Intake Port Project

Introduction to the Internal flow study

In engine design, the intake port plays an important role in the overall performance of the engine [43]. This study will look complex process of designing and optimising an intake port for an engine, with the goal of enhancing the airflow dynamics and power production of the engine.

This study involves creating an intake port which connects the combustion chamber to a precisely positioned intake aperture. While designing the intake port there are constraints to take into consideration. These include limitations to the intake throat aperture area, valve flow area and total valve area, all of which significantly will influence the engine's breathing capabilities and thus affecting the performance of the engine [44].

This study will look at the following:

• Initial design of the intake port

• CFD simulation and analysis of the initial design

• Optimisation of the intake port design

• CFD simulation and analysis of the improved intake port design

Throughout this study the use of 3D modelling software (Autodesk Inventor) and CFD software (StarCCM+) is used for the design and testing of the intake port, this software allows for visualisation of the airflow characteristics. Analysation of the flow and velocities will allow for refinements of the design and thus allowing for improvements on the engine’s performance.

Figure 1 - Area of intake port aperture

Figure 2 - Intake port CAD design

To start the design process Appendix 2 is used to recreate the cylinder head, in doing so a basic sketch is created for the cylinder head.

Then the intake port aperture is created (shown in figure 1), hear the design meets one of the design constraints. This being “The intake throat aperture area cannot be larger than 1400mm²”, here the Area of intake port aperture is 1399.752mm2.

At this stage in the design flow dynamics are being taken into consideration. The goal is to achieve an optimised balance between airflow performance and engine efficiency [45], this will be looked at further later during the CFD results, using this data will allow for improvements in the design to be made. In the design seen in figure 2, the venturi effect is being theorised by incorporating a tapered section in the design, this is before the port splits into two. This effect is intended to increase the velocity of the air flow into the cylinder [46]. The port then splits into two with a smooth transition (seen in figure 3) to reduce friction and turbulence, doing so will ensure efficient flow.

Figure 3 - Complete initial design

Figure 4 - Complete Port design

Moving forward in the design, CFD analysis (using StarCCM+) will be used to validate the effectiveness of this design, doing so identifying potential areas for further improvement in airflow optimisation and power output thus enhancing the performance of the engine.

CFD simulation and analysis of the initial design

In the design of the intake port, the component needs to be assessed for its performance and efficiency. Computational Fluid Dynamics (CFD) is used to simulate the airflows behaviour within the port while under specific operating conditions, this will provide an insight into the design’s strengths and weaknesses, which allows for visualisation of areas to improve [47].

The simulation (in StarCCM+) is setup to mimic the conditions of the engine, which in this case some of these are requirements.

• Valves set at 10mm lift

• Piston positioned 35mm down the cylinder (in this case a test combustion chamber is created seen in figure 12)

• Intake velocity 20m/s

These constraints allow for a thorough analysis of the intake ports flow dynamics during and intake stroke.

Figure 5 - Intake and Test combustion chamber

Figure 6 - Intake port internal model

In the process of setting up the simulation the test combustion chamber (seen in figure 5) is fitted to cylinder head, as well as the valves being implemented into the design at 10mm lift. Figure 6 shows the next step of the simulation process showing the internal model of the cylinder head

Figure 7 - Intake - Part seed - Velocity

Figure 8 - Venturi Effect example

Figure 7 shows the intake ports velocity during the simulation using a part seed.

The figure shows the velocity distribution in the intake port, which is notably uneven. The results of the simulation show a high concentration of airflow velocity at the top section of the port (~50 m/s to ~60 m/s) when compared to the lower section (~20 m/s to ~30 m/s). This imbalance indicates that the port design might not be efficiently distributing the airflow. A potential cause of this imbalance is the sharp angle at which the port directs the airflow, thus causing Coanda effect. The Coanda effect is a stream flows along a solid surface air cannot be entrained where the stream touches the wall, this causes low pressure to remain in this area and the stream is held against the wall.

