Conventional Powertrain Research Articles

Real-world gaseous and particle emissions of a Bi-fuel gasoline/CNG Euro 6 passenger car

The objective of the present study is the assessment of the environmental impact of a bivalent (bi-fuel) vehicle, running either on gasoline or compressed natural gas (CNG). To that aim, a Euro 6 passenger car was tested under various real-world driving conditions. In order to cover the full range of conventional powertrains currently in the market, the tests were also repeated on a Euro 6 diesel passenger car. Both cars were driven in two routes, the first complying with the regulation limits and the second going beyond them. Carbon monoxide (CO), nitrogen oxides (NOx) and particle number (PN) emissions were recorded using a Portable Emissions Measurement System (PEMS). Apart from the aggregated emission levels, in g/km, the exact emission location along the route was also assessed. Natural gas proved beneficial for CO and PN emissions, the level of which always remained below the respective legislation limits. On the other hand, under the dynamic driving conditions with gasoline, the relevant limits were exceeded. Cold start, occurring at the beginning of the urban part, and motorway driving were identified as major contributors to total emissions, especially in gasoline mode. However, the application of natural gas was associated with a penalty in NOx emissions, which were significantly increased as compared to gasoline. Local peaks within the urban part were identified in CNG mode. In any case, the diesel vehicle was by far the highest NOx emitter.

A tool for the assessment of the potential benefits of electric and hybrid cars for emissions reduction in urban areas

ABSTRACT A simulation tool was developed to evaluate variations in exhaust emissions from cars when replacing conventional powertrains with electric or hybrid propulsion systems. The model permits calculation of direct emissions (released at the vehicles’ exhaust) and indirect emissions (released when producing electricity for batteries recharging). To verify model outputs, a reference scenario was defined selecting the urban area of Genoa, Italy, considering the number of vehicles and mileage of eight vehicle categories. A simulated scenario was then designed, replacing cars belonging to older legally defined classes with electric and hybrid ones. Significant reductions were estimated for regulated pollutants, with higher benefits estimated for CO and NOX emissions, deriving from calculated reductions and contributions of cars in the reference scenario. No advantages were estimated for CO2, outlining that a change in the national mix for electricity production is also required.

Comparing Fuel Consumption and Emission Levels of Hybrid Powertrain Configurations and a Conventional Powertrain in Varied Drive Cycles and Degree of Hybridization

Hybrid electric powertrains in automotive applications aim to improve emissions and fuel economy with respect to conventional internal combustion engine vehicles. Variety of design scenarios need to be addressed in designing a hybrid electric vehicle to achieve desired design objectives such as fuel consumption and exhaust gas emissions. The work in this paper presents an analysis of the design objectives for an automobile powertrain with respect to different design scenarios, i. e. target drive cycle and degree of hybridization. Toward these ends, four powertrain configuration models (i. e. internal combustion engine, series, parallel and complex hybrid powertrain configurations) of a small vehicle (motorized three wheeler) are developed using Model Advisor software and simulated with varied drive cycles and degrees of hybridization. Firstly, the impact of vehicle power control strategy and operational characteristics of the different powertrain configurations are investigated with respect to exhaust gas emissions and fuel consumption. Secondly, the drive cycles are scaled according to kinetic intensity and the relationship between fuel consumption and drive cycles is assessed. Thirdly, three fuel consumption models are developed so that fuel consumption values for a real-world drive cycle may be predicted in regard to each powertrain configuration. The results show that when compared with a conventional powertrain fuel consumption is lower in hybrid vehicles. This work led to the surprisingly result showing higher CO emission levels with hybrid vehicles. Furthermore, fuel consumption of all four powertrains showed a strong correlation with kinetic intensity values of selected drive cycles. It was found that with varied drive cycles the average fuel advantage for each was: series 23 %, parallel 21 %, and complex hybrids 33 %, compared to an IC engine powertrain. The study reveals that performance of hybrid configurations vary significantly with drive cycle and degree of hybridization. The paper also suggests future areas of study.

