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    3. SPATER Gas Turbine In an aircraft gas turbine the output of the turbine is used to turn the compressor (which may also have an associated fan or propeller). The hot air flow leaving the turbine is than accelerated into the atmosphere through an exhaust nozzle (Fig. la) to provide thrust or propulsion power:

    4. SPATER FUNCTION OF TURBINE A portion of the kinetic energy of the expanding gases is extracted by the turbine section, and this energy is transformed into shaft horsepower which is used to drive the compressor and accessories.





    9. SPATER

    10. SPATER TURBINE BLADE COOLING Current turbine inlet temperatures in gas turbine engines are beyond the melting point of the turbine blade material. To prevent the blades from melting, turbine blade cooling methods are applied to the first turbine stages. Since convectively cooled flow fields and temperature fields are coupled and interact strongly, it is necessary to understand the flow physics in order to accurately predict how cooling will behave. In case of the rotating turbine blades, the effects of rotation also influence the flow. Centrifugal forces as well as the Coriolis force have to be included in the analysis. The present research project is an experimental and computational investigation of the flow through internal turbine blade cooling passages. In the first phase, the flow in a straight, stationary cooling channel is observed. Pressure measurements as well as hot-wire and PIV measurements are used to determine efficacy of different turbulator geometries. In the phase 2, the flow in a rotating cooling channel with an 180 bend will be investigated using PIV.

    11. SPATER Advantages of the gas turbine It is capable of producing large amounts of useful power for a relatively small size and weight Since motion of all its major components involve pure rotation (i.e. no reciprocating motion as in a piston engine), its mechanical life is long and the corresponding maintenance cost is relatively low. Although the gas turbine must be started by some external means (a small external motor or other source, such as another gas turbine), it can be brought up to full-load (peak output) conditions in minutes as contrasted to a steam turbine plant whose start up time is measured in hours. A wide variety of fuels can be utilized. Natural gas is commonly used in land-based gas turbines while light distillate (kerosene-like) oils power aircraft gas turbines. Diesel oil or specially treated residual oils can also be used, as well as combustible gases derived from blast furnaces, refineries and the gasification of solid fuels such as coal, wood chips and bagasse.

    12. SPATER Difference between impulse and reaction turbine


    14. SPATER A ramjet, sometimes referred to as a stovepipe jet, or an athodyd, is a form of jet engine that contains no major moving parts. Unlike most other airbreathing jet engines, ramjets have no rotary compressor at the inlet, instead, the forward motion of the engine itself 'rams' the air through the engine. Ramjets therefore require forward motion through the air to produce thrust. Ramjets require considerable forward speed to operate well, and as a class work most efficiently at speeds around Mach 3, and this type of jet can operate up to speeds of at least Mach 5. Ramjets can be particularly useful in applications requiring a small and simple engine for high speed use; such as missiles. They have also been used successfully, though not efficiently, as tip jets on helicopter rotors. Ramjets are frequently confused with pulsejets, which use an intermittent combustion, but ramjets employ a continuous combustion process, and are a quite distinct type of jet engine



    17. SPATER Axial turbine blade vortex balding A turbine blade for a turbine engine having one or more cavities in a trailing edge of the turbine blade for forming one or more vortices in inner aspects of the trailing edge. In at least one embodiment, the turbine blade may include one or more elongated cavities in the trailing edge of the blade formed by one or more ribs placed in a cooling chamber of the turbine blade. The elongated cavity in the trailing edge may have one or more orifices in the rib on the upstream side of the cavity. The orifice may be positioned relative to a vortex forming surface so that as a gas is passed through one or more orifices into the elongated cavity, one or more vortices are formed in the cavity. The gas may be expelled from the cavity and the blade through one or more orifices in an inner wall forming the pressure side of the turbine blade

