shehbazi2001
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When we talk of thrust, we should talk of "nozzle" because it is the nozzle that generates the thrust. A jet engine without nozzle can be used for electric power generation as gas turbine powerplant or can be used to power the ships, tanks and helicopters.
Helicopters and electric powerplants use the shaft power instead of thrust and thus this category is also called turboshaft engines. Tanks seem to be in the same category, although I know only M-1 Abraham that uses gas turbine propulsion.
The equation of thrust of a nozzle is,
Thrust= mass flow rate of air/gas*(Exit Gas Velocity - Inlet Air Velocity)+(Exit Pressure - Inlet Pressure)*X-Sectional Area of Nozzle
The first component is the important one with room of improvement. We need both a higher mass flow rate of air with a large difference between the entry air and exit air/gas mixture. A higher mass flow rate of air means that size would always play a role when you want a higher thrust. This is the reason that the engines of Beoing 747 or Airbus A380 are enormous in dimensions.
The other factor is the difference of velocities. For this, I think there are two things. First a higher pressure ratio in the compressor. Nowadays a pressure ratio of 30:1 is norm. A higher pressure ratio shall obviously give better results.
Then is the combustion. A more energetic fuel than the normal aviation fuels can increase thrust just like in some automobiles and early jet aircrafts, special fuels were used to get more thrust and more power.
You can put more fuel to get a more rich air/fuel mixture but its not the trend these days. Jet engine air/fuel mixture is weak in the order of 70:1, meaning 1kg of fuel for each 70kg of air. Of course the use of afterburner changes all this. But todays research is to improve the understanding of turbulent combustion so that the fuel is "fully" burnt and there is no wastage and no smoke in exhaust. Here the understanding of "Turbulence" is itself a problem in advancement in this field.
we also have the pressure losses in a jet engine. An effort to minimise the pressure losses shall evidently result in higher thrust performance.
Other important parameter, related to combustion, is Turbine Entry Temperature (TET). This area depends on progress in materials. Nowadays, engines are using Single-Crystal materials in turbine blades as they endure higher temperatures.
Then is the thermal coating of turbine blades to save them from severe effects of higher temperatures. A better coating can result in better performance. Then is the turbine blade cooling. If you can come with a liquid or liquid metal that has excellent heat absorbing capabilities and can be used as a coolant, then too thats an improvement and we would be able to increase TET, thus increasing thrust.
Another area is backflow of air from high pressure area to low-pressure area because there is a "gap" between blade tip and casing of engine. This "gap" causes sort of leakage. Any breakthrough in this area shall improve the engine performance.
Coming back to where I started, the most important is nozzle design itself. Its not easy to get a good thrust from a nozzle at all altitudes. The thrust of a conventional nozzle varies with altitude because the back atmospheric pressure on nozzle changes with altitude. Some nozzles are optimised for a certain altitude whereas some are optimised for sea-level altitude.
Having said all this, any improvement in engine thrust is useless if it does not improve the thust/weight ratio. An engine should have at least 10:1 thust/weight ratio to be useful for aircraft because once fitted inside aircraft, the aircraft may get a thrust/weight ratio of hardly 1:1.
Before concluding this post, we must remember that really what matters is "Installed Thrust" and not the "stand-alone thrust". The thrust that we get from an engine on the test-rig is not the same when installed inside an aircraft. At the business end, we want that engine should perform the same way when installed inside the airframe.
Helicopters and electric powerplants use the shaft power instead of thrust and thus this category is also called turboshaft engines. Tanks seem to be in the same category, although I know only M-1 Abraham that uses gas turbine propulsion.
The equation of thrust of a nozzle is,
Thrust= mass flow rate of air/gas*(Exit Gas Velocity - Inlet Air Velocity)+(Exit Pressure - Inlet Pressure)*X-Sectional Area of Nozzle
The first component is the important one with room of improvement. We need both a higher mass flow rate of air with a large difference between the entry air and exit air/gas mixture. A higher mass flow rate of air means that size would always play a role when you want a higher thrust. This is the reason that the engines of Beoing 747 or Airbus A380 are enormous in dimensions.
The other factor is the difference of velocities. For this, I think there are two things. First a higher pressure ratio in the compressor. Nowadays a pressure ratio of 30:1 is norm. A higher pressure ratio shall obviously give better results.
Then is the combustion. A more energetic fuel than the normal aviation fuels can increase thrust just like in some automobiles and early jet aircrafts, special fuels were used to get more thrust and more power.
You can put more fuel to get a more rich air/fuel mixture but its not the trend these days. Jet engine air/fuel mixture is weak in the order of 70:1, meaning 1kg of fuel for each 70kg of air. Of course the use of afterburner changes all this. But todays research is to improve the understanding of turbulent combustion so that the fuel is "fully" burnt and there is no wastage and no smoke in exhaust. Here the understanding of "Turbulence" is itself a problem in advancement in this field.
we also have the pressure losses in a jet engine. An effort to minimise the pressure losses shall evidently result in higher thrust performance.
Other important parameter, related to combustion, is Turbine Entry Temperature (TET). This area depends on progress in materials. Nowadays, engines are using Single-Crystal materials in turbine blades as they endure higher temperatures.
Then is the thermal coating of turbine blades to save them from severe effects of higher temperatures. A better coating can result in better performance. Then is the turbine blade cooling. If you can come with a liquid or liquid metal that has excellent heat absorbing capabilities and can be used as a coolant, then too thats an improvement and we would be able to increase TET, thus increasing thrust.
Another area is backflow of air from high pressure area to low-pressure area because there is a "gap" between blade tip and casing of engine. This "gap" causes sort of leakage. Any breakthrough in this area shall improve the engine performance.
Coming back to where I started, the most important is nozzle design itself. Its not easy to get a good thrust from a nozzle at all altitudes. The thrust of a conventional nozzle varies with altitude because the back atmospheric pressure on nozzle changes with altitude. Some nozzles are optimised for a certain altitude whereas some are optimised for sea-level altitude.
Having said all this, any improvement in engine thrust is useless if it does not improve the thust/weight ratio. An engine should have at least 10:1 thust/weight ratio to be useful for aircraft because once fitted inside aircraft, the aircraft may get a thrust/weight ratio of hardly 1:1.
Before concluding this post, we must remember that really what matters is "Installed Thrust" and not the "stand-alone thrust". The thrust that we get from an engine on the test-rig is not the same when installed inside an aircraft. At the business end, we want that engine should perform the same way when installed inside the airframe.
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