Aligning vocational training to the electromobile transformation by establishing the “Training Factory Stator Production” – A methodical deficit analysis with derivation of measures

In addition to the current challenges in production technology due to the shift from conventional powertrains towards electrified drive technologies, the disruptive transformation of mobility confronts OEMs and suppliers with major personnel challenges, which include new requirement profiles for prospective skilled workers. In order to meet the personnel requirements of industry and ensure the high quality of vocational training in Germany nonetheless, the current training concepts must be strengthened by the targeted integration of specific contents and be geared holistically to the needs of new occupational profiles. This paper presents a methodological approach for deriving current deficits in vocational education and training through the systematic analysis of framework curricula and the targeted survey of teachers working at German vocational schools as well as the derived training program to support the qualification of trainees. In order to obtain a training concept of high didactic quality, the approach is based on pedagogical methods to provide the best possible support and to convey the learning objectives related to professional, social, methodical, and personal skills. With the newly conceived “Training Factory Stator Production” at the wbk Institute of Production Science of the Karlsruhe Institute of Technology, a program for the training and further education of trainees, skilled employees and engineers will be introduced using the example of producing stators with hairpin technology, to support especially small and medium-sized companies in the personnel transformation process.

Integrated energy-oriented cruising control of electric vehicle on highway with varying slopes considering battery aging

Eco-driving strategies for vehicles with conventional powertrains have been studied for years and attempt to reduce fuel consumption by optimizing the driving velocity profile. For electric vehicles (EVs) with regenerative braking, the speed profile with the best energy efficiency should be different from conventional vehicles. This paper proposes an energy-oriented cruising control strategy for EVs with a hierarchical structure to realize eco-cruising on highways with varying slopes. The upper layer plans the energy-optimized vehicle velocity, and the lower layer calculates the torque allocation between the front and rear axles. However, the resulting speed profile with varying velocity may cause a high charge and discharge rate of the battery, resulting in rapid battery fading. To extend the battery life, we make a tradeoff between the energy consumption and wear of the battery by formulating an optimal control problem, where driving comfort and travel time are also considered. An indirect optimal control method is implemented to derive the optimal control rule. As an extension, the control rule for avoiding rear-end collisions is presented and simulated for driving in the real world.

Multi-objective optimization of virtual formula powertrain design for enhanced performance and fuel efficiency

Formula 1 is considered an important motorsport event that has driven the development of cutting-edge automotive technology. Similarly, virtual formula competition is introduced at the university level to harness technological advances for automotive development among universities. Performance and fuel efficiency have always been two conflicting objectives in determining the optimal powertrain design. In this paper, state-of-the-art multi-objective evolutionary algorithms (MOEAs) are employed to optimize the vehicle powertrain design based on competing event and the on-track performance through software in-the-loop optimization approach. Unlike conventional powertrain optimization approach where the powertrain design is optimized again standard urban driving profiles to achieve optimum driving performance and fuel consumption which is not suitable to be employed to optimize race car powertrain design. The powertrain design is optimized and benchmarked in multiple dynamic test events i.e. Acceleration, Autocross and Endurance. Each event measures different performance parameters (i.e. lap time and fuel consumption) A total of nine design parameters are optimized in this study. Three design parameters (employed to formulate the progressive gear calculation of six gear ratios), five gear shifting rpm (revolutions per minute) and an aerodynamic downforce scale value (for front and rear downforce). Two stages of optimization solution are proposed to handle such complicated design requirement. NSGA-II was identified as the most efficient algorithms among the MOEAs employed in this study; especially in terms of computational time, Pareto distribution and Pareto design. Overall, the optimized powertrain design showed significant improvement in all events i.e. energy efficiency was increased by 13.7% for the endurance event while lap time was reduced by 0.7 and 1.2% in the acceleration and autocross events, respectively.

