Optimization of Exhaust Valve

The assignment content discusses the design and analysis of an exhaust valve in a diesel engine. The valve has an air cavity that reduces its weight by 17%. The thermal stress analysis shows that the valve is subjected to a maximum stress of 24.43 MPa due to temperature changes between 578 K and 588 K. The finite element analysis (FEA) software ANSYS was used for the analysis. The results show that the valve's deformation, heat flux, and stress are reduced after optimization. The optimized design reduces the valve's weight by 17% while maintaining its strength. The analysis also suggests that the valve's design can be further optimized to reduce material usage and costs.

EXHAUST VALVE
DESIGN AND OPTIMIZATION OF ENGINE EXHAUST VALVE

EXHAUST VALVE
ABSTRACT
Exhaust valve is a significant engine component that expels the exhaust
gases that are produced after fuel combustion, out. Any flaws in the exhaust valve
design, affects the overall performance and reliability indirectly and directly, so, it
fails, before its intended function and performance and result in poor running
conditions of the engine. Exhaust valves are failed faster than that of the intake,
because of the higher thermal stress of the exhaust valve. Hence, it needs to be
very carefully designed, without any possible flaws. Finite element technique is
used through vibration testing and analysis of performance.

EXHAUST VALVE
Contents
DESIGN AND OPTIMIZATION OF ENGINE EXHAUST VALVE.................................6
INTRODUCTION...............................................................................................................6
ENGINE EXHAUST VALVE.............................................................................................6
DESIGN ANALYSIS...........................................................................................................6
NUMERICAL METHOD....................................................................................................7
FINITE ELEMENT METHOD...........................................................................................8
FINITE ELEMENT SIMULATION WITH ANSYS WORKBENCH................................9
Specifications...............................................................................................................................9
Heat Flux and Structural Stress Calculated Theoretically.........................................................11
DESIGN OF LIGHT WEIGHT VALVE WITHOUT AFFECTING
PROPROERTIES...................................................................................................................11
FINITE ELEMENT ANALYSIS.......................................................................................12
RESULTS OF ANALYSIS................................................................................................13
OPTIMIZATION AFTER ANALYSIS..............................................................................14
RESULTS OF ANALYSIS AFTER OPTIMIZATION.....................................................15
CONCLUSION..................................................................................................................15
REFERENCES..................................................................................................................15

EXHAUST VALVE

EXHAUST VALVE
DESIGN AND OPTIMIZATION OF ENGINE EXHAUST VALVE
INTRODUCTION
The paper is aimed to design, analysis and optimization of the exhaust valve
of an engine. The design has performed the theoretical calculations and also
automated calculations, through the design and analysis done, in the ANSYS
Workbench, by performing the finite element analysis and method. The method
makes use of the AutoCAD designs.
ENGINE EXHAUST VALVE
Exhaust valves are designed with the objective to allow escaping of the
exhaust gases, into the exhaust manifold, in internal combustion engines.
The valve stands as the quite significant part of the engine valve mechanism
and determines the overall service life and structural strength, when considered
working with higher temperatures. Hence, it influences the overall engine
performance. Since, it works under the environment of higher pressure and
temperature, frequently, it has to bear not only various mechanical loads, like
cylinder gas pressure, valve spring elastic and friction forces and reciprocating
inertia forces, but also by the thermal load, when worked in increased temperature
(Deng, et al. 2014).
DESIGN ANALYSIS
Since, the practical design and analysis in physical terms demands more
time, efforts and money, all of them can be saved to a great extent, when the engine
exhaust valve is designed with software, preferably, AutoCAD and Ansys
Workbench.

