Local exhaust system is an effective but energy-consuming method for capturing oil mist particles in machining workshops. To reduce the flow resistance of an exhaust system for minimal fan energy ...consumption, the method of applying individually shape-optimized exhaust hoods, namely mass-production design, is feasible. However, the combined effect of multiple exhaust hoods in an exhaust system may not be optimal in reducing the flow resistance. This investigation thus firstly validated the shape optimization of an individual exhaust hood by a discrete adjoint method. The discrete adjoint method could adjust the shape of an exhaust hood automatically in the direction of reducing the flow resistance. The design variables were the coordinates of wall boundaries of the exhaust hood. The validation used measured data from a small-scale experiment. This study then applied the validated discrete adjoint method to conduct customized design through the shape optimization of multiple exhaust hoods simultaneously in the exhaust system. The flow resistance under customized design was compared with the method of mass-production design. The results revealed that the customized design led to different shapes of individual exhaust hoods and they were different from the shape of the individually optimized exhaust hood. The flow resistance of the exhaust system under customized design was reduced by 57%. However, only 36.5% reduction in flow resistance was achieved when the mass-production design method was employed. The customized design method was more effective in reducing flow resistance of the exhaust system.
•The discrete adjoint method for shape optimization of an exhaust hood was validated.•The flow resistance under the mass-production and customized design were compared.•The performance of uniform and non-uniform exhaust systems was compared.•The mass-production and customized design reduced the flow resistance by 36.5% and 57%.•Uniform exhaust system is recommended but it costs 60.7% more material than the non-uniform one.
In this new era, noise pollution is very high. One of the reasons for this noise pollution is sound which is generated by the exhaust system of the motorbike. So, it is necessary to reduce the noise ...coming from the exhaust of the motorbike. In this paper, original silencer reverse engineering has been done, then three modification models of the silencer with its analysis have been done and from those results, one of the modified silencers was selected and it was sent for manufacturing. After fabrication of the silencer, two tests were conducted. First, the test was conducted with original silencer, then it was conducted with modified silencer. From that data, transmission loss of original and modified silencers was calculated and then compared with each other and from that, noise was reduced to 5db. Also, flow velocity of exhaust gas in original silencer and modified silencer were also measured. It concluded that modified flow was increased by 11% to original silencer and also PUC of modified silencer was checked and it was in limit as per the PUC norms.
Globally, over 60% of generated electricity is derived from fossil fuels. In the Gulf Cooperation Council (GCC) region, most of electrical power is generated from fossil fuel fired thermal power ...stations, which are operated either in simple cycle (SC) or combined cycle (CC). The combined cycle is applied in industry to maximize the waste heat recovery. However, 70% of the thermal power plants are in SC configuration in GCC countries, while only 30% are in CC. In the United States, the SC to CC ratio is 54–46%. Considering the large number of SC power plants, exhaust heat recovery upgrades options are of particular interest. This paper aims to investigate and evaluate the potential of incorporating cost-effective new developed heat recovery methods.
In this work, the utilization of extracted heat is categorized into three implementation zones: within the gas turbine flange-to-flange section, auxiliary systems and outside the gas turbine system in the power plant. Moreover, a new methodology has been established to enable qualitative and comparative analyses of the system performance of nine recently developed heat extraction methods according to well identified criteria including safety and risk, complexity of implementation, effectiveness, scale of modifications and the potential market opportunity. The developed methodology is used to advise further system modifications and improvements on the studied inventions for the purpose of enhancing the plant efficiency.
Based on the conducted analysis, no single design out of the investigated in this paper was able to full achieve the established criteria, a summarized comparison and scoring table was constructed to provide direct comparison between the recent heat recovery patents, among each other, as well as typical waste heat recovery units that are commonly used in the gas turbine industry. It was concluded that each of the presented designs has particular benefits and can be selected for implementation according to the objective, the length of downtime and monetary capital available to the owner of the power station.