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    19. SPATER INLETS SUBSONIC INLETS For aircraft that cannot go faster than the speed of sound, like large airliners, a simple, straight, short inlet works quite well. On a typical subsonic inlet, the surface of the inlet from outside to inside is a continuous smooth curve with some thickness from inside to outside. The most upstream portion of the inlet is called the highlight, or the inlet lip. A subsonic aircraft has an inlet with a relatively thick lip. SUPERSONIC INLETS An inlet for a supersonic aircraft, on the other hand, has a relatively sharp lip. The inlet lip is sharpened to minimize the performance losses from shock waves that occur during supersonic flight. For a supersonic aircraft, the inlet must slow the flow down to subsonic speeds before the air reaches the compressor. Some supersonic inlets, like the one at the upper right, use a central cone to shock the flow down to subsonic speeds. Other inlets, like the one shown at the lower left, use flat hinged plates to generate the compression shocks, with the resulting inlet geometry having a rectangular cross section. This variable geometry inlet is used on the F-14 and F-15 fighter aircraft. More exotic inlet shapes are used on some aircraft for a variety of reasons. The inlets of the Mach 3+ SR-71 aircraft are specially designed to allow cruising flight at high speed. The inlets of the SR-71 actually produce thrust during flight. HYPERSONIC INLETS Inlets for hypersonic aircraft present the ultimate design challenge. For ramjet-powered aircraft, the inlet must bring the high speed external flow down to subsonic conditions in the burner. High stagnation temperatures are present in this speed regime and variable geometry may not be an option for the inlet designer because of possible flow leaks through the hinges. For scramjet-powered aircraft, the heat environment is even worse because the flight Mach number is higher than that for a ramjet-powered aircraft. Scramjet inlets are highly integrated with the fuselage of the aircraft. On the X-43A, the inlet includes the entire lower surface of the aircraft forward of the cowl lip. Thick, hot boundary layers are usually present on the compression surfaces of hypersonic inlets. The flow exiting a scramjet inlet must remain supersonic.

    20. SPATER INLET EFFICIENCY An inlet must operate efficiently over the entire flight envelope of the aircraft. At very low aircraft speeds, or when just sitting on the runway, free stream air is pulled into the engine by the compressor. In England, inlets are called intakes, which is a more accurate description of their function at low aircraft speeds. At high speeds, a good inlet will allow the aircraft to maneuver to high angles of attack and sideslip without disrupting flow to the compressor. Because the inlet is so important to overall aircraft operation, it is usually designed and tested by the airframe company, not the engine manufacturer. But because inlet operation is so important to engine performance, all engine manufacturers also employ inlet aerodynamicists. The amount of disruption of the flow is characterized by a numerical inlet distortion index. Different airframes use different indices, but all of the indices are based on ratios of the local variation of pressure to the average pressure at the compressor face. The ratio of the average total pressure at the compressor face to the free stream total pressure is called the total pressure recovery. Pressure recovery is another inlet performance index; the higher the value, the better the inlet. For hypersonic inlets the value of pressure recovery is very low and nearly constant because of shock losses, so hypersonic inlets are normally characterized by their kinetic energy efficiency. If the airflow demanded by the engine is much less than the airflow that can be captured by the inlet, then the difference in airflow is spilled around the inlet. The airflow mis-match can produce spillage drag on the aircraft.

