Cold Start Period Research Articles

Improving vehicle warm-up performance in cold conditions using phase change materials

In cold climates, improving vehicle warm-up performance is crucial for reducing emissions and fuel consumption. Traditional methods often fail to efficiently address this issue, particularly during initial cold start periods. This study aims to enhance vehicle warm-up performance in cold conditions using phase change materials (PCMs). A thermal storage device was developed using paraffin wax, selected for its high energy density and a melting point of 69.3 °C, integrated with an optimized heat exchanger. Real road driving tests were conducted under urban and highway conditions, with temperatures ranging from −5 to 0 °C, using a 2.2L diesel engine vehicle. The results demonstrated a significant reduction in engine warm-up time by 20–30 %, leading to a decrease in fuel consumption and CO emissions by 365–517 g annually. The thermal storage device supplied up to 694.63 kJ of heat energy to the coolant, further improving vehicle efficiency and reducing environmental impact. Furthermore, evaluating PCM-based systems under real-world driving conditions is crucial for validating their practical effectiveness. Real-world variables introduce challenges that help confirm the applicability of PCM systems in everyday use. This approach shows potential for enhancing warm-up performance in cold climates without additional fuel consumption, outperforming conventional methods.

Energy analysis during cold start and warm up period of a methanol engine hybrid power system under several novel energy conversion strategies

The use of methanol in engine hybrid power system has a wide range of potential applications, with the primary challenge being cold start issues. This paper innovatively proposes four strategies for starting and warming up the methanol engine, including motor dragging, motor dragging coupled with exhaust gas recirculation (EGR), motor dragging coupled with exhaust control, and motor dragging coupled with both EGR and exhaust control. These strategies can be implemented in methanol hybrid power system with minimal hardware modification costs, and not generate any emissions compared to traditional gasoline assisted strategy. The warm-up mechanisms of these strategies were analyzed and their effectiveness was verified by experiments. The optimum strategy, motor dragging coupling both EGR and exhaust control, has been demonstrated to enhance power input and improve the energy conversion efficiency substantially. Compared to the traditional gasoline assisted strategy, the energy consumption, energy conversion efficiency and the warm-up time in this strategy are 17.9 % lower, 5.1 % higher, 4.2 s shorter, respectively. These strategies well solve the problem of methanol engines being unable to start at low temperatures, which is expected to eliminate the cold start of the engine and directly enter the hot start.

Robust, high-performance Cu-impregnated ZSM-5 zeolites for hydrocarbon removal during the cold-start period: Quantitative elucidation of effects of H+ and Na+ ions on performance and stability

Cu-containing zeolites are suitable for active hydrocarbon (HC) traps. Crucially, physicochemical properties of the zeolite could be finely tuned by varying the ion contents, though such approach has not been used intensively for HC trapping. Therefore, in this study, we adjusted the ratio of Na+ to H+ ions in ZSM-5 zeolites from 1 to 0 and, subsequently, wet-impregnated these zeolites with Cu. A low Na/Al ratio (≤0.4) resulted in marked cold-start test (CST) performance for HC removal in the fresh state (HC removal efficiency of 60.2 %-69.5 %). However, a hydrothermally treated counterpart having an optimal Na+ content (Na/Al ratio of 0.4) could well preserve the original active Cu+ ions along with zeolite structure and, accordingly, show the best CST performance after hydrothermal treatment (HT) at 800 °C (HC removal efficiency of 24.4 % vs. 10.8 % for the conventional H+-form-based one). Furthermore, we investigated adsorption behavior of water and HCs at a deep level and, further, revealed a clear correlation between the HC adsorption ability and CST performance and the representative physicochemical properties (mainly related to Cu+ ions) at all Na+ contents. Additionally, tiny CuO particles on the outer surface of the Cu-impregnated ZSM-5 zeolites having Na/Al ratios of 0–0.4 showed good low-temperature HC oxidation ability (ca. 175–182 °C). Although this HC oxidation ability was reduced after HT, an optimal Na/Al of 0.4 led to preservation of the original ability (ca. 283 °C vs. 320 °C for pure large CuO particles). Finally, we demonstrated a synergistic relationship between Na+ and H+ ion contents (Na/Al ratio of 0.4) that favored the formation of the desired Cu species, thus achieving marked HC adsorption and oxidation after HT.

