Transient simulation of flow over a throttle body

Introduction:In the last part of the project I have discusses the various parameter effects the simulation and design of the most common valve of the SI engine intake system i.e. butterfly valve. Ideally we need the optimum mixing and unhindered flow for any engine load conditions or drive parameters. For example in the most of the PFI engines the fuel injectors and various other sensors are inside the throttle body. So it is very important to design in such a way that the fuel get mixed properly as well as the engine gets the proper air for the work load it requires. One such case was able simulate in the following report.

Setup:Converge in particular doesn’t require any preprocessing of the mesh so the case set up was pretty much the same here is the picture of the case with dimensions in meters

Here I have considered the air as the primary fluid for the ease of simulation purpose.Since the flow is flowing from the pipe length of 0.12 m and average velocity was calculated via software at the output from the following figure

as you can see from the previous steady state case the flow through the pipe in the first 100 cucyles was the velocity is aroounfd 62.2 m/s so according to the formulae time= (displacement/velocity) i.e. time = 0.12/62.2= 0.0015 s. SO I choose 0.01s in order to have the fair simulation. The throttle profile was consider here as From 0 to 2 ms the valve rotate by 25 degrees. From 2 to 4ms it should stay at 25 degrees.After which by 8ms the valve should get back to it’s original position. Here is the video of throttle valve rotation.

The Mesh results were also the clear there were not overlapping as shown in the picture.Here I retain the fixed embedding of the same level as from the previous setup here the Animation for clear picture.

Results:The rest of the case setup was the same as the previous on so there is nothing much to discuss. There are some grey color blocks occurs in the picture it is due to the simulation was running in 3-D but I am viewing as 2-d images here is the snap shot of the image.

The total cell count was around 46,000 as shown in the image

As you can see the image that there are different type of disturbance in the image this is due to the fact that throttle body is moving initially from 0 to 0.02 seconds and stays same in that period after wards it rotates further more from 0 to 0.08 and then at the end of the simulation there is huge spike because the throttle abruptly got to its original position and simulation ended. This plot confirms the set up and conditions earlier clearly.

Here is the video animation of the Pressure and Velocity respectively for more closure look. As you can see the pressure decreases as the throttle valve approaches to the fully open stage and stagnation point as reaches to towards the throttle body.

In order to confirm the theory here are the pressure and velocity plots.

The plot is the pressure over the whole setup with reaching 0.14 MPa approx.

In order to visualize stagnation point I have created video of introducing the particales in the stream and observe over the whole steam this was possible with the help of the stream tracer feature on Paraview. Here is the Stream Tracers video.

The Mass flow rate was pretty much the same the behavior as of the velocity this shows the conservation laws were satisfied

The Whole simulation took 7 hours approx this is non reacting and non premix flow.In future I would like to do full simulation with little bit of mixing of different common fuels blends such as petrol with 10% ethanol or some thing else and increasing fixed embedding or AMR feature of the converge.