bluuebunny/crossref_metadata_2025 huggingface dataset:
Developing Artificial Intelligence (AI) and Machine Learning (ML) Based Soft Sensors for In-Cylinder Predictions with a Real-Time Simulator and a Crank Angle Resolved Engine Model
Authors: Jane Robert , James Corey , Rose Samantha , Kim Tae
Published: April 2023

Currently, there are no safe and suitable fuel sources with comparable power density to traditional combustible fuels capable of replacing Internal Combustion Engines (ICEs). For the foreseeable future, civilian and military systems are likely to be reliant on traditional combustible fuels. Hybridization of the vehicle powertrains is the most likely avenue which can reduce emissions, minimize system inefficiencies, and build more sustainable vehicle systems that support the United States Army modernization priorities. Vehicle systems may further be improved by the creation and implementation of artificial intelligence and machine learning (AI/ML) in the form of advanced predictive capabilities and more robust control policies. AI/ML requires numerous characterized and complete datasets, given the sensitive nature of military systems, such data is unlikely to be known or accessible limiting the reach to develop and deploy AI/ML to military systems. With the absence of data, AI/ML may still be developed and deployed to military systems if supported by near-real-time or real-time computationally efficient and effective hardware and software or cloud-based computing. In this research, an OPAL real-time (OPAL-RT) simulator was used to emulate a compression ignition (CI) engine simulation architecture capable of developing and deploying advanced AI/ML predictive algorithms. The simulation architecture could be used for developing online predictive capabilities required to maximize the effectiveness or efficiency of a vehicle. The architecture includes a real-time simulator (RTS), a host PC, and a secondary PC. The RTS simulates a crank angle resolved engine model which utilized pseudo engine dynamometer data in the form of multi-dimensional matrices to emulate quasi-steady state conditions of the engine. The host PC was used to monitor and control the engine while the secondary PC was used to train the AI/ML to predict the per-cylinder generated torque from the crank shaft torque, which was then used to predict the in-cylinder temperature and pressure. The results indicate that using minimal sensor data and pretrained predictive algorithms, in-cylinder characterizations for unobserved engine variables may be achievable, providing an approximate characterization of quasi-steady state in-cylinder conditions.
Enabling Robust Communication Among Military Ground Vehicles Using Multi-Connectivity
Authors: Mishra Prabodh Kumar , Kar Snigdhaswin , Lin Chun-Chih , Wang Kuang-Ching , Guo Linke
Published: April 2023

Vehicles-to-Everything or V2X communications provide attractive advantages in achieving reliable and high-performance connectivity amongst ground and aerial military vehicles. The 5G New Radio (NR) based cellular-V2X (C-V2X) technology, can support wide coverage areas with higher data rates and lower latencies needed for demanding military applications ranging from real-time sensing to navigation of autonomous military ground vehicles. Millimeter wave technology (mmWave) is critical to meet such throughput and latency requirements. However, mmWave links have a low transmission range and are often subject to blockages due to factors like weather, terrain, etc. that make them unreliable. Multi-connectivity with packet duplication can be used to enhance the reliability and latency by transmitting concurrently over independent links between a mobile device and multiple base stations. We propose and evaluate a novel method based on new radio dual connectivity (NR-DC) and packet duplication techniques to achieve reliable communication between military ground vehicles, especially in mobility scenarios. We further propose and analyze a Channel State Information Reference Signal Received Quality (CSI-RSRQ) based duplication strategy to improve the system's radio resource utilization. Channel State Information Reference Signal symbols in downlink transmissions are used to accurately compute the CSI-RSRQ values of the radio channel in real-time. This is critical on the battlefield for real-time awareness and adaptive control in fast-changing environments. Prototyped in the Simu5G network simulator and MATLAB, our results show packet duplication achieved less than 5 milliseconds of latency with zero packet loss under mobility.
The Pendulum Motion Measured Digital Photogrammetry for a Centrifugal Pendulum Vibration Absorber
Authors: Li Weijun , Wu Guangqiang , Zhang Yi
Published: April 2023

Centrifugal Pendulum Vibration Absorber (CPVA for short) is used to absorb torsional vibrations caused by the shifting motion of the engine. It is increasingly used in modern powertrains. In the research of the dynamic characteristics of the CPVA, it is necessary to obtain the real motion of the pendulum to compensate the fitting performance of mathematical model. The usual method is to install an angle sensor to measure the movement of the pendulum. On the one hand, the installation of the sensor will affect its movement to a certain extent, so that the measurement results do not match the actual motion. On the other hand, the motion of the pendulum is not only the rotational motion around the rotational axis of the CPVA rotor, but also has translation relative to it. As a result, it is difficult to obtain accurate motion only by the angle sensor. We proposed a non-contact centrifugal pendulum motion measurement method. A high-speed camera is used to photograph the motion of the CPVA. For two adjacent images recording its motion, we use the ORB descriptor with rotation invariance to obtain the key points of the images. The Brute-Force Matcher(BF Mathcer) is used to match these points. Then, we calculate the rotational motion of the absorber rotor and the translation of the centrifugal pendulum relative to the rotor after peeling off the rotational motion around it. The method can obtain the motion of the centrifugal pendulum without affecting the motion of the CPVA. It is a feasible method without installation limitation of sensors to study the dynamic characteristics of the CPVA.
Variable-Efficiency Traction Inverter Provides Low Cost Multi-kW Coolant Heating
Authors: Turudic Andy
Published: April 2023

