Typical Liner Research Articles

Outdoor engine test using acoustic liners combined with Fine-Perforated-Film

Resonant-type liner panels are one the primary countermeasures for the fan noise of aircraft engines, though the noise reduction performances of the liners are known to be tolerated by the flow streaming on the liner surface. Therefore, suppressing the effect of the flow on the liners is greatly important for larger noise reduction. In this study, a liner panel with a special surface structure was manufactured and applied to an outdoor test using a small turbofan engine, DGEN 380. The surface structure consisted of a special thin film, Fine-Perforated-Film (FPF), and a gap. The gap was fixed between the FPF and liner surface. In addition, a typical resonant-type liner and a hard wall were used for comparison, to investigate the effect of the structure. During the test, the samples were installed to the exhaust bypass duct of the DGEN 380 engine. The acoustic pressure was measured with a far field microphone array. Analysis and comparison of the results showed that the new structure suppressed the effect of the grazing flow and caused a larger amount of noise reduction, compared to the typical liner sample.

Fan Noise Reduction by Acoustic Liners Combined with Fine-Perforated-Film: Noise Tests by a Small Turbofan Engine DGEN 380

Resonant-type liner panels are one the primary countermeasures for the fan noise of aircraft engines, though the sound absorption performances of the liners are known to be tolerated by the grazing flow streaming on their surface. Therefore, suppressing the effect of the flow on the liners is greatly important for higher sound absorption efficiency. In this study, liner panels with special surface structures were manufactured and applied to an outdoor test using a small turbofan engine, DGEN 380. A special thin film, Fine-Perforated-Film (FPF), was applied to two liner samples. In the first sample, FPF was applied directly to the surface of a typical liner. In the second sample, a gap was fixed between the FPF and liner surface. In addition, a rigid wall and a typical liner were used for comparison, to investigate the effect of the structures. During the test, the samples were installed to the exhaust bypass duct of the DGEN engine. The acoustic pressure inside the duct and in far field was measured. Analysis and comparison of the results showed that the new structures suppressed the effect of the grazing flow and caused a larger amount of noise reduction, compared to the typical liner sample.

Response of a polymer liner passing across a pressure pipeline joint opening under axial ground movements

A closed form solution is developed to quantify the stresses that develop in polymer liners installed within pressure pipes, where the liner spans across a joint or ring fracture in the ‘host’ pipeline that is subjected to axial extension as a result of ground movements. The solution considers the zones of slip between liner and host pipe on either side of the joint that is opening. The expression derived indicates that maximum axial liner stress is proportional to the square root of the product of the gap that opens across the joint, liner modulus, internal fluid pressure, coefficient of friction between liner and host pipe, and inverse of liner thickness. Calculations are presented for a typical liner installed within a cast iron water pipe, though research is needed to quantify liner-host pipe friction. Comparisons to finite element calculations demonstrated that the new solution characterises the liner as having higher stiffness than numerical analysis using thick shell elements. Initially the two solutions match, but the new closed form solution becomes more conservative with increasing gap size. FEA was then used to show that temporary reductions in water pressure decrease axial liner stresses significantly.

Numerical Simulation on Jet Forming and Penetration Performance of Several Amorphous Energetic Alloy Liner with Typical Structures

The structure and material of the liner are the key factors that affect the forming and penetration ability of the jet. In order to study the influence of new energetic materials and typical liner shapes on jet forming and penetration behavior, this paper takes ZrCuNiAlAg amorphous alloy as the liner material and establishes four shaped charge (SC) models with conical, sub-hemispherical, eccentric sub-hemispherical and hypercumulative liners respectively. The jet forming law and its penetration process against the concrete target plates under different liner shapes are studied based on the AUTODYN numerical simulation software. The results show that a stable jet can be formed from ZrCuNiAlAg amorphous alloy liner under the Mohaupt effect, but the jets produced by liners with different structures differs quite a lot. Under the same conditions including charge diameter, charge length diameter ratio and wall thickness, the tip velocity, the tip-tail velocity difference and the length of the jet formed by conical and hypercumulative liners are significantly higher than those of sub-hemispherical and eccentric sub-hemispherical liners. The jet length of the hypercumulative liner is the longest while that of the eccentric sub-hemispherical liner is the shortest. The hypercumulative jet can penetrate a concrete target plate with 400mm thickness at 250μs, and the jets formed by conical, sub-hemispherical and eccentric sub-hemispherical liners basically stops the penetration ability at 300μs. In terms of penetration depth, the hypercumulative liner is the largest and the sub-hemispherical liner is the smallest. The sub-hemispherical liner gets the largest perforation aperture. The eccentric sub-hemispherical liner gets the best comprehensive effect of penetration and expansion against the concrete target. The results of this paper can be used for reference in the structural design of the amorphous alloy liner.

