• Title/Summary/Keyword: cavity pressure

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A Study on the Expansion Cavity Pipe for Performance Improvement of Exhaust System in Automotive (자동차 배기성능개선을 위한 확장형 공동파이프에 관한 연구)

  • Son, Sung-Man;Park, Kyoung-Suk
    • Transactions of the Korean Society of Automotive Engineers
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    • v.17 no.5
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    • pp.1-6
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    • 2009
  • The temperature of exhaust gas was raised by increasing of engine movement on developing engine. Thermal of high temperature and pressure reverse in bellows, because of increasing of engine movement and the thermal performance of converter in combustion. As a result, thermal loss is increased and thermal efficiency is decreased rapidly in bellows, it can occur to damage in mechanical structure. In this study, it was necessary to analyze back pressure performance and thermal characteristic on driving condition in exhaust system. It was adapted braid type bellows and straight type exhaust pipe. It was compared with curve type exhaust pipe for lay-out on considering to design of exhaust system. It was necessary to improve thermal characteristic and back pressure performance so that expansion cavity pipe(ECP) was installed between bellows and catalyst convert. Not only decreasing back pressure was solved but also thermal characteristic problems in exhaust pipe because of increasing capacity. According to this study, the basis of data is presented when new exhaust system is designed.

Scattering Sound by a Flexinble Cylindrical Cavity (매질이 다른 무한 실린더에 의한 음의 산란)

  • Kim, Yu-Man;Lee, Byung-Ho
    • The Journal of the Acoustical Society of Korea
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    • v.7 no.4
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    • pp.117-126
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    • 1988
  • The pressure waves scattered by an infinite cylindrical cavity filled with air in a h0mogeneous medium have been calculated for the incident plane pressure waves. For ka = 1/2, 1, 2, 4, 10 and 20, the scattered pressure waves are plotted., where k is the wave number and a is the radius of the cylindrical hole. As an indicator of the directivity of the scattering pattern, we have defined the angle at which the magnitude of the scattered pressure wave decreases by a half(6 dB) with respect to that of the forward peak scattered pressure wave. This angle depends strongly on the values of ka and the distance r, and the angle can be used for the detection of the location and the size of the cavity in a homogeneous medium.

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Performance Enhancement Study Using Passive Control of Shock-Boundary Layer Interaction in a Transonic/Supersonic Compressor Cascade (천음속/초음속 압축기 익렬에서 Shock-Boundary Layer 상호작용의 수동적 제어에 의한 성능 향상 연구)

  • Kim, Sang-Deok;Gwon, Chang-O;Sa, Jong-Yeop
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.20 no.9
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    • pp.2944-2952
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    • 1996
  • In this paper the CSCM type upwind flux difference splitting Navier-Stokes method has been applied to study the ARL-SL19 transoni $c^ersonic compressor cascade flow. First, the general characteristics of baseline cascade flow were analyzed. At freestream Mach n.1.612 and exit/inlet pressure ratio 2.15, the results from current laminar flow were compared well in suction surface with the experiment; however, not well in pressure surface. Second, numerical study of the transoni $c^ersonic compressor cascade flow demonstrated the effectiveness of a passive control by the various size cavities. A cavity under the shock foot point at the suction surface of the blades was used as a passive control. The passive control of shock-boundary layer interaction by a cavity reduced total pressure losses. The effect of cavity length and depth was studied. The total pressure loss was reduced by about 10% and the isentropic efficiency was improved slightly. The effect of cavity depth in current study(d/l = 0.05, 0.02) was not found strong. Further adequate turbulence modeling and TVD schemes would help to capture the shock more accurately and increase the effectiveness of the current shock-boundary layer interaction study using upwind flux difference splitting computational methods.thods.

