Automotive Power Research Articles

Analysis and Comparison of the Performance of an Inverted Brayton Cycle and Turbocompounding With Decoupled Turbine and Continuous Variable Transmission Driven Compressor for Small Automotive Engines

For an internal combustion engine, a large quantity of fuel energy (accounting for approximately 30% of the total combustion energy) is expelled through the exhaust without being converted into useful work. Various technologies including turbocompounding and the pressurized Brayton bottoming cycle have been developed to recover the exhaust heat and thus reduce the fuel consumption and CO2 emission. However, the application of these approaches in small automotive power plants has been relatively less explored because of the inherent difficulties, such as the detrimental backpressure and higher complexity imposed by the additional devices. Therefore, research has been conducted, in which modifications were made to the traditional arrangement aiming to minimize the weaknesses. The turbocharger of the baseline series turbocompounding was eliminated from the system so that the power turbine became the only heat recovery device on the exhaust side of the engine, and operated at a higher expansion ratio. The compressor was separated from the turbine shaft and mechanically connected to the engine via continuous variable transmission (CVT). According to the results, the backpressure of the novel system is significantly reduced comparing with the series turbocompounding model. The power output at lower engine speed was also promoted. For the pressurized Brayton bottoming cycle, rather than transferring the thermal energy from the exhaust to the working fluid, the exhaust gas was directly utilized as the working medium and was simply cooled by ambient coolant before the compressor. This arrangement, which is known as the inverted Brayton cycle (IBC) was simpler to implement. Besides, it allowed the exhaust gasses to be expanded below the ambient pressure. Thereby, the primary cycle was less compromised by the bottoming cycle. The potential of recovering energy from the exhaust was increased as well. This paper analyzed and optimized the parameters (including CVT ratio, turbine and compressor speed and the inlet pressure to the bottoming cycle) that are sensitive to the performance of the small vehicle engine equipped with inverted Brayton cycle and novel turbocompounding system, respectively. The performance evaluation was given in terms of brake power output and specific fuel consumption. Two working conditions, full and partial load (10 and 2 bar brake mean effective pressure (BMEP)) were investigated. Evaluation of the transient performance was also carried out. Simulated results of these two designs were compared with each other as well as the performance from the corresponding baseline models. The system models in this paper were built in GT-Power which is a one dimension (1D) engine simulation code. All the waste heat recovery systems were combined with a 2.0 L gasoline engine.

Thermomechanical Modeling of Sintered Silver – A Fracture Mechanics-Based Approach

Sintered-silver has proven to be a promising candidate for use as a die-attach and substrate-attach material in automotive power electronics components. It holds promise of greater reliability than lead-based solders – especially for higher temperatures (> 200°C). Accurate predictive lifetime models of sintered silver need to be developed and its failure mechanisms thoroughly characterized before it can be deployed as a die-attach or substrate-attach material in wide-bandgap device-based packages. We present a finite-element-method (FEM) modeling methodology which can offer greater accuracy in predicting the failure of sintered silver under accelerated thermal cycling. A fracture-mechanics-based approach is adopted in the FEM model and J-integral/thermal cycle values are computed. In this paper, we outline the procedures for obtaining J-integral/cycle values in a computational model and report on the possible advantage of using these values as modeling parameters in a predictive lifetime model.

Activity targets for nanostructured platinum-group-metal-free catalysts in hydroxide exchange membrane fuel cells.

Fuel cells are the zero-emission automotive power source that best preserves the advantages of gasoline automobiles: low upfront cost, long driving range and fast refuelling. To make fuel-cell cars a reality, the US Department of Energy has set a fuel cell system cost target of US$30 kW-1 in the long-term, which equates to US$2,400 per vehicle, excluding several major powertrain components (in comparison, a basic, but complete, internal combustion engine system costs approximately US$3,000). To date, most research for automotive applications has focused on proton exchange membrane fuel cells (PEMFCs), because these systems have demonstrated the highest power density. Recently, however, an alternative technology, hydroxide exchange membrane fuel cells (HEMFCs), has gained significant attention, because of the possibility to use stable platinum-group-metal-free catalysts, with inherent, long-term cost advantages. In this Perspective, we discuss the cost profile of PEMFCs and the advantages offered by HEMFCs. In particular, we discuss catalyst development needs for HEMFCs and set catalyst activity targets to achieve performance parity with state-of-the-art automotive PEMFCs. Meeting these targets requires careful optimization of nanostructures to pack high surface areas into a small volume, while maintaining high area-specific activity and favourable pore-transport properties.

