Salient Features Of Scramjet Engine And Its Applications For Hypersonic Vehicles

 

Salient Features Of Scramjet Engine And Its Applications For Hypersonic Vehicles

        The scramejet uses a slightly modified Brayton Cycle to produce power, similar to that used for both the classical ramjet and turbine engine. Where Air is compressed and the  fuel injected, mixed and burned to increase the air, the combustion products are Temperature and Pressure then these combustion products are expanded.

For Turbojet engine Air is mechanically compressed by combustor using a turbine. In principle the ramjet and scramjet works the same. Where the forward motion of the vehicle compresses the air then the Fuel injected into the compressed air and burned. Results the high pressure combustion products expand through the Nozzle. Elevating the surface pressure and moving the vehicle forward.

 

SCRAMJET

• The wall of Ramjet will tend to fail at the higher temperature around 2500k,
• Like Turbojets, Conventional ramjets are also limited by material problem at high Mach Number.
• When the temperature of the air entering the combustor is too high, during which the fuel injected, it will be decomposed by the higher temperature instead been burned (Fuel will absorb rather than producing energy).
• The engine will become a Drag producing machine instead for a Thrust producing device.
• When the air flow is decrease by the scramjet the relative velocity and kinetic energy both decrease, during that energy required that any missing kinetic energy will reappear as internal energy.
• When the flight Mach number exceeds about 6 led to decelerate the flow to subsonic speeds.

Advantage

• No moving parts easies to manufacture.

• Has less weight and simple design.

• Does not have to carry oxygen tank.

• High seed could be achieved easier, so cheaper access to outer space in the future.

Disadvantage

• Scramjet cannot produce efficient thrust unless achieves high speed, around Mach 5.

• Testing a Scramjet design requires a expensive equipments (hypersonic test chambers and launching vehicles).

• Lack of strength.

 

 

 

 

Ramjet Engines in Fighter Aircraft

            Ramjet Engines is a type of Combustion Engine, comes under the category of Air breathing engine. It is the simplest of all the air breathing engines. It consists of a Diffuser, Combustion chamber and a Nozzle, and ramjets do not need any moving parts such as compressors and consequently no turbine as well.

Major Assemble of Ramjet Engines

• Diffuser

• Combustion Chamber

• Nozzle

Ramjet Engines mechanism are less complicated jet engine for producing thrust in flying vehicle.

Ramjet Engines are most efficient when operated at supersonic speeds.

All the compression is occurs in the intake diffuser section producing rise in the static pressure.

When the air decelerated from a high mach number to a low subsonic mach number, it results in substantial increase in pressure and temperature so the ramjet does not need Compressor and Turbine.

 

Working

Ramjet produces power by increasing the momentum of the moving fluid by induction of energy by combustion of fuel, so the momentum of the exhaust jet greater and exceed that of the incoming air on continuous cycle.

Where the Fuel is burned the high pressure air and the mixture is then expanded to ambient static pressure through a Nozzle System.

High pressure gas expanded through the Nozzle by converting the low subsonic flow in the combustion chamber into a supersonic jet.

The combine mixture of air and fuel (supersonic jet) exhausted through the C-D Nozzle.

Working cycle of Ramjet Engines

source:NPTL

 

Ramjet Engines

            Ramjet Engines is a type of Combustion Engine, comes under the category of Air breathing engine. It is the simplest of all the air breathing engines. It consists of a Diffuser, Combustion chamber and a Nozzle, and ramjets do not need any moving parts such as compressors and consequently no turbine as well.

Major Assemble of Ramjet Engines

• Diffuser

• Combustion Chamber

• Nozzle

Ramjet Engines mechanism are less complicated jet engine for producing thrust in flying vehicle.

Ramjet Engines are most efficient when operated at supersonic speeds.

All the compression is occurs in the intake diffuser section producing rise in the static pressure.

When the air decelerated from a high mach number to a low subsonic mach number, it results in substantial increase in pressure and temperature so the ramjet does not need Compressor and Turbine.

 

Working

Ramjet produces power by increasing the momentum of the moving fluid by induction of energy by combustion of fuel, so the momentum of the exhaust jet greater and exceed that of the incoming air on continuous cycle.

Where the Fuel is burned the high pressure air and the mixture is then expanded to ambient static pressure through a Nozzle System.

High pressure gas expanded through the Nozzle by converting the low subsonic flow in the combustion chamber into a supersonic jet.

The combine mixture of air and fuel (supersonic jet) exhausted through the C-D Nozzle.

Working cycle of Ramjet Engines

source:NPTL

Control Surface of airplane

Control Surface of airplane

              Control surface of Aircraft is an aerodynamic device mean by which pilot stabilize aircraft and controls the direction and altitude of an aircraft on flight. Control surface is a movable surface which is lighter in construction has light  spar rod at the front edges to provide strength and rigidity, the spar connect the ribs and covered by the thin skinned sheet. The tabs are attached to the trailing edge of the control surface additional device will be attached based of purpose the control surface is used for transmission of tab loads to the surface.

