Optimum Area Ratio Research Articles

Investigation on friction and wear performance of volcano-shaped textured PVD coating

This study aims to investigate friction and wear performance of a novel volcano-shaped textured PVD coating , hoping to find the influence mechanism of volcano-shaped texture on the tribological behavior of textured coated surface. The volcano-shaped texture was fabricated on the sample surface by laser, and then PVD coating was deposited. For samples with different texture diameters or texture area ratios, reciprocating pin-on-disk wear tests were conducted to study tribological properties. After tests, wear topographies of samples and counter pins were observed to analyze wear details. The results showed volcano-shaped texture with suitable diameters and area ratios was conducive to lowering friction coefficient and reducing adhesive wear . The optimal texture diameter and area ratio were 310 μm and 25%, respectively. Meanwhile, the texture with large area ratios increased friction. These results indicated this texture's potential for friction control. Finally, the influence mechanism of volcano-shaped texture was proposed. • The volcano-shaped texture can both decrease and increase friction. • There exists optimal diameter and area ratio of volcano-shaped texture to achieve best friction and wear performance. • Tribo-film formed on the convex area reduced texture wear. • Influence mechanism of volcano-shaped textured PVD coating on the friction and wear performance was studied.

Performance investigation of an ejector expansion refrigeration system working on different alternative refrigerants to R134a

ABSTRACT In this paper, the performance characteristics of an ejector-expansion refrigeration cycle using six low GWP alternative refrigerants for R134a are presented through the first and second laws of thermodynamics. The ejector is modelled by assuming a constant-mixing pressure. The investigated refrigerants are compared based on the optimum ejector area ratio, discharge temperature, volumetric cooling capacity (VCC), coefficient of performance (COP) and exergy efficiency (ηex). The drop-in analysis is considered based on the same operating/designing parameters, and the VCC, COP and ηex improvements over the conventional refrigeration cycle are presented. The improvements in COP and VCC are between 7.914%–18.46% and 5.712%–22.82%, respectively, for the investigated range of evaporating and condensing temperatures. These values are higher than that of R134a by about 21% and 16%, respectively. The VCC using R1234yf is very close to R134a with a maximum reduction of 6.5%. Therefore, R1234yf refrigerant appears to be the best alternative to R134a in an ejector-expansion system with an appreciable COP and ηex devaluation. R152a outperforms R134a in terms of COP and ηex, thus it is a suitable alternative to R134a except for safety.

Performance Evaluation of LowThrust Rocket Nozzles of Various Geometries

Issues of viscous loss in rocket nozzle become increasingly more important as the thrust chamber is reduced in size. A properly designed nozzle is critical since small geometrical differences can result in dramatically modified performance. The present study analyzes the performance of conical converging-diverging nozzle for low-thrust rocket application. A total of five nozzles with different area ratio and divergence length were numerically tested; two optimum area ratio nozzles, one underexpanding nozzle and two overexpanding nozzles. The main aim is to analyze the flow phenomena of compressible gas flows within these nozzles and its relation to the rocket performance (i.e. thrust). The axisymmetric flow problems are numerically solved using a well-validated software with the Spalart-Allmaras turbulence model is employed to model the effect of turbulent on the flow. The results revealed technique of eliminating flow separation and obviously, knowledge of the point of separation is essential for performance enhancement. The elimination of flow separation inside the overexpanding nozzle by means of truncating it at a point of separation increases the thrust produced by 18% for a relatively low combustion pressure. It is anticipated that the thrust enhancement would be greater for a higher nozzle pressure ratio (NPR, i.e. the ratio of combustion chamber total pressure and atmospheric static pressure). With the demonstrated performance enhancement, this work serves as a driver for further nozzle enhancement using this technique.