EXHAUST VALVE
An analysis of design against its performance and failure are carried out with
various analysis and the analysis is done over the gasoline engine valve. It has been
observed and shown that the material hardness and microstructure, through
scanning, by the electron microscope and performing thermal deformation, in
terms of coordinate measuring machine. The tests have shown the failure of valve,
because of the mechanical bending force, because of the valve shift misalignment
and because of thermal deformation. Other tests conducted have shown the results
of analysis of failure as initiation of the cracks, from the valve shaft outer surface
and propagating towards inner part of the surface. Other fractographic study
conducted on the valve shows the decomposition of the matrix and formation of
the lamellar structure that has ΎCr23 C6 that influence and decrease the harness,
toughness, valve plate material gas corrosion resistance, all resulting towards
exhaust valve failure. Overheating of valve occurred because of the extensive
surface oxidation, galling or fretting of the valve have resulted in significant loss of
hardness. Valve also gets affected from the stress that is increased due to closing
acceleration, valve train dynamics and combustion temperature and pressure (Jeff,
et al. 2014). Temperature gradient, such as near to seat face, thermal stress etc.,
would increase the stresses and fails the valve, in its head area and result in
traversal cracks.
NUMERICAL METHOD
Valve drawing is done through CATIA model and then converted to .igs file
and then the file is imported to the ANSYS Workbench. Then meshing is done for
the model. The physical and mechanical properties of the material used for the
valve are to be entered in the engineering data. The mesh has to represent the
component geometry, accurately, especially, in the critical areas and here stress is a
vital factor (Sagar et al., 2015).

EXHAUST VALVE
Option loads are used for applying the force and the support is fixed,
through the option displacement. Once the supports and forces are applied
selection of the von misses to be done, through the option, stresses and solution is
obtained, based on the parameters given in the engineering data, after clicking on
the solve button.
FINITE ELEMENT METHOD
ANSYS along with the Finite Element Method and Application help to
obtain the knowledge of both theoretical and practical, along with the necessary
skills for engineering problems analysis. The analysis can better be done with the
adopton of the APDL (ANSYS Parametric Design Language) and GUI (Graphical
User Interface). Using the FEM, practical modeling of the machines and
components, such as engine exhaust valve can be done with practical
considerations, of various parameters of the components. For example, the
problems related to the engine exhaust valve moisture diffusion, heat transfer and
nonlinear structural problems can be explored. Additionally, sub-structuring, sub-
modeling, capability of interaction with the external files are offered.
Exhaust valves can be designed virtually, analyzed and optimized for better
performance. The design of the values consider various factors, like material
strength, fatigue life, temperature and manufacturing processed, so that they can be
operated without premature failure. Studies have explored the better material used
for the valves for better material strength and can provide stronger valves with
lesser cost and lesser weight, such as Nimonic 105 A and Magnesium Alloy.
Deisgn of the valve through modifying the exhaust valve, through varying the
shape, position and certain considerations, like structural and thermal
considerations, can increase the heat transfer rate from the exhaust valve seat
portion, so that possibility of knocking can be reduced. Finite element analysis can

EXHAUST VALVE
be utilized for the design and optimization of the exhaust valves giving no affect of
structural strength and thermal strength.
Air cavity can be created at insider the stem of the valve, as it acts in the
form of insulating medium and eventually, heat flow is prevented. So, need of
insulation coating can be minimized. The objective of the air cavity creation is the
engine weight reduction and thermal coating cost as well. The air cavity would
further be optimized in the valve, so that the temperatures and thermal stresses can
be lightly decreased at every nodal point.
FINITE ELEMENT SIMULATION WITH ANSYS WORKBENCH
Towards the analysis of thermal and structural capacity, an exhaust valve is
selected with a single-cylinder engine.
Specifications
Specifications of the Engine are as the following.
Specifications of
Engine
Type of Engine 4 Stroke Single
Cylinder
Maximum Power 7.2 bhp per 8000
rpm
Displacement 97 cc
Diameter of
Cylinder Bore
5 cm
Dimensions
Calculated
Diameter of Valve
Head
20 mm
Length of Stem 65.30 mm

