Adam P. Wells

High-Performance Airfoil Using Coflow Jet Flow Control

T O ACHIEVE revolutionary aircraft performance, advanced technologies should be pursued to drastically reduce the weight of aircraft and fuel consumption and significantly increase aircraft mission payload and maneuverability. Both the military and commercial aircraft will benefit from the same technology. Flow control is a promising technology to break through the limits of the conventional aerodynamic concepts. Recently, a novel active airfoil flow control concept with zero-net mass flux, the coflow jet (CFJ) airfoil, has been developed by Zha et al. [1–5]. The CFJ airfoil achieves three effects simultaneously in a dramatic fashion: lift augmentation, stall margin increase, and drag reduction. The energy expenditure of the CFJ airfoil is low [1], and the CFJ airfoil concept is straightforward to implement. The CFJ airfoil may create a new concept of an “engineless” airplane, which uses the CFJ to generate both lift and thrust without conventional propulsion systems of propellers or jet engines [6]. A CFJ airfoil [1–5] uses an injection slot near the leading edge (LE) and a suction slot near the trailing edge (TE) on the airfoil suction surface. Similar to tangential blowing, the LE jet is in the same direction of the main flow, but the same amount of mass flow that is injected is removed via suction near the TE, resulting in zeronet mass-flux flow control. A proposed fundamental mechanism [2] is that the severe adverse pressure gradient on the suction surface strongly augments turbulent mixing between the main flow and the jet [7]. The mixing then creates the lateral transport of energy from the jet to the main flow and enables the main flow to overcome the large adverse pressure gradient and remain attached at high angle of attack (AOA). The stall margin is hence significantly increased. At the same time, the high-momentum jet drastically increases the circulation, which significantly augments lift, reduces drag, or even generates thrust (negative drag). The objective of this paper is to demonstrate the high performance of the CFJ airfoil with the windtunnel test results.

Effect of Injection Slot Size on the Performance of Coflow Jet Airfoil

Two coflowjet airfoils with injection slot size differing by a factor of 2 are tested in a wind tunnel to study the effect of injection slot size. At the same angle of attack, the larger injection slot size airfoil passes about twice the jet mass flow rate of the smaller injection slot size airfoil. The smaller injection slot size airfoil is more effective in increasing the stall margin and maximum lift, whereas the larger slot coflow jet airfoil is more effective in reducing drag. To achieve the same lift, the smaller injection slot size airfoil has much less energy expenditure than the larger injection slot airfoil. A coefficient of jet kinetic energy is introduced, which appears to correlate well with the maximum lift and stall margin when coflow jet airfoil geometry varies. Both the jet kinetic energy coefficient and the momentum coefficient correlate well with drag reduction. No optimization of the airfoil configuration is pursued in this research, and the results indicate that there is a great potential for coflow jet airfoil performance improvement.

2-bromo-3,3,3-trifluoropropene: A facile trifluoromethylacetylene anion synthon

Abstract The introduction of trifluoromethylacetylene units into organic compounds has been further studied and extended. The direct reaction of two equivalents of Lithium Diisopropylamide with 2-bromo-3,3.3-trifluoropropene gave lithium trifluoromethylacetylide, the anion of which was trapped in greater than 90% overall yield with a variety of electrophiles.

1-(1-Alkenyl)benzotriazoles: Novel α-Hydroxyacyl Anion Equivalents for the Synthesis of α-Hydroxy Ketones

Abstract α-Lithiated 1-(1-alkenyl)benzotriazoles, generated from the reactions of 1-(1-alkenyl)benzotriazoles with n-BuLi, react with a variety of electrophiles to afford α-substituted 1-(1-alkenyl)benzotriazoles which undergo epoxidation with m-CPBA followed by hydrolysis to give α-hydroxy ketones in good yields. Thus, 1-(1-alkenyl)benzotriazoles behave as α-hydroxyacyl anion equivalents.

ADDITIONS OF 5-PHENYLTETRAZOLE AND OTHER HETEROCYCLIC NH COMPOUNDS TO OLEFINS

The reactivity of a range of heterocyclic NH compounds toward cyclohexene underp-toluenesulfonic acid catalysis was surveyed. 1,2,4-Triazole (38%), carbazole (67%) and 5-phenyltetrazole (83%) gave significant amounts of addition products. 5-Phenyltetrazole reacts with a wide range of unactivated olefins, to give addition products in 65% to 90% yield. This method represents a general, preparatively useful route to 2-alkyl-5-phenyltetrazoles.

Mechanistic studies of the palladium(II)–copper(II)-mediated demercuriation of cycloalkyl and cycloalkylmethyl systems

The likely events involved in the conversion of cyclohexylmethylmercuric chloride into predominantly trans-4-methylcyclohexyl chloride, on treatment with PdCl2–CuCl2 in acetic acid, have been identified by product and deuterium-labelling studies, as well as by the behaviour of probable intermediates. Extension to related cycloalkyl- and cycloalkylmethyl-mercuric chlorides is reported, and mechanistic changes occur as a function of ring size, with elimination–re-addition of [HPdX] being important in cyclohexyl systems, but carbocation formation dominating in cyclooctyl cases.

Velocity field for an airfoil with co-flow jet flow control

*† ‡ § ** The wind tunnel tests reported in this paper demonstrate the ability of the co-flow jet airfoil to dramatically increase lift, stall margin, and drag reduction. Detailed velocity field measurements are reported for a baseline NACA0025 airfoil and two variants of the baseline which implement the co-flow jet. The first variant has an injection slot size of 0.65% of chord while the second has an injection slot size twice that size.

The first examples of the addition of heterocyclic NH to unactivated olefins

Benzotriazole adds to aliphatic open-chain and cyclic alkenes at 80 °C under toluene-p-sulfonic acid catalysis. Terminal aliphatic olefins give solely 2-(benzotriazol-1- and -2-y-1)alkanes, which are stable to acid. In the presence of an excess of acid, all possible non-terminal benzotriazol-1-and -2-y-1 addition products are obtained, owing to a facile migration of the double bond in the starting olefin. Addition also occurs to phenylalkenes with the intervention of some bond migration.

Electrophile induced reactions of medium ring vinyl- and 1,2-epoxy-silanes and related compounds

Deuterium labelling studies confirm extensive trans-annular participation in acidolysis, acetylation and brominolysis of 1,2-epoxy-1-trimethylsilylcyclooctane and (E)-1-trimethylsilylcyclooctene, and require revision of previous mechanistic proposals.

13C chemical-shift assignments in cyclooctyl derivatives from the spectra of deuterioisotopomers. Deuterium isotope effects on chemical shifts and conformational equilibria

The 13C NMR spectra of some derivatives of (Z)-cyclooctene, cyclooctanols and cyclooctanone have been assigned by consideration of substituent effects, 1H–13C correlated spectra, and 2H isotope effects. Some four-bond downfield 2H effects (+4Δ) on certain chemical shifts have been measured and attributed to conformational equilibrium perturbations and trans-annular 1H–1H interactions. The data provide a basis for further assignments in these systems.