The topic of this paper is the design of fuel valve nozzles for natural gas engines that maximize the kinetic energy and momentum of the injected fuel and maintain a required mass flow rate. The nozzle design used both the method of characteristics and computational fluid dynamics (CFD). Three types of nozzles were designed: a converging-diverging nozzle, three conical nozzles and an aerospike nozzle. The evaluation of the performance of the nozzle designs was conducted using Computational Fluid Dynamics. CFD simulations were used to calculate the average axial momentum per unit fuel mass and the average kinetic energy per unit fuel mass in the jets emanating from each nozzle. The performance was computed in off-design conditions (2.9MPa, 3.1MPa) as well as for the nominal design supply pressure of 3 MPa. Results showed that for the new nozzle designs, the average axial momentum per unit mass was improved by 17 to 24% and the average kinetic energy per unit fuel mass was improved by 30 to 80% compared with a standard shrouded poppet valve. Of the candidate designs, the converging-diverging nozzle gave the best performance, and the simple 15 degree conical nozzle also performed very well.

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