The recent introduction of high power Silicon Carbide (SiC) switching devices has enabled electric vehicle (EV) traction inverters to achieve >99% efficiency. The consequentially low heat loss is horrific to vehicle heating-systems designers, since ~200W of power is available, at highway speeds, to heat a liquid coolant -- an order of magnitude less than that necessary to thermally condition High Voltage (HV) battery packs, and is ~40x lower than the peak heating levels needed to warm a passenger cabin.

Rather than resort to convention by adding expensive and unreliable immersion heaters, including their inherently leak-prone plumbing and high power electronics; or adding exotic heat pumps to scavenge heat, this paper discusses the benefits and implementation of a traction inverter, that eliminates resistive heaters altogether, through novel modalities of either maintaining SiC’s high efficiency or, using a logic signal, to turn on a heating mechanism inherent in switching devices’ physics to provide multi-kilowatt coolant heating intended for HV battery pack and passenger cabin heating.

A review of traditional traction inverter architecture and a brief overview of switching device characteristics is performed at a thermal engineer’s level, along with introducing the heating physics being exploited and the low cost circuit implementation in the novel inverter.

Simulations showing circuit performance at several kilowatts of coolant heating power, independent of vehicle speed, are presented in the context of applicability to the imminent need for extremely cost-competitive EVs that do not provision any expensive heating devices, yet necessarily incorporate this traction inverter for EV propulsion.
Experimental Study on Effect of State of Charge on Thermal Runaway Characteristics of Commercial Large-Format NCM811 Lithium-Ion Battery
Authors: Wei Gang , Zhang Guangxu , Chen Siqi , Jiang Bo , Zhu Jiangong , Han Guangshuai , Wei Xuezhe , Dai Haifeng
Published: April 2023

The application of Li(Ni0.8Co0.1Mn0.1)O2 (NCM811) cathode-based lithium-ion batteries (LIBs) has alleviated electric vehicle range anxiety. However, the subsequent thermal safety issues limit their market acceptance. A detailed analysis of the failure evolution process for large-format LIBs is necessary to address the thermal safety issue. In this study, prismatic cells with nominal capacities of 144Ah and 125Ah are used to investigate the thermal runaway (TR) characteristics triggered by lateral overheating. Additionally, TR characteristics under two states of charge (SoCs) (100% and 5%) are discussed. Two cells with 100% SoC exhibit similar characteristics, including high failure temperature, high inhomogeneity of temperature distribution, multi-points jet fire, and significant mass loss. Two cells with 5% SoC demonstrate only a slight rupture of the safety valve and the emission of white smoke. However, there is a difference: the 144Ah cell still has a significant temperature rise inflection point. Moreover, apart from the early voltage drop before the sudden temperature rise, the environmental pressure shows an even earlier rise. The above phenomenon means the pressure signal could also be used as a valid indicator to predict potential thermal failure events. Interestingly, the ablation traces on the aluminum casing of the TR cells show a spreading arch shape on both the side and bottom surface. In summary, the results indicate that the batteries with a high SoC exhibit a more severe mode of failure and a faster failure evolution process. The research provides a comprehensive insight into the TR evolution process and has specific guiding implications for future TR warnings and thermal safety accident traceability work.
Oil Droplet vs. Film Flow at Discharge and Suction after Shutdown of Automotive Compressor
Authors: Wang Xin , Haider Syed Angkan , Elbel Stefan
Published: April 2023

The compressor oil is retained at different locations of the vapor compression system during operation. After shutdown, retained oil absorbs the vapor refrigerant and mixes with the liquid refrigerant gradually. Oil retention can largely affect the heat transfer and cause insufficient oil return. In this paper, the liquid mixture behaviors at the compressor suction and discharge are observed by flow visualization. Liquid mixture property variations are estimated by existing models according to the temperature and pressure variations. At the suction, the vapor refrigerant solubility with oil rapidly increases due to the pressure increase. The viscosity and surface tension decrease quickly with temperature and refrigerant mass fraction increase in the liquid layer. Flow visualization shows that the mixture film breaks from the top of the tube wall and flows down. The oil-refrigerant mixture accumulates at the bottom of the tube within seconds. The liquid level increases then decreases. At the discharge, the refrigerant solubility fluctuates within a small range. Viscosity increases because of temperature decrease then decreases because of refrigerant mass fraction increase. After shutdown, the oil flow in contact with the inner wall of the discharge stops immediately while oil droplets in the vapor core flow slow down gradually. In the end, oil droplets flow down, coalesce with the oil film, and accumulate at the bottom of the tube. The vapor refrigerant, liquid refrigerant and oil relationship is investigated and estimated after shutdown to better understand oil retention.
Feedback Linearization-based Thermal Control Strategy for Electrified Vehicles
Authors: Rashid Muzamil , Shojaei Sina , Toriumi Fabio , Karimshoushtari Milad , Restrepo Mateo , Weslati Feisel , Bouyoucef Kamal
Published: April 2023