Effects of fuel and driving conditions on particle number emissions of China-VI gasoline vehicles: based on corrections to test results.

The increasing number of vehicles are emitting a large amount of particles into the atmosphere, causing serious harm to the ecological environment and human health. This study conducted the Worldwide Harmonized Light Vehicles Test Cycle (WLTC) to investigate the emission characteristics of particle number (PN) of China-VI gasoline vehicles with different gasoline. The gasoline with lower aromatic hydrocarbons and olefins reduced particulate matter (PM) and PN emissions by 24% and 52% respectively. The average PN emission rate of the four vehicles during the first 300s (the cold start period) was 7.2 times that of the 300s-1800s. Additionally, because the particle transmission time and instrument response time, the test results of instantaneous emissions of PN were not synchronized with vehicle specific power (VSP). By calculating the Spearman correlation coefficient between pre-average vehicle specific power (PAVSP) and the test results of PN instantaneous emissions, the delay time was determined as 10s. After the PN emissions results were corrected, the PN emissions were found to be more related to VSP. By analyzing the influence of driving status on emission, this study found that vehicles in acceleration mode increased PN emissions by 76% compared to those in constant speed mode.

Enhanced Low-Temperature Activity and Hydrothermal Stability of Ce-Mn Oxide-Modified Cu-SSZ-39 Catalysts for NH3-SCR of NOx

Cu-SSZ-39 zeolite with an AEI structure exhibits excellent hydrothermal stability and can be a potential alternative to Cu-SSZ-13 zeolite SCR catalysts for NOx removal in diesel vehicles. However, the inferior low-temperature performance of Cu-SSZ-39 leads to substantial NOx emissions during the cold-start period, impeding its practical application. In this study, Ce-Mn oxide-modified Cu-SSZ-39 catalysts (CeMnOx/Cu-SSZ-39) and references (CeO2/Cu-SSZ-39 and MnOx/Cu-SSZ-39) were prepared by the ion-exchange of Cu ions followed by impregnation of the oxide precursors, with the aim of enhancing the NH3-SCR performance at low temperatures. The modified catalysts exhibited improved low-temperature activity and hydrothermal stability compared to the unmodified counterpart. In particular, CeMnOx/Cu-SSZ-39 showed the highest activity among the three catalysts and achieved NOx conversions above 90% within the temperature range of 180 °C to 600 °C, even after undergoing hydrothermal aging at 800 °C. Experimental results indicated that the synergistic effect between Ce and Mn in CeMnOx improves the redox properties and acidity of the catalyst due to the presence of Ce3+, Mn4+, and abundant adsorbed oxygen species, which facilitate low-temperature SCR reactions. Furthermore, the interaction of CeMnOx with Cu-SSZ-39 stabilizes the zeolite framework and hinders the agglomeration of Cu species during the hydrothermal aging process, contributing to its exceptional hydrothermal stability. The kinetics and NO oxidation experiments demonstrated that CeMnOx provides access to fast SCR reaction pathways by oxidizing NO to NO2, resulting in a significant increase in low-temperature activity. This study provides novel guidelines for the design and preparation of Cu-SSZ-39 zeolite with outstanding SCR performance over a wide temperature range.

Experimental study on improving cold start performance of diesel engines at extremely low ambient temperatures with diethyl ether

How to achieve a fast and reliable cold start of diesel engines at extremely low temperatures is a significant and longstanding problem. In this study, a precise amount of diethyl ether was premixed in the intake to facilitate the starting at extremely low ambient temperatures down to −40 °C. The study investigated the effects of diesel fuel injection strategies, diethyl ether concentration, and ambient temperature on the cold-start performance. Additionally, an analysis was conducted on energy consumption and heat loss during the cold start period. The test engine could start quickly and steadily when diethyl ether was premixed in the intake. This was achieved by optimizing the diesel injection quantity to 60% of the original quantity and retarding the injection timing from 6 oCA BTDC to 2 oCA BTDC. The engine exhibited reliable starting at −40 °C when 2.0% v/v diethyl ether was premixed. However, excessive direct injection of diesel had an adverse effect on fuel ignition at such extremely low temperatures. Moreover, the electricity consumption was much lower with diethyl ether premixed in the intake than that with an electric intake heater, greatly reducing the requirements for starting batteries during the cold start under extremely low-temperature conditions.

