Exhaust Duct Research Articles

Influence of the marine 4-stroke diesel engine malfunctions of the air and exhaust duct on the composition of exhaust gas

Influence of the marine 4-stroke diesel engine malfunctions of the air and exhaust duct on the composition of exhaust gas

Carbon and Hydrogen Accumulation on Exhaust Duct in LHD

Carbon and Hydrogen Accumulation on Exhaust Duct in LHD

Numerical Study of the Impact of Filters Located in the Exhaust Duct of a Low-Voltage Circuit Breaker

Low-voltage circuit breakers under critical situations such as a severe short circuit develop a strong electric arc leading to brutal manifestations such as envelope rupture or fire. Apparatus are strictly designed to avoid damages like personal injury and material destruction. To limit the external manifestations of the electric arc, an efficient way consists of inserting a porous filter in the gas exhaust duct, composed of metallic cloth arranged in a Reps structure. Experimental tests have demonstrated the efficiency of this technique. We propose to complete the experimental study by carrying out the numerical simulations about the filter impact on the hot gas flow. A 2-D model based on the gas flow in porous media is considered, taking into account the porosity variation while the electric arc model derives from the experimental data and a thermal radiation model. A sophisticated finite-volume method based on a well-balanced scheme developed for nonconservative system is used to correctly approximate the solution when dealing with porosity variation.

Experimental Research of HCCI Combustion Based on Late Exhaust Duct EGR Strategy

Late exhaust duct EGR strategy is one of internal EGR strategies to realize HCCI combustion. Based on a single-cylinder test engine system equipped with an electronic controlled hydraulic variable valve train system, the effects of valve phases in this strategy were studied. The results show that at engine speed 1000r/min, equivalent air-fuel ratio λ= 1, when the IVO phase is put off, EGR ratio increases gradually, CA10 and CA50 are postponed and combustion duration becomes longer. At the same time, peak pressure and maximum pressure rise rate have a tendency to descend. When the SEVO phase is postponed, the parameters of the test engine will also be affected. However, when the phase is postponed above the critical point, the parameters have a backward trend. The property of HCCI combustion is not sensitive to SEVO phase.

ЧИСЛЕННОЕ МОДЕЛИРОВАНИЕ ГИДРАВЛИЧЕСКИХ ХАРАКТЕРИСТИК КОЛЕНООБРАЗНЫХ ГАЗООТВОДОВ ГТД

ЧИСЛЕННОЕ МОДЕЛИРОВАНИЕ ГИДРАВЛИЧЕСКИХ ХАРАКТЕРИСТИК КОЛЕНООБРАЗНЫХ ГАЗООТВОДОВ ГТД

Optimum Design of Manganese-coated Copper Catalytic Converter to Reduce Carbon Monoxide Emissions on Gasoline Motor

One of the engineering technologies that can be used to reduce air pollution is the use of catalytic converter mounted on vehicle gas exhaust duct. Unfortunately, these tools are very expensive in the market and not all motor vehicles use these technologis, because the catalyst was made from exoensive metals and rarely available in the market, such as: Palladium, Platinum and Rhodium. Besides, the catalyst is susceptible to premium fuel with low levels of lead (Pb) which results in the damage of the function of the catalyst due to blockage in the honeycomb Catalytic Converter. Therefore research needs to be done in the laboratory to test the other substrate materials as a catalyst, to study the ability of the catalyst in a catalytic converter to reduce exhaust emissions of Carbon Monoxide. This research will also study the performance capabilities and assess the effectiveness of Manganese-coated Copper catalysts which are designed in such a way to obtain the appropriate shape and type of Catalytic Converter catalyst and suitable for premium fuel motor vehicles. The result showed that (1) Catalytic Converter design and modification of catalytic materials can be an alternative to overcome the high air pollution problem from the transportation sector, esspecially particular Carbon Monoxide exhaust emissions from gasoline motors. (2) The use of Manganese-Coated Copper as a catalyst in the catalytic converter was significantly able to increase the reduction of Carbon Monoxide exhaust emissions. (3) The increase of catalyst cells amount decreased the concentration of Carbon Monoxide exhaust emissions. (4) Optimum Design of Model 2 Catalytic Converter was able to reduce exhaust emissions of Carbon Monoxide.

