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ANALYSIS OF A PNEUMATIC CHECK VALVE
The practical view of CFD problems that differentiates CFD Engineering from the others can be successfully used in the design process of pneumatic devices. This was proved by one of our consulting jobs completed some weeks ago in cooperation with the Hungarian development center of the worldwide known solution provider in automation and pneumatics. The place of CFdesign in the process of product development, the so called Upfront way is described in this article . What is released here is the concept working in real life.
The job was to increase the volumetric flow through a pneumatic check valve. The project was started with the simulation of the original design. We received the production ready geometry from our partner. It took only one hour to get rid of the manufacturing clearances and put the inlet and outlet tubes and extra volumes that helped to divide the solution domain into parts. (We would like to highlight the 1 hour because at the end of the article we will make a summary on the time required to complete the project.)
After setting the analysis parameters, mesh sizes and performing test runs (altogether 1 hour again) the simulation of the original condition was started. According to the log file the analysis reached converged solution after 6 hours and 7 minutes. The picture shows the result of the original geometry. It was shown that the bottleneck of the flow was at a different location than the manufacturer thought and made calculations with. This simulation showed exactly where to look for some design changes.
During the next three days three different design changes were analyzed. One changed the housing, the other two focused on the floating piston that shuts and opens when pressure decreases or increases. The design changes were performed in the 3D CAD and each design was loaded back into CFdesign and analyzed. It was required to see what design change gave what modifications in the volumetric flow value. (Let us count a bit: we were at four days and had four converged simulations on four different designs. Based on them the decision could be made on how to progress with the development). On the fifth day of the project the decision was made that the two modifications of the piston could be combined into one part because this could be also manufactured and it would give the best results.
On the sixth day the last analysis was completed during the usual 6 hours runtime. The results: compared to the original geometry the new one could produce 10.5% more volumetric flow, without decreasing the structural strength and sealing capabilities of the valve. The 10.5% was important because this was missing from the required performance.
It was the success of the joint efforts in a way that the development had been made for 2 months with shorter pauses and the deadline for ordering the dies came closer and closer, but 10% of volume flow was still missing. The manufacturer made measurements on prototypes but a test rig does not allow you to look into your product.
The CFD simulation made with CFdesign showed that the bottleneck was on a different location that it was believed. Knowing this, during six days comparing different designs the problem was solved, the dies are scheduled on time.
This is what we call a success story.
The above article, like others before was issued with the written approval of our partner.
2007.11.12 - CFD Engineering Hungary Kft. |
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