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The rapid increase of the number of motor vehicles, especially motorcycles, makes serious problem caused by the pollution from gas emission of fossil fuel combustion. The problems related to human health and the erosion on ozone layer is credited to its gas emission. Several dangerous and toxic gasses such as Hydrocarbon (HC), Carbon Monoxide (CO), and Nitrogen Oxide (NOx), Sulphur Dioxide (SO2), and Lead (Pb) are emitted during IC engine operation. To manage those dangerous gasses, catalytic converter which converts the gasses into more eco-friendly CO2H2O and N2 may be employed. In this research, a specially designed catalytic converter made from brass (CuZn) wire in the form of spider web pattern was fitted into exhaust system of a standard motorcycle. The performance of the converter for several engine rotation speeds was examined by measuring CO and HC of exhaust by using Gas Analyzer. By comparing the exhaust of a standard exhaust system and modified exhaust system (fitted with converter), it can be concluded that the converter was able to decrease the exhaust emission gas. For HC content, the percentage of decrease was as much as 36,88 % for converter fitted exhaust system compared to 61.12% for standard one. For CO content, the decrease percentage was 19.90% compared to 80.10% for standard one.

Platinum group metals (PGMs) assume an important role within the chemistry and chemical engineering due to their exceptional chemical stability in high temperatures and various environmental conditions. Their unique attributes make them highly demanded materials across an array of industries. Nevertheless, the gradual depletion of PGM reserves underscores necessitates of recycling PGM-containing waste as a means to ensure the reasonable utilization of resources. Recycling of catalytic waste, in particular, presents a more cost-effective and environmentally sustainable approach acquiring these metals, in contrast to the conventional practice of mining from natural ores. Of particular importance are spent automotive catalysts, which represent a valuable source of platinum group metals, featuring substantially higher PGM concentrations than their naturally occurring counterparts. Conventionally, the recovering of PGMs from waste materials predominantly employs hydrometallurgical and pyrometallurgical processes. Unfortunately, these established techniques entail the utilization of potent oxidizing acidic solutions, including aqua regia and hydrochloric acid with chlorine gas, which exert adverse ecological consequences. In recent years, there has been a growing focus on the development of alternative methodologies that are both environmentally friendly and economically viable for the recovery of PGMs from spent catalysts. Notable among these emerging techniques are solvometallurgy, molecular recognition technology, and magnetic separation. This comprehensive review endeavors to study and assess the latest advancements in the recovery of platinum group metals from spent catalysts, meticulously evaluating their respective advantages and disadvantages. Through an analysis, this review aspires to identify the most promising method - one that combines environmental friendliness and economic feasibility., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)

PROMETHEUS catalyst, a copper-based polymetallic nano-catalyst has been proven to be suitable for automotive emission control applications. This novel catalyst consists of copper, palladium and rhodium nanoparticles as active phases, impregnated on an inorganic oxide substrate, CeO2/ZrO2 (75%, 25%). The aim of PROMETHEUS catalyst’s development is the substitution of a significant amount (85%) of Platinum Group Metals (PGMs) with copper nanoparticles while, at the same time, presenting high catalytic efficiency with respect to the commercial catalysts. In this work, an extensive investigation of the catalytic activity of full scale PROMETHEUS fresh and aged catalyst deposited on ceramic cordierites is presented and discussed. The catalytic activity was tested on an Synthetic Gas Bench (SGB) towards the oxidation of CO and CH4 and the reduction of NO. The loading of the washcoat was 2 wt% (metal content) on Cu, Pd, Rh with the corresponding metal ratio at 21:7:1. The concentration of the full-scale monolithic catalysts to be 0.032% total PGM loading for meeting Euro III standard and 0.089% for meeting Euro IV to Euro VIb standards. The catalytic activity of all catalysts was tested both in rich-burn (λ = 0.99) and lean-burn conditions (λ = 1.03).

