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Technical Paper

1D Engine Simulation Approach for Optimizing Engine and Exhaust Aftertreatment Thermal Management for Passenger Car Diesel Engines by Means of Variable Valve Train (VVT) Applications

Using a holistic 1D engine simulation approach for the modelling of full-transient engine operation, allows analyzing future engine concepts, including its exhaust gas aftertreatment technology, early in the development process. Thus, this approach enables the investigation of both important fields - the thermodynamic engine process and the aftertreatment system, together with their interaction in a single simulation environment. Regarding the aftertreatment system, the kinetic reaction behavior of state-of-the-art and advanced components, such as Diesel Oxidation Catalysts (DOC) or Selective Catalytic Reduction Soot Filters (SCRF), is being modelled. Furthermore, the authors present the use of the 1D engine and exhaust gas aftertreatment model on use cases of variable valve train (VVT) applications on passenger car (PC) diesel engines.
Technical Paper

1D Modelling of Fuel Cell Losses Including the Water and Thermal Management

Fuel cells plays significant role in the automotive sector to substitute the fossil fuels and complement to electric vehicles. In the fuel cell vehicles fuel cell stack is major component. It is important to have a robust fuel cell model that can simulate the behaviour of the fuel cell stack under various operating conditions in order to study the functioning of a fuel cell and optimize its operating parameters and achieve the best efficiency in operation. The operating voltage of the fuel cell at different current densities depends upon thermodynamic parameters like temperature and pressure of the reactants as well factors like the state of humidification of the electrolyte membrane. A 1D model is developed to capture the variation in voltage at different current densities due to internal losses and changes to operating conditions like temperature and pressure.
Technical Paper

1D Transient Thermal Model of an Automotive Electric Engine Cooling Fan Motor

For the thermal management of an automobile, the induced airflow becomes necessary to enable the sufficient heat transfer with ambient. In this way, the components work within the designed temperature limit. It is the engine-cooling fan that enables the induced airflow. There are two types of engine-cooling fan, one that is driven by engine itself and the other one is electrically driven. Due to ease in handling, reduced power consumption, improved emission condition, electrically operated fan is becoming increasingly popular compared to engine driven fan. The prime mover for electric engine cooling fan is DC motor. Malfunction of DC motor due to overheating will lead to engine over heat, Poor HVAC performance, overheating of other critical components in engine bay. Based upon the real world driving condition, 1D transient thermal model of engine cooling fan motor is developed. This transient model is able to predict the temperature of rotor and casing with and without holes.
Journal Article

1D-3D Online Coupled Transient Analysis for Powertrain-Control Integrated Thermal Management in an Electric Vehicle

Thermal management in electric vehicles (EVs) has attracted more attention due to its increasing significance, and computer aided engineering (CAE) plays an important role in its development. A 1D-3D online coupling approach is proposed to completely characterize transient thermal performance of an electric vehicle on a high performance computer (HPC) platform. The 1D thermal management model, consisting of air conditioning, motor cooling and battery cooling systems, is integrated with the 1D control strategy model and powertrain model consisting of motor, battery, driver and vehicle models. The 3D model is established for the air flow around the full vehicle and through its underhood. The 3D model gives boundaries such as heat exchanger air flowrates and heat flows on some component surfaces to the 1D model, while 1D gives back boundaries such as heat exchanger heat loads, component surface temperatures and fan speed simultaneously.
Technical Paper

2005 Ford GT- Maintaining Your Cool at 200 MPH

An integrated engineering approach using computer modeling, laboratory and vehicle testing enabled the Ford GT engineering team to achieve supercar thermal management performance within the aggressive program timing. Theoretical and empirical test data was used during the design and development of the engine cooling system. The information was used to verify design assumptions and validate engineering efforts. This design approach allowed the team to define a system solution quickly and minimized the need for extensive vehicle level testing. The result of this approach was the development of an engine cooling system that adequately controls air, oil and coolant temperatures during all driving and environmental conditions.
Technical Paper

