Introduction to Air Flow Test in Precision Parts Manufacturing - Impro Precision


Introduction to Air Flow Test in Precision Parts Manufacturing

November 14th, 2023

Mass air flow measurement provides a functional test of precision machined parts like those used in gas turbine engines. It’s important for minimizing temperature variations and vibration, preventing overheating and maximizing efficiency.

Impro Aerotek produces and repairs the highly engineered components used in gas turbines, and fully understands the critical role air flow testing fulfills. Our engineering teams perform this testing in accordance with the procedures set out in our AS9100 and NADCAP certified quality management system. Here’s an introduction to what’s involved.

Air Flow in Gas Turbines

A gas turbine ingests vast quantities of air, mixing it with fuel, burning the mixture, and directing the hot combustion gasses through the nozzle assembly to generate rotation. More air is used to cool nozzle components in order to avoid metallurgical creep and subsequent engine damage.

Stable and controlled air flow in combustion and cooling is key to maximizing efficiency and life. A particular concern on the cooling side is the risk of overcooling if air flow is too high. This increases the quantity of air drawn away from combustion which reduces overall efficiency.

Air flow measurement is performed to:

  • Verify new, precision machined components operate within design limits
  • Identify trends in condition and performance of installed parts like blades and buckets
  • Determine when repair is needed
  • Detect problems such as blocked cooling channels
  • Confirm repaired parts provide performance within design limits (variation in thickness of reapplied thermal barrier coatings will affect air flow)
  • Obtain data for matching components in the final assembly, so ensuring consistency and stability

To expand on this last point, consistency, or minimization of variation, is critical when assembling or reassembling a gas turbine. Inconsistencies can lead to temperature differentials, resulting in uneven expansion and regions where temperatures exceed safe operating limits. They can also cause vibration which will shorten component life.

Air Flow Testing

Air flow testing is performed on sophisticated test stands. These are calibrated to national standards, sited within a clean, temperature controlled room, and supplied with clean, dry air.

Each part to be tested needs a dedicated fixture that holds it in place and eliminates any leaks that would otherwise give misleading results. These fixtures need as much care and attention to their design, machining and assembly as is given to the components under test themselves.

Once the test parts are clamped into the fixture, air is supplied as detailed in the manufacturers or engine OEMs specifications. Most testing is performed with air flows of 0.001 to 2.0 lbm/sec. Results are logged and are traceable to the individual units tested, which facilitates trend monitoring and matching at assembly.

Ask us About Air Flow Testing of Precision Machined Parts

Functional testing verifies parts and assemblies are fit for purpose. Performed repeatedly over time, it provides trend data, and it enables matching of parts for assembly. It’s especially important for high precision parts like those used in gas turbine nozzle assembly components as it helps maximize efficiency and life.

Impro performs mass air flow testing in controlled conditions, on calibrated equipment, and in accordance with strict quality procedures. Please contact us to learn more about our testing services.


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