Mild Hybrid Research Articles

Mitigating HV battery malfunctions in a 48 V P0 mild hybrid system: A novel voltage control strategy

Mitigating HV battery malfunctions in a 48 V P0 mild hybrid system: A novel voltage control strategy

E-Heater Performance for Aftertreatment Warm-Up in a 48V Mild-Hybrid Heavy-Duty Truck over Real Driving Cycles

High-efficiency and low-emissions heavy-duty (HD) internal combustion engines (ICEs) offer significant GHG reduction potential. Mild hybridization via regenerative braking and enabling the use of an electric heater component (EHC) for the aftertreatment system (ATS) warm-up extends these benefits, which can mitigate tailpipe GHG and NOx emissions simultaneously. Understanding such integrated hybrid powertrains is essential for the system optimization of real-world driving conditions. In the present work, the potential of a low engine-out NOx (1.5–2.5 g/kWh range) ‘Low-NOx’ HD diesel engine and EHCs were analyzed in a 48V P1 mild-hybrid system for a class 8 commercial vehicle concept and compared with those in an EPA-2010-certified HD diesel truck as a baseline under real-world driving cycles, including those from the US, Europe, India, China, as well as the world harmonized vehicle cycle (WHVC). For analysis, an integrated 1-D vehicle model was utilized that consisted of models of the ‘Low-NOx’ HD engine, the stock ATS, and a production EHC. For the real driving cycles, ‘GT-RealDrive’-based vehicle speed profiles were generated for busy trucking routes for different markets. For each cycle, the effects of the Low-NOx and EHC performances were quantified in terms of the ATS warm-up time, engine-out NOx emissions, and net fuel consumption. Depending on the driving route, the regenerative braking fully or partly neutralized the EHC power penalty without a significant impact on the ATS thermal performance. For a two-EHC system, the fueling penalty associated with every second reduction in the warm-up time FCEHC (g/s) was several-fold higher for the real driving routes compared with the WHVC. Overall, while a multi-EHC setup accelerated the ATS warm-up, a single EHC integrated at the SCR inlet showed minimized EHC heating power, leading to a minimized fueling penalty. Finally, for the India and China routes, being highly transient, the P1 hybridization proved inadequate for GHG reduction due to the limited energy recuperation. A stronger hybridization was desirable for such driving cycles.

Mild Hybrid Powertrain for Mitigating Loss of Volumetric Efficiency and Improving Fuel Economy of Gasoline Vehicles Converted to Hydrogen Fueling

Mild Hybrid Powertrain for Mitigating Loss of Volumetric Efficiency and Improving Fuel Economy of Gasoline Vehicles Converted to Hydrogen Fueling

Increasing the efficiency of the automotive generator due to active rectification

Problem. Increasing fuel economy requirements for modern vehicles lead to an increase in their electrification. The rise in the number of electrical systems leads to a higher load on the electrical power supply system, with the vehicle's power load reaching 2-3 kW. Leading automobile companies have begun serial production of vehicles with the new 12/48 V power supply voltage standard. The traditional alternator used today is a synchronous alternator, and rectifier diodes are used to convert the generated AC to DC to charge the battery, which is inefficient. A study of losses in an automobile alternator shows that the diode rectifier creates a significant portion of the machine's losses at low speeds, resulting in increased fuel consumption. The solution to this problem is to use a synchronous rectifier to replace traditional rectifier diodes, thus improving the efficiency of the AC/DC rectifier. Goal: To improve the economic and environmental characteristics of a mild hybrid vehicle through the use of a synchronous two-semi-periodic rectifier with a midpoint in the car generator. Methodology: Analytical methods are used to calculate energy losses on diodes and in the phase windings of the generator when employing a two-semiperiod rectifier with a midpoint, compared to a bridge rectifier. Results: The structure, functions, and operation modes of the synchronous rectification system are considered. The effect of synchronous rectification on the generator efficiency of a mild hybrid vehicle is analyzed. It was determined which configurations of synchronous rectification are more effective from the standpoint of energy saving and under which operating conditions. It was determined that in a two-semiperiod rectifier with a midpoint, compared to a bridge rectifier, there will be the same heating of the phase windings and 2 times fewer losses on the diodes. Practical value: A version of the bridge synchronous rectification system of the 48 V generator for a mild hybrid vehicle using MOSFET transistors and specialized control IC is proposed. A synchronous rectification system and its circuit implementation for a 12 V generator based on a two-semi-periodic rectifier scheme with a midpoint is proposed, which allows increasing the energy efficiency and economy of the automobile generator.