3-D Modeling of Heat Transfer in Diesel Engine Piston Cooling Galleries

Ever increasing specific power of diesel engines has put huge demand on effective thermal management of the pistons for the desired reliability and durability. The piston temperature control is commonly achieved by injecting cooling oil into piston galleries, but the design of the cooling system as well as the boundary conditions used in FEA simulations have so far relied mostly on empirical methods. A numerical procedure using 3D computational fluid dynamics (CFD) has therefore been developed to simulate the cooling process and to estimate the cooling efficiency of gallery. The model is able to predict the detailed oil flow and heat transfer in gallery, of different designs and engine applications, under dynamic conditions. The resulted spatially resolved heat transfer coefficient from the CFD model, with better accuracy, enables improved prediction of piston temperature in finite element analysis (FEA).
Journal Article

48 V High-power Battery Pack for Mild-Hybrid Electric Powertrains

Mild hybridisation, using a 48 V system architecture, offers fuel consumption benefits approaching those achieved using high-voltage systems at a much lower cost. To maximise the benefits from a 48 V mild-hybrid system, it is desirable to recuperate during deceleration events at as high a power level as possible, whilst at the same time having a relatively compact and low cost system. This paper examines the particular requirements of the battery pack for such a mild-hybrid application and discusses the trade-offs between battery power capabilities and possible fuel consumption benefits. The technical challenges and solutions to design a 48 V mild-hybrid battery pack are presented with special attention to cell selection and the thermal management of the whole pack. The resulting battery has been designed to achieve a continuous-power capability of more than 10 kW and a peak-power rating of up to 20 kW.
Technical Paper

50 KVA High Temperature Bi-directional Converter for On-Engine Application in More Electric Aircraft

The transition towards More Electric Aircraft (MEA) architectures has challenges relating to integration of power electronics with the starter generator system for on-engine application. To efficiently operate the power electronics in the hostile engine environment at high switching frequency and for better thermal management, use of silicon carbide (SiC) power devices for a bi-directional power converter is examined. In this paper, development of a 50 kVA bi-directional converter operating at an ambient temperature of about 2000C is presented. The design and operation of the converter with details of control algorithm implementation and cooling chamber design are also discussed.
Technical Paper

A 5 Phase Brake Insulator Engineering Selection Process

Brake squeal signatures (2 kHz to 18 kHz) have tonal content highly dependent on the specific brake system structural architecture. The challenge in minimizing squeal involves correctly identifying the conditions (temperature, apply pressure, rotor speed as some basic parameters) of occurrence, defining the underlying structural dynamics of the system and applying appropriate suppression solutions. The quantitative metric of improvement is the cumulative event percentage of occurrence. Design variables of the brake system and performance attribute targets extend the challenge beyond the level of just reducing noise. Consideration of material costs, manufacturing/assembly factors, durability, thermal management as well as other factors narrow the solution space significantly. Compressed late stage development is not uncommon in reaching acceptable levels of performance and is a primary reason for following a well defined process flow with provision for alternative solutions.
Technical Paper

A Case Study of Compressor Surge Related Noise on Turbocharged 2.0-L Gasoline Engine

Till recently supercharging was the most accepted technique for boost solution in gasoline engines. Recent advents in turbochargers introduced turbocharging technology into gasoline engines. Turbocharging of gasoline engines has helped in powertrains with higher power density and less overall weight. Along with the advantages in performance, new challenges arise, both in terms of thermal management as well as overall acoustic performance of powertrains. The study focuses mainly on NVH aspects of turbocharging of gasoline engines. Compressor surge is a most common phenomenon in turbochargers. As the operating point on the compressor map moves closer to the surge line, the compressor starts to generate noise. The amplitude and frequency of the noise depends on the proximity of the operating point to the surge line. The severity of noise can be reduced by selecting a turbocharger with enough compressor surge margin.
Technical Paper