Sheet Materials used in Control Surface

1. Metal structure                   -        Covered with metal skin
2. Composite Structure          -        Covered with fabric
3. Wooden Structure              -        Covered with Plywood or fabric

Drilling

The hole on the surface made using drain holes to prevent water  trapped inside the structure , which causes the control surface to be thrown out of balance

Jointing

Process involved in jointing the components includes fasteners like adhesive and bonding agents.

Flight Control Surface are sub branched into

• Primary Control Surface
• Secondary Control Surface

Primary Control Surfaceis designed to provide adequate response to controlling device giving a natural feel.

At low speed control will be smooth and sluggish

At high speed control will become increasingly firm

Responding to speed

At low speed the aircraft respond slow to control applied

At high speed the aircraft respond more rapid (faster) to control applied

Primary Control Surface includes:

Ailerons - (ROLL) Control motion along longitudinal axis.

Elevator - (PITCH) Control rotational motion along lateral axis.

Rudder  - (YAW) Control motion along Vertical axis.

Secondary Control Surface are use to improve the aircraft performance characteristics and to release the excessive control loads applied.

Secondary Control Surface includes:

Wing flaps - Used to increase the Lift and Drag increase while Take off.

Slats- Located on the leading edge of the wings. Creates enough lift at high Angle of attack.

Slots- Span wise gap present at each wing allowing air to flow between the wings, which creates lift thus reduces stall.

Trimtabs - Connect trailing edge to large Control Surface, Used to Stabilize the aircraft.

Balancetabs - Control loads on the control surface is significantly reduced, makes aircraft easy to fly.

Anti-Balancetabs - Maintain the stability in the desire position.

Servo tabs- Small Hinged device to assist the movement of the control surface.

The Combination of this Control Surface of Aircraft helps the pilot in controlling and stressing the aircraft during flight .

For more Related Topic and Information on Aircraft Technology - CLICK HERE

 

TYPES OF LANDING GEAR

TYPES OF LANDING GEAR

        The basics of the landing gear was explained in the before posts.(https://sabaeroline.blogspot.com/2020/06/aircraft-landing-gear.html) Landing gear types would clearly explain in the present post. As pilot tries, Not Every Aircraft landing is perfect due to Bad weather conditions, short landing etc., Landing gear play important role at time of rough landing, handles the aircraft smoothly and safely landing without breaking or collapsing the aircraft into pieces. 

TYPES OF LANDING GEAR

There are many types of Landing gear. The types of landing gear used in the aircraft depend on two things design of the aircraft (like military, civil purpose) and its intended use (like Cargo, commercial).There are three main types of landing gears used.

Tail wheel Landing Gear

Tail wheel Landing Gear is also known as Conventional or traditional type landing gear because this was milestone for majority of the aviation history, used in the other legendary fighters of WW2. The main gear are located forward to centre of gravity of flight, which makes the tail to get support  from the third wheel assembled in the tail of the aircraft. In some aircraft skid replaces the third wheel which helps slow the aircraft while landing and provide direction stability in earlier aircraft.

By raising the angle of fuse large when fitted with conventional gear allows to fix long propeller in front of engine for older aircraft, It also provide increase ground clearance of the forward fuse large with is also a advantage in using Conventional Landing Gear.

Directional stability is controlled by different breaking system until the aircraft speed comes under the control of the Rudder. Steerable tail wheel connected to the rudder and rudder pedals by cables. For smooth and easy landing springs fixed for damping.

Tandem landing gear

Most of the aircraft using tandem landing gear are military planes and spy planes. This type of landing gear has a main gear andtail gear aligned on the longitudinal axis of the aircraft. 

The main advantage of Tandem landing gear design reduces drag when deployed they are retractable.

Tricycle-type landing gear

The most common type landing arrangement used in modern aircraft is the Tricycle-type landing gear consist of a nose gear and main gear. Larger and small aircraft today used this gear arrangement.

Benefits

• Allows more forceful application of the breaks without noise created over when Breaking which increases high landing speed.
• Provides better visibility from the flight while landing and ground maneuvering.
• Weights are equally spread over large area and are equally distributer each Gears provide a better safety margin.
• Aircraft centre of gravity lies forward of the main gear, force act on CG point makes the aircraft moving forward avoiding looping which prevents groung-looping.

Landing Gear Design

Depend on the Aircraft usage and operation the landing been designed either Fixed Gear (immovable) Retractable Gear(movable).

For more Related Topic and Information on Aircraft Technology - CLICK HERE

 

Fuel System

          

Fuel system in aircraft is designed to deliver uniform flow of clean fuel from the tank to the propulsion system of the aircraft without any interruption to power system during continuous flight at high altitude, during all approved maneuvers.  Each fuel tank is equipped with internal fuel pumps, valves and plumbing to feed fuel to the engine to produce thrust.

