AERODYNAMIC IMPROVEMENT OF A TRUCK BODY BY USING CFD

Transcription

1 AERODYNAMIC IMPROVEMENT OF A TRUCK BODY BY USING CFD K. Durga Priyanka #1 and Dr. B. Jayachandraiah *2 #1 M.Tech Student, CAD/CAM, Srikalahasteeswara institute of technology, Srikalahasthi, Chittoor dist, A.P. India *2 Professor and Vice-Principal & Professor, Mechanical Engineering, Srikalahasteewara institute of technology, Srikalahasthi, Chittoor dist, A. P. India. Abstract Now-a-days the reduction of drag coefficient is becoming a very important challenge for all the truck manufacturers. The aerodynamic effects play a role in reducing the coefficient of drag of the vehicle, which may benefits for increasing the fuel efficiency. The exterior design of truck a body is helpful in reducing the drag coefficient which results in reducing the load on the vehicle and low fuel consumption. An attempt is made in this paper identifying the best spoiler for the truck for reduction of drag coefficient by wind tunnel test by using CFD Analysis. Then modeling of the spoiler done by CATIA V5 software and meshed and analyzed by ABAQUS software. The aerodynamic study truck with a cross wind velocity at various speeds. The aerodynamic resistance of the truck and found the coefficient of drag values without any add on and with add on and finally found that with add on helps to increase the fuel efficiency of the truck. Results drawn for pressure and velocity to found drag values. Index Terms Truck, Roof Spoiler, Wind Tunnel test, Abaqus CFD analysis. I. INTRODUCTION Aerodynamics is a branch of fluid dynamics concerned with studying the motion of air around an object, particularly when it interacts with a moving object enables the calculation of forces and moments acting on the object. In aerodynamics problems, the forces acting on the vehicle are lift, drag, thrust and weight. Of these, lift and drag are aerodynamic forces, i.e. forces due to air flow over a solid body. One of the most important aim of the aerodynamic drag reduction researches is to save energy and to protect the global environment, fuel consumption reduction is primary concern of automotive development. Aerodynamic problems are typically solved using fluid dynamics conservation laws as applied to a fluid continuum. Conservation of laws are conservation of mass, conservation of momentum and conservation of energy. These problems are classified by the flow environment or properties of the flow, including flow speed, compressibility and viscosity. Generally classified into external aerodynamics and internal fluid dynamics. External aerodynamics is the study of flow around solid objects of various shapes. Evaluating the lift and drag on an vehicle. Internal aerodynamics is the study of flow through passages in solid objects. For instance, internal aerodynamics encompasses the study of the airflow through a jet engine or through an air conditioning pipe. Aerodynamics is important in a number of applications other than aerospace engineering. It is a significant factor in any type of vehicle design, including automobiles. In this work truck design is to be analysed. In this problem a heavy duty truck was taken and the coefficient of drag was found without any add on devices, that model is treated as the base line model and the same truck with single add on device was run and found the coefficient of drag values. Usually the add on devices helps to reduce the coefficient of drag value. The same trucks with all add on devices and found the coefficient of drag values. In the present work roof spoiler on truck is designed truck is designed in using famous 3D modeling software CatiaV5. Various designs of spoilers are collected from different papers & these are going to be designed using fabulous 3D modeling software CatiaV5. These spoilers are going to be tested by wind tunnel technique in Abaqus software through CFD analysis to validate the efficiency mathematical model. Initial experimental validation of such software is performed using a wind tunnel with the final validation. CFD can be used for a better understanding of wind tunnel tests by using CFD visualization to help understand certain phenomena observed in the wind tunnel tests. Wind tunnel testing was applied to automobiles, not so much to determine aerodynamic forces but more to determine ways to reduce the power required to move the vehicle on roadways at a given speed. In these studies, the interaction between the road and the vehicle plays a significant role, and this interaction must be taken into consideration when interpreting the test results. In an actual situation the roadway is moving relative to the vehicle but the air is stationary relative to the roadway, but in the wind tunnel the air is moving relative to the roadway, while the roadway is stationary relative to the test vehicle. Reducing the drag coefficient in an automobile improves the performance of the vehicle as it pertains to speed and fuel efficiency. There are many different ways to reduce the drag of a vehicle. Mostly, by using spoilers drag is reduced. A spoiler is an automotive aerodynamic device whose intended design function is to 'spoil' unfavorable air 110