Modelling and Simulation of Object Detection in Automotive Power Window

The paper focuses on the system modelling of hardware based power window control system. In power window system, Direct Current (DC) motor served as the source of power to drive the power window frame and accordingly power window can be raised and lowered. In the paper, mathematical model of a DC motor controlled by an H bridge circuit and bridge is controlled through input switches which are available at driver and passenger door side. The main objective of power window control is to control the movement of glass door in upper and lower direction and this operation is controlled with the help of current sensor, fire sensor and position sensor in the replacement of manual control hand turned crank techniques for existing power windows. The driving component is DC motor that drives the power window using selflocking techniques for worm gear in the minimum ratio of 1:50 and output of worm gear goes to lead screw having pitch of 3mm to deliver linear movement to power window. The control unit of power window senses both high and low load obstructions. It is used to activate and deactivate the movement of the glass door in upward direction and downward direction with the help of DC motor, whenever, any hard and soft obstruction is detected. The automatic power window with intelligent control is designed and verified with several conditions that claim its movement in upward and downward direction. The simulation model is visualized in MATLAB/Simulink and performance is analysed with respect to current, voltage and speed measurement.

Comprehensive Study of the Performance of SiC MOSFET-Based Automotive DC–DC Converter Under the Influence of Parasitic Inductance

With low loss, fast switching speed, and high-temperature capabilities, silicon carbide (SiC)-based devices are beneficial to automotive power converters in terms of efficiency increase and size reduction. Nevertheless, as a result of fast switching transitions and low on-state resistance of SiC devices, SiC-based converters are prone to overshoots and oscillations on switching waveforms, with the presence of parasitic inductances in the circuit. The overshoots and oscillations further contribute to increased converter loss and EMI emissions. This paper aims to study the influence of parasitic inductances on the performance of SiC MOSFETs for automotive dc–dc converters from the loss and electromagnetic interference perspective.

Teaching Reforms in Automotive Power train and Chassis Control System Experiment

The Automotive Power train and Chassis Control System Experiment is a supporting course for Automotive Power train Control System and Chassis Control System. This paper discusses the choice of experimental materials and how to vividly explain theoretical knowledge and conduct experiments.

Reliability design of direct liquid cooled power semiconductor module for hybrid and electric vehicles

With the global interests and efforts in popularizing low carbon vehicles, automotive power module has been becoming one of the fastest growing sectors in power semiconductor industry. As working in a harsh environment, the performance and reliability requirements of automotive module are stringent than industrial products. In this work, an integrated direct liquid cooled power module with enhanced reliability for hybrid and electric vehicles (HEV/EV) is developed. The design and assembly of the module were optimized in terms of performance, weight, cost and reliability. The module is integrated Al direct liquid cooling structure, leading to about 40% reduction of weight and cost and almost 50% reduction of junction to heat sink thermal resistance. Therefore, the junction temperature stays below the upper limit at the worst operation case which enhances the thermal reliability and lifetime. By incorporating advanced die lead bonding, the parasitics can be reduced by 50%, which is beneficial to efficiency and reliability. Furthermore, the die and terminal attach technologies are investigated to improve reliability. The lifetime prediction under a typical driving cycle shows that the proposed module is capable of working in the whole vehicle service period.