Effect of Angle of Turn on Loss Characteristics and Flow Rectification of Curve Diffuser

Curve diffuser is often used in HVAC and wind tunnel systems to provide pressure recovery and avoid excessive energy loss to the surrounding environment. Performance of curve diffuser is disturbed mainly by the presences of flow separation and secondary flow vortices occurred due to the effect of turning angle, in which scarce literature found. In this study, the effect of turning angle from 30° to 180° configured with an area ratio of 1.60 to 4.00 and inflow Reynolds number of 5.934x104 – 1.783x105 on loss characteristics and flow rectification of curve diffuser is investigated with optimum configuration is proposed. Performance of curve diffuser is evaluated in terms of pressure recovery and flow uniformity using ANSYS CFD equipped with validated Standard k-ɛ model (ske) and enhanced wall treatment of y+ = 1.2 - 1.7. Results show that performance of pressure recovery and flow uniformity decreases respectively by 85.71% and 45.84% as the angle of turn increases from 30° to 180°. Curve diffuser with minimum angle of turn 30o, optimum area ratio 2.16 and intermediate Rein 8.163x104 turns out to be the best configuration to provide pressure recovery of 0.399 and flow uniformity of 3.630 m/s.

A Comparative Performance Study of an Ejector-Expansion Refrigeration Cycle Using R134a and its Alternatives: Application of Automobile Air Conditioning

In this study, the performance of ejector-expansion refrigeration cycle (EERC) with R134a alternative refrigerants (R152a, R1234yf, R404A, R407C, R507A and R600a) for automobile air-conditioning application is investigated numerically. The ejector is modeled with a constant mixing-pressure assumption taking into consideration the friction effect in the ejector mixing section. The studied refrigerants are compared based on the optimum area ratio, discharge temperature, compressor input power, volumetric cooling capacity, exergy destruction, COP, exergy efficiency and COP improvement. The results show that R152a and R1234yf have the closest performance to R134a and can be considered the most suitable alternative refrigerants for R134a. The COP and exergy efficiency are improved by 2.26% and 2.27%, respectively, using R152a compared to the use of R134a, whereas they are reduced by 2.89% and 2.88% using R1234yf. The volumetric cooling capacity is reduced for both R152a and R1234yf by 6.14% and 6.8%, respectively. In addition, the effect of compressor rotational speed on the performances is reported.

Transonic Relief in Fans and Compressors

Abstract Every supersonic fan or compressor blade row has a streamtube, the “sonic streamtube,” which operates with a blade relative inlet Mach number of one. A key parameter in the design of the “sonic streamtube” is the area ratio between the blade throat area and the upstream passage area, Athroat/Ainlet. In this article, it is shown that one unique value exists for this area ratio. If the area ratio differs, even slightly, from this unique value, then the blade either chokes or has its suction surface boundary layer separated due to a strong shock. Therefore, it is surprising that in practice designers have relatively little problem designing blade sections with an inlet relative Mach number close to unity. This article shows that this occurs due to a physical mechanism known as “transonic relief.” If a designer makes a mistake and designs a blade with a “sonic streamtube,” which has the wrong area ratio, then “transonic relief” will self-adjust the spanwise streamtube height automatically moving it toward the unique optimal area ratio, correcting for the designer’s error. Furthermore, as the blade incidence changes, the spanwise streamtube height self-adjusts, moving the area ratio toward its unique optimal value, effectively controlling the blade’s incidence range. Without “transonic relief,” supersonic and transonic fan and compressor design would be impossible. This article develops a simple model that allows “transonic relief” to be decoupled from other mechanisms and to be systematically studied. The physical mechanism on which it is based is thus determined and a universal relationship for core compressor preliminary blade design is presented. Finally, its implications in relaxing manufacturing tolerances and in the design of future distortion tolerant blades are discussed.

Effect of the passage area ratio of wick on an ultra-thin vapour chamber with a spiral woven mesh wick

