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Open Journal of Technology & Engineering Disciplines (OJTED)
Vol. 2, No. 4, December 2016, pp. 166~177
ISSN: 2455-6971
Journal homepage:
http://ojal.us/ojted/
166
ANALYSIS ON THE LEAKAGE OF BRAKE FLUIDS IN MECHANICAL BREAKING
SYSTEM BY USING CFD SOFTWARE
VINOD KUMAR S
GUDURU RAMA KRISHNA REDDY
&
AND RAMACHANDRU
Assistant Professor, Department of Mechanical Engineering, Bharat Institute of
Engineering and Technology, Mangalpally, Hyderabad, Telangana, India.
krishgudur315@gmail.com
Article Info
ABSTRACT
In the Modern world, due to advancement of
technology many high-speed vehicles are invented. In
the present situation with respect to the speed safety is
also a major factor. Mainly, braking systems is the one
which we should be focused to reduce the road
accidents. In order to avoid accidents due to brake
failures, this paper mainly focuses on Analysis of Loss
of pressure in Tandem Master Cylinder due to leakage
of brake fluid through the seals in braking system
which is one of the major reason for the failure of the
brakes in the vehicles, Here We used CFD software for
simulation in order to study the leakage of brake fluid
in the braking system. Here the main aim is to optimize
the leakage of braking fluid so as to ensure the proper
functioning of the brakes. Which helps in the safety of
Passengers.
Copyright © 2015
Open Journal of Technology & Engineering Disciplines
(OJTED)
All rights reserved.
1 INTRODUCTION.
As the project is deals with the study of the leakage behaviour in terms of
reducing pressure due to leakage through the seals in master cylinder, it is necessary to
know about the tandem master cylinder
Open Journal of Technology & Engineering Disciplines (OJTED)
Vol. 2, No. 4, December 2016, pp. 166~177
ISSN: 2455-6971
Journal homepage:
http://ojal.us/ojted/
167
Fig 1.1: Assembly of braking system.
The main part of the hydraulic braking system is the tandem master cylinder. The
function of the tandem master cylinder is to convert the force applied on the brake
pedal in to the hydraulic pressure for the purpose of applying brakes. At the time of the
application of the brakes push rod moves inside the master cylinder. The assembly of
the pistons present inside the tandem master cylinder transfers the brake fluid in to
various brake circuits of the wheels. The above Figure shows the assembly of the
braking system.
As the brake fluid is incompressible after the application of brakes it is supplied to
various connection lines. In order to obtain the proper functioning of the tandem
master cylinder, care should be taken for no air must present inside the brake fluid. As
the air is compressible leads to loss of pressure finally results in the failure of the
braking system in the vehicles.
As the primary and secondary pistons are connected by the spring-loaded
system. When the brake pedal is released then the displaced brake fluid is replaced
from the fluid in the fluid reservoir by the means of the compensating ports. The TMC in
the braking system is shown in below Figure.
Open Journal of Technology & Engineering Disciplines (OJTED)
Vol. 2, No. 4, December 2016, pp. 166~177
ISSN: 2455-6971
Journal homepage:
http://ojal.us/ojted/
168
Fig 1.2: Tandem master cylinder in hydraulic brakes.
1.2 TANDEM MASTER CYLINDER PROBLEMS
The main problems occurring in the tandem master cylinder are leaks (internal
and external) and valve related problems. Leakage of the brake fluid from the rear end
of the master cylinder is not desirable. As it indicates the leakage through the seals.
Even some times the misalignment of the push rod will result in the leakage.
The condition of the worn of master cylinder piston and bore effects the pressure
of brake fluid inside the cylinder. It must check properly. Sometimes the replacement of
master cylinder is done to avoid this problem.
1.3 CAUSES OF BRAKES FAILURE
Increased demand for the speed moving vehicles at the present time had increased
the speed range of the vehicles for the same reason accidents also increased. Some of
the causes for the failure of brakes are listed below
a) In the hydraulic brakes loss of the pressure inside the tandem master cylinder
due to the leakage of brake fluid in the lines of brakes, callipers and brake hose.
This results in the failure of brakes because of not having enough fluid pressure.
b) Brake fluid boiling occurs at the time of accelerating
c) , racing and mountain climbing where the demand for more pressure is required
for producing same effect of friction and braking effect.
d) If piston seals used in tandem master cylinder may get damaged or worn.