High-Temperature Synthesized PGM-Free Oxygen Reduction Reaction Catalyst

Platinum group metal-free (PGM-free) oxygen reduction reaction (ORR) electrocatalysts have demonstrated substantial improvements in electrochemical cell and fuel cell performance in the last decade. However, the durability of these catalysts is still insufficient for the implementation of these catalysts in polymer electrolyte fuel cells (PEFCs), particularly in automotive power systems. Recently, carbon oxidation has been reported as a main cause for the destruction of ORR active sites in heat-treated metal-nitrogen-carbon (M-N-C) PGM-free catalysts (1). This result suggests that in order to improve their durability, M-N-C catalysts should be synthesized at as high a temperature as possible to maximize the graphitic content thereby making the catalyst more oxidation resistant. An optimum heat-treatment temperature for the best ORR activity of M-N-C catalysts depends on many factors, including the synthesis approach, type of precursors used, and the precursor ratio. One more factor to account for, based on the reasoning above, is the need to maximize the heat-treatment temperature without sacrificing catalyst activity. In this work we have found that for the high-temperature synthesis of active M-N-C catalysts, the most important factors are the selection of the nitrogen precursor, adjustment of the precursor ratio, and the choice of the synthesis route. Without fine-tuning of the synthesis conditions, the ORR activity of the PGM-free catalysts usually decreases when heat-treated above 900° C. By selecting an appropriate synthesis route and catalyst precursors we have been able to perform synthesis at 1100° C and obtain catalysts that show high RDE activity (E½ of 0.81 V vs. RHE, Figure 1). In this presentation, we will summarize the electrochemical and fuel cell performance of these catalysts, with particular emphasis on their durability. Acknowledgement Financial support of this research by DOE-EERE through Fuel Cell Technologies Office is gratefully acknowledged. Microscopy research was supported through a user project at ORNL’s Center for Nanophase Materials Sciences, which is an Office of Science User Facility. Reference Choi Chang Hyuck, Claudio Baldizzone, Jan-Philipp Grote, Anna K. Schuppert, Frédéric Jaouen, and Karl J. J. Mayrhofer, Stability of Fe-N-C Catalysts in Acidic Medium Studied by Operando Spectroscopy. Angew. Chem. Int. Ed. 54, 1 (2015). Figure 1

Two-phase jet impingement cooling for high heat flux wide band-gap devices using multi-scale porous surfaces

In the future, wide band-gap (WBG) devices such as silicon carbide and gallium nitride will be widely used in automotive power electronics due to performance advantages over silicon-based devices. The high heat fluxes dissipated by WBG devices pose extreme cooling challenges that demand the use of advanced thermal management technologies such as two-phase cooling. In this light, we describe the performance of a submerged two-phase jet impingement cooler in combination with porous coated heat spreaders and multi-jet orifices. The cooling performance of four different porous coated structures was evaluated using R-245fa as the coolant at sub-cooling of 5K. The results show that the boiling performance of a pin-fin heat spreader is the highest followed by that for an open tunnel (OPT), closed tunnel (CLT), and flat heat spreader. Furthermore, the flat heat spreader demonstrated the lowest critical heat flux (CHF), while the pin-fin surface sustained a heat flux of 218W/cm2 without reaching CHF. The CHF values of the OPT and CLT surfaces were 202W/cm2 and 194W/cm2, respectively. The pin-fin heat spreader has the highest two-phase heat transfer coefficient of 97,800W/m2K, while the CLT surface has the lowest heat transfer coefficient of 69,300W/m2K, both at a heat flux of 165W/cm2. The variation of the pressure drop of all surfaces is similar for the entire range of heat fluxes tested. The flat heat spreader exhibited the least pressure drop, 1.73kPa, while the CLT surface had the highest, 2.17kPa at a heat flux of 79W/cm2. Based on the two-phase cooling performance and pressure drop, it is concluded that the pin-fin surface is superior.

Fuel Cell Modeling Strategic Roadmap: A Systematic Approach

Polymer electrolyte fuel cells (PEFCs) are promising electrochemical devices for the direct conversion of chemical energy of a fuel into useful electrical work with vast applications in automotive, stationary, and autonomous power. It is widely recognized that progress in PEFC technology is a multi-disciplinary challenge and hinges on Research and Development (RD Services; Products; High Level Targets; Technology; Science; and Enablers and Resources. This study contributes to a much needed foundation for further planning of potential R&D and demonstration projects of fuel cells for automotive and other emerging sectors.

Determining the Impact of Dynamic Load Conditions on Interfacial Liquid Water Accumulation in Polymer Electrolyte Membrane Fuel Cell Gas Diffusion Layers Using Synchrotron X-Ray Radiography

Automotive power demand is dynamic, so the transient multiphase transport behavior must be understood and considered in the design of next generation polymer electrolyte membrane (PEM) fuel cell materials. In-operando synchrotron X-ray radiography was used to measure the changes in liquid water saturation of the gas diffusion layer (GDL) during changes in operational current density. Through in-operando visualizations at high temporal and spatial resolutions, we observed that the liquid water saturation of the GDL increases with increasing current density, but a threshold saturation in the GDL is eventually reached, despite further increases in current density. A time lag between the change in current density and the onset of increasing GDL saturation was also observed.

