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35-420: Direct cycle nuclear engines resemble a conventional jet engine without combustion chambers . The air gained from the compressor section is sent to a plenum that directs the air into the nuclear reactor core . An exchange takes place where the reactor is cooled, but it then heats up the same air and sends it to another plenum. The second plenum directs the air through a turbine (powering the compressor), then out

70-412: A MSR concept, the program was canceled by President Kennedy on March 26, 1961 citing the high cost with no flight-worthy reactor having been produced up to that point – "15 years and about $ 1 billion have been devoted to the attempted development of a nuclear-powered aircraft; but the possibility of achieving a militarily useful aircraft in the foreseeable future is still very remote". Also contributing to

105-538: A civilian power station concept. The result of the proposal was direction from the Atomic Energy Commission for ORNL to design, construct, and operate the Molten-Salt Reactor Experiment (MSRE). Combustion chamber A combustion chamber is part of an internal combustion engine in which the fuel/air mix is burned. For steam engines, the term has also been used for an extension of

140-458: A lower grade of fuel. Harry Ricardo was prominent in developing combustion chambers for diesel engines, the best known being the Ricardo Comet . In a continuous flow system, for example a jet engine combustor , the pressure is controlled and the combustion creates an increase in volume. The combustion chamber in gas turbines and jet engines (including ramjets and scramjets ) is called

175-414: Is squish , where the fuel/air mix is "squished" at high pressure by the rising piston. The location of the spark plug is also an important factor, since this is the starting point of the flame front (the leading edge of the burning gasses) which then travels downwards towards the piston. Good design should avoid narrow crevices where stagnant "end gas" can become trapped, reducing the power output of

210-515: Is large steam locomotive engines, allows the use of shorter firetubes . Micro combustion chambers are the devices in which combustion happens at a very small volume, due to which surface to volume ratio increases which plays a vital role in stabilizing the flame. General Electric J47 The General Electric J47 turbojet (GE company designation TG-190) was developed by General Electric from its earlier J35 . It first flew in May 1948. The J47

245-488: Is located below it. The shape of the combustion chamber, intake ports and exhaust ports are key to achieving efficient combustion and maximising power output. Cylinder heads are often designed to achieve a certain "swirl" pattern (rotational component to the gas flow) and turbulence , which improves the mixing and increases the flow rate of gasses. The shape of the piston top also affects the amount of swirl. Another design feature to promote turbulence for good fuel/air mixing

280-617: The Lockland facility (renamed to the Evendale facility) utilized vertical engine assembly to ensure compressor rotor balance and stability. The technological jump provided by the engine led to it becoming the most produced jet engine in aviation history, and established GE Aviation as a worldwide leader in jet propulsion. Overhaul life for the J47 ranged from 15 hours (in 1948) to a theoretical 1,200 hours (625 achievable in practice) in 1956. For example,

315-617: The X211 . The design based on the J47 became the X39 program. This system consisted of two modified J47 engines which, instead of combusting jet fuel, received their heated, compressed air from a heat exchanger that was part of the Heat Transfer Reactor Experiment (HTRE) reactor. The X-39 was successfully operated in conjunction with three different reactors, the HTRE-1, HTRE-2 and HTRE-3. Had

350-465: The combustor . The combustor is fed with high pressure air by the compression system, adds fuel and burns the mix and feeds the hot, high pressure exhaust into the turbine components of the engine or out the exhaust nozzle. Different types of combustors exist, mainly: If the gas velocity changes, thrust is produced, such as in the nozzle of a rocket engine . Considering the definition of combustion chamber used for internal combustion engines,

385-601: The compressor , allowing fighter jets equipped with the engine to function at high altitudes, and in cold conditions such as the top of Mount Washington in New Hampshire's White Mountains , where the engine was first tested. The engine featured an electronically controlled afterburner , a system that dumped additional fuel into the combustor pipe 'behind' the engine, reheating the exhaust and producing significantly more thrust, although with greatly reduced efficiency and high fuel burn rates. The engine production process in

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420-437: The firebox which is used to allow a more complete combustion process. In an internal combustion engine , the pressure caused by the burning air/fuel mixture applies direct force to part of the engine (e.g. for a piston engine, the force is applied to the top of the piston), which converts the gas pressure into mechanical energy (often in the form of a rotating output shaft). This contrasts an external combustion engine, where

