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Computational Fluid Dynamic Analysis of

An Air Suspension.

A PROJECT REPORT

Submitted by

  Patel Tirth M.                     (130580119145)

                            

In fulfillment for the award of the degree

                                 Of

   BACHELOR OF ENGINEERING

                                 In

                       MECHANICAL

                                          

INDRASHIL INSTITUTE OF SCINCE AND TECHNOLOGY, RAJPUR

GUJARAT TECHNOLOGICAL UNIVERSITY

October, 2016

INDRASHIL INSTITUTE OF SCIENCE AND TECHNOLOGY

Mechanical Department

2016

CERTIFICATE

                                 Date:

This is to certify that the dissertation entitled “Computational Fluid Dynamic Analysis of An Air Suspension\" has been carried out by Patel Tirth M. (130580119145) under my guidance in fulfillment of the degree of Bachelor of Engineering in 7th Semester of Gujarat Technological University, Ahmedabad during the academic year 2016-17.

Internal Guide: Ms. Niyati Vala

                                                                             

                                                                                      Head of the department

Declaration

        I hereby certify that I am the author of this report and that neither any part of this report nor the whole of the report has been submitted for a degree to any other University or Institution.

I certify that, to the best of my knowledge, my report does not infringe upon anyone’s copyright nor violate any proprietary rights and that any ideas, techniques, quotations, or any other material from the work of other people included in my report, published or otherwise, are fully acknowledged in accordance with the standard referencing practices. Furthermore, to the extent that I have included copyrighted material that surpasses the bounds of fair dealing within the meaning of the Indian Copyright Act, I certify that I have obtained a written permission from the copyright owner(s) to include such material(s) in my report and have included copies of such copyright clearances to my appendix.

I declare that this is a true copy of my report, including any final revisions, as approved by my report review committee.

Date:

Place: Ahmedabad

Sign of Student:    Patel Tirth

Acknowledgement

Foremost, I would like to express my sincere gratitude to my guide Prof. Niyati Vala for the continuous support of my Project study and research, for her patience, motivation, enthusiasm, and immense knowledge. Her guidance helped me in all the time of research and writing of this report. I could not have imagined having a better advisor and mentor for my Project study.

Besides my advisor, I would like to thank to Dr. S. Rajaraman, HOD, Mechanical Engineering department, who gives guidance for the Project work and their insistence for meeting deadlines we can do such excellent work.

I offer my special gratitude to all the faculty members, Mechanical Engineering Department for their help and support. I thank to my friends for providing me such a warm atmosphere to make my study more delightful and memorable.

I would like to express endless gratitude to “My Parents” who gave me everything they could to enable me to reach the highest possible education level. I only hope that they know how their love, support and patience encouraged me to fulfill their dream.

I would like to thank all people who have helped and inspired me during my Report study.

Abstract

Disclosed here is a design of an Air Suspension System which is to be analyzed further, in order to better understand the design and the effects of multi-fluid and multi region system. The Air Suspension System which is being designed here is formulated on the basis of the best known and suitable observations which are carried out to serve its purpose. Basically, the Air Suspension System is used as a replacement for the conventional spring and leaf suspensions as it provides better comfortability, better shock absorbing capacity as well as versatility in spring constants. Since the conventional suspensions are not up to the mark to make the driving safer and secure, air suspension is new way to make this possible. The design is done in advanced 3D modelling software to compensate best results towards the new and the original thing.