Energy saving potentials of modern powertrains utilizing predictive driving algorithms in different traffic scenarios

In this article, we analyze the interaction between powertrain technology, predictive driving functionalities, and inner-city traffic conditions. A model predictive velocity control algorithm is developed that utilizes dynamic traffic data as well as static route information to optimize the future trajectory of the considered ego-vehicle. This controller is then integrated into a state-of-the-art simulation environment for automated driving functionalities to calculate energy saving potentials for vehicles with a conventional gasoline engine powertrain and a P3-hybrid powertrain configuration as well as for a battery electric vehicle based on real driving measurements. The comparison of these powertrains under various traffic conditions shows that all three technologies profit from predictive driving functionalities. The determined reduction in energy demand ranges from 15% to more than 40%, but it is highly dependent on the boundary conditions and the selected powertrain technology. Specifically, it is shown that electrified powertrains can profit the most when the time-gap to the preceding vehicle is maintained at a high level. For a conventional powertrain, this effect is less pronounced and can be attributed to the efficiency characteristics of gasoline engines. It can be concluded that the development of advanced predictive driving functionalities requires microscopic simulation of inner-city traffic to achieve optimum results with regard to energy consumption.

Study of System Integral Energy Efficiency of a Hybrid Pneumatic Power System

Currently, in the field of vehicle engineering, researchers are focused on finding a new type of high-efficiency vehicle. Based on the conventional powertrain system, the hybrid pneumatic power system (HPPS) is a type of hybrid system that focuses on compressed air power instead of the electrochemical energy conversion of a battery. This study concentrates on the integral efficiency of the HPPS. The HPPS was operated under different conditions of internal combustion engine speed, fuel consumption, compressor speed, pressure in air tank, cross-sectional area, and air motor efficiency. Based on this, the best operating condition of the HPPS was defined, and the integral efficiency of the HPPS was measured under this condition. The experimental results show that the system integral efficiency can reach up to 45.3%. It is higher than 28% when using individual internal combustion engines. In addition, the HPPS could reduce fuel consumption by 38% during its best performance.

Simulation-based identification of the parameters of a minibus hybrid powertrain

The bus is one of the most popular types of the road public transport and is much less dependent on the external infrastructure than the tram or the trolleybus. However, buses with conventional powertrains are the active sources of the environment pollution. Buses with hybrid powertrain are known to combine the independence of the motorbuses with a conventional internal combustion engine, a considerable reduction in the environmental pollution and the capability of the braking energy recuperation. This explains the increasing interest to the problems of their construction and development of effective control laws for their units and subsystems. Nowadays, these problems are solved by means of the mathematical simulation of the vehicle operation.

Optimization of the parallel and mild hybrid vehicle platforms operating under conventional and advanced combustion modes

Abstract The stringent regulations, increased global temperature and customer demand for high fuel economy have led to rapid developments of different alternative propulsion solutions in the last decade, with special attention to the electrified vehicles. The combination of electric machines with conventional powertrains allows to diversify the powertrain architectures. In addition, alternative combustion modes as reactivity controlled compression ignition (RCCI) have been shown to provide simultaneous ultra-low NOx and soot emissions with similar or better thermal efficiency than conventional diesel combustion (CDC). Therefore, the combination of both technologies creates a promising horizon to be implemented in commercial vehicles of the near future. In this work, experimental and numerical simulations were combined to study the potential of the parallel full hybrid electric vehicle (P2-FHEV) and mild hybrid vehicle (MHEV) to obtain lower fuel consumption and NOx emissions than a conventional powertrain in the Worldwide Harmonized Light Vehicles Cycle (WLTC). The hybrid vehicles are simulated with both CDC and diesel-gasoline RCCI combustion engines as power source. Each powertrain was optimized in terms of components (battery, electric motors…) capacity, internal combustion engine operative points, energy management strategy and gear ratios. The results show a significant fuel consumption reduction as the complexity of the hybrid system increases. The parallel architecture, which represents the most complex hybrid system tested in this work, allows obtaining a fuel consumption reduction of around 20% as compared to CDC. The dual-mode CDC-RCCI concept showed improvements in NOx and soot emissions with comparable values in terms of energy consumption and CO2 emissions than CDC. Additionally, the mild hybrid technology with the functionality of start-stop, torque assist and regenerative braking showed an acceptable balance between complexity and fuel consumption gain.

