How An Injector Works: Difference between revisions
No edit summary |
No edit summary |
||
| Line 12: | Line 12: | ||
The usual explanation is that an injector works because the steam imparts sufficient velocity to the water to overcome the pressure of the boiler. That is true, but is simply a statement of fact and gives no clue as to how we might have discovered the answer. So, now you have your finger on the puzzle. The answer tells you "why" an injector works and now you should just like to know "how" it does it. | The usual explanation is that an injector works because the steam imparts sufficient velocity to the water to overcome the pressure of the boiler. That is true, but is simply a statement of fact and gives no clue as to how we might have discovered the answer. So, now you have your finger on the puzzle. The answer tells you "why" an injector works and now you should just like to know "how" it does it. | ||
We'll first take a look at some of the goings on the inside of a boiler. Assume the internal pressure to be 180 pounds. That will be 180 pounds per square inch whenever it is measured. A thermometer placed inside will show that the surface water and the steam are at the same temperature, 379°. But the steam contains more heat than the water. After the water is heated, it requires still more heat to break up the drops of water to make steam. This heat is stored up in the steam and is known as the transfer of energy. The stream not only exerts a pressure of 180 pounds per square inch, but can also expand eight to twenty--six times its original volume. Water under the same pressure would be discharged in a solid jet with no expansion. One pound of steam is capable of much more work than one pound weight of water because of the heat which has been used to change it to steam. This can be seen by comparing the velocities of discharge from a steam nozzle and a water nozzle, both under 180 pounds of pressure. Steam will expand while issuing, and reach a velocity of about 3600 feet per second (fps) at the end of the nozzle. Water, having no expansion, will have a velocity of only 164 fps, only about 1/22 of that of the steam. | |||
== External Links == | == External Links == | ||
* [https://www.chaski.org/homemachinist/viewtopic.php?t=111293 "How An Injector Works", <i>Chaski.org</i>] | * [https://www.chaski.org/homemachinist/viewtopic.php?t=111293 "How An Injector Works", <i>Chaski.org</i>] | ||
Revision as of 18:03, 1 February 2022
See also Injector.
- Last month (February 1976) I mentioned an article appearing in the Riverside Live Steamers Chronicle, written by Dick Bagley, and entitled "HOW AN INJECTOR WORKS," and offered to print it if there were enough requests. Harry Dixon sent me a copy, although I had saved one myself, with permission from Dick to use it, which is not a request. It means, "print or else..."
- Bill Tuggle, Editor
By Dick Bagley
The usual explanation is that an injector works because the steam imparts sufficient velocity to the water to overcome the pressure of the boiler. That is true, but is simply a statement of fact and gives no clue as to how we might have discovered the answer. So, now you have your finger on the puzzle. The answer tells you "why" an injector works and now you should just like to know "how" it does it.
We'll first take a look at some of the goings on the inside of a boiler. Assume the internal pressure to be 180 pounds. That will be 180 pounds per square inch whenever it is measured. A thermometer placed inside will show that the surface water and the steam are at the same temperature, 379°. But the steam contains more heat than the water. After the water is heated, it requires still more heat to break up the drops of water to make steam. This heat is stored up in the steam and is known as the transfer of energy. The stream not only exerts a pressure of 180 pounds per square inch, but can also expand eight to twenty--six times its original volume. Water under the same pressure would be discharged in a solid jet with no expansion. One pound of steam is capable of much more work than one pound weight of water because of the heat which has been used to change it to steam. This can be seen by comparing the velocities of discharge from a steam nozzle and a water nozzle, both under 180 pounds of pressure. Steam will expand while issuing, and reach a velocity of about 3600 feet per second (fps) at the end of the nozzle. Water, having no expansion, will have a velocity of only 164 fps, only about 1/22 of that of the steam.