Computational analysis of compressibility effects on cavity dynamics in high-speed water-entry

  • Chen, Chen;Sun, Tiezhi;Wei, Yingjie;Wang, Cong
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.11 no.1
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    • pp.495-509
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    • 2019
  • The objective of this study is to analyze the compressibility effects of multiphase cavitating flow during the water-entry process. For this purpose, the water-entry of a projectile at transonic speed is investigated computationally. A temperature-adjusted Tait equation is used to describe the compressibility effects in water, and air and vapor are treated as ideal gases. First, the computational methodology is validated by comparing the simulation results with the experimental measurements of drag coefficient and the theoretical results of cavity shape. Second, based on the computational methodology, the hydrodynamic characteristics of flow are investigated. After analyzing the cavitating flow in compressible and incompressible fluids, the characteristics under compressible conditions are focused upon. The results show that the compressibility effects play a significant role in the development of cavitation and the pressure inside the cavity. More specifically, the drag coefficient and cavity size tend to be larger in the compressible case than those in the incompressible case. Furthermore, the influence of entry velocities on the hydrodynamic characteristics is investigated to provide an insight into the compressibility effects on cavitating flow. The results show that the drag coefficient and the impact pressure vary with the entry velocity, and the prediction formulas for drag coefficient and impact pressure are established respectively in the present study.

The Effect of Oil Supply Pressure on the Performance of Vapor Cavitated Short Squeeze Film Dampers (증기 공동현상이 발생하는 무한 소폭 스퀴즈 필름 댐퍼 성능과 오일 공급압력의 영향)

  • Jung, Si-Young
    • Tribology and Lubricants
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    • v.24 no.3
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    • pp.147-153
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    • 2008
  • The effect of oil supply pressure on the performance of vapor cavitated short squeeze film dampers is examined. Vapor cavitation is characterized by film rupture occurring as a result of evaporating oils. The pressure of vapor cavity in the film is almost zero in absolute pressure and nearly constant. Pan's model about the shape of vapor cavity is utilized for studying the effect of vapor cavitation on the damping capability of a short squeeze film damper. As the level of oil supply pressure is increasing, vapor cavitation is suppressed so that the direct damping coefficient increases and the cross coupled damping coefficient decreases. Futhermore, the analysis of the unbalance responses of a rigid rotor supported on cavitated squeeze film dampers shows that a significant reduction in rotor amplitude and force transmissibility is possible by controlling the oil supply pressure into short squeeze film dampers.

Parametric Study of Subscale Ejector for Pressure Recovery of Chemical Lasers (화학레이저 압력회복을 위한 축소형 이젝터의 성능변수)

  • Kim Sehoon;Kim Hyungjun;Kwon Sejin
    • Proceedings of the KSME Conference
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    • 2002.08a
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    • pp.135-138
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    • 2002
  • High-speed ejection of burnt gases from the resonator cavity is essential for performance optimization of the chemical laser system. Additionally, to maintain the population of lasing species at a level for maximum optical power, the pressure within the cavity must be of order of 10 torr. In the present study, a small-scale ejector was designed and built for parametric study of its performance. High-pressure air was used as a motive gas. Measurements include schlieren visualization and pressure distribution trace near the ejector nozzle and along the diffuser downstream of the ejector. preliminary tests showed performance of the ejector is a function of parameters including mass flow rate and stagnation pressure of the motive gas, ejector nozzle area ratio, throat area of the diffuser downstream of the ejector.

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Horseshoe Vortices variation around a Circular Cylinder with Upstream Cavity (상류 캐비티로 인한 실린더 주위의 유동장 변화)

  • Kang, Kyung-Jun;Kim, Dong-Beum;Song, Seung-Jin
    • Proceedings of the KSME Conference
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    • 2008.11b
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    • pp.2625-2630
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    • 2008
  • Horseshoe vortices are formed at the junction of an object immersed in fluid-flow and endwall plate as a result of three-dimensional boundary layer separation. This study shows preliminary results of the kinematics of such horseshoe vortices around a circular cylinder with a cavity (slot) placed upstream to disturb the primary separation line. Through the cavity, no mass flow addition (blowing) or reduction (suction) is applied. The upstream cavity weakens the adverse pressure gradient before the cavity. With the upstream cavity, a single vortex is found to form immediately upstream of the cylinder whereas a typical two vortex system is observed in the absence of the cavity. Furthermore, the strength of the single vortex tends to be reduced, resulting from the interaction with the separated flow convecting directly towards the leading edge of the cylinder.