In this study, material flow analysis (MFA) is applied to quantify and reduce the obstacles for advancing a circular economy (CE) of platinum (Pt) from catalytic converters (CC) in Europe. First, the value chain and related stakeholders are mapped out in an MFA‐like model to both facilitate the assessment of stocks and flows, and get a comprehensive view of potential action levers and resources to close‐the‐loop. Then, through the cross analysis of numerous data sources, two MFA are completed: (i) one general MFA, and (ii) one sector‐specific MFA, drawing a distinction between the fate of Pt from (a) light‐duty vehicles, under the European Union's End of Life Vehicle Directive 2000/EC/53, and (b) heavy‐duty and off‐road vehicles. Key findings reveal a leakage of around 15 tons of Pt outside the European market in 2017. Although approximately one quarter of the losses are due to in‐use dissipation, 65% are attributed to insufficient collection and unregulated exports. Comparing the environmental impact between primary and secondary production, it has been estimated that halving the leakage of Pt during usage and collection could prevent the energetic consumption of 1.3 × 103 TJ and the greenhouse gases emission of 2.5 × 102 kt CO2 eq. Through the lens of circularity indicators, activating appropriate action levers to enhance the CE performance of Pt in Europe is of utmost importance in order to secure future production of new generations of CC and fuel cells. Moreover, the growing stockpile of Pt from CC in use indicates the need for better collection mechanisms. Also, the CC attrition during use and associated Pt emissions in the environment appears non‐negligible. Based on the scarce and dated publications in this regard, we encourage further research for a sound understanding of this phenomenon that can negatively impact human health. [ABSTRACT FROM AUTHOR]

In recent years, the permissible limits of engine exhaust emissions are reduced considerably. Hence a quick warm-up and high conversion efficiency of the catalyst system is essential to meet upcoming stringent emission regulations. In the present work, the transient thermal behavior of an oxidation catalyst is studied using a one-dimension mathematical modeling approach with the focus on CO oxidation for dual-fuel engine application. At first, the heat generation due to chemical reactions is considered negligible for studying the warm-up behavior. Upon obtaining a good agreement between predicted warm-up temperature profiles with available literature data, the effect of an electrical heater on the warm-up behavior is investigated. The model is then extended by incorporating heat generation due to CO oxidation. A simplified reaction rate model is considered in order to reduce the computational complexity. It is observed that the simplified model agrees well with the experimental data for both low and high levels of CO concentration at the inlet, typical in dual-fuel technology when an engine is operated under diesel and dual-fuel modes, respectively. [ABSTRACT FROM AUTHOR]

• Improved pressure drop model for a honeycomb monolith system. • Multi-zone permeability accounts for all observed effects in single channel model. • Includes all entrance and exit effects and developing flow pattern. • Model extended to continuum porous medium mode for entire converter. • Velocity profile in converter closer to experiment than single permeability model. This paper presents an improved model for pressure drop in a honeycomb monolith reactor, which configuration is widely used in automotive exhaust gas after treatment systems. The model is based on pressure drop simulations for single channel models complemented with large eddy simulation. The model has multiple zones, and accounts for the pressure losses for flow entering, passing through, and leaving the substrate. The new multi-zone model is theoretically more consistent than those that use a single permeability for the whole the monolith, and it gives a superior result for pressure drop and hence flow distribution. [ABSTRACT FROM AUTHOR]

This work compares two studies in which the spark ignition gas engine test was used with typical biogases generated in the rice industry: Bio70 (Study 1), Bio65 (Study 2), Syngas1 and Syngas2 (in both studies). Methane (Study 1) and natural gas (Study 2) were also used. From these studies, three different ignition advance angles were chosen: 20°, 35°, and 55°, to compare and analyze the effects of these fuels and their mixtures inside the engine. The emissions were also evaluated using a three‐way catalytic converter connected to the engine. Study 1 demonstrated lower CO and hydrocarbon (HC) emissions than Study 2 for all conditions and all fuels, whereas NOx emissions varied according to the engine operating conditions (λ and ignition advance angle). Except in the case of the syngases, Study 1 demonstrated higher indicated efficiency, electrical efficiency, and electrical power than Study 2. After the use of the three‐way catalytic converter, HC and CO emissions were strongly reduced for all fuels and in different operational conditions. On the other hand, because the efficiency of the catalytic converter decreases abruptly in mixtures rich in NOx, this pollutant was not removed when λ > 1. The comparison of the two studies and the emissions after the use of a catalytic converter is important as it shows specific ways to improve the use and efficiency of the fuels to encourage the development of renewable energy both in industry and in the transport sector. © 2019 Society of Chemical Industry and John Wiley & Sons, Ltd [ABSTRACT FROM AUTHOR]

