Refine Your Search

Topic

Author

Affiliation

Search Results

Technical Paper

Guidelines for SUV Bodywork Design Focused on Aerodynamic Drag Reduction Using the Generic AeroSUV Model

2020-04-14
2020-01-0478
SUV Aerodynamics has received increased attention as the stake this segments holds in the automotive market keeps growing year after year, as well as the direct impact it has on fuel economy. Understanding the key physics in order to accomplish both fuel efficient and aesthetic products is paramount, which indeed gave origin to a major initiative to enhance collaborative aerodynamic research across academia and industry, the DrivAer model. In addition to this sedan-based DrivAer model, a new dedicated SUV generic model, called AeroSUV (Zhang C. T., 2019), has been introduced this year, likewise intended to provide a common framework for aerodynamic research for both experimental and numerical simulation validation. The present work provides an area of common ground for SUV bodywork design focused on minimization of aerodynamic drag making use of the new AeroSUV model in its three available configurations, namely estate back, fastback and notchback.
Technical Paper

Equivalence Factor Calculation for Hybrid Vehicles

2020-04-14
2020-01-1196
Within a hybrid electric vehicle, given a power request initiated by pedal actuation, a portion of overall power may be generated by fuel within an internal combustion engine, and a portion of power may be taken from or stored within a battery via an e-machine. Generally speaking, power taken from a vehicle battery must eventually be recharged at a later time. Recharge energy typically comes ultimately from engine generated power (and hence from fuel), or from recovered braking energy. A hybrid electric vehicle control system attempts to identify when to use each type of power, i.e., battery or engine power, in order to minimize overall fuel consumption. In order to most efficiently utilize battery and fuel generated power, many HEV control strategies utilize a concept wherein battery power is converted to a scaled fueling rate.
Technical Paper

Sensitivity Analysis of Aerodynamic Drag Coefficient to EPA Coastdown Ambient Condition Variation

2020-04-14
2020-01-0666
The test cycle average drag coefficient is examined for the variation of allowable EPA coastdown ambient conditions. Coastdown tests are ideally performed with zero wind and at SAE standard conditions. However, often there is some variability in actual ambient weather conditions during testing, and the range of acceptable conditions is further examined in detail as it pertains to the effect on aerodynamic drag derived from the coastdown data. In order to “box” the conditions acceptable during a coastdown test, a sensitivity analysis was performed for wind averaged drag ((CDW ) ̅) as well as test cycle averaged drag coefficients (CDWC) for the fuel economy test cycles. Test cycle average drag for average wind speeds up to 16 km/h and temperatures ranging from 5C to 35C, along with variation of barometric pressure and relative humidity are calculated. The significant effect of ambient cross winds on coastdown determined drag coefficient is demonstrated.
Technical Paper

VIRTUAL METHOD FOR ELECTRONIC STOP-START SIMULATION & VDV PREDICTION USING MODIFIED DISCRETE SIGNAL PROCESSING FOR SHORT TIME SIGNALS

2020-04-14
2020-01-1270
Electronic Stop-Start (ESS) system automatically stops and restarts the engine to save energy, improve fuel consumption and reduce emissions when the vehicle is stationary during traffic lights, traffic jams etc. The start and stop events cause unwanted vibrations at the seat track which induce discomfort to the drivers and passengers in the vehicle. These events are very short duration events, usually taking less than a second. Time domain analysis can help in simulating this event but it is difficult to see modal interactions and root cause issues. Modal transient analysis also poses a limitation on defining frequency dependent stiffness and damping for multiple mounts. This leads to inaccuracy in capturing mount behavior at different frequencies. Most efficient way to simulate this event would be by frequency response analysis using modal superposition method.
Technical Paper

Assessing the Impact of Lubricant and Fuel Composition on LSPI and Particulate Emissions in a Turbocharged Gasoline Direct Injection Engine

2020-04-14
2020-01-0610
Downsized turbocharged gasoline direct-injection (TGDI) engines with high specific power and torque can enable reduced fuel consumption in passenger vehicles while maintaining or even improving on the performance of larger naturally aspirated engines. However, high specific torque levels can lead to abnormal combustion phenomena such as knock and Low Speed Pre-Ignition (LSPI). LSPI, in particular, can limit further downsizing due to resulting and potentially damaging mega-knock events. Here, we characterize the impacts of lubricant and fuel composition on LSPI frequency in a TGDI engine while specifically exploring the correlation between fuel composition, particulate emissions, and LSPI events. Our research shows that oil composition has a strong impact on LSPI frequency and that LSPI frequency can be reduced through a carefully focused approach to lubricant formulation.
Technical Paper

