scholarly journals Reduction of Aerodynamic Drag of Heavy Vehicles using CFD

Author(s):  
Priyank Kothari

Abstract: Aerodynamic drag is the force that opposes an object’s motion. When a vehicle no matter the size, is designed to allow air to move fluidly over its body, aerodynamic drag will have less of an impact on its performance and fuel economy. Heavy trucks burn a significant amount of fuel as to overcome the air resistance. More than 50% of an 18-wheeler’s fuel is spent reducing aerodynamic drag on the highways. Keywords: Aerodynamics, Heavy vehicles, ANSYS, Aerodynamic Drag, Fuel efficiency.

Author(s):  
Madhava R. Madireddy ◽  
Gregory G. Kremer

In conventional vehicles the entire power is derived from the IC engine, so it is obligatory to size the engine larger than necessary for its cruising speed. The engine must be designed to account for peak power requirements like acceleration. This oversizing of the engine shifts the operating point from its efficient zone and this adversely affects the fuel economy and emissions. The idea of hybridization is that a part of the total power required can be replaced by an auxiliary power source, generally a motor powered by batteries. Hence, the IC engine can be designed for average load and can be operated with better fuel efficiency. A simulation tool called ADVISOR (Advanced Vehicular Simulator) is used for this study. The software takes the vehicle input and the drive cycle from the user, simulates the vehicle drive and gives fuel economy, acceleration performance and emissions. In this study, each of the three vehicle platforms (average SUV, full size SUV and heavy truck) is selected and a reasonable power level for that vehicle platform is taken from the data of the current conventional vehicle type. The powertrain is then hybridized by replacing part of the total power by an equivalent motor power and a set of simulations are run in ADVISOR at three different battery charge capacities to understand the effect of on-board charge. A weighted combination of performance and fuel economy results is recorded for each run, and the simulations are then repeated at a higher level of hybridization. The results for a range of “percent hybridization” levels are then evaluated to determine the optimum level. A cost optimization is also done by adding weighted factors based on cost effect of the motor, batteries, and the projected lifetime fuel costs. The penalty due to the weight of the batteries is reflected in the simulated performance and fuel economy of the vehicle, and the space effect of the batteries is also considered. The results of this thesis support the conclusion that parallel hybridization of the drive train could help SUVs and heavy trucks to improve fuel efficiency. Depending on the assumptions made for replacement battery costs and total mileage over the lifetime of the vehicle, the increased initial cost of a hybrid SUV can be justified by the operating cost savings; the benefits of hybridization are even more pronounced for heavy trucks. The “optimum” hybridization percentages are reported for each platform, with and without cost considerations.


Author(s):  
D. Hasen ◽  
S. Elangovan ◽  
M. Sundararaj ◽  
K.M. Parammasivam

Nowadays, fuel efficiency of heavy vehicles became an ultimate issue to the manufacturing and design engineers. The best approach to reduce the fuel consumption is to improve the aerodynamic performance of vehicle. This can be achieved by reducing the drag, because drag coefficient is directly proportional with the fuel consumption. Design engineers trying to improve the heavy vehicle’s performance by manipulating various parameters such as engine parameters, weigh, rolling resistance and aerodynamic drag. In this project, efforts were made to increase the aerodynamic performance by changing the frontal area of the container. Computational analysis was carried out at various velocities (50km/hr, 60km/hr, and 70km/hr) by changing the frontal area of the container in heavy vehicles. Different truck geometries were done using CATIA V5 and the simulations were done using ANSYS CFX software. Results were obtained and comparative studies were made. As a result of comparisons between various designs, the cowl of 2h dimension shows better results in reducing the drag when compared with the other designs.


2021 ◽  
Vol 13 (1) ◽  
pp. 111-117
Author(s):  
Mikhail Podrigalo ◽  
◽  
Volodymyr Krasnokutskyi ◽  
Vitaliy Kashkanov ◽  
Olexander Tkachenko ◽  
...  

Aerodynamic characteristics have a major impact on the energy efficiency and traction and speed properties of the vehicle. In this article, based on previous studies of the aerodynamic characteristics of various car models, we propose an improved method for selecting engine and transmission parameters at the design stage. The aim of the study is to improve the dynamic properties of the car by improving the method of selecting the main parameters of the engine-transmission unit by refining the calculation of aerodynamic drag. To achieve it, the following tasks must be solved: to specify the method of selecting the maximum effective engine power; to specify a technique of definition of the maximum constructive speed of the car; to develop a technique for selecting gear ratios. The aerodynamic resistance to the movement of the vehicle is determined by the frontal coefficient of the specified resistance, the density of the air, the area of the frontal resistance and the speed of the vehicle. It is known from classical works on the aerodynamics of a car that in the range of vehicle speeds from 20 m / s to 80 m / s, taking the law of squares when assessing the force of air resistance, it is necessary to change the coefficient of frontal aerodynamic drag depending on the speed of the car. However, when carrying out calculations, this coefficient is taken constant, which leads to obtaining large values of the air resistance force at high speeds and lower at low speeds. There are two possible ways to improve the dynamic properties and energy efficiency of the car during its modernization (increasing the maximum design speed of the car by reducing the gear ratio in higher gear; reducing the maximum efficiency of the engine while maintaining the previous gear ratio in higher gear). As a result of the study, the method of selection (maximum effective engine power; maximum design speed of the car; gear ratios) at the design stage of the parameters of the motor-transmission unit of the car has been improved.


