Commercial Converters Research Articles

Exploration of Zeolite 5A as a catalyst in the after-treatment system of a CI engine powered by plastic oil blend

Catalytic converters are commonly used for automotive engines to reduce regulatory emissions. Catalysts used in commercial converters are expensive and they work in particular temperature ranges. To overcome those problems, Zeolite 5A powder is chosen and used as a catalytic material in the catalytic converter to reduce the emissions from the Compression Ignition (CI engine). Zeolite 5A was molded into solid by adding distilled water and carboxymethyl cellulose as binder material. The prepared solid mold was used as catalytic material in the exhaust gas after-treatment system. The waste plastics were pyrolyzed into oil and blended equivalently with diesel (50:50 ratios) for this investigation. The performance and emission readings were taken by varying the engine loads (0, 1.32, 2.6, 3.9 and 5.2 kW) in the single-cylinder 5.2 kW CI engine. The NO and HC emission were reduced by 37% and 33% respectively at the full load condition.

Equivalent Phase Current Harmonic Elimination in Quadruple Three-Phase Drives Based on Carrier Phase Shift Method

Multiphase drives are entering the spotlight of the research community for transportation applications with their high power density and the possibility of high fault tolerance. The multi three-phase drive is one of the main types of multiphase drives that allows for the direct adoption of commercial three-phase converters and high control flexibility. The elimination of high-frequency current harmonics will reduce the flux linkage harmonics, torque ripple, vibration and noise in machine drives. Therefore, this work introduces a new method to the modelling of equivalent phase current in multi three-phase drives with the double integral Fourier analysis method. A new carrier-based pulse-width modulation (CPWM) method is introduced to reduce the equivalent phase current harmonics by applying proper carrier phase angle to each subsystem in the multi three-phase drives. The proposed angles of carrier signals are analyzed for quadruple three-phase drives, and the corresponding experimental results confirm the significance of the proposed phase-shifted CPWM method to eliminate the equivalent phase current harmonics.

A Review of Steel Scrap Melting in Molten Iron‐Carbon Melts

In the current economic climate, the recycling of steel scrap is become one of the most interesting tasks for the optimization of integrated steel plants. Steelmaking aspects such as jet/bath interaction, slag formation or foaming, lime dissolution as well as slag/metal reactions have received more attention in recent years than the melting and dissolution phenomena of steel scrap in molten steel baths. Since the dynamic modeling of steelmaking processes ‐ especially the Linz Donawitz oxygen steelmaking process (LD) ‐ is becoming more important, interest in the melting and dissolution behaviour is increasing. Several researchers have investigated the complex transactions of coupled heat and mass transfer in the past. Small‐scale experiments are carried out under conditions where only mass transfer or heat transfer were considered. A few authors have reported on pilot‐scale investigations or commercial converters. The coupled heat and mass transfer has also been analyzed by several authors in mathematical models and numerical simulations. The present paper reviews the research on steel scrap melting and dissolution done in the last 50 years. A summary of all reported heat and mass transfer coefficients will be given and the differences between natural and forced convection will be explained. In addition, an overview of recently published numerical simulation describing the problem will give an outlook for future work.

Blackbox Large-Signal Modeling of Grid-Connected DC-AC Electronic Power Converters

Modern electric power distribution systems are progressively integrating electronic power converters. However, the design of electronic-power-converter-based systems is not a straightforward task, as the interactions among the different converters can lead to dynamic degradation or instabilities. In addition, electric power distribution systems are expected to consist of commercial-off-the-shelf converters, which implies limited information about the dynamic behavior of the devices. Large-signal blackbox modeling approaches have been proposed in order to obtain accurate dynamic models of commercial converters that can be used for system-level analyses. However, most of the works are focused on DC-DC converters. In this work, a large-signal blackbox model is proposed to model grid-connected three-phase DC-AC converters. An experimental setup has been used to demonstrate the limitations of small-signal models and the capability of the proposed modeling approach to capture the dynamic behavior of the converter when large perturbations are applied. Finally, the automation of the model identification process is discussed.

DFIG stator flux‐oriented control scheme execution for test facilities utilising commercial converters

The utilisation of conventional industrial converters for development of doubly-fed induction generator (DFIG) test facilities poses an attractive prospect as it would provide proprietary commercial protection and functionality. However, standard commercial converters present significant challenges in attainable DFIG operational capability. This is due to the fact that they are designed for execution of a limited set of pre-programmed common control modes. They typically do not cater for execution of complicated stator flux-oriented vector control (SFOC) schemes required for DFIG drive control. The research work presented in this study reports a methodology that enables effective implementation of SFOC on industrial converters through a dedicated external real-time platform and a velocity/position communication module. The reported scheme is validated in laboratory experiments on an experimental DFIG test-rig facility. The presented principles are general and are therefore applicable to conventional DFIG drive architectures utilising standard industrial converters.

