Intake Port Design

Intake ports are the final part of an engine’s air induc­tion system. They connect the intake manifold with the com­bus­tion chamber and are opened and closed with the intake valves.

While intake ports are found in all types of engines, they have an espe­cially pro­nounced influ­ence on the air/​fuel mixture for­ma­tion in gasoline (SI) engines. In Diesel engines, the piston bowl also helps with that task.

Fur­ther­more, the port shape is respon­si­ble for the charge motion, where favor­ably shaped vortices reduce energy dis­si­pa­tion, and it influ­ences the amount of air that gets into the com­bus­tion chamber, where an increase leads to higher engine performance.

This blog post gives you a short intro­duc­tion of the relevant intake port design capa­bil­i­ties within CAESES®. In addition, a recent project is outlined where CAESES® and STAR-CCM+ were coupled to fully automate the shape opti­miza­tion of an intake port.

CAESES’ Intake Port Design Capabilities

CAESES® has been effec­tively used to design state-of-the-art intake ports and brings along several key capa­bil­i­ties for this specific task. The main ​“duct” of the port is typ­i­cally modeled using CAESES®’ Meta Surface tech­nol­ogy, where a para­me­ter­ized cross-section is swept in a spec­i­fied direc­tion, e.g., along a path, and function curves control how the cross-section para­me­ters change during the sweep. Arbi­trary cross-section para­me­ter­i­za­tions can be used, see the ani­ma­tions below in the section ​“Geometry Setup”. Read a detailed descrip­tion of the intake port modeling capa­bil­i­ties here.

This con­trolled-sweep approach brings along a high amount of flex­i­bil­ity, while keeping the number of design para­me­ters as low as possible, for a faster optimization.

Here is a short summary of the impor­tant features when design­ing intake ports with CAESES®:

• The geometry para­me­ter­i­za­tion can be set up so that flow-relevant para­me­ters are directly con­trolled, e.g., the dis­tri­b­u­tion of cross-sec­tional area along the path, even under con­sid­er­a­tion of blocking due to the valve guide or stem.
• Alter­na­tively, morphing methods can be used to deform an existing – imported – geometry. This is faster, but less flexible and offering less direct control. The morphing can be applied to a NURBS surface geometry and be exported as IGES/​STEP/​etc., or to a dis­cretized geometry such as meshes or tessellations.
• Robust vari­a­tion of the port geometry is possible with no failed variants. As for other geome­tries, one of the most impor­tant targets of our software is 100% robust geometry vari­a­tion, obtained by smart para­me­ter­i­za­tion and depen­dency-based models.
• Arbi­trary con­straints can be built into the model or mon­i­tored. Typical examples are: man­u­fac­tur­ing con­straints such as drafting angles and minimal radii, or pack­ag­ing con­straints, where the distance to neigh­bor­ing components/​elements has to be maintained.
• The geometry can be exported in several dif­fer­ent formats suitable for your CFD/​meshing tools. Many of the formats support patch naming, so that the down­stream tool can cor­rectly identify surface patches for the assign­ment of indi­vid­ual mesh settings or boundary conditions.

Example Case: Intake Port Opti­miza­tion with STAR-CCM+

The fol­low­ing sections describe an opti­miza­tion study that was carried out to demon­strate the workflow for intake port opti­miza­tion using CAESES® and STAR-CCM+. The port was a typical geometry for an SI engine, combined with a pent-roof com­bus­tion chamber and four valves per cylinder.

Geometry Setup

The para­met­ric intake port model was created in CAESES® and a set of seven para­me­ters were selected for the optimization.

ELLIPSE FACTOR

The ellipse factor in two stream­wise loca­tions. This controls if the cross-section has a circular or rather ellip­ti­cal shape.

ECCEN­TRIC­ITY

The eccen­tric­ity in two stream­wise loca­tions. This blends the cross-section shape from a circular/​elliptical to a D‑shaped one.

INLET ANGLE
 

The inlet angle, i.e., the angle between the intake port’s path and the hor­i­zon­tal plane.

INLET HEIGHT

The inlet height is a typical standard dimen­sion of intake ports.

STRAIGHT LENGTH

The straight length at the inlet. This controls the shape of the path, when pro­jected onto a hor­i­zon­tal plane, specif­i­cally for how long it is straight when coming from the inlet. It has a major influ­ence on the septum length.

STAR-CCM+ Automa­tion

STAR-CCM+ was coupled to CAESES® using the Software Con­nec­tor. The geometry as dis­played before, was com­ple­mented by a half-spher­i­cal plenum to model the inlet flow con­di­tions and exported in a ​“colored” STEP format, which includes indi­vid­ual IDs for the iden­ti­fi­ca­tion of the dif­fer­ent patches. The sim­u­la­tion was carried out in steady, ​“cold-flow” con­di­tions, com­pa­ra­ble to a real-life air flow bench.

Opti­miza­tion Process and Results

The intake port opti­miza­tion was carried out in three steps. First, a DoE was run using a Sobol sequence to evaluate pre­lim­i­nary trends and cor­re­la­tions. Then, a pre­lim­i­nary opti­miza­tion using a sur­ro­gate model and a multi-objec­tive genetic algo­rithm was carried out to identify the Pareto frontier. These methods are fully inte­grated in CAESES®.

Finally, a second opti­miza­tion run with the same method as before was executed, to further populate and refine the pre­vi­ously iden­ti­fied Pareto frontier. Two con­cur­rent objec­tives were con­sid­ered: the dis­charge coef­fi­cient, or port per­me­abil­ity, and the tumble ratio. Addi­tion­ally, the tur­bu­lent kinetic energy in the spark plug region and the swirl motion (or omega tumble) were mon­i­tored. The whole opti­miza­tion process com­prised approx­i­mately 150 designs and there­fore CFD sim­u­la­tions in total.

The two objec­tives were – not sur­pris­ingly – anti-cor­re­lated and the influ­ence of the design vari­ables on the objec­tives was quite diverse. While, e.g., the cross-section eccen­tric­ity in the more upstream location had almost no influ­ence, the same value more down­stream had a pro­nounced, but opposite, effect on the two objec­tives. Other design vari­ables were only cor­re­lated with one objec­tive. E.g., the inlet angle had a positive cor­re­la­tion with the tumble ratio and the ellipse factor down­stream had a negative cor­re­la­tion with the dis­charge coefficient.

Several intake port designs could be chosen from the final Pareto frontier, depend­ing on dif­fer­ent con­sid­er­a­tions, whereby all the best solu­tions were char­ac­ter­ized by a pretty high inlet angle and a rather short straight length at the inlet. The one design that was selected at the end exhib­ited a sig­nif­i­cantly improved dis­charge coef­fi­cient, with an only slightly lower tumble ratio as the baseline.

Download Tech Brief

A short summary of the CAESES® intake port design capa­bil­i­ties can be found in this tech brief (PDF).

More Infor­ma­tion

If you want to hear this story in more detail, you can check out the record­ing of the webinar we ran jointly with R&D CFD. If you would like to discuss your intake or exhaust port appli­ca­tions with us, do not hesitate to get in touch! More infor­ma­tion about similar appli­ca­tions can be found in our pow­er­train appli­ca­tion section or the intake port design page.

Follow Us

If you are inter­ested in CAESES® and in CFD-driven design opti­miza­tion, then sign up for our newslet­ter. Don’t worry, we won’t bother you with too many emails. Of course, you can unsub­scribe at any time :-)