LIST OF TABLES

Table No

Table Description

Page No

Table 3.1 List of parts to be required 17

Table 3.2 Sub assembly parts 29

Table 3.3 Final assembly Parts 30

LIST OF FIGURES

Figure No Figure Description Page No

Figure 1.1 Leaf Spring , Helical spring 12

Figure 1.2 Typical Shock Absorber 13

Figure 1.3 Air Suspension System 13

Figure 3.0 Block Diagram 19

Figure 3.1 Air Bladder 20

Figure 3.2 T-connector 21

Figure 3.3 J-connector 22

Figure 3.4 Tyre 23

Figure 3.5 Rims 24

Figure 3.6 Dudukan 25

Figure 3.7 Cover Plate 28

Figure 3.8 Sub assembly-1 29

Figure 3.9 Final assembly 30

Figure 4.1 Empathy mapping canvas 31

Figure 4.2 Ideation canvas 32

Figure 4.3 AEIOU summary 33

Figure 4.4 Product development canvas 35

TABLE OF CONTENTS

Acknowledgement 7

Abstract 8

List of Figures 9

List of Tables 10

Table of Contents 11

Chapter : 1 Introduction 13

1.1 Introduction 13

     1.1.1  Working principle 17

1.2 Project Scope 18

1.3 Project Objective 18

     1.3.1 Stage-1 18

     1.3.2 Stage-2 19

Chapter : 2 Literature review 20

2.1 Literature review 20

2.2 Summary of literature review 21

Chapter : 3 Designing of Air Suspension 22

3.1 Parts to be required 22

3.2 Block diagram 23

3.3 Structural design of Air Suspension 24

     3.3.1 Air Bladder 24

     3.3.2 T-connector 25

     3.3.3 J-connector 25

     3.3.4 Tyre 26

     3.3.5  Rim 27

     3.3.6 Dudukan 27

3.3.7 Cover Plate 28

3.3.8 Assemble 29

Chapter : 4 Design engineering canvas 31

4.1 Empathy mapping canvas 31

    4.1.1 Users 31

    4.1.2 Stakeholders 31

4.2 Ideation canvas 32

4.3 AEIOU canvas 33

4.4 Product development canvas 35

   4.4.1 Product experience 36

   4.4.2 Product function 36

   4.4.3 Product features 36

Conclusion 37

References 38

Chapter 1                                                                             Introduction

1.1 Introduction

Suspension system for vehicle is an integral part of automotive chassis system whereas it can be described as the system that comprise of suspension springs, stabilizers and vibration dampers. Suspension system has been developed during past years with the first type of the suspension known as leaf springs before the coil springs typed gradually being introduced. Suspension system must complete several numbers of tasks which are essential for the overall function of the chassis. These purposes are not only for the ride comfort ability, but definitely for the overall safety of the vehicle. The main goals of having a suspension system in a vehicle aside from improving the ride comfort are to maximize the friction force between the road surface and wheels as well as providing a stable steering and good handling. Plus, Heißing, B. & Ersoy, M. (2010) stated that “this system was intended to mitigate impacts from the road surface”. Absolutely the road conditions are far from perfect for a smooth ride. Bumps and potholes on the roads prompt the wheel to move up and down vertically. In order to control and reduce this, a device known as shock absorber (damper) plays its roles by went through a process called as dampening. Shock absorbers reduce the vibratory motion and slow it down by turning the kinetic energy of vertical movement into heat energy and being dissipated through hydraulic fluid afterward.

Fig. 1.1.1 Leaf springs , Helical Spring

Additionally, the suspension system makes a quite contribution in helping vehicle’s wheel maintain the contact with the roadway as evenly as possible. This is a prerequisite for an effective force transfer between the tires and the road surface, which is essential for road gripping, transfer of power, and braking, all of which are important for overall driving safety.

Basically, there are two important components of suspension which are steel springs and dampers. Steel springs can be categorized into three types; leaf springs, bar springs and helical compression springs (coil springs). Leaf springs were the first type springs used in vehicle suspension as mentioned earlier. Multi-layer leaf springs offer a relatively inexpensive, yet great robust and reliable solution. Today, the combination of conventional leaf springs and a rigid axle can only be found on a small number of passenger vehicles (mainly SUVs). For commercial vehicles, however, leaf springs over other types of springs is that leaf spring not only act as a spring element, but they can also be used as a connecting element between the chassis and the axle and can even control the axle kinematics with respect to the chassis.

Meanwhile, bar spring or simply torsion bar is described as a straight elastic bar with a rectangular or circular cross section that is weighted mainly by a torsion and moment. Torsion bar springs and twisted beams are usually functioned as suspension springs in passenger cars and vans. They can be used in combination with lateral, longitudinal, and semi-trailing suspension arms. Coil springs definitely represent the best idea of spring design for the vertical suspension of a passenger vehicle. Over time, helical springs almost completely replaced leaf springs as the main vertical springing component used in modern vehicles. Unlike the leaf springs, coil spring solely functioning as springing components. Other components must be used to locate the wheel and dampen vibrations.

