• Title/Summary/Keyword: Nozzle Pressure

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Measurement and Evaluation of Cross-talk Effects in Multi-nozzle Inkjet Head (다중 노즐 잉크젯 헤드의 상호 간섭 측정 및 평가)

  • Kwon, Kye-Si;Kim, Jin-Won
    • Journal of the Korean Society for Precision Engineering
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    • v.28 no.1
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    • pp.73-79
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    • 2011
  • Inkjet printhead may have a lot of nozzles to increase productivity as a manufacturing tool. So, the uniformity of jetting performance among a lot of nozzles has been one of the key issues in inkjet technology In this study, we investigated the cross-talk effect which should be reduced for uniform jetting performance among a lot of nozzles. Due to the cross-talk, the jetting performance of a nozzle can be affected when neighboring nozzles are firing. For experimental study, we used commercial inkjet head SE-128 from Dimatix. To understand the cross-talk effect of SE-128 head, we measured the change in jetting speed of a nozzle when neighboring nozzles are jetting. The measured jetting speed was compared to the case of one nozzle jetting. Also, we used laser vibrometer to measure change in pressure wave due to cross-talk. As a result of the cross-talk, the jetting speed can become faster or sometimes slower depending on firing nozzle location. If the all nozzle are jetting, the jetting speed of a nozzle became slower because the pressure wave for jetting is reduced.

A Study on the Flow Characteristics in Double Coaxial Pipe Jets (동축이중원관 분류에 있어서의 유동 특성에 관한 연구)

  • Shin, C.H.;Kim, K.H.
    • Journal of ILASS-Korea
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    • v.1 no.4
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    • pp.46-53
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    • 1996
  • The present study is aiming at improving the performance of main nozzle of an air jet loom with a modified reed and auxiliary nozzles. The double coaxial pipe jets consisting of a central air jet and an annular air jet have been experimentally investigated. The duter jet has a potential core and a constant velocity. The inner jet through an inner long pipe is induced by the subatmospheric pressure near the inner nozzle edge, and the jet velocity of an inner pipe is always lower than that of a outer pipe. The static pressures of the main nozzle over a wide range of the nozzle tank pressure were measured, and the nozzle velocity and Mach numbers were analytically calculated. Experiment81 results indicate that the critical condition of Mach number of unity to occur at the two positions in a main nozzle; one of them is the needle tip and the other is the acceleration tube exit An increase in the tank pressure causes the critical throat condition to occur at the two positions above. The velocity of acceleration-tube exit is maximum at the critical length L* and flow patter in acceleration-tube over critical lengh remains unstable.

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A Numerical Analysis of Transonic Flows in an Axisymmetric Main Nozzle of Air-Jet Loom (에어제트직기 주 노즐내 천음속 유동의 수치 해석적 연구)

  • Oh T. H.;Kim S. D.;Song D. J.
    • 한국전산유체공학회:학술대회논문집
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    • 1998.05a
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    • pp.168-173
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    • 1998
  • A numerical analysis of axisymetric backward facing step main nozzle flow in air jet loom has been accomplished. To obtain basic design data for an optimum main nozzle for an air-jet loom and to predict the transonic/supersonic flow, a characteristic based upwind flux difference splitting compressible Navier-Stokes method has been used. The wall static pressure of the main nozzle and the flow velocity changes in the nozzle tube were analyzed by changing air tank pressures and acceleration tube lengths. The flow inside the nozzle experiences double choking one at the needle tip and the other at the acceleration tube exit at tank pressures over $4kg_f/cm^2$. The tank pressure $P_t$ leading to the critical condition depends on the acceleration tube length; i.e, $P_t$ is higher for longer acceleration tubes. The $P_t$ value required to bring the acceleration tube exit to the critical condition is nearly constant regardless of acceleration tube length. The round needle tip shape might lead to less total pressure loss when compared with step shape.

