International Journal of Powertrains (21 papers in press)
Special Issue on: PMC2016 Powertrains Modelling and Control
by Daniel Worwood, R. Algoo, Ryan McGlen, James Marco, David Greenwood
Abstract: Previous research has identified that the ageing rate and performance of lithium-ion cells is negatively influenced by unfavourable cell thermal conditions, specifically, high ambient temperatures and large in-cell temperature gradients. In this paper, the thermal performance of tab cooling cylindrical cells, which is not well understood within the literature, is compared to more common radial cooling strategies. The analysis is conducted through the development of a 2-D transient bulk layer thermal model displaying anisotropic thermal conductivity. The model is validated against experimental temperature measurements, where the peak error of the simulation was found to be 2% and 5% for the experimental test drive cycle and constant 1 C discharge respectively. Results indicate that radial cooling with air or singular tab cooling with liquid is inadequate in limiting in-cell temperature gradients to below 5 ℃ for HEV type 32113 cells when subject to 4 loops of the US06 drive cycle.
Keywords: Anisotropic thermal conductivity; automotive battery; thermal management; thermal modelling; tab cooling.
A Study of Transient Over-Fuelling During Heavy Knock in an Optical Spark Ignition (SI) Engine
by Hassan Vafamehr, Alasdair Cairns, Hazhir Ebne-Abbasi
Abstract: The work was concerned with improving understanding of the effects of transient over-fuelling during heaving knocking combustion. Heavy knock was deliberately induced using inlet air heating and a primary reference fuel blend of reduced octane rating. Under normal operation the engine was operated under port fuel injection with a stoichiometric air-fuel mixture. Additional excess fuel was then introduced directly into the end-gas in short transient bursts. As the mass of excess fuel was progressively increased a trade-off was apparent, with knock intensity first increasing by up to 65% before lower unburned gas temperatures suppressed knock under extremely rich conditions. This trade-off is not usually observed during conventional low intensity knock suppression via over-fuelling and has been associated with the competing effects of reducing auto-ignition delay time and charge cooling/ratio of specific heats. Overall, the results demonstrate the risks in employing excess fuel to suppress knock deep within a heavy knocking combustion regime.
Keywords: Optical; Auto-Ignition; Developing Detonation; Downsizing; Knock; Super-Knock.
Naturalistic Driving Cycles Synthesis by Markov Chain of Different Orders
by Zifan Liu, Andrej Ivanco, Zoran Filipi
Abstract: This paper evaluates the performance of using Markov Chain of different orders to synthesize real-world representative drive cycles from numerous naturalistic drive cycles. The representative drive cycles can be a valuable input into the design of powertrains, especially for Plug-in Hybrid Electric Vehicle (PHEV) and Electric Vehicle (EV). Their onboard cost-sensitive electric components, such as battery, require an appropriate sizing by understanding how people drive in naturalistic settings. Applying representative drive cycles instead of federal certification drive cycles provides flexibility of drive cycle length and ensures realistic cycle aggressiveness. Even though Markov chain has been widely used to synthesize representative drive cycles, the effects of different orders have not been systematically compared. Based on a publicly accessible portion of GPS-enhanced regional household travel survey, after statistical hypothesis tests, the results show that higher degree of representativeness can be achieved with a 3-order Markov chain compared to a 2-order Markov chain. These findings help to improve the accuracy of cycle synthesis for PHEV and EV analysis.
