Why are most props unducted?
Thread Starter
Join Date: Jun 2014
Location: Long Beach
Age: 32
Posts: 2
Likes: 0
Received 0 Likes
on
0 Posts
Why are most props unducted?
Hi guys.
I've been wondering why most props are unducted? Having a duct around the prop will increase safety of bystanders, decrease noise, and increase efficiency by reducing blade tip losses.
Thanks
I've been wondering why most props are unducted? Having a duct around the prop will increase safety of bystanders, decrease noise, and increase efficiency by reducing blade tip losses.
Thanks
At usual propeller speeds, with a usual number of blades (5 or less), the airflow efficiency saving of ducting is less than the extra weight, drag and complexity of adding the duct.
As the number of blades and tip speeds increase the advantage of ducting is clearer. However even here the advantages of removing the duct and instead using clever blade design have been thought about (google "NASA/GE Unducted Fan").
As the number of blades and tip speeds increase the advantage of ducting is clearer. However even here the advantages of removing the duct and instead using clever blade design have been thought about (google "NASA/GE Unducted Fan").
Last edited by Dont Hang Up; 30th Jun 2014 at 11:09.
Wonder what became of the unducted fan (UDF)? I'm Sure I remember experiments involving such engines being fitted to a B717 a number of years ago.
Gnome de PPRuNe
Join Date: Jan 2002
Location: Too close to Croydon for comfort
Age: 60
Posts: 12,618
Received 293 Likes
on
161 Posts
MD80 UDF was demo'd at Farnborough in 1988.
Join Date: Dec 1999
Location: UK
Posts: 2,584
Likes: 0
Received 0 Likes
on
0 Posts
I'm not at all sure that a ducted propellor would increase efficiency as drag losses in and around the duct would be much larger than the relatively small improvements at the blade tips. Not to mention the extra weight of the duct and supporting structure.
If they were more efficient we'd see them, as it is we see virtually none and for good reasons.
I'm not sure that bystander safety is relevant. What would bystanders be doing close to running aircraft?
Ducted props are pretty pointless in 99.9% of applications.
If they were more efficient we'd see them, as it is we see virtually none and for good reasons.
I'm not sure that bystander safety is relevant. What would bystanders be doing close to running aircraft?
Ducted props are pretty pointless in 99.9% of applications.
