INCREASE IN EFFICIENCY OF AN AIRCRAFT

Rohan Easwaran, Rohit Hankare, Siddesh Birajdar and Harsh Mistry. Department of Mechanical Engineering, Lokmanya Tilak College of Engineering,Koparkhairne, Navi Mumbai 400709, India. ...................................................................................................................... Manuscript Info Abstract ......................... ........................................................................ Manuscript History


ISSN: 2320-5407
Int. J. Adv. Res. 5(8), 208-215 209 One of the most recent developments in the modification of design to improve the efficiency has been done by the to major companies in avaition ie; Airbus and Boeing. Airbus recentely launched an updated model of the largest passenger aircraft the A380 Plus.
The A380 Plus boasts a promise to airlines that a 13% cost reduction per seat will be achieved , versus the current A380 model, while enjoying the A380"s unique comfort level. The new features of the A380 Plus include a prototype winglet, which promises the winglets will provide up to 4% fuel burn savings. The design changes from the existing design of the A380 are as follows : The new winglets measure approximately 4.7 metres in height (an uplet of 3.5m, and a downlet of 1.2m). It is designed to improve aerodynamics and reduce drag force .
The A380 Plus will have an increased maximum take-off capcity of 578 tonnes providing the flexibility of carrying up to 80 more passengers over today"s range (8,200 nautical miles), or flying a 300 nautical miles further. The A380 Plus features longer maintenance check intervals, a reduced six-year check downtime, and systems improvements, which will reduce maintenance costs and increase aircraft availability .
Boeing in competion to the Airbus A320 launched a new model of their 737 series known as 737 -Max 10 It boats of its newly designed winglets produced by advanced design and manufactuting techniques that allow natural laminar flow . Thus it delivers improved fuel efficiency than any other winglet. Also it has incorporated the latest CFM International Leap 1B engines which promises to deliver a reduction in noise , carbon as well as NOX emissions.
210 In aircraft design, overall propulsive efficiency η is the efficiency, in percent, with which the energy contained in a vehicle's propellant is converted into useful energy, to replace losses due to aerodynamic drag, gravity, and acceleration. It can also be stated as the proportion of the mechanical energy actually used to propel the aircraft. It is always less than 100% because of kinetic energy loss to the exhaust, and less than ideal efficiency of the propulsive mechanism, whether a propeller , a jet exhaust, or a fan. In addition, propulsive efficiency is greatly dependent on the density of air and air speed .
There are two types of efficiencies ; Cycle efficiency and Mechanical Efficiency .
The cycle efficiency, in percent, is the proportion of energy that can be derived from the energy source that is converted to mechanical energy by the engine .Most aerospace vehicles are propelled by heat engines of some kind, usually an internal combustion engine. The efficiency of a heat engine relates how much useful work is output for a given amount of heat energy input.
From momentum considerations, propulsion requires material to be pushed backwards to push the vehicle forwards. In general, energy efficiency is highest when the air or exhaust gas used to propel the vehicle end up travelling as slow as possible for the required thrust, in the frame of reference of the Earth. This is called Mechanical Efficiency-For jet engines dependence of the energy efficiency (η) from the exhaust speed/airplane speed ratio (c/v) for airbreathing jets . For all air-breathing engines the propulsive efficiency is highest when the engine emits an exhaust jet at a speed that is as close as possible to the aircraft velocity. The graph of Efficiency v/s speed ratio is given below -: An increase in efficiency not only guarantees a decrease in the running costs during the flight but also helps to preserve the enviornment as the amount of fuel burnt is deacreased per mautical mile flown . Hence the carbon footprint of the aircraft decreases and vast results can be identified over a longer period of time . Todays world focuses mainly over the issue of polution and saving the environment form its ill effects . Thus is a very important part of research which will help our world in one way or another .
Literature Review:-(A) F. Liu and W. A. Sirignano -: [1] A thermal analysis was carried out and the advantages of Continuous Turbine Burner (CTB) and Inter Turbine burner (ITB) engines for both the turbojet and turbofan configurations were noted. Burning in the turbine passages reduced the trade-off between Specific thrust (ST) and Thrust Specific Fuel Consumption rate (TSFC). It allowed significant increase in ST with only small increase in TSFC. A noticeable benefit for a CTB or ITB engine were, to be able to produce gases of high kinetic energy at high thermal efficiency , by providing a very desirable gas generator as the basis of high-performance engines which are applicable to both military and commercial applications. The parametric studies in the paper enlightened the following: (a) The turbine-burner engines were capable of operations at high compressor pressure ratios. Although conventional engines have an optimal compressor pressure ratio between 30-40 for supersonic flights , beyond which they have diminished thrust and very high TSFC, the turbine-burner engines were capable of operating at pressure ratios higher than 60. Increased compressor ratios generally increased ST and decrease TSFC of the turbine-burner engines. (b) Because of the extended compressor pressure ratio range and also for the fact that the propulsion efficency improves at high speed for jet propulsion, the performances of the turbine-burner engines were significantly superior at higher flight speed than conventional engines. (c) The turbine-burner engines benefited more from efficient, large by pass fans than the conventional engines. The by pass pressure ratio can be optimised for a specific need .