Internal combustion engines are one of the major contributors of air pollution. Exhaust gas from these engines contains HC, CO, NOx, PM and smoke which are the harmful pollutants to humans as well as to the environment. The stringent norms enforced by governments has necessitated in improving the after-treatment processes of these exhaust gas. A three-way catalytic converter is one of the most effective devices in treating the HC, CO and NOx pollutants into nontoxic gases. In this paper, numerical investigation is carried out by using commercial CFD code, ANSYS Fluent to analyse the effect of cone length on the conversion efficiency of the Catalytic Converter (CC). Pressure drop, back pressure and temperature are the parameters which are monitored in this study. The cone length of the CC is varied from 70mm to 90mm in steps of 10mm. All the CCs are analysed for identical test conditions. It is observed that temperature and pressure showed an appreciable decrease with increase in cone length to 90mm. On the other hand, velocity increases with increase in cone length to 90mm. A lower pressure drop and temperature is observed for the CC with cone length of 90mm. As conversion efficiency of the CC is dependent on the lower pressure drop, lesser back pressure and lower temperature, the CC with cone length of 90mm is found to be the apt choice. [ABSTRACT FROM AUTHOR]

Abstract In a typical practical monolith reactor implementation, turbulent flow in a large pipe or inlet header enters small monolith channels. After some distance the flow becomes fully developed laminar flow. It has been shown that the distance over which the turbulence transitions to laminar flow is significant. This paper reports results of investigation into the value of the Nusselt number in the entry region of a circular tube under conditions of decaying turbulence. Large Eddy Simulations (LES) are used to model the flow. LES simulations show that the Nusselt number is significantly larger in the entry region compared to the classical case of developing laminar flow. The entry length Nu number depends not only on the inverse Graetz number, but also independently on the Reynolds number, turbulence length scale and upstream turbulence intensity. A general correlation is developed that relates the Nu number in the entry region to the inverse Graetz number, Reynolds number, inlet turbulence intensity and turbulence length scale. Highlights • Entry length Nusselt numbers for a monolith channel are analyzed with decaying turbulence. • Nusselt numbers are higher than for developing laminar flow. • Nusselt number depends on Reynolds number and turbulence levels. • A general correlation for developing flow Nusselt numbers is developed. [ABSTRACT FROM AUTHOR]

Exhaust emissions emitted from spark ignition engines cause air pollution, human health hazards and ecological imbalance. Hence, effective curtail of these is an essential task. For this, an experimental evaluation was carried out on emissions and performance characteristics of the four-stroke threecylinder Maruthi engine at varied brake power. Three different techniques, initially the exhaust gas recirculation (EGR) system was coupled to the test engine and varied from 0 to 10% for estimation of optimal value. Secondly, the provision of the catalytic converter with the copper as a catalyst and finally by the air injection mechanism of 60 l/m into the catalytic converter is executed and evaluated for optimum emission reduction. Also, the combined effect of these techniques on the characteristics was analysed. From the results, it was found that up to an EGR rate of 5%, an enhancement of 2% in brake thermal efficiency and a reduction of 9.5% in brake specific fuel consumption, 21% in carbon monoxide (CO), 19% in un-burnt hydrocarbon (UHC) and 29% in NOx emissions and a further increase in the EGR rate causes performance deterioration. The NOx emissions decreased by 44% at 7% of EGR. The catalytic converter setup alone decreased CO and UHC by 40% and by application of air injection it was 60%. The CO& UHC emissions decreased by 54% &52% respectively at 7% EGR rate combined with the catalytic converter and air injection mechanism. [ABSTRACT FROM AUTHOR]

Abstract State-of-the-art catalytic converters need an ever-high amount of precious-metal catalysts to meet stringent emission regulations. This research reveals an alternative design based on micro-structured ceramic hollow fibre substrates, yielding high conversion of pollutants at low catalyst costs, as well as a unique benefit of low pressure-drop, leading to high engine performances. Graphical abstract Unlabelled Image Highlights • A new micro-structured ceramic hollow fibre substrate for emissions control • High geometric surface areas and low pressure drop are achieved at the same time. • Catalytic wash-coating is inside the unique radial micro-channels of substrates. • Light-off temperatures of CO oxidation are comparable to commercial counterparts. [ABSTRACT FROM AUTHOR]