Keywords: Naturalistic Drive Cycles; Representative Drive Cycles; Markov Chain; Markov Chain Order; Time Series; Hypothesis Test; PHEV; EV
Mean value engine model for early stage design of powertrains with turbocharged SI engines
by Cornelius von Heyden, Jens Neumann, Werner Eissler
Abstract: Due to complexity and computing time, crank-angle resolved engine
simulation does not fit the needs of early stage powertrain development. Therefore,
a mean value model is developed to design powertrains with exhaust turbocharged
spark ignition engines. As turbocharger size strongly affects the transient engine
process, the interaction between turbocharger and internal combustion engine is
investigated and a newmethod is presented to consider different turbocharger sizes
within the same set of mean value engine data. To compensate the linearisation
error in the mean value turbine, two new equations are derived. The newly
introduced turbine factors enable the model to predict the transient engine
behaviour. The model is successfully validated against measured data from
transient driving manoeuvres and sample applications are given. The developed
model offers a speed-up factor of 30-40 compared to a crank-angle resolved
engine model and is especially suited when a large quantity of design parameters
Keywords: powertrain; vehicle; spark ignition engine; turbocharger; mean value model; early stage design; transient engine simulation.
Exhaust Pulse Energy Harvesting An Experimental Investigation on a Single Cylinder Research Engine
by Taylor Bohach, Sundar Rajan Krishnan, Hamidreza Mahabadipour, Kalyan Kumar Srinivasan, Swaminathan Subramanian
Abstract: This paper discusses the theoretical potential of direct exhaust pulse energy harvesting, specifically through a proposed theoretical expander device. A detailed review of pertinent literature determined that there has been little focus specifically on directly converting exhaust pulse energy into useful power. Crank position resolved exhaust pressure was measured as engine load and speed were varied in a single cylinder research (diesel) engine. Potential theoretical improvements average a 12% reduction in overall indicated specific fuel consumption with respect to baseline for the tested operating conditions. Additional parametric studies quantify the effects of intake manifold pressure, exhaust manifold pressure, engine speed and load on measured instantaneous exhaust pressures. Together, these observations are expected to provide a wide range of experimental data to anchor CFD and phenomenological models, which can be used to design viable expander geometries to optimally harness exhaust waste energy in light and heavy-duty engines.
Keywords: blowdown; compounding; displacement; exhaust pulse; expander; heat energy recovery; pulse harvesting; second-law analysis; waste energy recovery.
Modeling and Active Damping of Powertrain Oscillations for RWD Electric Vehicle
by Cheng Lin, Shengxiong Sun, Wenfei Jiang
Abstract: Abstract: With the promotion and popularization of electric vehicles, their driving performance has become an increasingly important issue. As there is no clutch in the powertrain to buffer and absorb the torsional vibrations, vehicle speed oscillations will be caused by various elastic components when the accelerator pedal is stepped or shifted by the driver suddenly. The sudden acceleration input will bring an unpleasant jerk to the vehicle body and accelerates the wear and tear of various parts in the powertrain. In this paper, considering the structure of full electric vehicle, a dynamic model of the powertrain is developed. An optimal feedback controller is proposed based on the state space equation of the vehicle to prevent the driveline from oscillating by actively controlling the motor output torque. The controller parameters are designed based on the optimal control theory. Simulation results demonstrate that the optimal control of motor output torque can reduce the wheel speed oscillations significantly.
Keywords: Key words: electric vehicle; powertrain; dynamic model; oscillations; optimal control.
Real Time Calculation of Residual Gas Fraction Utilizing the Polytropic Coefficient of Compression
by Mark Hoffman, Robert Prucka, Zoran Filipi
Abstract: An algorithm is developed to serve as a stand-alone residual gas fraction diagnostic tool which utilizes the polytropic coefficient of compression and an inverse thermodynamic algorithm to determine trapped residual gas fraction. The model requires: (i) cylinder pressure resolved with at least crank angle resolution, (ii) high accuracy manifold pressure (preferably crank angle resolved and measured very near the intake port), (iii) equivalence ratio of the fuel-air mixture, (iv) mass estimations of cylinder contents other than residual, namely air mass, and fuel mass, (v) cylinder geometry (bore, stroke, clearance volume), and (vi) timing of the intake valve closing event. This work outlines the algorithm methodology and assesses its performance on both an ensemble averaged and individual cycle basis. However, the current RGF calculation methodology is shown to produce unacceptable levels of error on an individual cycle basis. Suggestions are provided for algorithm enhancement.
