1.CRYOGENIC ROCKET ENGINE1Presented By: Sushil LambaMechanical IDD Part IV,Sem VII 10406EN008

2. CONTENTS INTRODUCTIONHISTORY OF CRYOGENIC TECHNOLOGYCONSTRUCTIONROCKET ENGINE POWER CYCLESCOMBUSTION IN THRUST CHAMBERADVANTAGESDISVANTAGES2 3. INTRODUCTION3Cryogenics originated from two Greek words kyros which means cold or freezing and genes which means born or produced.Cryogenics is the study of very low temperatures or the production of the same. Liquefied gases like liquid nitrogen and liquid oxygen are used in many cryogenic applications.A cryogenic rocket engine is a rocket engine that uses a cryogenic fuel or oxidizer, that is, its fuel or oxidizer(or both) are gases liquefied and stored at very low temperatures.Oxygen remains a liquid only at temperatures below minus 183 Celsius and hydrogen at below minus 253 Celsius.Notably, these engines were one of the main factors of the ultimate success in reaching the Moon by the Saturn V rocket. 4. History of Cryogenic Technology The United States was the first country to develop cryogenic rocket engines with RL-10 engines, registered its first successful flight in 1963 and is still used on the Atlas V rocket.Then The Japanese LE-5 engine flew in 1977 ,French HM-7 in 1979 , Chinese YF-73 in 1984 .The Soviet Union, first country to put a satellite and later a human in space, successfully launched a rocket with acryogenic engine only in 1987.4 5. CONSTRUCTION The major components of a cryogenic rocket engine are the combustion chamber (thrust chamber), pyrotechnic igniter, fuel injector, fuel cryopumps, oxidizer cryopumps, gas turbine, cryovalves, regulators, the fuel tanks, and rocket engine nozzle.In terms of feeding propellants to combustion chamber, cryogenic rocket engines (or, generally, all liquidpropellant engines) work in either an expander cycle, a gas-generator cycle, a staged combustion cycle, or the simplest pressure-fed cycle.The cryopumps are always turbo-pumps powered by a flow of fuel through gas turbines . Looking at this aspect , engines can be differentiated into a main flow or a bypass flow configuration.In the main flow design, all the pumped fuel is fed through the gas turbines, and in the end injected to the combustion chamber. In the bypass configuration, the fuel flow is split; the main part goes directly to the combustion chamber to generate thrust, while only a small amount of the fuel goes to the turbine.5 6. 6 7. ROCKET ENGINE POWER CYCLES Gas pressure feed system:-A pressurized feed system consists of a highpressure gas tank, a gas starting valve, a pressure regulator, propellant tanks, propellant valves, and feed lines.Additional components, such as filling and draining provisions, check valves, filters, flexible elastic bladders for separating the liquid from the pressurizing gas, and pressure sensors or gauges, are also often incorporated.After all tanks are filled, the high-pressure gas valve is remotely actuated and admits gas through the pressure regulator at a constant pressure to the propellant tanks.The check valves prevent mixing of the oxidizer with the fuel when the unit is not in an right position.7 8. Continued. The propellants are fed to the thrust chamber by opening valves. When the propellants are completely consumed , the pressurizing gas can also scavenge and clean lines and valves of much of the liquid propellant residue. The variations in this system ,such as the combination of several valves into one or the elimination and addition of certain ,depend to a large extent on the application. If a unit is to be used over and over, such as spacemaneuver rocket,it will include several additional features such as,possibly, a thrust-regulating device and a tank level gauge.8 9. Gas-Generator Cycle The gas-generator cycle taps off a small of fuel and oxidizer from the main flow to feed a burner called a gas generator.The hot gas from this generator passes through a turbine to generate power for the pumps that send propellants to the combustion chamber.The hot gas is then either dumped overboard or sent into the main nozzle downstream.Increasing the flow of propellants into the gas generator increases the speed of the turbine, which increases the flow of propellants into the main combustion chamber (and hence, the amount of thrust produced).The gas generator must burn propellants at a lessthan-optimal mixture ratio to keep the temperature low for the turbine blades.Thus, the cycle is appropriate for moderate power requirements but not high-power systems, which would have to divert a large portion of the main flow to the less efficient gasgenerator flow.9 10. COMBUSTION IN THRUST CHAMBER10 11. COMBUSTION IN THRUST CHAMBER The thrust chamber is the key subassembly of a rocket engine. Here the liquid propellants are metered, injected, atomized, vaporized, mixed, and burned to form hot reaction gas products, which in turn are accelerated and ejected at high velocity. A rocket thrust chamber assembly has an injector, a combustion chamber, a supersonic nozzle, and mounting provisions. All have to withstand the extreme heat of combustion and the various forces, including the transmission of the thrust force to the vehicle. There is an ignition system if non-spontaneously ignitable propellants are used.11 12. The four phases of combustion in the thrust chamber are PrimaryIgnition FlamePropagation FlameLift off FlameAnchorin12 13. Primary Ignition Begins at the time of deposition of the energy into the shear layer and ends when the flame front has reached the outer limit of the shear layer.Starts interaction with the recirculation zone.Phase typically lasts about half a millisecondIt is characterized by a slight but distinct downstream movement of the flame.The flame velocity more or less depends on the pre-mixedness of the shear layer only.13 14. Flame Propagation This phase corresponds to the time span for the flame reaching the edge of the shear layer, expands into in the recirculation zone and propagates until it has consumed all the premixed propellantsThis period lasts between 0.1 and 2 ms.It is characterized by an upstream movement of the upstream flame front until it reaches a minimum distance from the injector face plate.It is accompanied by a strong rise of the flame intensity and by a peak in the combustion chamber pressure.14 15. Flame Lift Off Phase starts when the upstream flame front begins to move downstream away from the injector because all premixed propellants in the recirculation zone have been consumed until it reaches a maximum distance.This period lasts between 1 and 5ms.The emission of the flame is less intense showing that the chemical activity has decreased.The position where the movement of the upstream flame front comes to an end, the characteristic times of convection and flame propagation are balanced.15 16. Flame Anchoring This period lasts from 20ms to more than 50ms , depending on the injection condition.It begins when the flame starts to move a second time upstream to injector face plate and ends when the flame has reached stationary conditions.During this phase the flame propagates upstream only in the shear layer.Same as flame lift-off phase the vaporization is enhanced by the hot products which are entrained into the shear layer through the recirculation zone.16 17. Advantages High Energy per unit mass: Propellants like oxygen and hydrogen in liquid form give very high amounts of energy per unit mass due to which the amount of fuel to be carried aboard the rockets decreases.Clean Fuels Hydrogen and oxygen are extremely clean fuels. When they combine, they give out only water. This water is thrown out of the nozzle in form of very hot vapour. Thus the rocket is nothing but a high burning steam engineEconomical Use of oxygen and hydrogen as fuels is very economical, as liquid oxygen costs less than gasoline.17 18. Drawbacks: Boil off RateHighly reactive gasesLeakageHydrogen Embrittlement18 19. The next generation of the Rocket Engines All rocket engines burn their fuel to generate thrust . If any other engine can generate enough thrust, that can also be used as a rocket engineThere are a lot of plans for new engines that the NASA scientists are still working with. One of them is the Xenon ion Engine. This engine accelerate ions or atomic particles to extremely high speeds to create thrust more efficiently. NASA's Deep Space-1 spacecraft will be the first to use ion engines for propulsion.There are some alternative solutions like Nuclear thermal rocket engines, Solar thermal rockets, the electric rocket etc.19 20. 20