Non-Linear Behavioral Modeling for DC-DC Converters and Dynamic Analysis of Distributed Energy Systems

In modern distributed energy systems (DES), focus is shifting from the conventional centralized approach towards distributed architectures. However, modeling and analysis of these systems is more complex, as it involves the interface of multiple energy sources with many different type of loads through power electronics converters. The integration of power electronics converters allows distributed renewable energy sources to become part of modern electronics power distribution systems (EPDS). It will also facilitate the ongoing research towards DC-based DES which is mostly composed of commercial DC-DC converters whose internal structure and parameters are unknown. For the system level analysis, the behavioral modeling technique is the only choice. Since most power electronics converters are non-linear systems and linear models can’t model their dynamics to a desired level of accuracy, hence non-linear modeling is required for accurate modeling. The non-linear modeling approach presented here aims to develop behavioral models that can predict the response of the system over the entire operating range. In this work, either a lookup table or a polytopic structure-based modeling technique is used. The technique is further applied to cascade and parallel connected converters, being two DES scenarios. First the procedure is verified via application to switching models in a simulation and then validated for commercial converters via experiments. The results show that the developed behavioral models accurately predict both the transient and steady state response.

Multitrack Power Conversion Architecture

This paper introduces a MultiTrack power conversion architecture that represents a new way of combining switched capacitor circuits and magnetics. The MultiTrack architecture takes advantages of the distributed power processing concept and a hybrid switched-capacitor/magnetics circuit structure. It reduces the voltage ratings on devices, reduces the voltage regulation stress of the system, improves the component utilization, and reduces the sizes of passive components. This architecture is suitable to dc- dc and grid-interface applications that require both isolation and wide voltage conversion range. An 18-80 V input, 5 V, 15 A output, 800 kHz, 0.93 in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> (1/16 brick equivalent) isolated dc-dc converter has been built and tested to verify the effectiveness of this architecture. By employing the MultiTrack architecture, utilizing GaN switches, and operating at higher frequencies, the prototype converter achieves a power density of 457.3 W/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> and a peak efficiency of 91.3%. Its power density is 3× higher than the state-of-the-art commercial converters with comparable efficiency across the wide operation range.

The Effect of Different SO2/SO3 Catalytic Media on High-Temperature Corrosion Processes (Hot Corrosion, Fireside Corrosion, Sulfidation–Oxidation)

In many laboratory hot corrosion (HC) experiments and other experiments involving sulfur commercial catalytic converters are used to catalyze the $${\text{SO}}_{ 2} + { 1}/ 2 {\text{O}}_{ 2} \to {\text{SO}}_{ 3}$$ reaction. The conversion rate of SO2 to SO3 highly depends on the catalyst used and thus the HC results, especially in low-temperature HC conditions, may vary significantly depending on the catalyst selected. Different elements present in the catalyst affect the SO2 to SO3 conversion and with it the degree of HC induced attack. Modern automotive catalysts have low activity for the oxidation of SO2 to SO3. The conversion of SO2 to SO3 can be enhanced by modifications of the catalyst, e.g. by using a Pt-gauze or dip-coating the catalyst in a Fe2O3 solution.

Adaptive Voltage Control of the DC/DC Boost Stage in PV Converters With Small Input Capacitor

In the case of photovoltaic (PV) systems, an adequate PV voltage regulation is fundamental in order to both maximize and limit the power. For this purpose, a large input capacitor has traditionally been used. However, when reducing that capacitor's size, the nonlinearities of the PV array make the performance of the voltage regulation become highly dependent on the operating point. This paper analyzes the nonlinear characteristics of the PV generator and clearly states their effect on the control of the dc/dc boost stage of commercial converters by means of a linearization around the operating point. Then, it proposes an adaptive control, which enables the use of a small input capacitor preserving at the same time the performance of the original system with a large capacitor. Experimental results are carried out for a commercial converter with a 40 μF input capacitor, and a 4 kW PV array. The results corroborate the theoretical analysis; they evidence the problems of the traditional control, and validate the proposed control with such a small capacitor.