• An ultra-thin vapour chamber with a spiral woven mesh wick is proposed. • The effect of the passage area ratio of wick and test direction on performance is investigated. • The optimum design of the passage area ratio for high heat transfer is provided. • The passage area ratio of wick is adjusted by changing the number of spiral woven meshes. The effect of passage area ratio of wick on the heat transfer performance of the ultra-thin (0.4 mm-thick) vapour chamber (UTVC) which fabricated by brazing bonding was experimentally investigated, the spiral woven mesh (SWM) was utilized as the wick structure and support for the steam chamber of UTVC. The passage area ratio of wick of UTVC was adjusted by changing the number of SWMs. The capillary limits of UTVCs with different passage area ratio of wick were analyzed theoretically. The effect of SWM number and test direction on the thermal performance of UTVCs was experimentally investigated. The results indicated that the maximum heat transport capacity of UTVC increased and then decreased with increasing SWM number. An appropriate SWM number was beneficial to enhance the UTVC’s thermal performance by increasing the vapour-liquid circulation efficiency during heat transfer. The maximum heat transfer capacity of UTVC with 3 SWMs under gravity test direction was 6 W, which was 2 times, 1.4 times, and 1.3 times that of UTVC with SWM number of 1, 2, 4, respectively. The maximum heat transfer capacity of UTVCs changed by less than 10% under different test directions. The optimum passage area ratio of wick of the experimental UTVC was 62.5%.

Characteristics of dimple structure on aluminium silicon alloy fabricated using turning machine

PurposeThis research aims to present the characteristics of dimple structure which was fabricated using a turning machine, where the characteristics include sizes, shapes, area ratio and aspect ratio. This research aims at filling the gap in the machining parameters of previous research in producing dimple by using turning process with the aid of dynamic assisted tooling for turning (DATT). In producing dimple, a carbide insert grade H1 was used on a hypereutectic aluminium silicon alloy (A390) material. Dimple has many advantages such as for reducing friction coefficient, load-carrying capacity and trap wear debris for sliding mechanical components.Design/methodology/approachThere are seven machining parameters (cutting speed, feed rate, depth of cut, frequency, amplitude, rake angle, relief angle and nose radius) which have an influence on dimple produced. Taguchi method (orthogonal arrays L8) was used to conduct the experiment systematically and efficiently for these seven parameters. A carbide insert grade H1 was used as a cutting tool on a turning machine with the aid of DATT. The dimple structure was fabricated on a cylindrical rod hypereutectic aluminium silicon alloy (A390). A profilometer 3D Alicona infinite focus and an optical microscope equipped with Vis software were used to analyse the fabricated dimple structure.FindingsVarious shapes and sizes of ellipse dimples were produced in this research, including short and long drops with lengths in the range of 517.03–3,927.61 µm, widths of 565.15–1,039.19 µm, depths of 14.46–124.87 µm, area ratios of 5.05–25.65% and aspect ratios of 0.007%–0.111%. There were four experiments within the optimal area ratio range of 10%–20%, i.e. the second, third, seventh and eighth experiments. The width of these dimples was 895.95, 961.39, 787.27 and 829.22 µm, length was 826.26, 3163.13, 885.98 and 1026.65 µm, depth was 83.67, 84.19, 87.05 and 110.70 µm and area ratio was 15.12%, 13.14%, 14.79% and 12.70%. The surface roughness of textured surface was below 1 µm. In this research, the results obtained were similar with that of previous researchers on dimple structure related to tribology performance.Originality/valueThere exists machining parameters, namely, cutting speed and frequency, that were not used by previous research in producing dimple. These machining parameters (cutting speed and frequency) were used in this research to produce dimple via turning process with the aid of DATT using carbide insert grade H1. The turning process is an environmentally friendly process which is suitable for mass production for fabricating dimple structure as compared to most of the current methods which are widely used in fabricating dimple structure.

3D Numerical Analyses for Optimization of Deep-Mixing Columns Combined by Raft Foundations

In some cases, because of weak soil, the raft cannot provide sufficient bearing capacity. In these conditions, piles could be applied to enhance the bearing capacity and to reduce the settlements. In this regard, the deep-mixing method is one of the practical ground treatment methods. In this research, the raft foundation modeling combined with deep-mixing columns is performed using FLAC3D with the mixing parameters obtained using experimental uniaxial and triaxial tests. Several parameters such as the effective length, diameter, and distance of the columns and the optimum area ratio of the column group to the raft are investigated in the Firouzkouh loose sand. Then, column group optimization, including length and arrangement, is investigated. Finally, a comparison between using concrete piles and deep-mixing columns in raft foundations is performed.

