This paper presents a strategy to reduce exhaust noise in fuel cell vehicles. It focuses on optimizing the exhaust system. The innovation is an integrated muffler device. It combines a vapor separator and an absorptive-reactive muffler. The vapor separator removes moisture from exhaust gases. This prevents damage to sound-absorbing materials. It keeps mufflers functional for longer. Fuel cell vehicles produce noise across a wide frequency range. This makes noise reduction challenging. The absorptive-reactive muffler improves noise attenuation. It works across the full frequency spectrum. The combination of the separator and muffler enhances noise reduction. Simulations show high transmission loss. They also confirm acceptable back pressure. Real-vehicle testing supports these results. The optimized system reduces idle noise by 22.1 dB(A). This is a 32.4% reduction. Blowdown noise is reduced by 46.3 dB(A), or 40.1%. Full-throttle noise drops by over 20 dB(A), a 17.2% decrease. The design significantly reduces exhaust noise. It offers a new approach to noise control.

The mass transport and ohmic losses in proton exchange membrane fuel cells (PEMFCs) is significantly influenced by the channel to rib width ratio (CRWR), particularly when accounting for the interfacial contact resistance between bipolar plates (BPs) and gas diffusion layers (GDLs) (ICRBP-GDL). Both the determination of the optimal CRWR value and the development of an efficient flow field structure are significantly influenced by ICRBP-GDLs. To investigate this, three-dimensional numerical models were developed, revealing that selecting an optimal CRWR tailored to specific ICRBP-GDL values can effectively balance mass transport and ohmic losses. Building on this insight, a novel island two-dimensional flow field design is proposed, demonstrating the ability to enhance oxygen transport to the catalyst layer (CL) and achieve a more uniform oxygen distribution without increasing ohmic losses. Compared to conventional straight and serpentine flow fields, the island flow field improves output power density by 4.5% and 3.5%, respectively, while reducing the liquid water coverage ratio by 30%. Additionally, the study identifies optimal CRWR values for conventional flow fields corresponding to ICRBP-GDLs of 2.5, 5, 10, 20, and 40 mΩ·cm2 as 1.5, 1.5, 1.0, 0.67, and 0.43, respectively. For the island flow field, the optimal CRWRs are consistently smaller—1.5, 1.0, 0.67, 0.43, and 0.43—due to its superior mass transfer capability. This work provides a valuable framework for optimizing flow field designs to achieve improved PEMFC performance.

为探究同轴电缆屏蔽效能的影响因素,基于屏蔽衰减的三同轴法搭建测试台,评估车载通信同轴电缆及连接器的屏蔽效能.试验研究了同轴电缆屏蔽层、末端连接器和分段对屏蔽效能的影响,并获得0.1 MHz～3 GHz内的屏蔽效能测试数据.分析结果表明,对于车载通信同轴电缆RG174系列,双层屏蔽比单层屏蔽的屏蔽效能高10～15 dB,电缆分段及末端连接器均会降低其屏蔽效能,带有末端连接器且分段的电缆屏蔽效能降低更明显,降幅可达10 dB,并且末端连接器会改变电缆的截止频率.研究结果可用于指导车载通信同轴电缆的选用及分段布局设计,解决车载通信设备在电缆及其连接部位的电磁发射和受扰等电磁兼容问题.

As the power performance of electric vehicles continues to improve, the human body may be exposed to electromagnetic threats in the cabin. This study tested an electric vehicle to analyze the low-frequency magnetic field distribution in the cabin and to assess the safety of human low-frequency magnetic field exposure. A simulation analysis of human electromagnetic exposure was carried out to obtain the magnetic flux density, induced electric field strength and induced current density, and the test results were much lower than the limits specified in GB8702-2014 and the International Commission on Non-Ionizing Radiation Protection, and the relative error between the simulation results and the test results was <15%. This paper investigates the frequency, driving current, vehicle body material and cable layout to explore the law of human body induced electromagnetic field changing with power cable current, and provides theoretical reference for the design of human body low-frequency magnetic field protection.

In order to study the mutual interference between fuel cell's components and improve anti-interference ability of sensitive components, a test system for DC/DC converter, Air Compressor Controller (ACC), and FCU controller is established, and radiation emission measurements is conducted. Then, measurement results of DC/DC converter and ACC were used as interference sources, and a simulation model was established. The interference current signals on the DC/DC converter and ACC cables were collected as excitation sources for the simulation model. The impact of two components on the FCU controller was studied. The results showed that the coupling current on the FCU controller cable could exceed 100mA and limit. In addition, the simulation model was used to study the radiation anti-interference characteristics of the FCU controller after adding a cable shielding layer. Under the plane wave interference of 25V/m~100V/m, the induced current on the FCU controller cable was small, which will not affect the normal operation of the FCU controller.

