What is Jet: Definition and 327 Discussions

Jet fuel or aviation turbine fuel (ATF, also abbreviated avtur) is a type of aviation fuel designed for use in aircraft powered by gas-turbine engines. It is colorless to straw-colored in appearance. The most commonly used fuels for commercial aviation are Jet A and Jet A-1, which are produced to a standardized international specification. The only other jet fuel commonly used in civilian turbine-engine powered aviation is Jet B, which is used for its enhanced cold-weather performance.
Jet fuel is a mixture of a variety of hydrocarbons. Because the exact composition of jet fuel varies widely based on petroleum source, it is impossible to define jet fuel as a ratio of specific hydrocarbons. Jet fuel is therefore defined as a performance specification rather than a chemical compound. Furthermore, the range of molecular mass between hydrocarbons (or different carbon numbers) is defined by the requirements for the product, such as the freezing point or smoke point. Kerosene-type jet fuel (including Jet A and Jet A-1, JP-5, and JP-8) has a carbon number distribution between about 8 and 16 (carbon atoms per molecule); wide-cut or naphtha-type jet fuel (including Jet B and JP-4), between about 5 and 15.

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  1. P

    Estimating the force exerted by a water jet on a flat plate - Bernoulli vs Momentum Equation

    Hi, Case 1: Imagine a steady liquid water jet with unit cross sectional area - incompressible and inviscid. density D and uniform velocity V. Operating atmospheric pressure is 0.0 Pa. The jet is in air ( no air resistance ) and hits a stationary flat plate perpendicularly. Applying momentum...
  2. Astronuc

    Lifetimes of jet aircrafts and their engines

    I found this article today. Jalopnik - Here's How Often Airlines Replace the Jet Engines on Passenger Planes https://jalopnik.com/how-airlines-decide-to-replace-jet-engine-boeing-airbus-1850275010
  3. B

    B Gamma Ray Burst / Jet Questions

    The 1st photo is a Google image of a Gamma ray Burst in space, the image in the other photo is being emitted from a device I am playing around with. I am just wondering what is the cause of or what dictates the behavior of actual Gamma Ray Bursts in space vs whatever light patters are in the...
  4. G

    Fluid mechanics: water jet impacting an inclined plane

    I was looking at an example of fluid mechanics and I don't understand this. Statement figures: CONTINUITY EQUATION $$\left. \dfrac{dm}{dt}\right]_{MC}=(\dot{m}_2+\dot{m}_3)-\dot{m}_1=0$$ $$\dot{m}_1=\dot{m}_2+\dot{m}_3$$ $$\rho c_1A_1=\rho c_2A_2+\rho c_3A_3$$ $$\rho c_1 h1=\rho c_2 a1+\rho...
  5. Astronuc

    J58 jet engine and supersonic flight

    We've had several threads on the SR-71 (and related craft) and the J58 propulsion system. https://www.physicsforums.com/threads/sr-71-blackbird-supersonic-aircraft.68694/ https://www.physicsforums.com/threads/j-58-engine-inlet-spike.413262/...
  6. person123

    I Momentum of a Water Jet Impacting Plate

    Suppose you have a jet of fluid (say water) traveling vertically upward at a constant velocity. It impacts a stationary horizontal plate and so moves radially outward in all directions. Assume that there's no energy loss during the impact, so the speed of the fluid remains constant. Is momentum...
  7. M

    Researching Turboprops: Fuel Comparison of Hydrogen, Methanol, & Jet A1

    Hello I'm trying to get some good reference material so I can do a literature review on Turboprops and a comparison of PSFC of Hydrogen/Methanol/Jet A1 fuels for turboprops. If anyone knows any good source material for this please let me know as I have struggled to find anything. Regards, Michael
  8. R

    How difficult will it be to build a 'hybrid' Jet engine?