Numerical Evaluation of Gasoline Compression Ignition at Cold Conditions in a Heavy-Duty Diesel Engine

2020-04-14
2020-01-0778
Achieving robust ignitability for compression ignition of diesel engines at cold conditions is traditionally challenging due to insufficient fuel vaporization, heavy wall impingement, and thick wall films. Gasoline compression ignition (GCI) has shown good potential to offer enhanced NOx-soot tradeoff with diesel-like fuel efficiency, but it is unknown how the volatility and reactivity of the fuel will affect ignition under very cold conditions. Therefore, it is important to investigate the impact of fuel physical and chemical properties on ignition under pressures and temperatures relevant to practical engine operating conditions during cold weather. In this paper, 0-D and 3-D computational fluid dynamics (CFD) simulations of GCI combustion at cold conditions were performed.
Technical Paper

EXV to Optimize PHEV/BEV automotive air conditioning system performance and simulation methodology

2020-04-14
2020-01-1393
Due to increasing standards in fuel consumption, battery electric vehicles (BEV) and plug in electric hybrid vehicles (PHEV), are becoming more commonplace in the automotive industry. Batteries used in such applications require methods of thermal management to promote longer life, higher efficiency and performance. A common method of keeping the battery cool, in high heat conditions, is to use a water to refrigerant chiller. The already existing automotive air conditioning system is leveraged to enable the use of such a chiller. The added thermal transient load of the battery adds complexity to the refrigeration system. Balancing the thermal comfort of the occupants with temperature requirements of battery drives challenges to the overall system capacity. The sudden change in battery cooling loads can noticeably degrade the evaporator heat rejection. In extreme cases the battery cooling load can cause complete loss of refrigerant flow to the evaporator.
Technical Paper

A Vehicle Level Transient Thermal Analysis of Automotive Fuel Tanks

2020-04-14
2020-01-1342
Maintaining the fuel temperature and fuel system components below certain values is an important design objective. Predicting these temperature is therefore one of the key parts of the vehicles thermal management process. One of the physical processes affecting fuel tank temperature is fuel vaporization, which is controlled by the vapor pressure in the tank, fuel composition and fuel temperature. Models are developed to enable the computation of the fuel temperature, fuel vaporization rate in the tank, fuel temperatures along the fuel supply lines, and follows its path to the charcoal canister and into the engine intake. For Diesel fuel systems where a fuel return line is used to return excess fluid back to the fuel tank, an energy balance will be considered to calculate the heat added from the high-pressure pump and vehicle under-hood and underbody.
Technical Paper

Axle Efficiency Comparison Method and Spin Loss Benefit of Front Axle Disconnect Systems

2020-04-14
2020-01-1412
There are a variety of test protocols associated with vehicle fuel economy and emissions testing. As a result, a number of test protocols currently exist to measure axle efficiency and spin loss. The intent of this technical paper is to describe a methodology that uses a singular axle efficiency and spin loss procedure. The data can then be used to predict the effects on vehicle FE and GHG for a specific class of vehicles via simulation. An accelerated pre-conditioning method using a comparable energy approach has been developed, and can be used to meet the pre-conditioning requirements of different vehicle emission test protocols. A “float to equilibrium” sump temperature approach has been used to produce instantaneous efficiency data, which can be used to more accurately predict vehicle FE and GHG, inclusive of Cold CO2. The “float to equilibrium” approach and “fixed sump temperature” approach has been compared and discussed.
Technical Paper

Rear Axle Heat Exchanger Utilization of Engine Coolant for Reduced CO2 Emissions and Fuel Consumption

2020-04-14
2020-01-1411
This paper describes the design, development, and operation of a rear axle dual-shell heat exchanger on a RAM 1500 Light Duty truck. This system has been proven to increase fuel economy and reduce exhaust emissions, particularly CO2 on the EPA Cold City schedule. Through heat transfer math models, the energy conversion strategy will be explored. A PUGH analysis associated with concept selection is included. To refine the hardware and develop a control strategy prior to testing, a portable flow cart was developed to assess system performance and to correlate the multi-node heat transfer model. Bench testing focused on the durability and functional aspects of integrating the dual-shell axle cover with the axle and coolant delivery system through a comprehensive design and validation plan. Vehicle testing included various fuel economy and emissions related driving schedules to quantify the benefits.
Technical Paper

Longitudinal Vehicle Dynamics Modeling for AWD/4WD Vehicles to study torque split between front and rear axles.

