What is water methanol injection. why and when is it used? What aircraft utilize these systems?

Question

What is water methanol injection. why and when is it used? What aircraft utilize these systems?

Answer 1

water methanol injection is used in jet engine at higher altitude.

this is the process in which water and methanol( it is used to lower the freezing point of water and act as additional fuel) is injected in compressor section or just before burner to increase the mass of air entering inside the cobustion chamber to produce more thrust at lower rpm in greater height because at greter height the air get thinner in density so we need higher rpm for making the proper amount of air to enter making fuel consumption more.

this is why water methanol injection is used and it is more often used in proppelller aircraft

Answer 2

Max and brit are both correct. The increased density that Max refers to results in an increased mass flow rate for a limited time. A jet engine creates thrust by mass flow and exhaust velocity - (momentum). It's like throwing bowling balls off the back of a wagon while you are standing on the wagon. The more bowling balls that you throw, the faster you will move. Water injection is just a simple way to increase the mass flow rate without burning more fuel. As long as you don't add so much that you flame out, you will get more thrust while you're adding it. I think it makes a mess out of the combustor and turbine components, but KC135s were under powered and really needed a little extra oomph to get off the runway when they were fully loaded.

ADDED: I think the B52s that used these engines were the "G" models. The "H" models had new turbofans and were actually overpowered.

Answer 3

Water metanol injection is a system which improves the volumetric efficiency of an engine as it is directed into the inlet manifold in a recip. engine or just upstream of the combustion chambers in a jet engine. This fluid lowers the temperature of the induced gas stream allowing a denser charge to be burnt within the engine. A denser charge equals increased horsepower.  Water metanol injection has been used on the Rolls Royce Dart Aero Engine. (F 28 ). It allows take offs in very hot dry conditions which may be marginal without the use of this system in consideration of all up weight and runway length.

Answer 4

Back in the day (60's and 70's), The USAF KC-135A used water injection for additional thrust for take off, 120 seconds is all it had capacity for. The B-52,which had the same engines, but twice as many, only had 60 seconds of injection. This is now obsolete due to better technology and higher thrust engines. The water storage tanks are now used for fuel.

Answer 5

WATER INJECTION SYSTEM FOR RECIPROCATING ENGINES

There are a few of these now being used, but the water injection system enables more power to be obtained from the engine at takeoff than is possible without water injection. The carburetor (operating at high-power settings) delivers more fuel to the engine than it actually needs. A leaner mixture would produce more power; however, the additional fuel is necessary to prevent overheating and detonation. With the injection of the antidetonant fluid, the mixture can be leaned out to that which produces maximum power, and the vaporization of the water-alcohol mixture then provides the cooling formerly supplied by the excess fuel.

Operating on this best power mixture, the engine develops more power even though the manifold pressure and r.p.m. settings remain unchanged. In addition though, the manifold pressure can be increased to a point which would cause detonation without injection of the water-alcohol mixture. Thus, the increase in power with the autidetonant injection is two-fold: the engine can be operated on the best power mixture, and the maximum manifold pressure can be increased.

WATER INJECTION RE-SET SYSTEM

On warm days, thrust is reduced because of the decrease in air density. This can be compensated for by injecting water at the compressor inlet or diffuser case. This lowers the air temperature and increases air density. A microswitch in the fuel control is actuated by the control shaft when the power lever is moved toward the maximum power position.

A water injection speed re-set servo, re-sets the speed adjustment to a higher value during water injection. Without thìs adjustment, the fuel control would decrease r.p.m. so that no additional thrust would be realized during water injection.

The servo is a shuttle valve which is acted upon by water pressure during water injection. Movement of the servo displaces a lever on the cam-operated lever linkage to the speed governor speeder spring, increasing the force of the speeder spring and increasing the set speed. Because the resulting r.p.m. will usually be higher while water is flowing, increased thrust during water injection is ensured.

If the water injection system is not armed in the cockpit or if there is no water available, nothing happens when the water injection switch in the fuel control unit is actuated. When water is available, a portion of it is directed to the water injection speed re-set servo.

WATER OR COOLANT INJECTION

The sensitivity of turbine engines to compressor inlet temperature results in an appreciable loss of available thrust, or power in the case of a turboprop engine, on a hot day. It is sometimes necessary to augment the thrust output. Water injection is a means of increasing engine thrust. It reduces hot section temperatures, fuel flow can be increased and greater thrust thereby obtained.

Thrust increase is particularly desirable at takeoff when an aircraft engine is called upon for the greatest output of power, therefore the water injection system is designed to function only at high engine power.

The effect upon engine thrust depends upon the type of coolant used, the proportion of the ingredients, and the quantity of the coolant flow. For effective cooling, a liquid with a high heat of vaporization is required. Water, is the most desirable coolant. Alcohol is added occasionally in varying proportions, either to lower the freezing point of the coolant or to eliminate the need for separate enrichment of the fuel mixture, which might be necessary if only pure water were used. When alcohol is added, some small amount of additional thrust may be produced as the alcohol is burned. However, the efficiency of the combustion of the alcohol is usually quite low. The heating value of methyl or ethyl alcohol is only about half that of kerosene or gasoline. Most of the flow of the alcohol/air mixture will not pass through that part of the combustion zone where temperatures are high enough to support efficient combustion of the weak alcohol/air mixture.

Very few powerplants using water injection are in use today.

Answer 6

Max E got it and other answers were good too.

I used to work on the Convair 580 water bombers and they still use water meth for takeoff.

The methanol is for restoring the maximum engine temperatures as well as to prevent the leftover water from freezing at high altitudes.

I saw what happened once when someone accidentally put pure methanol into the water meth tanks.  About a ten foot flame out the exhaust pipe.

Answer 7

common-esp military use turbo/ram jet/prop afterburners: pump water methanol into exhaust after final turbine to increase thrust-used for takeoff, or short bursts of extra speed-very great weight penalty to carry around.  not used in other engine types except some competition piston engines as anti-knock fluid/powerboost/coolant-see Red Bull Air racers etc.

Answer 8

Max E deserve the ten points as his answer is true and correct. The aircraft who uses this were: HS-748, the Japanese modified YS-11. both engines are RR Dart (forgot the number.) I was still a component mechanic at this time and we have a tester for this water methanol control unit.

Answer 9

The what is and when has already been answered so I'm just gonna add a couple civilian aircraft that use AWI.  I fly the metroliner (sa-227)... I've got water/meth for takeoff when it's hot outside.  There's a 16 gallon tank in the nose that I can use for a max of 5 minutes.  Also, I know some of the fokker's used AWI.  I will say this, when using AWI it's amazing at how much torque increase there actually is.  You really notice it when you turn it off through a couple thousand feet and it feels like the plane's gonna fall out of the air.  It's a pretty neat system.

Answer 10

The big bombers (B29) and other craft used it during WWII. It was used at high altitude for more power and speed. The methanol was added to the water injection systems to prevent the water from freezing at high altitudes.