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Liquid-Propellant Rocket Engines
Published in D.P. Mishra, Fundamentals of Rocket Propulsion, 2017
This is the most widely used cooling system for liquid-propellant rocket engine. In this case, liquid fuel/oxidizer is employed as a coolant, which is allowed to pass through the passages placed outside of the combustion chamber and nozzle, as shown in Figure 8.12a, before being fed into thrust chamber. As a result, heat is transferred to the incoming propellant from the combustion hot gases and enhances its enthalpy. Since the heat from hot gases are reused as in regenerative cycle of power plant, this kind of cooling system is known as regenerative cooling system. This method of cooling is used in several rocket engines such as Saturn vehicle and Apollo missions. Generally, in this system, array of suitably shaped tubes are brazed to the walls of the thrust chamber of liquid-propellant rocket engine that are supported by steel bands. In case of cryogenic engine, hydrogen is used as a coolant for regenerative cooling system, because the pressure of the hydrogen is much above the critical pressure of boiling and avoids boiling during regenerative cooling. As a result, liquid hydrogen is continuously converted into hydrogen gas, which can enhance heat transfer rate due to its higher thermal diffusivity.
Are All Rockets the Same?
Published in Travis S. Taylor, Introduction to Rocket Science and Engineering, 2017
Figure 5.13 shows a close-up of the SSME nozzle. Note that there are pipes running down the nozzle connecting to channels that are rings around the bell part of the nozzle. The pipes flow liquid hydrogen fuel into these rings, which are known as cooling channels. The cold liquid propellant flows around the nozzle to keep it cool for two main reasons. The simplest of the reasons is for structural integrity. The temperature and pressure inside the SSME nozzle are quite high, placing the material in a very extreme environment. Keeping the nozzle wall materials cool helps maintain the material strength. The other reason is to keep the temperature of the nozzle walls as constant as possible. Hot spots can cause the flow to be disturbed and, therefore, will make the engine less efficient. Cooling the engine this way is called regenerative cooling.
Investigating the effective stress function algorithm for the thermostructural analysis and design of liquid rocket engines thrust chambers
Published in Journal of Thermal Stresses, 2021
Thrust chambers of liquid rocket engines can work at very severe thermo-mechanical load conditions, namely at heat fluxes of 1–10 MW/m2 and pressures that can vary from 5 to 10 MPa. Regenerative cooled thrust chambers are generally adopted for applications characterized by such high values of pressure and heat flux since it represents one of the most efficient method of cooling the inner liner of the chamber, which is typically made of copper alloys. Another peculiarity of the regenerative cooling technique is that the coolant, which is also the fuel, increases its enthalpy while absorbing heat and, then, enhances the combustion efficiency. The pressure inside the cooling channel must be considerably higher than the pressure of the thrust chamber causing, then, bending of the inner liner ligament; on the other hand, compressive hoop stresses arise in the inner liner since its thermal expansion is restrained by the the external cold structure. Then, thermo-elastic-plastic and creep numerical analyses of thrust chambers are usually very challenging since they should be as accurate as possible and computationally efficient. In fact, the complexity of the design and boundary conditions considered are further complicated by the highly non-linear elastoplastic constitutive equations [1–4].