A Dynamic Fleet Model of U.S Light-Duty Vehicle Lightweighting and Associated Greenhouse Gas Emissions from 2016 to 2050.

Substituting conventional materials with lightweight materials is an effective way to reduce the life cycle greenhouse gas (GHG) emissions from light-duty vehicles. However, estimated GHG emission reductions of lightweighting depend on multiple factors including the vehicle powertrain technology and efficiency, lightweight material employed, and end-of-life material recovery. We developed a fleet-based life cycle model to estimate the GHG emission changes due to lightweighting the U.S. light-duty fleet from 2016 to 2050, using either high strength steel or aluminum as the lightweight material. Our model estimates that implementation of an aggressive lightweighting scenario using aluminum reduces 2016 through 2050 cumulative life cycle GHG emissions from the fleet by 2.9 Gt CO2 eq (5.6%), and annual emissions in 2050 by 11%. Lightweighting has the greatest GHG emission reduction potential when implemented in the near-term, with two times more reduction per kilometer traveled if implemented in 2016 rather than in 2030. Delaying implementation by 15 years sacrifices 72% (2.1 Gt CO2 eq) of the cumulative GHG emissionmitigation potential through 2050. Lightweighting is an effective solution that could provide important near-term GHG emission reductions especially during the next 10-20 years when the fleet is dominated by conventional powertrain vehicles.

A Model-based Scenario Analysis for Assessing the Benefits of Fuel Cell Vehicle Hybridization

Abstract The paper presents model-based scenario analyses of micro and mild tri-hybrid vehicle configurations, related to existing conventional vehicles equipped with small power proton exchange membrane (PEM) fuel cell (FC) systems and, eventually, additional battery pack. The analyses are intended to support short-to medium-term development of fuel cell powered Light Duty Vehicles (LDVs) technology and are useful for carmakers to quantitatively assess the potential advantages associated to the afore-mentioned opportunities in terms of short-term clean and cost-efficient production of hydrogen. The analyses are performed making use of a comprehensive vehicle model, based on a hybrid (black-box and lumped parameters) approach, of a medium passenger car equipped with a turbocharged SI engine. The model has been enhanced to account for the additional components of two different powertrain configurations, namely conventional powertrain with ICE and fuel cell Auxiliary Power Unit (APU) and hybrid powertrain ICE/FC. Simulations have been carried out vs. standard driving cycles for two energy management strategies. The results allow evaluating the impact of powertrain configuration on CO2 emissions, in case of both Tank-to-Wheel (TTW) and Well-to-Wheel (WTW) analyses.

A Method for the Quantification of Powertrain Electrification Impacts on Driving Dynamics

This paper discusses a novel simulation-based study quantifying the impacts of driving dynamics in the electrification of conventional powertrains into hybrid powertrains. Towards this aim, the Fourier amplitude sensitivity test (FAST) is used to facilitate sensitivity analysis. Design of experiments and artificial neural network methods are employed to approximate the solution space to ensure a computationally efficient application of the FAST. To demonstrate this method, a simulation-based study was conducted to evaluate the electrification impacts in a challenging driving dynamic investigation scenario.

Optimal Powertrain Design through a Virtual Development Process

The ever more stringent global CO2 and pollutant emission regulations imply that the optimization of conventional powertrains can only provide partial reductions in fleet emissions. Vehicle manufacturers are therefore responding by increasing the electrification of their powertrain portfolios. This in turn, results in higher levels of electrification of the individual powertrain units. The increase in electric power leads to a comprehensive range of possible technologies—from 48 V mild hybrids to pure electric concepts. The powertrain topology and the configuration of the electrical components of a hybrid powertrain play a decisive role in determining the overall efficiency when considering the individual market requirements. Different hybrid functions as well as performance and customer requirements are determined from statutory cycles and in customer operation. A virtual development chain that is based on MATLAB/Simulink then represents the steps for the identification, configuration, and evaluation of new electrified powertrains. The tool chain presented supports powertrain development through automated conceptualization, design, and evaluation of powertrain systems and their components. The outcome of the entire tool chain is a robust concept decision for future powertrains. Using this methodical and reproducible approach, future electrified powertrain concepts are identified.

