575 research outputs found
SCR-filter model order reduction (2): proper orthogonal decomposition and artificial neural network
No full text© 2020, The Author(s). Catalysed diesel particulate filters (DPF) have been described as multifunctional reactor systems. Integration of selective catalytic reduction (SCR) functionality in the DPF creates an SCR-in-DPF system that achieves nitrous oxides (NOx) treatment along with particulate matter (PM) collection. The physical and chemical aspects of the integrated SCR-filter complicate system modelling. The goal of this work is to develop low-complexity model of the SCR-filter system which retains high fidelity. A high-fidelity model of the SCR-coated filter has been developed and validated. The performance of the model was described in a previous paper. Model complexity reduction is attempted in this paper. The objective is to achieve simulation times that can support the deployment of the model for online system control in an engine control unit. Two approaches were taken for the SCR-coated filter model order reduction (MOR): a “grey-box” approach via proper orthogonal decomposition (POD) and a “black box” approach via artificial neural network (ANN) function approximation. The POD method is shown to deliver a significant MOR while maintaining a high degree of fidelity but with less than 5% improvement in simulation time. The ANN method delivers a substantial MOR with reduction of three orders of magnitude in simulation time. The accuracy of the ANN model is satisfactory with good generalisation to new test data but noticeably inferior to the POD method
Beyond SCR in Weak Grids: Analytical Evaluation of Voltage Stability and Excess System Strength
No full textDue to the continuous increase (decrease) in the number of inverter-based (synchronous) generators in modern electrical power systems, the theoretical foundations behind widely used system strength and voltage stability assessment methods require thorough revision. The existing evaluation methods such as the Short-Circuit Ratio (SCR) are often based on simplifications which may produce inaccuracies, particularly when studying weak systems. As a result, a misleading estimation of voltage stability can occur, exposing systems to unnecessary renewables curtailment or other inappropriate remedial actions that may cause partial disruptions or potential instability. This paper provides a rigorous analytical revision of voltage stability assessment to confidently evaluate the maximum power transfer under various operating conditions. Subsequently, the proposed approach is applied as an enhanced method of system strength evaluation. The method is extensively tested on a single-machine-infinite-bus test system. Numerical results show a notably more accurate assessment relative to the common alternative methods.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Intelligent Electrical Power Grid
Segmented SCR for High Voltage ESD Protection
No full textTypical SCR with stripe layout style is modified into segmented one in order to tune the SCR's holding voltage for the ESD protection in different operation voltage domain SCRs with different segmented style and ratio were made, and according to TLP test results, the most proper one for high voltage ESD protection is selected among them. By delicate layout design and choosing the right segmentation pattern and ratio, the holding voltage of the SCR is obviously lifted to a high level of over 30 V, a high enough value to obtain latch-up immunityEngineering, Electrical & ElectronicPhysics, AppliedEICPCI-S(ISTP)
Voluntary Simplicity – A Path to Sustainable Prosperity
No full textVoluntary simplicity is not about living in poverty; it is about living with balance. This contribution illuminates the pattern of changes that an increasing number of people around the world are making their everyday lives as an active response to the challenges of our times. By embracing a lifeway of simplicity - characterized by a compassionate and ecological consciousness, frugal consumption, and inner development - people can change their lives and, in the process, move the world toward sustainable prosperity
LDMOS-SCR: a replacement for LDMOS with high ESD self-protection ability for HV application
No full textA study of LDMOS-SCR devices for SOI BCD technology is presented. The LDMOS-SCR is fully compatible with BCD process and can replace the LDMOS as a high voltage output driver. By comparison of the LDMOS and another 'pnpn' type of LDMOS-SCR, the triggering mechanism and ESD behavior are well discussed with both device simulation and TLP measurement. It is verified that the ESD performance of the LDMOS-SCR is much improved compared with the LDMOS.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000300624000008&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Engineering, Electrical & ElectronicMaterials Science, MultidisciplinaryPhysics, Condensed MatterSCI(E)EI2ARTICLE3null2
