Theoretical Calculation of Pressure Characteristics in Two-Stage High-Velocity Oxy-Fuel Thermal Spray Gun Employing Supersonic Flow (Validation by Cold Flow and Actual Spray Gun Tests)

Abstract

The theoretical calculation of a two-stage high-velocity oxy-fuel thermal spray gun was conducted for the purpose of predicting the stagnant pressure in the mixing chamber (MC). The theoretical results were compared with the experimental ones obtained by the cold flow and actual spray gun tests. The effect of the diffuser shape installed between the combustion chamber (CC) and the MC was also investigated in the cold flow test. It was clarified in this study that 1) the theoretical calculation shows that in order to obtain a larger pressure in the MC the diameter rations of d_3t/d_1t and d_1e/d_1t should be chosen to satisfy Eq.(11), to keep the diffuser throat unchoked, 2) the theoretical results of p₀₃/p₀₁ agree with the results of cold flow test within an accuracy of 6%, 3) the theoretical results of p₀₁ agree with the results of actual two-stage HVOF gun test within an accuracy of 4%, demonstrating the validity of the present theoretical calculation.