    Hi, Here is a question - somewhat futuristic and at the moment, hypothetical. How difficult will it be to build a 'hybrid' Jet (turbofan) engine? The engine should be able to handle both Kerosene and (gaseous) Hydrogen as fuel. After burning the kerosene for a while, Hydrogen will take over as...
  9. JD_PM

    I Understanding the thrust generated by a typical jet engine

    I was reading propulsion chapter 9 of Anderson's Flight book (http://213.230.96.51:8090/files/ebooks/Muhandislik/Anderson J.D. Introduction to flight (8ed., MGH, 2016)(ISBN 9780078027673)(O)(929s) EAs .pdf) and came to Figure 9.18 b) & c), Figure 9.19 (I cannot post the image here due to...
  10. mopit_011

    Force on three Bolts holding up a Jet Engine

    My solution was that there would be a force of 0 Newtons on the bolt as the bolt is not moving. But this answer is wrong. Where am I going wrong?
  11. O

    I Fluid force from a fluid flow vs. from a fluid jet

    In fluid flow (such as wind), the force exerted on a perpendicular surface is derived from kinetic energy and is ρAv^2/2. But in problems involving a jet of fluid that strikes a plate, the force is derived from momentum and is explained to be ρAv^2, lacking the 1/2 factor. Can someone please...
  12. berkeman

    GE initiates testing on second XA100 "adaptive cycle" fighter jet engine

    This is pretty interesting. It sounds like GE and the Air Force have been able to make some good improvements recently...
  13. N

    What is necessary for a hypothetical supersonic speed Radio Controlled Jet?

    Hi everyone! :) While i watched rc jet exhibitions on youtube, i find that the most fast of this RC reached +700 Km/h. When i browse more information about the tourbine, i realized that for a hypothetical supersonic RC the mechanical system of the tourbine must have a complete air compressor...
  14. ZdMh

    About difference in Velocity and motion in Jet engines

    I was watching a video about jet engines, and it was obvious for me and for the instructor that if we compress air at high speed from the gas turbine inlet, then after multiple stages collide with the turbines blades inside, the body will move in the sense of difference in velocity, so forward...
  15. W

    Thrust of Jet Plane: Why Is -313m/s^2 Wrong?

    What is wrong with saying that since the speed of fuel goes from 0 to -313m/s (rel to ground) in 1s, then its acceleration is -313m/s^2. This leads to wrong answer according to author's solution but I don't see why.
  16. Twigg

    A How Does Jet Injection Work in Fluid Dynamics?

    Hi all, Sorry to post an open ended question, but I'm struggling because I don't know the right terms I need to do a literature search on my own. Any kind of feedback here is helpful! I'm interested in the dyanmics of a class of device I've heard described as a "jet injector". I know of two...
  17. S

    Piston Engine versus Jet Engine Power

    Hello All The power output of piston engines fitted to aircraft were (and still are?) specified in terms of their HP rating, whereas jet engines are typically rated in terms of their trust. For example, a Mosquito two engined fighter/bomber was equipped with two Merlins, each producing...
  18. S

    Jet pack spotted at 6000 feet over LAX

    https://edition.cnn.com/2020/10/14/us/jetpack-guy-back-lax-trnd/index.html What kind of jetpack is used here? I wonder when they will be available at amazon.
  19. M

    I Understanding Gluon Self-Interaction and Quark/Gluon Jet Differentiation

    Hello! Based on QCD we can have gluon self-interaction i.e. a vertex with 3 or 4 gluons. What were the experimental evidences by which the existence of these vertices was confirmed? Also, how does one differentiate between a quark and a gluon induced jet? Thank you!
  20. Robert Friz

    I What Mechanism Creates the Jet Emanating From a Quasar?

    Given that a quasar is a super massive black hole with an accretion disk rotating at some significant percentage of the speed of light, what is the mechanism that generates the enormously luminous jet that emanates from the "poles" of the black hole that has become a quasar? a. The magnetic...
  21. person123

    Parabolic Pressure Distribution in a Jet

    Assume the jet is straight but the radius of the jet varies over it's length (like a jet of water falling which narrows due to gravitational acceleration). Also ignore viscosity. A pressure gradient would be required to accelerate the fluid radially. Because during an expansion transformation...
  22. A

    A jet engine's shaft is neutral in the direction of thrust?

