DESIGN OF INTEGRATED BREATHER VALVE COVER FOR LARGE POWER
ENGINES
Sudhakar Nandam
B.S., Osmania University, Hyderabad, India 2006
PROJECT
submitted in partial satisfaction of
the requirements for the degree of
MASTER OF SCIENCE
in
MECHANICAL ENGINEERING
at
CALIFORNIA STATE UNIVERSITY, SACRAMENTO
FALL
2011
DESIGN OF INTEGRATED BREATHER VALVE COVER FOR LARGE POWER
ENGINES
A Project
by
Sudhakar Nandam
Approved by:
___________________________________________________, Committee Chair
Dr. Dongmei Zhou
____________________________
Date
ii
Student: Sudhakar Nandam
I certify that this student has met the requirements for format contained in the University
format manual, and that this project is suitable for shelving in the Library and credit is to
be awarded for the project.
__________________________, Graduate Coordinator ___________________
Dr. Akihio Kumagai
Date
Department of Mechanical Engineering
iii
Abstract
of
DESIGN OF INTEGRATED BREATHER VALVE COVER FOR LARGE POWER
ENGINES
by
Sudhakar Nandam
“Tier 4 Emission control versus Conventional engine design” is what every design
engineer’s challenge to be dealt with. To design an engine to current market standards
and requirements has become very intricate. In order to make such an explicit design
which meets the standards, every component of the engine plays as a vital role. Every
component design and development to current engineering standards pushes the envelope
of manufacturability to new limits, which constraints the cost of the product across the
ease of manufacturability of it. In consideration of the complexity to be attained, every
component design contributes to the existence of a complete standardized engine, such as
integrated valve cover.
With the new tier 4 final regulations for engine manufactures, every new engine
produced needs to meet those regulations. Caterpillar Inc regulated to produce tier 4
final compatible engines for the market. The new drive for development of new engines
identified the objective of this project to design a new integrated breather valve cover for
large power engines. Valve Cover, the noun by name explains it covers valves. In
explanation to the definition of the valve cover, it covers the cylinder head mechanism;
iv
this is a high speed operating valve. Valve Cover not only covers the head mechanism
and should also be persistent to pressure, stress and heat dissipated during the operation
of the engine. Valve cover design initiates and explains the intricacy of a complete engine
design.
All the functional requirements of valve cover would be designed, analyzed and
validated in this project, that drive the process of execution of the project to several
phases of product development. Process identified for execution initiates with correct
manufacturing technique, design intent and analysis. Caterpillar Inc. Engineering
standards have been taken as a reference for defining all form fit functions. Pro
engineering, Abaqus, Gambit and Fluent are the computer aided design tools used in this
project for the execution of design intent.
Identification of a proper manufacturing technique, processed execution of design
requirements and analysis of concepts of design are validated across the requirements in
this project with a justification of value added solutions are notified in the project.
Conclusion on complete product design of integrated breather valve cover with
optimal solution of all the available techniques in every aspect of design, development
and real time production of valve cover have been discussed in this project,
___________________________________________________, Committee Chair
Dr. Dongmei Zhou
____________________________
Date
v
ACKNOWLEDGEMENTS
I would like to express my heartfelt thanks to Dr. Dongmei Zhou for her guidance and
support in the completion of my project. My project would have never been completed
without her. I would like to thank Mr. Adrian Porojan (Senior Design Engineer,
Axis/Caterpillar Inc.) for guiding me throughout the process of design execution. Also, I
would like to thank Mr. Manmohan Sahoo (Manager Key Account, Axis-Inc.) for
showing the trust in me and giving me the responsibility of handling complex
engineering jobs. Lastly, I would like to thank Department of Mechanical Engineering at
California State University, Sacramento for the encouragement and help to complete my
Master’s in Mechanical Engineering.
Sudhakar Nandam
B.S. Mechanical Engineering
Osmania University, 2006
INDIA
vi
TABLE OF CONTENTS
Page
Acknowledgements….........................................................................................................vi
List of Tables......................................................................................................................ix
List of Figures......................................................................................................................x
Chapter
1. INTRODUCTION, CASTING PROCESS AND MATERIAL SELECTION...........1
1.1 Introduction.............................................................................................................1
1.2 What is a Casting?...................................................................................................1
1.3 Functional Advantages of Castings.........................................................................2
1.4 Economic Advantages of Castings..........................................................................3
1.5 Kinds of Casting Process.........................................................................................3
1.6 What is the Current Casting Process Opted and Why?...........................................4
1.7 Material Assigned and Quality of Product .............................................................4
2. DESIGN INTENT..........................................................................................................6
2.1 Mounting Locations................................................................................................6
2.2 Envelope of Mechanism..........................................................................................8
2.3 Thread Engagement and Hardware.........................................................................9
2.4 Thickness of the Casting and Importance of Profile Tolerance.............................11