A Computational and Analytical Study into the Use of Counter-Flow Fluidic Thrust Vectoring Nozzle for Small Gas Turbine Engines

This paper provides an understanding of counter-flow fluidic thrust vectoring, in the presence of the secondary air vacuum, applied to the exhaust nozzle of a micro-jet engine. An analytical and numerical study is performed here on a divergent collar surface adjacent to the cylindrical exhaust duct system. The vectoring angle is controlled by manipulating the momentum flux through a vacuum gap that is located on a circle concentric to the main nozzle. Three dimensional numerical simulations are conducted by utilizing a computational fluid dynamics model with two-equation standard k-ε turbulence model to study the pressure and velocity distribution of internal flow and nozzle geometry. Moreover, an analytical validation is carried out based on the known mathematical form of the governing equations of fluid dynamics over the sinusoidal wall. It is shown that the analytical results are in good agreement with numerical simulations, which also show that the pressure coefficient over the collar surface has the same trend as given by computational simulation. Similarly, the results of the numerical method are also verified against experimental results that were approved by previous research in area of numerical model for co-flow fluidic thrust vectoring technique.

Acoustic signature characterization of a sub-scale rocket launch

Georgia Tech Research Institute (GTRI) conducted a flight test of a sub-scale rocket in 2013 outside Talladega, Alabama, to acquire the launch acoustics produced. The primary objective of the test was to characterize the acquired data during a sub-scale launch and compare it with heritage launch data from the STS-1 Space Shuttle flight. Neither launch included acoustic suppression; however, there were differences in the ground geometry. STS-1 launched from the Mobile Launch Platform at Pad 39B with the RS-25 liquid engines and Solid Rocket Boosters (SRBs) firing into their respective exhaust ducts and flame trench, while the GTRI flight test vehicle launched from a flat reflective surface. The GTRI launch vehicle used a properly scaled Solid Rocket Motor (SRM) for propellant; therefore, primary analysis will focus on SRM/SRB centric acoustic events. Differences in the Ignition Overpressure (IOP) wave signature between both due to this will be addressed. Additionally, the classic liftoff acoustics “football shape” is preserved between both full and sub-scale flights. The launch signatures will be compared, with note taken of specific launch acoustic events more easily investigated with sub-scale launch data or supplement current sub-scale static hotfire testing.

On Sound Radiation from an Open-Ended Non-Uniformly Lined Cylindrical Nozzle

Acoustic liners are widely used in jet engine inlet and exhaust ducts, as a passive means of noise reduction. One possible way of liner optimization is the use of a non-uniform acoustic impedance distribution. It has been shown that such a liner can lead to an attenuation in the acoustic amplitude of some of the modes present in the duct. However, the sound attenuation perceived by an observer in the far-field is arguably the most important effect to be achieved. These issues may be illustrated by considering the radiation of sound from a cylindrical duct with impedance varying circumferentially, axially or in both directions and the acoustic pressure at the far-field in each situation. The radiation of sound from an open pipe is represented by a pressure distribution on a disk, viz. the exit plane. The radiation of sound in free space, i.e. without obstacles, is specified by a Kirchhof integral. The source distribution on the duct exit plane, which allows the evaluation of radiation integrals, is specified by the radial, axial, and circumferential modes, in the cylindrical nozzle. The evaluation of the radiation integrals show that (i) the total acoustic field consists of a spherical wave multiplying a sum of radial modes n = 1, . . . ,∞ and azimuthal modes of odd order only m = 1,3,5, . . . ; (ii) each mode consists of a monopole term and a dipole term and depend on the frequency and the radial wavenumbers, determined by the boundary condition at the duct wall. When the impedance distribution varies circumferentially or axially, the evaluation of the wavenumbers involves the determination of the roots of an infinite determinant, while when the impedance aries both axially and circumferentially, the roots of a doubly infinite determinant have to be calculated. In the case of external noise of an aircraft, the observer is on the ground, at a distance much greater than the duct diameter, and the radiation integrals for an observer in the far-field can be simplified, since the dipole term is weak. The evaluation of the acoustic pressure for an observer in the far-field, shows that it depends on the radial wavenumbers in the nozzle, which are specified by the wall boundary conditions, and thus depend on the acoustic impedance distribution. This allows comparison of hard-walled nozzles, with liners with constant impedance and non-uniform liners, the latter with impedance distribution varying circumferentially, axially or in both directions. The far-field acoustic pressure is specified by a directivity factor that is calculated for several values of the parameters for each of the cases mentioned above.