Immunity of Automotive Power Line Communication Systems

Power line communication (PLC) could not be established in automotive environments till now due to concerns with the unavoidable electromagnetic disturbances in the vehicle supply nets. Conducted broad band switching noise and field coupled narrow band noise can disturb the communication and prevent higher data rates. The continuously increasing size of the communication cable harnesses in vehicles is very difficult to handle, and PLC could reduce the complexity of the harness. This paper presents an approach to estimate the theoretical limits of PLC in the presence of noise in automobiles. Signal power and bit error rates are computed and discussed, based on electromagnetic compatibility-standards and PLC-parameter sets from older investigations’ noise levels. Commonly used automotive immunity tests are applied to analyze the signal to noise ratio of the PLC in a simulation environment. Therefore, immunity test setup models are introduced in order to analyze the noise injection and coupling characteristics to the PLC receiver. A virtual direct power injection (DPI) test is carried out with narrow band noise and transient pulse injection. For method validation, BCI measurements of a real PLC transceiver were carried out and failure behavior was compared to DPI simulation results. Immunity improvement for single carrier modulation in PLC is proposed. Finally, an analysis of the immunity to pulses is performed and results are discussed.

Impact of DC 48 V on Automotive Power Supply Systems: Comparison with DC 42 V and Future View under DC 60 V

SUMMARYIn the twenty‐first century, rapid advances are being made in the electric propulsion of vehicles as a countermeasure of global warming. In addition, CO2 emissions from all vehicles are to be stringently regulated to 95 g/km by 2020. Thus, most automakers around the world have had to develop not only hybrid electric vehicles, but also conventional internal combustion engine with energy‐saving technology. Battery technology (Li‐ion) and semiconductor technology (SiC and GaN) for automotive power supply systems have proceeded to the mass‐production stage. In 2011, Verband der Automobilindustrie (German OEMs and suppliers) announced the adoption of DC 48 V for the market of 2020. In this paper, we analyze the needs and impact of DC 48 V and compare it with DC 42 V (current technology). We also try to portray the future view under DC 60 V for automotive power supply systems.

(Invited) Impacts of Environmental Stress Factors on Li-Ion Battery Safety Margins

Since the mid-1990’s, many commercial, automotive, and aerospace platforms have transitioned from heritage aqueous electrolyte nickel-based energy storage batteries to lithium-ion battery (LIB) based electrical power subsystems. For space applications, the transition from nickel-hydrogen (Ni-H2) batteries to LIB’s was accelerated by growing concerns with Ni-H2 raw materials obsolescence issues. Although significant research efforts were undertaken to mitigate the risk of Ni-H2 raw materials obsolescence, the recurring cost of maintaining multiple Ni-H2 battery technology supply sources was prohibitive versus the longer-term benefits of supporting a deliberate transition to LIB technologies. Other transitional market forces such as consumer demands to reduce system mass, volume and cost continue to drive the commercial electronics and automotive industries. While it is widely recognized that the mass market for LIB’s in consumer electronics is reaching maturity, the automotive and aerospace marketplace continues to experience new technology growth opportunities. These emerging markets are highly leveraged against economic incentives to pursue safe and reliable LIB design solutions to meet demanding customer requirements. Traditionally, implementing safe and reliable LIB design solutions into aerospace platforms included considerations of simplistic first-order interactions between thermal, mechanical, and electrical environmental stress factors. However, industry experience indicates that the effect of certain synergistic stress factors on LIB performance characteristics in their service environments is a complex multi-dimensional problem. For example, induced and natural environmental stress factors such as thermal cycling, vibration, and radiation have been shown to impact LIB battery performance and in some cases, safety margins. Specifically, certain high-performance LIB aerospace and automotive power systems have recently been challenged to understand the principles governing lithium-ion cell thermal runaway in far greater detail than previously accepted. The severity of lithium-ion cell thermal runaway has created a need for identifying LIB design modifications which reduce degree of severity. The consequences of thermal runaway have the potential to make lithium-ion chemistry an at-risk technology for some applications. To mitigate these risks, investigators from academia, government, and industry have shifted research efforts toward identifying key factors which contribute to the severity of thermal runaway. This work focuses on identifying gaps and opportunities in achieving new paradigms for mitigating LIB safety hazards. Challenges with current technologies to increase LIB safety margins and steps required to reach the readiness level required for successful insertion in an industrial application will also be presented.