Conclusion:-
The analysis concluded that the 1-ITB engine provides more than 50% increase in ST with equal or lower TSFC over the conventional base turbofan engine. Also the thermal analysis proved that A CTB or ITB engines for both turbojet and turbofan configurations yielded noticable increase in ST with small increase in the TSFC . This can lead to an increase of efficiency of upto 5% [1].
(B) Dr. Jassim M. Abdulkarim Jaff [2] (a) Experimental analysis:-All types of jet engines were studied and their characteristics were noted . The types of jet engines studied were ; Turboprop , Turbojet , Turbofan . A vast thermodynamic analysis of each of the jet engines were taken .
The velocity of air entering the engine was also studied extensively . Also various parts which help in the efficient operation of the aircraft were studied such as ; Turbocharger , Compressor , Turbine , Ignition system , Equivalent Ratio and Nozzle.
213 (1) Most of the possible performance, programmatic, design, and technological parameters that effect of jet engine were analysed. The results indicated that rotor inlet, equivalence ratio, and combustion chamber design are a significant in almost all of the relationships. (c) Derek Sitt - [3] (a) Experimental Analysis - The use of Gear boxes turbofans than traditional turbofans was studied . An experiment with Rolls Royce was conducted.
(b) Observations:-A gearbox allowed the engine to run at optimal speeds while reducing the number of parts required to make the engine. Not only would it increase efficiency, but it also reduced fuel consumption which released fewer harmful chemicals into the atmosphere. The use of geared turbofans would replace conventional turbofans due to superior efficiency , increased sustainability and more prominent economic benefits The differences between the regular and geared turbofan are -214 a. Fan blade diameter, b. Reduced number of parts, and c. The addition of a planetary gearbox. [3] It was found that though each difference was not that significant on its own, the combined effect of each of them would result in a much more efficient engine. Longer and wider fan blades would provide the geared turbofan and in increased intake of volumes of air. The larger quantities of air can be used to provide more thrust in the form of bypass air. A downside to larger fans is the engine size. The larger engine is necessary to accommodate larger fans , also the increased volume of air passing through the turbofan. [3] To the contrary, the geared turbofan weighs less than the conventional turbofan due to the less number of parts. The lesser number of components can be attributed to the planetary gearbox, which optimizes the speed of each part of the turbofan. The gearbox will be inserted directly between the fan and the compressor blades. By optimizing both the compressors and turbine, it would reduce the required number of blades.
(c) Conclusion:-The conclusion can be analysed with an example -Boeing 787 Dreamliner has a life of around 40,000 cycles. 1 cycle is considered the time take-off to the time when it lands. With a price of 200 million dollars, this Boeing aircraft costs around 5,000 dollars per flight. In addition, the cost of fuel for a transatlantic flight costs upwards of 15,000 dollars. Using these estimates, the cost of fuelling is about three times as expensive as the plane itself. In the future, and engine like Rolls-Royce"s Ultra Fan could drastically reduce fuelling costs thanks to its projected 25% increase in fuel efficiency.
Thus the use geared turbofans on aircrafts lead to a reduction of fuel burnt by 16 percent, emissions reduced by 50 percent and the engine noise reduction by 75 percent . [3] Conclusion:- important role in determining the efficiency. (C) Geared turbofans were preferable than normal turbofans . It was concluded that a reduction of fuel burnt was by 16 percent, emissions were cut by 50 percent and engine noise was reduced by 75 percent.