Holistic Testing Strategies for Electrified Vehicle Powertrains in Product Development Process

In the field of powertrain engineering, longstanding knowledge was gained for testing conventional vehicle powertrains. The hitherto used test strategies here were more focused on the subsystems of the powertrain than on the powertrain as an integrated system. Through the electrification of the powertrain, the topology and the range of functions have changed. This leads to new challenges for the validation and requires not only adjustments of the test strategies for electric vehicle powertrains but establish and develop integrative tests for the powertrain as an integrated system in order to meet the increased complexity. This paper presents a method to develop a holistic test strategy for a hybrid and electrical vehicle powertrain. In order to avoid misunderstandings of the used terms, it is necessary to create a standard understanding of them. Therefore, a nomenclature is defined and described. Furthermore, a definition of a holistic test strategy is provided. The focus of this present study is on the powertrain and not on its single subsystems. Subsequently, the four steps of the method are introduced and the current results are presented. Finally, a new developed test element within the holistic test strategy is introduced. The findings of this study support the integrative testing for powertrains.

Comparative fuel economy, cost and emissions analysis of a novel mild hybrid and conventional vehicles

Mild hybrid vehicles have been explored as a potential pathway to reduce vehicle emissions cost-effectively. The use of manual transmissions to develop novel hybrid vehicles provides an alternate route to producing low cost electrified powertrains. In this paper, a comparative analysis examining a conventional vehicle and a mild hybrid electric vehicle is presented. The analysis considers fuel economy, capital and ongoing costs and environmental emissions, and includes developmental analysis and simulation using mathematical models. Vehicle emissions (nitrogen oxides, carbon monoxide and hydrocarbons) and fuel economy are computed, analysed and compared using a number of alternative driving cycles and their weighted combination. Different driver styles are also evaluated. Studying the relationship between the fuel economy and driveability, where driveability is addressed using fuel-economical gear shift strategies. Our simulation suggests the hybrid concept presented can deliver fuel economy gains of between 5 and 10%, as compared to the conventional powertrain.

An Integrated Framework on Characterization, Control, and Testing of an Electrical Turbocharger Assist

Electrical turbocharger assist is one of the most critical technologies in improving fuel efficiency of conventional powertrain vehicles. However, strong challenges lie in high efficient operations of the device due to its complexity. In this paper, an integrated framework on characterization, control, and testing of the electrical turbocharger assist is proposed. Starting from a physical characterization of the engine, the controllability and the impact of the electrical turbocharger assist on fuel economy and exhaust emissions are both analyzed. A multivariable robust controller is designed to regulate the dynamics of the electrified turbocharged engine in a systematic approach. To minimize the fuel consumption in real time, a supervisory level controller is designed to update the setpoints of key controlled variables in an optimal way. Furthermore, a cutting-edge experimental platform based on a heavy-duty diesel engine is built. The proposed framework has been evaluated in simulations, physical simulations, and experiments. Results are presented for the developed system and the proposed framework that demonstrate excellent tracking performance, high robustness, and the potential for improvements in fuel efficiency.

Considerations on adapting the new WLTC test cycle for a conventional powertrain to a computerized simulation using AVL Cruise software

Vehicle simulation is a very important part in the design and development of powertrains groups. To precisely simulate the powertrain running status, many commercial software products are applied into the development of control strategy. AVL Cruise software allows the simulation of the vehicle driving performance, fuel consumption and emissions. In 2017 the European Union intends to adopt a unique normalized cycle World Harmonized Light vehicles Testing Cycle – WLTC, more representative for the real traffic, with more aggressive acceleration and patchy, with higher maximum speed, with a greater length of time. A conventional powertrain will be created in the AVL Cruise software and simulate vehicle driving performance, fuel consumption and emissions over the new WLTC test cycle. In order to achieve this, the WLTC test cycle will be written and adapted to the Cruise simulation software for the proposed powertrain. A conventional powertrain, with a unique power source represented by an internal combustion engine will be considered for the sake of simplicity. The results will be useful for the automotive specialists and car manufacturers.