455-402: The hemi , pent-roof , wedge or kidney-shaped chambers). The older flathead engine design uses a "bathtub"-shaped combustion chamber, with an elongated shape that sits above both the piston and the valves (which are located beside the piston). IOE engines combine elements of overhead valve and flathead engines; the intake valve is located above the combustion chamber, while the exhaust valve

490-658: The Air National Guard retired the jet-boosted KC-97Js. Despite this, these engines are still extensively utilized in F-86 Sabre jets owned by civilians, making them a common sight at air shows. The J47 design used experience from the TG-180/J35 engine which was described by Flight magazine in 1948 as the most widely used American-conceived turbojet. The turbojet featured a revolutionary anti-icing system where hollow frame struts allowed heated airflow to pass through from

525-530: The J47-GE-23 was rated to run 225 hours time between overhauls . As installed on the F-86F, it experienced one in-flight shutdown every 33,000 hours in 1955 and 1956. Ground-based vehicles that used the engine include: In the 1950s, interest in the development of nuclear-powered aircraft led GE to experiment with two nuclear-powered gas turbine designs, one based on the J47, and another new and much larger engine called

560-520: The cancellation was that the first intercontinental ballistic missiles entered into active service in September 1959 which all but eliminated the need for a nuclear-powered aircraft as a strategic deterrent. Nevertheless, the results of the ARE program prompted scientists and engineers at ORNL to submit a preliminary design proposal to the Atomic Energy Commission for a 30 MW th experimental MSR to explore MSR as

595-509: The circulating-fuel reactor program of the Pratt and Whitney Aircraft Company (PWAC). This was called the PWAR-1, the Pratt and Whitney Aircraft Reactor-1. The purpose of the experiment was to experimentally verify the theoretically predicted nuclear properties of a PWAC reactor. The experiment was only run briefly; by the end of February 1957 all data had been taken and disassembly had begun. The experiment

630-454: The combustion takes place in a separate part of the engine to where the gas pressure is converted into mechanical energy. In spark ignition engines, such as petrol (gasoline) engines , the combustion chamber is usually located in the cylinder head . The engines are often designed such that the bottom of combustion chamber is roughly in line with the top of the engine block . Modern engines with overhead valves or overhead camshaft(s) use

665-411: The compressed air run through the reactor to be heated by it before being exhausted through the turbine. Indirect cycling involves thermal exchange outside of the core with compressor air being sent to a heat exchanger . The nuclear reactor core would heat up pressurized water or liquid metal and send it to the heat exchanger as well. That hot liquid would be cooled by the air; the air would be heated by

700-450: The engine and potentially leading to engine knocking . Most engines use a single spark plug per cylinder, however some (such as the 1986-2009 Alfa Romeo Twin Spark engine ) use two spark plugs per cylinder. Compression-ignition engines, such as diesel engines , are typically classified as either: Direct injection engines usually give better fuel economy but indirect injection engines can use

735-457: The equivalent part of a steam engine would be the firebox , since this is where the fuel is burned. However, in the context of a steam engine, the term "combustion chamber" has also been used for a specific area between the firebox and the boiler . This extension of the firebox is designed to allow a more complete combustion of the fuel, improving fuel efficiency and reducing build-up of soot and scale. The use of this type of combustion chamber

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770-399: The exhaust, providing thrust. The end result is that instead of using jet fuel, an aircraft could rely on the heat from nuclear reactions for power. The General Electric program, which was based at Evendale, Ohio , was pursued because of its advantages in simplicity, reliability, suitability and quick start ability. Conventional jet engine compressor and turbine sections were used, with

805-632: The launch of Sputnik 1 ), and continued strong support from the Air Force allowed the program to continue, despite divided leadership between the DOD and the AEC. Numerous test facilities were funded and constructed through the 1950s and 1960–61 in order to produce a flight-worthy nuclear power unit, including one at the Oak Ridge National Laboratory (ORNL). While the ARE successfully demonstrated operation of

840-699: The liquid, sent through a turbine (powering the compressor), then out the exhaust, providing thrust. The Indirect Air Cycle program was assigned to Pratt & Whitney, at a facility near Middletown, Connecticut . This concept would have produced far less radioactive pollution. One or two loops of liquid metal would carry the heat from the reactor to the engine. This program involved a great deal of research and development of many light-weight systems suitable for use in aircraft, such as heat exchangers, liquid-metal turbopumps and radiators . The Indirect Cycle program never came anywhere near producing flight-ready hardware. The United States Aircraft Reactor Experiment (ARE)