Damper or widely known as shock absorber is also an important part of suspension. It can be said that suspension is a device that overcomes any unwanted spring motion by slowing down or dampening the vibratory motions. In other words, it turns the kinetic energy of the suspension up and down movement into heat energy that can be released or dissipated through pressurized hydraulic fluid. Generally, shock absorber can be indicated as an oil pump mounted in between car body frame and the wheels. The upper part of the shock absorber is connected to the frame which can be modelled as sprung mass. Meanwhile, the lower part of the shock absorber is connected to the axle, nearby the wheels and can be modelled as unsprang mass.

Fig. 1.1.2 Typical Shock Absorber system

The suspension eventually works when the wheels hits a bump as it compresses the suspension and the kinetic energy is stored in the spring and directly after the wheel pass over the bump, the stored energy earlier wants to flow back and here the damper plays it roles by dissipating the energy. Additionally, shock absorbers work in two loop cycles which are the compression cycle and rebound cycle. During compression, the piston in the shock absorber moves downward compressing the hydraulic fluid in the chamber beneath the piston. Likewise, the rebound cycle takes place when the piston is moved upward to top of pressure tube, compressing the working fluid through valves in the chamber above the piston. Typical passenger cars or lightweight vehicles usually have more resistance during it rebound cycle than its compression cycle.

Most of the modern shock absorbers are sensitive to velocity. Hence, it can be concluded that the faster the suspension moves, the more resistance the shock absorber will behave. So, this makes the shock absorber adjusted to the road conditions and handling all of the undesired motions that can occur in a moving car, including sway, bounce, braking and acceleration.

Air Suspension

When it comes to improve the ride, comfort ability and handling of one’s vehicle, industries have tried everything including the invention of the air suspension. Air suspension actually nearly serves as conventional shock absorber and can be described as a type of suspension that supports the vehicles on the axles and “powered by driven air pump or compressor” (Thiwari, 2009). Instead of having some types of steel spring including leaf, coil or bar spring arrangement, and air suspension is made up of air spring where the compressor pumps the air into a flexible bellows or air bag made from high textile-reinforced rubber.

Fig. 1.1.3 Air Suspension System

1.1.1 Working Principle

In air suspension system, some of the configuration and installation might not be same and varies among the vehicle models depends on the manufacturers, but the underlying principle remains identical. Baxter, E. (2012) visualized that, refer to during the working of the air suspension, the engine-driven air compressor compresses and supplies the air to the air tank which stored compressed air for the future use.

In the air spring, the compressed air is supplied from the air tank to the air bags through the pressurized air lines. Since there is a built-in pressure reservoir present, the flow of the compressed air is equally controlled with solenoid valves. Once the air bag is filled with the air, it compresses leads to an increase in pressure inside the air bag and when the air is prolonged, air will come out of the bellows which make the pressure decreases. These filled and empties mechanism actually determines the riding height of the vehicles. To that end, since there is increasing in vibratory load, the riding height is decreases; the stiffness increases and effective volume are decrease as well. As a result, the effective areas of the air inside air bag increase and lead to increase in load carrying capacity.

Meanwhile, when the vibratory load is reduced, definitely the riding height is increases, the stiffness will reduce and the effective volume will eventually increase. By that, the effective areas are decreases and thus the load carrying capacity is also reduced (Liu H. and Lee J., 2011). In this way, within the effective stroke, the spring height, effective volume and load carrying capacity achieve a smooth flexible transmission occurs with the increase or decrease of the vibratory load, together with the efficient control of amplitude and vibratory load.

In addition, through the increasing and decreasing quantity of air-filling, the spring stiffness and load bearing capacity can be adjusted. It can also be attached to the auxiliary air chamber to achieve self-control.

For the semi active air suspension, there is a valve called Height Control Valve(HCV) mainly functions as kind of brain to the system where it dictate and direct how much the air is in the air bags. Thus, it makes the air bags set the vehicle body at desired height. Meanwhile, the ride height sensors are mounted to the frame of the vehicles to detect the height of vehicle at instantaneous time.

1.2 Project Scope

        In this study, the scopes of the project basically to understand the air suspension by performing several procedures which are:

1. Selecting suitable and standard Air Suspension.

2. Designing of Air Suspension.

3. CFD analysis of the product.

1.3 Project Objectives

The project is being divided into two stages respectively. They are as under:

1. Stage-1

• Study of different Air Suspension models.

