Analysis of Diesel Engine Exhaust Manifold
6
Analysis of a Diesel Engine Exhaust Manifold Yiran Yang 1 Miao He 2 Masoud Mojtahed 3 [email protected] [email protected] [email protected] Department of Mechanical Engineering, Purdue University Calumet, 2200 169 th ST, Hammond, IN 46323 Department of Mechanical Engineering, Purdue University Calumet, 2200 169 th ST, Hammond, IN 46323 Department of Mechanical Engineering, Purdue University Calumet, 2200 169 th ST, Hammond, IN 46323 Abstract The exhaust manifold is an essential component of an engine, which has become increasingly important because of innovations in the industry. Thus, the efficiency of an exhaust manifold is a key factor in overall engine efficiency. In operating conditions, there are many factors that may influence the performance of an exhaust manifold, such as temperature, pressure, wall thickness, coolant velocity, etc. A manufacturer of diesel engine’s exhaust manifolds was interested in investigating the performance of its manifolds. This paper describes the method of analysis and results obtained by Fluent and ANSYS software. The purpose of the project is to analyze the stress distribution and locate the areas most prone to failure. Background The exhaust manifold is an essential component of an engine. It channels the exhaust gases from multiple inlets into a single outlet. The function of the exhaust manifold is to collect and cool down the exhaust gas temperature with a proper coolant. Given the increasing emphasis on engine efficiency in recent years, the exhaust manifold efficiency has become a major concern and a critical component of engine efficiency. A good design of an exhaust manifold will increase the reliability and performance of the engine while decreasing its maintenance cost. Such a design keeps the customers satisfied and improves the manufacturer’s profitability. However, an exhaust manifold with poor design will result in performance that does not meet desirable efficiency standards or will lead to accidents. In addition, because the exhaust gas flows through the manifold at very high temperatures, up to more than 900 degrees Kelvin, improper cooling and diversion of exhaust gasses may result in distortion of the manifold or even damage to the engine. Based on the above discussions, the proper design of the exhaust manifold is an essential factor that impacts engine efficiency. The two important factors that should be considered initially are ensuring that the exhaust gas can be cooled as qualified and to maximize the overall efficiency of the engine. Engine emissions have the most important impact on the environment. There are several harmful gases in an engine exhaust, such as carbon dioxide and nitrogen oxides, which cause greenhouse effects and contribute to global warming. When the exhaust manifold works at low efficiency, harmful gasses are produced, and the engine emission will cause environmental damage. One way to reduce the environmental damage is to increase the manifold efficiency, which in turn increases engine efficiency. Besides environmental aspects, increasing efficiency of the exhaust manifold is also beneficial for consumers. An efficient engine consumes less fuel, and a good manifold design requires less maintenance. These are all savings for the consumers. Methodology and Results 1. Model Simplification The configuration of the exhaust manifold is shown in Figure 1. In the first stage, a simplified model is used to verify the accuracy of the analysis. A double pipe with coolant and exhaust gas flowing in and out was modeled in gambit, shown in Figure 2. Proceedings of the ASME 2014 International Mechanical Engineering Congress and Exposition IMECE2014 November 14-20, 2014, Montreal, Quebec, Canada IMECE2014-37606 1 Copyright © 2014 by ASME
Transcript of Analysis of Diesel Engine Exhaust Manifold
Analysis of Diesel Engine Exhaust ManifoldYiran Yang1 Miao He2
Masoud Mojtahed3
[email protected] [email protected] [email protected]
Department of Mechanical Engineering, Purdue University
Calumet, 2200 169th ST, Hammond, IN 46323 Department of Mechanical Engineering, Purdue University
Calumet, 2200 169th ST, Hammond, IN 46323 Department of Mechanical Engineering, Purdue University Calumet, 2200
169th ST, Hammond, IN 46323
Abstract The exhaust manifold is an essential component of an
engine, which has become increasingly important because of
innovations in the industry. Thus, the efficiency of an
exhaust manifold is a key factor in overall engine efficiency.
In operating conditions, there are many factors that may
influence the performance of an exhaust manifold, such as
temperature, pressure, wall thickness, coolant velocity, etc.
A manufacturer of diesel engine’s exhaust manifolds
was interested in investigating the performance of its
manifolds. This paper describes the method of analysis and
results obtained by Fluent and ANSYS software. The
purpose of the project is to analyze the stress distribution
and locate the areas most prone to failure.
Background The exhaust manifold is an essential component of an
engine. It channels the exhaust gases from multiple inlets
into a single outlet. The function of the exhaust manifold is
to collect and cool down the exhaust gas temperature with a
proper coolant.
recent years, the exhaust manifold efficiency has become a
major concern and a critical component of engine efficiency.
