We depict and analyse the successive steps of atomization of a liquid jet when a fast gas stream blows parallel to its surface. Experiments performed with various liquids in a fast air flow show that the liquid destabilization proceeds from a two-stage mechanism: a shear instability first forms waves on the liquid. The transient acceleration experienced by the liquid suggests that a Rayleigh–Taylor type of instability is triggered at the wave crests, producing liquid ligaments which further stretch in the air stream and break into droplets.

On spray formation

A comprehensive review of measurements and data analysis of laminar burning velocities for various fuel+air mixtures

Apparatus and methods are provided for converting methane in a feed stream to acetylene. A hydrocarbon stream is introduced into a supersonic reactor and pyrolyzed to convert at least a portion of the methane to acetylene. The reactor effluent stream may be treated to convert acetylene to another hydrocarbon process.

Methane conversion apparatus and process using a supersonic flow reactor

The afterburner on a modern aircraft gas turbine engine provides significant thrust augmentation critical to the performance and mission of tactical aircraft. Higher exhaust temperatures and survivability requirements for advanced aircraft have resulted in new constraints on the augmentor design which dramatically changes the design architecture. Many of the design methods established for afterburners over the past 50 years are insufficient for the augmentor configurations being developed today. This paper will describe some of the fundamental technical challenges being faced by augmentor designers, and will outline critical needs in terms of fundamental combustion sciences and engineering that needs to be acquired to support new design methods for advanced augmentors.

Development Needs for Advanced Afterburner Designs

A method of forming an internal channel within an article, such as a cooling channel in an air-cooled blade, vane, shroud, combustor or duct of a gas turbine engine. The method generally entails forming a substrate to have a groove recessed in its surface. A solid member is then placed in the groove, with the solid member being sized and configured to only partially fill the groove so that a void remains in the groove. The void is then filled with a particulate material so that the groove is completely filled. A layer is then deposited on the surface of the substrate and over the solid member and the particulate material in the groove, after which at least the solid member is removed from the groove to form the channel in the substrate beneath the layer.

Method of forming hollow channels within a component

The liquid film flow on the inner wall of the center post of a swirl coaxial injector was analyzed theoretically. The development of the boundary layer in the liquid-film flow and the transition from laminar to turbulencewere studied. The film thickness at the post exit was measured using a contact needle probe, and the predicted film thickness was compared with the measurements. The film thickness varies in the azimuthal direction due to the geometry of the liquid inlet. The average film thickness at the post exit increases as the post length increases. The sheet cone angle and breakup length were measured using photography and a contact mesh probe, and their empirical equations were deduced by modifying those of a simplex swirl injector, taking into account the liquid momentum loss due to a long center post. These equations predict the sheet cone angle and breakup length well, except for small liquid flow rates. The mean droplet size and droplet velocity were measured by a phase Doppler particle analyzer. The measured spray characteristics exhibited characteristics similar to those of a conventional airblast atomizer.

Characteristics of Liquid Film and Spray Injected from Swirl Coaxial Injector

A method of producing rocket combustors wherein in forming an outer cylin by a powder metallurgical method on the outer side of a cylinder provided on its outer periphery with a cooling wall of channel construction having a plurality of grooves, a low-melting alloy is used as a filler to be filled into the grooves. It is also possible to form the outer cylinder after forming a Cu plating shell on the periphery of the inner cylinder filled with the low-melting alloy.

Method of producing rocket combustors

An experimental study on a 14 kN linear aerospike-nozzle combustor

During development tests of the LE-7A prototype engine, severe side-loads were observed. The side-load peaks appeared only in certain limited conditions during start-up and shut-down transients. To investigate phenomena causing those severe side-loads observed in the LE-7A prototype engine nozzle, series of cold-flow tests and hot-firing tests as well as CFD analyses were conducted. As a result of the hot-firing tests, two different phenomena were found to cause severe side-loads in the LE-7A prototype engine nozzle. One was a restricted shock separation (RSS) flow structure and the other was a phenomenon termed “separation jump,” the rapid movement of the separation location in the vicinity of the step. A step was installed in the LE-7A prototype to supply film-cooling gas. Hot-firing test results showed that RSS can occur for a limited mixture ratio. Detailed flow structure of RSS on the nozzle surface was revealed by the cold-flow tests. Measured pressures and visualized images of cold-flow tests clarified the mechanism causing the separation jump. The key phenomenon ruling the separation jump was found to be the base flow behind the step. Based on the results of the present study, the latest LE-7A engine nozzle design has been changed to eliminate the severe side-load.

Experimental evaluation of side-loads in LE-7A prototype engine nozzle

The spray and combustion characteristics of a liquid-fueled ramjet combustor were experimentally analyzed. RJ-1J fuel was injected transversely into a subsonic hot vitiation airstream from a round injection ori ce. The penetration of the liquid jet under hot air ow conditionswas larger than that calculated by the empirical equation obtained under room-temperature air ow conditions. A V-shaped gutter was attached to the center of the combustor for  ame holding. Two different arrangements of the gutter and the fuel injector were tested. In one, the fuel was injected perpendicular to the gutter axis, and in the other, the fuel was injected parallel to the axis. In regard to perpendicular fuel injection, a region with a temperature higher than 1500K was observed at the center of the combustor; this region was long and narrow in the direction of the fuel injection. The high-temperature region reached the bottomwall due to involvement of the fuel in the wake region of the fuel injector and the liquid column. In regard to parallel injection, the high-temperature region covered the major part of the cross section of the combustor except in the vicinity of the bottom wall; the measured combustion ef ciencies were higher than those for perpendicular fuel injection. Pilot fuel injection from the gutter was found to be a very effective method for improving combustion characteristics. In addition, it was found that the fuel dispersion in the direction of the injection of the high-temperature fuel, which simulates the regenerative cooling of a ramjet combustor, was lower than that of the low-temperature fuel due to fuel evaporation.

Hiroshi Sakamoto

Papers

Characteristics of Liquid Film and Spray Injected from Swirl Coaxial Injector

Method of producing rocket combustors

An experimental study on a 14 kN linear aerospike-nozzle combustor

Experimental evaluation of side-loads in LE-7A prototype engine nozzle

Spray and combustion characteristics of a liquid-fueled ramjet combustor