2.5 Port Definition.......................................................................................................13
2.6 Channelize The Oil and Air Mixture.....................................................................16
vii
2.7 Seal Design............................................................................................................17
3. ANALYSIS....................................................................................................................20
3.1 Finite Element Analysis of Valve Cover...............................................................20
3.2 Computational Fluid Dynamics.............................................................................24
4. CONCLUSION..............................................................................................................30
4.1 Conclusion.............................................................................................................30
4.2 Future Work...........................................................................................................30
References....................................................................................................................................32
viii
LIST OF TABLES
Page
1. Table 2.1 Caterpillar Engineering STD’s for thread engagement [1]............................10
2. Table 2.2 Caterpillar Engineering Standards for Port Dimensions [1]..........................14
ix
LIST OF FIGURES
Page
1. Figure 1.1 Flow Chart of Casting Process [2]..................................................................2
2. Figure 2.1 Mounting Locations on Engine and Cylinder Head mechanism....................6
3. Figure 2.2 Mounting Locations on Valve Cover.............................................................7
4. Figure 2.3 Front view of the Engine, with Engine Block and Cylinder Head
Mechanism...........................................................................................................................7
5. Figure 2.4 Left Side and Top View of Standard Cover and Cylinder Head Assembly...9
6. Figure 2.5 Cross-sectional View of the Valve Cover for thickness measurement........12
7. Figure 2.6 Comparison across the concepts of Valve Covers.......................................13
8. Figure 2.7 Highlighted feature shows the port of the Valve Cover...............................15
9. Figure 2.8 Port Dimensions of the valve cover..............................................................15
10. Figure 2.9 Tube Assembly and Separator GP[3].........................................................16
11. Figure 2.10 Integrated breather valve cover specification...........................................17
12. Figure 2.11 Seal of the Valve Cover............................................................................18
13. Figure 2.12 Seal profile and Stress corners.................................................................19
x
14. Figure 3.1 Setup for FEA of standard cover................................................................20
15. Figure 3.2 Boundary condition for Normal Mode Analysis........................................21
16. Figure 3.3 Normal mode analysis at 990.5 Hz ............................................................22
17. Figure 3.4 Normal mode analysis at 1110.6 Hz............................................................22
18. Figure 3.5 Normal mode analysis at 1392.0 Hz...........................................................23
19. Figure 3.6 Normal mode analysis at 1798.6 Hz...........................................................23
20. Figure 3.7 Normal mode analysis at 1903.8 Hz...........................................................24
21. Figure 3.8 Initial Setup of the concept valve cover.....................................................25
22. Figure 3.9 Configuration of planes to understand the flow distribution......................26
23. Figure 3.10 Nature of Flow..........................................................................................26
24. Figure 3.11 Flow Distribution across vertical planes..................................................27
25. Figure 3.12 Flow Distribution across Horizontal planes.............................................27
26. Figure 3.13 Pressure Drop...........................................................................................28
27. Figure 3.14 Path lines of flow (Colored basing on particle ID)..................................28
28. Figure 3.15 Recommendation 1...................................................................................29
29. Figure 3.16 Recommendation 2...................................................................................29
1
Chapter 1
INTRODUCTION, CASTING PROCESS AND MATERIAL SELECTION
1.1 Introduction:
With current Tier 4 emission control standards, every new engine built should be built
for improved efficiency, power and performance, long life, reliability, maximized
uptime and reduced cost. Designing an engine to the tier 4 bench marks drove for the
development of a new engine on new scale of market for Caterpillar Inc. every
component has to be redesigned to match requirements of the market. This intention
for building a new engine for new market standards brought this project to existence.
Objective of this project is to design a new valve cover for new engine. In order to
execute several phases of product development the approach to this project is to
stream line one phase at a time like identifying the optimal manufacturing technique,
design intent execution to meet the requirements and analysis for design
improvement.
This project report starts with an introduction to basic concepts and process of
casting. Then the design intents of a valve cover are detained in chapter 2. Stress
analysis and flow distribution are provided in chapter 3. Chapter 4 will draw the
conclusion.
1.2 What is a Casting?
Casting is a manufacturing technique where molten metal is poured into a mold,
which has cavities for the shape to be formed or extracted. Casting is an efficient
technique and very cost effective to other Forming techniques.
2
Casting Technique:
Figure 1.1 Flow Chart of Casting Process [2].
1.3 Functional Advantages of Castings:

Can be quickly turned into a finished part

A series of part numbers making an assembly can be replaced by one casting

Near net shape

Can make complicated geometries

Economical Manufacturing method

Large selection of materials and properties

Suitable for mass production or piecework
1.4 Economic Advantages of Castings:
3

When replacing an assembly with one casting, we save assembly time, handling,
scheduling, inventory, and space.

Reduce machining time (near net shape)

Finished Dollar per kilogram is less than wrought products

Potential for weight savings of the final product
1.5 Kinds of Casting Process:

Sand Casting: It is a casting process in which sand is used as mold, efficient
technique for large size castings, relatively cheap to other casting process, usually
requires a bonding agent to attain the mold. Additional Machining operation is
required for the finish part.

Die Casting: It is a Casting Process where motel metal is forced into a die at high
pressure, this process is usually used avoid additional machining operation. Most die
castings are made for non-ferrous materials.

Permanent Mold Casting: Permanent mold casting is a metal casting process that
shares similarities to both sand casting and die casting. As in sand casting, molten
metal is poured into a mold which is clamped shut until the material cools and
solidifies into the desired part shape. However, sand casting uses an expendable mold
which is destroyed after each cycle. Permanent mold casting, like die casting, uses a
metal mold (die) that is typically made from steel or cast Iron and can be reused for
several thousand cycles.
1.6 What is the Current Casting Process Opted and Why?
4
Sand Casting is the manufacturing technique opted for the production of this Valve
Cover, because the complexity of the part, moderate volume of production, intended
profile tolerance and cost of the product.
1.7 Material Assigned and Quality of Product.
With several considerable materials available, Aluminum Alloy was found to be best
material suitable for this Valve Cover basing on its properties. Ease of mold adhesion,
High strength and Cost effective. Alloy and Temper designation are in accordance
with ANSI H35.1 and H35.1M.
This material is intended to apply to high strength structural aluminum castings with
complex configurations susceptible to high. Unless otherwise noted on the detail
drawing, castings will be made to a Grade C quality level with a Class 3 inspection
frequency requirement. This specification may also be used to procure other Classes
and Grades of Aluminum Association 356.0 aluminum alloy castings. Sections of a
casting may be of varying quality grades depending on the stresses applied to that
portion of a casting. Particular attention should be given to areas that contain, or will
eventually contain, stress risers after machining (such as sharp internal corners, holes
or notches). The heat-treated condition required shall be as shown on the detail
drawing. The inspection Class specified by Engineering Design Control establishes
the test method(s) used to control mechanical property requirements during
production.
5
Chapter 2
DESIGN INTENT
2.1 Mounting Locations:
6
Valve cover is designed to mount and act as shield for cylinder head mechanism;
hence it mounts on the cylinder head. However identifying proper mounting locations
is very critical. As such head directly mounts on the block with high torque bolts. The
new locations identified for the valve cover cannot be heavily torqued considering the
wall thickness of the cylinder head
Figure 2.1 Mounting Locations on Engine and Cylinder Head mechanism.
Basing the on the available mounting area, the additional bosses have been added to
cylinder head at non interfering and have the potential of stress and vibration
absorption. Mounting locations are designed to be symmetric to the best possible
condition, that would ease the machining and fixture design for tooling and assembly
line.
7
Figure 2.2 Mounting Locations on Valve Cover.
In the above Figure 2.2 the encircled locations are the mounting locations for the
Valve Cover. Secondly, the locations are designed to be symmetric to ease the
tooling, machining time and fixture design. Thirdly, time to be spent on assembly line
would be very less compared to asymmetric.
2.2 Envelope of Mechanism:
Intent of Valve Cover is to shield the valve mechanism; hence the casting height
