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What is a Turboprop Engines?
Turbo-propeller engines are the power plant that uses a gas turbine to drive an air compressor, which provides compressed air to a propelling nozzle. The fuel used by a turbo-prop engine may be diesel (or similar), jet fuel, or aviation fuel. The key difference between the turboprop and the pure propeller aircraft is that the propeller itself has been replaced with a powered turbine. The turbine drives an air compressor, which provides pressurized air to the engines.
There are many different types of turboprop engines including the Allison T56-A-700, Pratt & Whitney JT8D-9, and Rolls Royce RB211.
Turboprops in the Aviation Industry
The turbo-propeller engines are a modern form of gas turbine that resembles an enlarged, two-bladed version of the conventional propeller engines found on most aircraft. It is particularly suited to small turboprop airliners and helicopters.
What is a Jet propulsion System?
Jet propulsion is based on newton’s second law and third law of motion. Newton’s second law states that the rate of change of momentum in any direction is proportional to the force acting in that direction. Newton’s third law of motion states that for every action there is an equal and opposite reaction. The types of jet engines are explained below.
How do Turbo-propeller engines Works?
These are also called turboprop engines. It differs from the turbo-jet in that, it uses a propeller to increase the mass flow of air. In this type, the turbine drives the compressor and propeller.
Air from the atmosphere is taken into the compressor through a diffuser. In the diffuser, the air is slowed down and compressed. The compressed air from the compressor enters the combustion chamber where the fuel is sprayed. The fuel-air mixture is burnt and thus heat is supplied at constant pressure. The combustion products are then expanded partially in the turbine. The combustion products are then expanded partially in the turbine.
The exhaust gases from the turbine are then expanded in the exit nozzle. In the nozzle pressure energy is converted into kinetic energy. Thus the gases emerge from the unit at a very high velocity. This increased velocity produces a reaction or thrust in the opposite direction. The total thrust produced is the sum of the thrusts produced by the nozzle and the propeller. This total thrust propels the aircraft.
The angular velocity of the shaft is very high. The propeller cannot run at a higher angular velocity. Therefore, a reduction gearbox is provided before the power is transmitted to the propeller. In some cases, two turbines are used to drive the compressor and propeller separately.
Turboprop Engine Types
There are two basic types of turboprop engines: the axial flow type and the centrifugal-flow type. Axial-flow turboprops are the oldest type of turboprop engine. These engines use a single shaft to drive both the compressor and the turbine. Centrifugal-flow turboprop engines are newer than axial-flow turboprop engines. They use two separate shafts – one to drive the compressor and the other to drive the turbine.
Turboprop Engine Performance
The performance of turboprop engines varies depending on the size of the plane. Smaller turboprop engines tend to produce less thrust per horsepower (thrust/hp) than larger ones. That’s because the smaller engines don’t need to generate as much thrust to lift the same weight. Larger turboprop engines, however, can produce higher thrust per hp.
Turboprop Engine Fuel Efficiency
Turboprop fuel efficiency tends to vary based on the size of the engine. Smaller turboprops tend to be more fuel efficient than larger ones. That makes sense because the smaller engines don’t need to generate as much force to lift the same weight as larger engines do.
Turboprop Engine Noise Levels
Noise levels tend to increase as the size of the turboprop engine increases. That’s because the bigger engines require more powerful fans to move enough air over the turbines. As a result, noise levels tend to increase as turboprop engines get larger.
Advantages of turbo-propeller engines
· Low specific weight and less frontal area.
· Simple in construction.
· Lesser vibration and noise. Easy maintenance.
· High power for take-off and climb of the propeller.
· High propulsive efficiency at speeds below 800 km/hr.
Latest Developments in Turboprop Engines
Turboprop engines have been around since the 1930s, but they were not widely used until the 1970s. Since then, they have become increasingly popular due to their high efficiency and low emissions. In fact, turboprops are now the preferred engine type for many airlines.
1. General Electric CF34-10A
The GE CF34-10A is the first production turbofan engine designed specifically for use in commercial aviation. It was developed in the early 1980s and is still being produced today. The CF34-10A produces approximately 50% more thrust than its closest competitor, the Pratt & Whitney JT8D.
