The Packard XJ49 was the first U.S. designed
turbofan
The turbofan or fanjet is a type of airbreathing jet engine that is widely used in aircraft propulsion. The word "turbofan" is a portmanteau of "turbine" and "fan": the ''turbo'' portion refers to a gas turbine engine which achieves mechanic ...
aircraft engine, and was developed by the
Packard Motor Co. in the 1940s.
Design and development
In 1943,
Packard leased a government-owned manufacturing plant located on the outskirts of
Toledo, Ohio
Toledo ( ) is a city in and the county seat of Lucas County, Ohio, United States. A major Midwestern United States port city, Toledo is the fourth-most populous city in the state of Ohio, after Columbus, Cleveland, and Cincinnati, and according ...
. The plant was previously operated by the defunct Aviation Corporation. Packard used the leased plant to manufacture parts for the
Rolls-Royce Merlin
The Rolls-Royce Merlin is a British liquid-cooled V-12 piston aero engine of 27-litres (1,650 cu in) capacity. Rolls-Royce designed the engine and first ran it in 1933 as a private venture. Initially known as the PV-12, it was late ...
engine, and referred to it as its Toledo Division. In the early-summer of 1944, the
Army Air Force Materiel Command contracted with Packard to carry out "advanced aircraft engine development" on both the Merlin and gas-turbine engines. To oversee the new project, Packard hired
Allison Engine Company
The Allison Engine Company was an American aircraft engine manufacturer. Shortly after the death of James Allison in 1929 the company was purchased by the Fisher brothers. Fisher sold the company to General Motors, which owned it for most of it ...
's
Robert M. Williams as their chief design engineer at the Toledo facility in July of that year. In October 1946 Williams and Dr. George F. Wislicenus, one of the engineers working under him, discussed ways of improving the efficiency of turbojet engines. They came up with an engine design which they called a "
ducted fan
In aeronautics, a ducted fan is a thrust-generating mechanical fan or propeller mounted within a cylindrical duct or shroud. Other terms include ducted propeller or shrouded propeller. When used in vertical takeoff and landing
(VTOL) applicati ...
". The resulting engine was Packard's model PT-205, with the military designation Packard XJ49-V-1 turbofan engine.
The XJ49 design was truly a break from conventional design practices of the time. Most turbojet engines then used one
centrifugal compressor
Centrifugal compressors, sometimes called impeller compressors or radial compressors, are a sub-class of dynamic axisymmetric work-absorbing turbomachinery.
They achieve pressure rise by adding energy to the continuous flow of fluid through t ...
, one
turbine
A turbine ( or ) (from the Greek , ''tyrbē'', or Latin ''turbo'', meaning vortex) is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work. The work produced by a turbine can be used for generating ...
wheel and multiple
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 the firebox which is used to allow a more complete combustion process.
Intern ...
s that resembled long cylinders arranged in a conical pattern. The XJ49 design had a two-stage compressor made up of an
axial-flow
An axial compressor is a gas compressor that can continuously pressurize gases. It is a rotating, airfoil-based compressor in which the gas or working fluid principally flows parallel to the axis of rotation, or axially. This differs from other ...
supersonic compressor at the engine intake, driven by the second power turbine wheel, followed by a spirally-shaped mixed flow compressor, driven by the first turbine wheel, giving an overall
compression ratio of 6:1.
[Neal]
Power from the
annular
Annulus (or anulus) or annular indicates a ring- or donut-shaped area or structure. It may refer to:
Human anatomy
* '' Anulus fibrosus disci intervertebralis'', spinal structure
* Annulus of Zinn, a.k.a. annular tendon or ''anulus tendineus co ...
combustion chamber exhaust drives the complex two-stage turbine. The discharge flow from the first turbine stage drives an independent second-stage turbine. The blades of the last stage of the second turbine are extended beyond the engine core to form a
supersonic fan that provides
air flow
Airflow, or air flow, is the movement of air. The primary cause of airflow is the existence of air. Air behaves in a fluid manner, meaning particles naturally flow from areas of higher pressure to those where the pressure is lower. Atmospheric ...
around the
engine core for additional thrust and further combustion. Supplementary burning (reheat or afterburning) between the two turbines and in the tailpipe can also be used for additional thrust.
The period between drawing up the basic design theory and having a complete engine ready to make its first run on a test stand was unusually short, as Packard started testing the first (and only) XJ49 in November 1948. When the testing was complete, the XJ49 proved itself to be the most powerful jet engine in operation at the time.
Survivors
On September 16, 1959, the
United States Air Force
The United States Air Force (USAF) is the Aerial warfare, air military branch, service branch of the United States Armed Forces, and is one of the eight uniformed services of the United States. Originally created on 1 August 1907, as a part ...
released the XJ49 engine to the
National Air Museum (now the National Air and Space Museum), and is now in storage at their
Silver Hill, Maryland facility.
[NASM]
Specifications (XJ49-V-1)
See also
Notes
References
*Neal Robert J., ''Master Motor Builders'', Aero-Marine History Publishing Co. (2000)
*NASM Holdings, National Air and Space Museum, Washington, DC
External links
Packard Aircraft EnginesPackard engine specificationsImages of Packard engines including the XJ41Production statistics for all Packard engines
{{Aeroengine-specs
1940s turbojet engines
Turbofan engines
XJ-49