Liquid hydrogen is a key energy carrier for decarbonizing heavy-duty transportation due to its high energy density and zero carbon emissions. The reliable delivery of liquid hydrogen from storage to utilization points requires efficient pressurization systems, where conventional mechanical pumps face challenges related to cryogenic cavitation, thermal gradients, and maintenance. In this context, passive injection technologies offer a promising alternative by enabling fluid pressurization without moving parts, thereby enhancing system reliability and compactness. This work presents a numerical model and parametric analysis of a liquid hydrogen injector that operates through direct vapor-liquid interaction and condensation-driven momentum transfer. A one-dimensional, axisymmetric model is developed based on conservation laws across defined control volumes, incorporating real fluid properties and accounting for phase change during mixing. The model is applied to analyze injector performance under diverse inlet conditions, including variations in vapor temperature and pressure, and geometric parameters. Results demonstrate the capability to achieve significant pressure lift, with performance maps identifying optimal operating regions. The analysis provides insights into the thermodynamic process within the device, highlighting the role of condensation shocks in pressure lift.