By Steve Back
New York Blower Company
Willowbrook, Illinois
Performance curves are among the most crucial and frequently requested documents from fan manufacturers, second only to dimensional prints. While many request these documents, not everyone fully understands their significance or maximizes their potential.
Fan performance curves are generated through laboratory and/or field testing. Fans are tested in accordance to international standards such as AMCA 210 and ISO 5801 for laboratory testing along with AMCA 203 and ISO 5802 for in-situ (field) testing. Data points are collected at a set speed while the flow is modulated from full closed to full open, creating a fan performance curve representing the fan’s capabilities. Additional testing is usually performed at different speeds to get a comprehensive picture of the fan's aerodynamic and noise performance.
Performance curves serve multiple functions. They graphically depict basic performance data such as Fan Volume Airflow Rate (Q), Mass Flow Rate (ṁ), Rotational Speed (N), Fan Pressure (P), Sound Pressure Levels (Lp), Fan Efficiency (η), and Fan Power Input (Hi). Beyond these raw metrics, the curves illustrate crucial performance characteristics of various fan types, including areas of instability and the rate of change between airflow and pressure.
While capacity tables published in literature offer a convenient way to catalog this data, they are essentially simplified versions of the test results. Working with the source document — the performance curve itself — provides additional valuable information, particularly when determining capacities at varying speeds or conditions beyond published capacity tables. The data collected during testing also serves as the foundation for developing computer selection programs and published capacity tables that system designers and end users rely upon.
With a solid understanding of performance curves, engineers and technicians can make informed decisions about fan selection, system modifications, and the suitability of a fan for specific applications. These curves become invaluable tools for determining the feasibility of fan or system alterations and calculating resultant speed and power requirements.
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