Deciphering H2-induced low-temperature NOx adsorption on Ag/Al2O3: Expanding the operating temperature range of ethanol-SCR system for effective NOx abatement

Despite the advantages of the catalytic reduction of NOx by hydrocarbons, typical Ag/Al2O3 suffers from limited low-temperature activity in response to cold-start periods. In this study, the promotional effect of H2 on NOx adsorption on Ag/Al2O3 was investigated to address the low-temperature NOx emissions. H2 significantly enhanced NOx accumulation on Ag/Al2O3 below 200 °C, with desorption occurring at high temperatures. The H2-temperature-programmed reduction (H2-TPR) results showed the formation of silver oxide on metallic Ag species by H2+O2, serving as the primary site for H2-induced NOx adsorption, while the single-atom Ag species (Ag+) remained nearly unchanged. Ag/Al2O3 with low Ag loading (1–2 wt%) exhibited lower NOx adsorption capacities compared to the case with high Ag loading (4 wt%) owing to the low metallic Ag content. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) studies identified diverse surface-adsorbed species related to H2-induced NOx adsorption. Nitrite, bridging nitrate, and bidentate nitrate contributed to low-temperature NOx desorption, whereas monodentate nitrate contributed to high-temperature desorption. Finally, we demonstrated exceptionally-high NOx reduction activity by synergistically combining the NOx trapping ability of Ag/Al2O3 with its deNOx capability through ethanol with H2, covering a wide temperature range of 100–350 °C under transient conditions at a high space velocity of 100,000 h−1.

Revealing the Roles of Cu/Ba on Ce-Based Passive NOx Adsorbers

At present, passive NOx adsorbers (PNAs) represent one of the most effective technologies for addressing NOx emissions from diesel engines during cold-start periods. Conventional PNAs, which primarily consist of noble metals (such as Pt, Pd, and Ag) loaded on metal oxides or zeolites, share the common drawback of high production costs. Consequently, developing low-cost PNAs with outstanding NOx storage performance remains a significant challenge. In this study, a series of CuxBa5Ce adsorbents were synthesized using the impregnation method, and a monolithic adsorbent was employed to evaluate NOx storage and release performance. Techniques such as XRD, UV-Vis DRs, H2-TPR, XPS, and in situ DRIFTs confirmed the crucial roles of Cu and Ba in NOx storage and release. Specifically, the incorporation of Cu into CeO2 enhanced NOx storage performance. Moreover, in the Cu3Ba5Ce adsorbent, the addition of Ba not only introduced new storage sites and altered the stability of NOx adsorption species but also helped prevent the aggregation of CuO, thereby prolonging the complete NOx storage duration and satisfying desorption temperature requirements. The Cu3Ba5Ce adsorbent exhibited the most favorable NOx storage performance, including a complete NOx storage time of 135 s and a NOx storage efficiency exceeding 50% at 80 °C over a 10 min period. While PNAs loaded with noble metals, such as Pd/CeO2 and Pt/CeO2, exhibited NOx storage efficiencies below 50% after adsorbing for 5 min at 80 °C. Therefore, this research offered a crucial strategy for developing non-noble-metal-loaded, Ce-based PNAs.