would be an optimal value, by the clearance provided for the Valve mechanism across
the profile tolerance attainable from the casting process. Performing a tolerance stack
up with worst case condition, height of the Valve cover is identified. Below shown
image is the side view of the engine block and cylinder head mechanism which
8
presents a perception of what could be the envelope of mechanism the valve need to
cover.
Figure 2.3 Front view of the Engine, with Engine Block and Cylinder Head
Mechanism
9
Figure 2.4 Left Side view and Top View of Standard Cover and Cylinder Head
Assembly.
Above figure 2.4 shows the envelope of optimal surface surrounded around the
mechanism, which explains the design intent.
2.3 Thread Engagement and Hardware:
Valve Cover being mounted onto cylinder head, there should be enough thread
engagement provided to make sure valve cover seats properly on the cylinder head.
To retain heavy vibrations and high pressure generated under the hood of cover.
Amount of thread engagement justifies what kind of hardware to be used and amount
of torque to be applied. Correct amount of torque signifies the life of the thread and
correct engagement with the cylinder head.
Below table justifies what is the optimal thread engagement value should be provided
on the cylinder head for proper functionality of the valve cover.
10
Table 2.1 Caterpillar Engineering STD’s for thread engagement [1].
With the available Caterpillar engineering standards and from production references
database, the optimal hardware identified for the valve cover is to be M8. Being
cylinder head is mounted on engine block with high torque bolts at 90 Nm; valve
cover could not be mounted at the same value for possible crack propagation on the
casting. Considering this case, the current valve cover is designed to have 45-60 Nm
value of torque for mounting it on to the cylinder head.
11
2.4 Thickness of the Casting and Importance of Profile Tolerance:
Thickness of the casting is very important factor to be considered, higher thickness
value adds weight to the casting and low thickness value results in cracking. To
calculate the optimal value of thickness of casting several parameters needs to be
considered. The maximum pressure the cover has to sustain; weight of the casting and
profile tolerance to be attained on the casting.
Internal pressure in an engine block recorded from lab test engine is 4Kpa around the
crankcase and rest of the block. During the combustion and valve mechanism the
pressure rises exponentially. Empirical value of pressure under the hood of valve
cover is recorded to 30 - 35KPa. Hence the valve cover has to with stand 35Kpa of
pressure on a worst case scenario.
Weight of the valve cover group(that is sum of twelve standard covers and four
integrated covers) is constrained to be 53kg from the global purchasing team at
Caterpillar, this value is identified by reverse engineering from overall weight of the
engine should be for Tier 4 final engines.
Weight of the Integrated Breather Valve Cover: 4.03 Kg
Weight of the Standard Valve Cover: 2.7Kg
Total Weight of the Valve Cover Group: 12 X 2.7 + 4 X 4.03 = 48.52Kg <53 Kg
Thirdly, profile tolerance of a casting is one of the prime factors considered in
designing a casting. As such every casting process has its own limitations in the
amount of profile tolerance it can attain. so, do the sand casting process for the Valve
cover. Valve cover has to be designed in a manner even on the worst case scenario
12
minimum amount of wall thickness should be present. Hence there exists a range of
wall thickness on every casting.
Current casting has 4mm basic wall thickness and 2.5mm minimum wall thickness,
aluminum has excellent properties with respect attaining very good profile tolerance
and blending perfectly with the mold, hence the design of casting has the flexibility to
attain the required thickness.
Figure 2.5 Cross-sectional View of the Valve Cover for thickness measurement
2.5 Port Definition:
The standard design of the valve cover is to only shield, however there are oil fumes
which been produced across the engine are collected by the OCV (Oil Control Valve)
hence a breather is connected to few of the valve covers, on those valve covers need
to have an outlet port, the port definition is defined by the Caterpillar engineering
