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View Full Version : How to calculate the pressure ratio of a fan ?



kemo1988
28-Apr-10, 06:18 PM
Hi everyone

I am working on my graduation project which is hovercraft, and i am using integerated system. The fan i got is 80 cm dia. and has 5 blades and the available power is 13 hp @ 3600 rpm.

I am sure that it is going to produce a good thrust, but here i am worried about the lift, i want a pressure of about 0.02 bar ( gauge ), and i dont know any data about this fan, so i was asking: how can i calculate the pressure ratio of this fan in terms of power, speed, blade cross section and diameter to know if the lift will be succsesful or not.

I am also sure that it will produce the required flow rate, but here i am concern about the pressure.

please need help .

broad5186
28-Apr-10, 07:26 PM
hi

what size is your craft

my single seater integrated craft is based on a skirt pressure of 600Pa (0.006 Bar) which is well below your estimation and i run 5 blades through a 90cm duct but with 50Hp

there is software available to give pressure/flow rate of fans at various speeds/pitches but i don't have it sorry, other people who post here may be along to help you - good luck with your project

tony

kemo1988
28-Apr-10, 07:54 PM
hi

what size is your craft

my single seater integrated craft is based on a skirt pressure of 600Pa (0.006 Bar) which is well below your estimation and i run 5 blades through a 90cm duct but with 50Hp

there is software available to give pressure/flow rate of fans at various speeds/pitches but i don't have it sorry, other people who post here may be along to help you - good luck with your project

tony

well, i calculated the pressure from this relation P=F/A

- the area which the air is trapped in is 2.2 m2
- and for 200 kg ( 2000 N ) weight
it gives about 0.0091 bar ( i was wrong sorry )

but i am using the closed type skirt, like this one http://amasci.com/amateur/hovercft.html

but i am not going to make it circular, do you think this fan at this power will give the required pressure.