A Combined CFD and Flow Network Modeling Approach for Vehicle Underhood Air Flow and Thermal Analysis

Conventional CFD analysis for underhood thermal management is quite involved and time consuming because of the complex geometry and flow distributions. As an alternative to full scale CFD modeling, a hybrid method of vehicle underhood air flow and thermal analysis is presented in this paper, using the principle of flow network modeling (FNM) and CFD. In the present method, the entire flow domain in underhood is broken into various air flow passages, which are represented in a FNM model by nodes and links. For each individual air flow passage selected, CFD analysis is carried out to obtain the pressure drop (ΔP) vs. flow rate (Q) relation by considering various air flow rates, leading to a characteristic curve for each passage. The distribution of flow rates and pressure is then determined by FNM through solving 1D mass and momentum conservation equations over the entire flow network.
Technical Paper

A Comparative Analysis of the Thermal Efficiency of 1977 and 1978 Model Year Vehicles Under Chassis Dynamometer Conditions

Comparison of vehicle thermal efficiency and engine load factor for 1977 and 1978 model year certification vehicles shows low correlation. At any load factor, the spread in thermal efficiencies was on the order of 2 to 1. These facts suggest that, with existing technologies, vehicle manufacturers can realize a significant improvement in fuel economy through better matching of engines (specific fuel consumption), transmissions and final drive ratios to vehicle power requirements.
Technical Paper

A Comparative Study on Engine Thermal Management System

As the automotive industry faces tighter fuel economy and emission regulations, it is becoming increasingly important to improve powertrain system efficiency. One of the areas to improve powertrain efficiency is the thermal management system. By controlling how to distribute the heat rejected by the engine, especially during the warm-up stage under cold temperatures, an engine thermal management system can improve the overall energy efficiency of the powertrain system. Conventionally, engine thermal management systems have been operated by a mechanical water pump and a thermostat. However, the recent introduction of electric water pumps and electrically-controlled flow valves allow for more sophisticated control of the thermal management system. In this study, these two different thermal management system architectures are investigated by conducting simulations.
Technical Paper

A Comparison of Model Order Reduction Techniques for Real-Time Battery Thermal Modelling

Battery temperature is known to have a critical influence on overall battery pack performance, from electrochemical behavior, charge acceptance, power availability, trip efficiency, safety, reliability and life-cycle costs. Temperature monitoring is critical to ensure safe and reliable battery pack operation. Monitoring of cell temperatures in battery packs allows for control and estimation algorithms that can ensure homogenous pack temperature distribution, prevent excessive pack temperature rise and even infer cell core temperature, potentially allowing to both predict and mitigate onset of thermal runaway. The increasing need for improved accuracy requires inclusion of more detail in the modelling stage, leading inevitably to ever larger-scale, ever more complex dynamical systems. Simulations in such large-scale settings lead in turn to unmanageably large demands on computational resources, which is the main motivation for Model Order Reduction.
Technical Paper

A Comprehensive CFD Method for Thermal Performance Evaluation of a Scooter Type Motorcycle and Its Application

Thermal management is of vital importance in the development of a scooter type motorcycle (two-wheeler). Traditionally the thermal management development of a two-wheeler is done through experimental methods, or using sub-system level CFD models. In current work, a comprehensive, complete vehicle, three-dimensional CFD model has been developed to assess thermal performance of the scooter and its sub-systems. The model can predict thermal performance in different operating conditions, such as, wide open throttle, idling and key-off. A typical thermal interaction in engine happens through metal contact conduction, air cooling and oil flow path in the engine. The model can capture the sub system interaction, such as, an interaction between the cooling system and engine cabin. Modeling oil is computationally expensive, as it involves complex physics modeling such as multiphase flow.
Technical Paper

A Comprehensive Numerical Approach to Predict Thermal Runaway in Li-Ion Battery Packs

