In this test setup, the measured thrust is not appropriate. So can anyone suggest any modification in this one ?
P.S. Refer the link to youtube for the setup which was replicated.
https://www.youtube.com/watch?v=GDuo8gmfn9k
Dear Tapan Jansari,
the thoughts that come to my mind after looking at your pictures and viewing the linked video are the following:
- What thrust exactly is to be measured? Fixing the propeller in space will lead to a thrust value for zero speed with respect to the still air far away from the setup. In general, it would seem to me that thrust values can be expected to depend on the speed of the propeller with respect to the still air far away from the propeller. In that regard, the setups shown would be a special case. In other words, the details of the air flow around the propeller are important.
- Assuming this special case, I would recommend to find a way of mounting the propeller on a force scale in such a way that the scale / measuring device does not interfere with the air flow around the propeller. In the setup shown, the thrust might be underestimated by the measurement configuration, since the exhaust air will compress the air near the scale and the table to some degree, increasing the local pressure. I am not sure whether this is a significant effect or not for the flow conditions in question. But again, in general, I expect the details of the air flow around the propeller to be important.
- A detail, perhaps, but in the linked video, the axis of the propeller is off-center with regard to the scale. In the worst case, there may be a certain reduction of the force reading due to this, but that certainly depends on the details of the scale itself as well. I would make sure that the force to be measured does not apply a torque to the measurement device, it should be a linear force only.
This is what comes to my mind at the moment. I hope that this is of some help.
Best regards and successful experimentation!
Bjorn
Dear Tapan,
I could not see the videos as not permitted in our office...so please excuse me if my observations are wrong as they are made only by seeing the pictures...
I completely agree with Mr Bjoern....
One very basic mistakes that you can do -> dont forget zeroing the machine after putting test article on it....
But more importantly what makes to think you that thrust measurement is not appropriate? Is it because it do not match with your calculations/predictions?
If so....please check your calculations again....If testing is done in proper way and all the instruments are calibrated properly and all the assumptions are reasonable, there is no point in doubting the test. In such case you should doubt your predictions and improve your simulation/calculation so that you come closer to the real world i.e. test.
Regards
Thank you, Mr. Bjoern and Mr. Naveen for your detailed explanation related to the setup. And I found the solution to the stated problem.
The problem was with the propeller I was using. It's variation in angle of attack was inappropriate. I got satisfying results when I replaced it with a new one.
Also, I shall take care of your suggestions regarding the air flow around the weighing scale.
Regards.
- Badges
- Science topic
- Similar topics
- Engineering
- Mechanical Engineering