Highlights • A TES system was integrated into the diesel aftertreatment. • With TES reduction in emissions was seen, particularly during engine cold-start. • The TES system maintained the DOC temperature above 150 °C for more than 12 h. • Graphite based PCM and metallic substrate increased system's thermal conductivity. Abstract To reduce cold-start emissions, a thermal energy storage (TES) system can be used in conjunction with the exhaust aftertreatment system. Phase change materials (PCM) can be used in the TES system to absorb the exhaust gas thermal energy, thus liquefying and storing it as latent heat. This allows storage of the exhaust gas thermal energy during the engine's high-load conditions and gradually releases the thermal energy back to the catalyst substrate during the engine-off period. Based on the results, implementing a TES system into the diesel aftertreatment system has shown great potential in reducing a vehicle's emissions, particularly for hybrid vehicles. This approach can assist the catalyst to activate the emissions' conversion reactions straight after the cold-start. However, its effectiveness largely depends on the duration of the engine-off periods between the driving cycles. In this study, it was found that facilitating the heat transfer between the PCM and the catalyst can significantly improve the emissions' reduction performance by avoiding the catalyst to light-out after the cold-start. A substantial improvement in the system's thermal behaviour was observed by using PCM additives and metallic catalyst substrates to increase the system's thermal conductivity. Although a TES system increases the aftertreatment cost and complexity, it can result in substantial emissions' reduction over the vehicle's operating life. This can also translate into reduced vehicle fuel consumption and CO 2 emissions, as the emissions-related fuel penalty will be minimized. [ABSTRACT FROM AUTHOR]

N2O emission from automobile has been regulated by the United States Environment Protection Agency due to its higher global warming potential compared to CO2. Responding to this, an instrument for fast sensing of ultra-low concentration of N2O from automobile has become an urgent need. In this study, an instrument based on the quantum cascade laser spectroscopy has been developed and applied for certification testing of ultra-low N2O in automobile exhaust. The pulsed quantum cascade laser can emit coherent lights in the mid-infrared region where N2O shows strong absorption and better control of wavelength. Therefore, a very low detection limit can be achieved and interference of co-existing gases can be avoided using a super fine resolution of the mid-infrared spectrum. The US Code of Federal Regulations Parts 1065/1066 allows measuring N2O from sample storage bags, from a continuous dilute stream or a raw exhaust stream. Typically, batch (bag) sampling has better accuracy and repeatability, but continuous sampling is more efficient in terms of test cell running time and provides test-mode emissions. In this study, the quantum cascade laser analyzer has been applied to investigate correlations between bag sampling and continuous dilute exhaust sampling using a fleet of vehicles with a wide range of N2O emission levels all meeting United States Environment Protection Agency emission standards. Very good correlation between these two sampling methods was observed for the majority of tests conducted and in best case the difference was less than ±1%. The direct injection gasoline vehicle emits higher N2O than conventional port injection gasoline vehicles. The quantum cascade laser analyzer has been successfully applied for United States Environment Protection Agency N2O certification test. [ABSTRACT FROM AUTHOR]

Abstract To mitigate the concentrations of air pollutants in the atmosphere, an intervention program of replacing the converters of liquefied petroleum gas (LPG) fueled vehicles was implemented by the Hong Kong government between October 2013 and April 2014. Data of ambient volatile organic compounds (VOCs) and other trace gases continuously monitored from September 2012 to April 2017 at a roadside site were used to evaluate the continuous effectiveness of the replaced catalytic converters on the reduction of air pollutants. The measurement data showed that LPG-related VOCs (propane and n / i -butanes) and several trace gases (CO, NO and NO 2) decreased significantly from before to after the program (p < 0.01). To further assess the efficiency of the program, five periods covering before the program, during the program, 1st year after the program, 2nd year after the program and 3rd year after the program were categorized. The values of propane and n / i -butanes decreased from Period-1 (before the program) to Period-2 (during the program), and from Period-2 to Periods 3–5 (after the program) (p < 0.01). In addition, the reduction rates of propane and n / i -butanes remained high and constant in Periods 3–5, suggesting that either had the vehicle owners themselves routinely replaced the converters at suitable interval afterwards, or were their vehicles caught by a remote sensing program checking excessive emissions. Source apportionment analysis indicated that LPG-fueled vehicular emissions were the top contributor to ambient VOCs in the roadside environment while the VOCs emitted from LPG-fueled vehicles indeed decreased at a rate of 4.21 ± 2.38 ppbv/year (average ± 95% confidence interval) from Period-1 to Period-5 (p < 0.01). Furthermore, the photochemical box model simulations revealed that the net negative contribution of VOCs and NO x emitted from LPG-fueled vehicles to O 3 production strengthened at a rate of 1.9 × 10−2 pptv/day from Period-1 to Period-5 (p < 0.01). The findings proved the continuous effectiveness of the intervention program, and are of help to future control strategies in Hong Kong. Graphical abstract Unlabelled Image Highlights • VOCs emitted from LPG-fueled vehicles decreased • Net negative contribution of VOCs and NO x from LPG vehicles to O 3 increased • The intervention program has been continuously effective. [ABSTRACT FROM AUTHOR]