A good design of an exhaust manifold will increase the
reliability and performance of the engine while decreasing
its maintenance cost. Such a design keeps the customers
satisfied and improves the manufacturer’s profitability.
However, an exhaust manifold with poor design will result
in performance that does not meet desirable efficiency
standards or will lead to accidents. In addition, because the
exhaust gas flows through the manifold at very high
temperatures, up to more than 900 degrees Kelvin,
improper cooling and diversion of exhaust gasses may result
in distortion of the manifold or even damage to the engine.
Based on the above discussions, the proper design of
the exhaust manifold is an essential factor that impacts
engine efficiency. The two important factors that should be
considered initially are ensuring that the exhaust gas can be
cooled as qualified and to maximize the overall efficiency of
the engine.
the environment. There are several harmful gases in an
engine exhaust, such as carbon dioxide and nitrogen oxides,
which cause greenhouse effects and contribute to global
warming. When the exhaust manifold works at low
efficiency, harmful gasses are produced, and the engine
emission will cause environmental damage.
One way to reduce the environmental damage is to
increase the manifold efficiency, which in turn increases
engine efficiency. Besides environmental aspects, increasing
efficiency of the exhaust manifold is also beneficial for
consumers. An efficient engine consumes less fuel, and a
good manifold design requires less maintenance. These are
all savings for the consumers.
Methodology and Results 1. Model Simplification
The configuration of the exhaust manifold is shown in
Figure 1. In the first stage, a simplified model is used to
verify the accuracy of the analysis. A double pipe with
coolant and exhaust gas flowing in and out was modeled in
gambit, shown in Figure 2.
Proceedings of the ASME 2014 International Mechanical Engineering Congress and Exposition IMECE2014
November 14-20, 2014, Montreal, Quebec, Canada
IMECE2014-37606
The simple model is used to simulate the original
manifold while keeping the same loading and boundary
conditions.
double pipe. The cylinders were spaced appropriately to
create walls, gas, and fluid channels. The quality of mesh
was verified in gambit for FLUENT software application.
Finally, the pipes were defined as solids, and gas and fluid
were added to the cavities.
1.2 Boundary Conditions Application in FLUENT
The meshed model was opened in Fluent and boundary
conditions were applied. In addition, material properties,
fluids velocities, and temperatures were defined for water
and exhaust gas in the pipes. Data used in the analysis are
shown in Tables 1 and 2. Water was chosen as the coolant
liquid and carbon dioxide as the exhaust gas in a laminar
flow model.
Left Pipe Right Pipe Coolant Zone
Heat Transfer Rate [W] 6972.44 9067.18 89462.62
Table 2. Total Heat Transfer Rates Avg. Convection Coefficient Left Pipe Right Pipe Coolant
Zone
Inlet Temperature - [K] 975.74 975.74 362.78
Wall Temperature - [K] 606 606 300
Convection Coefficient
3672.22
model.
Figure 4 exhibits the static temperature distribution of
the pipe’s cross section surface and the wall flux,
respectively.
1.3 ANSYS Analysis
establish the geometry of the model [1,2,3]
. Then, the
and strain distributions are shown in figures 5 and 6.
2 Copyright © 2014 by ASME
Figure 5 Stress Distribution of Interior Pipe
Figure 6 Strain Distribution of Interior pipe
2. Manifold Analysis
The original manifold is of a complex shape with welds
included. This complexity created difficulty in meshing the
model in ANSYS. As a result, the welds were removed in
the ANSYS model to reduce the complexity. After removing
welds and other unimportant parts from the original model,
the three major remaining parts were the coolant pipe, the
left exhaust pipe, and the right exhaust pipe in the structure.
Frozen objects were added into spaces between the pipes
and the inside of the interior pipe to model the coolant and
exhaust gasses. Exhaust gases flow in two independent left
and right exhaust pipes. Water runs in the space between
sleeve pipe and the exterior of the gas pipe.
Figure 7 shows the refined model in Workbench Model
Designer.
2.1 Model Mesh in Workbench
Body sizing and face sizing were performed to define
the mesh size. The model was also tested for inflation and
the results were similar to a model without inflation. After
the model was refined, it was meshed in ANSYS. The mesh
quality was checked by a tool called mesh quality in
Workbench. The meshed model was found to be adequately
stable to be imported into Fluent. Figure 8 shows the
meshed model.
