DESIGNING a jet engine, Mr. Mock warns at the beginning of his paper, is anything but a simple matter.
In addition to the usual powerplant requirements of efficiency, complete combustion, proper temperature distribution, and minimum volume and weight, he points out that the internal-combustion turbine is subject to certain special requirements for aircraft operation, which he outlines as follows:
  1. 1.
    It should start easily, positively, and consistently, without detriment to engine life; it should restart in the air without complex or difficult manipulation by the pilot.
  2. 2.
    The engine should fire without blow-out or die-out at all speeds, altitudes, and throttle positions that the pilot can use in flying. All air/fuel regulation should be automatic; it should not be necessary for the pilot to nurse the throttles.
  3. 3.
    To avoid fire risk, ignition should be positively accomplished under any rate of fuel flow, and burner construction should be such that liquid fuel will not accumulate or seep through the engine.
  4. 4.
    Carbon accumulation should be minimum in the burner, particularly on the spray nozzles.
  5. 5.
    Since for many duties relatively volatile fuels may have to be used, precautions must be taken against vapor lock.
Although the author does not claim that all of these requirements have been achieved as yet, he feels that in time they certainly will be. As evidence, he reveals that clean, compact combustion, wide range of inflammability, and positive starting under such adverse conditions as, for instance, 1200 to 1 total air/fuel ratio has already been accomplished in his own laboratory.
In addition to suggesting a detailed comparative rating of merit for different burners to enable experimental workers to appraise their models against other American and foreign types, the author sets forth in simple, easily visualized forms, the essential factors of jet engine combustion, and gives some idea of the broad possibilities of improvement that exist in the use of graduated air velocity, controlled turbulence, and impact heating spray.


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