• Journal of the korean Society of Automotive Engineers
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• v.9 no.4
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• pp.35-40
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• 1987

The experimental study, using constant pressure injection system, is carried out to investigate the effect of the geometrical shape changes of the needle valve of the effective flow area, the spray angle and the Sauter's Mean Diameter according to needle valve lift for a pintle-type injection nozzle. The results are as follows: 1) With the increase of the needle valve lift, the effective flow area is increased, the spray angle is at first increased and later decreased, and the Sauter's Mean Diameter is decreased. 2) It is also shown that the spray angle is maximum at the rapidly increased region of the effective flow area.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.5
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• pp.1330-1336
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• 1990

The factors to act on atomization of liquid fuel are viscosity, geometric shape of nozzle, atomizing pressure, etc. Most of high viscous liquid fuels show decrease in viscosity by raising the preheat temperature, but the viscosity of liquid fuel like CWM does not readily change with fuel temperature. As an experimental study to investigate the atomizing characteristics of CWM, CWM fuel is atomizing with a twin-fluid atomizer, and the effects of the geometric shape of spray nozzle on atomization are investigated by measuring the Sauter`s Mean Diameter (SMD) of CWM. The summarized results obtained in this study are as follows ; (1) As the ratio of the mass flows of atomizing air to that of fuel (W$_{a}$ /W$_{1}$) increases, 능 decreases when fuel temperature is constant. (2) At the ratio (t/d) 4 of thickness (t) of spray nozzle hole to the diameter (d) of the hole, there is the best atomization. And SMD decreases when t/d is between 1 to 4 and increases when t/d > 4.

• Journal of the Korean Society of Propulsion Engineers
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• v.26 no.5
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• pp.44-51
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• 2022

In this study, 5-axis machining was proposed as a method for manufacturing a nozzle with a curved shape, and flow analysis and structural analysis were used for structural validation of the manufactured geometry. The program used for CFD obtained the internal temperature and pressure distribution of the nozzle using STAR-CCM+ and used it as the boundary condition for structural analysis. For structural analysis, the commercial program NASTRAN was used, and stress was calculated using the von-mises technique. Based on the maximum stress value generated, the safety margin was 0.78 and the safety margin of the bearing stress was 46.8. In addition, the creep life was calculated as 9.97 x 1012 hours using the Larson-Miller parametric method and applying the maximum stress value of 187 MPa and the exhaust gas perfectly mixed temperature of 463 K.

• Journal of the Korean Society of Propulsion Engineers
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• v.6 no.2
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• pp.1-7
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• 2002

In the modern propulsion systems, requited thrust is obtained using a nozzle. Sometimes shock and induced boundary layer separation is generated in an over-expanded convergent-divergent supersonic nozzle. It occurs because the nozzle expansion ratio is too large for a given nozzle pressure ratio (NPR). This phenomenon can be explained that it redefines effective nozzle geometry, shorer nozzle geometry and lower pressure ratio, in a given pressure ratio. Numerical studies were conducted about a fixed geometry 2D nozzle in overexpanded condition and compared with Hunter's experimental result. For the numerical simulation of the supersonic nozzle, Navier-Stokes equations are considered and as a turbulent model, $\kappa$-$\varepsilon$ /$\kappa$-$\omega$ blended SST two equation turbulent model is used. The characteristics of $\lambda$-shape shock systems due to the interaction of shock and boundary layer was investigated in a low NPR. And the result of comparison of thrust value shows that a fixed geometry nozzle can cover required flight mission.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.5
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• pp.800-809
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• 1987

For precise stress analysis of pressure vessel nozzle junction area, it should be modelized as a cylindrical shell with a cylindrical outlet attached on it, but because of its geometrical complexity, exact analysis and solution is very difficult to obtain. So, when the nozzle diameter is small compared to that of vessel, it is general to simplify the model as a flat plate with a cylinder. As the current nozzle shape is manufactured as "Through Type" to reduce the stress concentration around the nozzle junction part of pressure vessel, a theoretical analysis on the cylinder with finite length should be performed to accomodate this fact. In this paper, the general solutions which were obtained by applying Fulgge's theory to the finite length cylinder, membrane and bending theory to the flat plate were superposed to analyze the model. Each theoretical optimal values were obtained through the analysis of stress concentration caused by the variation of cylinder length and thickness, and these results were estimated by performing model experimentation.mentation.