대형 주물공정 용접작업장의 건강 위해인자 및 환기 개선

이 연구에서는 대형 주물공정 용접작업장 근로자들의 건강보호 및 작업환경 개선을 위해 위해인자 조사 및 분석작업을 수행하였다. 또한, 대상 작업장의 작업환경을 개선하기 위해 측정 및 전산유체해석 모델링을 수행한 후 효과적인 환기방법을 제안하였다. 대형 주물공정 용접작업장 근로자들의 건강 위해인자를 조사한 결과, A사는 산화철분진, B사와 C사는 용접흄, D사는 용접 흄과 산화철분진이 주오염원인 것으로 확인되었다. 작업자 호흡영역에서의 흄 농도는 <TEX>$0.05{\sim}4.37mg/m^3$</TEX>이었고, 용접작업장 공기 중 흄 농도는 <TEX>$0.13{\sim}7.54mg/m^3$</TEX>이었다. 또한, 용접작업 시 최적의 환기방법을 제안하기 위해 측정 및 전산유체해석 모사를 수행한 결과, 배기공정의 경우에는 배기 덕트를 용접점에 근접시켜 국소배기를 실시하는 것이 효과적인 것으로 나타났다. 급기공정의 경우에는 개구부 끝 부분에서 급기를 하며 급기용 팬은 작업 공간 외부에 설치하는 것이 효과적일 것으로 나타났다. 향후 대형 주물공정 용접작업장의 터널형 반밀폐 공간에 대한 환기방법을 표준화한다면 주물산업 및 조선업 등에 종사하는 용접 근로자들의 건강보호 및 작업환경 개선에 매우 효과적일 것으로 판단된다. In this study we have examined the health risk factors and analyzing data of laborers working at the welding operation at large-sized casting process. In order to improve the working environment of workplace, an effective ventilation method was proposed after performing CFD (computational fluid dynamics) modeling and measurement of pollutants. As a result of examining the health risk factors of workers, oxidized steel dust is the main pollution source in the company A, welding fume in the companies B and C, and welding fume and oxidized steel dust in the company D. The fume concentration in the workers' breathing zone was <TEX>$0.05{\sim}4.37mg/m^3$</TEX>, and the fume concentration in the indoor air at the welding process was <TEX>$0.13{\sim}7.54mg/m^3$</TEX>. From a result of CFD, a local exhaust with an exhaust duct adjacent to welding point was found to be most effective in case of the exhaust process. In case of air supply, we found that a desired location of air supply fan would be at the end of the opening. If a standardizing the ventilation system for tunnel-type semi-enclosed space at a large-sized casting process is introduced in welding work places in the future, it would be more effective to protect the health of welding workers working at the casting industry and shipbuilding industry and improve the work environment.

Effect of pin fin to channel height ratio and pin fin geometry on heat transfer performance for flow in rectangular channels

The efficiency of a thermoelectric generator (TEG) can be defined as the ratio of the power output to the heat input at the hot side of the device. This ratio is governed by the laws of thermodynamics and thus cannot exceed the Carnot efficiency. It follows that the greater the difference between the temperatures of the hot and cold sides of the device, the greater the efficiency and power output from the TEG. This study focuses on effective techniques to enhance heat transfer on the hot side of the TEG in order to increase the total power output from the device. In this study heat transfer enhancement mechanisms are evaluated for the hot side of a TEG system generating power from waste heat in automobile exhaust gases. The use of pin fins was examined, as they are a common and effective way to increase heat transfer in a channel. Heat transfer enhancement measurements are presented with 3-dimensional partial pin fin arrays of circular, triangular, hexagonal, and diamond shapes on the walls of a rectangular channel representing the hot side of the TEG system and the automobile exhaust duct. Channel heights are varied to measure the effect of the pin fin height to channel height ratio while keeping the pin fin height constant. Channel hydraulic diameter and configuration of the fins were chosen based on existing literature. Pin fin performance is studied over a range of Reynolds numbers, calculated based on full channel height. The pin fins with the best initial performance have been further analyzed by varying the channel height in order to change the pin fin to channel height ratio while keeping the hydraulic diameter to pin fin height ratio constant. The experiments use the transient liquid crystal method to measure detailed heat transfer coefficients on the test surface. Results show that the diamond pin fins perform the best in enhancing heat transfer. Lower channel heights that cause pin fins to block 50% of the channel provide significantly higher heat transfer coefficients.