Recently, a few researchers studied a coupled system of first order partial differential equation arising from a catalytic converter and interesting existence and uniqueness results have been proved. Later, the same system has been solved using finite difference method after linearizing it using a monotone iterative scheme. Even though all the iterative schemes considered were proved to have linear convergence, numerical examples suggest that certain iterative scheme converges faster than the others. The theoretical justification for the above behavior is missing in these works. This short note intents to bridge this gap by providing a mathematical justification for the faster convergence. [ABSTRACT FROM AUTHOR]

Automotive industry is one of the largest industries all over the world. There are worldwide companies and individual local automotive companies. There are restricted regulations and standards related to automotive industry including emissions. Reduction of emissions is a very important problem. Alternative solutions are offered to reduce the emissions. In this study, reduction of the emissions is numerically investigated for different channel geometry, inlet temperature, and wall temperature of the catalytic converter channel. It was found that increasing the wall temperature activates the catalytic converter and produces more reduced emissions. The channel geometry has little effect on the conversion efficiency of the catalytic converter due to the same hydraulic diameters of the channels. In conclusion, the cold-start engine condition preheating could be applied to the exhaust gas for more environmentally friendly operation. [ABSTRACT FROM AUTHOR]

Highlights • A new generation of catalytic converters is presented. • Experimental and numerical investigations are carried out. • The thermal and fluid flow characteristics is evaluated. • Improvement in the thermal performance by 18% is achieved. • The uniformity index is improved by 5% Abstract The need for improved fuel economy, while meeting more stringent global vehicle emission standards, continues to grow with the increasing demand for environmental protection and rising fuel prices. A new generation of catalytic converters, designed and patented by Vida Fresh Air Corp., offers emissions reduction while improving fuel economy. In this design, a thin layer of insulating material is placed inside the ceramic honeycomb channels, creating a multi-chamber catalytic converter. The improvement in performance of the catalytic converter is attributed to the change in both the flow distribution and the controlled heat diffusion from the inner to the outer chambers. On engine performance tests have shown significant improvements in both fuel economy and emissions, however, the theory of operation of this design needs to be validated for potential design improvements to achieve an optimum performance. In this study both experimental and numerical investigations are carried out in order to understand the flow through the catalytic converter, using different monolith cell densities. A dynamically scaled-down model for a typical flow through catalytic converter was utilized for this study. Detailed experiments were conducted using hot air as the working fluid in order to evaluate the thermal and fluid flow characteristics of the new catalytic converter technology without the effect of chemical reactions. The measurements were performed at a Reynolds number of 43,000 with a free stream temperature of 177 °C. These conditions were selected in order to achieve thermal and hydraulic similarity to actual flow conditions for a typical catalytic converter. Numerical modelling of the flow through the setup under investigation was found to adequately replicate the experimental measurements for temperature, velocity and turbulence intensity within ±3%, ±5% and ±8% respectively. The use of a new design of the catalytic converter found to improve the thermal performance by 18% and the hydraulic performance by 5% without a significant increase of the pressure drop across the catalytic converter. [ABSTRACT FROM AUTHOR]

Highlights • New approach to predict turbulent flows inside of a catalytic converter. • Decay and ignition of turbulence at the entrance and exit zone of the monolith. • Model simplicity in terms of implementation in any commercial or open-source CFD software. Abstract This work presents a new approach to predict turbulent flows inside of a catalytic converter taking into account a decay and ignition of turbulence at the entrance and exit zone of the monolith, respectively. The core part of the converter is a monolith substrate, which is commonly represented as a homogeneous porous medium due to computational limitations. Such simplification eliminates any interaction with the solid when the flow is entering and leaving the substrate. This work extends the previously addressed decay of the turbulence entering the monolith, with the turbulence generation exiting it. This is achieved using an immersed boundary condition immediately after the porous medium, whose values are estimated using a local Reynolds, based on observations made in a discrete channel geometry. The results are compared with commonly used converter models, finding substantial differences in the effective viscosity and kinetic energy inside and after the monolith. The proposed model agrees with the one obtained in discrete geometry, and it also prevents unrealistic changes in the flow observed in existing models. The distinguishing feature of the proposed model is its simplicity in terms of implementation in any commercial or open-source CFD software. Model performance using models based on Reynolds-averaged Navier–Stokes equations (RANS) and Large eddy simulations (LES) of the whole automotive converter is illustrated. [ABSTRACT FROM AUTHOR]

