A precombustor system (300) including an ignition chamber (301) having a front wall (308), a central axis, a diameter Dic, and an outlet (313) configured to discharge a product gas (315). The ignition chamber (301) includes a central ignition oxygen injector (307) configured to inject a first oxygen stream from the front wall (308) substantially parallel to the central axis, and a tangential primary fuel injector (303) configured to inject a primary fuel stream tangential to the central axis at a location an axial distance Xpf downstream of the front wall (308). The ratio Xpf/Dic is from 0.25 to 4.0. The central axis forms an angle a with a vertical line of less than or equal to about 45 degrees. The trajectory of the primary fuel stream forms an angle θ with a plane that is perpendicular to the central axis of less than or equal to about 20 degrees. A method for combustion is also disclosed.