- 3 January 2008 -

Filtration software: Shedding light on fluid flow system design

Design analysis and simulation techniques have come a long way from the days of slide rules and drafting tables. The next step, claims Jim Spann of Blue Ridge Numerics, is putting fluid flow simulation capabilities into the hands of multi-tasking design engineers, potentially saving costs and energy further along in the filtration process.

Until recently, the development of specialist fluid flow systems required a series of expensive and time-consuming analytical activities, involving laboratory tests and complex calculations. Understanding the internal flow structure of a new design presented a significant challenge. With no means to see what is going on inside, the only way to prove new designs has been to build physical prototypes and test them in the lab. Each modification made to the initial design demands a new physical prototype and a new round of testing, which is costly and time-intensive. However, analysis in the engineering world is changing. No longer the preserve of specialists in test labs with powerful supercomputers and arcane software, techniques like finite element analysis (FEA) and, increasingly, computational fluid dynamics (CFD) are being used by a broad spectrum of design engineers to test design and performance fundamentals at the concept stage, when major changes are relatively inexpensive.

CFD is the simulation of flows, such as the flow of water through a filtration system or a pump. CFD software has been around for more than 30 years but it has thus far done little to improve design in the filtration industry. Once difficult to learn, time consuming and too expensive, new software developments make it possible to model flow and run comparative analyses early on in the design process.

Integrating flow and thermal simulation within a computer-aided design (CAD) environment, means that the operator doesn't have to be a dedicated CFD or computer-aided engineering (CAE) expert to solve complicated and challenging design problems. Applications are used by multi-tasking engineers during early stage product development, when innovation and intelligent problem solving are most cost effective allowing companies to gain critical insight into product performance early on in the design process. It cuts development time, reduces the amount of physical prototyping and testing required and enables early exploration of new fluid flow systems in a three dimensional virtual world.

Whereas most traditional CFD applications are designed to offer external fluid and heat transfer simulations, upfront CFD tools like CFdesign include specialist filtration capabilities, which enable designers to calculate pressure drop and velocity within an internal volume. The engineering information made available includes transient details of a whole machine's response to fluid flow on any time scale, full performance curves, impeller radial loading, analysis of single blade passage and analysis of intermeshing gear parts: all of which are almost impossible to determine from lab tests.

Engineering in the dark

Elster Kromschroeder manufactures components and systems for safeguarding, measuring and controlling gas in an environmentally friendly way. The company's portfolio covers domestic and industrial gas meters, filters, pressure regulators, safety valves and controller components for heating systems as well as systems for measuring and controlling industrial heating processes. The product development team at Elster Kromschroeder has used CFD software for ten years, enabling the product development team to better understand the internal flow structure of its products.

Prior to the introduction of CFdesign, flow optimisation in gas-using components was difficult because there was no way of knowing exactly what was happening inside them. Of course the design characteristics of physical prototypes were examined on the test bench, but there was often no definitive understanding about what was happening inside the valve, flaps and control systems since these areas were not visible. Improving the design relied on the engineer's experience alone, but the cost and time associated with building and testing physical prototyping would erode profit margins. The company used fluid flow simulation software to reduce the time it took to develop, test and prove new product designs and this enabled the design team at Elster Kromschroeder to compare several new ideas and designs within a short time frame.

"We focused on the efficiency of the gas-containing components in the process," says development engineer Klaus Midding. "It allowed us to see the effects of geometry changes by adjusting the model in our CoCreate CAD system. Our integrated process tapped the potential of a higher number of evaluated solutions and brought the most effective one to production in a much shorter time. Often just one physical prototype is enough for validating the construction."

Introducing CFD analysis and simulation techniques to the concept stage of the design process rather than using it for final validation when it is too late to make changes can cut development time, reduce the amount of physical prototyping and testing required and gain critical insight into product performance and efficiency early on in the design process.

Real world innovation

Another company that has benefited greatly from CFD is Vee Bee Filtration, a manufacturer of specialised filtration products for commercial and industrial applications. The use of upfront CFD software has transformed Vee Bee Filtration's business model from one that offered a limited range of standard products to one with the agility to deliver completely new, custom-made, high quality solutions to meet customer demands.

Until the establishment of a dedicated in-house R&D department to help deliver bespoke filtration solutions, the company was only able to offer a limited portfolio of standard products. "Clients were increasingly requesting bespoke products, which needed to be designed and engineered from scratch but at this time, we were using standard calculations to make standard products," explained Napoleon Motaban, development engineer. "We could scale them up or down, but apart from that we had very limited flexibility in terms of bringing new products to market."

"Upfront CFD is a vital part of our R&D offering," states Motaban. "It means we can test new designs for pressure drop and velocity without having to run expensive lab tests for every product. We conducted lab tests against results we achieved using CFdesign and found it to be well within our range of accuracy."

Vee Bee Filtration was recently commissioned to design and manufacture a new strainer for a nuclear power plant. Crucially, the strainer needed to be designed in a wide range of sizes, with CFD results determining the K factor for each size so that only viable options would make it to the physical testing stage. Before the use of CFD, each size would have to have been modelled into a physical prototype and then laboratory tested, which would lead to excessive costs.

For companies with engineering departments full of multi-tasking engineers whose responsibility it is to get product to market, the true value of CFD lies in using it in the product development process and testing design fundamentals at a point when major changes cost very little. However, it can do much more than simply enable manufacturers to lower the cost of product development: it can be instrumental in the creation and evolution of a far more competitive business model. Instead of manufacturing a few products well and hoping that the market continues to want them, providers can now use CFD to bring bespoke solutions to market quickly and cost effectively, meeting customer demand for tailor-made products that fulfil a specialist need and helping actively to drive innovation within the filtration industry.

Contact:
Jim Spann
www.cfdesign.com