Modelling and thermodynamic analysis of ejector flow for application at design and off design operating conditions in an ejector air conditioner

Ejector flow in an ejector air conditioning system using R245fa is analysed for entrainment ratio and potential refrigeration effect, at varying temperature and heat input conditions in the generator ranging from 60C to 100C and 2kW to 5kW respectively. The effect of varying generator temperature in cooling capacity of the system when the vapour ejectoris operating at design evaporator and condenser temperatures of 10C and 35C respectively is investigated. The mathematical model of the vapour ejector with optimum area ratio is developed and validated. A critical entrainment ratio of 0.385 is obtained corresponding to generator temperature of 100C. When the generator temperature is varied from 60C to 100C, the cooling capacity range from 0.3kW at generator heat input of 2 kW to 1.78 kW at 5 kW heat input. Further, the operation of the system is analysed for off design operating condition corresponding to reduced heat input rate in the generator. In that case the state of primary refrigerant flow in ejector inlet will be two phase and a mathematical model for two-phase ejector flow is developed and validated. Ejector flow analysis revealed the minimum quality of flow at ejector inlet to maintain adequate backpressure for condensation to occur range from 0.72 at 60C to 0.22 at 100C. The corresponding refrigeration refrigeration effect produced is less than the respective designed operation value byits 12.2% to 8%. Further, analysis of the system shows that at least 7 kW heat input at 100C is required to produce 1 ton of cooling effect.
 Ejector flow in an ejector air conditioning system using R245fa is analysed for entrainment ratio and potential refrigeration effect, at varying temperature and heat input conditions in the generator ranging from 60C to 100C and 2kW to 5kW respectively. The effect of varying generator temperature in cooling capacity of the system when the vapour ejectoris operating at design evaporator and condenser temperatures of 10C and 35C respectively is investigated. The mathematical model of the vapour ejector with optimum area ratio is developed and validated. A critical entrainment ratio of 0.385 is obtained corresponding to generator temperature of 100C. When the generator temperature is varied from 60C to 100C, the cooling capacity range from 0.3kW at generator heat input of 2 kW to 1.78 kW at 5 kW heat input. Further, the operation of the system is analysed for off design operating condition corresponding to reduced heat input rate in the generator. In that case the state of primary refrigerant flow in ejector inlet will be two phase and a mathematical model for two-phase ejector flow is developed and validated. Ejector flow analysis revealed the minimum quality of flow at ejector inlet to maintain adequate backpressure for condensation to occur range from 0.72 at 60C to 0.22 at 100C. The corresponding refrigeration refrigeration effect produced is less than the respective designed operation value byits 12.2% to 8%. Further, analysis of the system shows that at least 7 kW heat input at 100C is required to produce 1 ton of cooling effect.

Manipulating the heat transfer of pool boiling by tuning the bubble dynamics with mixed wettability surfaces

Boiling heat transfer is widely involved in various energy conversion and utilization systems owing to its high heat transfer ecoefficiency even at low temperature differences. It is still a great challenge to control the boiling behaviors due to their multiple influencing factors and their randomness of bubble behaviors. The wettability greatly affects the boiling heat transfer. Hydrophobic surfaces can promote bubble nucleation and increase the heat transfer coefficient of nucleate boiling, while hydrophilic surfaces can promote bubble detachment, inhibiting film boiling, and hence increasing the critical heat flux. In order to meet such mixed requirements of wettability at different boiling stages, we propose a scalable and affordable method to fabricate the hydrophilic / hydrophobic mixed wettability surface. Compared with pure hydrophilic or superhydrophobic surfaces, the mixed surfaces exhibit higher heat transfer coefficient than the hydrophilic surface at low superheat degrees but larger critical heat flux than the hydrophobic surface at high superheat degrees. Therefore, the mixed wettability surfaces are more adaptable for a wider range of inputted heat flux. Such boiling heat transfer characteristics is the resultant of the unique bubble dynamics. The bubbles are likely to pinned on the hydrophobic spots but more easily detach from hydrophilic area. Tuning the hydrophilic / hydrophobic area ratio can manipulate the bubble dynamics. A numerical model is used to mimic the boiling on the hydrophilic / hydrophobic mixed surface, which agrees with the experimental results. And then the optimal area ratio is suggested by a boiling phase diagram based on a large number of simulations with various area ratios. Besides proposing a scalable and affordable way to fabricate the hydrophilic / hydrophobic mixed wettability surface, we also provide details of bubble dynamics on the pure or mixed wettability surfaces. Such details facilitate to understand the enhancement mechanisms of boiling heat transfer on mixed surface, which is still an open issue. The effects of the area ratios on the heat transfer coefficient are also discussed, which would provide a guideline to fabricate the mixed boiling enhancement surfaces.