Author(s):  
W. David Pointer ◽  
Tanju Sofu ◽  
David Weber

The issue of energy economy in transportation has grown beyond traditional concerns over environment, safety and health to include new concerns over national and international security. In collaboration with the U.S. Department of Energy Office of FreedomCAR and Vehicle Technologies’ Working Group on Aerodynamic Drag of Heavy Vehicles, Argonne National Laboratory is investigating the accuracy of aerodynamic drag predictions from commercial Computational Fluid Dynamics (CFD) Software. In this validation study, computational predictions from two commercial CFD codes, Star-CD [1] and PowerFLOW [2], will be compared with detailed velocity, pressure and force balance data from experiments completed in the 7 ft. by 10 ft. wind tunnel at NASA Ames [3, 4] using a Generic Conventional Model (GCM) that is representative of typical current-generation tractor-trailer geometries.


2018 ◽  
Vol 8 (12) ◽  
pp. 2390 ◽  
Author(s):  
Jaehyuk Lim ◽  
Yumin Lee ◽  
Kiho Kim ◽  
Jinwook Lee

The five-driving test mode is vehicle driving cycles made by the Environment Protection Association (EPA) in the United States of America (U.S.A.) to fully reflect actual driving environments. Recently, fuel consumption value calculated from the adjusted fuel consumption formula has been more effective in reducing the difference from that experienced in real-world driving conditions, than the official fuel efficiency equation used in the past that only considered the driving environment included in FTP and HWFET cycles. There are many factors that bring about divergence between official fuel consumption and that experienced by drivers, such as driving pattern behavior, accumulated mileage, driving environment, and traffic conditions. In this study, we focused on the factor of causing change of fuel efficiency value, calculated according to how many environmental conditions that appear on the real-road are considered, in producing the fuel consumption formula, and that of the vehicle’s accumulated mileage in a 2.0 L gasoline-fueled vehicle. So, the goals of this research are divided into four major areas to investigate divergence in fuel efficiency obtained from different equations, and what factors and how much CO2 and CO emissions that are closely correlated to fuel efficiency change, depending on the cumulative mileage of the vehicle. First, the fuel consumption value calculated from the non-adjusted formula, was compared with that calculated from the corrected fuel consumption formula. Also, how much CO2 concentration levels change as measured during each of the three driving cycles was analyzed as the vehicle ages. In addition, since the US06 driving cycle is divided into city mode and highway mode, how much CO2 and CO production levels change as the engine ages during acceleration periods in each mode was investigated. Finally, the empirical formula was constructed using fuel economy values obtained when the test vehicle reached 6500 km, 15,000 km, and 30,000 km cumulative mileage, to predict how much fuel consumption of city and highway would worsen, when mileage of the vehicle is increased further. When cumulative mileage values set in this study were reached, experiments were performed by placing the vehicle on a chassis dynamometer, in compliance with the carbon balance method. A key result of this study is that fuel economy is affected by various fuel consumption formula, as well as by aging of the engine. In particular, with aging aspects, the effect of an aging engine on fuel efficiency is insignificant, depending on the load and driving situation.


Author(s):  
Jukka Isotalo

Roads in Finland are exposed to seasonal strength variation. Because of industrial policy, the maximum weight of heavy trucks is 60 metric tons all year. The policies applied by the Finnish National Road Administration (Finnra) to mitigate the effects of seasonal road strength variations on public roads, and the current research on the topic in Finland, are investigated. It has been estimated that the annual cost of road repairs because of spring damages is about $10 million under the present load restriction policy. The costs for road repairs would be $35 million without restrictions. The annual additional cost for all heavy transport is estimated at $15 million. An internal Finnra survey revealed that $80 million to $100 million is needed to repair all known frost-susceptible road sections. Finnra load restrictions are intended to prevent damage to roads by heavy vehicles during spring thaw. The restrictions will reduce and possibly eliminate increases in annual road maintenance costs. On the other hand, the restrictions will allow a minimum standard for vital transport. Finnra’s Road Structures Research Programme (TPPT) studies improvements in the durability, strength, and economy of road structures. A key part of the TPPT project concerns problems associated with frost, especially durability against frost action. The most important factors of frost action on roads are the freezing index, duration of frost and thaw seasons, surface temperature, and ground water level. Methods for testing and calculating frost effects are discussed, as are the questions that must be answered before more precise models can be published.