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A Computational Study of the Supersonic Cavity Flow (초음속 Cavity 유동에 관한 수치해석적 연구)

  • Jung Sung-Jae;Gwak Jong-Ho;Kim Heuy-Dong
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2004.10a
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    • pp.23-26
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    • 2004
  • A computational analysis has been conducted to investigate the detailed flow structure inside a supersonic cavity. The free stream Mach number and Reynolds number are 1.83 and $6.02\times10^5$ respectively. In the present study, the depth and width of the cavity are changed to investigate the effect of the cavity dimensions. A fully implicit finite volume scheme is applied to solve the three-dimensional, steady, unsteady, compressible, Navier-Stokes equations. The computed results are validated with the previous experimental data available. The present computation provides reasonable predictions of the cavity flow, compared with experimental results. The obtained results show that a shock wave is generated in front of the downstream edge of the cavity and the dominant frequencies of the pressure oscillations inside the cavity were obtained.

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Comparison of Molding Characteristics for Multi-cavity Molding in Conventional Injection Molding and Injection Compression Molding (다수 개 빼기 성형에서 일반사출성형과 사출압축성형의 성형특성 비교)

  • Lee, Dan Bi;Nam, Yun Hyo;Lyu, Min-Young
    • Polymer(Korea)
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    • v.38 no.2
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    • pp.144-149
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    • 2014
  • Large residual stresses are remained in the conventional injection molded products because of the high cavity pressure in packing phase during injection molding process. Conventional injection molding (CIM) invokes distribution of cavity pressure and it has a limitation to obtain product with uniform physical property. Multi-cavity conventional injection molding contains quality deviation among the cavities since flow imbalance occurs during filling phase. Injection compression molding (ICM) is adopted to overcome these limitations of CIM. In this study, molding characteristics of CIM and ICM have been investigated using multi-cavity injection mold. Researches were performed by both experiment and computer simulation through observations of birefringence for transparent resins, polycarbonate and polystyrene in CIM and ICM. As a result, low and uniform birefringence and mold shrinkage were showed in the specimens by ICM that could give a uniform cavity pressure. Deviation of physical property among the specimens in multi-cavity mold shown in CIM was significantly reduced in the specimens by ICM. Through this study it was concluded that the ICM in multi-cavity molding was valid for molding products with uniform property in an individual cavity and also reduced property deviation among the cavities.

The Whole Region Pressure Measurement of Cavity Downstream using PSP Technique (PSP를 이용 다양한 공동 후류의 전역적 압력분포 측정)

  • Seo, Hyung-Seok;Oh, Ju-Young;Jeon, Young-Jin;Lee, Jae-Woo;Byun, Yung-Hwan
    • Journal of the Korean Society of Propulsion Engineers
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    • v.11 no.6
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    • pp.50-57
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    • 2007
  • Pressure Sensitive Paint(PSP) means a reacting paint in pressure. PSP can measure continuous pressure field by analyzing the oxygen quantity using optical method. The surface pressure of down stream after the sonic jet that injected transversely into the supersonic freestream was measured by PSP technique. Moreover the effect of various rectangular shaped cavities in front of the jet was measured by PSP technique. A comparison of the PSP results with conventional pressure tap and CFD indicates good agreement. Until now, the results of numerical analysis were compared with the discrete points such as the results of pressure tap. In this study, the whole region pressure was measured using PSP technique and its results were similar to CFD. Therefore, the flow phenonenon of cavity downstream was clearly grasped.