2.2 Application of Boundary Conditions in FLUENT
The Boundary conditions were applied to the model to
define the mass flow rate inlets, pressure outlets, coupled
.
equation is K-epsilon model with all standard and default
choices. Stainless steel was used as material for pipes, water
as coolant, and carbon dioxide as the exhaust gas. Table 4
shows exact values of boundary condition that are applied to
the model.
Table 3 Boundary Conditions
results of FLUENT solution and velocity distribution are
shown in Figure 9. The fluids flowing through pipes can be
clearly seen in this figure.
Figure 9 Velocity Distribution
the entire model.
Figure 11 shows the temperature distribution for a
cross-section of the model.
Section
Fluent temperature distribution module was imported
into Thermal and Static Structural Modules of Workbench
for stress Analysis. With importance of temperature load in
Steady-State Thermal Module, the Static Structural Module
can calculate the required thermal stresses. The solution
results can be influenced by the mesh quality. Thus, the
proper mesh method and model were tested over times for
an accuracy of the ANSYS results. Finally, the boundary
conditions are applied to the model.
The stress and strain were calculated and investigated
for failure analysis. Figures 12 and 13 show the principal
stresses in the inner and outer pipes.
Figure 12 Principal Stress Distribution of Inner Pipes
Left Pipe
Inlet Temperature - [K] 970 970 360
Wall Temperature - [K] 300 300 606
4 Copyright © 2014 by ASME
Figure 13 Principal Stress Distribution of Outer Pipe
Figure 14 Von Mises Stress Distribution of Inner Pipes
Figure 15 Von Mises Stress Distribution of Outer Pipe
Figure 16 Maximum Von Mises Stress Area
Von Mises stresses are shown in Figures 14, 15, and 16.
Maximum stresses are located at the manifold’s inlets. This
is expected as the hot engine gas enters the pipes at the
inlets of the manifold. Von Mises stress distributions are
then used to determine the safety factor in the inner and
outer pipes of the manifold. Safety factors were determined
for the 310 stainless steel that is available on the ANSYS
library. Figure 17 shows the safety factor of the outer pipe.
Figure 17 Safety Factor of the Outer Pipe
5 Copyright © 2014 by ASME
Figure 18 Location of the Minimum Safety Factor for 310
Stainless Steel
All gas inlets exhibit high stress on the interior of the
pipes. In order to improve the thermal performance of the
pipes and the safety factors, a different type of material is
used to simulate the results. Two other stainless steels were
used to improve the safety factors. Stainless steel 304 with
yield strength of 276 MPa, used for its high temperature
tolerance, improves the minimum safety factor to 0.91.
Stainless steel 316 with a good weldability and yield
strength of 345 MPa gives the minimum safety factor of
1.13. In addition, Titanium alloy which has higher yield
strength of 920 MPa was also investigated in the analysis.
The minimum safety factor of 1.45 for titanium alloy is the
highest among the options, as seen in Figures 19 and 20.
Use of titanium alloy also reduces the weight of manifold by
41 percent. However, the weldability of titanium alloy and
its cost could be a drawback in using titanium alloy by the
manufacturer.
Alloy Pipe
distributions agree with the expected operational conditions.
However, the minimum safety factor results indeed show the
failure potential. This could be attributed to hot engine gas
entering the manifold at the inlets. The simulation results
clearly show that these areas are exposed to a higher
temperature and higher pressure as the flow of hot engine
gas enters the manifold.
In order to avoid the possible failure of the manifold,
the 316 stainless steel, which has higher yield strength and
good weldability, is recommended to the manufacturer. In
addition, future studies with the inclusion of weldments are
recommended to improve the accuracy of the simulated
model and possible failure due to weld fatigue.
References [1]http://202.118.250.111:8080/fluent/Gambit13_help/tutori
[2]http://hpce.iitm.ac.in/website/Manuals/Fluent_6.3/fluent6
[3]http://www.mece.ualberta.ca/tutorials/ansys/, Dec. 2012,
muffler using a one dimensional CFD channel,” Applied
Acoustic.
based on coupling of 3D CFD tool with effective 1D
channel models,” Catalysis today.
[email protected] [email protected] [email protected]
Department of Mechanical Engineering, Purdue University
Calumet, 2200 169th ST, Hammond, IN 46323 Department of Mechanical Engineering, Purdue University
Calumet, 2200 169th ST, Hammond, IN 46323 Department of Mechanical Engineering, Purdue University Calumet, 2200
169th ST, Hammond, IN 46323
Abstract The exhaust manifold is an essential component of an
engine, which has become increasingly important because of
innovations in the industry. Thus, the efficiency of an
exhaust manifold is a key factor in overall engine efficiency.