Development of a Genetic Algorithm-Based Control Strategy for Fuel Consumption Optimization in a Mild Hybrid Electrified Vehicle’s Electrified Propulsion System

Increasingly stringent pollutant emission regulations and a customer demand for a high-fuel economy drive the modern automotive industry to hurriedly solve the problem of decarbonization and powertrain efficiency, leading R&D towards alternative powertrain solutions and fuels. Electrification, today, plays the biggest role in the topic, with Mild Hybrid Electrified Vehicles (MHEVs) being the most cost-effective architectures, displaying dominance in smaller markets such as Brazil. One of the biggest challenges for HEVs’ development is the complexity of the hybrid control system, knowing when to actuate the electric machine, and the optimum power delivery, plus the gearshift schedule becomes a hard optimization problem that plays a key role in powertrain efficiency and cost savings for the customer. This paper proposes the implementation of a genetic algorithm (GA) as a machine learning-based control strategy to determine the torque split and the gear engaged for each driving condition of an MHEV operation, aiming to optimize fuel consumption. A quasi-static model of the vehicle was developed in Matlab/Simulink version 2022b, the virtual vehicle was then tested following the FTP75 and HWFET driving cycles. Simulation results indicate that the control decisions taken by the GA are qualitatively coherent for all operation conditions, and even quantitatively coherent in some cases, and that the software has the potential to be used as a control strategy outside the simulation environment, in future steps of development.

Combining Gasoline Compression Ignition and Powertrain Hybridization for Long-Haul Applications

Gasoline compression ignition (GCI) combustion was demonstrated to be an effective combustion concept to achieve high brake thermal efficiency with low-reactivity fuels while offering improved NOx–soot trade-off. Nevertheless, future greenhouse gas regulations still challenge the heavy-duty transportation sector on both engine and vehicle basis. Hybridization is a possible solution in this scenario, allowing the avoidance of low-efficiency conditions and energy recovery during regenerative braking, improving overall vehicle efficiency. In this sense, this investigation proposes a detailed analysis to understand the optimum hybridization strategy to be used together with GCI to simultaneously harness low pollutant and CO2 emissions. For that, different hybrid architectures were defined in GT Drive (Mild hybrid 48 V P0 and P2 and full Hybrid P2 500 V) and submitted to 15 different use cases, constituted by five normative and real-driving conditions from the US, China, India, and Europe and three different payloads. Results showed that all hybridization strategies could provide fuel savings benefits to some extent. Nonetheless, usage profile is a dominant factor to be accounted for, benefiting specific hybrid powertrains. For instance, P0 and P2 48 V could provide similar savings as P2 500 V, where regenerative braking is limited. Nonetheless, P2 500 V is a superior powertrain if more demanding cycles are considered, allowing it to drive and recuperate energy without exceeding the Crate limitations of the battery.

The Effectiveness of HEVs Phase-Out by 2035 in Favor of BEVs with Respect to the Production of CO2 Emissions: The Italian Case

The EU has planned the phase-out of new vehicles based on internal combustion engines in favor of high-efficiency battery electric vehicles (BEV) by 2035 (Fit for 55 package). However, many doubts remain about the effectiveness of this choice for each country of the Union in terms of CO2 emissions reduction, as each State is characterized by a different carbon intensity related to the production of electricity needed to manufacture and recharge vehicles. This study seeks to explore the Italian case. To this aim, carbon intensities related to electricity production were calculated considering both the Italian electricity mix production in 2022 and those envisaged in 2035, considering two energy scenarios based on different introductions of renewable energy sources (RES). Afterward, the values obtained were adopted for determining the CO2 emissions related to the whole production process of battery systems in Italy (emissions from mining and refining, scrap materials, and final assembly included) by comparing some of the most up-to-date Life-Cycle Assessment (LCA) analyses related to the manufacturing cycle of the batteries. Finally, the results were adopted to calculate the starting carbon debit for A, B, C, and M car segments for Mild Hybrid, Full Hybrid, and Full Electric powertrains. At the same time, statistical road fuel/electricity consumption data were collected and overall CO2 emissions were calculated for the same vehicles adopting a dynamic approach and plotted for a defined distance, so as to determine break-even points with respect to the cumulative (i.e., from battery and road) carbon emissions. The results showed that advantages related to electric vehicles are significant only if a low carbon intensity related to electricity production is reached by means of a very high introduction of RES, thus keeping the door open for innovative hybrid powertrain technologies, if fed with low carbon fuels.

