Initiation and propagation of shock waves in the exhaust pipe of an internal combustion engine.

Sekine, Noriaki; Matsumura, Shuji; Takayama, K.; Onodera, Osamu; Ito, Katsuhiro

doi:10.1299/kikaib.54.527

Cited by 11 publications

(5 citation statements)

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“…Fig.4 shows schlieren pictures of the impulsive waveforms taken at the same instance, where the time is taken immediately after the normal shock wave reaches the measuring point (2). Fig.4 shows schlieren pictures of the impulsive waveforms taken at the same instance, where the time is taken immediately after the normal shock wave reaches the measuring point (2).…”

Section: Resultsmentioning

confidence: 99%

“…Discharge problem of a shock wave from an open end of a duct has been associated with a variety of unsteady internal flow devices, for example, gun muzzles [ 1], diesel engine exhaust mufflers [ 2], dynamic pressure exchangers [a], pulse combustors [4], pulse jet filters [5] etc.. Very often the impulsive wave has been a major problem that restricts the performance of flow devices.…”

Section: Introductionmentioning

confidence: 99%

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Passive control of an impulsive wave using a cavity/helical vane system

et al. 1999

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Passive control of an impulsive wave using a cavity/helical vane system

et al. 1999

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“…The total energy e per unit volume of the gas can be expressed by the sum of the kinetic energy and the internal energy, as indicated by 2) is closed by the thermal equation of state of a perfect gas, pˆrR T . In the present computations, equation (2) was rewritten in a non-dimensional form by normalizing the variables with respect to atmospheric conditions and the diameter of the tube as follows:…”

Section: Computational Analysismentioning

confidence: 99%

“…When a pressure wave generated inside a duct is discharged from an open end of the duct, as would be encountered in a variety of internal ows such as gun muzzles [1], internal combustion engine exhaust muf ers [2], dynamic pressure exchangers [3], pulse combustors [4] and pulse jet lters [5], an impulsive wave forms at the exit of the duct. The impulsive wave is usually characterized by a high sound pressure level of short duration and propagates far from the duct exit [6].…”

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confidence: 99%

Weak shock reflection from an open end of a tube with a baffle plate

Kim

Kweon

Setoguchi

et al. 2003

Proceedings of the Institution of Mechanical Engineers, Part C:

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The present paper describes experimental and numerical investigations of a new boundary condition at an open end of a tube, in which a weak shock wave is discharged towards the surroundings. Experimental and computational investigations were performed on a simple shock tube with and without baffle plates. A numerical calculation was carried out for an unsteady, axisymmetric, inviscid, compressible flow. The size of baffle plate was varied in order to understand its effect on the reflection of the weak shock wave from the open end of the tube. With and without a baffle plate, the results of the experiment were in good agreement with those of numerical calculations. The results showed that an open end correction is subject to the presence of a baffle plate at the open end. An improved empirical equation for the reflection of the weak shock wave from the open end of a duct with and without a baffle plate was developed.

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“…In experimental pressure measurements using actual cars [2], it is reported that shock waves with Mach number about 1.1 are generated in the exhaust pipe, and pulsed pressure profiles are shown in the upstream side of the silencer. The pulsed shock wave is considered to be the blast wave, which is an unsteady pressure wave where the shock wave is accompanied by expansion waves.…”

Section: Introductionmentioning

confidence: 99%

Attenuation Effect of Expansion Configuration and Acoustic Material on Propagation of Blast Waves in a Duct

Ishiguro¹,

Shinkai²,

Shimamura³

et al. 2016

JFCMV

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With recent increase of cars, the noise problem has been caused by the exhaust sounds released from exhaust pipes, which consist of weak and pulsed shock waves called blast waves. To diminish the noise, a silencer is set up in front of the exhaust pipe. In the present study, reflectors were installed in the high-pressure section of the shock tube to generate blast waves, and three types of expansion region were investigated, combined with acoustic material of glass wool. The pressure decay was evaluated by transmission factor and reflection factor for the incident blast wave, together with pressure histories and high-speed Schlieren photography. As results, it was confirmed that the acoustic material greatly contributed to blast-wave attenuation: the one stage expansion model with glass wool recorded the highest decay of the peak over pressure for transmission, and other models with glass wool showed the second highest. The acoustic material also contributed to decay of reflected shock waves propagating toward an upstream duct. KeywordsBlast Wave, Shock Tube, Exhaust Noise, Decay Factor, Silencer Model, Acoustic Material * Corresponding author. M. Ishiguro et al. 80 waves.In experimental pressure measurements using actual cars [2], it is reported that shock waves with Mach number about 1.1 are generated in the exhaust pipe, and pulsed pressure profiles are shown in the upstream side of the silencer. The pulsed shock wave is considered to be the blast wave, which is an unsteady pressure wave where the shock wave is accompanied by expansion waves. In the blast wave, the pressure decays just behind the abrupt rise by a shock wave, while in the usual shock wave, the pressure is kept constant behind the pressure rise. The blast waves are generated by the explosion, and in the natural phenomena they are caused by the volcanic eruption. In this research, the blast waves are generated in a shock tube by the way shown in [3].Till now various researches have been reported about silencers of cars, models of which are classified typically into one-stage and multi-stage expansion models, by the number of partitioned chambers with diameter higher than that of the exhaust pipe. In early-stage investigations, Kanai presented theoretical equations to give attenuation characteristics of pure sound for fundamental expansion models [4], investigated attenuation characteristics of exhaust noise theoretically and experimentally, and showed that multi-stage expansion models with connecting pipes or expansion chambers filled with the acoustic material of glass wool had much efficacy [5]. Izumu, et al. investigated the attenuation effects for the noise of airflows less than 50 m/s for one-stage models with several adapters in either side of inflow or outflow duct [6]. These early-stage investigations were carried out mainly from the view point of acoustics. However, it was pointed out that a linear acoustic theory held for waves of infinitesimal pressure amplitudes, and not for waves of finite amplitudes generated in the exhaust pipe, wh...

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Initiation and propagation of shock waves in the exhaust pipe of an internal combustion engine.

Cited by 11 publications

References 0 publications

Passive control of an impulsive wave using a cavity/helical vane system

Passive control of an impulsive wave using a cavity/helical vane system

Weak shock reflection from an open end of a tube with a baffle plate

Attenuation Effect of Expansion Configuration and Acoustic Material on Propagation of Blast Waves in a Duct

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