In operating conditions, there are many factors that may
influence the performance of an exhaust manifold, such as
temperature, pressure, wall thickness, coolant velocity, etc.
A manufacturer of diesel engine’s exhaust manifolds
was interested in investigating the performance of its
manifolds. This paper describes the method of analysis and
results obtained by Fluent and ANSYS software. The
purpose of the project is to analyze the stress distribution
and locate the areas most prone to failure.
Background The exhaust manifold is an essential component of an
engine. It channels the exhaust gases from multiple inlets
into a single outlet. The function of the exhaust manifold is
to collect and cool down the exhaust gas temperature with a
proper coolant.
recent years, the exhaust manifold efficiency has become a
major concern and a critical component of engine efficiency.
A good design of an exhaust manifold will increase the
reliability and performance of the engine while decreasing
its maintenance cost. Such a design keeps the customers
satisfied and improves the manufacturer’s profitability.
However, an exhaust manifold with poor design will result
in performance that does not meet desirable efficiency
standards or will lead to accidents. In addition, because the
exhaust gas flows through the manifold at very high
temperatures, up to more than 900 degrees Kelvin,
improper cooling and diversion of exhaust gasses may result
in distortion of the manifold or even damage to the engine.
Based on the above discussions, the proper design of
the exhaust manifold is an essential factor that impacts
engine efficiency. The two important factors that should be
considered initially are ensuring that the exhaust gas can be
cooled as qualified and to maximize the overall efficiency of
the engine.
the environment. There are several harmful gases in an
engine exhaust, such as carbon dioxide and nitrogen oxides,
which cause greenhouse effects and contribute to global
warming. When the exhaust manifold works at low
efficiency, harmful gasses are produced, and the engine
emission will cause environmental damage.
One way to reduce the environmental damage is to
increase the manifold efficiency, which in turn increases
engine efficiency. Besides environmental aspects, increasing
efficiency of the exhaust manifold is also beneficial for
consumers. An efficient engine consumes less fuel, and a
good manifold design requires less maintenance. These are
all savings for the consumers.
Methodology and Results 1. Model Simplification
The configuration of the exhaust manifold is shown in
Figure 1. In the first stage, a simplified model is used to
verify the accuracy of the analysis. A double pipe with
coolant and exhaust gas flowing in and out was modeled in
gambit, shown in Figure 2.
Proceedings of the ASME 2014 International Mechanical Engineering Congress and Exposition IMECE2014
November 14-20, 2014, Montreal, Quebec, Canada
IMECE2014-37606
The simple model is used to simulate the original
manifold while keeping the same loading and boundary
conditions.
double pipe. The cylinders were spaced appropriately to
create walls, gas, and fluid channels. The quality of mesh
was verified in gambit for FLUENT software application.
Finally, the pipes were defined as solids, and gas and fluid
were added to the cavities.
1.2 Boundary Conditions Application in FLUENT
The meshed model was opened in Fluent and boundary
conditions were applied. In addition, material properties,
fluids velocities, and temperatures were defined for water
and exhaust gas in the pipes. Data used in the analysis are
shown in Tables 1 and 2. Water was chosen as the coolant
liquid and carbon dioxide as the exhaust gas in a laminar
flow model.
Left Pipe Right Pipe Coolant Zone
Heat Transfer Rate [W] 6972.44 9067.18 89462.62
Table 2. Total Heat Transfer Rates Avg. Convection Coefficient Left Pipe Right Pipe Coolant
Zone
Inlet Temperature - [K] 975.74 975.74 362.78
Wall Temperature - [K] 606 606 300
Convection Coefficient
3672.22
model.
Figure 4 exhibits the static temperature distribution of
the pipe’s cross section surface and the wall flux,
respectively.
1.3 ANSYS Analysis
establish the geometry of the model [1,2,3]
. Then, the
and strain distributions are shown in figures 5 and 6.
2 Copyright © 2014 by ASME
Figure 5 Stress Distribution of Interior Pipe
Figure 6 Strain Distribution of Interior pipe
2. Manifold Analysis
The original manifold is of a complex shape with welds
included. This complexity created difficulty in meshing the
model in ANSYS. As a result, the welds were removed in
the ANSYS model to reduce the complexity. After removing
welds and other unimportant parts from the original model,
the three major remaining parts were the coolant pipe, the
left exhaust pipe, and the right exhaust pipe in the structure.
Frozen objects were added into spaces between the pipes
and the inside of the interior pipe to model the coolant and
exhaust gasses. Exhaust gases flow in two independent left
and right exhaust pipes. Water runs in the space between
sleeve pipe and the exterior of the gas pipe.