Quantification of annular flow in lined pipelines

This paper attempts to quantify the amount of flow within the annular space that could exist between a polymeric liner and a deteriorated host pipe. Inadequate fit of the liner within sewer line segments is likely to cause annular flow that will result in a higher flow rate within the wastewater collection system. The results of full-scale field tests performed by the authors on 12 pipelines lined with four different deformed/reformed or fold-and-form (DR/FF) and cured-in-place-pipe (CIPP) liner products indicated that gaps of different sizes existed in all of the tested pipelines. These gaps have resulted in variable annular flow in the tested pipelines. Based on the results of the full-scale tests, a mathematical relationship was established between the annular flow in a lined pipeline and the annular space. The relationship between the annular flow rate and the average annular gap size depends on the difference in head between the entry and exit points along the pipeline. In turn, the average annular gap size depends on many factors including tolerances and imperfections in the host pipe and liner, conditions of the host pipe and the quality of liner installation. A third-order polynomial equation was found to best describe the relationship between the annular flow and average gap size under high differential heads (up to 3.0 m or 10 ft); whereas, a logarithmic relationship fits best under low differential heads for wider range of annular gap sizes (up to 17.8 mm or 0.70 in.). Based on the results of the full-scale tests, this is believed to be more representative of typical liner installations.

NGC 1052: a LINER with strong stellar Mg/Fe gradient

We analyze long slit spectroscopy of NGC 1052, the third brightest member of a group of eleven galaxies. This elliptical is a typical LINER with a stellar rotating disk. We have found a strong negative radial gradient of the abundance ratio Mg/Fe, which suggests an enhancement of α-elements particulary towards the nuclear region, and higher metallicity and age at the galactic nucleus too. We have measured the Lick line-strength indices along the major axis of the galaxy. This information, together with single-aged stellar population models of Thomas et al. (2003), was used to determine the star formation history of NGC 1052.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Oil well perforator design using 2D Eulerian code

The purpose of the present study is to obtain a good shaped charge design using a 2D Eulerian code such that the high speed jet of the liner creates a large hole in the well casing and a small hole in the gun pipe. Double-velocity inverse gradients, one at the tip of the liner and another one located near the middle section of the jet, are described for conical and elliptical shaped charges. A series of computer simulations are performed for jet formation and penetration into the casing wall as well as the surrounding rocks. For a typical liner material, the penetrated casing hole size is related to the liner geometry, the amount of the explosive charge, and the shape as well as the thickness of the charge case. From this study, it is shown that the geometry and the thickness of the liner are the most pertinent parameters for a good charge design.

Microfluid Dynamics and Acoustics of Resonant Liners

It is known that most of the acoustic dissipation associated with a resonant liner takes place around the openings of the resonators. However, because the openings are physically very small, there has not been any direct experimental observation of the flow and acoustic fields in this region. As a result, current understanding of liner dissipation mechanisms are either completely theoretical or are based on experiments using much larger physical models. Inasmuch as large openings were used in these experiments, the true Reynolds numbers were unfortunately not reproduced. The flow around and inside a typical liner resonator under the excitation of an incident acoustic field is investigated by direct numerical simulation (DNS). There are two distinct advantages in using DNS. First, by the use of a carefully designed grid, even very small-scale features of the flowfield can be resolved and observed. Second, the correct Reynolds number can be imposed in the simulations. Numerical experiments reveal that at low sound intensity, acoustic dissipation comes mainly from viscous losses in the jetlike unsteady laminar boundary layers adjacent to the walls of the resonator opening. At high sound intensity, dissipation is due to the shedding of microvortices at the mouth of the resonator. The energy dissipation rate associated with the shedding of microvortices is found to be very high. Results of a parametric study of this phenomenon are reported.

