410 Hamilton St.,Washington, Ill. 61571
'Why and how does it work?'
You old time engineers have used an injector most of your life, but you don't know how or why it works! At least I haven't found a single man who could tell me. Ask any number of Steam Engine Operating Engineers how and why a boiler, feed water, steam injector works and you may get as many different answers as you have engineers nothing in the way of a technical, scientific or through explanation. You are more likely to get and 'I don't know' answer or something like this 'Why any good engineer knows how it works. You use steam from the boiler through a steam jet, blowing through a suction jet, that syphons the water from your supply tank, that in turn is blown through a delivery jet and into the boiler. Now that was simple, wasn't it?' Simple all right, it didn't tell you a thing. I would still insist on 'How and Why'. The explainer starts out again. 'Well it goes like this' his voice trails off in thought. 'We know it works and why it doesn't work now go see that fellow over there, he might give you the scientific answer'. And so it goes. I've asked mechanical engineers the question (now a days they are too young and most likely never heard of the steam injector for boiler water feed). 'I'll go to the library and look it up and let you know'. 'I'll take the question into the factory and put it up to my fellow engineers'. I received no help from an inquiry directed at a well known manufacturer of injectors.
Now, here is what throws them all: the problem simplified is this: 'How can you take steam from a boiler, say at 100 lbs. for example, pick up water with it and force it back into the boiler on the water side which is under 100 lbs. pressure, and equal back pressure, also?'
It is easier to see why an EJECTOR (not injector) works, when you have a pressure differential, or pressure drop, to allow the thing to work. You can't pick yourself up with your own bootstraps, nor are perpetual motion machines possible; this is why a patent was refused on the injector when first submitted to the United States Patent Commissioner, until he had seen it work.
Simply stated the injector works because the velocity (speed) of steam is much greater than the velocity of water. (Steam from the top of the boiler, water from the bottom of the same boiler) and the sufficient 'coolness' of the incoming water to be able to condense ALL of the steam. The ability of the greater speed of the steam, which picks up the water by way of a syphon action, and drives the incoming water at great speed against the boiler water, which would flow out of the boiler at a lesser speed, at the same time the steam must 'get lost' condense entirely in the cool incoming water. Water passing through the injector must be all liquid so that the incoming water will have enough weight to drive against the boiler water pressure. Thats why the steam must also condense.
As you know, hot water or a hot injector refuses to work. It can't condense enough steam to give the water enough weight to buck the boiler water, even though it still has velocity.
I started this question as a small boy, when I first saw the injector work. At the age of 50 (last year) I found the answer at last! A booklet 'STEAM ENGINE GUIDE' available through this magazine was very helpful.
'More Power' to all, and to all in fun I submit this writing.