CFD software helps vent pressure and vacuums inside gasoline tankers.
Next time you see a gasoline tanker rolling down the highway, you might want to give a silent thanks to Betts Industries. Betts makes the vents on top of gasoline trailers that help ensure safety by normalizing pressure and vacuums that build up within the tank. Flow-rate tests of the company’s newest vent designs, optimized using CFdesign software, show 33-percent greater efficiency than previous models.
Betts has long been associated with the oil industry, from its beginnings in 1901 as an iron foundry producing oil-field equipment to its current position as a provider of components for highway cargo tanks.
In 1946, Betts began making manifold valves for use with petroleum tank trucks. Since then, the company has built its product line to offer a wide range of components used on highway cargo tanks transporting petroleum, chemicals, and other materials. Not wanting to sit on its laurels, Betts has taken advantage of the latest technologies for conceptual design through manufacturing.
The latest move in Betts’ quest to continually increase efficiency and quality is implementing upfront computational fluid dynamics (CFD), which provides the ability to conduct flow and thermal simulation within an MCAD environment.
The aluminum die-cast body of the company’s current pressure/vacuum vent was modeled in Pro/ENGINEER. In designing the new model, Betts wanted to use native Pro/ENGINEER data to conduct design trade-off studies without having to hire a full-time CFD specialist or outsource the work. The company found its solution in CFdesign, upfront CFD software from Blue Ridge Numerics.
CFdesign enables multi-tasking engineers to perform computational fluid dynamics analysis early in the design cycle, when it is most cost-effective to explore and validate designs. Virtual prototyping of different design options replaces traditional testing methods, saving the more costly physical prototyping for final design verification.
“We wanted software that was tightly integrated with Pro/E, and didn’t require the specialized expertise that is usually needed to solve complex CFD problems,” says Kyle A. Anderson, the design engineer in charge of CFD analysis for the pressure relief vent project.
Although Anderson minored in finite-element analysis in college and had used ANSYS software to simulate static, dynamic, and heat-transfer models, he didn’t have any direct CFD experience. Within three days of installing CFdesign, however, he had generated a full-motion CFD simulation using the Pro/ENGINEER model.
“CFdesign fit naturally into our existing workflow without adding layers of complexity,” Anderson says.
Integration and automation in CFdesign are made possible by the software’s finite-element approach. Based on mathematics rather than the physics-based methodology of traditional CFD programs, CFdesign naturally accepts different shapes and geometries defined within the MCAD model. The finite-element approach enables Blue Ridge Numerics to incorporate intelligent algorithms within CFdesign that relieve the user from learning the complex operations normally required for accurate simulations.
For Betts Industries, integration between Pro/ENGINEER and CFdesign is not just about ease-of-use — it cuts right to the integrity of the geometry, according to Anderson. When Betts makes a geometry change in Pro/ENGINEER, it is automatically recognized within CFdesign, which adapts to the change without loss of data.
“CFdesign uses native Pro/E geometry, so there is no threat of losing geometry intelligence through data porting or translation into an analysis environment,” says Anderson. “The process ensures efficiency and data integrity.”
Within the first day of running the model in CFdesign, Anderson generated 3D visualizations showing flow characteristics that he had not seen before. Over the course of the next two weeks, he tested different designs to analyze and compare critical data such as flow velocity, flow magnitude, and pressure differential under varying conditions.
“I could easily see the flow inside the model, where it was moving quickly and where there were pressure pockets, something you can’t do in real life or on a flow bench,” Anderson says. “We were able to run all our scenarios with CFdesign and be confident of the results before we moved on to physical prototyping.”
Upfront CFD results showed that a relatively small design change yielded dramatic improvements, increasing the flow rate from 1,750 standard cubic feet per hour (SCFH) to 2,336 SCFH. The process took a total of about two weeks, compared to the estimated six to eight weeks that would have been required using physical prototypes, according to Anderson.
The finalized Pro/ENGINEER model was fed into a fused-deposition modeling (FDM) system to produce a rapid prototype made of ABS material. The prototype was then tested on Betts’ critical orifice flow tank to verify the CFdesign results. The differences between the actual flow from the tank testing and the CFdesign results were very small — 2.79 percent for pressure flow and 3.85 percent for vacuum flow, with the physical prototype tests showing slightly better flow improvement than the computer simulation.
Based on the close correlation between the CFdesign results and the physical testing, Betts is moving ahead on tooling for the new pressure relief vent. When the first of the newly designed vents hits the road this month, Betts says it will be delivering a product that is significantly more efficient than its predecessor. And, thanks to upfront CFD, it will be designed in one-third of the time it would have taken in the past.
Bob Cramblitt is a freelance writer based in Cary, NC. More information on CFdesign is available from Blue Ridge Numerics Inc., 3315 Berkmar Dr., Charlottesville, VA 22901, by calling 434 977 2764, or at www.cfdesign.com.
PULL-QUOTE:“The process took a total of about two weeks, compared to the estimated six to eight weeks that would have been required using physical prototypes.”Captions:Use with both PD71Auto01a and PD71Auto01Ba
Pro/ENGINEER models show different perspectives of a Betts Industries pressure relief vent.PD71Auto01Ca
Visualization of flow inside the moving, pressure-driven vent shows initial impingement of flow during the first microsecond of movement.
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