Despite the imbalance in velocity, the initial design shows some promising characteristics for the engine performance and efficiency. The first characteristic being the venturi effect, which was spoken about in the design process (figure 15 shows an example of this effect). Looking at figure 13 the simulation highlights the distinct region of peak velocity within the port, which indicates the acceleration of airflow in this aera, with peak velocity in this area being ~60 m/s.

The next positive characteristic shown in the design is the smooth flow path observed throughout most of the intake port. The streamlines in figure 13 show that the airflow has a consistent and predictable path throughout the port, with minimal disruptions to the airflow. This characteristic suggests that the ports shape is effective at maintaining laminar flow, thus reducing the amount of energy lost.

The CFD simulation of the initial intake port design has shown both strength and weaknesses of the design and thus showing areas for improvement. While the overall design demonstrates promising aspects, such as the effective implementation of the venturi effect and smooth flow, the uneven velocity distribution is a significant area of concern in the design. The sharp angle of the port will cause a high velocity concentration at the top section of the port, which is likely due to the Coanda effect. Once optimised the port will flow effectively and thus improving the performance of the engine.

Final intake port design

Optimisation of the intake port design

Based on the CFD simulation and analysis of the initial port design, there are a few areas identified for the optimisation of the port. The main focus of the redesign will be to address the uneven velocity distribution, which is seen in figure 13.

Figure 9 - Sketch of Final Intake port

Figure 10 - Final Intake port internal model

To improve the port design the following alterations will be implemented:

• Port angle adjustment – The angle that the port was at will be adjusted to reduce the sharp turn, this adjustment is seen in figures 9 and 10 with curve of the intake port. This should distribute the the airflow evenly through out the port. Doing so will create a smoother flow path, which should reduce turbulence and thus improve airflow efficiency.

• Port split refinement – The port’s split section will be adjusted to promote an even split between the two valves. Balancing the flow is essential for maintinaing consistent cylinder filling and will improve the volumetric efficiency.

• Venturi effect fine tuning – The location and intensity of the Venturi effect will be altered to ensure the flow is managed effectively throughout the port. To do this the port is narrnowed (seen in the sketch in figure 9) prior to it splitting into two, this should increase the velocity of the air flowing into the cylinder.

These improvements should improve the performance of the port, the effectiveness of these design alterations will be evalutated with the use of CFD simulations.

CFD simulation and analysis of the improved intake port design

The main goal of the redesign was to address the issues identified with the initial design, these including an uneven velocity distribution and inefficient airflow splitting. Figures 18 and 19 show the results of the CFD simulation of the improved design.

Figure 11 - Final Intake - Part seed - Pressure

Figure 12 - Final Intake - Part seed - Velocity

The results of the CFD simulation show a significant improvement in the airflow distribution when compared to the initial design. Figure 12 shows that focus of distributing the airflow evenly in the port has worked effectively. To achieve this the port angle was adjusted, which reduces sharp turns and promotes smoother airflow paths.

The CFD simulation also show that the Venturi effect (seen in figure 12) in the improved design has increased airflow velocity while maintaining balanced flow into both valves. The peak velocity is ~35.8 m/s, which is lower than the initial design (~60 m/s), indicating reduced turbulence and a more stable flow.

Figure 11 shows a smooth pressure gradient with few high pressure zones. The highest pressure occurs near the inlet of the design, gradually decreasing in the aera of Venturi effect, this reducing energy lost and improving the efficiency.

Conclusion

The redesign and optimisation of the intake port has shown a significant improvement in the airflow dynamics and overall performance. The initial design presented issues such as uneven velocity distribution and inefficient flow splitting. The changes to the design, these being port angle adjustment, split refinement, and Venturi effect adjustment, these challenges were addressed effectively.

The CFD simulations of the improved design show a uniform velocity distribution, a reduction in turbulence and minimised pressure losses. The smooth pressure gradient seen in figure 11 and the balanced airflow into both valves show an enhanced volumetric efficiency. Additionally, the adjusted Venturi effect successfully increased airflow velocity while maintaining stability.

Overall, these improvements highlight the importance of simulation and analysis in achieving optimal performance. The optimised intake port design provides a strong foundation for enhancing the engine efficiency and power output.

Please Get In Touch At tbetetafreeman@gmail.com

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