Commercial Buck Converters and Custom Coil Development for the Atlas Inner Detector Upgrade

A new generation of higher gain commercial buck converters built using advanced short channel CMOS processes has the potential to operate in the Atlas Inner Detector at the Super Large Hadron Collider (sLHC). This approach would inherently be more efficient than the existing practice of locating the power conversion external to the detector. The converters must operate in a large magnetic field and be able to survive both high doses of ionizing radiation and large neutron fluences. The presence of a large magnetic field necessitates the use of an air core inductor which is developed and discussed here. Noise measurements will be made to investigate the effect of the high frequency switching of the buck converter on the sensitive front end electronics. Radiation hardness of selected buck converters and mosfets will also be reported.

Simple Modeling and Identification Procedures for “Black-Box” Behavioral Modeling of Power Converters Based on Transient Response Analysis

Today, black-box behavioral models of power converters are becoming interesting for system level simulation of power electronics systems. These models can be used to evaluate the response of systems that are composed of commercial converters, since they can be fully parameterized by analyzing the actual converter response. To optimize the required computational resources, these models should be as simple as possible. Furthermore, the identification of the parameters should be carried out easily, looking for simple experiments and straightforward adjusting algorithms. Easy modeling and identification procedures, based on a transient response analysis, are proposed in this paper. Using this method, a large-signal black-box behavioral model of a power converter is composed of reduced-order transfer functions, which are identified by analyzing the step response of the converter. Both an actual commercial dc-dc converter and a line-commutated rectifier have been modeled and identified by means of this approach, in order to validate the proposed procedures.

Enhancement of 3-Way CNG Catalyst Performance at High Temperature Due to the Presence of Water in the Feed: On the Role of Steam Reforming of Methane and on the Influence of Ageing

The reaction mechanism of typical 3-way catalysts (TWC) has been already deeply studied. However, fewer efforts have been made to understand TWC compressed natural gas applications. Thus, the role of water in reducing atmospheres is still not well understood. In the present paper we show the positive impact of water on pollutants abatement at high temperature on commercial converters.

Parametric algorithms for frequency estimation in PWM converter systems

Proper estimation of voltage parameters has a significant meaning for power converters control systems. One of the measured parameter, directly associated with control process, is frequency of the basic voltage component at the converter output. Unfortunately, power converters generate a wide spectrum of harmonics as well as interharmonics, that makes difficulties in estimation this frequency. Measurement carried out in industrial applications exhibits complex nature of investigated signals often corrupted by resonances or overvoltages phenomena. It entails searching a new digital algorithms for frequency measurement. This work presents algorithm using modification of high-resolution Prony method connected with digital filtering. The investigations was based on simulations and real measured signals recorded in two different commercial PWM converters. Obtained results indicate accuracy of the method as well as its fast response.

A Unified Approach for Modeling Three-Way Catalytic Converters and NOx Traps with a Minimum Set of Tunable Parameters

The demanding legislation for vehicle emissions pushes the automotive industry to the commercialization of advanced exhaust systems. The careful design of each aftertreatment device fitted in exhaust line and the interactions with the engine management, makes modelling an important part of systems engineering for these applications. Almost all catalytic converter models that are found in the literature use tunable parameters which typically address the kinetic terms of chemical reactions. A great effort has been given to the definition of complex reaction schemes and mechanistic description of them in-vitro, in order to assist the advanced design of catalytic washcoats and explain their complex chemistry. This paper presents a systematic effort towards the modelling of advanced commercial exhaust treatment systems, using a unified approach for the different devices. The model used in this work describes the catalytic processes with global reactions, using apparent Arrhenius type rate expressions with L-H kinetics. The model is used to predict transient performance of commercial catalytic converters under legislated test conditions. During these tests the existing uncertainties and intrinsic variations of engine and catalyst operation make the robustness and flexibility of the model prominent targets. Comparison of computed and measured second-by-second emissions demonstrate a high level of modelling accuracy, adequate to fit the behavior of advanced commercial applications of three-way catalytic converters and NOx traps, using a minimum set of 3 tunable parameters for each device.

Performance Study of 48 Road-Aged Commercial Three Way Catalytic Converters

48 commercial three-way catalytic converters (TWC) aged on-road were investigated. The results show that there was no significant impact of aging on light off temperatures for CO, HC, and NO up to 120 000 km. Above 120 000 km, the light off temperatures in general increased. The steady state conversions for CO and HC are not significantly affected by aging. However, the steady state conversion of NO is decreased with increased mileage at the conditions studied. The impact of aging on oxygen storage capacity (OSC) of the converters was studied by propene pulse experiments. A trend of decreased pulse conversion was noted above 120 000 km. OSC and NO-conversion showed considerable difference between individuals with similar mileage. A number of high-mileage units perform well while a few low-mileage converters appear to be next to destroyed. The surface characterization shows that the main cause of deactivation was loss of specific surface, both of washcoat and precious metals. This is most likely due to exposure to high temperatures. Poisoning elements, typically phosphorus, lead, sulphur and calcium, are found on the catalysts surface.

