to a late injection strategy (50° bTDC). Two different DOI have been tested, equal to 6° and 17°. URANS simulations have been carried out to assess the influence of the different injection timings on the uniformity index, which, based on the local equivalence ratio, describes the level of homogenization of the charge. Insights of the equivalence ratio spatial distribution at the ignition timing are provided, along with the observed differences in terms of charge motion (swirl and tumble indices) and turbulence levels, described by the trends of the mean turbulent kinetic energy inside the cylinder. Early injections have been found to realize a nearly homogeneous mixture. This has been observed to be particularly true in the DOI 6° cases, due to the higher level of the charge motion and turbulent kinetic energy induced by the jet momentum. On the other side, the SOI 50° bTDC and DOI 17.5° has been observed not to produce a suitable mixing. For the same SOI, an improvement in the mixture quality has been observed when lowering the DOI to 6°, due to the same reasons found in the early injection cases.
Experimental Collision and Swirl of CFD Simulated Fuel Sprays in a Dual Injector Cylinder Head Concept
Authors: Gutierrez Marcos , Taco Diana , Bösenhofer Markus , Harasek Michael , Castillo Andres , Iniguez Juan , Reyes Gorky , Guanuche Denny
Published: August 2023

A higher level of atomization of the fuel leads to a more homogeneous mixture with the air in internal combustion engines, whether they are equipped with direct injection or port fuel injected systems. The further break-up of the atomized fuel drops by the interaction of two fuel sprays is described in this paper. In the present research, a simulation of the collision and swirl of two fuel sprays in a double-injector engine concept is carried out through a qualitative comparison with the images obtained from the recorded video of the sprays and the results of the simulation. Previous work simulated and tested the spray interaction of fuel injectors on the top of the combustion chamber; while this research proposes a new approach to reduce the diameter of the atomized fuel drops through the direct collision of the sprays with injectors located oppositely and fully horizontally to get advantage of the flow’s momentum. These effects were simulated using of CFD (Computational Fluid Dynamics) with OpenFOAM®, and qualitatively compared under non-reacting conditions with images of recorded videos of the sprays. The results show a reduced diameter of the fuel drops with the direct collision of the fuel sprays and a bigger diameter of those drops with the swirl because of a higher level of coalescence. Even when the diameter of the atomized fuel drops with a single spray is similar to the diameter of the two direct colliding sprays, the required injection time for the two injectors is 50% less. Our work aims to contribute to an enhanced fuel atomization and to the next development stage of internal combustion engines.
Towards H
2
High-Performance IC Engines: Strategies for Control and Abatement of Pollutant Emissions
Authors: Bulgarini Margherita , Della Torre Augusto , Barillari Loris , Montenegro Gianluca , Onorati Angelo , Gullino Fabrizio , Tonelli Roberto
Published: August 2023

In future decarbonized scenarios, hydrogen is widely considered as one of the best alternative fuels for internal combustion engines, allowing to achieve zero CO2 emissions at the tailpipe. However, NOx emissions represent the predominant pollutants and their production has to be controlled. In this work different strategies for the control and abatement of pollutant emissions on a H2-fueled high-performance V8 twin turbo 3.9L IC engine are tested. The characterization of pollutant production on a single-cylinder configuration is carried out by means of the 1D code Gasdyn, considering lean and homogeneous conditions. The NOx are extremely low in lean conditions with respect to the emissions legislation limits, while the maximum mass flow rate remains below the turbocharger technical constraint limit at λ=1 only. To find a trade-off between the two mixture conditions, three different engine control strategies are simulated, imposing a variation of air-to-fuel ratio from λ=2.3 at low load to λ=1 at high load. Different strategies were considered for the transition between minimum and maximum values, including continuous sweep and instantaneous discontinuity. A maximum in the NOx emissions is detected at λ around 1.1 - 1.2, while they remain low in ultra-lean conditions. However, poor drivability is obtained in correspondence of λ discontinuity. Different ATS configurations are proposed and evaluated on the basis of the state-of-the-art technologies and their possible development for the particular H2 engine application. The analysis is carried out by means of numerical simulations performed with the 1D code Axisuite, considering the different emission scenarios associated to the particular engine control strategies and the selected driving cycles (WLTP and RDE). In particular, three different ATS lines are designed, namely TWC-based, SCR-based and LNT-based, exploiting catalytic devices commonly applied on the current Gasoline/Diesel engines. Potential and drawbacks of each configuration are analyzed, considering the requirements in terms of engine control strategies, complexity of the solution, operative temperature, technological challenges and limitation in particular phases of the driving cycle (e.g. cold start or sudden accelerations).
Wall Permeability Estimation in Automotive Particulate Filters
Authors: Samuels Callum , Holtzman Ran , Benjamin Stephen , Aleksandrova Svetlana , Watling Timothy C. , Medina Humberto
Published: August 2023

