• Title/Summary/Keyword: Mechanical pulsator

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Spray Characteristics of Simplex Swirl Injector with Low Hydrodynamic Disturbance Generated by Pressure Fluctuation in Feed Line (축방향 압력섭동에 의해 발생되는 저주파 수력학적 교란이 단일 스월 인젝터에 미치는 영향 분석)

  • Khil, Tae-Ock;Kim, Sung-Hyuk;Kim, Hyeon-Sung;Yoon, Young-Bin
    • Journal of ILASS-Korea
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    • v.12 no.1
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    • pp.1-10
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    • 2007
  • The low frequency combustion instability phenomena generated by pressure drop oscillation such as propellant shake in feed line are studied. To generate the flowrate oscillation by the pressure pulsation up to 400Hz without flow discontinuities and cavitations, a hydrodynamic mechanical pulsator of rotating disk type was produced. Injection pressure conditions are 5, 7 and 9 bar and pressure fluctuation frequency conditions are 0, 4, 6 and 8 Hz. When the injection pressure was oscillated by a mechanical pulsator, the spray shape was pulsated regularly. During the pulsated state of the spray with a mechanical pulsator, the spray characteristics, such as spray angle and liquid film thickness in orifice exit, were measured and compared with those in steady state without a mechanical pulsator. Though the mean injection pressure was fixed in the steady and fluctuating state, there were some differences in all measured values, i.e. liquid film thickness and spray cone angle, between both states.

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Experimental Study on Dynamic Characteristics of an Impinging Jet Injector (충돌형 분사기의 동특성 실험연구)

  • Kim, Jiwook;Chung, Yunjae;Lee, Ingyu;Yoon, Youngbin
    • Journal of the Korean Society of Propulsion Engineers
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    • v.17 no.5
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    • pp.86-94
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    • 2013
  • 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.

A Development of A Gas Mechanical Pulsator (압력 섭동 장치 설계/제작 및 검증시험)

  • Kim, Tae-Woan;Hwang, Oh-Sik;Ko, Young-Sung;Jung, Se-Yong
    • Journal of the Korean Society of Propulsion Engineers
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    • v.13 no.3
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    • pp.50-57
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    • 2009
  • A gas mechanical pulsator is developed for the study of combustion instabilities in various combustors such as LRE combustor. First, it shows that the mass flow rates and the perturbation frequencies can be successively controlled by the inlet pressure and the rotating speed of a rotating disk with many holes. Second, the device is used as an acoustic amplification source as a substitute for the speaker in the previous acoustic tests and its results show almost the same resonant frequency and damping characteristics compared with the previous results. In conclusion, the result shows that it can be used as a substitute for a speaker in the studies of LRE combustion instabilities, which has a flow and no limitation of amplification, and a device for making a perturbation source in gas flow.

Simulation-based Stamping Process Design for a Pulsator Cover of a Washing Machine with Ferritic Stainless Steel Sheet (페라이트계 스테인리스 판재 적용을 위한 세탁기 회전날개의 전산 해석기반 성형공정설계)

  • Kim, Se-Ho;Kim, Kee-Poong
    • Journal of the Korean Society for Precision Engineering
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    • v.28 no.3
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    • pp.349-356
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    • 2011
  • This paper replaces a conventional austenitic stainless steel sheet to a ferritic stainless steel for the cost reduction of a pulsator cover of a washing machine. However, ferritic stainless steel has poor formability in comparison with austenitic one. The low formability of ferritic steel results in problems during stamping such as fracture, wrinkling, shape inaccuracy and so on. Design modification of the stamping tool is carried out with the aid of the finite element analysis for multistage stamping process of the pulsator cover. The simulation results show that fracture occurs on top of the product while wrinkles are generated by the excess metal near the wing part. Modification of the initial stamping die is performed to improve metal flow and to eliminate problems during the stamping process. Simulation with the modified design fully demonstrates that safe forming is possible without inferiorities.

The Effects of Pulsator Washing Machine on Joints Torques and Muscles Strengths Considering Height of Outside Machine and Depth of Inside Drum for Average Height Users (투입구 높이 및 내부 드럼 깊이를 고려한 펄세이터 세탁기 사용시 평균신장 사용자의 관절 토크 및 근력에 미치는 영향)

  • Kim, Seong Guk;Cho, Young Kuen;Lee, Nam Gi;You, Joshua Sung Hyun;Lim, Dohyung;Kim, Han Sung;Ko, Chang-Yong
    • Journal of Biomedical Engineering Research
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    • v.33 no.4
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    • pp.184-193
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    • 2012
  • Many studies have reported that housework done using household appliances may affect biomechanical characteristics of the musculoskeletal system. The purpose of this study was to investigate the effects of housework done using a pulsator washing machine on joints and muscles. We calculated joint torques and muscle strengths on the basis of an experimental/virtual three-dimensional motion analysis for six healthy females using the pulsator washing machine at different heights (H) and depths (D) of the inside drum (H (mm){\times}D (mm), Trial1: $962.5{\times}609.4$, Trial2: $962.5{\times}624.4$, Trial3: $982.5{\times}644.4$, Trial4: $995.5{\times}642.4$, Trial5: $1015.5{\times}677.4$). The joint torques and muscle strengths tended to be considerably different during torso flexion in the sagittal plane for all the trials. The maximum joint torques for the thoracic vertebra, left ankle, and right shoulder measured in Trial4 were significantly higher than those measured in the other trials (p < 0.05); in addition, those for the thoracic vertebra and both ankles measured in Trial5 were significantly higher than those measured in the other trials (p < 0.05). The maximum muscle strengths for the left trapezius muscle and both tibialis anterior muscles measured in Trial5 were significantly higher than those measured in the other trials (p < 0.05). These results indicate that housework done using a pulsator washing machine may affect joint torques and muscle strengths, and these effects are dependent on the height and/or depth of the inside drum of the pulsator washing machine.