Based on the results obtained from the comparative scoring tables, a new design of integrated heat recovery system was proposed. The new system incorporated a circular duct heat exchanger to extract the heat from the exhaust stack and deliver the intermediary heat transfer fluid to a separate fuel gas exchanger. This system showed superiority in improving the thermodynamic cycle efficiency, while mitigating safety risks and avoiding undesired exhaust system pressure drop.
Purpose
Novel aircraft propulsion configurations require a greater integration of the propulsive system with the airframe. As a consequence of the closer integration of the propulsive system, higher ...levels of flow distortion at the fan face are expected. This distortion will propagate through the fan and penalize the system performance. This will also modify the exhaust design requirements. This paper aims to propose a methodology for the aerodynamic optimization of the exhaust for novel embedded propulsive systems. To model the distortion transfer, a low order throughflow fan model is included.
Design/methodology/approach
As the case study a 2D axisymmetric aft-mounted annular boundary layer ingestion (BLI) propulsor is used. An automated computational fluid dynamics approach is applied with a parametric definition of the design space. A throughflow body force model for the fan is implemented and validated for 2D axisymmetric and 3D flows. A multi-objective optimization based on evolutionary algorithms is used for the exhaust design.
Findings
By the application of the optimization methodology, a maximum benefit of approximately 0.32% of the total aircraft required thrust was observed by the application of compact exhaust designs. Furthermore, for the embedded system, it is observed that the design of the compact exhaust and the nacelle afterbody have a considerable impact on the aerodynamic performance.
Originality/value
This paper presents a novel approach for the exhaust design of embedded propulsive systems in novel aircraft configurations. To the best of the authors’ knowledge, this is the first detailed optimization of the exhaust system on an annular aft-mounted BLI propulsor.
Display omitted
•A fundamental calculation methodology using mode equivalent factors was proposed.•A lumped-parameter model with the six-element and two mass points was set up.•Vibration parameters ...were analysed from the model and the mode equivalent factors.•The transmissibilities are in good agreement with the actual measurements.•The approach can be used as a prediction method in engineering applications.
Dynamic behavior is a key factor for preventing fatigue failures of a structure or system. With fundamental specimens of simple cantilevered structures, the basic calculation methodology using equivalent factors of vibration mode was proposed and verified. With a rigid installation under bolt fastening, the vibration transmissibility of a coupled catalyst muffler system connecting in parallel was examined through a shaker system. The resonance peaks of the first, second translational modes, and the rotation mode of two units were identified in three excitations. A lumped-parameter model was built using the six-element and two mass points for modeling the muffler system. The dynamic parameters were analyzed, and their coupled vibration transmissibilities were calculated with the equivalent factors of mode. The calculated curves were in excellent agreement with the experimental curves, and the characteristic parameters were identified. When the spring and damping coefficients of the connecting pipe in the specimen were changed, the resonance frequencies and transmissibilities changed accordingly by calculation. This approach is appropriate to be used as a prediction method for vibration control and optimization including interactions and damping in a system with complicated components in engineering applications.
•Up to 90% drag reduction rate can be achieved by spraying.•Drag reduction downstream of the spray produces a significant drag reduction.•Saturated spray flow and inclination of 45° or 60° have the ...best drag reduction.
The drag of the exhaust pipe greatly influences the engine power performance of an engineering vehicle. The engine power performance would decrease significantly when the exhaust drag is large. The drag reduction effect achieved by the existing drag reduction is relatively weak; thus, based on spray cooling, drag reduction technology is introduced to solve this problem. The present study aims to determine the influence of spray parameters on drag reduction using an electric heating test bench and to clarify why spray significantly reduces drag using numerical simulations based on Discrete Phase Modeling (DPM). The obtained results prove that increasing the flow value in the test spray flow range of 12–24 ml/s can significantly improve the drag reduction performance. When the spray inclination increases from 45° to 90°, the drag reduction remains, in the beginning, unchanged and then decreases. Under the synergistic effect of the frictional resistance reduction and the dynamic pressure reduction, the resistance downstream of the spray location is significantly reduced. Compared with the existing drag reduction, the spray drag reduction has obtained the ultimate drag reduction effect, and the drag reduction rate is as high as 90 %. To conclude, this research will help promote the application of spray drag reduction to engineering vehicles.