This study investigates geometric parameters of commercially available or recently published models of catalyst substrates for passenger vehicles and provides a numerical evaluation of their influence on heat-up behavior. Parameters considered to have a significant impact on the thermal economy of a monolith are: internal surface area, heat transfer coefficient, and mass of the converter, as well as its heat capacity. During simulation experiments, it could be determined that the primary role is played by the mass of the monolith and its internal surface area, while the heat transfer coefficient only has a secondary role. Furthermore, an optimization loop was implemented, whereby the internal surface area of a commonly used substrate was chosen as a reference. The lengths of the thin wall and high cell density monoliths investigated were adapted consecutively to obtain the reference internal surface area. The results obtained by this optimization process contribute to improving the heat-up performance while simultaneously reducing the valuable installation space required.

According to the strict European exhaust emissions standards that have been imposed by European legislation there is an elevated need for the decrease of the toxic gas emissions from vehicles. Therefore, car manufacturers have implemented a series of catalytic devices in the aftertreatment of the engine to comply with the standards. All catalytic devices (such as three-way catalysts, diesel particulate filters and diesel oxidation catalysts) accumulate concentrated loading of platinum group metals (PGMs, platinum, palladium, rhodium) as the active catalytic phase. Thus, the demand for PGMs is constantly increasing with a subsequent increase in their market prices. As a result, the research on catalytic converters of high activity and reduced cost/PGM loading is of great interest. In the present work, the Prometheus catalyst, a polymetallic nanosized copper-based catalyst for automotive emission control applications, is presented in two different metal loadings (2 wt% and 5 wt%) and metal ratios (Cu/Pd/Rh = 21/7/1 and Cu/Pd/Rh = 21/7/3). For the first time, a three-metal (copper, palladium, rhodium) nano-catalyst has been synthesized and characterized on a large scale. By using copper as an active catalytic phase, a reduction of PGMs loading is achieved (up to 85%) resulting in a novel catalytic device with similar or improved catalytic performance compared to commercial ones. The Prometheus catalyst is prepared by a wet impregnation method, using as a carrier an inorganic mixed oxide (CeZrO4) exhibiting elevated oxygen storage capacity (OSC). The heterogeneous catalytic powders produced were characterized by both spectroscopic and analytical methods. The metal content and ratio were determined by inductively coupled plasma mass spectrometry (ICP-MS), X-ray fluorescence (XRF) and energy-dispersive X-ray spectroscopy (EDS). The morphology and the catalyst particle size were determined with scanning electron microscopy (SEM) and X-ray diffraction (XRD). The investigation revealed homogeneous particle formation and dispersion. The deposition of the metal nanoparticles on the porous inorganic carrier was verified with N2 sorption. Catalytic performance and reactivity of a catalyst (pure wash coat) with molar ratio 21/7/1 and a full-scale Prometheus catalyst with the desired loading of 15 g/ft3 were tested on an in-house synthetic gas bench (SGB) for the abatement of CO, CH4 and NO, both presenting high catalytic activity.

In automobile-exhaust systems, catalytic converters are the main components to produce substantial pressure drops, which induce engine-power loss and fuel-consumption rise. In addition to the need to reduce the pressure loss, the flow passing through the catalytic substrate should be as uniform as possible, which provides a uniform thermal distribution and high catalytic-conversion efficiency. The authors have reported that a flow deflector placed inside a catalytic-converter diffuser part can drastically reduce the pressure loss and improve the velocity-profile uniformity in comparison with the no-flow-deflector case (Hirata et al., 2006 & 2008). In those reports, the authors' concern is restricted only to steady flow, due to the authors' intention to reveal fundamental features precisely under a simple and general condition. On the other hand, actual exhaust flows often include various pulsative components. So, the authors investigate the effects of flow pulsation upon the flow-deflector performances such as the pressure-loss reduction and the flow-uniformity improvement. As a result, the authors reveal that the flow deflector can reduce the pressure loss and improve the velocity-profile uniformity in comparison with the no-flow-deflector case, even for pulsating flow as well as steady flow.