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Energy Conversions and Heat Exchanges in a Helium-Pressurized Rocket Engine System, Exercises of Applied Thermodynamics

A schematic diagram and explanation of the energy conversions and heat exchanges in a helium-pressurized, bipropellant rocket engine system for the fourth stage of the peacekeeper ballistic missile. It discusses the roles of internal, potential, kinetic, and chemical energy, as well as work and heat transfer, in the process.

Typology: Exercises

2011/2012

Uploaded on 07/22/2012

senapathy_101
senapathy_101 🇮🇳

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Below is a schematic diagram of a helium-pressurized, bipropellant rocket engine system
(for the fourth stage of the Peacekeeper ballistic missile). Describe the conversions of
energy (internal, potential, kinetic and chemical) and exchanges of heat and work for this
system and that of the rocket itself. Note at which points in the process heat is transferred
to/from the surroundings. (LO#1, LO#2, LO#3)
It is understood at this point in Unified that you have only had one or two lectures on
thermodynamics, and no propulsion and fluid mechanics lectures. So what is expected is
that you recognize conversions between various forms of energy when they occur and know
then difference between transfers of energy called “work” and transfers of energy called
“heat”.
For the gases in the system, changes in potential energy will typically be small compared to
the changes in internal energy, kinetic energy and chemical energy due to their low density.
Internal energy is stored in the high pressure helium. The helium expands, pushing against
(i.e., applying a force over a distance or doing work on) the propellants. As the helium
expands, its internal energy is reduced. Energy may also be exchanged with the
surroundings through heat transfer if the high pressure helium tank and the tubing and
valves are not thermally-insulated. The work from the helium probably does not raise the
internal energy (pressure and temperature) of the propellants very much since there is a
pressure regulator in the system, However, it does cause the propellants to move (i.e., giving
the propellants kinetic energy). The propellants flow into a combustion chamber where they
react, converting chemical energy stored in the propellants into internal energy (high
temperature and pressure) in the gases formed as products of the reaction. Here again,
energy may be exchanged with the surroundings through heat transfer depending on how
well thermally-insulated the combustion chamber and nozzle are. These high temperature
and high pressure gases are then accelerated through an exhaust nozzle (exchanging internal
energy for kinetic energy). As they pass through the exhaust nozzle they push on the walls
of the nozzle doing work on the rocket. The kinetic and/or potential energy of the rocket
increase as a result. Any energy left in the exhaust (internal and kinetic) is lost to the
atmosphere which sees a very slight increase in internal energy (e.g. temperature) as a result
of the whole process.
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Download Energy Conversions and Heat Exchanges in a Helium-Pressurized Rocket Engine System and more Exercises Applied Thermodynamics in PDF only on Docsity!

Below is a schematic diagram of a helium-pressurized, bipropellant rocket engine system (for the fourth stage of the Peacekeeper ballistic missile). Describe the conversions of energy (internal, potential, kinetic and chemical) and exchanges of heat and work for this system and that of the rocket itself. Note at which points in the process heat is transferred to/from the surroundings. (LO#1, LO#2, LO#3)

It is understood at this point in Unified that you have only had one or two lectures on thermodynamics, and no propulsion and fluid mechanics lectures. So what is expected is that you recognize conversions between various forms of energy when they occur and know then difference between transfers of energy called “work” and transfers of energy called “heat”.

For the gases in the system, changes in potential energy will typically be small compared to the changes in internal energy, kinetic energy and chemical energy due to their low density. Internal energy is stored in the high pressure helium. The helium expands, pushing against (i.e., applying a force over a distance or doing work on) the propellants. As the helium expands, its internal energy is reduced. Energy may also be exchanged with the surroundings through heat transfer if the high pressure helium tank and the tubing and valves are not thermally-insulated. The work from the helium probably does not raise the internal energy (pressure and temperature) of the propellants very much since there is a pressure regulator in the system, However, it does cause the propellants to move (i.e., giving the propellants kinetic energy). The propellants flow into a combustion chamber where they react, converting chemical energy stored in the propellants into internal energy (high temperature and pressure) in the gases formed as products of the reaction. Here again, energy may be exchanged with the surroundings through heat transfer depending on how well thermally-insulated the combustion chamber and nozzle are. These high temperature and high pressure gases are then accelerated through an exhaust nozzle (exchanging internal energy for kinetic energy). As they pass through the exhaust nozzle they push on the walls of the nozzle doing work on the rocket. The kinetic and/or potential energy of the rocket increase as a result. Any energy left in the exhaust (internal and kinetic) is lost to the atmosphere which sees a very slight increase in internal energy (e.g. temperature) as a result of the whole process.

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