    I think i read somewhere that jet engine shaft is neutral,because forces at turbine and compressor cancle out,so that mean axial berings don't have force on it in direction of thrust!? (this can't be true,becsue in that case thrust will be zero...) But if this is true ,against what pressure...
  23. mnb96

    I Question on tangent space and jet spaces

    Hello, I am reading some material related to jet spaces, which at first glance seem to be a generalization of the concept of tangent space. I am confused about what is the correct definition of a jet space. In particular, given a map ##f: X \rightarrow Y## between two manifolds, what is the...
  24. R

    Personal Jet Boat Water Craft Thrust Question

    Assume a jet boat or personal water craft (JetSki, etc) has a movable propulsion nozzle. This nozzle can be moved vertically so that the water jet driving the boat forward can be either above the surface or below the surface of the water. Further clarification. You are speeding along on your...
  25. VTOL147

    VTOL Jet Engine Aircraft and VTOL Jet Engine

    I am thinking about VTOL jet engine aircrafts like the following example (an ambulance). To be able to buid that kind of aircraft VTOL jet engines are needed. At the moment there are no VTOL jet engines available, but I have my own proposal: I have questions to jet engine experts. Is my...
  26. S

    Water jet strikes a plate and slows down due to frictional forces?

    [moderator note: super size font formats removed.] When a water jet strikes a plate (3m plate) at an angle (like 60 degrees), velocity of water decreases as it travels downstream. I know the major contributor that slows down water is probably wall frictional force but how to quantify this...
  27. Whitestar

    I C Could a Jet Helicopter with Wings Fly at Supersonic Speeds?

    I have always been fascinated with helicopters and it was the tv series "Airwolf" that started it off. In the show, it was acknowledged that Airwolf is the only helicopter that can fly at supersonic speeds. Granted, I'm no physicist, but I do know it is impossible for a helicopter to fly at...
  28. C

    Tracking Spread of a water jet out of a downward-facing pipe

    Hey folks, I'm back with a new question. If I have a pipe of known diameter, with a known volume of water at a known pressure discharging downwards into atmosphere, how can I calculate the radius of its "spread". That is, how can I find what area beneath the discharging pipe is being covered...
  29. I

    Force exerted by a deflecting water jet

    Homework Statement Homework Equations Impulse momentum theorem, Newton's second law The Attempt at a Solution Now the water will impart some impulse to her. Let ##\bar{v_1}## be the initial horizontal velocity of the water jet and let ##\bar{v_2}## be the final vertical velocity of the jet...
  30. Alexanddros81

    A jet comes in for a landing on solid ground

    Homework Statement A jet comes in for a landing on solid ground with a speed of 100m/s, and its acceleration can have a maximum magnitude of ##5.00m/s^2 ## as it comes to rest. (a) From the instant the jet touches the runway, what is the minimum time interval needed before it can come to rest...
  31. P

    Can a Jet Engine Remove drag from the Hyperloop tunnel?

    [Moderator: link removed] Can a jet engine the size of the tunnel mean that you can have an effectively have drag-free vehicle? Any lorry tethered to the jet engine would be basically be drag free? Is this correct? Thanks
  32. Y

    What formula would i use this for this HW problem? (Aircraft carrier jet launch)

    *This is an introductory physics class for non-math majors. A typical jet fighter launched from an aircraft carrier reaches a take-off speed of 175mph over a distance of 310 ft. assuming the acceleration is constant, what is the jet's acceleration in (meters per second)? 2) how long does i...
  33. M

    What does the word 'Jet' mean in fluid mechanics?

    What does it mean the word 'Jet' in fluid mechanics, special when it depends on the free surface?!
  34. vysqn

    Acceleration of a car and jet plane problem

    As we know, POWER is what accelerate a car, FORCE itself doesn't accelerate a car, if FORCE cousing movement it change into work, and work over time = POWER. The FORCE from jet engine pushes a plane forward. But as we know (or I'am wrong) FORCE don't push enything, only POWER couses...
  35. FelixLudi

    I Possibility of a quasar jet laser impacting Earth directly

    I understand quasars as black holes with an accretion disk and occassional jets of mass being shot out of the black hole from it's top and bottom. (Correct me if I'm wrong) If so, what is the actual possibility for that type of quasar to be rotated so heavily that it rotates on a horizontal...
  36. R

    The diameter of the exhaust nozzle of jet engines

    Hello, Can anybody please tell me the typical diameter of the exhaust nozzle of a jet engine? I know, there are different types of engines and nozzle types also vary. For instance, I am interested to know the typical diameter of the nozzle of a turbofan engine. Thanks
  37. P