Author(s):  
Brandt J. Ruszkiewicz ◽  
Tyler Grimm ◽  
Ihab Ragai ◽  
Laine Mears ◽  
John T. Roth

Increasingly strict fuel efficiency standards have driven the aerospace and automotive industries to improve the fuel economy of their fleets. A key method for feasibly improving the fuel economy is by decreasing the weight, which requires the introduction of materials with high strength to weight ratios into airplane and vehicle designs. Many of these materials are not as formable or machinable as conventional low carbon steels, making production difficult when using traditional forming and machining strategies and capital. Electrical augmentation offers a potential solution to this dilemma through enhancing process capabilities and allowing for continued use of existing equipment. The use of electricity to aid in deformation of metallic materials is termed as electrically assisted manufacturing (EAM). The direct effect of electricity on the deformation of metallic materials is termed as electroplastic effect. This paper presents a summary of the current state-of-the-art in using electric current to augment existing manufacturing processes for processing of higher-strength materials. Advantages of this process include flow stress and forming force reduction, increased formability, decreased elastic recovery, fracture mode transformation from brittle to ductile, decreased overall process energy, and decreased cutting forces in machining. There is currently a lack of agreement as to the underlying mechanisms of the electroplastic effect. Therefore, this paper presents the four main existing theories and the experimental understanding of these theories, along with modeling approaches for understanding and predicting the electroplastic effect.


2013 ◽  
Vol 712-715 ◽  
pp. 2173-2178
Author(s):  
Ping Sun ◽  
Xiu Min Yu ◽  
Wei Dong ◽  
Ling He

Hybrid electric vehicle (HEV) is integrated with the engine, the motor and the battery and so on. HEV has a significantly better fuel efficiency compared with conventional vehicles due to its multiple power sources. To evaluate fuel economy, HEV and its subsystem modeling methodologies were provided through the analysis of energy flow. The Equivalent Consumption Minimization Strategy (ECMS) was built based on the prototype. The ECMS implementation analytical formulation was developed. The equivalency factor, one for charging and the other for discharging, each of them was different during a driving cycle. In a certain drive, only a subset of them generates a trend close to zero, which indicates charge-sustainability.


Author(s):  
Michael E. Iden

U.S. freight railroads produce about 40 percent of freight gross ton-miles while consuming only about 1/20th of the total U.S. diesel fuel1. Compared to heavy-duty trucks, freight railroads have significant energy (and emissions) advantages including the low coefficient of friction of steel wheel-on-rail (compared to rubber tires-on-pavement) and multiple-vehicle trains. However, improved heavy-duty truck technologies are being federally-funded and developed which may create some challenges to freight rail’s long-standing environmental (and economic) advantage in certain transportation markets and corridors. This paper reviews U.S. freight rail fuel efficiency (measured in gallons of fuel per thousand gross ton-miles) from 1920 to 2015, using published records from the former Interstate Commerce Commission (ICC) archived and made available by the Association of American Railroads (AAR). All freight locomotive energy consumption (all types of coal, crude oil, electricity kilowatt-hours and diesel fuel) are converted into approximations of diesel gallons equivalent based on the nominal energy content of each locomotive energy type, in order to show the effect of transitioning from steam propulsion to diesel-electric prior to 1960 and the application of other new technologies after World War II. Gross ton-miles (rail transportation work performed) will similarly be tracked from historic ICC and AAR records. Annual U.S. freight rail fuel efficiency is calculated and plotted by dividing total calculated diesel gallons equivalent (DGe) consumed by gross (and by lading-only net) ton-miles produced. New technologies introduced since 1950 which have likely contributed to improvements in freight rail fuel efficiency (such as introduction of unit coal trains, distributed power, alternating current locomotives, etc) will also be discussed and assessed as to relative contribution to fuel efficiency improvements. The paper includes a discussion about U.S. freight rail fuel efficiency compared to heavy-duty truck fuel efficiency, with comments on projected improvements in heavy-duty truck technologies and fuel efficiency. A conclusion is that U.S. freight railroads and equipment suppliers need to be more aware of projected heavy-duty truck fuel efficiency improvements and their potential for erosion of some aspects of traditional railroad competitiveness. Numerous suggested action plans are discussed, with particular focus on reducing the aerodynamic drag (a delta velocity-squared factor in train resistance and power requirement) of double-stack container trains. Last, this paper discusses possible courses of action for U.S. freight railroads to achieve fuel efficiency improvements greater than the historic ∼1 percent improvement achieved over the past 50 years. If freight rail is to remain economically competitive vis a vis heavy duty trucking, railroads will have to identify, evaluate and implement new technologies and/or new operating practices which can help them achieve fuel efficiency improvements matching (or exceeding) those projected for heavy trucks over the next 7-to-12 years. A specific example for improving fuel efficiency of double-stack container trains is discussed. Failure to address the future of freight rail fuel efficiency is likely not an option for U.S. railroads.


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