    21. SPATER SCRAMJET A scramjet (supersonic combustion ramjet) is a variation of a ramjet with the distinction being that some or all of the combustion process takes place supersonically. At higher speeds, it is necessary to combust supersonically to maximize the efficiency of the combustion process. Projections for the top speed of a scramjet engine (without additional oxidiser input) vary between Mach 12 and Mach 24 (orbital velocity). The X-30 research gave Mach 17 due to combustion rate issues. By way of contrast, the fastest conventional air-breathing, manned vehicles, such as the U.S. Air Force SR-71, achieve approximately Mach 3.4 and rockets from the Apollo Program achieved Mach 30+. Like a ramjet, a scramjet essentially consists of a constricted tube through which inlet air is compressed by the high speed of the vehicle, a combustion chamber where fuel is combusted, and a nozzle through which the exhaust jet leaves at higher speed than the inlet air. Also like a ramjet, there are few or no moving parts. In particular, there is no high-speed turbine, as in a turbofan or turbojet engine, that is expensive to produce and can be a major point of failure. A scramjet requires supersonic airflow through the engine, thus, similar to a ramjet, scramjets have a minimum functional speed. This speed is uncertain due to the low number of working scramjets, relative youth of the field, and the largely classified nature of research using complete scramjet engines. However, it is likely to be at least Mach 5 for a pure scramjet, with higher Mach numbers (between 7 and 9) more likely. Thus scramjets require acceleration to hypersonic speed via other means. A hybrid ramjet/scramjet would have a lower minimum functional Mach number, and some sources indicate the NASA X-43A research vehicle is a hybrid design. Recent tests of prototypes have used a booster rocket to obtain the necessary velocity. Air breathing engines should have significantly better specific impulse while within the atmosphere than rocket engines. However, scramjets have weight and complexity issues that must be considered. While very short suborbital scramjet test flights have been successfully performed, perhaps significantly no flown scramjet has ever been successfully designed to survive a flight test. The viability of scramjet vehicles is hotly contested in aerospace and space vehicle circles, in part because many of the parameters which would eventually define the efficiency of such a vehicle remain uncertain. This has led to grandiose claims from both sides, which have been intensified by the large amount of funding involved in any hypersonic testing. Some notable aerospace gurus such as Henry Spencer and Jim Oberg have gone so far as calling orbital scramjets 'the hardest way to reach orbit', or even 'scamjets' due to the extreme technical challenges involved. Major, well funded projects, like the X-30 were cancelled before producing any working hardware

    22. SPATER Axial turbine blade cooling


    24. SPATER INTERNAL BALLISTICS Internal ballistics is what happens inside a weapon when it is fired. The firing pin makes a distinct mark on the cartridge. Then explosive pressure causes the bullet to expand slightly to fill the spiral 'rifling' grooves cut in the bore. This makes the bullet spin as it passes down the barrel, but it leaves tell-tale marks on the bullet that are unique to that particular firearm. The presence of rust or spider silk indicates the gun has not been fired recently. At close range, particles from a wound may lodge inside the barrel. External ballistics is what happens to the bullet and residues outside the gun, including the direction and velocity of the shot, as well as any deviation in the trajectory. Terminal ballistics looks at the changes in trajectory and speed caused by ricochet and penetration of objects, as well as the layered deposits on parts of the bullet accumulated as it contacts these objects. Terminal ballistics includes examination of the shape of wounds and the extent of tissue damage. If a bullet cannot be removed for examination, its calibre can be measured by CT scanning.




    28. SPATER ADVANTAGES OF SOLID ROCKET MOTOR Advantages/Disadvantages Solid fueled rockets are relatively simple rockets. This is their chief advantage, but it also has its drawbacks. Once a solid rocket is ignited it will consume the entirety of its fuel, without any option for shutoff or thrust adjustment. The Saturn V moon rocket used nearly 8 million pounds of thrust that would not have been feasible with the use of solid propellant, requiring a high specific impulse liquid propellant. The danger involved in the premixed fuels of monopropellant rockets i.e. sometimes nitroglycerin is an ingredient.


    30. SPATER A simple solid rocket motor consists of a casing, nozzle, grain (propellant charge), and igniter. The grain behaves like a solid mass, burning in a predictable fashion and producing exhaust gases. The nozzle dimensions are calculated to maintain a design chamber pressure, while producing thrust from the exhaust gases. Once ignited, a simple solid rocket motor cannot be shut off, because it contains all the ingredients necessary for combustion within the chamber that they are burned in. More advanced solid rocket motors can not only be throttled but can be extinguished and then re-ignited by controlling the nozzle geometry or through the use of vent ports. Also, pulsed rocket motors which burn in segments and which can be ignited upon command are available. Modern designs may also include a steerable nozzle for guidance, avionics, recovery hardware (parachutes), self-destruct mechanisms, APUs, controllable tactical motors, controllable divert and attitude control motors and thermal management materials