    Calculating Speed and Force in Water Jet Impact | Fluid Mechanics Homework

    Homework Statement "A jet of water issues from a nozzle, of diameter h_1=0,102 m (and depth b=1 m), at a speed U_1=2,02 m/s. The jet strikes a flat plate of mass M=2,05 kg, as shown in figure, and it breaks into two jets of equal speed and diameter h_2=0,122 m and h_3=0,102 m. Determine the...
  38. FreeBob

    Calculating equivalent horsepower for a jet engine

    Trying to remember some basics. I know the thrust of a jet engine. I'm thinking about equivalent HP. I can establish HP at a given speed, but what about while accelerating? I will display my ignorance here :( Power for static, non accelerating flight: Power = [Thrust x Airspeed] Thrust...
  39. A

    Acceleration in water using a water jet

    Hi, everyone. I'm working on a personal project and I need some insight from the intelligent minds here. I'm trying to calculate the thrust that a jet motor on a marine craft needs to exert in order to accelerate the craft in a certain direction. What are the necessary factors to determine the...
  40. nashikin58

    Rotary or centrifugal jet spinning (nanofiber)

    Hi, I am a research student, working on rotary jet spinning. while spinning, nanofibers are formed but it's not attached properly to the collector. It became like a spider web. You guys have any idea why it became like that?
  41. S

    Calculating suction area around the intake of a jet engine

    I am looking to calculate the area around the engine where, if an object enters this area, it would be "ingested" by the engine (subsonic flight). In other words, I am looking to draw the shape around the engine, where the air within that shape is disturbed air (being ingested by the engine)...
  42. E

    B Exploring the Possibility of a Warp Jet: A Theoretical Approach

    I was looking at videos on how a warp drive theoretically could work: by compressing space in front and expanding space in the back. This reminded me of a jet engine compressing air and blasting it out of a nozzle. My question is, could you build a sort of warp jet that would compress space...
  43. orb_yt

    How are/were computers used in jet engine design?

    Hello all, I have been tasked with writing a very short article regarding the use of computers and software in early jet engine design up to modern times. I've been having a relatively hard time finding reading material through Google. I understand that modern jet engine designers use CAD...
  44. D

    How to Calculate E-Balance for a Jet Ejector?

    I am working on problem that has to deal with a jet ejector. For the life of me, I cannot figure out the E-Balance equation for it. Below is a cut away image of the ejector. The fluid is the same so using the ideal gas law I do not think should be included. Any help is greatly appreciated...
  45. J

    Jet fighter flying in a vertical loop

    Homework Statement A jet fighter flies in a vertical circle of diameter 1000 m. The speed of the aeroplane at the bottom of this circle is 185 m s-1. For the aeroplane at this point, calculate: Apparent weight Homework Equations Fc = mv^2/r Ac = v^2/r Fn = Fg + Fc The Attempt at a Solution...
  46. G

    Air resistance that affects jets and people

    I wanted to ask. Since jets fly at great speed, often even supersonic, I'm curious about next things: 1) What is the relation between air resistance force and energy? 2) How does all that force resistance affect a pilot? 3) What protection do they have, if any? 4) And purely speculative...
  47. W

    Charged liquid jet instability

    I am dealing with a problem of instability of an infinitely long charged liquid jet. When there is a change is surface profile(which originally is a column with radius R), it surface charge density changes, thus the electric energy change of the liquid jet is E (due to surface charge density...
  48. T

    Thermodynamics: The Jet Engine

    Good evening everyone,I had several questions regarding basic thermodynamics. After going to Paris Airshow (Le Bourget), lot's of questions came to my mind after looking at those beautiful Jet engines...I have always had a very basic understanding on these engines: a fan, a compressor (High and...
  49. B

    MHB Shower Head Jet Separation: Seeking Assurance

    I previously posted this question on this website:https://math.stackexchange.com/questions/2297129/shower-head-jet-separation However, I'm not sure if the answers I got were correct or the answers that I found out were correct, or if neither of them were. Can anyone help assure me which one is...
  50. T

    Fuel with Static Air in a Jet engine

    Good evening, Today's planes' need bleed air to start. Above a certain speed, igniters fire up and we inject fuel inside the combustor chamber. Why do we need to have the engine running to inject fuel (around 20%N2)? Can we simply not inject fuel with static air (i.e. when engine is not...
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