Modern electric vehicles (EVs) have complex thermal systems due to stringent energy efficiency requirements. The thermal systems of such vehicles have highly nonlinear and strongly coupled dynamics as they operate under various thermal modes. Extracting the maximum performance benefits from such complex systems requires elaborate and modern control strategies since classic and rule-based strategies cannot effectively control them. This is becoming a challenge for electric vehicles. Feedback linearization is a control approach that is designed based on the mathematical model of the system. It has the advantage of requiring low computational resources, specifically, low-computational-time and low-memory usage when compared to control strategies such as Model Predictive Control (MPC).

This paper presents a feedback linearization controller that is designed using a nonlinear physics-based model for cabin heating of an electric vehicle. The nonlinear physics-based model is derived from cabin heating governing equations and is correlated with a 1-D model of the thermal systems of the target vehicle. The controller is composed of an Input-Output Feedback Linearization and a Proportional-Integral control. The controller is implemented in an onboard embedded Electronic Control Unit (ECU) and tested on an electrified vehicle. The performance of the classic or Rule-Based controller and the Feedback-Linearization controller are compared.
Revisiting Motion Sickness Models Based on SVC Theory Considering Motion Perception
Authors: Inoue Shota , Liu Hailong , Wada Takahiro
Published: April 2023

Ride comfort improvement and motion sickness reduction are gaining attention given recent technological trends, such as the advancement of automated driving systems, the introduction of in-vehicle digital devices, and the daily use of mobile devices in vehicles. As a countermeasure, mathematical models predicting motion sickness were proposed. Among them, models based on sensory conflict or subjective vertical conflict theories were developed. These models can successfully describe the tendency of motion sickness in several scenarios involving various vestibular inputs or head movements, including carsickness. Almost all models are based on human motion perception with an internal model hypothesis. It has advantages when expanded to model sickness caused by multi-sensory inputs. Some expansions of the models to include the effects of visual information and motion prediction on motion sickness have been made. However, the motion perception calculated by the models has not been investigated, while the motion sickness output has been evaluated for various scenarios, including carsickness. Therefore, as the first step, we focused on vestibular motion sickness. Herein, 6 DoF SVC models of vestibular motion sickness were investigated to determine whether they could describe motion sickness incidence (MSI) as well as motion perception reported in the literature through parameter optimization. In this investigation, four different structures of 6 DoF SVC models, with or without integrals in the feedback process of the observer-theoretic structure, were explored, including the original 6 DoF SVC model. We found that multiple models with optimized parameters could describe the tendency of MSI as well as motion perception.
A Modeling Tool for Particulate Emissions in GDI Engines with Emphasis on the Injector Zone
Authors: Payri Raul , Novella Ricardo , Lopez J. Javier , Abboud Rami
Published: April 2023

Fuel film deposits on combustion chamber walls are understood to be the main source of particle emissions in GDI engines under homogenous charge operation. More precisely, the liquid film that remains on the injector tip after the end of injection is a fuel rich zone that undergoes pyrolysis reactions leading to the formation of poly-aromatic hydrocarbons (PAH) known to be the precursors of soot. The physical phenomena accompanying the fuel film deposit, evaporation, and the chemical reactions associated to the injector film are not yet fully understood and require high fidelity CFD simulations and controlled experimental campaigns in optically accessible engines. To this end, a simplified model based on physical principles is developed in this work, which couples an analytical model for liquid film formation and evaporation on the injector tip with a stochastic particle dynamics model for particle formation. The modeling framework is applicable under steady-state engine operating conditions, and can be extended to transient driving cycle simulations, although the former is only presented in this work. Particle number, mass, and size distributions are validated with experimental measurements performed on a steady-state engine test bench for a 2.0L turbocharged gasoline engine under two engine speeds at part and full load. The model is able to qualitatively capture the main trends in particle number concentration values, especially at the higher load conditions. An underestimation of PN and PM at lower loads is observed, which can be attributed to other sources of particle formation.
Computational Investigation of Combustion Phasing and Emission of Ammonia and Hydrogen Blends under HCCI Conditions
Authors: Bakir Ahmad , Ge Haiwen , Zhao Peng
Published: April 2023