An uncertainty analysis of mean flow velocity measurements used to quantify emissions from stationary sources

Point velocity measurements conducted by traversing a Pitot tube across the cross section of a flow conduit continue to be the standard practice for evaluating the accuracy of continuous flow-monitoring devices. Such velocity traverses were conducted in the exhaust duct of a reduced-scale analog of a stationary source, and mean flow velocity was computed using several common integration techniques. Sources of random and systematic measurement uncertainty were identified and applied in the uncertainty analysis. When applicable, the minimum requirements of the standard test methods were used to estimate measurement uncertainty due to random sources. Estimates of the systematic measurement uncertainty due to discretized measurements of the asymmetric flow field were determined by simulating point velocity traverse measurements in a flow distribution generated using computational fluid dynamics. For the evaluated flow system, estimates of relative expanded uncertainty for the mean flow velocity ranged from ±1.4% to ±9.3% and depended on the number of measurement locations and the method of integration.Implications:Accurate flow measurements in smokestacks are critical for quantifying the levels of greenhouse gas emissions from fossil-fuel-burning power plants, the largest emitters of carbon dioxide. A systematic uncertainty analysis is necessary to evaluate the accuracy of these measurements. This study demonstrates such an analysis and its application to identify specific measurement components and procedures needing focused attention to improve the accuracy of mean flow velocity measurements in smokestacks.

Fan Noise Sources and Passive Reduction Methodologies in High Bypass Turbofan Engines

Increasing air traffic and more stringent aircraft noise regulations continue to increase requirements on community noise prediction capabilities for conventional and unconventional aircraft configurations. For engines with a high bypass ratio, fan noise is a major noise source. The main established technologies for fan reduction and those currently under evaluation are scarf inlets, forward swept fans, swept and leaned stators, fan trailing edge blowing, acoustic treatment placed over the fan and acoustic liners. Acoustic liners have desirable acoustic attenuation properties and thus are commonly used to reduce noise in jet engines. The liners typically are placed upstream and downstream of the rotors (fans) to absorb sound before it propagates out of the inlet and exhaust ducts. This paper focusses on about the main fan noise sources in new modern turbofan engines.

Monitoring of heavy metal particle emission in the exhaust duct of a foundry using LIBS

Heavy metals have long been known to be detrimental to human health and the environment. Their emission is mainly considered to occur via the atmospheric route. Most of airborne heavy metals are of anthropogenic origin and produced through combustion processes at industrial sites such as incinerators and foundries. Current regulations impose threshold limits on heavy metal emissions. The reference method currently implemented for quantitative measurements at exhaust stacks consists of on-site sampling of heavy metals on filters for the particulate phase (the most prominent and only fraction considered in this study) prior to subsequent laboratory analysis. Results are therefore known only a few days after sampling. Stiffer regulations require the development of adapted tools allowing automatic, on-site or even in-situ measurements with temporal resolutions. The Laser-Induced Breakdown Spectroscopy (LIBS) technique was deemed as a potential candidate to meet these requirements.On site experiments were run by melting copper bars and monitoring emission of this element in an exhaust duct at a pilot-scale furnace in a French research center dedicated to metal casting. Two approaches designated as indirect and direct analysis were broached in these experiments. The former corresponds to filter enrichment prior to subsequent LIBS interrogation whereas the latter entails laser focusing right through the aerosol for detection. On-site calibration curves were built and compared with those obtained at laboratory scale in order to investigate possible matrix and analyte effects. Eventually, the obtained results in terms of detection limits and quantitative temporal monitoring of copper emission clearly emphasize the potentialities of the direct LIBS measurements.

Numerical modeling of flow mixing and cooling processes in a perforated exhaust duct

Numerical studies of gas-hydrodynamic processes in a perforated exhaust duct are carried out. The distributions of velocity and temperature fields are obtained for different design of exhaust duct. The thermal effect of hot gas on the exhaust duct walls is analyzed.

