• Journal of Biosystems Engineering
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• v.21 no.2
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• pp.155-166
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• 1996

A direct injection sprayer was designed using the concepts of injection mixing and total flow control, flowrate-based system compensating for the variation of forwarding speed. A metered rate, proportionally to the actual diluent flow rate, of a tracer chemical was injected directly into the diluent stream. The injection of chemical may improve the precision and safety of chemical application process. The control system was evaluated for the variables of the control interval, tolerances and sensitivities of flow regulation valve and injection pump. Performance of the system was assessed as that the response time of flow rate, response time of injection rate, absolute steady state error, and the coefficient of variance(C.V.) of concentration were 8.5 and -0.53 seconds, 0.067 lpm(0.8%) and 3.15%, respectively, at optimal parameters of control interval of 1.0 sec, fast sensitivity of flow regulation valve, medium sensitivity of injection pump and medium tolerance of flow rate. Performance of the system can be improved by increasing the sensitivity of flow regulating valve and employing a high resolution velocimeter, such as Doppler radar.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.11 no.4
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• pp.44-53
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• 2002

Injection molding process factors such as molding temperature, injection pressure, flow rate and flow velocity, must be controlled properly in filling and packing phases in the injection molding process. In this study, effects of these factors on the injection molding were investigated through the flow analysis for the filling and packing phases. Molding troubles like flow mark weld line, sink ma가 short shot and warpage car be caused by these injection molding process factors. Among them the short shot was caused by the fact that the packing pressure could not reach properly to the filling end part in the packing phase and hence the flow rate could not be supplied to the full. In addition as the flow rate for the volumetric shrinkage during the f개zen phase could not be supplied Properly by the packing pressure, the short shot appeared. Here, the volumetric shrinkage reduced with increasing the packing pressure and also the warpage of molded part increased with increasing the packing Pressure.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.04a
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• pp.112-118
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• 2002

Injection molding process factors such as molding temperature, injection pressure, flow rate and flow velocity, must be controlled properly in filling and packing phases in the injection molding process. In this study, effects of these factors on the injection molding were investigated through the flow analysis fur the filling and packing phases. Molding troubles like flow mark, weld line, sink mark, short shot and warpage can be caused by these injection molding process factors. Among them, the short shot was caused by that the packing pressure could not reach properly to the filling end part in the packing phase and hence the flow rate could not be supplied to the full. In addition, as the flow rate for the volumetric shrinkage during the frozen phase could not be supplied properly by the packing pressure, the short shot appeared. Here, the volumetric shrinkage reduced with increasing the packing pressure and also the warpage of molded part increased with increasing the packing pressure.

• 한국전산유체공학회:학술대회논문집
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• 2005.10a
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• pp.39-44
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• 2005

In HANARO, a multi-purpose research reactor of 30 MWth, the emergency water supply system consists essentially of an emergency water storage tank located in the level of about thirteen meter (13 m) above the reactor core, a three inch ('3\%') diameter water injection pipe line including injection valves from the tank to the reactor cooling inlet pipe and a test loop to do periodic system performance test. When the water level of the reactor pool comes down to the extremely low due to a loss of reactor pool water accident the emergency water stored in the tank should be fed to the core by the gravity force and at that time the design flow rate is eleven point four kilogram per second (11.4 kg/s). But it is impossible periodically to measure the injection flow rate under the emergency condition because the normal water level should be maintained during the reactor operation. This paper describes a flow network analysis to simulate the flow rate under the emergency condition. As results, it was confirmed through the analysis results that the calculated flow rate agrees with the design requirement under the emergency condition.

• Design & Manufacturing
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• v.6 no.2
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• pp.1-5
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• 2012

Weld line in injection molded part is one of the defects in injection molding process. Weld line deteriorates not only appearance quality but mechanical property. In this study, ABS and PP were used as experimental materials. And weld line length, depth and strength have been examined according to the injection molding conditions. As the results of experimental studies, weld line length increased as flow rate increases for all materials. And the flow rate is most influenced to the creation of weld line length. Also weld line strength increased, as flow rate and melt temperature increase for all materials. The whole experiment results was similar to CAE analysis results.