Exploring the framework of small pore zeolites for passive NOx adsorption

The use of a passive NOx adsorber (PNA) for NOx storage during the cold-start period is crucial for eliminating NOx emissions from the diesel exhaust. Palladium (Pd)-loaded zeolites have garnered significant attention owing to their high potential as PNA. In this study, small-pore zeolites with different frameworks were synthesized, and their structural characteristics and passive NOx adsorption abilities were investigated. Five zeolites, with CHA, AEI, AFX (low- and high- Si/Al ratio), and LEV framework structures, were synthesized by the hydrothermal conversion of faujasite-type (FAU) zeolite. Pd (1 wt%) was impregnated in combination with hydrothermal treatment. NOx adsorption and desorption behaviors were studied based on breakthrough NO adsorption and subsequent temperature-programmed desorption (TPD) experiments. Pd-loaded CHA, AEI, and LEV zeolites and high-silica AFX zeolites adsorbed approximately 93.88, 107.93, 97.57 and 106.53 μmol-NO g−1, respectively. On the other hand, the incorporation of Pd into AFX zeolite with a low Si/Al ratio led to significant hydrothermal damage and resulted in lower levels of adsorption and desorption capabilities. This demonstrates that hydrothermally stable small-pore zeolites on Pd-incorporation have great potential for passive NOx adsorption. The zeolite with different framework exhibited the different temperature range of NOx release. CHA, AEI, and high-silica AFX zeolites desorbed NOx in the low-temperature region (T < 250 °C), whereas the LEV zeolite showed a relatively high NOx desorption amount in the middle-temperature region (250 °C < T < 350 °C).

Real-time vehicular fuel consumption estimation using machine learning and on-board diagnostics data

Instantaneous fuel consumption estimation of fleet vehicles provides essential tools for fleet operation optimization and intelligent fleet management. This study aims to develop practical and accurate models to estimate instantaneous fuel consumption based on on-board diagnostics (OBD) data. Fuel consumption data is measured by a high-precision fuel flow meter. Two machine learning algorithms of Random Forest (RF) and Artificial Neural Networks (ANN) are trained with real-world urban and highway driving data of four fleet vehicles with different types and powertrain systems. In addition, the cold-start period of the vehicle operation is included to cover the fuel consumption penalty in the warm-up period. The validation results show that the RF method is more accurate than the ANN method, and both of the machine learning models have a better accuracy compared to the existing fuel consumption calculation methods based on the engine control unit (ECU) parameters.

Novel layered double hydroxide-based passive NOx adsorber: Synergistic effects of Co and Mn on low-temperature NOx storage and regeneration

Passive NOx adsorber (PNA) is an efficient strategy for reducing vehicular NOx emission during cold-start period, and current studies on PNA development are limited to materials containing precious metals (Pt, Pd, and Ag, etc.). Herein, Co–Mn–Mg–Al mixed metal oxides were prepared from layered double hydroxides (LDHs) and utilized as a new type of PNA. Although Co–Mg–Al oxides exhibited excellent NOx adsorption capabilities because Co species promoted the generation of active oxygen species, their NOx adsorption performance deteriorated substantially with decreasing adsorption temperature below 150 °C and they required high temperatures over 400 °C to release the adsorbed NOx. Conversely, Mn–Mg–Al oxides retained their adsorption performance regardless of adsorption temperature and allowed for NOx desorption at relatively low temperatures by decreasing the thermal stability of the adsorbed NOx species. Notably, Co–Mn–Mg–Al mixed oxides exhibited high NOx adsorption performance at low temperatures between 50 and 150 °C and were passively regenerated via thermal treatment within a temperature range of 200–350 °C owing to the synergistic effects of Co and Mn. The developed LDH-based PNA materials presented excellent cyclic NOx adsorption performances for long-term operation, and dynamic tests indicated that NOx adsorbed onto Co–Mn–Mg–Al mixed oxides was effectively released with increasing temperature even in the presence of NO and O2.

A study on the renewable power generation capacity of microalgae microbial fuel cells for powering GIoT sensor nodes

Microalgae-Microbial Fuel Cell (mMFC) is a novel and attractive green renewable energy source for bio-electricity generation. Its capacity to generate energy is of particular interest for the design of sustainable green internet of things (GIoT) sensor networks. However, this capacity needs to be assessed due to critical limitations in their low-level output voltage and possible bioelectrochemical disturbances. This study investigates the renewable energy generation capacity of an mMFC-harvester system for powering low-power wireless sensor nodes. A two-chamber mMFC prototype is designed as a proof of concept using the CMI7000 membrane and the BQ25570 circuit to harvest the energy. A sensor node based on Nordic nRF52840 ultra-low-power microcontroller implements a uniform power management strategy and the energy capacity is analyzed in terms of the number of Bluetooth low energy (BLE) transmissions. Experimental results show that after an initial cold-start period in the harvester circuit, the system stores the energy in a 0.1 F supercapacitor in 6.25 h, representing 3.26 J. The maximum power density generation is 80.10 mW/m2, and the energy harvested is suitable to perform up to 9 continuous transmissions using BLE.