Verification and Analysis of Characteristics of Mechanical Pulsation for Combustion Stability Study in a Model Chamber (모형 연소기의 연소 불안정성 연구용 섭동 장치의 기능 검증 및 분석)

  • Min, Yong-Ho;Sohn, Chae-Hoon
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2012.05a
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    • pp.28-30
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    • 2012
  • 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.

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Experimental Study on Simplex Swirl Injector Dynamics with Varying Geometry

  • Chung, Yun-Jae;Khil, Tae-Ock;Yoon, Jung-Soo;Yoon, Young-Bin;Bazarov, V.
    • International Journal of Aeronautical and Space Sciences
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    • v.12 no.1
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    • pp.57-62
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    • 2011
  • 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.

Dynamic Modeling and Analysis of the Washing Machine System with an Automatic Balancer (자동 밸런서를 갖는 세탁기 시스템의 동력학 모델링 및 해석)

  • Oh, Hyuck-Jin;Lee, U-Sik
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.28 no.8 s.227
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    • pp.1212-1220
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    • 2004
  • The structural unbalance mass and laundry are the important sources of the severe vibrations of automatic washing machines. In this paper, a mathematical model is developed for the dynamic analysis of the vertical axis automatic washing machines of pulsator-type. In the model, the rigid body motion of tub assembly is represented by six degrees of freedom and the dynamics of automatic hydraulic balancer is represented by one degree of freedom. The fundamental elastic modes of the tub shell and four suspension bars are also taken into account in the mathematical model, based on analytical and experimental modal analysis results. The 12 degrees of freedom equations of motion are derived by using the Lagrange's equations and the present dynamic model is evaluated by comparing the numerical simulation results with experimentally measured data.

Study on Phase-Amplitude Characteristics in a Simplex Swirl Injector with Low Frequency Range (저주파 압력섭동 범위 내에서의 단일 스월 인젝터의 진폭-위상 특성 연구)

  • Khil, Tae-Ock;Chung, Yun-Jae;Yoon, Young-Bin
    • Journal of the Korean Society of Propulsion Engineers
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    • v.14 no.2
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    • pp.19-28
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    • 2010
  • Generally, combustion instability is generated by the mutual coupling between the heat release and the acoustic pressure in the combustor. On the occasion, the acoustic pressure generates the oscillation of the mass flow rate of propellant injected from injector, and this oscillation again affects combustion in the combustor. So, the dynamic characteristics of the injector have been studied to control combustion instability using injector itself in Russia from 1970's. In order to study injector dynamics, a mechanical pulsator for forced pressure pulsation is produced and the method to quantify the mass flow rate of the propellant that is oscillating at the exit of the injector is developed. With the pulsator and the method, pulsating values of the mass flow rate, pressure, liquid film thickness, and axial velocity generated at the exit of the simplex swirl injector are measured in real time. And phase-amplitude characteristics of each parameter are analyzed using these pulsating values acquired at the exit of the simplex swirl injector.

A Study on Dynamic Characteristics of Gas Centered Swirl Coaxial Injector Varying Tangential Inlet Diameter with Liquid Pulsation (기체 중심 동축형 분사기의 접선방향 유입구 지름 변화에 따른 액체 가진 연구)

  • Oh, Sukil;Park, Gujeong;Kim, Seongju;Lee, Hyeongwon;Yoon, Youngbin;Choi, Jeong-Yeol
    • Journal of ILASS-Korea
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    • v.22 no.2
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    • pp.62-68
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    • 2017
  • It is important to study on the combustion instability to develop liquid rocket engines for preventing lower combustion efficiency and destruction of combustion chamber. There are many researches on simplex injector with liquid pulsation to solve this problem. In real rocket engine system, however, they use coaxial injectors. Therefore, research on coaxial injector with liquid pulsation is essential. In this study, we investigate dynamic characteristics of gas centered swirl coaxial injector varying tangential inlet diameter. A mechanical pulsator was used to generate an excitation in the liquid flow, and the response characteristics of the injector were confirmed. As tangential inlet diameter increased, mass flow rates increased and spray angle decreased. As tangential inlet diamter decreased, gain decreased because the pressure fluctuation in the injector manifold rarely passed through the inlet. Additionally, it was confirmed that a sufficiently small tangential inlet served as a damper.