Questions tagged [efficiency]

Efficiency is the (often measurable) ability to avoid wasting materials, energy, efforts, money, and time in doing something or in producing a desired result. In a more general sense, it is the ability to do things well, successfully, and without waste.

Filter by
Sorted by
Tagged with
0
votes
0answers
13 views

What is the difference in efficiency between variable pitch prop and two fixed propellers for take-off and cruise speeds?

Push-pull configuration aircrafts usually feature identical engines and propellers working only in tandem for multiple reasons like higher speed, better climb rate, reliability, cost, ease of ...
6
votes
0answers
87 views

Can ekranoplans (GEV) be more efficient than traditional airliners?

Ekranoplans or Ground Effect Vehicles (GEV) fly low enough to the ground that their wings stay in the ground effect. This increases lift and efficiency. But GEV fly in the lower atmosphere (...
2
votes
1answer
67 views

How can I calculate turbofan efficiency as a function of turbine inlet temperature?

I know that increasing the turbine inlet temperature (TIT) increases the overall efficiency of the jet engine. So I wanted to find the overall efficiency as a function of TIT. I used the equations ...
0
votes
1answer
123 views

Why are there no large turboprop passenger airliners? [duplicate]

If turboprop engines are more efficient than turbofan/jet engines at lower speeds, and have a lower specific fuel consumption, why are there no large passenger airliners that utilize the turboprop ...
2
votes
1answer
63 views

Is there an equation for jet engine efficiency as a function of turbine inlet temperature?

I know that there is a relation between the turbine inlet temperature and the engine's efficiency. But, can anyone provide an equation or efficiency as a function of just the turbine inlet temperature?...
5
votes
1answer
204 views

How do I obtain the max endurance altitude?

There are excellent explanations of the physics that determine maximum endurance speed here, here, and here. I was thinking of aircraft that have to be "on station" without an indicated altitude and ...
2
votes
2answers
121 views

How does fuel efficiency depend on wing configuration?

Which of the following wing configurations is the most fuel-efficient?
1
vote
1answer
104 views

When Airplane is reducing altitude from flight level (cruise), which one is more efficient

When an airplane is reducing altitude, say due to preparation for landing, the nose is tilted down. That I got from a video on Youtube which explains the way an airplane is going down until it reaches ...
4
votes
1answer
156 views

How much can a plane benefit from another planes wake?

Could a smaller plane fly in a V formation behind a much larger plane to reduce fuel consumption significantly more than a plane its own size? At what point does flying in a larger planes wake become ...
2
votes
1answer
183 views

Could a rotor head wing be plausible?

Could a helicopter support a detachable wing with no controls on top of the rotor head in place of a radar dome? Could the rotor head be made to support more weight? Would it be more fuel efficient at ...
9
votes
1answer
778 views

How is a Flying-V more efficient than current fuselage-over-wing designs?

It's claimed the plane will use 20% less fuel than the Airbus A350-900 while carrying a similar number of passengers -- the Flying-V will seat 314, while the Airbus A350 seats between 300 and 350. The ...
25
votes
2answers
6k views

Did airlines fly their aircraft slower in response to oil prices in the 1970s?

Modern airliners generally have lower cruise speeds than those of comparable aircraft from 40 years ago (the venerable Boeing 737 seems to be something of an exception; it has always had a more ...
0
votes
0answers
41 views

Turbine engine combustion efficiency [duplicate]

What I read about combustion efficiency of jet engine is ratio of (Th-Tc)/ Th where Th combustion chamber temp and TC exhaust temp. I also read this efficiency reduces with increase in altitude and ...
5
votes
1answer
262 views

What is “Carson cruise” and can I determine it myself?

Mike Y. just posted an answer containing the following: With today’s fuel costs, the Carson cruise angle of attack, which represents the most efficient way to fly fast with the least increase in ...
27
votes
5answers
10k views

Is it cheaper to drop cargo than to land it?

Is it more fuel efficient to drop cargo onto a runway from the air en route to a final destination than to land and unload it using a more fuel efficient plane?
1
vote
1answer
112 views

What values can/should be used for the isentropic efficiency of a compressor and turbine?

I was trying to model an turbofan aircraft engine using Matlab and Simulink. In the process I have fixed certain parameters to some specific values which are nominal operating values of the parameters....
6
votes
1answer
2k views

Why is the A330neo more efficient than the A350 on shorter routes?