• 한국금형공학회:학술대회논문집
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• 2008.06a
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• pp.115-119
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• 2008

Weld line in injection molded part is one of the defects in injection molding process. Weld line deteriorates not only appearance quality but mechanical property. In this study, ABS and PP were used as experimental materials. And weld line length, depth and strength have been examined according to the injection molding conditions. As the results of experimental studies, weld line length increased as flow rate increases for all materials. And the flow rate is most influenced to the creation of weld line length. Also weld line strength increased, as flow rate and melt temperature increase for all materials. The whole experiment results was similar to CAE analysis results.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1996.06c
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• pp.500-510
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• 1996

A Direct injection -mixing total -flow -control sprayer was developed and evaluated . The system provided precise application rates and minimized operator exposure to chemicals as well as providing a possibility for recycling container so f unused chemicals that can causes environmental contamination. Chemicals were metered and injected proportionally to the diluent flow rate to provide constant concentrations. The main diluent flow was varied in response to changes in travel speed. Experimental variables of the sprayer were the control interval, the sensitivity of flow regulating valve, the tolerance of control object and the sensitivity of the injection pump system. The optimal performance of the flow control system was with an average response time of 8.5 sec at an absolute steady state of error of 0.067 L/min (0.8% of flow rate). The average response time of the injection rate was -0.53 sec and the coefficient of variation (CV) of concentration was 3.2%.

• Journal of ILASS-Korea
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• v.27 no.4
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• pp.181-187
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• 2022

For carbon neutrality, direct-injection hydrogen engines are attracting attention as a future power source. It is essential to estimate the transient injection rate of hydrogen for the optimization of hydrogen injection in direct injection engines. However, conventional injection rate measurement techniques for liquid fuels based on the injection-induced fuel pressure change in a test section are difficult to be applied to gaseous fuels due to the compressibility of the gas and the sealing issue of the components. In this study, a momentum flux measurement technique is introduced to obtain the transient injection rate of gaseous fuels using a force sensor. The injection rate calculation models associated with the momentum flux measurement technique are presented first. Then, the volumetric injection rates are estimated based on the momentum flux data and the calculation models and compared with those measured by a volumetric flow rate meter. The results showed that the momentum flux measurement can detect the injection start and end timings and the transient and steady regimes of the fuel injection. However, the estimated volumetric injection rates showed a large difference from the measured injection rates. An alternative method is suggested that corrects the estimated injection rate results based on the measured mean volumetric flow rates.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.375-376
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• 2006

Thermoplastic elastomer(TPE) can be molded by conventional injection molding. Therefore TPE injection molding could be analyzed by commercial flow analysis software. However there are a little of gaps on CAE simulation results and practical molding. In this study, the properties of TPE were measured and applied to CAE simulation for comparing the simulation flow pattern and real flow pattern. The pattern that was controlled by injection time was match. The pattern that was controlled by injection stroke and rate was not match.

• Journal of Industrial Technology
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• v.20 no.B
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• pp.45-53
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• 2000

A numerical study is done on the thrust vector control using gaseous secondary injection in the rocket nozzle. A commercial code, PHOENICS, is used to simulate the rocket nozzle flow. A $45^{\circ}-15^{\circ}$ conical nozzle is adopted to do numerical experiments. The flow in a rocket nozzle is assumed a steady, compressible, viscous flow. The exhaust gas of the rocket motor is used as an injectant to control the thrust vector of rocket at the constant rate of secondary injection flow. The injection location which is on the wall of rocket is chosen as a primary numerical variable. Computational results say that if the injection position is too close to nozzle throat, the reflected shock occurs. On the other hand, the more mass flow rate of injection is needed to get enough side thrust when the injection position is moved too far from the throat.