Emission Control Systems Research Articles

The impact of energy flow on catalytic behavior in advanced DOC+SCR emission control systems

To further improve the catalytic efficiency of the aftertreatment system in exhaust conditions, the exhaust decoupling system is employed to investigate the effect of energy flow on aftertreatment catalytic systems (SCR & DOC+SCR) at wide engine load conditions (10–100 %). The physicochemical properties of particulate matter (PM) are analyzed by transmission electron microscopy (TEM). Furthermore, the energy flow and catalytic performances under the World Harmonized Transient Cycle(WHTC) are revealed. The research results exhibited that the energy distribution of exhaust in “DOC+SCR” was 10–15 % higher than that in “SCR” under steady state conditions, the provision of additional activation energy enhances the catalytic reaction, thereby improving the rate of the reaction, particularly in terms of NOx catalytic efficiency. On the other side, under transient conditions, the energy distribution of exhaust in “DOC+SCR” was 8.72 % higher than that in “SCR”. The NO/NO2 ratio remains stable value after the exhaust passing through DOC, thereby promoting the formation of rapid SCR reaction conditions. By revealing the PM microstructure, DOC enhances PM’s microcrystalline tortuosity and reduces particle size, thereby improving its oxidation reaction characteristics through combined catalysis. Simultaneously, this study demonstrates that the optimized combined catalytic method holds great potential for complete PM treatment.

Unveiling the Stability of Encapsulated Pt Catalysts Using Nanocrystals and Atomic Layer Deposition.

Platinum exhibits desirable catalytic properties, but it is scarce and expensive. Optimizing its use in key applications such as emission control catalysis is important to reduce our reliance on such a rare element. Supported Pt nanoparticles (NPs) used in emission control systems deactivate over time because of particle growth in sintering processes. In this work, we shed light on the stability against sintering of Pt NPs supported on and encapsulated in Al2O3 using a combination of nanocrystal catalysts and atomic layer deposition (ALD) techniques. We find that small amounts of alumina overlayers created by ALD on preformed Pt NPs can stabilize supported Pt catalysts, significantly reducing deactivation caused by sintering, as previously observed by others. Combining theoretical and experimental insights, we correlate this behavior to the decreased propensity of oxidized Pt species to undergo Ostwald ripening phenomena because of the physical barrier imposed by the alumina overlayers. Furthermore, we find that highly stable catalysts can present an abundance of under-coordinated Pt sites after restructuring of both Pt particles and alumina overlayers at a high temperature (800 °C) in C3H6 oxidation conditions. The enhanced stability significantly improves the Pt utilization efficiency after accelerated aging treatments, with encapsulated Pt catalysts reaching reaction rates more than two times greater than those of a control supported Pt catalyst.

The Effect of Using Crankcase Emission Control System Technology on the Performance of a 160 cc Single Cylinder Four Stroke Engine

The research was carried out on a single-cylinder four-stroke petrol engine with a rotation variation of 1000 rpm - 9000 rpm, using crankcase emission control system (CECS) technology. The air that will enter the carburetor is mixed with hot gas that flows and comes from the CECS, causing the air to become warm and then mixed with the fuel in the carburetor and then the mixture passes through the manifold into the combustion chamber. Investigation in the first stage under standard conditions and in the second stage using CECS technology. The use of CECS technology results in increased machine performance. After testing with and without using CECS technology, optimum performance in the form of power, torque and specific fuel consumption occurred at engine speeds of 8000 rpm, 6000 rpm and 7000 rpm respectively producing power, torque and specific fuel consumption of 13.11 ; 1.504 kg.m and 0.152 kg/hp.hour without CECS, and with the use of CECS technology of 13.20 hp; 1.56 kg.m and 0.151 kg/hp.hour.