Mechanistic insights into the cobalt promotion on low-temperature NH3-SCR reactivity of Cu/SSZ-13

The ever-increasing demand for nitrogen oxides (NOx) emission control from diesel engines during cold start period has provided a strong impetus to improve the low-temperature NOx removal efficiency of Cu/SSZ-13 catalyst. In this work, a series of bimetallic catalysts CuCo/SSZ-13 with varying cobalt contents were prepared, and attained the significant performance enhancement in NH3 selective catalytic reduction (NH3-SCR) reaction. The promotion mechanism of these catalysts at low temperatures (< 200 °C) was proposed: (1) The introduced Co(II) ions could tune the distributions of copper species and acid sites, resulting in a higher ratio of ZCuOH/Z2Cu (Z represents a negatively charged site on zeolite framework) and much more Lewis acid sites compared with original Cu/SSZ-13. (2) The fast reaction of reactive bridging nitrates with NH3 adsorbed on Lewis acid sites via Langmuir-Hinshelwood (L-H) mechanism decreased the activation energy. However, the addition of high cobalt content facilitated the formation of inactive CuOx species, which was not conducive to maintaining high-temperature (> 500 °C) activity.

Cold-Start NOx Mitigation by Passive Adsorption Using Pd-Exchanged Zeolites: From Material Design to Mechanism Understanding and System Integration.

It remains a major challenge to abate efficiently the harmful nitrogen oxides (NOx) in low-temperature diesel exhausts emitted during the cold-start period of engine operation. Passive NOx adsorbers (PNA), which could temporarily capture NOx at low temperatures (below 200 °C) and release the stored NOx at higher temperatures (normally 250-450 °C) to downstream selective catalytic reduction unit for complete abatement, hold promise to mitigate cold-start NOx emissions. In this review, recent advances in material design, mechanism understanding, and system integration are summarized for PNA based on palladium-exchanged zeolites. First, we discuss the choices of parent zeolite, Pd precursor, and synthetic method for the synthesis of Pd-zeolites with atomic Pd dispersions, and review the effect of hydrothermal aging on the properties and PNA performance of Pd-zeolites. Then, we show how different experimental and theoretical methodologies can be integrated to gain mechanistic insights into the nature of Pd active sites, the NOx storage/release chemistry, as well as the interactions between Pd and typical components/poisons in engine exhausts. This review also gathers several novel designs of PNA integration into modern exhaust after-treatment systems for practical application. At the end, we discuss the major challenges, as well as important implications, for the further development and real application of Pd-zeolite-based PNA in cold-start NOx mitigation.

Impact of the Internal Combustion Engine Thermal State during Start-Up on the Exhaust Emissions in the Homologation Test

Due to the increasingly restrictive exhaust emissions requirements from conventional vehicles, the internal combustion engine start-up seems to be most important part of engine operation. The period immediately after starting the engine is the time when the exhaust emissions are highest, thus, this aspect is currently subject to heavy analysis. The article evaluates the impact of the engine thermal state during its start-up for a Euro 5 emission class vehicle type approval test. The engine thermal state during start-up turned out to have a crucial influence (throughout the approval test) on the results of the hydrocarbons road emission (a difference of about 1500%) and the road emission of carbon monoxide (63%). The remaining road exhaust emission values were less sensitive to the thermal state of the engine during start-up—the nitrogen oxides emission value increased by 18% (for a cold start compared to a hot start), and the road fuel consumption (and thus the emission of carbon dioxide) increased by about 6%. In conclusion, the authors refer to technical solutions that may have a significant impact on reducing the exhaust emissions in the considered period of engine cold start.