Using Acoustic Liner for Fan Noise Reduction in Modern Turbofan Engines

With the increase in global air travel, aircraft noise has become a major public issue. In modern aircraft engines, only a small proportion of the air that passes through the whole engine actually goes through the core of the engine, the rest passes around it down the bypass duct. A successful method of reducing noise further, even in ultra-high bypass ratio engines, is to absorb the sound created within the engine. Acoustically absorbent material or acoustic liners have desirable acoustic attenuation properties and thus are commonly used to reduce noise in jet engines. The liners typically are placed upstream and downstream of the rotors (fans) to absorb sound before it propagates out of the inlet and exhaust ducts. Noise attenuation can be dramatically improved by increasing the area over which a noise reducing material is applied and by placing the material closer to the noise source. In this paper we will briefly discuss acoustic liner applications in modern turbofan engines.

Wykorzystanie indeksu termiczno� wilgotnosciowego (THI) do oceny warunk�w termiczno-wilgotnosciowych w oborach wolnostanowiskowych

The objective of this study was to evaluate temperature/humidity conditions in freestall barns with different types of gravity ventilation and to determine the risk of heat stress in cows based on the temperature-humidity index. The study was carried out during summer months (June/July) in two free-stall barns located in north-eastern Poland. The buildings for the study were selected based on the natural ventilation and animal housing systems used. One building was equipped with supply ducts mounted over windows and a roof ridge gap, and the other had flat roof exhaust ducts and side curtain. It was found from this study that the barn having flat roof exhaust ducts and air supply from side curtain was characterized by more favourable temperature/humidity conditions and presented a lower risk of heat stress to cows compared to the barn with roof ridge and air inlets. It was also found that cows in the barn with side curtain had comfortable conditions and those in the roof ridge barn were exposed to mild and moderate stress.

Optimal Machine Tools Selection Using Interval-Valued Data FCM Clustering Algorithm

Machine tool selection directly affects production rates, accuracy, and flexibility. In order to quickly and accurately select the appropriate machine tools in machining process planning, this paper proposes an optimal machine tools selection method based on interval-valued data fuzzy C-means (FCM) clustering algorithm. We define the machining capability meta (MAE) as the smallest unit to describe machining capacity of machine tools and establish MAE library based on the MAE information model. According to the manufacturing process requirements, the MAEs can be queried from MAE library. Subsequently, interval-valued data FCM algorithm is used to select the appropriate machine tools for manufacturing process. Through computing matching degree between manufacturing process machining constraints and MAEs, we get the most appropriate MAEs and the corresponding machine tools. Finally, a case study of an exhaust duct part of the aeroengine is presented to demonstrate the applicability of the proposed method.

Study on the Reasonable Smoke Exhaust Rate of the Crossrange Exhaust Duct in Double-layer Shield Tunnel

The research on the concentrated smoke extraction system of crossrange exhaust duct in double-layer shield tunnel is still very lack in the world. This paper is on the smoke extraction system of double-layer shield tunnel. It will provide the supports and references for the smoke control of tunnel fire and the determination of related technical parameters in the design of tunnel fire ventilation and smoke extraction, so it has important scientific value, practical significance and application prospects. This paper bases on the tunnel project of Slender West Lake in Yangzhou. By using the method of combining theory and numerical simulation, a conclusion can be drawn that the reasonable smoke exhaust rate of the upper tunnel is 140 m3/s.

1111 噴流拡散装置の低騒音化に対する基礎的研究

A muffler is attached to the exhaust duct of a diesel engine, and aerodynamic noise is generated by exhaust gas flows into the muffler. The jet flow diffusion device diffuses an air flow inside muffler. An air flow flowing into the jet flow diffusion device flow out outside through the perforated metal and slits. In this study, we performed measurements of the aerodynamic noise changing by perforated metal, the cone position and an attachment position of the support. Then, in order to clarify the aerodynamic noise sources, we performed measurements of the velocity fluctuation of the flow of air flowing out of the jet flow diffusion device. The result of the aerodynamic noise measurement experiment shows that the SPL increases when cone position is on the upstream side.