2 movement across a body of a vehicle in motion, usually described as turbulence or drag. In the present work by using the famous finite volume technique different cases are going to be tested with different spoilers on the object. Spoilers are meant for aerodynamics which helps to reduce coefficient of drag. The motive of this project is identify the best spoiler for the trucks. Fig1. roof spoiler dimensions II. LITERATURE SURVEY N.T.V.Sainath [1] explains the study the aerodynamic resistance of the truck and found the coefficient of drag values without any add on and with add on and finally found that with add on helps to increase the fuel efficiency of the truck. Here run the CFD analysis over the truck with and with out add on devices a domain was created first according to the dimensions of the truck. The domain plays a major role in the study of the flow analysis which helps to make the continuum. In this problem with the support of pressure, velocity, path lines and coefficient of drag values were found. Richard M. Wood et al, Bauer[2] explains the three simple, low cost aerodynamic drag reduction devices have been developed for application to the trailer of a tractor-trailer truck. This improvement in fuel economy correlates to an equivalent drag reduction of approximately 30% with a corresponding drag coefficient of Richard M. Wood [3] explains four simple, low cost aerodynamic drag reduction devices have been developed for application to the trailer of a tractor-trailer truck. Two vortex flow and two base mounted devices have undergone extensive operational fleet testing where they have amassed over 85,000 miles of use shown a combined fuel savings of 8% at an average speed of 47.5 mph with a corresponding drag coefficient of Christoffer hakansson, Malin j. lenngren [4] explains a recent research about fuel reduction technologies for trucks showed that aerodynamic improvement is one of the most important technologies when it comes to fuel saving. Volvo Trucks has a well established. Different aerodynamic trailer devices and aerodynamically shaped trailers have been tested by means of Computational Fluid Dynamics, in order to investigate their influence on the flow around the truck. Flow transition between the cab, the trailer, the tractor chassis and the trailer undercarriage can be optimized. Kevin Ihlein et la, Kurt Toro [5] explains to reduce the drag force exerted on tractor trailers by modifying the rear of the carrier trailer. Three different design modifications were tested in order to observe and calculate the total drag force reduction. The calculated drag coefficient was comparable to that of a real life model with Reynolds number similarities. Dr. Imad Shukri Ali and Aws Akram Mahmood[6] explains study experimentally and theoretically the effect of changing the aerodynamic shape of a tractor trailer scaled model on its aerodynamic drag and improving its aerodynamic characteristic by using modification added on the trailer body. R. B. SHARMA1 & RAM BANSAL [7] explains the work proposes an effective numerical model based on the Computational Fluid Dynamics (CFD) approach to obtain the flow structure around a passenger car with Spoiler. The addition of spoiler results in a reduction of the drag-coefficient 2.02% and lift coefficient 14.06% in head-on wind. Hence, the drag force can be reduced by using add on devices on vehicle and fuel economy, stability of a passenger car can be improved. III. OBJECTIVE OF PAPER The Objectives of work are: The main objective of this proposal motive of the work is to reduction of coefficient of drag by wind tunnel analysis on truck. Famous finite volume technique different cases are tested with different spoilers on the object. Spoilers are meant for aerodynamics which helps to reduce coefficient of drag. The motive of this project is identify the best spoiler for the truck. CFD analysis is carried for determining the coefficient of drag values with wind tunnel technique. III. MODELLING The heavy duty truck is modeled in using famous 3D modeling software CatiaV5. First the truck is designed without any add on devices. Here the design is included with roof spoilers. some parts are designed with the reference of papers with the help of industrial expert. Fig4.1 Truck model with spoiler Fig 4.2Roof spoiler 111

3 Fig.4.3Truck with wind tunnel model IV. CFD ANALYSIS CFD(computational fluid dynamics), which studies about the fluid dynamics. This is the science which studies about the physical laws of the fluid and various conditions. The flow of fluids can be studied using the support of the computers. Computers are used to perform the calculations required to simulate the interaction of liquids and gases with surfaces defined by boundary conditions. Ongoing research yields software that improves the accuracy and speed of complex simulation scenarios such as turbulent flows. Laminar flow and turbulent flow are two types of fluid flow. Based on Reynolds number (Re) engineers allows to determine whether a flow is laminar or turbulent, but the difference is also evident through observation of its properties. Flows with low Reynolds numbers (less than 10 3 ) are laminar and appear fairly smooth and steady. If a flow has a Reynolds number between 10 3 and 10 4, it cannot be classified as either laminar or turbulent and is called transitional flow. Flows with Reynolds numbers greater than 10 4 are considered turbulent and appear to be rough and unpredictable in nature. Here analysis of the truck model is carried out in Abaqus/CAE with CFD model to validate results. Importing the clean up geometry of the CATIA model as the part and assembling the parts into individual parts and applying property of the material i.e., density and viscosity as 0.7 and 0.3 respectively by taking these parts as a step create a step. 5.1Mesh model of truck Coefficient of Drag defined as the ratio of drag on the body moving through the air to the product of the velocity and the surface area of the body. The drag coefficient is defined as Cd=2Fd/ρV 2 A Where Fd is the drag force, which is by definition the force component in the direction of the flow velocity.ρ is the mass density of the fluid.v is the speed of the object relative to the fluid. A is the reference area. The term coefficient of drag generally relates to aerodynamic effect. The coefficient of drag helps to improve the fuel efficiency of the vehicle. As from the above plots of the pressure velocity and path lines are going to be minimum or maximum due to the contact area of the air with the truck V. RESULTS 6.1 Pressure counters at various speeds The pressure contour at 40 Kmph is as shown in the Figure 6.1 explains that the pressure is maximum at the at the front portion of the truck and this is because that the truck is moving with a 40 Kmph and the cross wind velocity hit the truck at 10 Kmph, the sudden impact of the wind with a certain velocity decreases the velocity and the pressure is increasing, this is clearly evident from the Figure 6.1. The pressure again it becomes minimum at the corners of the face of the truck this is due to the cross curvature, and at the back side of the cabin again the pressure will be the maximum because it hits the load carrier. As shown in the figure 6.2 the pressure value at the front end of the truck was more this is due to the increase in the speed of the truck. The increase in the speed of the truck hits the wind with more speed and due to that sudden impact the pressure values are increasing. At the front end corners the pressure is normal and all this due to the smooth curvature. As shown in the Figure 6.3 again the pressure value is increasing this is due to increase in the speed of the truck as the speed the increases in the truck is dominating the velocity of the truck. That s why the velocity comes down and the pressure gets increased. In this the front portion of the load carrier shows where again the pressure is more when the velocity increases. Mesh the step part with time interval 1 and with mesh size as 50 for truck parts and 100 for wind tunnel part as shown in fig.5.1 Fig.6.1 Pressure contours at 40kmph 112