With the increasing level of electrification of on-road, off-road and stationary applications, use of larger lithium-ion battery packs has become essential. These packs require large capital investments on the order of millions of dollars and pose a significant risk of self-annihilation without rigorous safety evaluation and management. Testing these larger battery packs to validate design changes can be cost prohibitive. A reliable numerical simulation tool to predict battery thermal runaway under various abuse scenarios is essential to engineer safety into the battery pack design stage. A comprehensive testing & simulation workflow has been established to calibrate and validate the numerical modeling approach with the test data for each of the individual sub model - electrochemical, internal short circuit and thermal abuse model. A four-equation thermal abuse model was built and validated for lithium-ion 21700 form factor cylindrical cells using NCA cathodes.
Technical Paper

A Computational Study on the Critical Ignition Energy and Chemical Kinetic Feature for Li-Ion Battery Thermal Runaway

Lithium-ion (Li-ion) batteries and issues related to their thermal management and safety have been attracting extensive research interests. In this work, based on a recent thermal chemistry model, the phenomena of thermal runaway induced by a transient internal heat source are computationally investigated using a three-dimensional (3D) model built in COMSOL Multiphysics 5.3. Incorporating the anisotropic heat conductivity and typical thermal chemical parameters available from literature, temperature evolution subject to both heat transfer from an internal source and the activated internal chemical reactions is simulated in detail. This paper focuses on the critical runaway behavior with a delay time around 10s. Parametric studies are conducted to identify the effects of the heat source intensity, duration, geometry, as well as their critical values required to trigger thermal runaway.
Technical Paper

A Cooling System for the EAPU Shuttle Upgrade

The Shuttle orbiter currently uses hydrazine-powered APU’s for powering its hydraulic system pumps. To enhance vehicle safety and reliability, NASA is pursuing an APU upgrade where the hydrazine-powered turbine is replaced by an electric motor pump and battery power supply. This EAPU (Electric APU) upgrade presents several thermal control challenges, most notably the new requirement for moderate temperature control of high-power electronics at 132 °F (55.6 °C). This paper describes how the existing Water Spray Boiler (WSB), which currently cools the hydraulic fluid and APU lubrication oil, is being modified to provide EAPU thermal management.
Technical Paper

A Coupled Lattice Boltzmann-Finite Volume Method for the Thermal Transient Analysis of an Air-Cooled Li-Ion Battery Module for Electric Vehicles with Porous Media Insert Modeled at REV Scales

Lithium ion batteries are the most promising candidates for electric and hybrid electric vehicles, owe to their ability to store higher electrical energy. As a matter of fact, in automotive applications, these batteries undergo frequent and fast charge and discharge processes, which are associated to internal heat generation, which in turns causes temperature increase. Thermal management is therefore crucial to keep temperature in an appropriate level for safe operation and battery wear prevention. In a recent work authors have already demonstrated the capabilities of a coupled lattice Boltzmann-Finite Volume Method to deal with thermal transient of a three-dimensional air-cooled Li-ion battery at different discharging rates and Reynolds numbers. Here, in order to improve discharge thermal capabilities and reduce temperature levels of the battery itself, a layer of porous medium is placed in contact with the battery so to replace a continuum solid aluminum layer.
Technical Paper

A Coupled Lattice Boltzmann-Finite Volume Method for the Thermal Transient Modeling of an Air-Cooled Li-Ion Battery Cell for Electric Vehicles

Due to their ability to store higher electrical energy, lithium ion batteries are the most promising candidates for electric and hybrid electric vehicles, whose market share is growing fast. Heat generation during charge and discharge processes, frequently undergone by these batteries, causes temperature increase and thermal management is indispensable to keep temperature in an appropriate level. In this paper, a coupled Lattice Boltzmann-Finite Volume model for the three-dimensional transient thermal analysis of an air-cooled Li-ion battery module is presented. As it has already been successfully used to deal with several fluid-dynamics problems, the Lattice Boltzmann method is selected for its simpler boundary condition implementation and complete parallel computing, which make this approach promising for such applications.