RESEARCH ON THE EFFICIENCY OF CATALYTIC CONVERSION OF EXHAUST GASES FROM A CAR ENGINE DURING WARM-UP MODE

The article is dedicated to researching the efficiency of catalytic conversion of exhaust gases from VW BBY car engine (4FS 7.65/7.56) during warm-up mode. The objective of the study is to determine the impact of structural and operational factors of emission control systems on their efficiency during the warm-up phases of car engines. A compre-hensive research methodology has been developed, which includes experimental investigations of the engine and catalyt-ic converter warm-up processes and their influence on harmful emissions. It has been established that during engine warm-up at idle, the attainment of chemical and thermal conditions necessary for the effective operation of the exhaust gas neutralization system occurs at different times: chemical conditions are reached earlier, while thermal conditions are reached later. The nominal efficiency of neutralizing various harmful exhaust gas components (CO, HC, NO) is achieved at different times and temperatures of the catalytic converter: for NO in 180 seconds at 295 °C; for CO in 220 seconds at 305 °C; and for HC in 400 seconds at 330 °C. The necessary chemical operating conditions are reached in 100 seconds at 230 °C. Furthermore, the attainment of the system’s nominal neutralization efficiency is almost independent of the time taken for the engine to reach its operational temperature based on the coolant temperature. The primary catalytic converter has little impact on emission levels in this mode due to not reaching its operational temperature. The results of the experimental research provide an opportunity to refine the theoretical model for determining the influence of structural and operational factors of emission control systems on harmful emissions and to establish a combination of factors for reducing emissions. Keywords: car engine, operating mode, fuel consumption, catalytic converter temperature, concentrations of harmful substances, exhaust gases.

Challenges and Solutions to Meet the Euro 7 NOx Emission Requirements for Diesel Light-Duty Commercial Vehicles

AbstractThe improvement of air quality requires a further reduction of pollutant emissions, especially in urban areas. The Euro 7 regulations aim at the development of a new generation of internal combustion engine vehicles capable of achieving ultra-low pollutant emissions under demanding, real-world operating conditions. They introduce new technical challenges in the holistic design of a vehicle’s powertrain and emission control system. To identify these, four real-world Euro 7 driving scenarios are investigated, covering demanding urban, highway and mountain driving situations. Technical solutions are then presented to address these challenges and ensure compliance with the Euro 7 emission requirements as set out in the latest regulation proposal of the European Commission. The study focuses on the NOx emissions of an N1 Class III light commercial vehicle with 3.5 t mass and a P2 diesel mild-hybrid powertrain. To ensure emission compliance, a Euro 6e exhaust gas aftertreatment system with enlarged catalysts is combined with NOx raw emission improvements. For low-load cold starts, a 4-kW electric heater in the exhaust system is considered in addition to a 2-l DOC and a 6-l DPF with SCR coating. For high-load cycles with high raw emissions, a 10-l underfloor SCR is considered to ensure the necessary deNOx performance.

Experimental research and estimation model of gasoline evaporative emissions from vehicles in China

Evaporative emission is an important source of vehicle pollutant emission and volatile organic compounds (VOCs), causing serious environmental pollution. Carbon canisters are used to store fuel vapor in evaporative emission control (EVAP) system, but canisters are prone to saturation, leading to the direct release of fuel vapor into the atmosphere. Therefore, accurate estimation of fuel vapor generation is crucial for EVAP system. Gasoline evaporation rate is mainly influenced by vapor-liquid interface area, gasoline saturated vapor pressure, filling level and temperature. The quantitative relation between different parameters and gasoline evaporation rate has rarely been reported, and a gasoline evaporative emission estimation model suitable for China needs to be proposed urgently. In this study, gasoline evaporative emission tests have been carried out in VT-SHED, and the effects of vapor-liquid interface area, filling level and temperature on gasoline evaporative emissions have been analyzed under the premise of consistent gasoline temperature and ambient temperature. Some valuable conclusions are obtained. The results show that different from expectation, gasoline evaporative emissions are not positively correlated with the vapor-liquid interface area. There is an approximately exponential relationship between the headspace volume and gasoline evaporative emissions. The widely used Reddy equation and Hata equation underestimate the gasoline vapor generation in China. Based on China VI test program and gasoline, accurate estimation of mass transfer coefficient has been conducted, and a new semi-empirical estimation model for vapor generation has been proposed. The model can accurately estimate the fuel evaporation of vehicles in China, providing guidance for the matching and optimization of EVAP system.

A picture of artisanal and small-scale gold mining (ASGM) in Brazil and its mercury emissions and releases.

