Why doen injecting water in 1)receprocating engines
2) jet engines
increase power?
2007-07-24 07:17:21 · 10 answers · asked by coolie 1 in Cars & Transportation ➔ Aircraft
Water injection simply cools the combustion chamber down. If thecombustion chamber gets to hot, the fuel/air mix will ignite before it reaches the spark plug. Water Injection solves this problem by cooling the walls of the chamber, This allows for a higher compression ratios. The actual fluid is not pure water but most of the time mixed with ethanol. Wthanol will act as an anti freeze and also like a boost.
2007-07-24 07:23:13 · answer #1 · answered by Charles 5 · 0⤊ 3⤋
On take off especially at an airport that is at a high altitude like Denver, the air is already thin so back in the day water was injected into the engine in front of the compressor stage. The water made the air condense, that is to make heavier, thus giving the engine more thrust. Here's an example. At about three thousand feet a fully loaded B-52 bomber would use approximately 12,000 gallons of water on take off. The B-52 has eight jet engines which would account for the ungodly amount of water and fuel it would consume on take off. With modern turbo fan engines that isn't necessary anymore but it is interesting how jet engine technology has progressed.
2007-07-24 17:14:37 · answer #2 · answered by rollmanjmg 4 · 0⤊ 0⤋
I know that some late war fighter aircraft in WW II had water injection available. According to the training films, it could only be used for about a minute at a time for extra power in combat situations. It's been a while since I saw the film and cannot directly quote the narration. I believe that the short durations in which it could be used was due to the fact it increased the engine compression and temperature to dangerous levels, and that's why was reserved for emergencies. The principal behind the increased power was the fact that the water volume was increased during ignition along with the fuel, to create steam. Just as a small measure of fuel expands during ignition creating power to move the piston, water with the fuel expands in to steam, greatly increasing the power expansion of the fuel.
2007-07-24 15:27:07 · answer #3 · answered by Derail 7 · 1⤊ 0⤋
Water injection not only prevents detonation, but it improves what is called "mass flow". This added mass increases the horsepower. (input to output, the same goes for jet engines) Most recent water injection systems use water methanol, a weak alcohol that prevents too much cooling by burning.
2007-07-24 19:57:59 · answer #4 · answered by mojonah 3 · 0⤊ 0⤋
Water injection on recip engines is known as Anti Detonation Injection (ADI).
Water injection itself does not increase power, but allows the engine to use a much higher manifold pressure (power) without the danger of detonation.
I can only speak of the Wright Turbo Compound engine - we could only use 54" MAP for a "dry" take off - but with ADI we could use 61" MAP. (I am relying on memory for those figures)
2007-07-24 19:29:59 · answer #5 · answered by skytrain18 3 · 2⤊ 0⤋
Water injection in a piston engine besides cooling things, also increases the compression pressure in the cylinder. Water will not compress like the air fuel mixture will in that situation, and so the compression pressure in the cylinder is higher at the compression stroke.
Compression pressure = horsepower.
2007-07-24 19:41:37 · answer #6 · answered by gromit801 7 · 0⤊ 0⤋
Some of the early military versions of the B 707 (C-135) were called "Water Wagons". Water was injected into the jet stream, which resulted in an increased thrust.
I do not know of any modern plane using that method.
2007-07-24 15:03:06 · answer #7 · answered by kg 2 · 1⤊ 1⤋
The water cools the charge air to allow it to become more dense in both Piston and Turbojet engines(Turbofans don't use it).
The more dense the air charge the more power from the engine. Think intercoolers on little rice rocket turbocharged cars. Same principle.
Turbofans would sling all the water into the bypass air and would do little to increase power since bypass air isn't combusted.
The short duration is strictly due to the inability to store enough water on board the aircraft. Piston or Turbojet.
Ret. USAF SNCO, Aircraft Maint.
2007-07-24 15:47:34 · answer #8 · answered by Anonymous · 0⤊ 2⤋
Skytrain18 is on track. The water solution was called 'Anti Detonation Injection. To understand the physics of it see, http://www.google.com.sg/search?hl=en&client=firefox-a&rls=org.mozilla:en-US:official&hs=2vB&sa=X&oi=spell&resnum=0&ct=result&cd=1&q=Anti+Injection+detonation+fluid&spell=1
I only experienced it on the C-118 which had the ADI tank in the tail.
2007-07-24 22:42:31 · answer #9 · answered by Caretaker 7 · 0⤊ 0⤋
Nothing like a cold drink of water on a hot summer day!
2007-07-24 21:08:34 · answer #10 · answered by Baron_von_Party 6 · 0⤊ 2⤋