• Understanding the different models.

• Selecting the most appropriate and standard model.

• Gathering required dimensions for the model.

• Sketching of the model.

• Part modelling of the Air Suspension.

• Part assembly (virtually) of the Air Suspension.

2. Stage-2

• Learning of the ANSYS.

• Understanding Computational Fluid Dynamics.

• Referencing of the model.

• Creating analytic database.

• Enumerating the equation for the model.

• Analysis of the model.

• Necessary modification and analysing the changes.

• Preparing final report.

Chapter 2                                                                     Literature review

2.1 Literature review

                       In 1999 John Lambert, Arnold McLean and BoHao Li were requested to assist in evaluating a new air suspension developed by Bill Haire, Director of Haire Truck and Bus Repairs Pty Ltd. Initial theoretical considerations by Lambert, and comparisons with standard trailing arm air suspensions revealed that the system had significant merit in overcoming air suspension deficiencies that had been described by drivers of problem prime movers as described in Lambert 2000. Problem vehicles exhibit all or nearly all of:

• Excessive whole body vibration at the driver’s seat,

• Excessive maintenance due to vibration related damage in the broad sense,

• Constant steering input to control wandering, and

• The occurrence of significant divergences from the intended vehicle path without driver input.

A risk assessment was undertaken and tests carried out that determined there were no increased operational risks with the new suspension, and that showed how other risks would be minimised. Whole body vibration, excessive maintenance, wandering and darting have disappeared with fitting of the modified suspension; traction is comparable to mechanical six-rod suspensions; tyre wear is significantly reduced; and brake pad wear is even. This led to further consideration of the theoretical reasons for these improvements, and these are discussed.

JI, Young Chun disclosed is an improved air suspension that prevents damage and/or failure of a component of an air spring, such as an air sleeve. The air suspension includes a damper including a cylinder and a piston rod slidably disposed in the cylinder, an air spring hermetically connected to an outside of the cylinder, an upper mount which secures the damper and the air spring to a vehicle frame, and a rotational sealing part disposed between the air piston and the cylinder and allowing relative rotation of the air spring and the cylinder while maintaining air-tightness between the air piston and the cylinder. The air suspension may prevent damage and/or failure of components of an air spring, such as an air sleeve, by undesired force or moment such as torsional rotational force applied to the air spring in the course of driving the vehicle.

Sunil Laroiya, Gunalan Pallavarasu, Lakshmipathi Ramasamy disclosed an load carrying member for an air suspension system. The load carrying member is a seamless tube comprising a straight mid portion, a left end portion and a right end portion. Each of the left and right end portions are bent or curved with a predetermined radius of curvature so that the said straight mid portion and both the curved left and right end portions form a shape of a cross-section of bath tub. The wall of the tube at the bent portion has thickness which substantially same as the thickness of wall of the straight mid portion. The load carrying member according to the invention not only obviates the problem of frequent failure, but also reduces the number of process steps of manufacturing.

2.2 Summary of literature review

        By the above literature read and to the best of my knowledge I decided to use single bladder cylindrical air suspension module for further formulation and inspection on it.

Chapter 3                                  Designing of Air Suspension System

The designing of Air Suspension system is divided into following parts:

3.1 List of parts to be required

Sr no.

Part name Quantity

1

Steel chassis

1

2

C. I. Axle

2

3 Wheels

4

4

Rims

4

5

Air bladder/bellows 4

6

T- connector 4

7

J- connector

4

8 Cover plates 4

9 Air compressor 1

10 Air tank

1

Table 3.1 Parts to be required

3.2 Block diagram

Figure3.1 Block Diagram

3.3 Structural design of Air Suspension system.

3.3.1 Air Bladder

 Materiel used synthetic reinforced rubber.

 Single bladder type.

                     

Fig. 3.2 Air Bladder

   

3.3.2  T-connector

 One end holding up Air Suspension and other linked to J-connectors.

 Material used in it may be C. I. or steel.

Figure 3.3 T-connector

3.3.3 J-connector:

 They are generally casted and is used in most stressed oriented times.

 It is in a shape of J or lying L.