Pressure drop will occur after operating the brake pedal.
Open Journal of Technology & Engineering Disciplines (OJTED)
Vol. 2, No. 4, December 2016, pp. 166~177
ISSN: 2455-6971
Journal homepage:
http://ojal.us/ojted/
169
2. LITERATURE REVIEW
Shivashankar S Triwedi et al, [1]
This journal mainly deals with leakage of seals in the tandem master cylinder.
Possible chances of leakages can be happened either by TMC leakage or by the
leakages of seals used in assembly of the piston. Inside the cylinder body acts as
inlet and other side of cylinder considered as throat of nozzle and the mass flow
rate is calculated for leakage in terms of kg/s of brake fluid.
Through Gambit pre-processing operation the creation of geometry along with
the mess generation and specifying the boundary zones are done. Then the method
for solution, properties of materials and operating parameters along with number
of iterations are given in the fluent. Finally, the results are analysed which contains
the value of leakage of the pressure in TMC along with respect to time as results.
Festus Motey[2]
The author describes the leakage of fluid automobile engine oil through the holes,
spaces and cracks, channel among others. Automobile mechanics at siwdo kokampe
in cape coast have learnt and developed different strategies mechanically to solve
the problems of leakages. Metal parts of automobile engines are in contact and
moving resulting to friction and the heat generation.
This journal reveals major causes of oil leakages are due to damage to crown
seals, damaged shaft seal, damaged crank seal and gear box seal.
Ryo akaiwa et al,[3]
This author gives the information about effect of seal profile on tribological
characteristics such as leakage friction, wear in the hydraulic cylinder can be
predicted as a function of depending factors like rod velocity, surface roughness
and frictional force.
Here the finite element analysis was carried out as for sealed pressure (1-20MPA)
and the rod velocities ranging from 0.12 to 0.5 m/s before the leakage was
measured experimentally. After experimental results obtained it is noted the finite
element analysis results are matching with experimental results.
3. PROBLEM FORMULATION AND METHODOLOGY
The project is carried out on the numerical simulation of leakage of the brake
fluid through the seals in the Tandem Master Cylinder. This leads to loss of pressure of
the brake fluid inside the cylinder. As very less work is done in this field. The leakage
source is identified by applying suitable boundary conditions for the meshed
geometry. Due to the leakage of brake fluid through the seals results in the failure of
breaks. The amount of pressure loss can be measured with respect to the time which
results in minimising the brake failure and increasing in productivity.
Open Journal of Technology & Engineering Disciplines (OJTED)
Vol. 2, No. 4, December 2016, pp. 166~177
ISSN: 2455-6971
Journal homepage:
http://ojal.us/ojted/
170
3.1 OBJECTIVES OF THE PROJECT
The main objective of this project is to understand the leakage behaviour of the
seals in the TMC, this helps to avoid the failures and also the production line
fastened as very less time involved in the detection of the leakage. This analysis is
carried by the CFD software of Fluent Ansyss 13 version.
Specific objectives
a) Creating the model and meshing the tandem master cylinder, this is used in the
assembly of the hydraulic cylinder.
b) As the leakage sources are seals, crack on the surface of seal is developed in the
hyper mesh software.
c) Determining the loss of pressure with respect to the time.
d) Conclusions based on the results.
Methodology
a) By the sources of the international journals, research papers the problem of
the project is defined.
b) Data collection: by the parameters which causes for leakage are studied and
analyzed.
c) Modelling and Analysis: after the generation of model, meshing is done then
simulation is done with respect to time.
d) Conclusions and recommendations.
4 MODELLING
4.1 GEOMETRY AND MESHING
The Computational domain of TMC is done initially in the catia model then
exported in to the hyper mesh software, then the mesh of the model is shown in Figure.
Where the complete assembly of the tandem master cylinder is done. then the assembly
of the pistons inside the cylinder is meshed. It shows that the domain was meshed with
tetra cells. During the generation of the mesh triangular elements are created.
Advantage of using tetra cells is to get converging of the solution properly.
Open Journal of Technology & Engineering Disciplines (OJTED)
Vol. 2, No. 4, December 2016, pp. 166~177
ISSN: 2455-6971
Journal homepage:
http://ojal.us/ojted/
171
Fig 4.1 Piston and seals in TMC
4.2 GENERATION OF CRACK
After the generation of the mesh to the model, the next step is to create the crack in
the seal. As the above model inside the cylinder it contains two pistons. The crack is
created to the seal with the diameter of the 0.2mm. It is shown in the Figure
Fig 4.2 Crack in the seal
In the Hyper mesh software separating the collectors is done it means separating
certain collectors from the main model to assign the boundary conditions in the ansys.