The flow of exhaust gases is the source of many physical processes, including thermal, acoustic, mechanical and chemical phenomena with high dynamics of changes. The study analyzes the impact of the ...entire structure of the exhaust system on the formation of acoustic energy, determining the transmission loss characteristics of its individual components and the entire system. On the example of a structure based on a proprietary solution of an adjustable reactive muffler, the possibilities of shaping the flow of acoustic waves in the process of designing and selecting exhaust systems for internal combustion engines were determined. The study was carried out with the use of the CFD method and a specialized package for advanced simulations AVL AST.
The safety issue involving unplanned H2 leakage has retarded promotion of Hydrogen fuel cell vehicles (HFCVs). When an accidental leakage occurs in a relatively closed space, H2 tends to accumulate. ...It is necessary to obtain a better understanding of the H2 dispersion characteristics in a relatively closed space. Most studies focus on the dispersion features in a small garage, whereas few consider large underground garages with complex ventilation systems. Herein, H2 released from a pressurized tank in a real large underground garage was investigated by a two-stage computational fluid dynamics (CFD) study. An isentropic expansion model with a real gas equation of state was employed in stage (1) to estimate the source strength which can be used as inlet boundary conditions for stage (2), the dispersion stage. The CFD models were validated against the experimental results. The concentration field and flammability envelope were focused. This study provides a feasible method for assessing the risks associated with HFCVs.
•HFCVs are viable net zero carbon emission strategies in transportation.•Unplanned H2 leakage in HFCVs is risky for humans and retards their development.•H2 dispersion released from a pressurized tank in a garage is investigated using CFD.•CFD simulation results agree with source strength and dispersion profile predictions.•This study provides a feasible method for assessing the risks associated with HFCVs.
In die casting, gas defects occur if the molten metal entrains the gas inside the shot sleeve and mold and remains inside the product after filling. Therefore, an exhaust system such as an exhaust ...runner or overflow is generally designed at the die casting mold to discharge the gas-entrained molten metal outside the mold completely. In addition, an overflow has a broader designable area than an exhaust runner has and can discharge the gas-entrained molten metal, which an exhaust runner cannot. Therefore, designing the overflows at appropriate positions and volumes in die casting is essential. In recent years, research regarding the design of the overflow positions has been conducted by combining optimization theory and computational fluid dynamics (CFD). However, optimizing the overflow positions only can cause gas defects in the product and the unnecessary discharge of molten metal due to the overflow volume excess. Moreover, applying those methods is difficult because the analysis to verify the exhaust system includes the entire mold as the analysis domain, which increases calculation time. In this research, we propose the automatic overflow design system to discharge the gas-entrained molten metal inside the product completely by estimating the direction of molten metal flow and evaluating the efficiency of overflow design positions. Finally, we verified the effectiveness of the proposed system by actual die casting experiments using the proposed overflow shape.
•In die casting, overflow system performance significantly affects product quality.•Conventional trial-and-error design fails to consider the flow inside the mold.•Estimates the direction of molten metal flow using Computational Fluid Dynamics.•The system made it possible to design the overflow system with a few analyses.•All gas-entrained molten metal is discharged, and quality is expected to improve.
Air pollution by wood dust in furniture production sites is an important hygiene issue. The dust is created by all types of wood and wood-based material machining, and its concentration in the ...working zone surrounding the machining stand depends on the effectiveness of the dust exhaust system. In present research, three setups of the dust extraction system for a conventional table sawing machine are considered while machining particleboards. The results showed a high impact of the exhaust system connection setup on the dust concentration in the air surrounding the sawing machine work stand. The use of both main and auxiliary sawdust extraction connectors together ensured the highest clearness of the air, with only 0.5 mg/m
of dust concentration. Closing the upper hood leads to a concentration five times higher, while disconnecting it results in a ten times higher dust content. The finest dust particles (<1 µm), however, are the most numerous in the case of closing the hood.
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