A 3D + 1D model is developed to investigate the effect of liquid water in cathode channels on oxygen trans-portation. The gas-liquid interface is tracked by volume of fluid (VOF) method and the oxygen transportation is solved by a species transport model. It is found that the existence of liquid water in channels can hinder the transportation of oxygen towards catalyst layers. The water coverage is a key factor that affects the oxygen transportation. It is influenced by the droplet numbers, volumes, contact angles and liquid regimes. Compared to the case with 0 droplet, the current densities for the cases with 6 and 12 droplets decrease by 1.4% and 10.6% respectively, for the cases with a droplet volume of 0.05 mu L, 0.1 mu L, 0.2 mu L and 0.3 mu L decrease by 1.7%, 3.9%, 9.6% and 14.9% respectively, for the cases with the contact angles of 115 degrees, 125 degrees, 135 degrees, 145 degrees and 155 degrees decrease by 15.2%, 13.8%, 9.6%, 6.6% and 5.3% respectively. Compared to the droplet regime, the current densities of the film regime with the water volume of 1.2 mu L and 2.4 mu L increase by 3.6% and 9.4% respectively.

Thermal barrier coatings (TBCs) have been widely used in high-power engine components because of their excellent thermal insulation properties. In this study, microcrack growth and fatigue life analysis of TBCs were carried out based on thermal shock tests of TBCs samples. Scanning electron microscopy (SEM) was used to observe the spallation and vertical crack growth behavior of TBCs during the tests. The fatigue life prediction model applied to piston TBCs was developed by modifying the Paris equation with the sintering of the coating and the effect of a thermally grown oxide (TGO) layer being considered. The model was calibrated by conducting tests on piston TBCs, and the forecasting error was less than 15%, indicating that the prediction model is both practical and effective. The results of this study provide a service life evaluation and test method for TBCs on pistons, which can be utilized to guide piston TBCs design.

The dynamics of water droplets on fiber layers are investigated by fiber-scale simulation using volume of fluid (VOF) method. The effects of fiber spaces, contact angles at fibers and numbers of layers on droplet dynamics are investigated. Force analysis for the pinned and moving droplets on fiber layers shows that the resistant forces from the wetted fibers at the edge positions rather than middle positions are the dominant force to control the droplet mobility. Force analysis for droplets on the dual-layers fiber layer are also conducted. The results show that the second layer contributes little to hinder the droplet directly due to the insignificant resistant force they provided. However, the second fiber layer enhances the total resistant force from the first layer. Furthermore a simplified model is used to compare with the fiber model. The results indicate that the simplified model can also be used to predict the droplet mobility once the contact angle is given.

The centrifugal fan blades of the high-speed train ventilation and cooling system are subjected to cyclic loading which will shorten the life of fan blades. It could cause an accident of the high-speed-train in service. In this study, a modified method based on the nominal stress method was proposed and developed for the fatigue life prediction of centrifugal fan blades. The finite element model was firstly used to analyze the mode and the stress of fan blades based on the typical material property. The fatigue life was predicted based on the physical curve, using the Miner’s cumulative damage rule to calculate total damage. In order to verify the effectiveness of this method, the experimental tests were conducted on fan blades using a fatigue bench system, which were the typical structure of the ventilation cooling system of the high-speed-train. The damage mechanisms of blades was deduced from the fracture fractographs. The ventilation good correlation was achieved between the prediction model and the actual experimental results, testifying the practicability and effectiveness of this proposed method. Thus, the research result can reduce the probability of accidents caused by the fan blade damage and improve the reliability of the ventilation cooling system of the high-speed train.

The use of metal shell is an effective method to solve electromagnetic interference caused by printed circuit board (PCB) of electronic equipment. Electromagnetic leakage mainly occurs at the junction of the upper metal shell and the lower metal shell. In order to reduce the electromagnetic interference caused by the electromagnetic leakage, the conductive adhesive is coated on the connection between the upper shell and the lower shell. In this paper, a simulation model of shielding effectiveness is established in CST STUDIO SUITE. It is mainly used to calculate the effects of conductivity and geometric size of conductive adhesives on shielding effectiveness. In the actual design process of electronic equipment, we can find a more economical combination of size and conductivity of conductive adhesives through the simulation of shielding effectiveness. The results can be used to guide the design of conductive adhesives to solve the electromagnetic compatibility problems of electronic equipment.