Performance assessment of solar chimney power plants with the impacts of divergent and convergent chimney geometry

Abstract Influence of area ratio (AR) on main performance parameters of solar chimney power plants (SCPPs) is investigated through a justified 3D axisymmetric CFD model. Geometric characteristics of Manzanares pilot plant (MPP) are taken into consideration for the numerical model. AR is varied from 0.5 to 10 to cover both concave and convex (convergent and divergent) solar chimney designs. Following the accuracy verification of the CFD results and proving mesh-independent solution, main performance oriented parameters are assessed as a function of AR such as velocity, temperature and pressure distribution within MPP, temperature rise of air in collector, mass flow rate of air around the turbine area, dynamic pressure difference across the turbine, minimum static pressure in the entire plant, power output and system efficiency. The results reveal that AR plays a vital role in performance figures of MPP. Mass flow rate of air ($\dot{m}$) is found to be 1122.1 kg/s for the reference geometry (AR = 1), whereas it is 1629.1 kg/s for the optimum AR value of 4. System efficiency (η) is determined to be 0.29% for the reference case; however, it is enhanced to 0.83% for the AR of 4.1. MPP can generate 54.3 kW electrical power in its current design while it is possible to improve this figure to 168.5 kW with the optimal AR value.

Research on turning maneuverability of submerged glider of the wave glider

Turning Maneuverability is an important hydrodynamic performance of the wave glider, which can realize the position keeping, path tracking and steering obstacle avoidance in a reliable way. The influences on the maneuverability of the relevant parameters of the rudder are analyzed by using the Computational Fluid Dynamic (CFD) method in this paper. Through the analysis, the conclusions that the optimal rudder area ratio with 0.15 and the aspect ratio with 0.8 are drawn. Furthermore, the position and profile of the rudder are also analyzed. To verify the validation of the work, sea trial data of the “Black Pearl” wave glider is adopted and analyzed. The result shows that the simulation analysis of the turning maneuverability of submerged glider is correct. And the conclusions have great significance for improving the turning maneuverability of the wave glider and the parameter design of the submerged glider engineering prototype from the perspective of the engineering application.

Daylight performance assessment of atrium skylight with integrated semi-transparent photovoltaic for different climate zones in China

The utilization of atriums in large space public buildings has significantly improved the internal lighting performance, but due to the harsh external environment, the application of large-scale skylights also brings higher heating or cooling energy consumption. Skylight Integrated Photovoltaic (SIPV) technology can not only use solar energy efficiently, but also has a significant shading effect, avoiding direct impact on the indoor light and thermal environment. At present, quite limited researches have studied the uncomfortable light environment of atrium caused by the application of semi-transparent photovoltaics in skylights. Therefore, it is very important to propose effective solutions to improve the daylight performance of these spaces or those with similar daylight climates.In this work, the indoor light environment has been systematically investigated through simulation employing DAYSIM tool. Both static and dynamic simulation analysis were carried out over the selected skylight glass to determine its appropriate area ratio of photovoltaic materials for representative Chinese cities. The optimal area ratio parameter range of thin film (TF) and crystalline silicon (C-Si) photovoltaic materials resulted in range of: 50–60% for both TF and C-Si in Xi'an represented area; 60–70% for TF, and 50–70% for C-Si in Beijing represented area; 50–60% for TF, and 60-70% for C-Si in Shanghai represented area; 50–60% for TF, and 50-70% for C-Si in Guangzhou represented area; 40–60% for TF, and 40-60% for C-Si in Harbin represented area; 30–50% for both TF and C-Si in Chongqing represented area. The optimal area ratio based design strategies of SIPV under various climatic conditions were then summarized.

