|
Post by nemesis on Dec 26, 2007 21:46:30 GMT 1
I'm watching an old classic at the moment, "The enemy below" and at one point the captain, Robert Mitchum tells the engine room that they're making smoke and he doesn't want to see that at dawn.
How did they prevent the production of smoke, assuming they have to burn the same fuel as when smoke is being produced?
|
|
|
Post by Mark on Dec 27, 2007 2:40:53 GMT 1
Ah, an interesting question. I'm glad you asked that.
Pauses to don anorak !!
You just know you're going to get bored with a long, drawn out explanation now, don't you ??
Being steam ships, they had boilers. You have fuel pumps to put fuel into the combustion chamber, via fuel atomising nozzles. These also have an air or steam supply to atomise the fuel (but that's not relevant to your question). You also have fans to blow the combustion air into the combustion chamber. Big marine boilers need a lot of air to work properly. You can vary the amount of air being blown into the boiler. These days we use electric fans and have movable flaps that control the amount of air. I think that old steam ships sometimes used steam turbine driven fans, and you could vary the speed of the fan easily (I stand to be corrected on the detail).
Oi !! You at the back of the class. Yes, you Nemesis ! WAKE UP !! (Black board rubber flys through the air)
You vary the amount of fuel according to how much steam you need to generate (or how fast you want to go in simple terms). You vary the amount of air to match the amount of fuel you put in the boiler the get optimum combustion. Get it just right and there is very little smoke produced. Too much or too little air, and you get smoke.
|
|
|
Post by nemesis on Dec 27, 2007 11:53:26 GMT 1
A great explanation, matey. Thanks for that. I take it then, that the way they created a smoke screen was just by altering the fuel/air mixture in the same way.
PS: expect to hear from my lawyer reference assault with a deadly board rubber. I'm very delicate, ya know.
|
|
|
Post by Mark on Dec 28, 2007 7:43:01 GMT 1
I don't know if ships ever deliberately made a smoke screen, cept in the movies (shortly before they open the sea cocks ). However, yes. Increase the air too much and you get white smoke. Too little air makes black smoke. I thought you were a roughty toughty Sgt Major, not a bleedin poof
|
|
|
Post by nemesis on Dec 28, 2007 11:16:57 GMT 1
I AM a roughty toughty Sgt. maj but I'm also finely tuned instruments of war. Besides that, board rubbers are against the Geneva convention, man.
|
|
|
Post by eric on Dec 28, 2007 18:55:48 GMT 1
I don't know if ships ever deliberately made a smoke screen, cept in the movies (shortly before they open the sea cocks ). However, yes. Increase the air too much and you get white smoke. Too little air makes black smoke. I thought you were a roughty toughty Sgt Major, not a bleedin poof There are several classic examples of british warships laying down smoke screens, one is HMS Gloworm, a destroyer under attack from Hipper off Norway, she layed the smoke screen, then tried to torpedo hipper through the smoke screen, got badly hit by Hipper, then turnrd and rammed her, she then turned over and sank. There are photos that were taken from Hipper clearly showing the one-sided fight. The Germans were impressed by their courage and stopped to rescue as many as they could. Another example was a british cruiser force under attack from Italian battleships and cruisers in the Med, they layed a long smoke screen then darted in and out of the cover firing at their huge adversaries, scoring many hits and compleatly demoralising them. The Italiands turned and withdrew when they could have flattened the whole force, sunk the convoy they were protecting which would have ended Malta's fight and swung the whole war in the med. All thanks to a little exra oil squirted into the boilers!!!
|
|
|
Post by Mark on Dec 29, 2007 9:11:42 GMT 1
Thanks Eric, you learn something new every day
|
|
|
Post by rem2007 on Dec 29, 2007 23:53:55 GMT 1
Back home in Canada, we used smoke to signal everyone when tea was ready!......no really on the DDE steamers I sailed on when we made smoke, it was some officer type burning his dinner on one of the main stops...oh I'm cracking me up. Anyway, there are several reasons and ways to make smoke and Eric's theory is the most relevent.....tea's ready I can see the smoke from here, and that doesn't mean she is a poor cook.
|
|