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    33. SPATER Thrust is the force which moves a rocket through the air. Thrust is generated by the rocket engine through the reaction of accelerating a mass of gas. The gas is accelerated to the the rear and the rocket is accelerated in the opposite direction. To accelerate the gas, we need some kind of propulsion system. We will discuss the details of various propulsion systems on some other pages. For right now, let us just think of the propulsion system as some machine which accelerates a gas. From Newton's second law of motion, we can define a force to be the change in momentum of an object with a change in time. Momentum is the object's mass times the velocity. When dealing with a gas, the basic thrust equation is given as: F = mdot e * Ve - mdot 0 * V0 + (pe - p0) * Ae Thrust F is equal to the exit mass flow rate mdot e times the exit velocity Ve minus the free stream mass flow rate mdot 0 times the free stream velocity V0 plus the pressure difference across the engine pe - p0 times the engine area Ae. For liquid or solid rocket engines, the propellants, fuel and oxidizer, are carried on board. There is no free stream air brought into the propulsion system, so the thrust equation simplifies to: F = mdot * Ve + (pe - p0) * Ae where we have dropped the exit designation on the mass flow rate. Using algebra, let us divide by mdot: F / modt = Ve + (pe - p0) * Ae / mdot We define a new velocity called the equivalent velocity Veq to be the velocity on the right hand side of the above equation: Veq = Ve + (pe - p0) * Ae / mdot Then the rocket thrust equation becomes: F = mdot * Veq The total impulse (I) of a rocket is defined as the average thrust times the total time of firing. On the slide we show the total time as "delta t". (delta is the Greek symbol that looks like a triangle): I = F * delta t Since the thrust may change with time, we can also define an integral equation for the total impulse. Using the symbol (Sdt) for the integral, we have: I = S F dt Substituting the equation for thrust given above: I = S (mdot * Veq) dt Remember that mdot is the mass flow rate; it is the amount of exhaust mass per time that comes out of the rocket. Assuming the equivalent velocity remains constant with time, we can integrate the equation to get: I = m * Veq where m is the total mass of the propellant. We can divide this equation by the weight of the propellants to define the specific impulse. The word "specific" just means "divided by weight". The specific impulse Isp is given by: Isp = Veq / g0 where g0 is the gravitational acceleration constant (32.2 ft/sec^2 in English units, 9.8 m/sec^2 in metric units). Now, if we substitute for the equivalent velocity in terms of the thrust: Isp = F / (mdot * g0) Mathematically, the Isp is a ratio of the thrust produced to the weight flow of the propellants. A quick check of the units for Isp shows that: Isp = m/sec / m/sec^2 = sec

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    35. SPATER A bipropellant rocket engine is a rocket engine that uses two propellants (very often liquid propellants) which are kept separately prior to reacting to form a hot gas to be used for propulsion. In contrast, most solid rockets have single solid propellant, and hybrid rockets use a solid propellant lining the combustion chamber that reacts with an injected fluid. Because liquid bipropellant systems permit precise mixture control, they are often more efficient than solid or hybrid rockets, but are normally more complex and expensive, particularly when turbopumps are used to pump the propellants into the chamber to save weight