Fan is widely used in industry as a very important component of pressure transmission and system cooling. Fan blade is the key part which decides the service life of fan and the whole system. In this paper, the research focuses on the centrifugal fan of high-speed train cooling system and the blades on it. The experimental system and research method of fatigue analysis and fault diagnosis are built. The fan can work in both steady and unsteady state conditions controlled and driven by the test system. At the same time, the signals of strain and acceleration at different positions can be obtained accurately. Based on the static tension and dynamic fatigue test of the material, the accurate simulation of the fan is carried out. By simulation analysis, steady-state test, long-time start-stop test and metallographic test, the prediction of fatigue life of fan blades is conducted with in-depth analysis and comprehensive evaluation. The results show that fan meets the requirements of actual working life. As the actual working state is more diverse and severe than the above test process, some phenomena of damage also appear in the blades after service. Based on real situation, the blade faults are classified. After determination of measuring point position, the vibration signals of four fault states of blade under rated speed are collected. This paper proposes a new fault feature extraction method - the Refined Generalized Multi-Scale Entropy (RMSE sigma 2) combined with Support Vector Machine (SVM). According to the results of the empirical mode decomposition (EMD), the effective intrinsic mode function (IMF) components are selected by energy distribution and correlation coefficient. The comparative analysis of multi-scale entropy (MSE), generalized multi-scale entropy (MSE sigma 2) and RMSE sigma 2 between the original signal and 1-8 IMF components are carried out. Results show the RMSE(sigma 2 )of IMF1 component of Z direction of point 1 is the best choice. And it is imported into SVM for pattern recognition with scale factor 20. The optimal SVM model is obtained by choosing kernel function and parameters that are optimized by Particle Swarm Optimization (PSO) method. The results show the faults of centrifugal fan blades can be classified accurately. A set of research flow and method is set up, which provides important reference for fatigue and fault pattern recognition of fan blades in the future. (C) 2020 Elsevier Ltd. All rights reserved.

A model describing NH3 selective catalytic reduction (NH3-SCR) over Cu-ZSM-5 to investigate the effects of intraphase and interphase mass transfer on standard SCR reaction is developed and further verified with the synthetic gas bench. The correlation between tortuosity and porosity has been analyzed by least squares method and applied to the sinuousoidal capillary bundle model. The effects of washcoat thicknesses, lengths, cell densities and channel widths on the standard SCR reaction are analyzed in temperature range of 150-500 degrees C. It is found that deNOx efficiency is affected by intraphase diffusion limitations at 200-500 degrees C and by interphase mass transfer limitation at intermediate (250-400 degrees C) and high temperatures (400-500 degrees C). As the temperature increases, the reaction is firstly controlled by kinetics, with the kinetics resistance decreasing and then increasing until the maximum among three processes. Furthermore, intake flow rates (GHSVs) play an important role impacting NO conversion on NH3-SCR. (C) 2019 Elsevier Ltd. All rights reserved.

The Selective catalytic reduction (SCR) technology is an effective and economical method for reducing NOx emissions from the heavy duty diesel engine. To ensure a reasonable design of the SCR system, it is critical to understand the effects of space velocity (GHSV), NO2/NOx ratio, NH3/NOx ratio and structural parameters of the SCR reactor on the NOx conversion efficiency. Using the experimental method to conduct all the investigations though the entire development cycle of SCR system is expensive and would cost a long time. Numerical method as a complementary tool to bench tests can help to optimize the design and shorten the development cycle of SCR system. In this paper, a mathematical model is developed to predict the NOx conversion efficiency over a Cu catalyst. The model is calculated in the MATLAB environment. The simulation results agree well with the experimental data, which indicates that the mathematical model is reliable and can effectively predict the performance of the SCR catalytic system. Then the effects of the parameters, such as space velocity, NO2/NOx ratio, NH3/NOx ratio, length, diameter and number of channels per square inch (CPSI) of the SCR reactor on the NOx conversion efficiency were studied. (C) 2019 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

•The effect of the mixers on the droplets residence time is investigated.•The use of mixers changes the droplets size distribution.•The mixers help to improve urea conversion and NH3 distribution uniformity.

应用计算流体力学(computational fluid dynamics,CFD)软件建立了尿素溶液的喷射雾化和蒸发分解模型,喷雾与壁面相互作用模型和尿素选择性催化还原(SCR)催化器的NOx催化反应模型.研究了叶片型混合器不同布置方案对尿素溶液雾化、蒸发和分解及催化剂入口NH3分布均匀性的影响.数值计算结果显示:叶片型混合器能够提升尿素喷雾雾化效果,提高尿素蒸发分解效率,改善NH3的分布均匀性.混合器布置在离喷嘴1倍排气管直径的位置,SCR系统具有最佳的喷雾雾化效果和尿素分解效率;混合器布置在3倍排气管直径的位置,SCR系统具有最佳的NH3分布均匀性.台架试验和数值计算结果表明:混合器布置在距离喷嘴1倍排气管直径位置时,SCR系统具有更高的NOx的催化转化效率.