Porous wall permeability is one of the most critical factors for the estimation of backpressure, a key performance indicator in automotive particulate filters. Current experimental and analytical filter models could be calibrated to predict the permeability of a specific filter. However, they fail to provide a reliable estimation for the dependence of the permeability on key parameters such as wall porosity and pore size.

This study presents a novel methodology for experimentally determining the permeability of filter walls. The results from four substrates with different porosities and pore sizes are compared with several popular permeability estimation methods (experimental and analytical), and their validity for this application is assessed. It is shown that none of the assessed methods predict all permeability trends for all substrates, for cold or hot flow, indicating that other wall properties besides porosity and pore size are important.

The hot flow test results show an increase in permeability with temperature, which is attributed to the effects associated with slip-flow. It is shown that the slip-effect magnitude also varies with the filter wall properties. Existing models that account for the effect of slip are assessed and are shown to underpredict the effect considerably for all four substrates. This is important for the prediction of through-wall losses in applications where permeability increase with temperature is a desirable effect. Further investigation is needed to consider the effect of the high temperatures in exhaust applications.
Evaluation of PM Emissions from Internal Combustion Engines, Electric and Plug-In Hybrid Vehicles by Using Emission Factors
Authors: Castiglione Teresa , Perrone Diego , Polistina Massimo
Published: August 2023

To pursue the target of the “net-zero” emission by 2050 and to reduce the most harmful pollutant emissions from road traffic, more specifically of particulate matter (PM), the transportation sector is subject to significant changes. A transition from internal combustion engine passenger cars (ICEVs) to hybrid vehicles (HEVs) and battery-electric vehicles (BEVs) is taking place. This transition, however, must be carefully examined from different perspectives, as hybridization/electrification may not reduce the levels of PM and CO2 as much as expected. In this work, exhaust and non-exhaust PM emissions of a vehicle powered with an internal combustion engine, and of the same vehicle in plug-in hybrid and electric configurations is carried out, by using the emission factors approach. The main objective is the evaluation of the impact of vehicle weight, of percentage of regenerative braking and of energy management strategy (for hybrid configuration), on tire, wear and road surface wear, which are the most important non-exhaust PM sources. In particular, as most of the studies focus on a comparison between ICEs and BEVs, the current analysis aims at evaluating if the plug-in hybrid configuration, which is half-way between ICE and BEV, can overcome the limitations of electrification and of ICEs in terms of PM emissions. Results for gasoline engine show that a weight increase of 31% and 40% for the hybrid and electric configurations, respectively, with respect to the ICE version, contributes to increase the total PM10 of about 16% and PM2.5 of 9% for PHEV. For BEV, these values amount to 20% for PM10 and to 4% for PM2.5. Adoption of regenerative braking significantly contributes to counteract the effects of a higher weight, so that overall, for PHEV and BEV, total PM emissions are reduced with respect to the ICE versions. In particular, total PM emissions (both PM10 and PM2.5) are reduced of about 3% for PHEV and of 13% for BEV. For the diesel engine, where the weight difference between the ICE and PHEV and BEV versions are more limited (+8% for PHEV and +36% for BEV), higher beneficial effects related to regenerative braking are achieved, so that total PM emissions are reduced of 13% for PHEV and of 14% for BEV, with respect to ICE.
3D-CFD Modelling of Gas Exchange and Combustion Inside the Expander of a Recuperated Split-Cycle Engine
Authors: Sforza Lorenzo , Lucchini Tommaso , Vaghini Alessandra , Bennett Colin , Owen Nick
Published: August 2023