875-582: The results of the NTA, the X-6 and the entire nuclear aircraft program was abandoned in 1961. As part of the AEC/USAF ANP program, in 1956 modified General Electric J47s were first operated on nuclear power using a reactor test assembly known as Heat Transfer Reactor Experiment 1 (HTRE-1). HTRE-1, which used vertically-oriented control rods, was reconfigured with a removable core to become HTRE-2 for additional testing. HTRE-3

910-464: The top of the piston (when it is near top dead centre ) as the bottom of the combustion chamber. Above this, the sides and roof of the combustion chamber include the intake valves, exhaust valves and spark plug. This forms a relatively compact combustion chamber without any protrusions to the side (i.e. all of the chamber is located directly above the piston). Common shapes for the combustion chamber are typically similar to one or more half-spheres (such as

945-440: Was a 2.5 MW th thermal -spectrum nuclear reactor experiment designed to attain a high power density and high output temperature for use as an engine in a nuclear-powered bomber aircraft. The advantage of a nuclear-powered aircraft over a conventionally-powered aircraft is that it could remain airborne orders of magnitude longer and provide an effective nuclear strategic deterrent to a nuclear-armed Soviet adversary. The ARE

980-408: Was advertised as an 'all-weather engine' due to its anti-icing systems which allowed it to perform at high altitudes and extreme temperatures where other aircraft's performance suffered. Its development began without an explicit need for it, although this design was quickly purchased by the military for its many potential benefits. In 1978, J47s were formally withdrawn from active military duty when

1015-645: Was built separately to test horizontally-oriented control rods as appropriate for use in an airframe. The decommissioned HTRE-2 and HTRE-3 reactors and test assemblies can be viewed by the public in the Experimental Breeder Reactor I parking lot at Idaho National Laboratory . On February 5, 1957, another reactor was made critical at the Critical Experiments Facility of the Oak Ridge National Laboratory (ORNL) as part of

1050-401: Was circulated around the primary coolant to transfer heat to a water radiator where heat output was dumped to atmosphere. Reactivity control rods were installed and it was found that the control rods did not determine the output power of the ARE; rather, the power demand did, which affected the outlet and inlet temperatures because of the negative temperature coefficient of reactivity . The ARE

1085-548: Was operated at power for 221 hours up to a peak of 2.5 MW th . On September 5, 1951, the USAF awarded Convair a contract to fly a nuclear reactor on board a modified Convair B-36 Peacemaker under the MX-1589 project of the ANP program. The NB-36H Nuclear Test Aircraft (NTA) was to study shielding requirements for an airborne reactor, to determine whether a nuclear aircraft was feasible. This

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1120-529: Was run at essentially zero nuclear power. The operating temperature was held constant at approximately 675 °C (1,247 °F), which corresponds closely to the design operating temperature of the PWAR-l moderator; this temperature was maintained by external heaters. Like the 2.5 MWt ARE, the PWAR-1 used NaF-ZrF4-UF4 as the primary fuel and coolant. Technological competition with the Soviet Union (as represented by

1155-544: Was the first axial-flow turbojet approved for commercial use in the United States. It was used in many types of aircraft, and more than 30,000 were manufactured before production ceased in 1956. It saw continued service in the US military until 1978. Packard built 3,025 of the engines under license. The J47's greatest advantage, as advertised, was its array of features which were unavailable and unprecedented in any other engine. It

1190-412: Was the first molten salt reactor (MSR) to be built and operated. It used the molten fluoride salt NaF - ZrF 4 - UF 4 (53-41-6 mol%) as fuel , was moderated by a hexagonal-configuration beryllium oxide (BeO), and had a peak temperature of 860 °C. A redundant liquid sodium coolant system was used to cool the moderator and reflector materials. A secondary helium gas coolant loop

1225-477: Was the only known airborne reactor experiment by the U.S. with an operational nuclear reactor on board. The NTA flew a total of 47 times testing the reactor over West Texas and Southern New Mexico. The reactor, named the Aircraft Shield Test Reactor (ASTR), was operational but did not power the aircraft; the primary purpose of the flight program was testing the effectiveness of the shielding. Based on

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