• Journal of ILASS-Korea
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• v.12 no.1
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• pp.11-17
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• 2007

The swirl spray for direct-injection spark-ignition (DISI) engines was investigated using a nozzle whose exit surface shape was cut with a certain tapered angle. The reason for the change in spray's characteristics at various tapered angles was explained by the data correlating the taper and flow angles. The spray tended to shift its characteristics from the symmetric to asymmetric when the tapered angle was increased; furthermore, the spray penetration and spray cone angle were also increased. When the tapered angle was greater than the $90^{\circ}$ minus flow angle, an opened hollow cone spray was formed because of the fuel impingement against the tapered surface area of the nozzle exit. This behavior indicates that the reduction in the air pressure difference between the inner and outer spray of the spray can be achieved. This behavior also promises the potential use of the tapered nozzle for the case where the independence of the spray performance from atmospheric pressure and fuel temperature is desired.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.159-159
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• 2011

Among the semiconductor ternary compounds in the I-III-$VI_2$ series, $CulnS_2$ ($CulnSe_2$) are one of the promising materials for photovoltaic applications because of the suitability of their electrical and optical properties. The $CuInS_2$ thin film is one of I-III-$VI_2$ type semiconductors, which crystallizes in the chalcopyrite structure. Its direct band gap of 1.5 eV, high absorption coefficient and environmental viewpoint that $CuInS_2$ does not contain any toxic constituents make it suitable for terrestrial photovoltaic applications. A variety of techniques have been applied to deposit $CuInS_2$ thin films, such as single/double source evaporation, coevaporation, rf sputtering, chemical vapor deposition and chemical spray pyrolysis. This is the first report that $CuInS_2$ thin films have been prepared by Aerosol Jet Deposition (AJD) technique which is a novel and attractive method because thin films with high deposition rate can be grown at very low cost. In this study, $CuInS_2$ thin films have been prepared by Aerosol Jet Deposition (AJD) method which employs a nozzle expansion. The mixed fluid is expanded through the nozzle into the chamber evacuated in a lower pressure to deposit $CuInS_2$ films on Mo coated glass substrate. In this AJD system, the characteristics of $CuInS_2$ films are dependent on various deposition parameters, such as compositional ratio of precursor solution, flow rate of carrier gas, stagnation pressure, substrate temperature, nozzle shape, nozzle size and chamber pressure, etc. In this report, $CuInS_2$ thin films are deposited using the deposition parameters such as the compositional ratio of the precursor solution and the substrate temperature. The deposited $CuInS_2$ thin films will be analyzed in terms of deposition rate, crystal structure, and optical properties.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.565-569
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• 2011

A two-dimensional thermal response and ablation analysis code for predicting charring material ablation and shape change on solid rocket nozzle is presented. For closing the problem of thermo-structural analysis, Arrhenius' equation and Zvyagin's ablation model are used. The moving boundary problem are solved by remeshing-rezoning method. For simulation of complicated thermal protection systems, this method is integrated with a three-dimensional finite-element thermal and structure analysis code.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.05a
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• pp.275-278
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• 2010

By changing the nozzle throat area during the operation, thrust of a pintle thruster can be adjusted easily such as a liquid propulsion. In this paper, numerical analysis was carried out for SNECMA's pintle thruster with different pintle shapes. Flow field and aerodynamic load changed drastically with pintle shapes. Bore in the pintle decreased aerodynamic load significantly.

• Transactions of Materials Processing
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• v.31 no.2
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• pp.89-95
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• 2022

3D printing products manufactured by material extrusion are used in many industrial fields recently. However, these products are difficult to use in the field due to their low tensile strengths. In order to solve this problem, research on improving the tensile strength of the output using a 3D printer has been continuously conducted. In this study, we performed a tensile test using Universal Testing Machine according to infill pattern, nozzle temperature, bed temperature, and printing speed conditions. Results revealed that tensile specimen of concentric shape had the highest tensile strength in infill pattern condition and that the tensile strength increased linearly with increasing nozzle and bed temperatures. However, the tensile strength decreased with increasing printing speed. Consequently, we confirmed that tensile strength could be increased and decreased depending on output conditions of 3D printing.