There is a growing interest in ammonia as a potential carbon-free fuel due to the current trend of decarbonization in ground transportation. Benefits of ammonia as a fuel include its high volumetric energy density, ease of storage and transportation, and mature manufacturing infrastructure. On the other hand, ammonia suffers from a low flame speed, long ignition delay times and NOx formation. In this work, a computational investigation of ammonia and hydrogen blends in a 0-D homogeneous charge compression ignition reactor is conducted using different blends under a range of engine-relevant conditions. Iso-contours of the crank angle corresponding to 50% of total heat release (CA50) are developed to assess the reactivity of the different blends under different engine speeds and equivalence ratios. The results show that ammonia requires a high inlet temperature to achieve a CA50 close to top dead center (TDC). An increase in hydrogen concentration resulted in a lower inlet temperature required to achieve a CA50 close to TDC. The gradients of iso-contour can easily show the sensitivity of CA50, as well as NO and H2 formation, to operating temperature and pressure in a wide range of conditions. A sensitivity analysis of the ignition delay showed that combustion phasing is highly promoted through hydrogen oxidation and the chain-branching reactions of the intermediate species. In terms of emissions, H2 and NO possess the highest concentrations, which increase further with increasing hydrogen concentration in the fuel blend. A chemical flux analysis is conducted to understand the role of the reactions and species in H2 and NO formation and consumption. This work provides useful insights into the chemical and thermal role of hydrogen in promoting the combustion of ammonia for future engine applications.
Computational Modeling of the Flow and Heat Transfer in an Internal Combustion Engine-Relevant Cooling Channel
Authors: Wegt Sebastian , Bopp Maximilian , Krüger Louis , Klink Artur , Reitz Ruediger , Hussong Jeanette , Jakirlic Suad
Published: April 2023

The “Water Spider Geometry” (WSG) configuration, representing a newly developed reference test sample designed to suitably investigate the flow and heat transfer processes relevant to cooling systems of internal combustion engines, was computationally investigated by applying a recently proposed Reynolds Stress model called the “Elliptic-Blending Model” (EBM). The WSG configuration resembles a specifically configured pipe geometry that appropriately mimics the flow phenomena encountered in cooling channels of realistic internal combustion engine, such as flow impingement and bifurcation, multiple deflections and flow confluence. The reference database, consisting of mean flow and turbulence fields, was provided by a Large-Eddy Simulation. The EBM formulation has been intensively validated by calculating numerous isothermal wall-bounded flows. The present work focuses on testing the EBM predictive performances under the conditions of non-isothermal flow scenarios. Before proceeding to the WSG configuration, the EBM is pre-validated by computing a jet discharging from a channel-like nozzle and impinging perpendicularly onto a heated wall. The results obtained follow closely the data of the reference Direct Numerical Simulation, also with respect to the predicted second peak at the Nusselt number distribution in terms of different nozzle-to-wall spacing. The EBM-predicted mean velocity field and associated global flow characteristics within the WSG configuration agree well with the results of the reference Large-Eddy Simulation, in contrast to those obtained by the widely used k − ω-SST model, which has been applied in addition. Different treatments of the near-wall region were also used, including integration to the wall and the universal wall-functions. The computationally obtained temperature field evaluated at the WSG walls reveals the hot spot location within a straight pipe segment situated between two deflections, closer to the upstream one, coinciding with the experimentally detected region of most severe degradation caused by intense heating.
Effects of Fuel Injection on Turbulence Enhancement in a Spray-Guided, Gasoline Direct-Injection, Optically Accessible Engine with a High-Pressure Injection System
Authors: Kim Donghwan , Son Yousang , Park Sungwook
Published: April 2023

In this study, the effects of fuel injection on in-cylinder flow under various injection conditions were investigated using particle image velocimetry measurements in a two-cylinder, direct-injection spark-ignition, optically accessible engine with a spray-guided injection system. Various injection timings and pressures were applied to intensify the turbulence of in-cylinder flow. Simple double-injection strategies were used to determine how multiple injections affect in-cylinder flow. The average flow speed, turbulent kinetic energy, and enhancement level were calculated to quantitatively analyze the effects of fuel injection. Fuel injection can supply additional momentum to a cylinder. However, at an early injection timing such as 300° before top dead center, in-cylinder flow development could be disturbed by fuel injection due to piston impingement and interactions between the spray and air. As the injection pressure increased, the in-cylinder flow intensified despite the possibility of increased wall and piston impingement due to lengthened spray penetration. When a double-injection strategy was applied, the second-injection timing was the dominant factor increasing turbulence intensity. As the injection timing was delayed, the effects of fuel injection on in-cylinder flow in the later portion of the compression stroke increased, but with rapid dissipation of momentum during the compression stroke. It would therefore be more effective to apply a multiple-injection strategy and inject a small amount of fuel just before ignition as the final injection to enhance turbulence. However, mixture formation near the spark plug should be considered to increase ignition stability.
A Synergic Use of Innovative Technologies for the Next Generation of High Efficiency Internal Combustion Engines for PHEVs: The PHOENICE Project
Authors: TAHTOUH Toni , Millo Federico , Rolando Luciano , Castellano Giuseppe , Brignone Mauro , Cleeton Jason , Demeilliers Nicolas , Lucignano Gennaro , Sierra Castellanos Juan , Perazzo Alessandro
Published: April 2023

Despite the legislation targets set by several governments of a full electrification of new light-duty vehicle fleets by 2035, the development of innovative, environmental-friendly Internal Combustion Engines (ICEs) is still crucial to be on track toward the complete decarbonization of on road-mobility of the future. In such a framework, the PHOENICE (PHev towards zerO EmissioNs & ultimate ICE efficiency) project aims at developing a C SUV-class plug-in hybrid (P0/P4) vehicle demonstrator capable to achieve a -10% fuel consumption reduction with respect to current EU6 vehicle while complying with upcoming EU7 pollutant emissions limits.