The demand of game-changing technologies to improve efficiency and abate emissions of heavy-duty trucks and off-road vehicles promoted the development of novel engine concepts. The Recuperated Split-Cycle (R-SC) engine allows to recover the exhaust gases energy into the air intake by separating the compression and combustion stages into two different but connected cylinders: the compressor and expander, respectively. The result is a potential increase of the engine thermal efficiency. Accordingly, the 3D-computational fluid dynamics (CFD) modelling of the gas exchange process and the combustion evolution inside the expander becomes essential to control and optimize the R-SC engine concept. This work aims to address the most challenging numerical aspects encountered in a 3D numerical simulation of an R-SC engine. First, the impact of both the mesh features and the boundary conditions is evaluated on the transonic conditions of the air, which enters the expander under a wide range of expansion ratios (1.1÷30). Simulations in a 2D axi-symmetric domain allowed to identify the suitable mesh size required for a correct prediction of the engine volumetric efficiency. Afterwards, simulations of fuel-air mixing and combustion clarified the peculiarities of combustion in R-SC engines, where ignition and combustion are strongly affected by the nonconventional in-cylinder charge motions and temperature stratification.
Simulation of Customer Usage: RENAULT’s Approach for Electric Powertrains
Authors: Bernard Bruno , Atlan Frederic , Maroteaux Damien
Published: August 2023

Simulation of Customer Usage is fully integrated in the design and validation process of RENAULT Powertrains. Application of Customer Usage Simulation to Electric Powertrains brings new challenges enhanced by rapidly changing technologies. New customer usage scenarios, for instance vehicle charging, need to be considered. The technological content of e-powertrain components is becoming more and more complex, increasing complexity of numerical simulation models. Consequently, the trade-off between simulation time and accuracy becomes critical.

This paper addresses RENAULT’s approach to tackle these issues on electric vehicles currently in development. Some examples of recent customer usage simulation results are presented and discussed. Some of the future planned evolutions are discussed: numerical simulation models must be reduced while keeping the right accuracy level; collected data from connected vehicles will soon be fully integrated as inputs to the simulation. Regarding the simulation time, massive parallel computations can now be implemented. Finally, it is necessary to keep technology intelligence active in all fields of interest for customer usage simulation activities.
Analytical and Experimental Handling Performance of Ultra-Efficient Lightweight Vehicles
Authors: Musso Emanuele , Previati Giorgio , Mastinu Gianpiero
Published: August 2023

The rising environmental awareness has led to a growing interest in electric and lightweight vehicles. Four-wheeled Ultra-Efficient Lightweight Vehicles (UELVs) have the potential to improve the quality of urban life, reduce environmental impact and make efficient use of land. However, the safety of these vehicles in terms of dynamic behaviour needs to be better understood. This paper aims to provide a quantitative assessment of the handling behaviour of UELVs. An analytical single-track model and a numerical simulation by VI-CarRealTime are analysed to evaluate the dynamic performance of a UELV compared to a city car. This analysis shows that the lightweight vehicle has a higher readiness (i.e. lower reaction time to yaw rate) for step steering and lower steering effort (i.e. higher steady-state value). Experimental analysis through real-time driving sessions on the Dynamic Driving Simulator assesses vehicle responses and subjective perception for different manoeuvres. The driving performance results are in line with the analytical and numerical simulation. Drivers perceive a quicker response to steering input from the UELV compared to the city car for curves, slalom and lane changes. This performance is subjectively perceived as positive for short sharp manoeuvres and negative for long slalom manoeuvres, where the vehicle behaviour is perceived as nervous and abrupt. Such aggressive driving can be reduced through safe driving training, especially for young drivers.