Application progress of small-pore zeolites in purifying NOx from motor vehicle exhaust

• Small-pore SSZ-13 and SSZ-39 zeolites have unique advantages in purifying NOx. • Pd/zeolites as PNAs present the superior low-temperature NOx adsorption activity. • Non-precious metal Co/zeolite is an ideal substitute for Pd/PNAs to reduce the cost. • Cu/zeolites possess the excellent high-temperature NH3-SCR catalytic activity. • Fe/Mn/Ce doped Cu/zeolites can broaden the NH3-SCR active temperature window. Lean-burn mode results in the high NOx emission of diesel vehicles despite its high fuel economy. NOx can be effectively removed by the SCR unit during normal operation, however, elimination during the cold start period needs to be addressed soon. Passive NOx adsorber (PNA) was proposed to adsorb and store NOx emitted during the cold start period. With the increase of exhaust gas temperature during normal operation, the adsorbed NOx will be quickly released and efficiently converted to N 2 when flowing through the downstream SCR catalyst. After years’ investigation, small-pore zeolites such as CHA and AEI have been found to possess superior hydrothermal stability and NOx selectivity compared with medium and large pore zeolites, and the former’s eight-membered ring structure effectively exclude large hydrocarbons from entering the zeolite channels, making them play a prominent role in NOx purification via both PNA and SCR units. SSZ-13 and SSZ-39 zeolites, which belong to CHA and AEI topologies respectively, has been confirmed to exhibit excellent low-temperature NOx adsorption performance and high-temperature SCR denitrification performance. In the field of purifying NOx from the diesel vehicle exhaust, the review simultaneously focused on the application of SSZ-13 and SSZ-39 zeolites in NOx purification from two aspects of PNA and SCR in recent decades. In addition, the unique advantages of their modified form of loading Pd/Co as PNAs, or loading Cu doped with Fe/Mn/Ce as SCR catalysts were systematically clarified, in order to provide some advanced guidance for the researchers in the purification of NOx from the diesel engine exhaust.

Experimental and Theoretical Studies of Pd Cation Reduction and Oxidation During NO Adsorption on and Desorption from Pd/H–CHA

Passive NOx adsorbers (PNAs) have been proposed for trapping NOx present in automotive exhaust during the period of cold start during which the three-way convertor is not yet hot enough to be effective for NOx reduction. Pd-exchanged chabazite (Pd/H–CHA) is a good candidate for passive NOx adsorption due to its ability to store NO and retain it to high temperatures (>473 K). Previous research suggests that NO adsorbs on both Pd2+ and Pd+ cations and that NO desorption from Pd2+ cations occurs at lower temperatures than from Pd+ cations. Since experimental evidence shows that Pd exchanges into CHA exclusively as Pd2+, it is not clear how these cations are reduced to Pd+. In this study we show through experiments and theoretical analysis that Pd+ cations can form via two processes, each of which involves water adsorbed on Brønsted-acid sites of the zeolite. The first of these processes is 1.5 NO + Pd2+Z–Z– + 0.5 (H2O)H+Z– → (NO)Pd+Z–H+Z– + 0.5 NO2 + 0.5 H+Z–. Experiments confirm that the ratio of the NO2 formed upon NO adsorption to the NO desorbing from Pd+ at elevated temperatures corresponds to 0.5. Pd2+ can also be reduced via the reaction 1.5 CO + Pd2+Z–Z– + 0.5 (H2O)H+Z– → (CO)Pd+Z–H+Z– + 0.5 CO2 + 0.5 H+Z–. Upon subsequent adsorption of NO, NO fully displaces CO from Pd+ to form (NO)Pd+Z–H+Z–. In this case, the amount of CO2 formed upon CO adsorption is 0.5 of the NO desorbing at elevated temperatures from Pd+. Gibbs free energy calculations for the above processes at various potential ion-exchange sites in the CHA framework indicate that these reactions are thermodynamically feasible. We also find that Pd+ is not formed in the absence of adsorbed water and is readily reoxidized to Pd2+ by trace amounts of O2.

