Experimental Measurements and Computations for Clarifying Nearly Complete Air-Insulation Obtained by the Concept of Colliding Pulsed Supermulti-Jets

In our previous papers, a new concept of a compressive combustion engine (Fugine) was proposed based on the collision of pulsed supermulti-jets, which can enclose the burned gas around the chamber center leading to an air-insulation effect and also a lower exhaust gas temperature due to high single-point compression. In order to examine the compression level and air-insulation effect as basic data for application to automobiles, aircraft, and rockets, a prototype engine based on the concept, i.e., a piston-less prototype engine with collision of bi-octagonal pulsed multi-jets from fourteen nozzles, was developed. Some combustion results [Naitoh et al. SAE paper, 2016] were recently reported. However, there was only one measurement of wall temperature and pressure in the previous report. Thus, in this paper, more experimental data for pressures and temperatures on chamber walls and exhaust temperatures, are presented for the prototype engine. First, pressure over 0.6MPa was measured on the chamber wall. A nearly complete air insulation effect was presumably obtained based on the experimental data for temperature measured on the chamber wall. The measured exhaust temperature was at an intermediate level around 700K. Experimental data are also presented for the air-insulation effect on a small solid wall located downstream from the collision point of the supermulti-jets. Unsteady three-dimensional computations of compressible flow also indicate that the experimental result of 0.6 MPa at the cylinder wall implies pressure of about 5 MPa at the collision point of the jets. The potential for high thermal efficiency is evaluated on the basis of the data.