standards. Initial design of the valve cover for breather input has packaging issues and
13
then a major change has took place for the integrated breather valve cover. This is our
current project, integration phenomena incorporated in the current design to have
additional plastic component where the flow of mixture has been channelized to a
breather.
Figure 2.6 Comparison across the concepts of Valve Covers.
Port dimensions have very close tolerance, because in-correct port dimensions leads to
oil leakages on the breather, which would raise the issues OCV sensor on the engine.
14
Table 2.2 Caterpillar Engineering Standards for Port Dimensions [1]
Above listed table 2.2 shows the dimensioning scheme of the port and what are the
respective dimensions need to be there for respective port sizes as per caterpillar
engineering standards, so do current valve cover port has been dimensioned in
reference to the above table. Figure 2.7 and 2.8 explains the port and its sketch
dimensions.
15
Figure 2.7 Highlighted feature shows the port of the Valve Cover.
Figure 2.8 Port Dimensions of the valve cover
2.6 Channelize The Oil and Air Mixture:
16
Every combustion cycle in an engine and motion of the crank builds up the pressure
in the oil pan as the combustion passes the rings. This pressure fills the block, it must
be removed. If it is not, the pressure build would damage the gaskets in the engine.
Hence, the valve cover should also act as proper channel for the evacuation of
pressure caused by the oil and air mixture. This oil and air mixture is passed to
separator group as shown in Figure 2.9
Figure 2.9 Tube Assemblies and Separator GP [3]
Initial concept designed did not have any mechanism and had large opening for the
breather integration, however, it has packaging issues and breather configuration
17
issues. To avoid these issues an internal integrated design has been developed, where
the flow is controlled and processed.
Figure 2.10 Integrated breather valve cover specification
Figure 2.10 shows the components involved in the integration of valve cover with
breather. Plastic plate creates the channel between its surface and hood of the cover,
which helps the flow of mixture to be streamlined to the separator group.
2.7 Seal Design:
Functional requirement of a seal is to avoid the leaks from the valve cover. Seal on its
own does not have any form; however, it has the fit and function. However, the major
concern in the seal design to make sure seal adheres mating surfaces properly. Figure
2.11 shows the seal on the valve,
18
Figure 2.11 Seal of the Valve Cover.
Seal has been seated in a cast groove; the cross section of the groove is pre-defined as
per caterpillar engineering standards. However the shape of the groove is defined as
per the profile of the mounting surface with few exceptions as stress corners. These
stress corners help the seal to stay in its location at higher frequency of vibrations.
Figure 2.12 shows the seal profile and stress corners.
The highlighted profile in Figure 2.12 is the seal’s profile which follows the profile of
the mating surface with the cylinder head, encircled area on the figure 2.12 shows
stress corners, instead of making a linear design the seal is made to follow a stressed
corners in order to make sure the seal adheres the mating surfaces even at higher
vibrations.
19
Figure 2.12 Seal profile and Stress corners.
Chapter 3
ANALYSIS
20
3.1 Finite Element Analysis of Valve Cover:
Finite element analysis is a computerized technique, where a particular material or
cad model is stressed for specific results. There exists several kinds of phenomena's
in finite element analysis, however normal mode analysis explains the stress the
standard cover is subjected.
This is taken as a reference for analyzing the integrated breather cover.
Figure 3.1 Setup for FEA of standard cover
Standard cover is been mounted on to cylinder head as shown in figure 3.1 the
cylinder head bolts to engine block considered as restrained, by do this we can
understand the stress concentrations of valve cover and cylinder head assembly alone.
Figure 3.2 shows the restrained condition of this assembly with the block.
Cylinder head and valve cover assembly setup is made parametric across few
frequency values and stress concentrations are observed at each frequency.
21
Figure 3.2 Boundary condition for Normal Mode Analysis
Considering restrained is the only boundary condition considered for this setup and