Hydrocarbon emission control of an adsorptive catalytic gasoline particulate filter during cold-start period of the gasoline engine

In order to reduce HC emission of the gasoline engine during cold start to meet increasingly stringent emission standards, an adsorptive catalytic gasoline particulate filter (A-CGPF) is proposed and a mathematical model of the A-CGPF is established. Then, HC adsorption performance, conversion performance and abatement performance of the A-CGPF coated with different catalyst under different inlet HC concentration are investigated during cold start. The results show that inlet HC concentration, exhaust temperature has great influence on the adsorption process, while mass flow rate has little influence; penetration time decreases with the increase of inlet hydrocarbon concentration. In addition, the catalytic conversion performance order is MCA > Rh–Pd > CeO2 > PCZ > Pd under adiabatic condition, their corresponding light-off time is 10s, 34s, 56.4s, 57s and 57.2s, respectively. Compared with the A-CGPF coated with adsorbent or catalyst, adsorption duration time of the A-CGPF coated with composite adsorptive catalysts is shortened, and its catalytic oxidation stage is advanced; the cumulative HC emission in the first 40s of the cold start phase is significantly reduced and the HC removal rate is increased; the HC removal performance order is MMC > MRP > MC > MP > MPCZ, and the HC removal blank period due to interaction effect between adsorption and catalytic oxidation can be properly shortened. Moreover, the inlet HC concentration fluctuation results in the deterioration of carrier temperature rise, prolongs the removal blank period, and decreases the HC removal rate at the initial stage of cold start. Compound rare earth oxide MCA has better HC abatement performance than other catalysts. This work provides reference for hydrocarbon abatement performance enhancement of a GDI engine and design of coupled after-treatment system.

Effects of the ZSM-5 zeolites on hydrocarbon emission control of gasoline engine under cold start

The feasibility of ZSM-5 zeolite for controlling hydrocarbon (HC) emissions during cold start period of gasoline engine was studied by temperature programmed desorption (TPD) experiment and molecular simulation (MS). Acetylene, 1-butene, propylene, ethylene, acetaldehyde and benzene molecules were selected as representative HCs based on the HC emission components of gasoline engine cold start experiment. TPD experiment was carried on commercial ZSM-5, and desorption intensity curve of ZSM-5 zeolite for main cold start hydrocarbons was obtained. TPD results indicated that ZSM-5 zeolite can retain most of the hydrocarbons after 472 K, and the overall desorption intensity on ZSM-5 zeolite is acetaldehyde>1-butene > acetylene. Then adsorption and diffusion properties of the six main cold start hydrocarbon components on Na-ZSM-5 zeolite with different Si/Al ratio were studied by grand canonical Monte Carlo (GCMC) method and canonical ensemble Molecular Dynamics (MD) method. The results showed that the adsorption and diffusion of single-component hydrocarbons on ZSM-5 zeolite were affected by the number of exchange cations of zeolite, environment temperature, diameter of HC molecules and covalent bond types of HC molecules, and the adsorption capacity and diffusion coefficient were also affected by the competitive effect between the HC components. In competitive adsorption, molecules with large diameters such as acetaldehyde, 1-butene and benzene occupied the main adsorption sites of zeolite, so the adsorption capacity of these three HC molecules was large, while the adsorption capacity of smaller molecules such as ethylene, acetylene and propylene were small.

LiLo: ADL Localization with Conventional Luminaries and Ambient Light Sensor

Indoor localization is a key factor for activities of daily living (ADLs)-related services. Many studies invest effort and money on high-cost infrastructure with modified devices. In this paper, an indoor localization system (LiLo) that utilizes ambient light sensor and orientation information on smartphones to recognize ADLs is proposed. Indoor ADLs are recognized by analyzing the data combination of visible light based localization, orientation and time. In the cold start period, LiLo estimates the location based on the computed luminance field map and the frequent orientation, validating the location result by the angle of arrival information. Then, LiLo produces the locations with a machine learning classifier. Compared with previous works, LiLo leaves out the laborious device configuration setup and data collection during the off-line phase. Another advantage is that LiLo utilizes a conventional luminaire and a standard smartphone, without extra infrastructure spreading in rooms. Therefore, every resident with a smartphone can benefit from this technology. An experimental study using data collected from smartphones shows that LiLo is able to achieve high localization accuracy at a low cost.