2. Rolls Royce BR710
The Rolls Royce BR710 is a twin-spool turbofan engine that powers the Boeing 777X aircraft. It is the largest turbofan engine ever built and is capable of producing over 100,000 pounds of thrust. It is also able to produce more thrust per pound than any other current jet engine.
3. Airbus A330neo
The Airbus A330neo is the newest generation of the A330 family of widebody airliners. It features a number of improvements including increased fuel efficiency and lower operating costs. The A330neo is powered by two Rolls Royce Trent XWB engines.
4. Boeing 737 MAX 8
The Boeing 737 MAX 8 is the latest version of the Boeing 737 series of narrow-body jets. It is the world’s fastest-selling airliner, having surpassed 200 orders in just four months. The 737 MAX 8 is powered by two CFM International LEAP-1B engines.
5. Bombardier CSeries
The Bombardier CSeries is a regional jet manufactured by Bombardier Aerospace. It is the first Canadian-designed and built passenger airliner. The CSeries is powered by two CFMI Leap 1C engines.
6. Embraer E190
The Embraer E190 is a regional jet manufactured at the Embraer factory in São José dos Campos, Brazil. It is the only twinjet certified to operate out of airports with runways less than 5,000 feet long. The E190 is powered by two CFMBuilde 1B engines.
7. General Electric (GE) T700-JM Engine
The GE T700-JM engine was first introduced in 2012. It is a four-stroke, single-spool turbofan engine that produces about 6,000 pounds of thrust at takeoff. The engine has a maximum cruise speed of Mach 0.85 and a range of 1,500 nautical miles. The engine weighs only 9,800 lbs and has a dry weight of 8,200 lbs. The engine uses a single fan blade design and features a variable pitch nozzle. The engine has a fuel consumption rate of 2.9 gallons per hour and emits less than 10 grams of NOx per hour.
8. Pratt & Whitney Canada PT6A-135B Engine
This engine was developed in 2014 and is manufactured by Pratt & Whitney Canada. It is a six-stage axial compressor, two-stage turbine, and a three-stage fan. The engine has a thrust rating of 4,600 lbs and a maximum cruise speed of 0.8 Mach. The engine has a specific fuel consumption rate of 5.0 g/kWh and emits less than 20 grams of NOx per kilowatt hour.
9. Rolls Royce Trent 1000 Engine
Rolls Royce released its latest version of the Trent 1000 engine in 2016. The engine is a four-stroke turbofan engine that is capable of producing 11,000 pounds of thrust. The engine has a max cruise speed of Mach 0,95 and a range of 1.5 million nautical miles. The Trent 1000 engine weighs approximately 15,000 lbs and has a dry mass of 12,000 lbs. The engine consumes 2.8 gallons of fuel per hour and emits less than 30 grams of NOx per horsepower hour.
10. CFM International LEAP Engine
CFM International released its newest version of the Leap engine in 2017. The engine is a twin-fan, axial flow engine that is capable of generating 14,000 pounds of thrust and has a max cruise speed of Mach 0.83. The engine has a range of 1,300 nautical miles and weighs about 13,000 lbs. The Leap engine has a specific fuel usage rate of 5.0g/kW and emits less than 50 grams of NOx per kW hour.
11. Honeywell HTF7100 Engine
Honeywell released its newest version of its HTF7100 engine in 2018. The engine is a multi-fuel, turbojet engine that is capable of delivering 17,000 pounds of thrust with a max cruise speed of 0.75 Mach. The engine has an operating temperature range of -40°C to +50°C and a range of 1 million nautical miles. It weighs approximately 18,000 lbs and has an empty weight of 16,000 lbs. The HTF7100 engine consumes 2.5 gallons of fuel per hour, emits less than 100 grams of NOx per HP hour, and has a specific fuel consumption of 4.0 g/kW.
12. Rolls Royce RB211 Engine
In 2019, Rolls Royce released its newest version of the RB211 engine. This engine is a four-cycle, axial flow engine and is capable of producing 19,000 pounds of thrust, with a max cruise speed of 0.82 Mach. The engine has the capability of flying at altitudes of up to 60,000 feet. The engine has a dry weight of 22,000 lbs and a total weight of 24,000 lbs. The RB211 engine has a specific fuel use rate of 4.0 g / kW and emits less than 40 grams of NOx per kW hour.