A ZVS Bidirectional 48V/12V Converter with Magnetic Integration for 48V Mild Hybrid Vehicles

A ZVS Bidirectional 48V/12V Converter with Magnetic Integration for 48V Mild Hybrid Vehicles

Hetero-Solvation-Diluted Strongly-Coordinated Zn2+-Cosolvent Pairs Downshifting Zn Electrode Potential for High-Voltage Hybrid Batteries.

Mild aqueous Zn batteries (AZBs) generally suffer a low-voltage/energy dilemma, which compromises their competitiveness for large-scale energy storage. Pushing Zn anode potential downshift is an admissible yet underappreciated approach for high-voltage/energy AZBs. Herein, with a mild hybrid electrolyte containing in situ-derived diluted strongly-coordinated Zn2+-cosolvent pairs, a considerable Zn anode potential downshift is initially achieved for high-voltage Zn-based hybrid batteries. The chosen butylpyridine cosolvent not only strongly coordinates Zn2+ ions but also acts as a hydrogen-bond end-capping agent to inhibit hydrogen evolution reaction (HER). The electrolyte environment with hetero-solvation-diluted strongly-coordinated Zn2+-cosolvent pairs remarkably lowers Zn2+ activity, responsible for the Zn electrode potential downshift (-0.330V vs Zn), confirming to modified Nernst law (ΔE = ln[a(Zn2 + )/a(coordinated solvent)]). With the diluted Zn2+-containing hybrid electrolyte, the Zn//Zn symmetric cell in the hybrid electrolyte shows a long lifespan over 1270h at a stripping/plating capacity of 0.4mA h cm-2. Compared with in common hybrid electrolytes, the as-assembled Zn-MnO2 hybrid battery delivers a ca. 0.278 V enhanced voltage plateau (1.57V) and a long-term cyclability of over 736 cycles. This work opens a new avenue toward Zn anode potential downshift for high-voltage AZBs, which can extend to other mild metal batteries.

Analysis of the noise mechanism and interactions of torsional decoupling devices in the belt driven 48V mild hybrid powertrain

This paper analyzed the mechanism of rattle noise from a decoupling damper pulley in a 48V belt driven mild hybrid powertrain with a three-cylinder turbo engine. To decouple the 48V belt drive from the high engine torque fluctuation of the engine, a decoupling device at the front end of engine is employed, which interacts with the rear end decoupling device and results in the rattling issue. In this study as opposed to the conventional engine torsional vibration studies which neglect the low inertia belt drive, the effective inertia of 48V belt drive is considered in 1D, 3D torsional vibration analyses of the entire powertrain as it easily reaches up to 20% of the whole torsional inertia. In this way, the impact inside the crank torque fluctuation decoupler was identified as the source of the rattle noise, which verified in the experiments. The interaction of the front end belt drive and the various types of rear end flywheel is also analyzed through parametric studies.

Research on the Mechanical Model and Hysteresis Performance of a New Mild Steel-Rotational Friction Hybrid Self-Centering Damper.

A mild steel-friction self-centering damper with a hybrid energy-dissipation mechanism (MS-SCFD) was proposed, which consisted of a mild steel, frictional, dual-energy-dissipation system and a disc spring resetting system. The structure and principle of the MS-SCFD were explained in detail while the restoring force model was established. The hysteretic behavior of the MS-SCFD under low-cycle reciprocating loading was modeled. Then, the influence of parameters such as the disc spring preload, the friction coefficient, and the soft-steel thickness on the mechanical properties of the MS-SCFD was investigated. The results indicate that the simulation results are basically consistent with the theoretical prediction results, with a maximum error of only 9.46% for the key points of bearing capacity. Since the MS-SCFD is provided with a hysteretic curve in the typical flag type, it will obtain the capacity of excellent self-centering performance. It can effectively enhance the stiffness, bearing capacity, and self-centering capability of the damper after the pre-pressure of the disc spring is increased. The energy-dissipation capacity of the MS-SCFD increases with the increase in the friction coefficient. However, it also increases the residual deformation of the MS-SCFD. The energy dissipation of the MS-SCFD is particularly sensitive to the thickness of mild steel. After being loaded, all components of the MS-SCFD are not damaged except for the plastic deformation caused by the yielding of the mild steel. The normal function of the MS-SCFD can be restored simply by replacing the mild steel plates after the earthquake. Therefore, it can significantly enhance the economy and applicability of the damper.

