Monday, 14 November 2011

An Update

First of all let me apologise for not having posted anything in the last few months. Rest assured, things have been moving steadily onward with the Thunderchild Project!

I have been very busy in the workshop and with nozzle and injector design. This coupled with the generalities of everyday life has meant  I have had little time to post.

Workshop wise I have been re-acquainting myself with screwcutting in the lathe. As well as being important to the project generally, my acquisition of threading tools for the Harrison has allowed me to radically re-design and improve the injector. I've also had some excellent input on the injector design front from Dr. John Chinn, of the University of Manchester Institute of Science and Technology (UMIST). Dr. Chinn is an authority on atomisation and sprays and was kind enough to take time to clarify a few points for me.

To try to get some idea of the efficiency of the injector design, I've been looking at a technique called "Shadow Sizing". Essentially this involves taking a photograph of the spray against a brightly illuminated graticule. It is then possible (with some effort) to gauge droplet size, distribution and number. I've been trying to work out a scheme to implement this, and thinking about software to automate the particle counting/sizing task. As an aside, I have put this notion forward for the BBC Radio 4 "So You Want to be a Scientist" search for amateur research ideas. I don't hold out much hope for it, as there usually seems to be an environmental, or "primary school nature table science" type of bias to the chosen entries. Still, you never know.

The design of the nozzle and convergence is well advanced, and this will most likely be the next component to be machined. The extra area required to achieve the design L* figure was calculated using the formula for the frustum of a cone. I will post the full nozzle and convergence design calculations in due course.

Some time ago I told you about the new tilting rotary table, well here it is:-

And here, tilted:-

Last but not least...the British Reaction Research workshop is moving! Yes, I have bought a new, larger house, and the space for the workshop is insulated and has access from inside the house. It will be much more comfortable in the colder months...I still get chills when I think about machining the components for the chamber last winter, when it was minus 10 degrees celsius outside!

Inevitably, it will take some time to get the workshop up and running again. I will give you some pictures of the move and set up, and I'll try to use some of the time to start giving you the much vaunted injector details. Do stay tuned.

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