A liquid fuel (14) is contained in a fuel container, and the liquid fuel (14) is discharged from a fuel outlet (31). Further, a water (12) is contained in a water containing pipe (10) provided in the fuel container, and the water (12) is discharged from a water outlet (33) to the outside. Air taken into the fuel container through a dustproof filter (8) attached to a rear lid portion of the fuel container is discharged to the outside from an oxygen source outlet (32) through an oxygen source pipe (9). The fuel outlet (31), oxygen source outlet (32) and water outlet (33) are provided in a front outer surface (3a) of the front lid portion (3).