Model-based design validation for advanced energy management strategies for electrified hybrid power trains using innovative vehicle hardware in the loop (VHIL) approach

Hybridization of automotive powertrains by using more than one type of energy converter is considered as an important step towards reducing fuel consumption and air pollutants. Specifically, the development of energy efficient, highly complex, alternative drive-train systems, in which the interactions of different energy converters play an important role, requires new design methods and processes. This paper discusses the inclusion of an alternative hybrid power train into an existing vehicle platform for maximum energy efficiency. The new proposed integrated Vehicle Hardware In-the-loop (VHiL) and Model Based Design (MBD) approach is utilized to evaluate the energy efficiency of electrified powertrain. In VHiL, a complete chassis system becomes an integrated part of the vehicle test bed. A complete conventional Internal Combustion Engine (ICE) powered vehicle is tested in roller bench test for the integration of energy efficient hybrid electric power train modules in closed-loop, real-time, feedback configuration. A model that is a replica of the test vehicle is executed – in real-time- where all hybrid power train modules are included. While the VHiL platform is controlling the signal exchange between the test bed automation software and the vehicle on-board controller, the road load exerted on the driving wheels is manipulated in closed –loop real-time manner in order to reflect all hybrid driving modes including: All Electric Range (AER), Electric Power Assist (EPA) and blended Modes (BM). Upon successful implementation of VHiL, a comparative study between Rule Based (RB) energy management strategy (EMS) and Equivalent Consumption Minimization Strategy (ECMS) to Control Parallel Through-The-Road Hybrid Electric Vehicle (PTTR-HEV) is performed. The study shows that the actual fuel efficiency of the tested vehicle under both control strategies can be used in order to evaluate the effectiveness of energy conversion efficiency of the powertrain system. The fuel consumption of hybridized powertrain is compared with the conventional powertrain equipped in an actual vehicle to help comprehend the degree of efficiency attained by the hybridization. This process is developed in order to enable effective tuning/validation of advanced energy management strategies utilized in hybrid electric powertrain through an evaluation of a complete real chassis system subject to electric hybridization. The VHiL is considered as new evolution for the utilization of vehicle test bed as a predictive mechatronic platform for the development of energy efficient electrified propulsion systems and thus reduce cost and time.

Fuel consumption assessment of a multi-mode low temperature combustion engine as range extender for an electric vehicle

Low temperature combustion (LTC) engines, including homogeneous charge compression ignition (HCCI) and reactivity controlled compression ignition (RCCI), are promising to improve powertrain fuel consumption and reduce NOx and soot emissions by improving the in-cylinder combustion process. However, the narrow operating range of LTC engines limits the use of these engines in conventional powertrains. In range extenders, the engine is decoupled from the drivetrain, which allows the engine to operate in a limited operating range; thus, range extenders offer an ideal application for realizing the advantages of LTC engines. In this study, the optimum fuel consumption improvement of an experimentally developed 2-l multi-mode LTC-SI range extender is investigated in a light-duty battery electric vehicle (BEV) platform. In the optimization framework, the mode-switching fuel penalty, exhaust aftertreatment catalyst light-off temperature, and engine noise, vibration, harshness (NVH) are considered. The engine operation modes include HCCI, RCCI, and conventional spark ignition (SI). The simulation results show in the city driving cycle, the single-mode HCCI and RCCI range extenders offer 11.0% and 5.4% fuel consumption improvement, respectively over a single-mode SI range extender. These improvements increase to 12.1% and 9.1% in the highway driving cycles. In the multi-mode operation, up to 1.4% higher fuel economy is achieved over different driving cycles, compared to single-mode HCCI/RCCI operation. As the driving cycle average demanded power increases, the contribution of the RCCI mode predominates the HCCI mode.