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Journal Article

Aerodynamic Investigation of Gap Treatment- and Chassis Skirts Strategies for a Novel Long-Haul Vehicle Combination

2012-09-24
2012-01-2044
Constantly lowering emissions legislation and the fact that fuel prices have increased tremendously over recent years, have forced vehicle manufacturers to develop more and more energy-efficient vehicles. The aerodynamic drag is responsible for a substantial part of the total driving resistance for a vehicle, especially at higher velocities; thus it is important to reduce this factor as much as possible for vehicles commonly operating in these conditions. In an attempt to improve transport efficiency, longer vehicle combinations are becoming more common. By replacing some of the shorter vehicle combinations with longer combinations, the same amount of cargo can be transported with fewer vehicles; hence there is large potential for fuel savings. The knowledge of the aerodynamic properties of such vehicles is somewhat limited, and therefore interesting to study.
Technical Paper

Determining the Vertical and Longitudinal First Mode of Vibration of a Wide Base FEA Truck Tire

2016-04-05
2016-01-1308
The purpose of this study is to determine the effect of tire operating conditions, such as the tire inflation pressure, speed, and load on the change of the first mode of vibration. A wide base FEA tire (445/50R22.5) is virtually tested on a 2.5m diameter circular drum with a 10mm cleat using PAM-Crash code. The varying parameters are altered separately and are as follows: inflation pressure, varying from 50 psi to 165 psi, rotational speed, changing from 20 km/h to 100 km/h, and the applied load will fluctuate from 1,500 lbs. to 9000 lbs. Through a comparison of previous literature, the PAM-Crash FFT algorithmic results have been validated.
Technical Paper

Modeling of Tire-Wet Surface Interaction Using Finite Element Analysis and Smoothed-Particle Hydrodynamics Techniques

2018-04-03
2018-01-1118
This paper focuses on predicting the rolling resistance and hydroplaning of a wide base truck tire (Size: 445/50R22.5) on dry and wet surfaces. The rolling resistance and hydroplaning are predicted at various inflation pressures, loads, velocities, and water depths. The wide base truck tire was previously modeled and validated using Finite Element Analysis (FEA) technique in virtual performance software (Pam-Crash). The water is modeled using Smoothed-Particle Hydrodynamics (SPH) method and Murnaghan equation of state. A water layer is first built on top of an FEA rigid surface to represent a wet surface. The truck tire is then inflated to the desired pressure. A vertical load is then applied to the center of the tire. For rolling resistance tests variable constant longitudinal speeds are applied to the center of the tire. The forces in the vertical and longitudinal directions are computed, and the rolling resistance is calculated.
Technical Paper

Dual Stage Front Underride Protection Devices (dsFUPDs): Collision Interface and Passenger Compartment Intrusion

2014-04-01
2014-01-0567
A performance investigation of Front Underride Protection Devices (FUPDs) with varying collision interface is presented by monitoring occupant compartment intrusion of Toyota Yaris and Ford Taurus FEA models in LS-DYNA. A newly proposed simplified dual-spring system is developed and validated for this investigation, offering improvements over previously employed fixed-rigid simplified test rigs. The results of three tested collision interface profiles were used to guide the development of two new underride protection devices. In addition, these devices were set to comply with Volvo VNL packaging limitations. Topology optimization is used to aid engineering intuition in establishing appropriate load support paths, while multi-objective optimization subject to simultaneous quasi-static loading ensures minimal mass and deformation of the FUPDs.
Technical Paper

A Study on Effects of Low Viscosity Engine Oil and MoDTC on Piston Friction Losses in a DI Diesel Engine

2015-09-01
2015-01-2044
The reduction of friction losses is a subject of central importance in a diesel engine. The piston frictions of low viscosity engine oil and molybdenum dialkyl dithiocarbamate (MoDTC) have been measured by floating liner method. It was found that the low viscosity engine oil lower than 5W-30 is not effective against the reduction of friction mean effective pressure (FMEP) related to the fuel consumption. MoDTC showed a good performance against the reduction of FMEP. In the friction measurement points, the reduction ratio of 10W-30 with MoDTC to 10W-30 was greater than that of 5W-30 to 10W-30.
Journal Article

CFD Simulations of one Period of a Louvered Fin where the Airflow is Inclined Relative to the Heat Exchanger