4 Fig.6.2 Pressue contours at 60 Kmph Fig.6.5Velocity vectors at 60 kmph Fig.6.3 Pressure contours at 80Kmph 6.2 Velocity magnitude for various speeds The velocity vector contour states the direction of the flow of fluid and found where the velocity is more. In general if any object is moving with a certain speed and suddenly hits an object it helps to reduce the speed of the object and disturbs the flow of fluid. In that conditions there may be a chance of reducing the velocity in some places and increases the velocity at other places. This is proved from the Figure 6.4 where the velocity is decreasing and where again it increasing. The velocity of the fluid which is coming at 10 Kmph suddenly hits the truck at the front end, in general the front end it consists of flat area where the contact area is increase and causes for the reduction the velocity and again the velocity is increases at the corners. Fig.6.6 velocity vectors at 80kmph VII. CONCLUSION The above results show the reduction in the coefficient of drag is as shown from pressure, velocity, and coefficient of drag values. In the pressure contours it is observed that without add on devices the pressure is increasing when the truck speed is increased. In the pressure contours with spoiler, states that there is a reduction in the pressure where the spoiler placed, and at the higher speeds the reduction in the pressure is minimum. In the velocity contours it states that the velocity at the sharp ends is high than the flat areas that which states that the cross ends helps to improve the efficiency of the vehicle. All these are happening before add on. After placing the add on device the velocity at that region is starts increasing that means this helps to improve the efficiency of the vehicle. VIII. REFERENCES Fig.6.4 Velocity vectors at 40 kmph [1] N.T.V. Sainath Vehicle Aerodynamics and Thermal Management,2011 [2] Richard M. Wood, Richard M. Wood and Steven X. S. Bauer Simple and Low-Cost Aerodynamic Drag Reduction Devices for Tractor-Trailer Trucks [3] Richard M. Wood A discussion of a heavy truck advanced aerodynamic trailer system. [4] Christoffer hakansson, Malin j. Lenngren CFD analysis of aerodynamic trailer devices for drag reduction of heavy duty, [5] Kevin Ihlein, Kurt Toro, Ryan B.White On Drag Coefficients of Tractor Trailer Trucks 113

5 [6] Dr. Imad Shukri Ali and Aws Akram Mahmood. Improvement of Aerodynamics Characteristic of Heavy Trucks [7] R. B. sharma & Ram Bansal drag and lift reduction on passenger car with rear spoiler ISSN Vol. 3, Issue 3, Aug 2013, [8] Fred Browand, Scott Johnston DOE Project on Heavy Vehicle Aerodynamic Drag, Heavy Vehicle Systems Optimization Program,PP(4-8),2004. [9] Prof. Tamás Lajos Basics of vehicle aerodynamics University of Rome La Sapienza [10] P.M. Van Leeuwen Computational Analysis of Base Drag Reduction Using Active Flow Control November [11] MBH Achen design of tractor for optimised safety and fuel consumption Report August AUTHORS: Dr. B. Jayachandriah Professor and Vice-Principal at Srikalahasteeswara Institute of Technology, Srikalahasti. He has completed his masters in mechanical engineering from BITS Pilani College, specialization in IC Engines. He completed his PhD from JNTUH, Hyderabad specialization in IC Engines CFD. The author has more than 25 years experience in Teaching & research in various subjects of Mechanical Engineering and he has guided about 25 Masters Thesis & number of B.Tech projects. He has credit to 50 publications in various national and International journals and conferences. K. Durga Priyanka M.Tech student at Srikalahasteeswara Institute of Technology, Srikalahasti. Perusing M.Tech 2 nd year CAD/CAM branch with distinction marks. Project done under the guidance of Dr. B. Jayachandriah. 114