For A330neo Wikipedia page, is written: A330neo enables profitability on shorter ranges where the longer-range A350 and Boeing 787 aren't optimized. For what reasons it is true? A330 and A350 ...
4
votes
1answer
172 views

Why does the rotor thrust decrease at smaller tip clearance for shrouded rotor?

Consider this system, rotor with shroud: From this research, we see that: at the same rpm, the rotor thrust decreases,the shroud thrust increases as tip clearance decreases. But why does the rotor ...
4
votes
6answers
703 views

What are the advantages of using a ramjet in an air-to-surface missile?

Which are the advantages of using a ramjet compared to a rocket engine in an air-to-surface missile? I suppose the cost rises a lot, so why do some countries use ramjets as a way of propelling ASM ...
-3
votes
3answers
118 views

Is it possible to calculate possible fuel savings of known turbofan engines if operational heat could be increased [closed]

Starlite is liquid paint like substance invented in 70s and perfected in the 80s by the late British inventor Maurice Ward (1933-2011). It is said to be able to withstand heat from 78 nuclear ...
5
votes
1answer
326 views

How do I optimize a turbofan engine to fly lower and slower instead of higher and faster?

I was reading something about someone who was doing this and I'm intrigued, but I have no idea what you actually do to optimize the engine to be better at lower altitudes and lower speeds?
6
votes
2answers
724 views

What passenger airplane has the lowest fuel efficiency?

What is the airplane with the lowest fuel efficiency? To set some parameters, let's limit it to the following: Must be manufactured between 1960 and modern day. Must be a non-military passenger ...
23
votes
6answers
9k views

Why then don't aircraft fly even higher, for even greater efficiency? [duplicate]

After reading various superb QA on here I now see that (basically) aircraft are more efficient per passenger-mile, at higher altitudes. Why don't we go even higher, than current typical airliner ...
3
votes
3answers
347 views

Does shrouding a propeller minimize induced drag by equalizing the downwash velocity along its blades?

EDIT: It's not a duplicate of Are ducted fans more efficient? That question and the answers doesn't address the reason for the higher theoretical efficiency, it is more about efficiency in practice (...
1
vote
0answers
83 views

Does Froude Efficiency represent an upper bound for propellers in certain flight / aircraft conditions?

I used the Simple Propeller Theory to calculate the Froude Efficiency for my theoretical propeller-driven craft (at 65k feet). Here are the results: https://ibb.co/kPPqzU. My results were that, for ...
1
vote
2answers
459 views

How is a propeller diameter for given application determined?

let's say I need 1000 N of thrust for a given aircraft and flight velocity. I have available a fixed pitch propeller with a given shape, and thus given performance to advance ratio curves. Let's say ...
2
votes
1answer
920 views

What is the efficiency of the turbine of a modern jet engine?

What is the turbine efficiency of a modern jet engine? Just the turbine efficiency only. What percentage of fuel energy the turbine converts into mechanical energy.
1
vote
2answers
558 views

Propeller Characteristics at Different Altitudes

Assuming I have a propeller with a given diameter (D), pitch, blade twist, and number of blades, I can theoretically analyze discrete airfoil sections in XFOIL and come up with lift and drag polars ...
4
votes
2answers
267 views

Would increasing rotor disc diameter increase efficiency in a helicopter by reducing disc loading?

Despite the obvious drawbacks of a larger rotor diameter would the reduced disc loading increase efficiency during hover and forward flight?
4
votes
1answer
421 views

Propeller Efficiency calculation different by two methods

Please refer to this MIT page which I used for my calculations: https://web.mit.edu/16.unified/www/FALL/thermodynamics/notes/node86.html I calculated my aircraft propeller's prop, thrust, and torque ...
-1
votes
2answers
311 views

Does wing paint colour improve airplane fuel efficiency?

If birds that fly very long distances like seabirds have darker colours on top of the wings and lighter colours underneath the wing, is it possible that painting airplane wings similarly may improve ...
3
votes
4answers
616 views

Why are helicopters less efficient than planes?

At higher speeds, advancing helicopter blades will operate at velocities approaching mach 1, reducing efficiency. But what about lower speeds? A helicopter is basically a wingless plane with a giant ...
7
votes
1answer
349 views

Why divide the blades of a 9 blade propeller into 3 groups?

In a youtube video an airboat is featured with two contra-rotating propellers, each holding nine blades. Interestingly those nine blades are not spaced evenly, but grouped into three groups. I've ...
3
votes
2answers
209 views

Can lift be equated to how much air is moved?

