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Aviation History
1955
1955 - 1503.PDF
616 FLIGHT, 14 October 1955 Aeronautical Research in Canada—II Eleventh British Commonwealth and Empire Lecture By Dr. J. J. GREEN THE field of aviation medicine in Canada had widenedconsiderably since 1939, and today Toronto's Institute ofAviation Medicine and the Defence Research Medical Laboratory were working closely together in, respectively,development and research. The Aerophysiology Group, repre- sentative of I.A.M. and D.R.M.L., had two decompressionchambers (covering the pressure range S.L. to 100,000ft, one holding 20 men), and had inherited Toronto's human centrifugeon which the Allies first recorded convulsive episodes resulting from g. Dr. Green came to what he considered the most important partof his lecture: a review of Canada's ten years of accomplishment in aeronautical research. Shock Wave and Supersonic Studies. Earliest work of TorontoUniversity's Institute of Aerophysics compared results from study of supersonic flow through a 2in by 7in shock-tube and the theoryof one-dimensional non-stationary inyiscid flow. Velocity agreed closely with theory in the region behind the shock-wave and thefollowing "contact surface"; behind the latter, however, flow was very turbulent and velocity and duration of flow agreed withtheory only up to M = 3.4. It had been found (Bitondo) that the transmitted waves incarbon dioxide and argon were stronger than the incident waves in air, a sharp separation between air and gas having beenachieved with a very thin microfilm sheet. In the case of the collision of two shock waves in the wave-interaction tube the observations (Gould) agreed with theory (Rankine-Hugoniot equations) up to certain temperatures. Thetheory predicting amplification of the shock wave on colliding with rarefaction was found valid up to incident shock-pressure-ratios of 7. The divergent shock-tube could be useful for producing super-sonic, possibly hypersonic, flows in conditions typical of missile flight; observed flow had agreed with theory. Using the 16in by 16in tunnel for the study of heat transfercoefficient and temperature recovery factors of a flat plate model at M = 2.5, Fallis had shown results in agreement with earlierwork. Lee had set out to determine thp behaviour of the boundary layer upstream from a sharp compression corner. Thedetached shock wave on cones and wedges had been studied by Johnson. Still another programme conducted in the 16in by 16in tunnelhad involved the experimental verification of flow over a flat plate delta wing with supersonic leading edges. Below a critical anglea continuous solution to the flow existed, while above it there was discontinuity. Boundary layer measurements showed that this could be pre-dicted by theory in certain conditions. It had been shown also that flow-separation from the walls of nozzles can prevent thedesign M from being reached, and this type of flow was being explored. Supersonic tests of low aspect ratio wings. A programme toinvestigate systematically the suitability of various wing shapes for supersonic aircraft had been contributed by the National Aero-nautical Establishment since 1953. Preliminary tests of delta A model of the National Research Council tailless glider, described by Dr. Green in the second part of our abstract of his paper, in the N.R.C. spinning tunnel. THE first part of this valuable paper by Dr. J. J. Green, M.B.E., B.Sc,A.R.C.S., D.I.C., F.I.A.S., F.C.A.I., F.R.Ae.S. (Defence Research Member, Canadian Joint Staff, in Washington, D.C.) was recorded inlast week's issue. The remainder of die lecture is summarized here. wings had been followed by experiments on three families ofmodels derived from four basic shapes, resulting in eight models of the "cropped-delta" shape, and three with a "cropped-arrow"planform. Variation in aspect-ratio was accomplished by chang- ing the taper-ratio.Dr. Green turned next to the study of liquid droplets. He discussed the work of four separate laboratories of the Divisionof Mechanical Engineering, National Research Council, as follows: Fuels and Lubricants Laboratory (atomization andevaporation), Low Temperature Laboratory (icing clouds, drop- let water-content), Engine Testing Laboratory (spray nozzles forturbojet engine icing tests and droplet-size measurements), and the Gas Dynamics Laboratory (droplet-evaporation and combus-tion and internal heat-transfer). There had been a number of developments of a fundamental character. In the Fuels and Lubricant Laboratory, Sacks had measuredthe rate of evaporation of a kerosine spray from a miniature atomizer, and found it to be about three per cent per second. Anattempt to calculate the rate of evaporation using the Rosin- Rammler law showed that actual evaporation was only eight percent of that calculated using evaporation constants from Lang- miur. The Engine Testing Laboratory had experimented with the"manufacture" of clouds in the laboratory. The finest spray was given by the smallest nozzle at the highest pressure, up to 1,000lb/sq in. The range of droplet-sizes achieved had been equiva- lent to that found in natural clouds. The method used formeasuring droplets had been to collect samples on an oil-covered slide and to take a photomicrograph immediately, using a specialoil to retard evaporation. The Gas Dynamics Laboratory had been interested in themotion of liquid droplets in a gas stream, in particular the dis- tortion and internal circulation, since it was recognized that thelatter played a very important part in evaporation because of its influence on heat-transfer into the droplet. The impact of liquiddroplets on cold and hot surfaces, e.g., aircraft icing and rain erosion, was studied. Savic and Boult had investigated turbineblade-cooling by an impinging liquid. The lecturer went on to describe fundamental work on com-bustion at the University of Toronto. The nuclear theory of ignition had been the subject of a number of experiments, byKing, some 24 papers having been published in the Canadian Journal of Research. Covering a wide field of oxygen ignition anddetonation of fuel vapours and gases, Dr. Green described some of the experiments and results. Gas dynamic research at McGill University was next turned to.Daw had studied reheat systems in which the fuel was injected ahead of the turbine blades, a system which makes use of theignition delay following injection, which varied between one and ten milli-seconds. Experiments had shown a deterioration inboth compressor and turbine performance with water-injection, particularly in the case of the compressor. The study of balancing of aircraft controls was next discussedby the lecturer. In 1941 the National Research Council under- took a programme of work on the study of the influence of allthe design parameters on hinge-moment and the rate of change of hinge-moment with angle of attack and angle of deflection ofcontrol surface. At that time it had been most difficult to recon- cile wind tunnel tests with flight tests. Early work had beendone on the aileron of the Harvard aircraft; one of the reasons suggested by the Canadian investigators had been the presence offriction in the model and full scale measuring equipment, aileron fabric deflection in flight tests, improperly assessed boundary con-ditions in the tunnel, etc. Development involving improved techniques and more knowledge of necessary corrections yieldedsufficiently close agreement between the model and full-scale air- craft. Dr. Green then mentioned the Canadian tailless glider,designed, built and tested to investigate the characteristics of this type of aircraft. He recorded that the idea was inspired byG. T. R. Hill, as U.K. scientific liaison officer to Canada in 1942. Experiments yielded much useful information, although the air-craft was no exception to the stability laws applying to the tailless designs. Thought had been given by the flight research station of theNational Aeronautical Establishment to the special problem of
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