Post by ERJets on Jul 7, 2008 12:13:39 GMT 8
Hi all,
It will be good to know how a duted fan works and here are few gerneral rules of DF for those who are keen of knowing.
On a scale model,ducted fans are an internally ducted performance fan which takes in air from the inlet and blow air out an exhaust tube to generate forward thrust. The air enters an impeller spinning at high RPM which propels pressurized air out of its exhaust at increased pressure and velocity.
A ducted fan thrives on the air fed into it so too little air will starve the fan, thus preventing it from perform at its optimum design point.
Conversely, inlets that are grossly oversized can have the same effect.
Well, that is because a ducted fan can only process a given amount of air at any particular time, so too much air will hamper performance and also will increased drag from the large inlets.
To have your ducted fan performs at it peak, It will be good to have inlets sized to approximately 90-100% of the Fan Swept Area (FSA).
Btw, bigger inlet is not always better as inlet sizes can be less, which can actually increase your top end speed but will affect the takeoff performance. Though, restricting the inlet too much can result in the fan starving for more air no matter how fast the aircraft is travelling.
Exhaust outlets are generally sized to approximately 75%-85% FSA. Choking down airflow at the exhaust will increases exhaust velocity which will increase top end speed of the aircraft.
However, choking down the exhaust too much will back pressure the fan resulting in degraded performance. Additionally, a larger outlet area will increase the static thrust of the system, but lower the top end speed of the aircraft. The areas suggested above represent a good compromise between static thrust and exhaust velocity.
I have heard some people claiming that having more static thrust can make his model fly faster, which I personally think that It is not ture, Having greater static thrust will helps on ROG, however I dont think it will increase the top speed of the model.
Here comes the figures on EDF , Watts and amps is the power and current of a running EDF system.
Amps is the measurement for electrical current while Watts is the measurement of power being generated.
Amps is a measure of efficiency of the system and is related to the wind of the motor combined with the source battery and how the motor is loaded.
Additionally, better quality motors will run more efficiently with the same power with lower amps than those lower quality motors.
Watts is the measure of power of the EDF set up. 1 hp = 746 Watts.
It is good to keep an eye on these high performance set up as high amps + high power = heat = overheated motor at the end of my flying section. Btw, Watts will vary accordingly depending on the size of fan/motor combination.
So what is a best set up?? (I heard this alot)
Well, to me there is no best EDF setup and the best set up is the one that you are happy with its performance.
Numerous combinations are possible on a same model depends on your flying style.
It will be good to know how a duted fan works and here are few gerneral rules of DF for those who are keen of knowing.
On a scale model,ducted fans are an internally ducted performance fan which takes in air from the inlet and blow air out an exhaust tube to generate forward thrust. The air enters an impeller spinning at high RPM which propels pressurized air out of its exhaust at increased pressure and velocity.
A ducted fan thrives on the air fed into it so too little air will starve the fan, thus preventing it from perform at its optimum design point.
Conversely, inlets that are grossly oversized can have the same effect.
Well, that is because a ducted fan can only process a given amount of air at any particular time, so too much air will hamper performance and also will increased drag from the large inlets.
To have your ducted fan performs at it peak, It will be good to have inlets sized to approximately 90-100% of the Fan Swept Area (FSA).
Btw, bigger inlet is not always better as inlet sizes can be less, which can actually increase your top end speed but will affect the takeoff performance. Though, restricting the inlet too much can result in the fan starving for more air no matter how fast the aircraft is travelling.
Exhaust outlets are generally sized to approximately 75%-85% FSA. Choking down airflow at the exhaust will increases exhaust velocity which will increase top end speed of the aircraft.
However, choking down the exhaust too much will back pressure the fan resulting in degraded performance. Additionally, a larger outlet area will increase the static thrust of the system, but lower the top end speed of the aircraft. The areas suggested above represent a good compromise between static thrust and exhaust velocity.
I have heard some people claiming that having more static thrust can make his model fly faster, which I personally think that It is not ture, Having greater static thrust will helps on ROG, however I dont think it will increase the top speed of the model.
Here comes the figures on EDF , Watts and amps is the power and current of a running EDF system.
Amps is the measurement for electrical current while Watts is the measurement of power being generated.
Amps is a measure of efficiency of the system and is related to the wind of the motor combined with the source battery and how the motor is loaded.
Additionally, better quality motors will run more efficiently with the same power with lower amps than those lower quality motors.
Watts is the measure of power of the EDF set up. 1 hp = 746 Watts.
It is good to keep an eye on these high performance set up as high amps + high power = heat = overheated motor at the end of my flying section. Btw, Watts will vary accordingly depending on the size of fan/motor combination.
So what is a best set up?? (I heard this alot)
Well, to me there is no best EDF setup and the best set up is the one that you are happy with its performance.
Numerous combinations are possible on a same model depends on your flying style.