    36. SPATER Liquid propellant Thousands of combinations of fuels and oxidizers have been tried over the years. Some of the more common and practical ones are: liquid oxygen (LOX, O2) and liquid hydrogen (LH2, H2) - Space Shuttle main engines, Ariane 5 main stage and the Ariane 5 ECA second stage, the first stage of the Delta IV, the upper stages of the Saturn V, Saturn IB, and Saturn I as well as Centaur rocket stage liquid oxygen (LOX) and kerosene or RP-1 - Saturn V, Zenit rocket, R-7 Semyorka family of Soviet boosters which includes Soyuz, Delta, Saturn I, and Saturn IB first stages, Titan I and Atlas rockets liquid oxygen (LOX) and alcohol (ethanol, C2H5OH) - early liquid fueled rockets, like German (World War II) A-4, aka V-2, and Redstone liquid oxygen (LOX) and gasoline - Robert Goddard's first liquid-fuel rocket T-Stoff (80% hydrogen peroxide, H2O2 as the oxidizer) and C-Stoff (methanol, CH3OH, and hydrazine hydrate, N2H4n(H2O as the fuel) - Walter Werke HWK 109-509 engine used on Messerschmitt Me 163B Komet a rocket fighterplane of (World War II) nitric acid (HNO3) and kerosene - Soviet Scud-A, aka SS-1 inhibited red fuming nitric acid (IRFNA, HNO3 + N2O4) and unsymmetric dimethyl hydrazine (UDMH, (CH3)2N2H2) Soviet Scud-B,-C,-D, aka SS-1-c,-d,-e nitric acid 73% with dinitrogen tetroxide 27% (=AK27) and kerosene/gasoline mixture - various Russian (USSR) cold-war ballistic missiles, Iran: Shahab-5, North Korea: Taepodong-2 hydrogen peroxide and kerosene - UK (1970s) Black Arrow, USA Development (or study): hydrazine (N2H4) and red fuming nitric acid - Nike Ajax Antiaircraft Rocket Aerozine 50 and dinitrogen tetroxide - Titans 24, Apollo lunar module, Apollo service module, interplanatary probes (Such as Voyager 1 and Voyager 2) Unsymmetric dimethylhydrazine (UDMH) and dinitrogen tetroxide - Proton rocket and various Soviet rockets monomethylhydrazine (MMH, (CH3)HN2H2) and dinitrogen tetroxide - Space Shuttle Orbital maneuvering system (OMS) engines Robert Goddard and his rocket One of the most efficient mixtures, oxygen and hydrogen, suffers from the extremely low temperatures required for storing hydrogen and oxygen as liquids (around 20 K or -253 C)) and low fuel density (70 kg/m), necessitating large and heavy tanks. The use of lightweight foam to insulate the cryogenic tanks caused problems for the Space Shuttle Columbia's STS-107 mission, as a piece broke loose, damaged its wing and caused it to break up and be destroyed on reentry. For storable ICBMs and interplanetary spacecraft, storing cryogenic propellants over extended periods is awkward and expensive. Because of this, mixtures of hydrazine and its derivatives in combination with nitrogen oxides are generally used for such rockets. Hydrazine has its own disadvantages, being a very caustic and volatile chemical as well as being toxic. Consequently, hybrid rockets have recently been the vehicle of choice for low-budget private and academic developments in aerospace technology


    38. SPATER Chemical rocket engines, like those on the space shuttle, work by burning two gases to create heat, which causes the gases to expand and exit the engine through a nozzle. In so doing they create the thrust that lifts the shuttle into orbit. Smaller chemical engines are used to change orbits or to keep satellites in a particular orbit. For getting to very distant parts of the solar system chemical engines have the drawback in that it takes an enormous amount of fuel to deliver the payload. Consider the Saturn V rocket that put men on the moon: 5,000,000 pounds of it's total take off weight of 6,000,000 pounds was fuel. Electric rocket engines use less fuel than chemical engines and therefore hold the potential for accomplishing missions that are impossible for chemical systems. To understand how, we have to understand a number called specific impulse.

    39. SPATER A resistojet simply uses electricity passing through a resistive conductor, something like the wires in your toaster, to heat a gas as it passes over the conductor. As the conductor heats up the gas is heated, expands, exits through a nozzle and creates thrust. In real resistojets the conductor is a coiled tube through which the propellant flows. This is done to get maximum heat transfer from the conductor to the propellant.

    40. SPATER An arcjet is simply a resistojet where instead of passing the gas through a heating coil it's passed through an electric arc. diagram of an arcjet Because arcs can achieve temperatures of 15,00 degrees C. this means the propellant gets heated to much higher temperatures (typically 3,000 degrees C.) than in resistojets and in so doing achieve higher specific impulses, anywhere from 800 sec for ammonia to 2,000 seconds for hydrogen. Arcjets tend to be higher power devices, typically 1 to 2 kilowatts, and used for higher thrust applications, like station keeping of large satellites. Several are currently in orbit.

