Experimental measurements and computations for clarifying nearly complete air-insulation obtained by the concept of supermulti-jets colliding with pulsation

Paper #:
  • 2017-01-1030

  • 2017-03-28
In our previous reports, a new concept of compressive combustion engine (Fugine) was proposed by us based on the collision of pulsed supermulti-jets, which can enclose the burned gas around the chamber center leading to air-insulation effect. In order to examine the compression level and air-insulation effect as a basic data for applications to automobiles, aircraft, and rockets, we developed prototype engines based on the concept, i.e., piston-less prototype engines having collision of bi-octagonal pulsed multi-jets from fourteen nozzles. We recently reported some combustion results [Naitoh et al. SAE paper, 2016]. However, there were only two trials of combustion experiments in the previous report. Thus, in this paper, more experimental data of pressures and temperatures of chamber walls, exhaust temperatures, air-fuel ratios, and photographs are shown for the prototype engine. First, pressure over 0.6[MPa] is measured on the chamber wall, while nearly complete air insulation effect is obtained from experimental data of temperature measured on chamber wall, and exhaust temperature measured is at a middle level around 700[K]. Improvement of temperature sensor was done because of very fast transonic or supersonic flows. Unsteady three-dimensional computations of compressible flow and combustion also show that high temperature gas does not touch the piston, which implies air-insulation effect. The experimental result of 0.6[MPa] at cylinder wall imply 5[MPa] at the collision point of jets, from computation. It is stressed that the engine power and thermal efficiency are evaluated by using the above data. A small wall is added at the downstream position of the combustion area where supermulti-jets collide with pulsation, because this wall may improve pressure ratio by sympathetic resonance of pressure waves reflected on the wall and point-compression around the chamber center. It is stressed that the small wall does not melt due to air-insulation.
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