Free jet sampling - a motley mix of methods and applications

Conference · Wed Mar 01 04:00:00 EST 1995

OSTI ID:110826

Fenn, J B ^[1]

---

1. Virginia Commonwealth Univ., Richmond, VA (United States)

When flowing gas issues into a chamber from an orifice or nozzle whose diameter is much smaller than that of the chamber, the resulting flow field constitutes a {open_quotes}free jet{close_quotes} bounded by relatively quiescent gas. If the pressure ratio across that nozzle or orifice exceeds a critical value (around 2.5 for most gases) the flow velocity will exceed the local speed of sound and the flow field is called a {open_quotes}supersonic free jet{close_quotes}. Though somewhat exotic in name such supersonic jets are really quite common. What might be regarded as the modern era for analysis and application of supersonic free jets began in 1948 with a calculation by Owen and Thornhill who used the method of characteristics to solve Euler`s equation for the flow field formed by the free expansion of gas from a sonic orifice into a region of zero pressure. Three years-later in another now-classic paper Kantrowitz and Grey proposed the use of a supersonic low density flow field as a source for molecular beams of high intensity. These two independent communications, motivated by entirely different interests and objectives, were destined to become related as the ancestors of a large progeny that form a flourishing family tree with many roots and branches. Some of the fruits of that tree are being served at this conference. They come from a branch that sprouted from the early experiments of E.W. Becker and his colleagues at the University of Marburg in 1954. These investigators were the first to achieve, by design, substantial success in reducing to practice the ideas set forth by Kantrowitz and Grey. However, in the interests of historical accuracy it should be noted 27 years earlier, T.H. Johnson at Yale produced an intense molecular beam from a supersonic free jet of mercury vapor. Unfortunately, at that time his results were neither understood nor appreciated so he has not received the recognition and credit that he clearly deserves.

• Research Organization: National Renewable Energy Lab., Golden, CO (United States)
• OSTI ID: 110826
• Report Number(s): NREL/CP--433-7748; CONF-9410343--; ON: DE95004052
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
JETS
MASS SPECTROSCOPY
MOLECULAR BEAMS
NOZZLES
SUPERSONIC FLOW
USES