Orta ve Yüksek Katlı Betonarme Binalarda Optimum Perde Duvar Alanının Belirlenmesi Yönelik Parametrik Çalışma

In this article, a structural analysis was conducted on a total of 40 building models withvarying building height and wall dimensions in order to determine the optimum ratio of shear wall areato floor area in a reinforced concrete building. For this purpose, 20, 30 and 40 story buildings wereselected to investigate the effect of varying building heights on their structural behaviors. A parametricstudy on shear wall areas was conducted base on varying shear wall area to floor area ratios. Buildingmodels, therefore, included no wall and walls with 0.5%, 1%, 1.5% and 2.0% area ratios applied incombined x and y directions. Each of these models was subjected to response spectrum analysis usingthe forces generated according to the 2018 dated Turkish Earthquake Code (TEC 18) and 2016 datedAmerican Building Code (ASCE 7-16). The buildings were assumed to be all office buildings located in asevere seismic zone region, Avcilar, Istanbul. The 30 and 40 story buildings due to their total heights hadto be considered tall in line with the requirements in TEC 18. The additional requirements were alsoincluded in the analysis to understand the impact of tall buildings on the optimum shear walldetermination. Therefore, the following parameters were investigated for the optimum shear wall areato floor area ratio: (a) building periods, (b) base shear and shear forces resisted by all shear walls, and (c)maximum lateral displacements and story drifts. The impact of effective wall layout configuration onstructural behavior was also investigated by studying the 2.0% wall area ratio. The results indicated thatthe most effective ratios of shear wall area to floor area for the 20 and 30 story buildings were equal to1.5% and 2.0%, respectively. However, the need for the wall area of the 40 story building was slightlymore than 2.0%. However, as the wall layout was revised for the building with the 2.0% wall area ratio,the requirement for the wall area was nearly met indicating that the 2.0% wall area ratio could also berecommended for the 40 story building.

A cylindrical mixing chamber ejector analysis model to predict the optimal nozzle exit position

By introducing the theory of an annular mixing-layer, a new model to predict the optimal nozzle exit position (ONXP) is established and verified for ejectors with a cylindrical mixing chamber. Furthermore, the optimal entrainment ratio, area ratio and dimensionless optimal nozzle exit position (DONXP) of ejectors under different working conditions are analysed by this model. Compared with the experimental data of R141b, R245fa, R134a and R600a ejectors, the entrainment ratio error is within ±10.70%, and the critical backpressure is within ±7%. The introduced theory can accurately predict the ONXP of the R245fa ejectors (within an error of ±15.85%) and the DONXP distribution of the R141b ejectors, and can properly predict the performance of the R134a ejectors under the same dimensions. With an increasing compression ratio, the DONXP decreases, and the rate of decrease is faster when the compression ratio exceeds the value of the inflection point. The compression ratio corresponding to the inflection point is higher for an ejector with a large expansion ratio than that with a small expansion ratio. In addition, the DONXP decreases when the expansion ratio increasing under a small compression ratio while increases when the expansion ratio increasing under a large compression ratio.

Performance assessment of a V-trough photovoltaic system and prediction of power output with different machine learning algorithms

This study carried out in two stages. In the first stage, four different-sized layers were designed and manufactured for a concentrated photovoltaic system. These layers were used to change the concentration ratio and area ratio of the system. Furthermore, a new power coefficient equation with this paper is proposed to the literature for the determination of the system performance. In the second stage of the study, the power outputs measured in the study were predicted with four machine-learning algorithms, namely support vector machine, artificial neural network, kernel and nearest-neighbor, and deep learning. To evaluate the success of these machine learning algorithms, coefficient of determination (R2), root mean squared error (RMSE), mean bias error (MBE), t-statistics (t-stat) and mean absolute bias error (MABE) have been discussed in the paper. The experimental results demonstrated that the double-layer application for the concentrator has ensured better results and enhanced the power by 16%. The average concentration ratio for the double-layer was calculated to be 1.8. Based on these data, the optimum area ratio was determined to be 9 for this V-trough concentrator. Furthermore, the power coefficient was calculated to be 1.35 for optimum area ratio value. R2 of all algorithms is bigger than 0.96. Support vector machine algorithm has generally presented better prediction results particularly with very satisfying R2, RMSE, MBE, and MABE of 0.9921, 0.7082 W, 0.3357 W, and 0.6238 W, respectively. Then it is closely followed by kernel-nearest neighbor, artificial neural network, and deep learning algorithms, respectively. In conclusion, this paper is reporting that the proposed new power coefficient approach is giving more reliable results than efficiency data and the power output data of concentrated photovoltaic systems can be highly predicted with the machine learning algorithms.