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    42. SPATER Ion engines: Rub a balloon against your hair or shirt and then hold it near your arm, the hairs on your arm will feel tingly and be attracted to the balloon. Bring the balloon near the carpet and bits of lint will be pulled to it. What's happening is that electrons have been deposited onto or removed from the balloon depending on what it was rubbed against, giving it an electrostatic charge, which creates an electrostatic field. A similar field can be used to produce thrust in a rocket engine called an ion thruster. ion engine diagram As propellant enters the ionization chamber (the small ns on the left), electrons (small -s in the middle) emitted from the central hot cathode and attracted to the outer anode collide with them knocking an electron off and causing the atoms of the propellant to become ionized (+s on the right). This means that they have an electric field around them like the balloon. As these ions drift between two screens at the right hand side of the ionization chamber, the strong electric field of the "+" side repels them and the "-" side attracts them, accelerating them to very high velocities. The ions leave the engine and since the engine pushes on them to accelerate them, they in turn push back against the engine creating thrust. Ion thrusters typically use Xenon (A very heavy, inert gas) for propellant, have specific impulses in the 3,000 to 6,000 range and efficiencies up to 60 percent. An average thruster is one to two feet in diameter, produces thrust on the order of small fractions of a pound and weighs some tens of pounds.

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    44. SPATER Nuclear rocket motor

    45. SPATER In a nuclear thermal rocket a working fluid, usually hydrogen, is heated to a high temperature in a nuclear reactor, and then expands through a rocket nozzle to create thrust. The nuclear reactor's energy replaces the chemical energy of the reactive chemicals in a traditional rocket engine. Due to the higher energy density of the nuclear fuel compared to chemical ones, about 107 times, the resulting efficiency of the engine is at least twice as good as chemical engines even considering the weight of the reactor, and even higher for advanced designs.

    46. SPATER Risk in nuclear rocket motor There is an inherent possibility of atmospheric or orbital rocket failure which could result in a dispersal of radioactive material, and resulting fallout. Catastrophic failure, meaning the release of radioactive material into the environment, would be the result of a containment breach. A containment breach could be the result of an impact with orbital debris, material failure due to uncontrolled fission, material imperfections or fatigue and human design flaws. A release of radioactive material while in flight could disperse radioactive debris over the Earth in a wide and unpredictable area. The zone of contamination and its concentration would be dependent on prevailing weather conditions and orbital parameters at the time of re-entry. However given that oxide reactor elements are designed to withstand high temperatures (up to 3500 K) and high pressures (up to 200 atm normal operating pressures) it's highly unlikely a reactor's fuel elements would be reduced to powder and spread over a wide-area. More likely highly radioactive fuel elements would be dispersed intact over a much smaller area, and although individually quite lethal up-close, the overall hazard from the elements would be confined to near the launch site and would be much lower than the many open-air nuclear weapons tests of the 1950s.

    47. SPATER Solar sail

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    49. SPATER The spacecraft arranges a large membrane mirror which reflects light from the Sun or some other source. The radiation pressure on the mirror provides a small amount of thrust by reflecting photons. Tilting the reflective sail at an angle from the Sun produces thrust at an angle normal to the sail. In most designs, steering would be done with auxiliary vanes, acting as small solar sails to change the attitude of the large solar sail. The vanes would be adjusted by electric motors.

    50. SPATER Limitation of solar sail Solar sails don't work well, if at all, in low Earth orbit below about 800km altitude due to erosion or air drag. Above that altitude they give very small accelerations that take months to build up to useful speeds. Solar sails have to be physically large, and payload size is often small. Deploying solar sails is also highly challenging to date. Solar sails must face the sun to decelerate. Therefore, on trips away from the sun, they must arrange to loop behind the outer planet, and decelerate into the sunlight. There is a common misunderstanding that solar sails cannot go towards their light source. This is false. In particular, sails can go toward the sun by thrusting against their orbital motion. This reduces the energy of their orbit, spiraling the sail toward the sun