Keywords: Residual gas fraction; polytropic coefficient; cylinder charge prediction; cylinder pressure; thermodynamics; heat loss; heat transfer.
Upgrading Conventional Cars to Solar Hybrid Vehicles
by Gianfranco Rizzo, Massimo Naddeo, Cecilia Pisanti
Abstract: Upgrading conventional vehicles to hybrid electric vehicles (HEV) can represent a viable and feasible way to reduce fuel consumption and emissions, particularly in urban areas. Hybridization to a Through the Road (TTR) parallel hybrid structure is obtained by integration of wheel motors in rear wheels, the addition of an additional battery, of photovoltaic panels and a vehicle management unit using data from OBD port. In the paper, the main aspects related to vehicle hybridization concerning the impact of different system architectures on optimal energy management, real-time measurement of active gear and neutral gear, and effects of control system structure on vehicle-driver interaction are presented and discussed.
Keywords: Hybrid Vehicles; Hybridization; Energy Management; Vehicle Control.
Transient Load Share Management of a Diesel Electric Hybrid Powertrain for Ship Propulsion
by Sotirios Topaloglou, George Papalambrou, Kostas Bardis, Nikolaos Kyrtatos
Abstract: In this paper, a transient load share methodology for a hybrid diesel electric marine propulsion system is presented. Aim of the system is the performance enhancement and reduction of gaseous emissions during low-load transient operation. The controlled variable is lambda while the manipulated variable is the torque from the electric motor regulated by a frequency inverter. The model for the lambda behavior is based on experimental identification while lambda values in feedback loop come from an actual and a virtual sensor, the later based on first principles modeling. A nominal model is used for the synthesis of a robust H-infinity controller for the controlled variable regulation. Experimental results in a full scale hybrid diesel electric powertrain under realistic loading scenarios verified the successful hybridization.
Keywords: Hybrid-Electric Propulsion; emissions control; diesel engines; robust control.
Special Issue on: PMC2016 Powertrains Modelling and Control
Analysis and design exploration of single stage compound stepped planetary gear transmissions
by Christos Spitas, Amin Amani, Stratos Tsolakis, Vasilios Spitas
Abstract: High-ratio compound stepped planetary transmissions are typically characterised by poor overall efficiencies, even if the individual mesh efficiencies are high, because of the very high sliding velocities imposed by the kinematics of their topologies. Here, a parametric exploration of the design space is presented for a stepped transmission topology, which is assessed in terms of transmission ratio, efficiency, and power density. It is confirmed that high ratio per (compound) stage is accompanied by low mechanical efficiency and/ or large volume for the most part of the parametric design space, as is also anticipated by prior research. At the same time, specific niche regions of particular importance are identified that combine high-ratio, high-efficiency, and good power density.
Keywords: planetary gears; efficiency; volume; transmission ratio; power density.
Dynamic modelling of the turbocharged gasoline direct injection air-path using mean value and linear parameter varying models
by Mohammadjavad Ghomashi, Byron Mason, Mark Cary, Kambiz Ebrahimi, Aitshaam Shahzad
Abstract: Engine models are frequently used to estimate the performance and behaviour of real engines. Various techniques can be applied to facilitate engine modelling. In this regard, mean value engine models (MVEM) describes engine behaviour as an average over one engine cycle but there are some concerns about the validity of MVEM models during transient operation. In this study the performance of MVEM is evaluated by comparing air-path dynamics during transient and steady-state operation for a turbocharged gasoline engine. The comparison is performed experimentally by the measurement of port and manifold fast pressures and calculated air mass flow and cylinder trapped mass during speed and torque transient tests.
In addition, engine models can be linearized at a number of points to represent system nonlinearities. This allows a simple representation of nonlinear systems and facilitates rapid estimation. In this regard, a nonlinear intake manifold model is linearized and several Linear Parameter Varying (LPV) models are formulated using various types of scheduling approaches. The nonlinear engine model and the identified LPV systems are compared based on intake manifold pressure and temperature estimates.