Characterization of Al-induced electroless tin films on mild steel substrate for corrosion protection

Al-induced electroless process is used to fabricate Sn films on the mild steel substrates. The deposition reaction was performed by designing a Fe-Al galvanic couple where the optimum geometric area ratio between Fe-Al was 0.3. Additionally, NaBH4 and NaH2PO2 reducing agents were also added to enrich the deposit morphology and composition. The film surfaces were characterized by scanning electron microscopy, energy-dispersive x-ray spectroscopy and x-ray diffraction measurements. The analysis showed dense, uniform tin deposits with the presence of boron and phosphorous. The x-ray diffraction results confirmed the polycrystalline tetragonal structure with mostly (211) texture having an average 18 nm crystallite size. The anti-corrosion performance of these tin films has been studied by immersion in saltwater, open circuit potential measurement test, potentiodynamic polarization test, and electrochemical impedance spectroscopy. The effect of the coating thickness was also considered in anti-corrosion performance. The analysis showed the tin coated steel has commendable corrosion resistant property and the corrosion rate can be decreased up to 16 times with the addition of these coatings irrespective of the film thickness.

Flow Analysis and Theoretical Design of Diesel Engine Exhaust Port

Exhaust port is an important part of a diesel engine which affects the combustion and emission. It is important to have a good design for exhaust port. In this paper, the calculation formula of the optimal area ratio (Kopt) of outlet and inlet of exhaust port was derived. The formula shows that Kopt is only determined by relative pressure difference (RPD). Then influence of the area ratio (K) of outlet and inlet on flow capacity of exhaust port and the trend of Kopt with relative pressure difference were studied numerically to verify the validity and applicability of the formula. The numerical results shows that the mass flow rate increases first and then keeps constant with the increase of K at the same RPD. Kopt exists and decreases first and then keeps constant with the increase of RPD. The numerical trend is consistent with theoretical trend and the errors between maximum mass flow rates of numerical results and actual mass flow rates at theoretical optimal area ratios are all less than 5% meeting engineering accuracy. It is indicated that the derived formula is correct and applicable. When an exhaust port is designed, the outlet area can be estimated by this formula.

Flow-induced noise analysis for natural gas manifolds using LES and FW-H hybrid method

In this paper, the flow-induced noise generated by natural gas manifolds is analyzed. A noise experiment is carried out to validate the present numerical model. The characteristics of the flow-induced noise, including sound source distribution, sound directivity and frequency spectra, are investigated numerically. The effects of relevant parameters on overall sound pressure level are also analyzed quantitatively, including gas outlet pressure, inlet velocity, and the section area ratio of distribution pipe to inlet/outlet pipes. The main impact factors are evaluated using the orthogonal experimental design and the grey relational analysis method. Furthermore, proper noise reduction measures are also proposed. The results show that the manifold noise is middle and low frequency noise, and the energy of manifold noise is mainly concentrated in the range of 50–1150 Hz. The peak noise dominantly radiates at the directions of 75–105° along the gas flow. The gas inlet velocity should be controlled below 25 m/s. The optimal section area ratio of distribution pipe to outlet pipes should be below 2, while the section area ratio of distribution pipe to inlet pipes should be greater than 4. Gas inlet velocity and the section area ratio of distribution pipe to outlet pipes are the most important impact factors. In addition, some passive measures like noise absorption cover, and isolation hoods or walls, are recommended to reduce the flow-induced noise.