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jet engine wet start

Jet engine wet start

Jet engine wet start

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Jet engine wet start
Jet engine wet start

Jet engine

jet engine is a type of reaction engine discharging a fast-moving jet that generates thrust by jet propulsion. While this broad definition can include rocket, water jet, and hybrid propulsion, the term jet engine typically refers to an internal combustion airbreathing jet engine such as a turbojet, turbofan, ramjet, or pulse jet. In general, jet engines are internal combustion engines.

Airbreathing jet engines typically feature a rotating air compressor powered by a turbine, with the leftover power providing thrust through the propelling nozzle—this process is known as the Brayton thermodynamic cycle. Jet aircraft use such engines for long-distance travel.

Early jet aircraft used turbojet engines that were relatively inefficient for subsonic flight. Most modern subsonic jet aircraft use more complex high-bypass turbofan engines. They give higher speed and greater fuel efficiency than piston and propeller aeroengines over long distances. A few air-breathing engines made for high speed applications (ramjets and scramjets) use the ram effect of the vehicle’s speed instead of a mechanical compressor.

The thrust of a typical jetliner engine went from 5,000 lbf (22,000 N) (de Havilland Ghost turbojet) in the 1950s to 115,000 lbf (510,000 N) (General Electric GE90 turbofan) in the 1990s, and their reliability went from 40 in-flight shutdowns per 100,000 engine flight hours to less than 1 per 100,000 in the late 1990s. This, combined with greatly decreased fuel consumption, permitted routine transatlantic flight by twin- engined airliners by the turn of the century, where previously a similar journey would have required multiple fuel stops.

Water jet

A water jet, or pump-jet, is a marine propulsion system that utilizes a jet of water. The mechanical arrangement may be a ducted propeller with nozzle, or a centrifugal compressor and nozzle. The pump-jet must be driven by a separate engine such as a Diesel or gas turbine.

Type Description Advantages Disadvantages
Water jet For propelling water rockets and jetboats; squirts water out the back through a nozzle In boats, can run in shallow water, high acceleration, no risk of engine overload (unlike propellers), less noise and vibration, highly maneuverable at all boat speeds, high speed efficiency, less vulnerable to damage from debris, very reliable, more load flexibility, less harmful to wildlife Can be less efficient than a propeller at low speed, more expensive, higher weight in boat due to entrained water, will not perform well if boat is heavier than the jet is sized for

How to Start a Jet Engine

Whether you are starting a sleek and stealthy F-22 Raptor or a 787 Dreamliner, the first main step to getting in the air is the same: You’ve got to get your engines going. But this isn’t a car. It’s not as easy as just turning the ignition. Nor is it some old-fashioned prop plane you can start up with your hands. A modern day jet engine is a little more complicated, and the key to getting started is a bit circular; you’ve got to have an engine running already.

You can’t understand how a jet engine starts if you don’t first understand what it’s doing when it’s going at full blast. As Bold Method concisely explains, the process is fairly simple in the abstract. Rotating fans at the front of the engine suck air in and compress it over and over to prepare it for a chamber near the back of the engine. In this chamber, fuel is injected and burned, creating a reaction which shoots air out the back of the engine, but also pushes past fans that turn a shaft that powers the fan up front. It’s a circular system, so turning the thing on in the first place puts you in a chicken-and-egg scenario.

The solution is to bring another engine into the equation. Some passenger jets have smaller, built-in engines that can be started by more conventional means. These can then provide enough pressurized air to push a larger engine up to the minimum speed at which it can keep itself going. Otherwise, you can get the same effect with an external cart that can provide the same kick of air to get things started.

From there, it’s as simple as using one engine to start the other, cranking the throttle to full, and then cruising into the air. OK, maybe it’s a little more complicated than that, but you’ll never find out if you can’t start the engine.

Jet engine wet start
Jet engine wet start

What Is Wet Starting A Jet Engine?

The term “wet-start” refers to a process at which the aircraft’s engines produce fuel while you hit it’s start switch so there is sufficient fuel in them. Due to a wet start, the tail of the plane ignites a flame long ago. An elaborate show meant to draw the pilot’s attention, it was done in that manner only.

What Causes Wet Start?

When the engine begins to smoke during the process of adding fuel to the combustion chamber, a wet start is possible. Fuel flooding occurs as a result of combustion when it is never lit. This, naturally, causes the ‘wet’ reaction. In order to start again, we need to get rid of this fuel.

 

What Should The Pilot Do After An Engine Wet Start?

By windmilling the engine, the plane captain can avoid overflying the plane after a wet start. It is then common for a second start attempt to be made. It is not possible to light off an engine within 20 seconds to start a wet car.

 

What Is A Hot Start Jet Engine?

You may experience what’s known as a “hot start” if the operating temperature exceeds the standard manufacturer limit. As the reason why a hot start may occur is because there is insufficient airflow through the compressor, improper fuel scheduling, or slow engine acceleration.

How much damage does a “wet start” do to a jet fighter?

A wet start does no harm to the engine. A wet start occurs when the engine fails to light up in a certain period of time when fuel is introduced into the combustion chamber. The indication of a wet start to the pilot is a positive rise and stabilisation of high pressure compressor with no rise in engine exhaust temperature.

When this happens, the pilot shuts off the fuel to the engine and selects the ignitors off. Because fuel was introduced for combustion and it never was lit up, fuel flooding occurs (hence the term ‘wet’) . This fuel needs to be removed before a second start is attempted. How this is achieved is by keeping high pressure compressor running with fuel and the igniters off. This ensures the fuel in the chamber is returned back into the fuel tanks or in certain engines evaporated out into the atmosphere.

The only danger of a wet start is a rare possibility of fuel igniting in the combustion chamber. This is called torching. The whole point of removing the excess fuel in the the chamber is to prevent this from happening.

 

Jet engine wet start
Jet engine wet start

What Is Aircraft Wet Leasing? Why Is It Important?

‘Wet leasing airline’ was the buzzword of 2018, referring to incredibly flexible airlines that can operate anywhere, at any time and for anyone. In fact, thanks to them and their fleets, air travel has become more convenient and hassle-free than ever before.

But what exactly is wet leasing, and how does it work?

What is Wet Leasing?

Imagine that you are leasing a car. For your money you get a vehicle with four wheels and a steering wheel. A wet-lease however, is more akin to a taxi. Your car comes with a driver, fuel and the registration to operate on the roads.

Several companies in the aviation space offer not just aircraft for lease, but provide their own pilots, flight crew, maintenance, and even airline certificates. This is called wet leasing.

Why is Wet-Leasing important?

Wet-lease is very important to the industry, as airlines often turn to wet-leasing to ensure smooth operations during peak traffic seasons, to cope with scheduled or unexpected maintenance checks, or to test new routes. Furthermore, a wet-leased aircraft may be used to fly services into countries where the lessee is not able to operate.

For example, the flag carrier of Egypt, Egypt Air, is not allowed to fly to Israel. As such, a new ‘airline’, Air Sinai, wet-leases Egypt Air flights to travel between the two countries.

Generally, the aircraft can be deployed at very short notice, sometimes as little as three hours, to cover short or medium term transportation needs. This means that primarily wet-lease aircraft are hired by airlines and governments. As we saw with Norwegian, several wet-lease aircraft were hired to cover their fleet capacity when their 787 Dreamliner fleet was grounded.

The flight is operated under the customer airline flight numbers and is billed by the wet-lease airline in flight hours, as opposed to tickets to passengers. Although wet-lease is the core business, many of these airlines also offer their fleets for high-quality charter flights.

 

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