subjected to five frequency parameters.
Resultant stress values across each frequency are listed in the following figures.
22
Figure 3.3 Normal mode analysis at 990.5 Hz
Figure 3.4 Normal mode analysis at 1110.6 Hz
23
Figure 3.5 Normal mode analysis at 1392.0 Hz
Figure 3.6 Normal mode analysis at 1798.6 Hz
24
Figure 3.7 Normal mode analysis at 1903.8 Hz
Figures 3.3 to 3.7 shows the stress concentrations of the valve cover and cylinder
head assembly across different frequencies from these results the areas of the stress
concentrations are controlled with the following model executions, firstly increasing
the casting rounds this would dissolve majority of the stress, secondly by addition of
material if needed and not a preferred technique to avoid weight issue.
3.2 Computational Fluid Dynamics:
Computational fluid dynamics is a computerized simulation of fluid flow to identify
the nature of flow and its effects. All the simulations of CFD are grounded to basic
Fourier transforms and numerical methods bounded by an algorithm to identify the
nature of fluid flow.
25
Concept design of valve cover is analyzed considering the multi phase flow of oil and
air mixture. upon the results of computational analysis location of port for the best
possible results have been identified.
Figure 3.8 Initial Setup of the concept valve cover
Figure 3.8 is the initial concept of integrated valve cover and simulation is performed
on this concept to only understand the nature of flow.
•Mass flow: V12 = 840 cfh (BC1), 1680 cfh (BC2)
V16 = 1120 cfh (BC1), 2240 cfh (BC2)
•Air Inlet Temp: 90 C
•Air Outlet Pressure: 97 Kpa abs
26
BC1 and BC2 are boundary conditions 1 and 2.The above listed values are empirical
extractions of lab test engines.
Figure 3.9 Configuration of planes to understand the flow distribution
Figure 3.10 Nature of Flow
27
Figure 3.11 Flow Distribution across vertical planes
Figure 3.12 Flow Distribution across Horizontal planes
28
Figure 3.13 Pressure Drop
Figure 3.14 Path lines of flow (Colored basing on particle ID)
Figures 3.8 to 3.14 explain the process followed upon computational simulation and
results obtained in each. These results are taken as reference for improving the concept of
integrated breather valve cover into a new design. Figure 3.15 and 3.16 are the
recommendations identified for improving the design of the valve cover and are the
potential solutions for better process flow.
The new valve cover design has been updated to current analysis recommendations
29
Figure 3.15 Recommendation 1
Figure 3.16 Recommendation 2
30
Chapter 4
CONCLUSION
4.1 Conclusion
A new integrated breather valve cover has been designed explicitly to meet tier 4 final
standards. The new valve cover is light in weight, high pressure resistant, best
packaging flexibility and carries an under hood temperature of 120 C. The new
integrated valve cover has a significant interior design to stream line the oil and air
mixture to separator group. This Project gave the opportunity to explore and execute
various phases of design, have been explained and monitored through this project.
This project is processed through several phases of product development concepts
like 1)Manufacturing 2)Design Intent 3)Analysis, validating all three phases to make
sure all the design requirements are met.
The new integrated breather valve cover would be manufactured in year 2012
typically for lab test engines. Basing on the engine performance in the lab any further
improvement would be considered on this design. In year 2014 Caterpillar Inc. would
make this part available upon large power engines which are Tier 4 emission
compatible.
4.2 Future Work:
The current manufacturing technique used for this process is sand casting, however
being an aluminum alloy a permanent mold process would be much more effective
for high volume of production. The current design is not compatible for permanent
mold process. Hence, in future with the estimated volume of demand there exists a
31
scope for design change to make it compatible to be manufactured with permanent
mold process.
32
REFERENCES
1. REDI " Caterpillar Engineering Standards"
2. CLMS " Caterpillar Learning System" Concepts of foundry.
3. Super Model " JT Files for engine validation and assembly"
4. Caterpillar Inc. Large Engines "C175, C270, 3500 and 3600 engine series" referenced
for design development.