2020-04-14
2020-01-1410
All-wheel Drive (AWD) is a mature technology and most automobile manufacturers offer this feature on their vehicles. Improved traction, enhanced vehicle stability, and better handling are some of the key characteristics of AWD vehicles which are achieved by distributing appropriate level of torque to the front and rear axles. Accurately capturing the torque split between the two axles is essential for sizing of driveline components like gears, bearings, and shafts. Traditionally, the torque split is considered to be either 50-50%, or solely proportional to the static weight distribution between the two axles. Design decisions are made based on historical test data. In this paper longitudinal vehicle dynamics model for AWD systems is proposed to understand the influence of various key factors such as dynamic weight transfer, compliance of driveline components, changing tire radius, and tire pressure on the torque split.
Technical Paper

A Case Study on Reducing the Fuel Pulse Noise from Gasoline Engine Injectors

2020-04-14
2020-01-1276
Vehicle NVH performance is a very important consideration for vehicle buyers in the marketplace. There are many noise sources from the fuel system to generate noise in a vehicle. Among them, the pressure pulsations due to the rapid opening and closing of gasoline engine injectors can cause undesirable fuel pulse noise inside the vehicle cabin. As the pressure pulsation propagates in the fuel supply line toward to rear end of the vehicle, the pressure energy is transferred from fuel lines to the vehicle underbody through clips and into the passenger compartment. It is crucial to attenuate the pressure pulsation inside the fuel line to reduce the fuel pulse noise. In this paper, a case study on developing an effective countermeasure to reduce the objectionable fuel pulse noise of a V8 gasoline injection system is presented. First, the initial interior noise of a prototype vehicle was tested and the objectionable fuel pulse noise was exhibited.
Technical Paper

Robust xEV Battery State-of-Charge Estimator Design using Deep Neural Networks

2020-04-14
2020-01-1181
The battery state-of-charge (SOC) is crucial information for the vehicle energy management system and must be accurately estimated to ensure more reliable and affordable electrified vehicles (xEV). However, due to the nonlinear, temperature, health, and SOC dependent behaviour of Li-ion batteries, SOC estimation is still a significant automotive engineering challenge. Traditional approaches to this problem, such as electrochemical models, usually require precise parameters and knowledge from the battery composition as well its physical response. In contrast, neural networks are a data-driven approach which requires no prior detailed knowledge of the battery or its nonlinear behaviour. The objective of this work is to walk through the design process to create a SOC estimator using deep feedforward neural networks (DNN).
Technical Paper

Combustion System Optimization of a Light-Duty GCI Engine Using CFD and Machine Learning

2020-04-14
2020-01-1313
In this study, the combustion system of a light-duty compression ignition engine running on a market gasoline fuel with Research Octane Number (RON) of 91 was optimized using computational fluid dynamics (CFD) and Machine Learning (ML). The focus of this study was to optimize the piston bowl geometry at two compression ratios (CR) (17 and 18:1) and this exercise was carried out at full-load conditions (22bar indicated mean effective pressure (IMEP). CAESES, a commercial software tool, was used to automatically perturb key bowl design parameters and CONVERGE software was utilized to perform all CFD simulations. 128 piston bowl designs were evaluated at each compression ratio. Subsequently, a Machine Learning-Grid Gradient Algorithm (ML-GGA) approach was developed to further optimize the piston bowl design. This extensive optimization exercise yielded significant improvements in the engine performance and emissions compared to the baseline piston bowl designs.
Technical Paper

Battery Entropic Heating Coefficient Testing and Use in Cell-level Loss Modeling for Extreme Fast Charging

2020-04-14
2020-01-0862
To achieve an accurate estimate of losses in a battery it is necessary to consider the reversible entropic losses, which may constitute over 20% of the peak total loss. In this work, a procedure for experimentally determining the entropic heating coefficient of a lithium-ion battery cell is developed. The entropic heating coefficient is the rate of change of the cell’s open-circuit voltage (OCV) with respect to temperature; it is a function of state-of-charge (SOC) and temperature and is often expressed in mV/K. The reversible losses inside the cell are a function of the current, the temperature, and the entropic heating coefficient, which itself is dependent on the cell chemistry. The total cell losses are the sum of the reversible and irreversible losses, where the irreversible losses consist of ohmic losses in the electrodes, ion transport losses, and other irreversible chemical reactions.
Technical Paper