Mild hybrid energy dual-slope solar stills: Design and performance

The critical increase in the lack of available freshwater worldwide owing to different anthropogenic and natural causes has led mankind to seek serious solutions, such as the use of solar stills. This study shows the design and performance of a dual-slope solar still powered by a mild hybrid power supply system. Different power supply configurations were created for the solar still, and commercial phase change materials were incorporated into the prototype. The highest freshwater production rate in the active solar still (6.76 l/m2d) was obtained when power was supplied from the portable photovoltaic plant at the beginning of the test, with an associated cost per liter of produced water of 0.2218 USD. It was shown that phase change materials increased the heat retention time and optimized the energy supply in the solar still. However, their use did not result in lower freshwater production costs.

Energy Analysis of a Novel Turbo-Compound System for Mild Hybridization of a Gasoline Engine

Efficient and low-polluting mobility is a major demand in all countries. Hybrid electric vehicles have already shown to be suitable to respond to this need, being a reliable alternative to conventional cars, at least in urban environments. Nevertheless, such vehicles present a yet unexplored potential. In this paper, we will investigate how the powertrain efficiency may possibly benefit, in an integrated drivetrain for a hybrid electric vehicle, based on a turbocharged gasoline engine, of an innovative supercharging system. The compressor and turbine will be mechanically decoupled so as to independently optimize their operation, avoiding turbo lag and maximizing energy recovery by completely eliminating the waste-gate valve. This, in turns, requires changing the turbine so as to have a flattest possible efficiency/load curve. Therefore, an ad-hoc designed turbine will be implemented in the decoupled configuration, to be used to drive an electrical generator and produce electrical energy for charging the battery. This study presents a preliminary assessment of the potential of a turbo-compounded system for a 1L turbocharged gasoline engine for a small city car. To this aim, a one-dimensional dynamic model of the engine has been built in GT-Suite and has been calibrated and validated by means of experimental data obtained on a dynamometer, both in steady state and dynamic conditions. In particular, the model has been calibrated by means of experimental data obtained in stationary conditions and its robustness has then been verified through experimental data obtained under transient conditions. The model also includes data retrieved from the characterization of the existing turbine and compressor, while a new performance map for the turbine has been designed to better exploit the potential of the components’ decoupling. Results include the estimation of energy recovery potential of such a solution. Under the implementation of a straightforward control strategy, which runs both compressor and turbine at the same speed, the system is able to achieve a 60.57% increase in energy recovered from the exhaust gasses in the turbine. Afterwards, an attempt was made to limit the minimum turbine speed to 45000 rpm and simultaneously decrease the instantaneous speed by 3000 rpm compared to the compressor, attaining a further increase of 1.7% in the energy recovered by the turbine.

Bifunctional additive: Lead dioxide nanoparticle-doped graphene oxide composites for the preparation and performance study of positive electrodes in lead-carbon batteries

