**Description**
We have proposed a new compressive combustion principle leading to the auto-ignition of fuel by the compression due to the collision of the pulsed supermulti-jets. This principle has the potential of nearly-complete air insulation due to encasing burned gas around the center of a combustion chamber and a relatively high compression ratio around the chamber center while suppressing vibration and noise levels like that of conventional engines. We have developed the first prototype engine having a very small combustion chamber of a diameter of 18 mm and also 14 side passages for the supermulti-jets. The combustion experimental results indicating the air insulation effect and high thrust over 100 N were obtained. However, it was also found that higher compression is necessary to stabilize combustion. Therefore, we have created the second engine with 24 side passages by using a metal 3D printer. In our past research, we experimented without combustion and a computational simulation, and it was confirmed that the second engine enables a higher compression ratio than that of the first prototype engine.
In this research, we conducted a fundamental combustion experiment using the second engine and confirmed the ignition of the fuel, though less fuel at oxidant-fuel ratio leaner than that at stoichiometric condition was injected in the experiment with the second engine than that in the experiment with the first prototype engine. The experimental data obtained imply that auto-ignition occurs due to the collision of the supermulti-jets. Furthermore, we also performed computational simulation corresponding to the combustion experiment for the shape of the second engine and compare the computational result with the experimental result. These results might be evidence that the second engine enables more stable combustion than the first prototype engine.

**Author(s) - ranked in descending order of contribution / as it should appear when published**
Tomotaka Kobayashi, Ken Naitoh, Aro Migita, Kohei Murata, Ryuki Nakagawa, Sato Matsumura, Daiki Ito, Riku Sato, Yuta Toba, Daiki Okada



Experimental and computational study of auto-ignition in the new prototype engine with focusing compression due to supermulti-jets colliding

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