Figure 7 shows the refined model in Workbench Model
Designer.
2.1 Model Mesh in Workbench
Body sizing and face sizing were performed to define
the mesh size. The model was also tested for inflation and
the results were similar to a model without inflation. After
the model was refined, it was meshed in ANSYS. The mesh
quality was checked by a tool called mesh quality in
Workbench. The meshed model was found to be adequately
stable to be imported into Fluent. Figure 8 shows the
meshed model.
2.2 Application of Boundary Conditions in FLUENT
The Boundary conditions were applied to the model to
define the mass flow rate inlets, pressure outlets, coupled
.
equation is K-epsilon model with all standard and default
choices. Stainless steel was used as material for pipes, water
as coolant, and carbon dioxide as the exhaust gas. Table 4
shows exact values of boundary condition that are applied to
the model.
Table 3 Boundary Conditions
results of FLUENT solution and velocity distribution are
shown in Figure 9. The fluids flowing through pipes can be
clearly seen in this figure.
Figure 9 Velocity Distribution
the entire model.
Figure 11 shows the temperature distribution for a
cross-section of the model.
Section
Fluent temperature distribution module was imported
into Thermal and Static Structural Modules of Workbench
for stress Analysis. With importance of temperature load in
Steady-State Thermal Module, the Static Structural Module
can calculate the required thermal stresses. The solution
results can be influenced by the mesh quality. Thus, the
proper mesh method and model were tested over times for
an accuracy of the ANSYS results. Finally, the boundary
conditions are applied to the model.
The stress and strain were calculated and investigated
for failure analysis. Figures 12 and 13 show the principal
stresses in the inner and outer pipes.
Figure 12 Principal Stress Distribution of Inner Pipes
Left Pipe
Inlet Temperature - [K] 970 970 360
Wall Temperature - [K] 300 300 606
4 Copyright © 2014 by ASME
Figure 13 Principal Stress Distribution of Outer Pipe
Figure 14 Von Mises Stress Distribution of Inner Pipes
Figure 15 Von Mises Stress Distribution of Outer Pipe
Figure 16 Maximum Von Mises Stress Area
Von Mises stresses are shown in Figures 14, 15, and 16.
Maximum stresses are located at the manifold’s inlets. This
is expected as the hot engine gas enters the pipes at the
inlets of the manifold. Von Mises stress distributions are
then used to determine the safety factor in the inner and
outer pipes of the manifold. Safety factors were determined
for the 310 stainless steel that is available on the ANSYS
library. Figure 17 shows the safety factor of the outer pipe.
Figure 17 Safety Factor of the Outer Pipe
5 Copyright © 2014 by ASME
Figure 18 Location of the Minimum Safety Factor for 310
Stainless Steel
All gas inlets exhibit high stress on the interior of the
pipes. In order to improve the thermal performance of the
pipes and the safety factors, a different type of material is
used to simulate the results. Two other stainless steels were
used to improve the safety factors. Stainless steel 304 with
yield strength of 276 MPa, used for its high temperature
tolerance, improves the minimum safety factor to 0.91.
Stainless steel 316 with a good weldability and yield
strength of 345 MPa gives the minimum safety factor of
1.13. In addition, Titanium alloy which has higher yield
strength of 920 MPa was also investigated in the analysis.
The minimum safety factor of 1.45 for titanium alloy is the
highest among the options, as seen in Figures 19 and 20.
Use of titanium alloy also reduces the weight of manifold by
41 percent. However, the weldability of titanium alloy and
its cost could be a drawback in using titanium alloy by the
manufacturer.
Alloy Pipe
distributions agree with the expected operational conditions.
However, the minimum safety factor results indeed show the
failure potential. This could be attributed to hot engine gas
entering the manifold at the inlets. The simulation results
clearly show that these areas are exposed to a higher
temperature and higher pressure as the flow of hot engine
gas enters the manifold.
In order to avoid the possible failure of the manifold,
the 316 stainless steel, which has higher yield strength and
good weldability, is recommended to the manufacturer. In
addition, future studies with the inclusion of weldments are
recommended to improve the accuracy of the simulated
model and possible failure due to weld fatigue.
References [1]http://202.118.250.111:8080/fluent/Gambit13_help/tutori
[2]http://hpce.iitm.ac.in/website/Manuals/Fluent_6.3/fluent6
[3]http://www.mece.ualberta.ca/tutorials/ansys/, Dec. 2012,
muffler using a one dimensional CFD channel,” Applied
Acoustic.
based on coupling of 3D CFD tool with effective 1D
channel models,” Catalysis today.