Investigation of MVEM shows the transient cycles are within the steady-state range, whilst the effects of turbocharger performance are significant. The LPV modelling approach showed approximately 90 percent conformity between the linear and nonlinear models for estimating manifold pressure.
Keywords: Air mass flow; intake manifold model; linearization; linear parameter varying; LPV; Mean value engine model; MVEM; transient operation.
A Numerical Study of Intake Valve Jet Flapping in a Gasoline Direct Injection Engine
by Nicholas Beavis, Salah Ibrahim, Weeratunge Malalasekera
Abstract: This paper presents findings from a numerical study of intake valve jet flapping within a gasoline direct injection (GDI) engine, using a large eddy simulation (LES) turbulence modelling approach. The experimental test case and computational setup, including choice of sub-grid scale (SGS) turbulence model, are presented and discussed. An example cycle where intake valve jet flapping is seen to be prominent is discussed in detail. Intake valve jet flapping was found to be initiated as a consequence of turbulent fluctuations in the intake valve curtains. Cycle-by-cycle variations in valve curtain mass flux and the subsequent jet flapping events are investigated and significant cyclic variability is found. It was observed that when an ensemble-averaging procedure, typically used in LES simulations and experimental PIV data post-processing, is applied, due to the cyclic variability of the variations in valve curtain mass flux, most of the information related to this flow phenomenon is lost.
Keywords: CFD; flow; GDI; numerical; valve jet flapping.
Predictive control of commercial e-vehicle using a priori route information
by Pavel Steinbauer, Josef Husak, Florent Pasteur, Petr Denk, Jan Macek, Zbynek Sika
Abstract: The driving range of the vehicle is usually an issue due to the limited energy storage capacity of the acu-pack. Thus, the e-vehicle control towards energy consumption decrease is of extreme importance. The known information about route properties can be used to plan torque/braking profile in optimal way. Several approaches are compared. The first is design approach based on model predictive control (MPC) in combination with prior (before the trip starts) dynamic optimization, the other is model-predictive control using hard limits based on route shape analyses and legal limits. The classical, optimized PID control is used as reference driver. A detailed driving range estimation model of a Fiat Doblo e-vehicle is the basis, including the main e-vehicle subsystem 1D model, e-motor, battery pack, air-conditioning/heating and EVCU. The model calibration is based on real vehicle measurements.
Keywords: E-vehicle; Optimization; Model Predictive Control; Range Extension; Range Estimation Model.
Effect of Radial Turbo-Expander Design on Off-Highway Vehicle Organic Rankine Cycle System Efficiency
by Fuhaid Alshammari, Apostolos Karvountzis-kontakiotis, Apostolos Pesyridis
Abstract: Compared to other Waste Heat Recovery (WHR) technologies, Organic Rankine Cycle (ORC) system is regarded as the most potential candidate due to its simplicity, low cost and small back pressure impact. Expanders are crucial components of the ORC along with working fluid. In this simulation study, an in-house code has been developed to explore the impact of two working fluids on the design of radial expanders. In addition, an off-design turbine analysis has been applied in order to evaluate the performance of the expander at various engine operating points. Moreover, the evaluation of ORC-diesel engine on fuel consumption and exhaust gas emissions is investigated. Compared to conventional diesel powertrain systems, WHR showed an up to 5.7% increase in brake torque and brake power and 5.44% reduction in BSFC. The results also showed that working fluid and the expander speed are critical parameters on the performance of the proposed powertrain configuration.
Keywords: diesel engines; organic Rankine cycle; radial turbine design; waste heat recovery.