In situ/operando spectroscopic studies on NH3-SCR reactions catalyzed by a phosphorus-modified Cu-CHA zeolite
No full textThe modification of Cu-exchanged zeolites with phosphorus represents a promising method to enhance their hydrothermal stability, which is of pivotal importance for catalysts that promote the selective catalytic reduction of NO with ammonia (NH3-SCR). In this study, we investigated the reaction mechanism of NH3-SCR catalyzed by a phosphorus-modified CHA zeolite that contains active Cu species (Cu-P-CHA), and assessed the effect of the phosphorus modification on the hydrothermal stability of the catalyst by employing in situ/operando spectroscopic methods. In their entirety, the combined results from in situ/operando IR, UV-vis, and XANES experiments revealed that the NH3-SCR process over Cu-P-CHA proceeds via the reduction of Cu(II) to Cu(I) followed by a reoxidation of Cu(I) to Cu(II). In addition, we found that the phosphorus modification improved the hydro thermal durability of the catalyst by retaining a higher amount of the redox-active Cu species and the zeolite framework
In Situ Spectroscopic Studies on the Redox Cycle of NH3−SCR over Cu−CHA Zeolites
No full textThe selective catalytic reduction of NO with ammonia (NH3-SCR) catalyzed by Cu-CHA zeolites is thoroughly investigated using in situ spectroscopic experiments combined with on-line mass spectroscopy (MS) under steady-state NH3-SCR conditions and transient conditions for Cu(II)/Cu(I) redox cycles. Quantitative analysis of the in situ XANES spectra of Cu-CHA under steady-state conditions of NH3-SCR show that NH3-coordinated Cu(II) species is the dominant Cu species at low temperatures (100-150 degrees C). At higher temperatures, Cu(II) species and [Cu(NH3)(2)](+) complex coexist, possibly because the rate of the Cu(II) -> Cu(I) reduction step is comparable to that of the Cu(I)-> Cu(II) oxidation step. In situ XANES, IR/MS, and UV-vis/MS experiments on the reduction half cycle demonstrate that the reduction of Cu(II) species occurs via the reaction of NH3-liganded Cu(II) with NO to yield N-2 and H2O. For the oxidation half cycle, in situ XANES experiments of Cu(I) oxidation in 10 % O-2 at 200 degrees C indicate that an increased density in CHA zeolite exhibits a higher oxidation rate. In situ UV-vis experiments of Cu(I) reoxidation using different mixtures of oxidant feed gas demonstrate the key role of O-2 in the oxidation cycle. It is suggested that the reoxidation of Cu(I) to Cu(II) species occurs with only O-2 as the oxidant, and a high Cu density in CHA zeolite promotes SCR activity by enhancing the oxidative activation of Cu(I) to Cu(II) during the catalytic cycle
Analisa Kadar Emisi NOx Menggunakan Bahan Bakar Biodiesel Minyak Biji Jarak Dengan Scr System Berbasis Eksperimen
No full textPenelitian yang dilakukan penulis bertujuan untuk menganalisis kadar emisi Nitrogen Oksida (NOx) yang dihasilkan oleh mesin diesel menggunakan bahan bakar biodiesel minyak biji jarak. Penelitian dilakukan dengan menggunakan (Selective Catalytic Reduction) SCR system dengan metode eksperimen. Katalis yang digunakan dalam SCR system yaitu zeolitebentonit dan agen pereduksinya yaitu larutan urea. Pada penelitian ini, penulis membandingkan dua bahan bakar sebagai pembanding dengan dua kondisi yang berbeda juga yaitu tanpa SCR system dan dengan SCR system. Pada penelitian ini persentase kenaikan kadar emisi terbesar dari pertamina dex ke B50 jarak kepyar terjadi pada beban 75% yaitu sebesar 24,53%. Dan penurunan emisi terbesar dari pertamina dex tanpa SCR ke pertamina dex dengan SCR terjadi pada beban 100% yaitu sebesar 23,71%. Penurunan emisi terbesar pada bahan bakar B50 jarak kepyar tanpa SCR ke B50 jarak kepyar dengan SCR terjadi pada beban 50% yaitu sebesar 23,38%. Hasil penelitian menunjukkan bahwa penggunaan biodiesel meningkatkan kadar emisi NOx jika dibandingkan dengan bahan bakar konvensional. Namun dengan penambahan SCR system berbasis zeolit-bentonit sebagai katalis dan larutan urea sebagai agen pereduksi mampu menurunkan kadar emisi NOx secara signifikan. Hal ini menunjukkan bahwa SCR system berbasis zeolit-bentonit sebagai katalis dan larutan urea sebagai agen pereduksi efektif dalam mereduksi emisi NOx yang dihasilkan mesin diesel yang menggunakan biodiesel minyak jarak.