Using Sandwich Composite Shells for Fully Pressurized Tanks on Liquefied Petroleum Gas Carriers

The growth of shipping as the main link of the seaborne gas supply chain results from the growing demand for liquefied petroleum gasses due to their various uses, such as fuel for cooking/heating, automotive power, and numerous applications. This study investigates the structural suitability of sandwich composite materials for pressurized tanks, which can be used in on-board carriers or barges for transportation, as well as inland for industrial or residential storage needs. The analytical solution methodology for analysing stresses and deformations is based on higher order shear deformation theory (HSDT). A boundary discontinuous generalized double Fourier series approach is used to solve highly coupled linear partial differential equations. The complementary boundary constraints are introduced through boundary discontinuities, generated by the selected boundary conditions for the derivation of the complementary solution. Numerical solutions are presented for laminated sandwich shells having both cylindrical and spherical forms, which are the preferred geometries for pressurized tanks.

Simulation and experimental research for the energy saving steering pump based on the special speed offsetting

In view of the performance steering pump application, this paper discusses the speed offsetting characteristics in specific speed range based on the action principle of a new variable displacement of the double-action vane pump. Under consideration of serious energy loss of an automotive hydraulic power steering system, the new pump has been designed and produced to overcome the problem. The key components of the pump were tested, and the test results show that the new pump with the speed offsetting can reduce the energy loss of the automotive hydraulic power steering system efficiently. The pump consumes about 20% less energy on average within the specific speed offsetting and hence the prosperous utilisation is expected.

車載パワーデバイスの動向と課題

車載パワーデバイスの動向と課題

Review on Automotive Power Generation System on Plug-in Hybrid Electric Vehicles & Electric Vehicles

Regenerative braking is a function to recharge power bank on the Plug-in electric vehicles (PHEV) and electric vehicles (EV). The weakness of this system is, it can only perform its function when the vehicle is slowing down or by stepping the brake foot pedal. In other words, the electricity recharging system is inconsistent, non-continuous and geography dependent. To overcome the weakness of the regenerative braking system, it is suggested that to apply another generator which is going to be parallel with the regenerative braking system so that continuous charging can be achieved. Since the ironless electricity generator has a less counter electromotive force (CEMF) comparing to an ironcored electricity generator and no cogging torque. Applying the ironless electricity generator parallel to the regenerative braking system is seen one of the options which creates sustainable charging system compared to cored electricity generator.

Automotive power window system design: object-oriented modelling and design of experiments integration within a digital pattern approach

The paper tackles an integrated use of object-oriented modelling (OOM) and design of experiments (DoE) to determine the performance of a double bowden power window system in order to accomplish the expected system performances during the preliminary designing phase and, therefore, by accelerating the product development process. A DoE has been carried out by using the power window model, developed in Dymola environment. The response surface method (RSM) and ANOVA analysis are used to identify the significant factors. Then, an empirical equation is derived. It predicts the main system response i.e. the stroke time, expressed as dependency related to the significant factors. Finally, the use of the empirical relation inside a design flow of a power window, based on digital patterns, is presented.

Reliability of Emerging Bonded Interface Materials for Large-Area Attachments

Conventional thermal interface materials (TIMs), such as greases, gels, and phase change materials, pose bottlenecks to heat removal and have long caused reliability issues in automotive power electronics packages. Bonded interface materials (BIMs) with superior thermal performance have the potential to be a replacement to the conventional TIMs. However, due to coefficient of thermal expansion mismatches between different components in a package and resultant thermomechanical stresses, fractures or delamination could occur, causing serious reliability concerns. These defects manifest themselves in increased thermal resistance in the package. In this paper, the results of reliability evaluation of emerging BIMs for large-area attachments in power electronics packaging are reported. Thermoplastic (polyamide) adhesive with embedded near-vertical-aligned carbon fibers, sintered silver, and conventional lead solder (Sn63Pb37) materials were bonded between 50.8 mm $\times 50.8$ mm cross-sectional footprint silicon nitride substrates and copper base plate samples, and were subjected to accelerated thermal cycling until failure or 2500 cycles. Damage in the BIMs was monitored every 100 cycles by scanning acoustic microscopy. Thermoplastic with embedded carbon fibers performed the best with no defects, whereas sintered silver and lead solder failed at 2300 and 1400 thermal cycles, respectively. Besides thermal cycling, additional lead solder samples were subjected to thermal shock and thermal cycling with extended dwell periods. A finite element method (FEM)-based model was developed to simulate the behavior of lead solder under thermomechanical loading. Strain energy density per cycle results were calculated from the FEM simulations. A predictive lifetime model was formulated for lead solder by correlating strain energy density results extracted from modeling with cycles-to-failure obtained from experimental accelerated tests. A power-law-based approach was used to formulate the predictive lifetime model.