以Langmuire Hinshelwood机理为理论依据,基于MATLAB/Simulink建立DOC系统的数值计算模型,研究不同参数(如空速、氧气浓度、NO2/NOx比例)对氮氧化物(NOx)、一氧化碳(CO)、碳氢化合物(HC)转化效率的影响,并对部分工况进行了实验研究,从而验证数值模型的准确性.结果表明,空速的降低可以增大DOC对CO、HC、NO的氧化性能,这是由于排气在催化器内的反应时间增长.当排气温度为225～300℃时,减小空速对增大HC的氧化效率效果明显,当排气温度在175～450℃范围内,减小空速对增大NO的氧化效率影响明显;当O2浓度低于1％,排气温度在175～250℃时,CO转化效率增大,在250℃之后均接近100％.当O2浓度为10％时,温度的变化对CO的转化效率影响很小.当O2浓度大于1％时,温度的变化对NO的氧化效率影响较大;当排气温度在300～550℃时,NO2/NOx比例的变化对NO的转化效率影响较大.降低排气中NO2/NOx比例,能够在排气温度高于300℃时,明显提高NO的转化效率.

The bulk current injection with substitution method is applied to the electromagnetic compatibility (EMC) test of automotive components. In this paper, the experimental characteristics of the device under test (DUT) with differential- mode bulk current injection and common-mode bulk current injection are studied. Also, the effects of the location of the bulk current injection probe are studied briefly. The test setup is in compliance with the ISO 11452-4 standard and the applicable frequency range is 1 MHz to 400 MHz. The results show that, due to the resonance phenomenon, the current coupled into the wiring harness in the common-mode bulk current injection test is sometimes less than the current coupled into the wiring harness in the differential-mode bulk current injection test. Moreover, the current coupled into the wiring harness is related to the location of the current injection probe, and the effects of the location are different in different frequency bands. However, in the ISO11452-4 standard, only common-mode bulk current injection test is considered in the bulk current injection immunity test. Therefore, in order to accurately reflect the true immunity level of the DUT, the differential-mode bulk current injection test should be considered in the ISO 11452-4 standard.

In order to investigate the catalytic performance of diesel engine integrated after-treatment system,the numerical simulation model which including NO oxidation,urea decomposition and SCR reaction were set up and the catalytic performance were studied by using CFD software.The catalytic efficiency of system at different exhaust temperature and NSR calculated after installing DOC and CDPF catalysts on upstream of SCR catalyst.The results show that when the temperature reaches 300℃ above,the decomposition efficiency of urea can reach about 81％;NO oxidation efficiency can reach about 45％ to 60％,the system has a good low temperature NOx catalytic efficiency,up to 76.6％ at 200℃;when the NSR is 1.0,the NOx catalytic efficiency is higher than 90％ at most of the conditions,the highest is up to 98.7％.The absolute error of the calculation and experimental results is less than 5％ through the bench test,which shows that the simulation results are reliable and can provide theoretical guidance for the matching optimization of the system.

To improve the actual performance of internal combustion engine (ICE), the transient behaviors of in cylinder combustion and heat-work conversion processes of ICE were investigated and an optimization method was proposed. Based on an advanced turbocharged gasoline direct injection (TGDI) engine, the steady-state bench test, load-step test at constant-speed and vehicle road test were carried out. On this basis, the in-cylinder combustion and heat-work conversion processes of vehicle engine under load-step and vehicle driving conditions were compared with the steady-state results. By this means, the deviations of ICE transient performance from their steady-state values were demonstrated and also their impacts were revealed. The research results show that there is a satisfactory consistency of ICE performance especially the ignition advance angle under load-step and steady-state conditions. However, under vehicle driving conditions, the operating and control parameters gravely deviate from the steady-state values with large fluctuations, e.g., ignition advance angle is retarded largely under the sharp deceleration conditions. When the IMEP is below 4 bar, the ignition advance angle seriously deviates from the steady-state values; which results in large fluctuation of combustion characteristic parameters and finally leads to the decrease of heat-work conversion efficiency. Moreover, the fluctuation of excess air coefficient is one of the main reasons for the instability of ICE transient performance. To accurately control the ignition timing under low load and decrease the fluctuation of excess air coefficient is an effective way to improve the ICE performance under vehicle driving conditions. (C) 2016 Elsevier Ltd. All rights reserved.