Lead-carbon batteries (LCBs) possess the dual functions of supercapacitors and lead-acid batteries (LABs), which can meet the demand for renewable energy and in mild hybrid electric vehicles (HEVs) for energy storage and short-term high-rate charging and discharging. With the cycle of high-rate partial state-of-charge (HRPSoC), irreversible sulfation of the positive electrode becomes increasingly prominent and serious, resulting in low discharge capacity and short cycle life. In this study, to reduce the sulfation of the positive plate and improve the battery capacity and cycle life, a lead dioxide nanoparticle-doped graphene oxide (nano-PbO2/GO) composite material with dual functions of conducting and nucleating was prepared by a hydrothermal method as a positive electrode additive. The results show that the addition of nano-PbO2/GO promotes the formation of a three-dimensional short rod-like structure of PbO2 nanoparticles in a dendritic arrangement, accelerates the generation of new phases and inhibits the growth of bulk PbSO4. Moreover, the positive plate with nano-PbO2/GO exhibits good electrochemical activity to maintain the stability and reversibility of the electrode redox reaction. Finally, the initial discharge specific capacity of the LCBs with nano-PbO2/GO is increased to 153.85 mAh/g, and the HRPSoC cycle life is up to 15658 cycles at a 2 C discharge rate. Overall, the dual functions of nano-PbO2/GO greatly alleviate battery sulfation and provide a reference for improving the performance of LCBs by modifying the electrode structure.

Energy conversion analysis for mild hybrid electric vehicles equipped with an electric supercharged SI engine via multi-domain acausal modeling

Mild hybrid electric systems, which are highly dependent on engine performance and use less scarce resources, are powertrain systems that can promote immediate vehicle electrification worldwide while taking advantage of existing infrastructure and facilities. In this study, a 12-V mild hybrid electric vehicle (MHEV) with an electric supercharged spark ignition (SI) engine, which is a complex system that integrates an engine, supercharger, electric motor, and battery, was physically modeled using Modelica, a multi-domain acausal modeling language, for a small and light-weight vehicle (vehicle mass: <1000 kg) that aims to make effective use of regenerated power. Additionally, the developed model was used to simulate driving cycle in realistic time and to quantitatively analyze and understand the regenerative power energy conversion process across multiple physical domains and the fuel consumption improvement mechanism in detail and dynamic performance improvement of the electric supercharger. As a result, in the target compact 12-V MHEV with an electric supercharged SI engine, although the intake enthalpy increase due to the intake air compression by the electric supercharger is negligible, the increase in engine speed can be suppressed as the engine torque increases due to supercharging, reducing the engine friction work, in turn resulting in a fuel consumption improvement of approximately 2.5 % under the WLTC mode driving cycle. Furthermore, the electric supercharged SI engine dynamic performance improved by more than 20 %.

Life Cycle Prediction Assessment of Energy Saving and New Energy Vehicles for 2035

The development of energy saving and new energy vehicles is an important technology path to reduce carbon emissions for the transportation industry. To quantitatively predict the life cycle carbon emissions of energy saving and new energy vehicles, this study used the life cycle assessment method and selected the fuel economy level, lightweight level, carbon emission factor of electricity structure, and carbon emission factor of hydrogen production as key performance parameters to establish inventories of internal combustion engine vehicles (ICEV), mild hybrid electrical vehicles (MHEV), heavy hybrid electrical vehicles (HEV), battery electrical vehicles (BEV), and fuel cell vehicles (FCV) based on automotive-related policy and technical routes. The sensitivity of carbon emission factors of electricity structure and different hydrogen production methods were analyzed and discussed. The results showed that the current life cycle carbon emissions (CO2 equivalent) of ICEV, MHEV, HEV, BEV, and FCV were 207.8, 195.2, 149.9, 113.3, and 204.7 g·km-1, respectively. By 2035, BEV and FCV were predicted to have a significant reduction of 69.1% and 49.3%, respectively, compared with ICEV. The carbon emission factor of electricity structure had the most significant influence on BEV life cycle carbon emissions. In terms of different hydrogen production methods of FCV, hydrogen demand should be mainly supplied by industrial hydrogen by-product purification in the short-term future, whereas hydrogen energy production by water electrolysis and hydrogen production from fossil energy combined with carbon capture, utilization, and storage technology should be used to meet the hydrogen demand of FCV in the long-term future, so as to achieve a significant improvement in the life cycle carbon reduction benefits of FCV.

