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Sunday, May 1, 2011

High Voltage Electrode Schlieren Images

This week was another busy week but I managed to get some time to experiment a bit. I decided to look a little more closely at the airflow around a high voltage electrode with the Schlieren setup. To do that I put together a quick test rig that allows me to raise and lower an electrode in front of the parabolic mirror. I'm working on editing a video of what I saw going on but in the meantime I have a couple of pictures. The first picture below is of the test setup.
High Voltage Electrode Schlieren Setup
The black cylinder near the bottom of the mirror is a plastic tube mounted to a small piece of wood. In the center of that is a smaller plastic cylinder that has a rounded and blunt electrode attached to it. There is a wood 'lever' going off to the left side of the photo that I can use to raise and lower the electrode by sliding it in the larger tube. The red wire at the top is connected to a sewing needle that is mounted right above the movable electrode that I just described. The red wire of course is connected to the power supply. What does all this mean?? I don't know but I'm going to try and figure it out and explain it to you. Continue reading to find out!

As I mentioned the point of this is to look at the airflow around the electrodes when there is a high voltage present but not arcing. When there is arcing the airflow is going all over the place and there is a lot of heat generated - which causes even more airflow. To me that isn't too interesting but it sure looks neat. What I am doing is raising the lower electrode until I can see airflow around the electrode but no arc. Another thing that I am doing is letting it arc then moving the electrode away until it stops arcing.

From playing around with this setup I can see there is a difference between the two scenarios. Watching the airflow after there has been an arc is interesting because the arc creates a lot of ionized air and the airflow follows it. Additionally there is a very fine stream of fast moving air coming off the point of the needle and flowing down to the lower electrode. I believe this is the airflow that is creating lift in Ionocrafts. There isn't a lot of airflow in this setup but then again the lower electrode isn't that large. I'll go into this more below.
Another thing that I want to look at is how the air is flowing down and away depending on the size of the lower ground electrode in other (more complicated) words The Biefeld-Brown effect and the force created by an asymmetric capacitor. Click HERE to get some more info about what I am talking about. Time for an exciting picture!
High Voltage Electrode Schlieren Airflow Image
Above is the picture you have been waiting and entire lifetime to see! OK maybe not but it is a neat picture if I do say so myself. Give me a sec to pat myself on the back. Enough of that, the picture above shows how the air is flowing around the electrodes and you can just make out the needle as a dark line above the lower electrode.
Another interesting thing that I noticed was some airflow coming off the needle above the point of the needle. This next picture shows that airflow pointed put by the yellow arrow. The end of the needle is by the red arrow. In the video that I am editing it is even more pronounced and I'll post that later. 
High Voltage Electrode Schlieren Airflow Image
That is about all I managed to get done this week. I hope to continue to review the video and edit it to see what else is going on. Also making different shaped electrodes and trying different voltages would be fun.
As always if you have any questions, comments or want to chat about this leave a comment or send me an email.

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