For the TMC model separation is done for the collectors such as inlet, wall, fluid and
outlet.
Open Journal of Technology & Engineering Disciplines (OJTED)
Vol. 2, No. 4, December 2016, pp. 166~177
ISSN: 2455-6971
Journal homepage:
http://ojal.us/ojted/
172
5 RESULTS AND DISCUSSION
Fig 5.1 TMC at no leakage of seals
Above Figure 5.1 shows the final diagram obtained by the CFD results which is
showing pressure in the TMC cylinder which is created at no leakage condition of seal.
Red colour brake fluid which is having the same input pressure of 5 bar. It clearly
indicates there will be no pressure loss inside the cylinder without the crack.
Fig 5.2 Leakage behaviour after 1.5 seconds
The Figure 5.2 shows the leakage behaviour of pressure along the seal region where
the pressure lost after 1.5 seconds for 5 bar in the TMC. Variation of the pressure along
the crack region inside the cylinder is indicated by the colour variations. The pressure
Open Journal of Technology & Engineering Disciplines (OJTED)
Vol. 2, No. 4, December 2016, pp. 166~177
ISSN: 2455-6971
Journal homepage:
http://ojal.us/ojted/
173
drop developing from the region near the seal and propagating towards the inside
region of the cylinder.
Fig 5.3 Leakage behaviour after 2 seconds
The Figure 5.3 shows the leakage behaviour of pressure through the seal region
where the pressure lost after 2 seconds for 5 bar in the TMC.
Fig 5.4 Leakage behaviour after 2.5 seconds
The Figure 5.4 shows the leakage behaviour of pressure along the seal region
where the pressure lost after 2.5 seconds for 5 bar in the TMC.
Open Journal of Technology & Engineering Disciplines (OJTED)
Vol. 2, No. 4, December 2016, pp. 166~177
ISSN: 2455-6971
Journal homepage:
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174
Fig 5.5 Leakage behaviour after 3 seconds
The Figure 5.5 shows the leakage behaviour of pressure along the seal region
where the pressure lost after 3 seconds for 5 bar in the TMC.
Fig 5.6 Leakage behaviour after 4.0250 seconds
The above Table 5.1 explains the pressure available inside the region of the
propagation of crack. The loss of pressure is detected in the earlier time of 1.5 seconds
Open Journal of Technology & Engineering Disciplines (OJTED)
Vol. 2, No. 4, December 2016, pp. 166~177
ISSN: 2455-6971
Journal homepage:
http://ojal.us/ojted/
175
inside the cylinder. Further the reduction of the pressure with respect to the time is
shown in the Table 5.2. As the time increases the leakage of the air inside the cylinder
through the seals increases
Fig 5.7 Testing of 5 bar
In the above Figure 5.7 Pressure Vs time is plotted. As the time in seconds is
plotted along X axis and pressure is plotted along Y axis, nature of the curve indicates
the decreasing of the pressure with respect to the time. Due to the leakage of the air
through crack generated on the surface of the seal. It is for the pressure input of 5 bar
inside the cylinder.
Comparison of the results
Pressure in bar
Pressure inside the
cylinder
by experiments [1]
Pressure inside the
cylinder by Ansys
results [1]
Pressure inside
the cylinder by
the project
5
3.78
3.5
3.63
CONCLUSION
Open Journal of Technology & Engineering Disciplines (OJTED)
Vol. 2, No. 4, December 2016, pp. 166~177
ISSN: 2455-6971
Journal homepage:
http://ojal.us/ojted/
176
It is seen without crack in the seal of Tandem Master Cylinder there will be no drop in
the pressure and ensuring of proper functioning of the brakes will be done. In the
further case, it is clear that any crack generated in the seal will results in the creating
the low-pressure region and reduces the efficiency of the braking systems. Loss of
pressure due to leakage with time can be seen in the above results. Finding of detection
done in the 1.5 seconds, it will increase the productivity also.
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Vol. 2, No. 4, December 2016, pp. 166~177
ISSN: 2455-6971
Journal homepage:
http://ojal.us/ojted/
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