2015-04-14
2015-01-1656
This article presents Computational Fluid Dynamics (CFD) simulations fo one period of a louvered fin, for a crossflow compact finned heat exchanger, where the incoming airflow was inclined relative to its core. Four inclinations were investigated: 90°, which was when the air flowed perpendicular to the heat exchanger, 60°, 30° and 10° angles relative to the vertical plane. The study included three heat exchanger designs, where two of them had symmetrical louvered fins and a thickness of 19mm and 52mm. The third had a thickness of 19mm and had the louvers angled in one direction. All heat exchangers have been simulated when the airflow entered both from above and below relative to the horizontal plane. Simulations have also been carried out when the airflow entered from the side, illustrating the heat exchanger to be angled relative to the vertical axis. Two air speeds have been investigated for each configuration, where the results were compared to experimental data.
Journal Article

Optimization of an Advanced Combustion Strategy Towards 55% BTE for the Volvo SuperTruck Program

2017-03-28
2017-01-0723
This paper describes a novel design and verification process for analytical methods used in the development of advanced combustion strategies in internal combustion engines (ICE). The objective was to improve brake thermal efficiency (BTE) as part of the US Department of Energy SuperTruck program. The tools and methods herein discussed consider spray formation and injection schedule along with piston bowl design to optimize combustion efficiency, air utilization, heat transfer, emission, and BTE. The methodology uses a suite of tools to optimize engine performance, including 1D engine simulation, high-fidelity CFD, and lab-scale fluid mechanic experiments. First, a wide range of engine operating conditions are analyzed using 1-D engine simulations in GT Power to thoroughly define a baseline for the chosen advanced engine concept; secondly, an optimization and down-select step is completed where further improvements in engine geometries and spray configurations are considered.
Technical Paper

Aeroacoustics of Heavy Duty Truck Side Mirrors - An Experimental Study

2018-06-13
2018-01-1516
Side mirrors are a known source of aerodynamically generated noise in vehicles. In this work we focus on mirrors for heavy duty trucks, they are large, often not designed with main focus on aero-acoustics and are located in a cumbersome position on the up-right A-pillar of European trucks. First the test method itself is discussed. To allow fast and cost effective design loops a bespoke vehicle, where the powertrain is separated from the cab, is developed. This vehicle can be run on a standard test track. While running the tests the wind speed is monitored, any variations are then compensated for in the post processing allowing averaging over longer time periods. For the mirror tests the door of the vehicle was especially trimmed to reduce other transmission paths into the cab than the side window. Additionally other possible aeroacoustic sources were reduced as much as practically possible.
Technical Paper

Analysis of the Effect of Vehicle Platooning on the Optimal Control of a Heavy Duty Engine Thermal System

2019-04-02
2019-01-1259
One promising method for reducing fuel consumption and emissions, particularly in heavy duty trucks, is platooning. As the distance between vehicles decreases, the following vehicles will experience less aerodynamic drag on the front of the vehicle. However, reducing the velocity of the air contacting the front of the vehicle could have adverse effects on the temperature of the engine. To compensate for this effect, the energy consumption of the engine cooling system might increase, ultimately limiting the overall improvements obtained with platooning. Understanding the coupling between drag reduction and engine cooling load requirement is key for successfully implementing platooning strategies. Additionally, in a Connected and Automated Vehicle (CAV) environment, where information of the future engine load becomes available, the operation of the cooling system can be optimized in order to achieve the maximum fuel consumption reduction.
Technical Paper

Impact of Paint Color on Rest Period Climate Control Loads in Long-Haul Trucks

2014-04-01
2014-01-0680
Cab climate conditioning is one of the primary reasons for operating the main engine in a long-haul truck during driver rest periods. In the United States, sleeper cab trucks use approximately 667 million gallons of fuel annually for rest period idling. The U.S. Department of Energy's National Renewable Energy Laboratory's (NREL) CoolCab Project works closely with industry to design efficient thermal management systems for long-haul trucks that minimize engine idling and fuel use while maintaining occupant comfort. Heat transfer to the vehicle interior from opaque exterior surfaces is one of the major heat pathways that contribute to air conditioning loads during long-haul truck daytime rest period idling. To quantify the impact of paint color and the opportunity for advanced paints, NREL collaborated with Volvo Group North America, PPG Industries, and Dometic Environmental Corporation.
Technical Paper