Figure 3.4 J-connector

  3.3.4  Tyres:

 Number of wheels:4

Figure. 3.5 Tyre

3.3.5 Rims:

 These are made up of stainless steel or sometimes alloys are also used.

 No. of rims: 4

Figure 3.6 Rims

3.3.6  Dudkan:

 Situated inside the rim and rigidly fastened to it.

 Generally made up of hard materials which shows excellent load handling capacity.

Figure 3.6 Dudukan

3.3.7 Cover Plates:

 These are fitted on the back of the dudukan and axle is connected to it on the other surface. They are circular in cross section like any other ordinary plate.

Figure 3.7 Cover plate

3.3.8 Assemble:

1. Sub assembly-1:

This sub assembly includes the parts as follows:

Sr. no. Parts

1. Air Bladder

2. T-connector

3. J-connector

4. Rims

5. Dudukan

6. Cover Plates

7. Tyre

Table 3.2 Sub assembly Parts

Fig. 3.8 Sub assembly-1

2. Final Assembly:

The parts included are:

Sr. no. Parts/Sub-assemblies

1. Sub assembly-1

2. Axle

3. Sub assembly-1(replica)

Table 3.3 Final Assembly Parts

Fig. 3.9 Final Assembly

Chapter 4                                                      Design engineering canvas

            The brief description of design engineering canvas for single stage zigzag ladder is given below.

4.1 EMPATHY MAPPING CANVAS :

                                         Empathy mapping canvas is the first canvas of the design engineering canvases. Which is used to understand the user and the related ethics.

Figure 4.1 Empathy mapping canvas

4.1.1 USERS:  

                    user is a person which whom we are empathically connected and for them we are finding a better solution of their problems. Here is the list is given below of our users.  

• Bus drivers

• Car drivers

• Truck drivers

• Loading vehicles

4.1.2 STAKEHOLDERS:

                                                 The person who are directly or indirectly connected with our users are called as a stakeholders. List of stakeholders is given below.

• Designer

• Management

• Maintenance

• Services

• Production unit

4.2 IDEATION CANVAS :

                                                 

 Ideation canvas helps us to define the problem of our users and to get the idea about the possible solution using different modern technology and props.

Figure 4.2 Ideation canvas

        

   

In the ideation canvas we inspected our users in the different situation and observed the activities during different situations and understand the problems they are facing. Then we had to use the modern technology to find the solution of the same.

4.2 AEIOU SUMMARY:

                             AEIOU Summary consists of research on our user to get the clear vision about the problem in different domains. Which is

• ACTIVITY

• ENVIROMENT

• INTERACTION

• OBSERVATION

• USER

 Figure 4.3 AEIOU summary

4.4 PRODUCT DEVLOPMENT CANVAS:

                                               Product development canvas is simple but powerful tool to develop an innovative product. In this all features components and remarks are included by refining them the best product comes up.

Figure 4.4 Product development canvas

4.4.1 PRODUCT EXPIRIENCCE:

• Better comfort ability

• Great balancing

• Eliminates overturning of vehicle

4.4.2 PRODUCT FUNCTION:

• Lessen vibrations

• Decreases jerks

• Maintaining speed even on rough terrain

• Offers balancing

4.4.3 PRODUCT FEATURES:

• Air Suspension

Conclusion

The study of air suspension is carried out for the reason that it will stimulates the industry to look more into development of this type of suspension. Besides, the designated experimental procedures that later on will be explained throughout this study might help in determining the most important variables that associates with behaviour of air suspension. In this study, the working fluid used in the air spring is simply compressed air. It will be interesting if there is another study that used another form working fluid or gases to perform the dampening process aside from compressed air. The result might be different, but in term of objectives it’s remain identical which is to reduce the vibratory motion. By referring to this study, the experimental procedures will be useful in guiding the further study regarding air suspension. Moreover, this study is focusing only on passive suspension system. For further research and development of air suspension, it will be beneficial by having semi-active air suspension since the main idea, parameter, and variables are similar to this study.

References

1 Journals

I. Air Springs by John Lambert, Arnold McLean and BoHao Li

II. Automotive air suspension by JI, Young Chun

III. Air suspension system by Sunil Laroiya, Gunalan Pallavarasu, Lakshmipathi Ramasamy

2 Websites

[1] Wikipedia

[2] www.ieee.com

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