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The research conducted by the author aims to analyze the emission levels of Nitrogen Oxide (NOx) produced by diesel engines using castor seed oil biodiesel fuel. The research was conducted using the SCR (Selective Catalytic Reduction) system with an experimental method. The catalyst used in the SCR system is zeolite-bentonite and the reducing agent is urea solution. In this study, the authors compared the two fuels as a comparison with two different conditions, namely without the SCR system and with the SCR system. In this study, the largest percentage increase in emission levels from Pertamina dex to B50 kepyar occurred at 75% load, which was 24.53%. And the biggest reduction in emissions from Pertamina Dex without SCR to Pertamina Dex with SCR occurred at 100% load, which was 23.71%. The biggest reduction in emissions from B50 rangefinder fuel without SCR to B50 rangefinder with SCR occurred at 50% load, namely 23.38%. The results showed that the use of biodiesel increased NOx emission levels when compared to conventional fuels. However, the addition of a zeolite-bentonite-based SCR system as a catalyst and urea solution as a reducing agent was able to significantly reduce NOx emission levels. This shows that the SCR system based on zeolite-bentonite as a catalyst and urea solution as a reducing agent is effective in reducing NOx emissions produced by diesel engines using castor oil biodiesel
A novel three-dimensional SCR motion simulator for modelling the catenary riser–seabed interaction in a centrifuge
No full textSteel catenary risers (SCRs) provide a cost-effective solution for deepwater oil and gas production. However, SCRs are susceptible to potential fatigue failure due to the cyclic motions of floating platforms. Previous studies on the physical modelling of cyclic SCR–seabed interactions have primarily focused on either the continuous cyclic motion of an SCR or a single rest period between two SCR motion packets. However, our understanding of the development of seabed trenches and excess pore pressure and their effects on SCR fatigue during multiple episodes of SCR motion and soil reconsolidation remains limited. This study presents a newly developed model container capable of modelling three-dimensional (3D) SCR motions including heave, surge, sway, and vortex-induced vibration (VIV) in a geotechnical centrifuge. A centrifuge test is conducted to investigate the vertical cyclic SCR–seabed interaction, considering five vertical cyclic motion packets with intervening periods of reconsolidation. The results indicate that ignoring the effects of reconsolidation leads to an overestimation of the fatigue life of an SCR. In this test, the SCR fatigue life is reduced by 18%–23% after five episodic SCR motion packets and intervening reconsolidation.The presentation of the authors' names and (or) special characters in the title of the pdf file of the accepted manuscript may differ slightly from what is displayed on the item page. The information in the pdf file of the accepted manuscript reflects the original submission by the author
Effect of late diesel injection on close-coupled SCR + ASC during DPF regeneration period
No full textFuture emission limits (Stage 6) for off-road engines will require more efficient removal of nitrogen oxides. The dual-SCR system has in addition of conventional main SCR catalyst after diesel oxidation catalyst (DOC) and particulate filter (DPF), a second SCR catalyst near to engine to enhance catalyst activity at low temperature periods. However, DPF regeneration requires periodic diesel fuel injection to DOC + DPF to oxidize carbonaceous particles at elevated temperatures. Late post-injection of diesel fuel was used during the regeneration period of a DPF. The study investigated how this strategy affects the performance of a close-coupled vanadium-based SCR with an ammonia slip catalyst. The exhaust aftertreatment system (SCR, DOC, DPF) was incorporated into the exhaust line of a high-speed, common-rail, diesel engine, designed for off-road applications fulfilling the latest emission legislation (Stage 5). Extensive bench experiments determined how late diesel injection through the close-coupled vanadium-SCR and ammonia slip catalyst affected the exhaust gas temperature, and whether high hydrocarbon concentrations from late diesel injection changed the catalyst performance. The SCR inlet temperatures ranged from 250 to 400 °C. Accumulation of hydrocarbons on the close-coupled vanadium-SCR catalyst at low exhaust temperatures was also examined. The studýs overall conclusion is that the strategy of late diesel injection is feasible to adopt during the regeneration period of a particulate filter only at sufficiently high SCR-inlet temperatures (≥ 320 °C). At lower temperatures, hydrocarbons might be stored in the catalyst. When the temperature increases again, exothermic reactions generated in the SCR may lead to notable catalyst deactivation.© 2024 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).fi=vertaisarvioitu|en=peerReviewed
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