A Case Study on Exhaust Manifold Flow Analysis Using ANSYS Fluent
Introduction
The fluidic behavior of an exhaust manifold is modelled using ANSYS Fluent to investigate the alteration of several flow parameters. Once we establish a basic configuration, inlet velocity, turbulence intensity, outlet diameter, and pressure distribution are adjusted in logical steps to assess their impact on pressure drop and flow distribution. Comparative velocity-pressure graphs are used to determine the most appropriate flow condition.
Case 1: Baseline Configuration
Input Parameters:
·
Inlet Velocity: 0.987 m/s
·
Turbulence Intensity: 1%
·
Inlet Hydraulic Diameter: 0.0254 m
·
Outlet Hydraulic Diameter: 0.01905 m
·
Outlet Gauge Pressure: 0 Pa
Observations:
· Uniform distribution across all outlets.
· Moderate pressure drops through the manifold.
Figures: – Flow Pathlines with Mesh (Fig 1.1), Velocity Contour (Fig 1.2), Pressure Contour (Fig 1.3), Velocity Vectors (Fig 1.4).
Fig 1.1 Flow Pathlines with Mesh
Fig 1.2 Velocity Contour
Fig 1.3 Pressure Contour
Fig 1.4 Velocity Vector
Fig 1.5 Residual Graph
Fig 1.6 Volume-Flow Rate
Table 1.2.1 Mass Flow Rate
|
Inlet |
0.0006063730424359209 |
|
Outlet-1 |
-0.000157018848379343 |
|
Outlet-2 |
-0.0002200332336641004 |
|
Outlet-3 |
-0.0002293208020550309 |
|
Net Flow [kg/s] |
1.583374e-10 |
Case 2: Increased Inlet Velocity and Turbulence Intensity
Reason for Selection:
This case examines the relationship between higher stream force and wider turbulence, which imitates operational conditions with faster stream rates.
Input Parameters:
·
Inlet Velocity: 1.2 m/s
·
Turbulence Intensity: 5%
·
Other parameters: Same as Case 1
Observations:
· Increased velocity magnitudes and stronger streamline curvature.
· Noticeable increase in pressure drop.
Scientific Insight:
Higher flow separation is a consequence of increased dynamic pressure and flow momentum with an increase in intake velocity. The mixing process in the manifold is enhanced by greater turbulence.
Figures: – Velocity Streamlines (Fig 2.1), Velocity Contour (Fig 2.2), Pressure Contour (Fig 2.3), Velocity Vectors (Fig 2.4).
Fig 2.1 Velocity Streamlines
Fig 2.2 Velocity Contour
Fig 2.3 Pressure Contour
Fig 2.4 Velocity Vector
Fig 2.5 Velocity Flow Rate
Fig 2.6 Residuals Graph
Table 2.2.1 Mass Flow Rate
|
Inlet |
0.0007372316625360733 |
|
Outlet-1 |
-0.0001918717442057694 |
|
Outlet-2 |
-0.0002663743353470258 |
|
Outlet-3 |
-0.0002789856910734104 |
|
Net Result [kg/s] |
-1.080901e-10 |
Case 3: Reduced Outlet Diameters
Reason for Selection:
Desaturation of outlet diameters alters flow resistance, which can be used to balance flow rates using optimal geometry.
Input Parameters:
·
Outlet Hydraulic Diameter: 0.015 m
·
Others: Same as Case 1
Observations:
·
Higher local velocities near outlets.
· Elevated pressure in the upstream caused by constriction of the outlet.
Scientific Insight:
Bernoulli’s principles suggest that a smaller outlet area leads to an increase in upstream static pressure and accelerated exit velocity.
Figures: – Pathlines (Fig 3.1), Velocity Contour (Fig 3.2), Dynamic Pressure Contour (Fig 3.3), Velocity Vectors (Fig 3.4).
Fig 3.1 Flow Pathlines
Fig 3.2 Velocity Contour
Fig 3.3 Dynamic Pressure Contour
Fig 3.4 Velocity-Vector
Fig 3.2 Residuals Graph
Fig 3.3 Volume-Flow Rate
Table 3.2.1 Mass Flow Rate:
|
Inlet |
0.0006063730424359209 |
|
Outlet 1 |
-0.0001554103488155116 |
|
Outlet 2 |
-0.0002214590858444973 |
|
Outlet 3 |
-0.0002295039992445406 |
|
Net Result [kg/s] |
-3.914686e-10 |
Case 4: Varying Outlet Pressures (Backpressure Conditions)
Reason for Selection:
In practical applications, outlet pressures are known to vary. The impact of differential outlet pressures on overall manifold behavior is demonstrated in this example.
Input Parameters:
·
Outlet 1 Pressure: 0 Pa
·
Outlet 2 Pressure: 500 Pa
·
Outlet 3 Pressure: 1000 Pa
Observations:
· Segments may experience reverse or stagnated flow due to an uneven and backpressure-independent flow distribution.
· Enhanced pressure gradients in the manifold.
Scientific Insight:
Lower backpressure outlets tend to attract more flow distribution as downstream pressure increases, which in turn reduces local mass flow rates.
Figures: – Velocity Pathlines (Fig 4.1), Velocity Contour (Fig 4.2), Pressure Contour (Fig 4.3), Velocity Vectors (Fig 4.4).
Fig 4.1 Flow Pathlines
Fig 4.2 Velocity Contour
Fig 4.3 Pressure Contour
Fig 4.4 Velocity Vector
Fig 4.5 Volume Flow Rate
Fig 4.6 Residuals Graph
Mass Flow Rate
|
inlet |
0.00060637304 |
|
outlet-1 |
-0.0098861858 |
|
outlet-2 |
-0.0010698918 |
|
outlet-3 |
0.01034029 |
|
Net [kg/s] |
-9.4142561e-06 |
Comparative Analysis of Velocity and Pressure
|
Case |
Max Velocity (m/s) |
Average Pressure Drop (Pa) |
Flow Uniformity |
|
Case 1 |
Baseline |
Moderate |
Balanced |
|
Case 2 |
Increased |
Significant |
More jetting effect |
|
Case 3 |
Higher near outlets |
Elevated |
Skewed towards least resistance |
|
Case 4 |
Non-uniform |
Highest |
Skewed towards low backpressure |
Summary Graphs
·
Velocity Comparison Graph: In the Velocity Comparison Graph, it is shown that Cases 1 and 2 have higher peak velocities, while Case 4 has lower ones due to backpressure changes.
·
Pressure Drop Comparison Graph: The Pressure Drop Comparison Graph displays an increasing pressure drop with the highest point in Case 4.
Conclusion and Recommendation
Our research indicates that the main factors influencing flow distribution and pressure drop are entrance velocity and exit pressure. A higher input velocity, but no backpressure limits, in Case 2 allows for greater flow without undesirable backflow or excessive pressure drop effects.
Optimal Configuration: Increase intake velocity moderately while keeping exit pressures equal for efficient flow distribution and minimum backpressure-induced losses.
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