Numerical Investigation of Natural Convection in a Simplified Engine Bay

2016-04-05
2016-01-1683
Presented are results from numerical investigations of buoyancy driven flow in a simplified representation of an engine bay. A main motivation for this study is the necessity for a valid correlation of results from numerical methods and procedures with physical measurements in order to evaluate the accuracy and feasibility of the available numerical tools for prediction of natural convection. This analysis is based on previously performed PIV and temperature measurements in a controlled physical setup, which reproduced thermal soak conditions in the engine compartment as they occur for a vehicle parked in a quiescent ambient after sustaining high thermal loads. Thermal soak is an important phenomenon in the engine bay primarily driven by natural convection and radiation after there had been a high power demand on the engine. With the cooling fan turned off and in quiescent environment, buoyancy driven convection and radiation are the dominating modes of heat transfer.
Technical Paper

On-Board Model Based Diagnosis Based on an Off-Board Engine Simulation Model

2014-04-01
2014-01-0278
This paper presents an approach to fault detection and isolation that is based on off-board 1D simulation tools such as GT-power or AVL Boost. The proposed method enables engineers to develop diagnostic functions early on in a development project. The proposed algorithm is evaluated based on measurements from the air path system of the new Volvo FH truck. The results are encouraging. The paper discusses pros and cons of the method and concludes that it has clear potential to be used for on-board diagnostics.
Technical Paper

A 1D Method for Transient Simulations of Cooling Systems with Non-Uniform Temperature and Flow Boundaries Extracted from a 3D CFD Solution

2015-04-14
2015-01-0337
The current work investigates a method in 1D modeling of cooling systems including discretized cooling package with non-uniform boundary conditions. In a stacked cooling package the heat transfer through each heat exchanger depends on the mass flows and temperature fields. These are a result of complex three-dimensional phenomena, which take place in the under-hood and are highly non-uniform. A typical approach in 1D simulations is to assume these to be uniform, which reduces the authenticity of the simulation and calls for additional calibrations, normally done with input from test measurements. The presented work employs 3D CFD simulations of complete vehicle in STAR-CCM+ to perform a comprehensive study of mass-flow and thermal distribution over the inlet of the cooling package of a Volvo FM commercial vehicle in several steady-state operating points.
Technical Paper

Sleeper Cab Climate Control Load Reduction for Long-Haul Truck Rest Period Idling

2015-04-14
2015-01-0351
Annual fuel use for long-haul truck rest period idling is estimated at 667 million gallons in the United States. The U.S. Department of Energy's National Renewable Energy Laboratory's CoolCab project aims to reduce heating, ventilating, and air conditioning (HVAC) loads and resulting fuel use from rest period idling by working closely with industry to design efficient long-haul truck climate control systems while maintaining occupant comfort. Enhancing the thermal performance of cab/sleepers will enable smaller, lighter, and more cost-effective idle reduction solutions. In order for candidate idle reduction technologies to be implemented at the original equipment manufacturer and fleet level, their effectiveness must be quantified. To address this need, a number of promising candidate technologies were evaluated through experimentation and modeling to determine their effectiveness in reducing rest period HVAC loads.
Technical Paper

Simplifications Applied to Simulation of Turbulence Induced by a Side View Mirror of a Full-Scale Truck Using DES

2018-04-03
2018-01-0708
In this paper, the turbulent flow induced by a production side-view mirror assembled on a full-scale production truck is simulated using a compressible k-ω SST detached eddy simulation (DES) approach -- the improved delayed DES (IDDES). The truck configuration consists of a compartment and a trailer. Due to the large size and geometric complexity of the configuration, some simplifications are applied to the simulation. A purpose of this work is to investigate whether the simplifications are suitable to obtain the reasonable properties of the flow near the side-view mirror. Another objective is to study the aerodynamic performances of the mirror. The configuration is simplified regarding two treatments. The first treatment is to retain the key exterior components of the truck body while removing the small gaps and structures. Furthermore, the trailer is shaped in an apex-truncated square pyramid.
Journal Article

Experimental Investigation of Heat Transfer Rate and Pressure Drop through Angled Compact Heat Exchangers Relative to the Incoming Airflow

