- Regenerative cooling (rocket)
Regenerative cooling in
rockets is where some or all of the propellantis passed through tubes, channels or otherwise in a jacket around the combustion chamberor nozzle to cool the engine because the fuel in particular and sometimes the oxidiser are good coolants. The heated propellant is then fed into a special gas generator or injected directly into the main combustion chamber for combustion there.
1857 - Siemens introduced the Regenerative cooling concept. On 10 May 1898,
James Dewarused regenerative cooling to become the first to statically liquefy hydrogen [ [http://history.nasa.gov/SP-4404/app-a1.htm Hydrogen through the Nineteenth Century] ] .The concept of regenerative cooling was also mentioned in 1903 in an article by Konstantin Tsiolkovsky. Robert Goddardbuilt the first regeneratively cooled engine in 1923, but rejected the scheme as too complex. A regeneratively cooled engine was built by the Italian researcher, Gaetano Arturo Croccoin 1930. The first Russian engines to employ the technique were Fridrikh Tsander's OR-2 tested in March 1933 and the ORM-50, bench tested in November of 1933 by Valentin Glushko. The first German engine of this type was also tested in March of 1933 by Klaus Riedel in the VfR. The Austrian scientist Eugen Sängerwas particularly famous for experiments with engine cooling starting in 1933; however, most of his experimental engines were water cooled or cooled by an extra circuit of propellant.
V-2rocket engine, the most powerful of its time at 25 tons (245 kN) of thrust, was regeneratively cooled by fuel lines coiled around the outside of the combustion chamber. This was an inefficient design that required the burning of diluted alcohol at low chamber pressure to avoid melting the engine. The American Redstone engine used the same design.
A key innovation in regenerative cooling was the Russian U-1250 engine designed by
Aleksei Mihailovich Isaevin 1945. Its combustion chamber was lined by a thin copper sheet supported by the corrugated steel wall of the chamber. Fuel flowed through the corrugations and absorbed heat very efficiently. This permitted more energetic fuels and higher chamber pressures, and it is the basic plan used in all Russian engines since. Modern American engines solve this problem by lining the combustion chamber with brazed copper or nickel alloy tubes (although recent engines like in the Boeing Delta IVhave started to use the Russian technique which is cheaper to construct). The American style of lining the engine with copper tubes is called the "spaghetti construction", and the concept is credited to Edward A. Neu at Reaction MotorsInc. in 1947.
Heat flow and temperature
The heat flow through the chamber wall is very high indeed, 1-20 MW/m2 is not uncommon.
The amount of heat that can flow into the coolant is controlled by many factors including the temperature difference between the chamber and the coolant, the
heat transfer coefficient, the thermal conductivityof the chamber wall, the velocity in the coolant channels and the velocity of the gas flow in the chamber or the nozzle.
boundary layers form; one in the hot gas in the chamber and the other in the coolant within the channels.
Very typically most of the temperature drop occurs in the gas boundary layer since gases are relatively poor conductors. This boundary layer can be destroyed however by combustion instabilities, and wall failure can follow very soon afterwards.
The boundary layer within the coolant channels can also be disrupted if the coolant is at subcritical pressure and film boils; the gas then forms an insulating layer and the wall temperature climbs very rapidly and soon fails. However, if the coolant engages in nucleate boiling but does not form a film, this helps disrupt the coolant boundary layer and the gas bubbles formed rapidly collapse; this can triple the maximum heat flow. However, many modern engines with turbopumps use supercritical coolants, and these techniques can be seldom used.
Regenerative cooling is seldom used in isolation,
film cooling[ [http://www.me.umn.edu/labs/tcht/measurements/what.html film cooling] ] , curtain cooling[ [http://sci.tech-archive.net/Archive/sci.space.tech/2005-01/0059.html curtain cooling] ] , transpiration cooling, radiation coolingand ablative liners [ [http://www.engineeringatboeing.com/articles/heart.htm radiation cooling] ] are very frequently employed as well.
With regenerative cooling, the pressure in the cooling channels is significantly above the chamber pressure hence the inner liner is under compression, while the outer wall of the engine is under significant hoop stresses.
The metal of the inner liner is greatly weakened by the high temperature, and also undergoes significant thermal expansion at the inner surface while the cold-side wall of the liner constrains the expansion. This sets up significant thermal stresses that can cause the inner surface to crack or craze after multiple firings particularly at the throat.
In addition the thin inner liner requires mechanical support to withstand the compressive loading due to the propellant's pressure, this support is usually provided by the side walls of the cooling channels and the backing plate.
The inner liner is usually constructed of relatively high temperature, high thermal conductivity materials, traditionally copper or nickel based alloys have been used.
Wikimedia Foundation. 2010.
См. также в других словарях:
Regenerative cooling — is a method of cooling gases in which compressed gas is cooled by allowing it to expand and and thereby taking heat from the surroundings, the cooled expanded gas then passes through a heat exchanger where it cools the incoming compressed gas.… … Wikipedia
regenerative cooling — /rəˌdʒɛnərətɪv ˈkulɪŋ/ (say ruh.jenuhruhtiv koohling) noun 1. Aeronautics the cooling of a rocket combustion chamber wall by the circulation of a propellant before its injection into the chamber. 2. Chemistry the cooling of a gas by allowing a… … Australian-English dictionary
Rocket engine — RS 68 being tested at NASA s Stennis Space Center. The nearly transparent exhaust is due to this engine s exhaust being mostly superheated steam (water vapor from its propellants, hydrogen and oxygen) … Wikipedia
Rocket — This article is about vehicles powered by rocket engines. For other uses, see Rocket (disambiguation). A Soyuz U, at Baikonur Site 1/5 A rocket is a missile, spacecraft, aircraft or other vehicle which obtains thrust from a rocket engi … Wikipedia
regenerative motor — noun : a jet or rocket motor in which the incoming combustion air is heated by passage through the motor cooling jacket … Useful english dictionary
Liquid rocket — A liquid rocket is a rocket with an engine that uses propellants in liquid form. Liquids are desirable because their reasonably high density allows the volume and hence the mass of the tanks to be relatively low, resulting in a high mass ratio.… … Wikipedia
Staged combustion cycle (rocket) — Staged combustion rocket cycle. Usually, all of the fuel and a portion of the oxidizer are fed through the pre burner (fuel rich) to power the pumps. An oxygen rich circuit is possible also, but less common because of the metallurgy required. The … Wikipedia
Multistage rocket — First stage and second stage redirect here. For other uses, see diving regulator and reading (legislature). The second stage of a Minuteman III rocket A multistage (or multi stage) rocket is a rocket that uses two or more stages, each of… … Wikipedia
V-2 rocket — ] Technical detailsAt launch the A 4 propelled itself for up to 65 seconds on its own power, and a program motor controlled the pitch to the specified angle at engine shutdown, from which the rocket continued on a free fall () trajectory. The… … Wikipedia
Vulcain (rocket engine) — Vulcain is a family of European cryogenic first stage rocket engines for the Ariane 5.HistoryThe development of Vulcain, assured by a European collaboration, began in 1988 with the Ariane 5 rocket program. [cite web url =… … Wikipedia