Such ambitious targets will require the optimization of the whole engine system, exploiting the possible synergies among the combustion, the aftertreatment and the exhaust waste heat recovery systems. Focusing on the first aspect, the combined use of innovative in-cylinder charge motion, Miller cycle with high compression ratio, lean mixture with cooled EGR and electrified turbocharger will enable a highly diluted combustion process capable to achieve a peak indicated efficiency of 47% and, at the same time, to minimize the engine out emissions. Numerical simulations were intensively exploited to reduce the engine calibration time and to preliminary assess the benefits of the abovementioned technologies. In particular, 3D-CFD simulations highlighted the capabilities of the SwumbleTM intake ports to produce an increase of about 50% of the Turbulent Kinetic Energy (TKE), while 1D-CFD models showed possible further enhancements of the brake thermal efficiency through the use of the new turbocharger (+2%) and of an aggressive Millerization of the cycle (+1.1%).

Finally, a preliminary experimental campaign, performed on the first engine prototype, confirmed the encouraging results of the simulation activity. With an AFR = 1.43 and an EGR ratio close to 5%, the PHOENICE engine showed a further improvement in the BTE up to 4% and a simultaneous reduction of the NOx emissions of more than 70% in comparison with conventional stoichiometric, undiluted operation.
Knock Inhibition in Hydrogen Fueled Argon Power Cycle Engine with a Higher Compression Ratio by Water Direct Injection at Late Exhaust Stroke
Authors: JIN Shaoye , Deng Jun , Wang Chenxu , Ding Weiqi , Deng Renjie , Yang Hao , Li Liguang
Published: April 2023

Hydrogen-fueled Argon Power Cycle engine is a novel concept for high efficiency and zero emissions, which replaces air with argon/oxygen mixtures as working fluid. However, one major challenge is severe knock caused by elevated in-cylinder temperature resulting from high specific heat ratio of Argon. A typical knock-limited compression ratio is around 5.5:1, which limits the thermal efficiency of Argon Power Cycle engines. In this article, preliminary experimental research on the effect of water direct injection at late exhaust stroke is presented at 1000 r/min with IMEP ranging from 0.3~0.6 MPa. Results show that, with temperature-reducing effect of water evaporation, knock is greatly inhibited and the engine can run normally at a higher compression ratio of 9.6:1. Water injected at the exhaust stroke minimizes its reducing effect on the specific heat ratio of the working fluid during the compression and expansion strokes. Thus, the maximum net indicated thermal efficiency reaches 50.32% when Ar/O2 molar ratio is 90:10 and equivalence ratio is 0.38. Besides, the anti-knock capability is most effective with a water injection timing later than 250°CA ATDC. The highest net indicated thermal efficiencies are obtained with water injection timing from 260 to 280°CA ATDC. Additionally, the water produced through combustion and the water needed for injection are in the same order of magnitude, namely tens of milligrams each cycle. Therefore, only a small tank will be needed as a buffer, if water can be separated and collected from the exhaust gas. This paper suggests that water injection is a feasible method for knock inhibition in the Argon Power Cycle engine.
A Method to Reduce Cold Start Emissions while Shortening Fast Idle Catalyst Light-off Time
Authors: Zhu Shengrong , Hollowell Jeffrey , Ha Kyoung-Pyo , Fantin Nicholas , Shirley Mark
Published: April 2023

For vehicles with internal combustion engines, tailpipe emissions heavily rely on the aftertreatment system, typically a catalytic converter. Modern three-way catalysts (TWC) can very effectively convert the unburnt hydrocarbons (HC), CO, and NOx into non-harmful gases such as H2O, CO2, and N2 when the catalyst brick reaches a relatively high temperature. However, before that catalyst light-off temperature is reached, the emissions conversion efficiency is low, leading to high tailpipe emissions. Due to this light-off temperature requirement of the catalytic converter, the emissions from the engine cold-start period contributes a significant portion of vehicle overall emissions. One of the major reasons for high emissions during cold start is low combustion chamber wall temperatures, lower than the initial boiling temperature of gasoline fuel. This results in fuel film formation, and significantly incomplete evaporation prior to combustion. In this study, an approach to increase the fuel evaporation rate and fuel-air mixing for reduced cold start emissions while attaining fast catalyst light-off time is explored by using CVVD (continuously variable valve duration) & CVVT (continuously variable valve timing) mechanisms for both the intake and exhaust valvetrains. Early exhaust valve closing (EVC) and late intake valve opening (IVO) can be used to create negative valve overlap (NVO) for trapping hot exhaust gas residuals to facilitate fuel vaporization and reduce engine-out emissions during the engine cold-start and warm-up periods. In addition, early exhaust valve opening (EVO) timing can be employed to ensure fast catalyst light-off time. In this paper, a spark-ignited combustion engine is considered, and the engine-out emissions during the cold fast-idle period are studied. Both numerical simulations and engine testing are conducted to analyze the potential improvement of fuel vaporization and cold start emissions reductions with the proposed NVO approach.
Operation of a Natural Gas Direct Injection Compression Ignition Single Cylinder Research Engine
Authors: White Tyler , Eggart Brian , Naber Jeffrey , Turcios Marco , Singh Ashish , Munshi Sandeep
Published: April 2023

