A centerline injection system for a liquid-only reductant delivery. An aftertreatment system comprises an aftertreatment component structured to treat exhaust exiting an engine, a reactor pipe, and a liquid-only dosing unit. The reactor pipe is positioned upstream of the aftertreatment component and is structured to receive the exhaust from the engine. The liquid-only dosing unit is structured to inject diesel exhaust fluid into the exhaust received from an engine. The liquid-only dosing unit injects the diesel exhaust fluid at the centerline of the reactor pipe as to provide uniform dispersion of the diesel exhaust fluid across at least a part of the aftertreatment component.