Dynamic Flow Characteristic of the Liquid Swirl Injector

( Seokgyu Jeong ),( Yunjae Chung ),( Youngbin Yoon ) 한국액체미립화학회 2017 한국액체미립화학회 학술강연회 논문집 Vol.2017 No.-

Liquid rocket engines are divided into three parts: feed system, injector, and combustion chamber. Among them, the injector is a device for injecting the propellant which is supplied from the feed system into the combustion chamber. Depending on the performance of the injector, atomization and mixing characteristics of the propellant are enhanced, and that can be leading to stable combustion, and the efficiency of the overall rocket engine can be improved. A study on injector dynamics has been carried out as a method to reduce combustion instability, and Bazarov established the theory on it. An indicator of this combustion instability characteristic is the injector transfer function, which can be expressed as the propellant flow rate at the injector outlet to the pressure applied to the injector. In the case of swirl injector, peaks may occur at specific frequencies as the propellant passes through the injector. When this phenomenon occurs, the atomization characteristics of the outside of injector as well as the inside of the injector may be different due to the flow perturbation. In this study, a pulsator was installed on the injector feed line to apply a constant pressure perturbation to the working fluid. To investigate the flow characteristic change with the condition, a liquid film thickness measuring device designed by Lefebvre was installed in the injector body. From this device, the injector response characteristics were found as the shape of injector transfer function and image processing was performed to investigate the external atomization characteristics. Generally, there are two kinds of injectors, open type and closed type, for liquid swirl injector. In this study, we focused on closed type swirl injector, and investigated atomization characteristics changes with the excitation, and conducted further studies to found the causes of peak in the swirl injector.

노후 기계식 인젝터의 분무특성 연구

정민욱 ( Minuk Jeong ),유영수 ( Young Soo Yu ),양승호 ( Seungho Yang ),최민후 ( Minhoo Choi ),박성욱 ( Sungwook Park ) 한국분무공학회 2021 한국액체미립화학회지 Vol.26 No.3

Deteriorated agricultural diesel engines using mechanical fuel injection systems have low fuel injection pressures. And they are not equipped with an exhaust gas abatement device, so it produces a lot of exhaust gas. Remanufactured used injectors can reduce emissions because spray characteristics are improved. In addition, remanufacturing is environmentally friendly and economical compared to producing new parts. For efficient injector remanufacturing, it is necessary to conduct a comparison experiment on the spray characteristics of an used mechanical injector and a new injector of the same model. In this study, the spray characteristics of the two injectors were compared by performing an injection quantity measurement and a spray visualization experiment. As a result, the used injector had a larger injection quantity, a shorter spray tip penetration, a wider spray angle and a smaller spray area than the new injector.

Experimental Study on Simplex Swirl Injector Dynamics with Varying Geometry

Yunjae Chung,Taeock Khil,Jungsoo Yoon,Youngbin Yoon,V. Bazarov 한국항공우주학회 2011 International Journal of Aeronautical and Space Sc Vol.12 No.1

The effects of swirl chamber’s diameter and length on injector’s dynamic characteristics were investigated through an experimental study. A mechanical pulsator was installed in front of the manifold of a swirl injector which produces pressure oscillations in the feed line. Pressure in the manifold, liquid film thickness in the orifice and the pressure in the orifice were measured in order to understand the dynamic characteristic of the simplex swirl injector with varying geometry. A direct pressure measuring method (DPMM) was used to calculate the axial velocity of the propellant in the orifice and the mass flow rate through the orifice. These measured and calculated values were analyzed to observe the amplitude and phase differences between the input value in the manifold and the output values in the orifice. As a result, a phase-amplitude diagram was obtained which exhibits the injector’s response to certain pressure fluctuation inputs. The mass flow rate was calculated by the DPMM and measured directly through the actual injection. The effect of mean manifold pressure change was insignificant with the frequency range of manifold pressure oscillation used in this experiment. Mass flow rate was measured with the variation of injector’s geometries and amplitude of the mass flow rate was observed with geometry and pulsation frequency variation. It was confirmed that the swirl chamber diameter and length affect an injector’s dynamic characteristics. Furthermore, the direction of geometry change for achieving dynamic stability in the injector was suggested.