The medium and heavy-duty powertrain industry trend is to reduce reliance on diesel fuel and is aligned with continued efforts of achieving ultra-low emissions and high brake efficiencies. Compression Ignition (CI) of late cycle Directly Injected (DI) Natural Gas (NG) shows the potential to match diesel performance in terms of brake efficiency and power density, with the benefit of utilizing a lower carbon content fuel. A primary challenge is to achieve stable ignition of directly injected NG over a wide engine speed and load range without the need for a separate ignition source. This project aims to demonstrate the CI of DI NG through experimental studies with a Single Cylinder Research Engine (SCRE), leading to the development of a mono-fueled NG engine with equivalent performance to that of current diesel technology, 25% lower CO2 emissions, and low engine out methane emissions. The SCRE has a single cylinder displacement of 2.5L and utilizes a high-pressure direct-injection gaseous injector with pilot gas injection capabilities. This is combined with technologies targeting the end-of-compression temperatures required to achieve the autoignition of late cycle injection of NG. These technologies include increased compression ratio and auxiliary charge air heating. The SCRE experimental studies have been successful in demonstrating robust ignition of DI NG, producing high efficiency, stable operation with acceptable pressure rise rates, and good combustion stability. The technology offers direct control of combustion phasing and heat release rate through injection strategy, including pilot and main injection timing and injection pressure. Studies have been conducted to expand the operating range of the SCRE and characterize the interactions of response variables to achieve high efficiency and low emissions operation at increased engine loads, with a final target of 24 bar BMEP.
Improvements of Thermal and Combustion Efficiencies by Modifying a Piston Geometry in a Diesel/Natural Gas RCCI Engine
Authors: Kim Hyunsoo , Kim Wooyeong , Lee Sanguk , Bae Choongsik
Published: April 2023

To meet the target of the CO2 regulations, it is mandatory to replace high-carbon fossil fuels with low-carbon fuels. Diesel/Natural Gas (NG) reactivity-controlled compression ignition (RCCI) can reduce CO2 emission, which stratifies two types of fuels with different reactivity. And also, RCCI produces less NOx and particulate matter emissions by reducing the in-cylinder temperature. However, RCCI must still be enhanced in terms of the thermal and combustion efficiencies at low and medium loads. In this work, a modified piston geometry was applied to improve the RCCI combustion. The piston geometry was designed to minimize heat loss and reduce flame quenching in an RCCI engine. Experiments were conducted using a single-cylinder engine with a displacement volume of 1,000 cc. Diesel was directly injected into the cylinder, and NG was fed through the intake port. Two different engine loads were selected to represent the low and medium loads for the operation of the engine, i.e., 4.3 bar indicated mean effective pressure (IMEP) and 7.5 bar IMEP, respectively. According to the experimental results, the combustion efficiency and thermal efficiency of the modified piston were improved by up to 0.8% and 1.0%, respectively. Energy balance analysis showed that the heat transfer loss decreased by 1.1% owing to the minimal surface area of the piston. Therefore, the thermal efficiency improved. In addition, the combustion efficiency was improved because a large squish height and a small squish distance enabled the flame to reach the crevice area, which had poor conditions for flame maintenance. Heat-loss management using an modified piston geometry can contribute to the reduction in CO2 emissions in RCCI engines.
Lambda Determination Challenges for Ultra-Lean Hydrogen-Fueled Engines and the Impact on Engine Calibration
Authors: Peters Nathan , Bunce Michael
Published: April 2023