EXHAUST VALVE
Diameter of Valve
Stem
5 mm
Thickness of Valve
Head
5 mm
Face Angle of
Valve
450
The valve is designed and analyzed with the Aluminium Alloy EN52
material, having certain mechanical properties (Ram, 2011).
The design, analysis and optimization are done with the following
assumptions.
1. During normal operation, stresses get arise from the seating and are
moderate, when it is seated at the cam ramp properly. the stress
become very high, when the valve train gets engineered improperly,
resulting in valve bounce or when lash is set improperly or engine is
spread overly. The analysis stresses occurred from valve seating are
considered.
2. Arise of valve misalignment with the set result in distortion stresses
and valve head has to deflect, for seat accommodation and result in
bending stresses.
3. The analysis is done for the medium range engines, assuming that the
cooled with air.
4. Water chamber exhausts the generated heat in chamber, around
cylinder head and liner.

EXHAUST VALVE
5. Valve pops up and down and stationary valve analysis is done with the
assumption that the valve fatigue life is much more and resulting
stress is neglected.
Heat Flux and Structural Stress Calculated Theoretically
DESIGN OF LIGHT WEIGHT VALVE WITHOUT AFFECTING
PROPROERTIES
Mean effective pressure
Diameter of cylinder bore = 50 mm
Length of stroke = 50 mm
Power = 7.2 BHP = 7.2 * 0.746 = 5.37 KW
Rotations Per Minute = 8000
Cylinder Area (A) = π/4 * D2
= 0.7857 * 50 * 50 = 1963.5 mm2.
BHP = (L * N * A * Pm * K ) / 60000
So, Pm (Mean Effective Pressure) = BHP * 60000 / (L * N * A * K )
Pm = 0.41 MPa
But Heat Flux, q = - kAl
Here, is valve temperature (5880 K) / length * direction (7.03 cm)
And k = thermal activity = 0.021 W/mm K
From the CAD model, the stem valve weight = 0.0159 kg
Valve legth = 65.3 + 5 = 70.3 mm
So, main valve main area of valve, Al = weight / (Density * L1)
= 28.811 mm2

EXHAUST VALVE
Therefore,
q = - (1/70) * (-10 *0.021 * 28.81)
so, heat flux = -0.08606 W
Stress of exhaust valve
σ = P/A
here, P = pressure or load on head of valve = 0.41 MPa = 128.81 N
Total change or deflection
is,
Δl = α x Δt x L1,
Δt = difference of temperature between the regions of cold and hot = 588 –
578 = 10 K
E = Modulus of Elasticity = 210 KN / mm2
α = thermal expansion co-efficient = 11.635 * 10 -6
Δl = 0.00817 mm
So, length change = 0.00787 mm
σ (Thermal stress ) = ε x E = 24.43 MPa
ε, Thermal Strain = Δl / L1 = 1.16 * 10-4
FINITE ELEMENT ANALYSIS
The solution is obtained with finite element analysis, which is a numerical
procedure for heat transfer, stress analysis, electromagnetism and fluid flow and

EXHAUST VALVE
other classes of engineering systems. Experimental analysis helps understand the
stresses arising in the device and components, so the prevention can be worked
upon. ANSYS finite element program is one of the FEM software, used in the
design, analysis and optimization of the exhaust valve.
Conditions of Thermal boundary considered are,
Material Density 7865 Kg / m3
Room temperature 298 K
Temperature of exhaust gas 578 K
Temperature of cylinder during
expansion
588 K
RESULTS OF ANALYSIS
Figure: Temperature Distribution and Heat Flux

EXHAUST VALVE
Figure: Stress and Deformation
Figure: Valve with and without air cavity CAD Model
OPTIMIZATION AFTER ANALYSIS
Figure: Optimized Valve Temperature Distribution and Heat Flux