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Injection Flow Rate Improvement of Injectors for DME Common-rail Systems (DME 커먼레일 시스템을 위한 인젝터 분사 유량 개선)

  • Lee, G.S.;Shin, S.S.;Park, J.H.
    • Journal of ILASS-Korea
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    • v.18 no.1
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    • pp.55-60
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    • 2013
  • In this study, injection flow rates and material of the solenoid sealing of the injectors were improved for the development of a di-methyl Ether(DME) common-rail system. To deliver the same amount of energy provided by injection pressure of diesel $P_{inj}$ = 160 MPa, the DME injectors need to have larger diameter of nozzle hole and more No. of hole at low injection pressure of $P_{inj}$ = 40~50 MPa. The simplified nozzle flow model, which takes account of nozzle geometry and injection condition, was employed in order to design the concept of a injector nozzle such as No. of hole, diameter of hole and diameter of needle seat, etc. Injection amount and rate were tested by diesel and DME test stand. As a result, the diameter of nozzle hole were enlarged by 0.25 mm. The diameter of the orifice in the high pressure line was increased by 1.0 mm to maintain hydraulic force in the nozzle. The material of the solenoid sealing was changed to HNBR, which was strong against the corrosive. Experimental results showed that the injection amount of the DME injector drastically increased by 191.9% comparison to that of diesel at $P_{inj}$ = 40 MPa.

Study on the frequency of self-excited pulse jet

  • Wang, Jian;Li, Jiangyun;Guan, Kai;Ma, Tianyou
    • International Journal of Fluid Machinery and Systems
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    • v.6 no.4
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    • pp.206-212
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    • 2013
  • Self-excited pulse jet is a specific nozzle with a closed chamber which can change a continuous jet into a pulse one. Energy of the pulse jet can be output not only unevenly but also with multifrequency. With the peak pressure of pulse jet, the hitting power would be 2~2.5 times higher than that of continuous jet. In order to reveal the correlation between the self-excited pulse frequency and nozzle diameter ratio, nozzle spacing and operating pressure, the model of 3D unsteady cavitation model has been used. We found that with the same nozzle structure parameters and the different operating pressure, the self-excited frequency and the width of peak crest are different, but the wave profiles are similar. With FFT, we also found that the less bandwidth of amplitude in low frequency range will lead to the wider wave crest of outlet velocity in its time domain, and the larger force of the strike will be gained. By studying the St of self-excite nozzle, not only the frequency of a certain nozzle can be predicted, but also a nozzle structure with a certain frequency can be designed.

An Investigation on the Spray Characteristics of DME with Variation of Nozzle Holes Diameter using the Common Rail Fuel Injection System (인젝터 노즐 홀 직경의 변화에 따른 DME 커먼레일 연료 분사 시스템의 분무 특성에 관한 연구 II)

  • Lee, Sejun;Lim, Ocktaeck
    • Transactions of the Korean Society of Automotive Engineers
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    • v.21 no.4
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    • pp.1-7
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    • 2013
  • DME spray characteristics were investigated about varied ambient pressure and fuel injection pressure using the DME common rail fuel injection system when the nozzle holes diameter is varied. The common rail fuel injection system with DME cooling system was used since DME has properties of compressibility and vaporization in atmospheric temperature. The fuel injection quantity and spray characteristics were measured. The spray analysis parameters were spray shape, penetration length, and spray angle at six nozzle holes. Three types of injector were used, the nozzle holes diameter were 0.166 mm (Injector 1), 0.250 mm (Injector 2), and 0.250 mm with enlargement of orifice hole from 0.6 mm to 1.0 mm (Injector 3). The fuel injection pressure was varied by 5MPa from 35 to 70MPa when the ambient pressure was varied 0, 2.5, and 5MPa. When using Injector 3 in comparison to the others, the DME injection quantity was increased 1.69 ~ 2.02 times. Through this, it had the similar low heat value with diesel which was injected Injector 1. Among three types of injector, Injector 3 had the fastest development velocity of penetration length. In case of spray angle, Injector 2 had the largest spray angle. Through these results, only the way enlargement the nozzle holes diameter is not the solution of DME low heat value problem.