2014-09-30
2014-01-2337
This paper presents pressure drops and heat transfer rates for compact heat exchangers, where the heat exchangers are angled 90°, 60°, 30° and 10° relative to the incoming airflow. The investigation is based on three heat exchangers with thicknesses of 19mm and 52mm. Each heat exchanger was mounted in a duct, where it was tested for thermal and isothermal conditions. The inlet temperature of the coolant was defined to two temperatures; ambient temperature and 90°C. For the ambient cases the coolant had the same temperature as the surrounding air, these tests were performed for five airflow rates. When the coolant had a temperature of 90°C a combination of five coolant flow rates and five airflow rates were tested. The test set-up was defined as having a constant cross-section area for 90°, 60° and 30° angles, resulting in a larger core area and a lower airspeed through the core, for a more inclined heat exchanger.
Journal Article

Comparative Studies between CFD and Wind Tunnel Measurements of Cooling Performance and External Aerodynamics for a Heavy Truck

2014-09-30
2014-01-2443
Nowadays, much focus for vehicle manufacturers is directed towards improving the energy efficiency of their products. The aerodynamic drag constitutes one major part of the total driving resistance for a vehicle travelling at higher speeds. In fact, above approximately 80km/h the aerodynamic drag is the dominating resistance acting on a truck. Hence the importance of reducing this resistance is apparent. Cooling drag is one part of the total aerodynamic drag, which arises from air flowing through the heat exchangers, and the irregular under-hood area. When using Computational Fluid Dynamics (CFD) in the development process it is of great importance to ensure that the methods used are accurately capturing the physics of the flow. This paper deals with comparative studies between CFD and wind-tunnel tests. In this paper, two comparative studies are presented.
Journal Article

Force Based Measurement Method for Cooling Flow Quantification

2017-03-28
2017-01-1520
Quantification of heat exchanger performance in its operative environment is in many engineering applications an essential task, and the air flow rate through the heat exchanger core is an important optimizing parameter. This paper explores an alternative method for quantifying the air flow rate through compact heat exchangers positioned in the underhood of a passenger car. Unlike conventional methods, typically relying on measurements of direct flow characteristics at discrete probe locations, the proposed method is based on the use of load-cells for direct measurement of the total force acting on the heat exchanger. The air flow rate is then calculated from the force measurement. A direct comparison with a conventional pressure based method is presented as both methods are applied on a passenger car’s radiator tested in a full scale wind tunnel using six different grill configurations. The measured air flow rates are presented and discussed over a wide range of test velocities.
Technical Paper

Investigation of Interior Noise from Generic Side- View Mirror Using Incompressible and Compressible Solvers of DES and LES

2018-04-03
2018-01-0735
Exterior turbulent flow is an important source of automobile cabin interior noise. The turbulent flow impacts the windows of the cabins to excite the structural vibration that emits the interior noise. Meanwhile, the exterior noise generated from the turbulent flow can also cause the window vibration and generate the interior noise. Side-view mirrors mounted upstream of the windows are one of the predominant body parts inducing the turbulent flow. In this paper, we investigate the interior noise caused by a generic side-view mirror. The interior noise propagates in a cuboid cavity with a rectangular glass window. The exterior flow and the exterior noise are computed using advanced CFD methods: compressible large eddy simulation, compressible detached eddy simulation (DES), incompressible DES, and incompressible DES coupled with an acoustic wave model. The last method is used to simulate the hydrodynamic and acoustic pressure separately.
Technical Paper

Modeling of Closed Fans using CFD and Steady State Assumption of Fluid Flow

2014-09-30
2014-01-2344
Computational Fluid Dynamics (CFD) is today an important tool in the design process of fuel and energy efficient vehicles. Under-hood management is one of the fields where CFD has proven itself to be useful for cost-efficient development of products. Multiple Reference Frame (MRF) method is the most common used tool in the industry for modeling rotating parts. In previous papers, the modeling strategy with MRF has been documented for open fans and showed high capability to predict fan performance. One of the open points of this proposed method has been its applicability to closed fans (ring fans), as industry experience and discussions has indicated previous conclusions of open fans and MRF modeling may not apply across ranges of fan designs. This paper investigates the MRF method for a closed fan with U-shroud and analyzes several aspect of the modeling strategy.
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