EXHAUST VALVE
RESULTS OF ANALYSIS AFTER OPTIMIZATION
Parameter With Air
Cavity
Without
Air Cavity
Deformation 0.009 0.0062
W (Heat Flux ) 0.04962 0.10403
Temperature,
in 0K
588 588
Stress, in MPa 22.746 23.095
Weight, in Kg 0.0148 0.0159
CONCLUSION
The numerical analysis results obtained suggest that the design of the valve
can possibly optimized, so that the weight would be reduced, with no affect of
deformation values and permissible stress values. Stress reduction can be observed,
because of the air cavity and improves the strength of the valve, further. The valve
weight is finally 17% reduced that can be reduced further, by repeating the same
procedure. Great amount of material is saved, by considering the mass production
and so helps in reducing the cost of manufacture, to a great extent.
REFERENCES
1. SingaiahGali & Charyulu, T.N. (2012). Diesel Engine Exhaust Valve
Design, Analysis and Manufacturing Processes, Indian Stream Research
Journal, Vol.2, Issue 7.
2. Kumar, G. & Mamilla, V. R. (2014) Failure Analysis of Internal Combustion
Engine Valves By Using ANSYS, American Int. Journal of Research in
Science, Technology, Engineering & Mathematics. Vol. 14, Issue 183.

EXHAUST VALVE
3. BalaSundaram, V. N.D. (N.D). Coupled Field Analysis of Exhaust Valve
Using ANSYS.
4. Ram M.S., (2011). Design Modification in Engine Exhaust, International
Journal of Scientific & Engineering Research, Volume 2, Issue 12.
5. Naresh, K., Raghuwanshi, Pandey, A. & Mandloi, R. K. (2012) Failure
Analysis of Internal Combustion Engine Valves: A Review, International
Journal of Innovative Research in Science, Engineering & Technology, Vol
1, Issue 2.
6. Deng, Z, Lan, F., Huang, W., Guo, H., Chen, P. (2014), The Research on
Thermal-Mechanical Coupled Analysis and the Lightweight Design of
Engine Exhaust Valve, Applied Mechanics and Materials, Samming, China.
7. Yadav, M. Y., Mittal, V. D. and Angra, S. (2014), Failure Analysis of Diesel
Engine Exhaust Valve by Using Ansys Software, India: NIT, Kurukshetra,.
8. Calabretta, M., Cacciatore, D., Carden, P. (2010). Valvetrain Friction -
Modeling, Analysis and Measurement of a High Performance Engine
Valvetrain System.
9. Boretti, A., Scalzo, J. (2015). Design of 65 degree V4 Moto GP Engines with
Pneumatic Poppet Valves or Rotary Valves. SAE Technical Paper.
10.Boretti A, Jiang S, Scalzo J. (2015). A Naturally Aspirated Four Stroke
Racing Engine with One Intake and One Exhaust Horizontal Rotary Valve
per Cylinder and Central Direct Injection and Ignition by Spark or Jet. SAE
Technical Paper 2015
11.Muzakkir, S. M., Patil, M. G., (2015). Hirani H. Design of Innovative
Engine Valve.
12.Brown, T. L., Atluri, P., Schmiedeler, J. P. (2013). Design of High Speed
Rotary Valves for Pneumatic Applications.

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13.Zibani, I. (2014). Design, Test and Implementation of a Single Piston Rotary
Valve Engine Control Unit. The International Federation of Automatic
Control.
14.Magda, M. (2012). Engine Blueprinting: How to Check Piston-to-Valve
Clearance EngineLabs.
15.BenzBoost (2012). Officially Introducing The 631 Horsepower 2013
Mercedes-Benz SLS AMG Black Series - Pictures, Curb Weight, And
Specifications.
16.Jeff, Y. (2012). Engine-Cylinder Deactivation Saves Fuel.
17.Sagar. S Deshpande et al. (2015), Experimental Investigation and Analysis
of Engine Valve Designs for Enhanced Fatigue Life, International
Engineering Research Journal (IERJ). Vol 1, Issue 2.