An increasing number of zero emission powertrain technologies will be required for meeting future CO2 targets. While this demand will be met by battery and fuel cell electric vehicles in several markets, other solutions are needed for harder to electrify sectors. Hydrogen (H2) internal combustion engines (ICEs) have become an attractive option for high power, high duty cycle vehicles and are expected to play a strong role in achieving zero emission goals. A unique characteristic of H2 ICEs is their ability to operate extremely lean, with lambda (λ) greater than 2. At such conditions, a multitude of benefits are observed including higher thermal efficiency, lower engine-out nitrogen oxides (NOx) emissions, and mitigating common problems with H2 abnormal combustion such pre-ignition and knock. However, two critical issues arise during extreme enleanment of H2 ICEs which have practical implications on controls and calibration of these engines. The first is the ability to properly measure air fuel ratio (AFR); both in a test cell environment and on-vehicle. The second is the deteriorating combustion efficiency with enleanment despite relative engine stability. In this study, several sources of error when measuring AFR for H2 ICEs are discussed and quantified. A H2-specific AFR equation is derived and the sensitivity to various measured combustion products is explored. It is shown that among these, H2 fuel slip introduces the highest sensitivity to exhaust-measured AFR. The challenge this H2 slip AFR sensitivity poses for closed-loop transient controls is explored and the impact on NOx emissions is highlighted.
Data-Driven Prediction of Key Combustion Parameters Based on an Intelligent Diesel Fuel Injector for Large Engine Applications
Authors: Warter Sven , Laubichler Christian , Kiesling Constantin , Kober Martin , Wimmer Andreas , Coppo Marco , Laurenzano Danilo , Negri Claudio
Published: April 2023

Digital technologies are capable of making a significant contribution to improving large internal combustion engine technology. In particular, methods from the field of artificial intelligence are opening up new avenues. So-called “intelligent” engine components rely on advanced instrumentation and data analytics to create value-added data, which in turn can serve as the basis for applications such as condition monitoring, predictive maintenance and controls. For related components and systems, these data may also allow for novel condition monitoring approaches. This paper describes the use of value-added data from an intelligent diesel fuel injection valve that give detailed information about the injection process for real-time prediction of key combustion parameters such as indicated mean effective pressure, maximum cylinder pressure and combustion phasing. These parameters are usually involved in combustion controls and power unit condition monitoring and normally acquired using in-cylinder pressure indication systems, which are costly and prone to wear. On the one hand, a data-driven model for key combustion parameters based on an intelligent fuel injection valve could replace an indication system. On the other hand, such a model may enable backup functionality and mutual condition monitoring of the fuel injection valve and the indication system. The data required for model building were acquired from a medium-speed four-stroke single-cylinder research engine with a displacement of approximately 15.7 dm3. Different machine learning methods are compared to obtain an accurate yet reliable model for each of the desired combustion parameters. In addition to the value-added injection data, readily available parameters on production engines serve as model inputs (e.g., engine speed, charge air and exhaust gas pressures). Based on the results, the quality of the model predictions is evaluated, and it is assessed whether the approach might be useful for series engine applications.
Freevalve: Control and Optimization of Fully Variable Valvetrain-Enabled Combustion Strategies for Steady-State Part Load Performance and Transient Rise Times
Authors: Elmagdoub Abdelrahman W. M. , Carlson Urban , Halmearo Mattias , Turner James , Brace Chris , Akehurst Sam , Zhang Nic
Published: April 2023

In passenger car development, extreme ICE downsizing trends have been observed over the past decade. While this comes with fuel economy benefits, they are often obtained at the expense of Brake Mean Effective Pressure (BMEP) rise time in transient engine response. Through advanced control strategies, the use of Fully Variable Valvetrain (FVVT) technologies has the potential to completely mitigate the associated drivability-penalizing constraints. Adopting a statistical approach, key part load performance engine parameters are analyzed. Design-of-Experiment data is generated using a validated GT-Power model for a Freevalve-converted turbocharged Ultraboost engine. Subsequently, MathWorks' Model Based Calibration (MBC) toolbox is utilized to interpret the data through model fitments using neural network models of optimized architectures. Calibration Generation (CAGE) toolbox is ultimately used to identify best-case look-up tables for the part load steady state performance points based on concluded, case specific, BSFC values. Transient tip-in events are simulated using a step pedal input to full load from the optimized part load points and total rise times are analyzed. For conventional non-FVVT configurations it has been demonstrated that part load cases with higher EGR rates concluded significantly higher T10 (time to 10% of BMEP) values, while T90 (time to 90% of BMEP) and T10-90 (time between 10% and 90% of BMEP) at the tip-in transient were least influenced by residual content. Assuming a Pareto optimal front, this leads to propose that advanced valve control strategies enabled by FVVT technologies, targeting maximum scavenging and optimized EGR rates, are capable of eliminating the potential burden that is turbocharger lag, otherwise sustained in boosted engines as a result of limited cam-based valvetrains, on tip-in transient events from a minimum BSFC steady state part load initial condition.
Experimental Study on Flash Boiling of Ammonia Fuel Sprays – A Potential Alternative Fuel
Authors: Akram Muhammad Saad , Yeganeh Maryam , Cheng Qiang , Kaario Ossi , Larmi Martti
Published: April 2023

