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I've currently got a mechanism that is powered via a shaft connected to a ducted fan. The ducted fan is powered by an existing air flow through the duct. I am looking to re-design the fan to increase torque/performance. The fan will be injection molded and is about 2" is diameter. With no-load, the current fan spins at 10k RPM. I need to make measurements under load, but it's significantly slower.
How can the parameters of the fan blades be adjusted to maximize the output torque?
Fan/turbine design is a highly involved process that lots of very smart people dedicate their careers to. If this is for an experiment, certainly try building one, but if this is for an application/product with efficiency requirements, I would recommend sourcing a pre-built one spec'd to the proper torque and rpm required by the load.
You can probably gain a lot of understanding in this by optimizing the fan/turbine you already have. A rule of thumb we used in water turbines was maximum power will be delivered at approximately half of the freewheeling RPM. This is probably different for gas turbines, but might be a good place to start. If it is currently loaded at 1000 RPM or less you are likely only receiving a fraction of the power your current turbine is capable of producing. Remember that you are not trying to maximize output torque(typically max at 0rpm) you are trying to maximize output power (RPM x Torque). It may be as simple as changing the gear ratio to your load or optimizing your load for your turbines maximum power RPM.