Structural Analysis and Topology Optimisation of an Aftercooler Cover for Weight Reduction in Off-Highway Engine Application
by Thomas Murton, Ramin Rahmani, John Crew
Abstract: It is endeavoured to gain design direction by use of computational topology optimisation methods on off-highway engines to improve fuel economy and costs to the service provider via weight reductions. Most published studies are focused on key functional components of an on-highway vehicle that are required for the engine or vehicle to function. However, this study aims to use topology optimisation methods on the off-highway Cummins Inc. QSK78 aftercooler cover to achieve an improved design that at least maintains the current product performance, while the weight of the component is reduced. Such analysis has not hitherto reported in the context of off-highway vehicles. The method involves using topology optimisation techniques based on the given objectives relating to strain energy and natural frequencies. The topology optimisation results are used to provide an informed direction for the design of an optimised 3D CAD model. FEA is used to investigate the structural response of both the baseline and optimised covers. The final optimised design shows an improvement even at worst case of generated stress results while a weight reduction of 6.5% is achieved. It was concluded that further improvements could be made in the optimised design considering limitations due to customer constraints.
Keywords: Topology Optimisation; Aftercooler Cover; Structural Analysis; Engine Design.
Design of Experiments to Generate a Fuel Cell Electro-Thermal Performance Map and Optimise Transitional Pathways
by Quentin Meyer, Lara Rasha, Hans-Michael Koegeler, Simon Foster, Paul Adcock, Paul. S. Shearing, Daniel Brett
Abstract: The influence of the air cooling flow rate and current density on the temperature, voltage and power density is a challenging issue for air-cooled, open cathode fuel cells. Electro-thermal maps have been generated using large datasets (530 experimental points) to characterise these correlations, which reveal that the amount of cooling, alongside with the load, directly affect the cell temperature. This work uses the design of experiment (DoE) approach to tackle two challenges. Firstly, an S-Optimal design plan is used to reduce the number of experiments from 530 to 55 to determine the peak power density in an electro-thermal map. Secondly, the design of experiment approach is used to determine the fastest way to reach the highest power density, yet limiting acute temperature gradients, via three intermediate steps of current density and air cooling rate.
Keywords: fuel cell; electro-thermal mapping; S-optimal design; cost-reduction; optimum transitional pathway.
Design optimization for an additively manufactured automotive component
by Meisam Abdi, Ian Ashcroft, Ricky Wildman
Abstract: The aim of this paper is to investigate the design optimization and additive manufacture of automotive components. A Titanium brake pedal processed through Selective Laser Melting (SLM) is considered as a test case. Different design optimisation techniques have been employed including topology optimization and lattice structure design. Rather than using conventional topology optimization methods, a recently developed topology optimization method called Iso-XFEM is used in this work. This method is capable of generating high resolution topology optimised solutions using isolines/isosurfaces of a structural performance criterion and eXtended Finite Element Method (XFEM). Lattice structure design is the other technique used in the design optimization of the brake pedal. The idea is to increase the stability of the brake pedal to random loads applied to the foot pad area of the pedal. The use of lattice structures can also significantly reduce the high residual stress induced during the SLM process. The results suggest that the integration of the design optimization techniques with a metal additive manufacturing process enables development of a promising tool for producing lightweight energy efficient automotive components.
Keywords: topology optimization; lattice structures; additive manufacturing; automotive; XFEM; isolines; selective laser melting; SLM.
Microgeometrical Tooth Profile Modification Influencing Efficiency of Planetary Hub Gears
by Ehsan Fatourehchi, Mahdi Mohammadpour, Paul King, Homer Rahnejat, Gareth Trimmer, Alan Williams
Abstract: Planetary hub systems offer desired speed and torque variation with a lighter, compact and coaxial construction than the traditional gear trains. Generated friction between the mating teeth flanks of vehicular planetary hubs under varying load-speed conditions is one of the main sources of power loss. Modification of gear tooth geometry as well as controlling the contacting surface topography is the remedial action.
