• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.6
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• pp.19-27
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• 2018

In this study, a numerical study was conducted to characterize the E-D nozzle which changes according to the nozzle pressure ratios. Three different numerical analysis models were designed by changing the pintle inflection angles. When the nozzle pressure ratio is low, the outside air flows into the E-D nozzle to form an open flow field. As the nozzle pressure ratio increases, the flow transition occurs to become the closed flow field where the recirculation region is isolated inside the nozzle. Also, the highest thrust coefficient was obtained in the analytical model with high pintle inflection angle at all nozzle pressure ratios.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.2
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• pp.41-47
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• 2017

By using liquid and gaseous nitrogen as simulants, effects of pintle opening distance and simulant supplying condition on spray from pintle injector were investigated qualitatively. The experiment was performed by fixing the liquid supply pressure and varying the opening of the pintle and the supply pressure of gaseous nitrogen. Shadowgraph method with CCD camera was used for image visualization, and the differences of liquid-gas spray were compared by image post processing. In case of liquid nitrogen single injection, as the opening distance was increased, the injection speed was decreased. Therefore, the end of liquid sheet were converged to the center of spray. In the case of liquid nitrogen/Gaseous nitrogen spray, although shadowgraph images look similar to each other, It is shown that it can be analysed by image post processing.

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.3
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• pp.20-28
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• 2015

Performance parameters of solid rocket motor with multi axis pintle nozzles were analyzed theoretically and modeled. For figuring out the governed variable of dynamic characteristics of system, dynamic analysis was done by using established model. To present characteristics of this system, the model should include not only internal ballistics of propulsion unit but also actuating system to move pintle. For solid rocket motor with multi axis pintle nozzles, not only performance of steady state but also dynamic characteristic of transient state is important design parameter to precise thrust control. Therefore, response time of open-loop system was analyzed by using established model and requirement about response time was satisfied by controlling pressure.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.5
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• pp.19-28
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• 2014

Firing test of solid rocket motor with pintle-technology carried out and the measured pressure-time curve was compared with the values predicted by the internal ballistic and performance analysis. Without baffle, the measured combustion chamber pressure was similar with the predicted pressure at the beginning of combustion, but gradual increase in pressure, which was unexpected with the end-burning grain of which burning area is constant, was observed. A baffle was inserted to make uniform flow over the pintle. Unlike the thruster without baffle, the measured combustion chamber pressure was 1.4 times higher than the predicted value. Through the CFD simulation, 10% of total pressure loss of the flow was observed from combustion chamber to nozzle throat when the baffle was inserted. The measured pressure with baffle was predicted well by considering the total pressure loss in the internal ballistic modelling and performance analysis.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.5
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• pp.22-31
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• 2018

In this study, numerical simulations were performed to determine the dynamic characteristics of a pintle nozzle, with changes to the chamber boundary conditions. To apply movement, to the pintle, the nozzle and pintle were created separately by an auto-grid generation program using an overset grid method. The chamber boundary conditions were selected between a constant mass-flow rate condition and a propellant burn-back condition. The pressure and thrust characteristics of the constant mass-flow rate condition were determined by changing the ratio of the mass-flow rate in the inlet. The propellant burn-back condition was considered by formulation of the combustion rate. The burn-back conditions represented nonlinear phenomena, unlike the constant mass flow rate, and a small flow rate resulted in a large change in the chamber pressure.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.3
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• pp.14-25
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• 2021

An experimental study was conducted on the spray characteristics of the pintle injector by opening distance. The discharge coefficient of the pintle injector was investigated and the spray angle was measured by taking the spray image by test conditions. As a result of the measurement of the discharge coefficient, it was confirmed that the change in the discharge coefficient of the outer injector was not significant over the experimental conditions, but the change in the discharge coefficient of the inner injector was decreased as the flow rate increased. Measurement of the spray angle showed that the change in the spray angle was not significant in the conditions under which the spray was fully developed, but the spray was not fully developed at low flow rates. This confirmed the possibility of thrust control using the pintle injector.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.8
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• pp.1077-1085
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• 1997

The use of "clean fuels" such as butane, propane, and mixtures of these (LPG) is an attractive way to reduce exhaust emissions. In this study internal flow of the pintle type injector for LPG engine is studied. The breakup of liquid jet is the result of competing, unstable hydrodynamic forces acting on the liquid jet as it exits the nozzle. The nozzle geometry and up-stream injection conditions affect the characteristics of flow inside the nozzle, such as turbulence and cavitation bubbles. A set of calculations of the internal flow in a pintle type nozzle were performed using a two dimensional flow simulation under different nozzle geometry and upstream flow conditions. The calculation showed that the turbulent intensity and discharge coefficient are related to needle leading angle(.alpha.) and needle lift.edle lift.

• Journal of ILASS-Korea
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• v.3 no.1
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• pp.34-42
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• 1998

The correlation between the droplets size and the velocity are investigated for an intermittent spray of the pintle type fuel injector employed in a port injection gasoline engine. The analysis such as the mean droplet size, SMD, and velocity under the fixed injection period and varied fuel pressures are conducted utilizing PDPA systems. As results, the experimental data obtained, show that the larger droplet sizes. the higher velocities during the spray tip arrival time, and that at Z=70mm, r=8mm, both droplet sizes and velocities are peak. At the upstream, flow of droplets are dominated by injection pressure, which are more effected inertia force of droplets at the downstream of Z=70mm.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.405-409
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• 2010

금속분말을 청정 에너지원으로 이용하기 위해 금속분말 소형 연소기의 구현이 필요하다. 이를 위한 선행연구로 연료 공급 시스템인 핀틀인젝터형(pintle injector type) 금속분말 공급장치의 중요 성능인 분사량을 실험적으로 측정하였다. 분사량 측정 시험에 앞서 간단한 금속분말 공급 시험으로 확인된 문제점을 장치의 변경을 통해 해결하였다. 측정 시험의 결과, 연료 공급 장치에 이송 가스 압력이 상승함에 따라 많은 질유량의 금속분말이 분사되었고 압력에 따른 정량적 분사량을 확인하였다. 이송 가스와 금속분말의 혼합 성능을 개선하여 균일한 분사를 하고자 이송 가스를 25 Hz로 가진 하여 공급하였고 가진이 없는 경우의 실험결과와 비교하였다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.249-252
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• 2011

고체로켓추진기관의 추력조절을 위해 핀틀 기술이 사용된다. 아직까지 핀틀 유동에 대해 근본적인 물리적 이해를 돕는 연구가 공개되지 않아, 이 연구에서 다양한 형상의 needle형 핀틀에 따른 유동구조에 대한 수치적 연구를 진행하였다. 2차원 축대칭, 압축성을 고려하여, 상용 열유체 해석 프로그램인 FLUENT 6.2를 사용하여 해석을 수행하였다. 난류 모델을 검증하기 위해 기 수행된 실험 결과와 비교하였다. 핀틀 각도(tip angle)가 작아질수록 노즐에서 유동 박리점이 하류로 이동하며, 핀틀에서 발생하는 끝단 충격파가 약해진다. 핀틀 반경(tip radius)이 작아질수록 핀틀에서 발생하는 끝단 충격파가 하류로 이동하며, 크기는 약해진다. 핀틀 형상(contour)은 유동 박리 지점에 직접적인 영향을 미친다.