연료분무 및 연소 2 : 기계식 및 커먼레일식 디젤 인젝터의 연료 분무특성 비교

박쥰규 ( Jun Kyu Park ),이상훈 ( Sang Hoon Lee ),송진근 ( Jin Geun Song ),노현구 ( Hyun Gu Roh ),박성욱 ( Sung Wook Park ) 한국액체미립화학회 2012 한국액체미립화학회 학술강연회 논문집 Vol.2012 No.-

The purpose of this study is understanding spray characteristic of mechanical and common-rail injector. Because many parts of decrepit diesel engines are dumped even though they could be used by remanufacturing process, researches about remanufacturing engine go on recently. Especially, Fuel injection system of used mechanical diesel engine needs to be improved by applying common-rail system. Because of these reasons, comparisons of mechanical and common-rail injection characteristic should be investigated. In this study, it was revealed that spray development of common-rail injector is faster than that of mechanical injector based on same injection quantity and common-rail injector has an advantage of various injection condition because injection conditions such as injection pressure, energizing time are controlled dependently in common-rail system. Furthermore, contrary to mechanical system, injection rate could be adjusted by changing injection pressure and energizing time.

Experimental Study on Simplex Swirl Injector Dynamics with Varying Geometry

Chung, Yun-Jae,Khil, Tae-Ock,Yoon, Jung-Soo,Yoon, Young-Bin,Bazarov, V. The Korean Society for Aeronautical and Space Scie 2011 International Journal of Aeronautical and Space Sc Vol.12 No.1

The effects of swirl chamber's diameter and length on injector's dynamic characteristics were investigated through an experimental study. A mechanical pulsator was installed in front of the manifold of a swirl injector which produces pressure oscillations in the feed line. Pressure in the manifold, liquid film thickness in the orifice and the pressure in the orifice were measured in order to understand the dynamic characteristic of the simplex swirl injector with varying geometry. A direct pressure measuring method (DPMM) was used to calculate the axial velocity of the propellant in the orifice and the mass flow rate through the orifice. These measured and calculated values were analyzed to observe the amplitude and phase differences between the input value in the manifold and the output values in the orifice. As a result, a phase-amplitude diagram was obtained which exhibits the injector's response to certain pressure fluctuation inputs. The mass flow rate was calculated by the DPMM and measured directly through the actual injection. The effect of mean manifold pressure change was insignificant with the frequency range of manifold pressure oscillation used in this experiment. Mass flow rate was measured with the variation of injector's geometries and amplitude of the mass flow rate was observed with geometry and pulsation frequency variation. It was confirmed that the swirl chamber diameter and length affect an injector's dynamic characteristics. Furthermore, the direction of geometry change for achieving dynamic stability in the injector was suggested.

충돌형 분사기의 동특성 실험연구

김지욱(Jiwook Kim),정연재(Yunjae Chung),이인규(Ingyu Lee),윤영빈(Youngbin Yoon) 한국추진공학회 2012 한국추진공학회 학술대회논문집 Vol.2012 No.11

로켓의 연소불안정과 관련되어 분사기의 동특성을 연구하는 일은 중요하다. 와류형 분사기의 동특성에 대해서는 많은 연구가 이루어졌지만 충돌형 분사기의 동특성에 대해서는 알려진 바가 거의 없다. 따라서 본 연구에서는 충돌형 분사기의 동특성을 규명하기 위해 이에 관한 실험을 수행하였으며 동적 거동을 생성시키기 위해 특별히 제작된 압력섭동기(mechanical pulsator)가 사용되었다. 가진주파수와 매니폴드 압력의 여러 조건 하에서 게인(gain)과 위상차(phase difference)를 분석하였고 주파수는 5,10, 15 Hz의 낮은 영역에 맞춰졌다. 제트 속도를 결정하기 위한 방법에 대해 논의하였으며 실험과정 중에 나타난 특정현상이 클라이스트론(Klystron) 효과와 관련이 있는 것으로 판단되어 이에 대해 고려하였다. Research on dynamic characteristics of injectors gives us insight for preventing combustion instability in a rocket engine. While lots of studies have been done about swirl injectors‘ dynamic characteristics, little is known about impinging jet injectors’ dynamic characteristics. For this reason, this study was aimed to reveal the dynamic characteristics of an impinging jet injector based on experiment using a hydraulic mechanical pulsator. Gain, which is the relationship between input pressure and output value(pressure or velocity) was analyzed with the frequency and manifold pressure change. Pulsating frequency was chosen in the low range: 5, 10, 15 Hz. As a background work, Methods to determine the jet velocity were discussed. Klystron effect was also considered as a factor of this experiment.

