디메틸에테르-공기 예혼합 화염의 화염전파특성과 화염안정성에 있어서 합성가스의 첨가효과

Abstract

The main purpose of this study is to evaluate the usability of the blend fuel compound of dimethyl ether and syngas as alternative energy. The focus was to measure the laminar burning velocity which is the most fundamental factor in determining the efficiency of internal engines and to assess the flame instability. Experiments in outwardly propagating spherical flame were carried out to investigate unstretched laminar burning velocity and flame instability by adding 25%, 50%, and 75% syngas to DME-air mixtures at room temperature and elevated pressures up to 0.3 MPa. The measured unstretched laminar burning velocities were compared to numerical predictions using PREMIX code with Zhao reaction mechanism and good agreement was found between them. Flame instability was also investigated through evaluating Markstein length and cellular instability. Behavior of the Markstein lengths was described well by the deficient reactant Lewis number and highly affected by the amount of syngas addition to the DME-air mixtures. Effects of syngas addition and increased initial pressure on cell formation on the flame surface were also examined through evaluating the Lewis number, flame thickness, and thermal expansion ratio. Regardless of syngas addition, the cellular instability was enhanced mainly by the hydrodynamic instability due to decreased flame thickness while diffusional-thermal instability was minor.