          Fuel system consist multiple fuel tanks located in the wing or fuselage base on aircraft design, intended use and as well as age aircraft determine which fuel tank to be installed. The tanks are made of non corrosive materials that are non reactive aviation fuel. Aluminium alloy are more commonly used in modern aircraft fuel tank of its light weight and corrosive resistant, Synthetic rubber coated type fuel cells are also used.

                     

        In high wing aircraft there is no need of any pumps to feed the fuel. Gravity propels the fuel from tank to the engine. In lighter Aircraft and low wing aircraft fuel tanks are located inside the wing. Have filler opening at the top of the wing through which fuel can be filled and drains in the bottom by which any moisture can be removed, to drain fuel sample for inspection. Electrical Pump been used to pass the fuel from the tank to the Carburetor, and pressure gauge will be attached to the pump show weather the pumps are working properly. Vent (Duct) placed to equalise the internal pressure. Fuel selector valveare used to avoid imbalance fuel flow and allow to choose from which tank the fuel should flow to the Engine. Before the fuel enters the engine fuel will passes through the Strainer where the water and other contaminated particles are removed to avoid improper quality fuel to flow leads to Failure of Fuel system.

Common fuel system issues  

   

Pressurization of Fuel Tank

During maneuvering, rolling and yawing motion of the aircraft Centrifugal force will be created due to which pressure acts on fuel tank. During design fuel tank will undergo analyse applying different pressure load at pitch yaw roll motion to calculate natural frequency and resonance which may leads to the vibration of the fuel Tank which are more effective.

Failure of Fuel pump

Pumps have automatic bypass valves. If one valve fails other pumps will continue normal flow to pass the failed pump. A failure pump can causes several of problems. Fuel pump is a non serviceable part means it needs to be replaced.

Imbalance fuel flow

On flight the usage and the movement of the fuel in the fuel tank keeps changing which would change center of gravity of the aircraft. Many air craft have pump to pass the fuel from one tank in the wing to another to balance level equally on both as not to get heavier on onside. This happens because of unequal usage of fuel by the engines. Imbalance fuel flow affects the stability of the aircraft during flight.

For more Related Topic and Information on Aircraft Technology - CLICK HERE

 

RADAR SYSTEM

RADAR SYSTEM

          Clear-cut of the word RADAR is Radio Detection and Ranging which operates under the principle similar to sound-wave reflection. In aircraft RADAR systems are placed at the front inside the nose the aircraft which would be the perfect place to transmit and receive signal without any interruption.

         RADAR systems have a transmitter which produces an electromagnetic signal which is transmitted and radiated into the space by an antenna. Electromagnetic signal hit and sticks the object and get reflect back and received by the receiver. Received echo Signal from the antenna is processed by a computer and display on screen inside the cockpit displayed to the pilot. Where it is processed to detect the location and distance of the object on the earth surface accurate from the point where the Radar is fixed by calculating the time taken radar signal to stick the object and reflect back. As the aircraft fly at high altitude target location is measured in degrees and angles.

Types of RADAR used in Aircraft

• Pulse Doppler RADAR transmits high pulse repetition frequency utilizes the Doppler frequency shift of the echo signal to reject and detect moving aircraft.

Doppler shift are calculated by transmitted high pulse and the received echo signals are mixed in a detector.

• Moving Target Indicator RADAR transmits low pulse repetition frequency low pulse to avoid range cluster and the received echo signals are mixed in a detector where it differentiate echoes of a moving object from stationary object detect moving aircraft.
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Aircraft Black Box

Aircraft Black Box

         

            Black Box is an indestructible orange colored recording device placed in aircraft which would be the only evidence to establish why a plane crash or how the aircraft met with the accident. Aviation experts normally called Black boxes as electronic flight data recorders. Their main process is to record and keep tracking on-flight data information such as altitude (height from earth surface), stability of the aircraft and speed as well as pilot conversation took place in the cockpit. Multiple functions would be carried out on-flight with multiple devices all information will be easily transmitted to the black box. It is placed on the tail of the aircraft for safe precautions.

Black box are not black in color. It is bright orange in order it would be more easily visible in wreckage.

Black box design

For safety purpose and protect the secondary components that stores information its covered with in a thin layer aluminium and 1-inch layer of high-temperature insulation, and over that shielded in a corrosion-resistant titanium or stainless steel shell. Strengthens it to withstand shocks during flight crash or fall from high altitude and went deep inside the sea.

Two separate box in Black box

Clearly there are two black boxes present in an aircraft:

• Flight Data Recorder stores the information about flight control include direction, altitude and engine performance includes speed and turbulence etc.
• Cockpit voice Recorder record the background sound on the aircraft in cockpit cabin, engine and voice conversation between the crew and control station (ATC Air traffic control) to predict the performance of the aircraft before crash or accident.

If any airplane accident happens investigators immediately begin searching for the aircraft’s black boxes.