The current transportation fuels have been one of the biggest contributors towards climate change and greenhouse gas emissions. The use of carbon-free fuels has constantly been endorsed through legislations in order to limit the global greenhouse gas emissions. In this regard, ammonia is seen as a potential alternative fuel, because of its carbon-free nature, higher octane number and as hydrogen carrier. Furthermore, many leading maritime companies are doing enormous research and planning projects to utilize ammonia as their future carbon-free fuel by 2050. Flash boiling phenomenon can significantly improve combustion by enhancing the spray breakup process and ammonia possessing low boiling point, has a considerable potential for flash boiling. However, present literature is missing abundant research data on superheated ammonia sprays. Therefore, this research work aims to optically investigate the behavior of ammonia sprays under different conditions of fuel temperatures for varying chamber pressures. This work probes overall ammonia spray geometry at engine relevant conditions and compare the results with gasoline sprays. A multi-hole solenoid gasoline injector is used to inject fuels into a constant volume spray chamber and fuel sprays are investigated using optical z-type schlieren imaging technique. Higher fuel temperatures are achieved by installing a heater coil on the injector tip with a sleeve in between to avoid possible heat transfer losses. The experimental results show significant effect of superheating on ammonia and gasoline sprays. The liquid and vapor phase are clearly characterized upon flash boiling, resulting in decreased spray tip penetration and areas compared to ambient fuel temperature conditions. The results also show differences between the overall spray geometries of both fuels, and that ammonia sprays are more sensitive to chamber pressure as compared to gasoline.
Effects of Water Addition on Flash-Boiling Spray of Gasoline and Gasoline/Water Mixtures
Authors: Liu Yifu , Yu Yang , Hou Xinghui , Wu Zhijun
Published: April 2023

To improve the thermal efficiency and inhibit the knock tendency of gasoline direct injection (GDI) engines, water injection technology has a bright application prospect. Utilize gasoline/water mixture as a way to realize this technology can lower the cost of modifying the engines and bring potential for better spray qualities. Hence it is essential to give deep insight into the effects of water on spray atomization, evaporation and mixture formation for gasoline/water mixtures. A spray synchronous measurement experimental system with a single hole nozzle is used to investigate the spray morphology, spray width and droplet size distribution of gasoline/water mixtures sprays under different water volume fractions (0 %, 20 %, 35 %) and different initial fuel temperatures (50 °C~ 130 °C). There are critical temperatures of 80 °C(G100), 100 °C(G80) and 120 °C(G65), above which the ‘collapsed’ spray appears. Noticeably, unlike the collapsed spray caused by jet-jet interactions in the multi-hole nozzles. In this article, the referred ‘collapsed’ spray has a smoother and more curved leading edge. The ‘collapsed’ spray pattern appears because finer droplets appear at high-temperature conditions and the aggregations of small droplets are rarer. The study of the spray width shows that the influence of water is two-sided and more evident under flash boiling conditions. The intensity of spray ‘collapse’ increases with fuel temperature and decreases with water volume fraction. Spray width variation within the axial of 5 mm is revealed by calculating heterogeneous nucleation rate and is mainly related to bubble growth and breakup under flash boiling conditions. The microscopic exploration demonstrates when spray enters flash boiling state, Sauter mean diameter (SMD) falls slightly. However, when fuel temperature reaches the critical temperature, spray enters ‘collapsed’ state and SMD drops drastically. For instance, when G80 spray transforms into flash boiling and ‘collapsed’ state, SMD decreases by 6.05 % and 61.43 % respectively.
Ignition Delay Time of a Toluene Reference Fuel with Substituted Phenol Additives
Authors: Trombley Grace , Toulson Elisa
Published: April 2023

Rapid compression machines can be used to measure a fuel’s ignition delay time and develop an understanding of its resistance to autoignition. Continuing developments in engine design demand higher octane fuels that are resistant to autoignition. Substituted phenols are members of the aromatic hydrocarbon family, and aromatics like toluene are often added to pump-grade gasoline to increase the fuel octane number. Previous numerical and experimental studies have found that substituted phenols included at additive levels in gasoline surrogates, such as the toluene reference fuel in this study, may have a lengthening effect on the ignition delay time of the base fuel they are added to. In this study, the substituted phenols 2,4-xylenol and 3,5-xylenol were added to their own respective toluene reference fuel at 2% by mole, and the ignition delay times of the base fuel mixtures including substituted phenols were compared to the base fuel without additives at engine-relevant conditions for equivalence ratios of φ = 0.6, 0.8, and 1.0. In combination with fuel composition, exhaust gas recirculation has been used to lengthen the ignition delay time of fuel-air mixtures, where exhaust gas recirculation helps to inhibit autoignition of fuel-air mixtures by lowering the combustion temperature of the mixture. The effect of exhaust gas recirculation on the ignition delay time of different fuel compositions was studied by using nitrogen as a diluent. Exhaust gas recirculation was carried out by adding N2 at rates of 15% and 30% for the stoichiometric fuel-air mixtures. Both additives were found to lengthen the ignition delay of the toluene reference fuel at high and low temperatures, but not at mid-range temperatures. 2,4-xylenol had a lengthening effect on the toluene reference fuel at more conditions than 3,5-xylenol did.