The paper studies the effect of tooth crowning and tip relief upon system efficiency. It includes an analytical elastohydrodynamic analysis of elliptical point contact of crowned spur gear teeth. The analysis also includes the effect of direct contact of asperities on the opposing meshing surfaces. Tooth contact analysis (TCA) is used to obtain the contact footprint shape as well as contact kinematics and load distribution. A parametric study is carried out to observe the effect of gear teeth crowning and tip relief with different levels of surface finish upon the planetary hubs power loss.
Keywords: Transmission efficiency; Gear tooth modification; Planetary wheel hub system; Surface finish.
Special Issue on: Recent Advances in Modelling, Control and Optimisation of Powertrains for Electric and Hybrid Electric Vehicles
Propulsion and Auxiliary Loads Identification and Validation Using HIL Simulations
by Soheil Mohagheghi Fard, Amir Khajepour
Abstract: Electrification of auxiliary systems in service vehicles can noticeably reduce engine idling time and fuel consumption. To replace an engine-driven auxiliary system with electric one, size of required components (a battery pack and a generator) should be determined based on information that can be obtained from propulsion and auxiliary loads of a target vehicle. Propulsion and auxiliary loads are defined as the portion of engine power that is used for moving the vehicle and auxiliary devices, respectively. In this paper, a model-based estimation algorithm is developed to estimate auxiliary and propulsion loads. The algorithm is validated using a hardware-in-the-loop system. The results show that the proposed algorithm can accurately identify propulsion and auxiliary loads in service vehicles.
Keywords: Auxiliary torque estimation; Propulsion load identification; Hardware-in-the-loop; Mass estimation; Auxiliary load identification.
Investigation of Challenges in Interior and Surface Permanent Magnet Synchronous Machines during Integrated Charging Operation in Electric Vehicles
by Lakshmi Varaha Iyer, Chunyan Lai, Shruthi Mukundan, Himavarsha Dhulipati, Kaushik Mukherjee, Narayan Kar
Abstract: Power electronics and motor drive components existing in conventional electric vehicle (EV) drivetrain employed to propel the EV can be used to charge the battery under level 3 fast charging capacity as well. This beneficial feature is propelling research and development activities towards realizing this integrated charging technology in EVs. However, alternating magnetic field will be produced in the air-gap of the permanent magnet (PM) machine as a function of 3-phase AC charging current in its stator windings during integrated charging operation. Theoretically, this is expected to lead to unusual loss and magnet operating characteristics due to the stand-still nature of the rotor. Since, the same PM motor will be used for both traction and integrated charging, it is of paramount importance to understand the machines behavior during integrated charging to optimally design the PM machine for both applications. Hence, this paper exclusively investigates the: 1) permanent magnet operation; 2) electrical and magnet losses; 3) temperature rise; and 4) effect of winding inductances on voltages and currents, in both surface and interior permanent magnet synchronous machines designed for traction application and employed for integrated charging operation in EVs. This is the contribution of the paper. Investigations are conducted on both interior and surface permanent magnet synchronous machines available in the laboratory using their developed electromagnetic models in conjunction with finite element analysis and experimentation. Results obtained from investigations are analyzed and discussed.
Keywords: Electric vehicle; powertrain; permanent magnet; electric motor; traction; charging; design; finite element; harmonics; inductance; losses; demagnetization.
Round and Rectangular Winding Loss Analysis and Optimization for a 22,000rpm 150kW Switched Reluctance Machine
by Daniël Hilgersom
Abstract: Under research is a Switched Reluctance Machine for the powertrain of an electric vehicle. The research focuses on accurate estimation and optimization of winding losses in switched reluctance machines. These losses result from both AC and DC resistance. An FEA based procedure is described which computes both components of loss. Round and rectangular conductors are both analyzed for a number of cases. Ultimately, rectangular conductors are chosen for more thorough analysis. Here, a number of winding geometries are simulated. Plotting conductor geometry versus conductor loss confirms a loss trend with a global minimum. For the motor design under consideration, this represents up to 4kW reduction in loss over the initially simulated round conductors.
Keywords: electric powertrain; coil design; eddy currents; proximity effect; switched reluctance machine; winding losses.