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Giffard boiler water injectors

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picclock:
For anyone who doesn't know what I'm talking about :
http://www.bluebell-railway.co.uk/~uhaa009/bb/locos/3217/injector.html

Apart from the fact that these seem like a bit of sleight of hand magic has anyone successfully used these in a model engine ?  It does seem odd that you can take a high pressure gas, shoot it down a cone, picking up water on the way, then re-pressurise it to higher than its original level and feed it back into the boiler. How much high pressure gas is wasted in the process? Do design formulae exist for this configuration?

Failing that what sort of water injectors do you use on your model engines ?

Any help or info much appreciated.

Best Regards

picclock

inthesticks:
Hello PICCLOCK as a stationary engineer I recieved instruction on thier operation. They are finicky to operate and if found in a modern power plant are used only for emergency back-up. For model engineering they would be a great project. I believe Model Engineering Magazine did an article on this years ago, if you have access to an index you may be able to find it.

Below are 8 page scans from one of my stationary engineering books covering thier design, construction and operation with questions. Hope this helps. :thumbup:

Cheers
CB

picclock:
Hi inthesticks

That is the best info I have ever seen. Many, many thanks for taking the time to post it. I have printed out the pages and hopefully the dark clouds of ignorance are moving away.

The info you provided clearly shows and the sequence of events initiating the process (p381), something which I have not seen explained elsewhere.

>>They are finicky to operate and if found in a modern power plant are used only for emergency back-up.

I am not surprised. One of the issues with this solution is that to work well the flow must contain a lot of energy. If you have a large volume of steam this is not a problem, but on a modelling scale much of the steam energy will be absorbed by the boundary layer effect, and increasing the volume of flow would quickly deplete a model boiler pressure reserves.

If they are only used as a backup in 'modern' boilers, do you know what mechanisms are used in their place?

I will try to hunt down the model engineer article you mentioned to see if they succeeded in making one work at such a small scale.

Best regards and a (sadly) virtual  :beer:

picclock

 

chipenter:
D E Lawrence artical in ME 1986

inthesticks:
Glad you found the info. usefull PICCLOCK.You will not find injectors in lage industrial plants thier feedwater volume requiremants are to high for injectors.In smaller heating and cooling plants they can still be found. I worked one hospital heating and cooling plant with 3, 25,0000 lbs/hr. Cleaver Brooks firetube boilers.
Thier 2 main feedwater pumps were electrically driven. In the event of a power failure each boiler had its own injector mounted in its feedwater supply to provide water during the shut down proccess. Clean feedwater is important, as noted in the earlier text they will gum-up quikly. The majority of plants use electrical and steam turbine prime movers for their feedwater pumps. Steam turbines probably logging more hrs. than any other method.

Below is a section diagram of a tipical steam turbine used in feedwater service.

Cheers
CB

 

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