The explanation for lift that I find easiest to visualize is that air is deflected downward by the wing. This downward action causes an equal and opposite reaction of an upward force against the plane,...
5
votes
2answers
1k views

Is 1 propeller always more efficient than 2?

Based on other answers I've read here (1) (2) (3), a single large blade propeller is the most efficient type of thrust you can get. There are 2 reasons for this (as I understand it). Firstly, ...
0
votes
0answers
135 views

How turbofan engine efficiency increases over altitude or speed? [duplicate]

I am confused a lot about the efficiency and thrust relation with altitude and velocity of an aircraft. If thrust is related to air mass flow and velocity diffrence of bypassed air - exhaust gases ...
2
votes
4answers
450 views

How can larger wingspan decrease the strength of wingtip vortices?

In the last paragraph from the link below, it states that Vortex Strength is inversely proportional to Wingspan. Why is this? http://avstop.com/ac/flighttrainghandbook/wingtipvortices.html EDIT: ...
1
vote
1answer
139 views

Propeller Curve Modification on Test Rig

this is my first stack exchange question so please bear with me if I have missed a rule: I tried searching for this question to no avail. I have an off-the-shelf propeller for the purpose of eventual ...
3
votes
1answer
218 views

How can you explicate the efficiency of a turbofan engine with Carnot's theorem?

From Carnot's theorem, we know that efficiency is $$ \eta = 1-\dfrac{T_c}{T_h}$$ where $T_c$ is the temperature of the cold reservoir and $T_h$ the temperature of the hot reservoir. But what do we ...
6
votes
1answer
556 views

Are two twin-jet flights more efficient than one quad-jet flight?

Ignoring for this question the issue of flexibility for the airline, would it be more (fuel, cost) efficient to have a single flight with a 4 engine plane than to have two flights with 2 engine planes....
4
votes
2answers
954 views

Why is there still a preference for turboprop airliners over the new regional jets? [duplicate]

In the 1950s and in the early 1960s, jets were mostly available as fighter/military or big, long haul aircraft. Regional aviation was based primarily on piston aircraft that could operate in smaller ...
3
votes
1answer
3k views

How to select the most efficient airfoil for low speed flight?

What airfoil (or family) has the highest $C_L/C_D$ ratio at speeds in the $50\:km/h$ range. The use case would be an ultralight with a max speed of $50\:km/h$
0
votes
2answers
842 views

Are two little engines or one big engine more efficient for an ultralight?

For an ultralight, should two engines weighing 10kg each and making 7hp each OR one engine weighing 20kg and making 14hp be used?
1
vote
4answers
363 views

How bad is the efficiency of jet engines under low loads?

VTOL operations need 4-5 times more thrust than a conventional take-off of an aircraft. If you don't want to install additional lift-engines into a hypothetical aircraft and use thrust vectoring to ...
-5
votes
1answer
371 views

How much fuel is used for preheating the outer engines of a four-engine airliner that were not used for taxiing?

Many questions and observations here have highlighted the idea of using some kind of electric towing system for towing airplane to and from the runway, instead of using fuel to taxi. One of the ...
14
votes
1answer
9k views

Which jet engines have the highest thermal efficiency?

Some automakers (Mercedes-Benz, Toyota) have recently been making news about the improved thermal efficiency of their engines, stating that they reached the 50% mark. I was wondering if it was the ...
2
votes
2answers
447 views

Is a propeller with two long blades more efficient than one with three shorter blades? [duplicate]

Is a longer, two-bladed propeller more efficient than a three-bladed propeller with a smaller diameter?
-4
votes
1answer
201 views

Would an extra fan make turbofans more efficient in cruise?

A turbo fan engine cannot use all of its available thrust in cruise any longer that it normally does at today's technologies, otherwise it would risk a meltdown of the internal hot engine parts and ...
8
votes
3answers
779 views

Would a coaxial propeller with the second prop slower and larger improve speed?

Looking at various propeller designs, I started wondering about these limitations: Large propellers at high speeds have tips going supersonic Scimitar props attempt to keep prop tip from going ...
1
vote
0answers
83 views

Would this be an accurate method of fuel consumption comparison?

I'm looking to compare the fuel consumption of regional jets in the US and the stated efficiency of the Bombardier CS100. At the moment, I'm considering using data from the Bureau of Transportation ...