Performance of acoustic liners for jet engine intake ducts

In order to meet current and future noise emission regulations, it is necessary to reduce the noise generated by aircraft engines. One method is to line the duct with an attenuating configuration, and acoustic liners employing the Helmholtz resonator concept are now commonplace in jet engine intake ducts. Based on reports of core failure, the question of the mechanisms behind such failures, being the interaction of high sound pressure levels and shock waves with the liners, is addressed. Full-scale experimental pressure data are presented. Moreover, using the experimental data as input to a numerical model for nonrigid cavity walls, the induced stresses are analyzed. Results for typical liner configurations are given, and the nonlinear orifice effects considered. Possible alternative designs are examined and their advantages and disadvantages from an acoustic viewpoint discussed.

S III] 9069, 9532 EMISSION IN ACTIVE GALACTIC NUCLEI

ABSTRACT Observations of the [S III] λλ9069,9532 emission lines in the nuclear spectra of two Seyfert 2 galaxies, four LINERs, and two galaxies, with H II region nuclei are presented. These data are combined with published measurements to reexamine the suggestion by Diaz and collaborators that the relative strengths of the [S II] λλ6716,6731 and [S III] λ λ9069,9532 lines in LINER nuclei provide a powerful method of distinguishing between photoionization and shock heating mechanisms. On the basis of this larger sample of objects, we find general support for the idea that many LINERs are photoionized and form a continuous sequence with Seyfert nuclei characterized by decreasing ionization parameter. Nevertheless, comparison with shock model calculations and published observations of the Kepler SNR shows that the [S II] and [S III] lines alone cannot be used to unambiguously rule out shock models as an alternate explanation for the emission-line spectra of typical LINERs. Indeed, in the case of the LINER nucleus of the luminous infrared galaxy NGC 6240, the observed strengths of these lines would appear to strongly favor shock heating as the dominant source of ionization. Thus, we conclude that both photoionization and shock heating are likely to play significant roles in any given LINER, with either process capable of dominating the observed emission-line spectrum.

Erratum: Fifth Canadian Geotechnical Colloquium: Control of contaminant migration by the use of liners

Procedures satisfactory for the design of seepage control liners for hydraulic structures are not generally sufficient for the design of pollution control liners, where the primary intent is mitigation of contaminant migration effects on the environment. Contaminant migration rates and concentrations are controlled by seepage rate, dispersion and diffusion processes, and attenuation mechanisms such as filtration, precipitation, adsorption, and biodegradation. Both liner and subsoil (or bedrock) properties affect contaminant migration; thus, both should be considered as part of the overall liner system. Mechanisms for controlling migration are limited by the perceived extent of the liner system. Typical liner materials include compacted clays, admixes, polymeric membranes, spray-ons, and sealants. The field hydraulic properties, liner thickness, and liner–fluid compatibility should be considered in design

Fifth Canadian Geotechnical Colloquium: Control of contaminant migration by the use of liners

Procedures satisfactory for the design of seepage control liners for hydraulic structures are not generally sufficient for the design of pollution control liners, where the primary intent is mitigation of contaminant migration effects on the environment. Contaminant migration rates and concentrations are controlled by seepage rate, dispersion and diffusion processes, and attenuation mechanisms such as filtration, precipitation, adsorption, and biodegradation. Both liner and subsoil (or bedrock) properties affect contaminant migration; thus, both should be considered as part of the overall liner system. Mechanisms for controlling migration are limited by the perceived extent of the liner system. Typical liner materials include compacted clays, admixes, polymeric membranes, spray-ons, and sealants. The field hydraulic properties, liner thickness, and liner–fluid compatibility should be considered in design