Characterisation of Three-Way Automotive Aftertreatment Catalysts and Related Model Systems

The techniques applied to the characterisation of three-way automotive aftertreatment catalysts, and some of the most relevant results obtained from those, are briefly overviewed. Studies dealing with both, commercial converters and NM/CeO2 (CeO2-ZrO2) model systems are considered. The analytical and structural characterisation studies on commercial TWCs reported here are mainly devoted to the identification of some of the most relevant factors causing their deactivation. Regarding the reviewed literature on model systems, some more fundamental aspects are considered. Among them, the use of HRTEM, spectroscopic, and chemical techniques in studies on metal sintering and re-dispersion, metal/support interaction phenomena, and redox characterisation of ceria-based catalytic materials are discussed.

Measurement of NOY during the SCOS97-NARSTO

Abstract Dual converter NOY analyzers configured to also measure nitric acid were evaluated under laboratory conditions, smog chamber simulations, and during ambient monitoring. Commercial molybdenum metal converters in the NOY configuration were found to be capable of converting all major NOY species to NO under laboratory testing conditions. Some converters required higher-temperature set points than received from the manufacturer and several converters did not achieve 95% efficiency at the highest temperature allowed by the manufacturer (380°C). They also exhibited varying degrees of efficiency for oxidizing ammonia to NO depending on previous usage, but not operating temperature. After the field measurement program, the efficiency for converting nitric acid was found to be variable during smog chamber measurements. This was ascribed to degradation of the converter under field measurement conditions. The ambient measurement program showed a significant memory effect that contributed to a positive NOY measurement bias. The magnitude of this memory effect appeared to be related to the degree of ambient concentrations of pollutants being sampled. Ambient nitric acid measurements determined from the dual converter approach were related to those from a tunable diode laser absorption spectrometer although the correlation was not high. The variable converter efficiency for ammonia may lead to negative biases when measuring nitric acid.

銅製錬転炉反応解析への平衡計算の応用

Changes of the matte grade and oxygen pressure during the slag making stage in a PS copper converter were calculated by equilibrium calculations. In the calculation a slag making stage was simulated by many calculation steps in series, each of the steps being assumed in an equilibrium state. Results of the calculation were compared with experimental values measured in pilot and commercial converters.1. Calculated and measured matte grade changes were in good agreement with each other during the slag making stage. In particular, both of the changes showed that in the beginning of the stage there was a period of time for which the matte grade did not increase appreciably in spite of blowing. According to the present calculation, this was attributed to an increase of oxygen disolved in the matte.2. Calculated oxygen pressures at the beginning and the end of the stage agreed relatively well with those measured for the matte before blowing and for the converter slag after the stage, respectively. However oxygen pressures measured through the converter mouth during the stage were rather higher than those predicted by the calculation. Some of the measurements gave higher oxygen pressures than those measured even at the end of the stage.3. To explain the above mentioned phenomena by equilibrium calculation, a two-zone converter model has been developed. In the model the matte holding zone in a converter consists of two zones, i. e. a magnetite formation zone and a magnetite reduction zone, which are assumed in a different equilibrium state. By setting a proper ratio of the two zones, differences in oxygen pressure between the white metal and the converter slag at the end of the slag making stage were explained to some extent.

Mössbauer study of some rust converters

The ability “to transform rust” of nine commercial converters has been studied by Mossbauer spectroscopy. This technique fails to prove that all nine but one change the chemical nature of the rust previously formed on mild steel plates. Accelerated salt spray tests demonstrated a significant different performance for the studied products, whose effects range from deleterious to beneficial.

浴内反応および混合攪拌状態を考慮した数学モデルによる脱炭反応の検討*

A mathematical model taking the flow and reactions in bath into consideration has been developed in order to investigate the decarburization process quantitatively. This model is able to simulate well the variation of process variables.The knowledges obtained from process analysis in this study are as follows: (i) the low value of oxygen efficiency for decarburization is due to the low value of absorption efficiency of oxygen, namely 50-60%, which is further caused by the relatively large resistance of mass transfer in gas phase; (ii) the fire spot occupies the area corresponding to the width of gas jet; (iii) the variation of exhaust gas composition is primarily determined by the division of unabsorbed oxygen between the combustion of CO gas and the oxidation of scattered droplets of liquid iron.Finally, the self-acceleration of decarburization in commercial converters has been pointed out.