Numerical analysis and simulation of an impulse driven piezoelectric needle-free jet injector

Mojiz Abbas Trimzi,함영복,안병철,박중호,윤소남 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.8

Transdermal drug delivery using needle free jet injections entails ejection of a liquid drug through a fine nozzle at elevated pressure, thus generating a narrow high-velocity fluid jet readily penetrable into skin and tissue. The idea of a simple and compact piezoelectric powered needle free injector (NFI) is introduced in this article, which offers electric control of injection volume in microliters. An impulse of up to 3500 N-s or more is generated by the multilayer piezoelectric actuator to drive the needle-free injector. The governing equations for the force and mass balance over the syringe plunger were derived to represent the driving mechanism for a compact needlefree injector. Furthermore, simulation was carried out to witness the effect of variation in parameters like impulse force, nozzle diameter and nozzle length on the injection dynamics, and the results prove the dependence of injection characteristics on aforementioned parameters, respectively. Finally, the specifications for fabrication of 10 μl volume delivering piezoelectric-impulse driven needle-free injector were obtained through analysis of multiple simulation results.

모형 연소기의 연소 불안정성 연구용 섭동 장치의 기능 검증 및 분석

민용호(Yongho Min),손채훈(Chae Hoon Sohn) 한국추진공학회 2012 한국추진공학회 학술대회논문집 Vol.2012 No.5

본 연구에서는 연소실 내의 압력섭동에 의해 발생되는 연소 불안정 상황을 모사하기 위한 시험 도구로서 섭동장치를 제작하였고, 이에 대한 성능 실험을 수행하였다. 공급되는 산화제의 유동의 흐름을 조절하여 교란을 발생시켜 인위적인 섭동을 유발할 수 있는 디스크 형태의 섭동 발생 장치를 제작하고 특성을 파악하였다. 디스크의 회전에 따라 주파수를 조정하여 모델 연소실내의 공진 주파수와의 동조가 가능하였다. 압력센서를 이용하여 섭동의 크기를 파악할 수 있었다. 따라서 설계된 섭동 장치는 연소 불안정 연구에 활용될 수 있을 것으로 판단된다. A mechanical pulsator is manufactured for study of combustion instabilities in a model chamber with impinging-jet injectors. Artificial disturbance is generated by the device and thereby, artificial instability can be examined experimentally. A sample F(fuel)-O(dxidizer)-O-F impinging-jet injector is adopted for the test. The model chamber was designed based on the methodologies proposed in the previous work regarding geometrical dimensions and operating conditions. Pressure fluctuation data, which is obtained from the dynamic pressure transducers installed in combustion chamber, is analyzed.

충돌형 분사기의 동특성 실험연구

김지욱(Jiwook Kim),정연재(Yunjae Chung),이인규(Ingyu Lee),윤영빈(Youngbin Yoon) 한국추진공학회 2013 한국추진공학회지 Vol.17 No.5

Research on dynamic characteristics of injectors gives us insight for preventing combustion instability in a rocket engine. While lots of studies have been done about swirl injectors‘ dynamic characteristics, little is known about impinging jet injectors’ dynamic characteristics. For this reason, this study was aimed to reveal the dynamic characteristics of an impinging jet injector based on experiment using a hydraulic mechanical pulsator. Gain, which is the relationship between input pressure and output value(pressure or velocity) was analyzed with the frequency and manifold pressure change. Pulsating frequency was chosen in the low range: 5, 10, 15 Hz. As a background work, Methods to determine the jet velocity were discussed. Klystron effect was also considered as a factor of this experiment.

단일 전단 동축 분사기를 가지는 GH₂/GO₂ 로켓 연소기의 고해상도 수치해석

정승민(Seung-Min Jeong),엄재령(Jae-Ryeong Um),최정열(Jeong-Yeol Choi) 한국추진공학회 2018 한국추진공학회지 Vol.22 No.6

In this study, a series of CFD analyses were carried out for a hydrogen rocket combustor with a single shear coaxial injector. A hybrid RANS/LES approach was used for the turbulent combustion analysis with a two-dimensional axisymmetric configuration. Three reaction mechanisms, three spatial discretization methods, and three levels of grid resolution were compared to determine an appropriate CFD approach. The performance of the CFD prediction were investigated by comparing the wall heat flux with experimental data. Investigation of the flow field results provides an insight into the characteristics of the turbulent reacting flow of a rocket combustor with a shear coaxial injector.