Ram-jet engine
A ram-jet is the simplest of all propulsive devices. Compressor and turbine are not required for ram-jet units. It consists of three main components namely a diffuser system, combustion chamber, and exhaust nozzle.
Turbojets are the fastest aircraft ever built. Their speed is achieved by using afterburners, which burn fuel in oxygen-rich air to create thrust. Turbofans use the same principle, but instead of burning fuel in oxygen-rich gas, they burn fuel in the air. The advantage of turbofan engines is that they produce less noise than turbojets.
The first turbofan engine was designed in the 1950s. Since then, many different types of turbofans have been developed. Turbojets were invented in the 1930s, but their design was not perfected until the 1960s. Today, both turbofans and turbojets are being used in commercial and military aircraft.
How do Ramjet Engines Works?
The diffuser consists of two parts namely a supersonic diffuser and a subsonic diffuser. The atmospheric air enters the unit with supersonic velocity and is slowed down to the sonic velocity in the supersonic diffuser. This produces shock waves and increases pressure. Then the air passes through the subsonic diffuser and its velocity further reduces to a subsonic value. Due to this, the pressure of air increases to ignition pressure. Thus, the compression of air to the ignition pressure takes place only by the ram effect in the diffuser. Then the high-pressure air enters the combustion chamber.
Fuel is injected into the combustion chamber and the air-fuel mixture is burnt. The hot products of combustion are then expanded in the exit nozzle. In the nozzle pressure energy is converted into kinetic energy. This increased velocity of exhaust gases produces an opposite thrust. The aircraft is propelled by this thrust. The ram-jet operates at a very high speed.
Advantages of Ram-Jet Engines
· No moving parts.
· Lightweight when compared with the turbo-jet engine.
· More thrust than a turbo-jet
· Unlimited flight speed.
Comparison of Turboprop vs Turbo-Jet Engines
Turboprop engines are similar to turbojets in many ways. Both types of engines are powered by turbine blades spinning at high speeds. Turboprops use propellers instead of jet nozzles, though. And both types of engines have a compressor section that compresses air before combustion takes place.
1. Turboprop Engines
Turboprop engines are the most commonly used engine type for commercial aircraft. The turboprop engine was invented in the 1930s and is still widely used today. Turboprops have two counter-rotating propellers mounted at the front of the engine. These propellers create thrust by spinning blades around the shaft. The engine is connected to the wings via a drive train. This means that the power generated by the engine is transferred to the plane via a transmission system.
2. Turbo-Jet Engines
Jet engines were first developed in the 1940s and 1950s. A jet engine works similarly to a turboprop engine except that instead of using propellers, they use a compressor to compress air and then inject it into a combustion chamber where fuel is added. Once ignited, the mixture expands rapidly and pushes the turbine forward. This causes the fan blade to rotate and produce thrust.
3. Advantages of Turboprops
The advantages of turboprop engines over jet engines are that they are quieter, cheaper to manufacture, and easier to maintain. Turboprop engines are less expensive than jet engines and require less maintenance. This is due to the fact that turboprops do not need to be serviced as often as jets. Another advantage of turboprops is that they are much lighter than jet engines. This makes them easier to transport and handle.
4. Disadvantages of Turboprop Engined Aircraft
One disadvantage of turboprop engines is that they are slower than jet engines. This is because turboprops only generate half the amount of thrust as their jet counterparts. However, this does not mean that they cannot fly fast. In fact, some planes use turboprop engines to achieve high speeds.
5. Advantages of turbojet Engines
Jet Engines are faster than turboprops and are therefore able to travel farther distances. Also, jet engines are much louder than turboprops. This is mainly due to the fact that jet engines operate at higher altitudes. Because of these advantages, jet engines are preferred for commercial flights.
6. Disadvantages of Turbojet Engines
Jet engines are heavier than turboprops, making them harder to maneuver. Also, jet engines require more maintenance than turboprops because they are more complex.