Thermal stress intensity factor solutions for reactor pressure vessel nozzles

  • Jeong, Si-Hwa;Chung, Kyung-Seok;Ma, Wan-Jun;Yang, Jun-Seog;Choi, Jae-Boong;Kim, Moon Ki
    • Nuclear Engineering and Technology
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    • v.54 no.6
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    • pp.2188-2197
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    • 2022
  • To ensure the safety margin of a reactor pressure vessel (RPV) under normal operating conditions, it is regulated through the pressure-temperature (P-T) limit curve. The stress intensity factor (SIF) obtained by the internal pressure and thermal load should be obtained through crack analysis of the nozzle corner crack in advance to generate the P-T limit curve for the nozzle. In the ASME code Section XI, Appendix G, the SIF via the internal pressure for the nozzle corner crack is expressed as a function of the cooling or heating rate, and the wall thickness, however, the SIF via the thermal load is presented as a polynomial format based on the stress linearization analysis results. Inevitably, the SIF can only be obtained through finite element (FE) analysis. In this paper, simple prediction equations of the SIF via the thermal load under, cool-down and heat-up conditions are presented. For the Korean standard nuclear power plant, three geometric variables were set and 72 cases of RPV models were made, and then the heat transfer analysis and thermal stress analysis were performed sequentially. Based on the FE results, simple engineering solutions predicting the value of thermal SIF under cool-down and heat-up conditions are suggested.

A Theoretical Study on Flow and Pressure Variation Characteristics of Fuel Supply System in Diesel Engine (디젤엔진 연료계통의 유동 및 압력 변동특성에 관한 이론적 연구)

  • 송치성
    • Journal of Advanced Marine Engineering and Technology
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    • v.17 no.3
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    • pp.12-23
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    • 1993
  • Combustion phenomenon in diesel engine is mainly governed by characteristics of fuel injection and fuel spray system affected by its dimensions and operating condition. Fuel supply system is consisted of fuel injection pump, high pressure pipe and injection nozzle. In order to develope the more economical diesel fuel injection system, it is in need to carryout the fairly wide range experiments, which is quite impossible. Therefore, theoretical analysis for the numberous parameters is powerful method in this case. In the present study, equations of continuity of fuel oil in fuel injection system are solved to obtain the flow and pressure variation in diesel fuel system affected by injection pump speed, plunger diameter, pipe length and nozzle opening pressure.

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A Study on the Development of High Pressure Holder for Machining (절삭가공용 고압분사 홀더 개발에 관한 연구)

  • Yi, Chung-Seob;Jeong, In-Guk;Suh, Jeong-Se;Chung, Sang-Wan
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.11 no.6
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    • pp.55-61
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    • 2012
  • In this study, it was grasped to the flow characteristics of injection nozzle installed in high pressure holder for improving productivity. Chip curling occurred during cutting process for difficult-to-cut material detracts product qualities and productivity. Among of method preventing the phenomenon, high pressure injecting cutting oil is an alterative. In this study, the optimal nozzle was designed by CFD method and it was conducted to analyse on the effect of high pressure injection on chip shape generated during cutting process and wear of insert by experimental method. As the result, it could be confirmed that high pressure injection is favorable for preventing chip curling and insert from wearing.

Plume Structure Analysis of an Axisymmetric Supersonic Micro-nozzle at the Various Pressure Ratios (압력비가 변할 때 축대칭 초음속 노즐의 플룸 구조 해석)

  • Kwon, Soon-Duk;Kim, Sung-Cho;Kim, Jeong-Soo;Choi, Jong-Wook;Kim, Yong-Sseok
    • Proceedings of the KSME Conference
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    • 2007.05b
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    • pp.2862-2867
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    • 2007
  • The steady non-reacted compressible flow field in a symmetric micro-thruster, which is used for the accurate attitude control of a satellite, is analyzed varying the nozzle pressure ratio (NPR) to investigate the plume characteristics. The nozzle throat diameter is 0.06 inch and the area ratio is 56. The recirculation region is found just behind the normal shock at the several NPRs due to the locally adverse pressure gradient along the nozzle centerline when the environmental pressure is atmospheric. This phenomenon, the cause of flow loss, is similar to the flow behind a blunt body. As NPR increases the location of Mach disk, characteristics of the normal shock, moves downstream and its strength increases. The Mach number distribution appears in a wave-type patter after the normal shock because oblique shocks are reflected on the shock boundaries especially when NPRs are very high.

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