Since 2008, LAPAN had been developing liquid-liquid rocket engines with kerosene and HNO_3 propellants with pressure-fed system. A proper gas pressure is needed for achieving optimum flow rate. Visual method has been used to measure the mass flow of propellants, but it couldn't give the exact mass flow rate, so a flow measurement device is needed. Supersonic flow meter, a kind of non-intrusive flow measurement device, had been used previously. Unfortunately, the measurement is failed, probably because the bubbles from the flow of the propellants disrupted the device. Thus, orifice flow meter, a kind of intrusive flow measurement device, will be used. This paper is aimed to discuss the loss in terms of flow rate of a D and D/2 orifice meter, as compared to a plain pipe by using ANSYS Fluent. The 3D model of the pipe with orifice and without orifice were created using SolidWorks and have dimensions as follows, d = 9.53 mm, D = 19.05 mm, R = 95 mm, and L = 483 mm. The meshing was structured with 3D tetrahedron elements and local inflation function was applied. For further meshing quality refinement, body sizing is defined to be 1 mm in element size and local method set as automatic. The CFD analysis has been solved by using ANSYS Fluent and using realizable k-e model to describe the behavior of turbulent flows, with the boundary conditions at the inlet and outlet sections are 3.0 105 Pa and 0 Pa, respectively. The fluid used in simulations are nitric acid (HNO_3) with ANSYS Fluent default configuration. The results showed that the plain pipe has a volumetric flow rate of 1.0099552 l/s and the pipe with orifice has a volumetric flow rate of 0.808536 l/s, thus the orifice meter losses 0.2 l/s.
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