Prospective life cycle assessment of alternatively fueled heavy-duty trucks

The development of renewable drop-in diesel fuels is essential for decarbonizing the diesel-dominated heavy-duty fleet in the short to medium term. Therefore, the project ‘Robust and Efficient processes and technologies for Drop In renewable FUELs for road transport’ (REDIFUEL), developed a novel renewable fuel production technology. The novel fuel, named REDIFUEL, consists of a mixture of high-cetane hydrocarbons and C6-C11 alcohols. This work presents a complete well-to-wheel environmental assessment of REDIFUEL use in heavy-duty mild hybrid and plug-in long haul hybrid trucks with prospective Life Cycle Assessment (LCA). In addition, the use of REDIFUEL is compared to trucks fueled with fossil diesel, conventional biodiesel, and battery electric trucks. The LCA results showed a reduction in climate change impacts of 40–55% in 2030, and 27–64% in 2050 when REDIFUEL displaces fossil diesel. The sensitivity analysis showed that the feedstock value, the payload, and the allocation factor were the most important parameters affecting the climate change results. For most environmental impact categories, plug-in hybrid and battery electric long haul trucks had higher impacts than mild hybrid trucks fueled with REDIFUEL.

Features of designing scenarios for the development of hybrid technologies in the Russian and foreign automotive industry

The relevance of the development of hybrid electric vehicle technology in the automotive industry lies in its diversity. Various degrees of hybridization allow you to get bonuses for both conventional cars with an internal combustion engine and pure electric vehicles, while controlling the level of electrification of your cars, from soft hybrids close to cars with only an internal combustion engine to plug-in hybrids more similar to pure electric vehicles. Depending on the policy of the automaker and the requirements of the market, it is possible to use various designs, including those based on existing developments. The article analyzes the modern automotive market in Russia and the share of cars with hybrid technology in it. A comparison of the development of hybrid technology in modern automotive construction of Russian and foreign automakers is made. The specificity of designing scenarios for the development of hybrid technologies in the Russian and foreign automotive industries is reflected in the very process of using hybrid technology in the models of foreign automakers. Thus, the use of mild hybrid technology is mainly used by automakers with the aim of a smooth transition to more electrified versions, the design and implementation of mild hybrid technology is used by automakers to improve the environmental parameters of their cars while maintaining dynamic performance or to increase the latter. Full hybridization technology can also be used as a transitional for full electrification of models, however, it is mainly used in electric vehicles aimed at a hybrid device. Sequential hybridization technology has not been widely used in passenger cars.

Drive cycle simulation of light duty mild hybrid vehicles powered by hydrogen engine

In the ongoing efforts to reduce CO2 and pollutant emissions, hydrogen combustion engine can provide immediately available mature technology for carbon-free transportation. Hydrogen combustion does not produce on-site CO2 emissions, the principal pollutant is NOx (which can be minimized using appropriate combustion control and aftertreatment), and the available ICE technology can be readily modified to accommodate for hydrogen use. The paper provides a prediction of the performance of a hydrogen combustion engine in passenger vehicles, aiming at extending or updating the available research with the current powertrain trends, namely downsizing, turbocharging, and hybridization. Data gathered from a single-cylinder engine fueled by a lean hydrogen mixture are used as input into a mild hybrid vehicle model, which is used for quasi-static drive cycle simulations. The results show NOx emission around the EURO VI limit without the use of any aftertreatment and fuel consumption as low as 1.1 kgH2/100 km in WLTC.

Battery sizing of 48 V plug-in hybrids considering calendar and cycle degradation

Plug-in hybrid electric vehicles (PHEVs) with battery packs tailored to the driving use case can help to reduce the environmental footprint of the transportation sector. Compared to common high-voltage systems, PHEVs based on a low-voltage level show a higher fuel consumption, but in return benefit from lower component costs and allow the utilization of cheaper high-energy cells. In this paper, the battery size of a 48 V PHEV concept is optimized to minimize the operational costs while taking battery degradation into account and ensure a lifetime-robust system layout. To investigate the applicability of high-energy batteries, 31 automotive-grade cells were investigated experimentally in a calendar and cycle aging study. The results show that calendar aging has a significant contribution of 17.5 % to the overall capacity loss and should be considered during the battery design process. The cycle degradation model is integrated in a Dynamic Programming simulation environment with various real-driving speed and slope profiles, which are extracted from a measured year-round driving profile. The simulation results show, that considering the degradation in the energy management strategy reduces the capacity loss but results in higher operational costs throughout the vehicle lifetime. The extension of a mild hybrid vehicle to a PHEV can reduce the operational costs by 18.5 %. If the vehicle is not charged, the costs increase by 6 % highlighting the need for frequent charging of PHEVs.