Sensitivity Analysis of Coastdown Test Cycle Averaged Drag Coefficient for Several Functions of Drag Coefficient vs. Speed

2020-04-14
2020-01-0663
Aerodynamic testing for predicting fuel economy effects is typically done at EPA nominal ambient conditions, with nominal ‘2 Pass’ vehicle attitude. Essentially, the EPA standard coastdown is simulated in the wind tunnel. This predictive model is typically used well in advance of production manufactured vehicles, when prototype models are used for wind tunnel testing. However, in reality the actual loading of the vehicle due to manufacturing tolerances, changes in ride height with test loading, and the change in drag coefficient CD with speed, results in some variation in the vehicle CD during a coast down test. By testing the prototype vehicle on track with ride height sensors and at several ride height variations in the wind tunnel, a mathematical model can be used to predict the coast down speed effects on aerodynamic drag.
Technical Paper

EGR distribution in an Intake Manifold: Analysis, Dynamometer Correlation and Prediction

2020-04-14
2020-01-0840
Every passing year automotive engineers are challenged to attain higher fuel economy and improved emission targets. One widely used approach is to use Cooled Exhaust Gas Recirculation (CEGR) to meet these objectives. Apart from reducing emissions and improving fuel economy, CEGR also plays a significant role in knock mitigation in spark ignited gasoline engines. Generally, CEGR is introduced into the intake manifold in SI gasoline engine. Even though the benefits of using CEGR are significant, they can be easily negated by the uneven CEGR flow distribution between the cylinders, which can result in combustion instability. This paper describes the application of co-simulation between one and three dimensional tools that accurately predict the distribution of CEGR to the cylinders and the effect of its distribution on engine performance.
Technical Paper

Detailed Analysis of U.S. Department of Energy Engine Targets Compared To Existing Engine Technologies

2020-04-14
2020-01-0835
The U.S. Department of Energy, Vehicle Technologies Office (U.S. DOE-VTO) has been developing more energy-efficient and environmentally friendly highway transportation technologies that would enable the United States to burn less petroleum on the road. System simulation is an accepted approach to evaluate the fuel economy potential of advanced (future) technology targets. U.S. DOE-VTO defines the targets for advancement in powertrain technologies (e.g., engine efficiency targets, battery energy density, lightweighting, etc.) Vehicle system simulation models based on these targets have been generated in Autonomie, to reflect the different EPA classifications of vehicles for different advanced timeframes as part of DOE Benefits and Scenario Analysis (BaSce). It is also important to evaluate the progress of these component technical targets compared to existing technologies available in the market.
Technical Paper

Design of Valve Body Integrated Direct Acting Control Solenoids

2020-04-14
2020-01-0965
This paper studies the latest trend in transmission hydraulic controls development which involves the integration of the solenoid hydraulic element into the hydraulic valve body and attaching the magnetic part of the solenoid to the assembled valve body. This practice has been adopted by multiple automotive OEMs. Integrated direct acting control solenoids are key enablers for OEMs to meet more stringent fuel economy requirements in competitive environments. In the meantime, there are unique challenges in both integration and packaging due to the limited useful stroke of the armature and the fact that the solenoid armature can only act upon the spool valve in an outward motion. Both normally low and normally high functionality can be achieved with direct acting solenoids, but there are more challenges for the normally high functionality, especially spool valve porting and high hysteresis.
Technical Paper

Impact of Active-Grille Shutter Position on Vehicle Air-Conditioning System Performance and Energy Consumption in Real World Conditions

2020-04-14
2020-01-0947
Active grille shutter (AGS) in a vehicle provides aerodynamic benefit at high vehicle speed by closing the front-end grille opening. At the same time, this causes lesser air flow through the cooling module which includes the condenser. This results in higher refrigerant pressure at the compressor outlet. Higher head pressure causes the compressor to work more thereby possibly negating the aerodynamic benefits towards vehicle power consumption. This paper uses a numerical method to quantify the power consumed by the vehicle in different scenarios and assesses the impact of AGS closure on vehicle energy consumption. The goal is to analyze the trade-off between the aerodynamic performance and the compressor power consumption at high vehicle speeds and mid-ambient conditions. These so called real world conditions represent high way driving at mid-ambient temperatures where the air-conditioning (AC) load is not heavy.
X