This study presents a picture of ASGM in Brazil and prospective numbers on mercury emissions and releases in 2016, when the country declared production of about 90 tonnes of gold, of which circa 25 tonnes came from ASGM. However, it is also necessary to consider the illegal production of ASGM which is estimated to vary between 10% and eight times more than the legal production. The proposed method included: organization of spatial data on legal ASGM output, stakeholder identification and meetings, mercury metallurgical balance, quantitative measurement of mercury in the atmosphere and qualitative social aspects such as the miners' economic dependence on the managers and scenarios of illegal ASGM annual production. The main results revealed that the initial mercury (Hg)-gold (Au) production ratio was higher for the primary whole ore than for the concentrate secondary ore, which is the most frequent type of Brazilian ASGM. The amalgam filtering technique followed by mercury recovery is routine, decreasing the Hg releases to tailings ponds or to soil and water bodies. The mercury emissions by thermal decomposition of amalgam are independent of the initial mercury mass, depending only on the mercury in the amalgam and the (adequate) use or not of emission control systems. Illegal activities reduce the availability and proper use of these systems, resulting in higher emissions. Mercury emissions from ASGM in Brazil may increase the global mercury emissions estimates, while their mercury releases may represent a marginal increase. As the mercury emitted may be trapped by the rainforests added to the mercury released, the environmental contamination may pose health risks to Amazonian population, which requires immediate action.

An Estimate of the NOX Emissions of Euro 6 Diesel Passenger Cars with Manipulated Emission Control Systems

The motivation for conducting this research stems from the increasingly applied manipulations of emission control systems (ECSs), especially those in diesel passenger cars (PCs). The study aimed to investigate the influence of manipulations of exhaust gas recirculation (EGR) valves and a diesel exhaust fluid (DEF)-dosing system on the nitrogen oxide (NOX) emissions of a Euro 6 diesel vehicle and, through the quantification of vehicles with manipulated ECSs, estimate the emissions of Euro 6 diesel PCs. Portable emissions measurement system (PEMS) measurements were performed on a Euro 6 diesel vehicle at a constant speed and on real driving emission (RDE) routes. The speed-dependent functions of the NOX hot emission factor (EF) were calculated for seven different scenarios. The results showed that the NOX EFs for the worst-case scenarios were more than two orders of magnitude higher than those where all ECSs were active. Applying the calculated EFs and the survey answers on the percentage of manipulated PCs to the Croatian Euro 6 diesel PC fleet, the results showed that the emission levels were up to 46.3% higher than the emissions calculated by the official computer program COPERT v5.6.5, with a tendency towards significantly higher values. The main conclusion is that vehicle manufacturers, policymakers, and the general public need to be informed about the enormous damage that in-use vehicles with manipulated ECSs cause to the environment and human health, in order to prevent such actions.

Large Decreases in Tailpipe Criteria Pollutant Emissions from the U.S. Light-Duty Vehicle Fleet Expected in 2020-2040.

The U.S. EPA MOVES3 model was used to assess the impact of the large-scale introduction of electric vehicles on emissions of criteria pollutants (CO, hydrocarbons [HC], NOx, and particulate matter [PM]) and CO2 from the U.S. light-duty vehicle fleet. Large reductions in emissions of these criteria pollutants occurred in 2000-2020. These trends are expected to continue through 2040 driven by turnover of the conventional fleet with old vehicles being replaced by battery electric vehicles (BEVs) and by new internal combustion engine vehicles (ICEVs) with modern emission control systems. Without the introduction of BEVs, the absolute emissions of CO, NOx, HC, and PM2.5 from the U.S. light-duty vehicle fleet are expected to decrease by approximately 61, 88, 55, and 20% from 2020 to 2040. Introduction of BEVs with market share increasing linearly to 100% in 2040 provides additional benefits, which, combined with ICEV fleet turnover, would lead to decreases of absolute emissions of CO, NOx, HC, and PM2.5 of approximately 77, 94, 71, and 37% from 2020 to 2040. Reductions in CO2 emissions follow a similar pattern. Large decreases in criteria pollutant and CO2 emissions from light duty vehicles lie ahead.

Review of the Current State of Pyrolysis and Biochar Utilization in Europe: A Scientific Perspective

This scientific paper provides an overview of the current state of pyrolysis in Europe, with a focus on mapping the key research areas and technologies employed. This research relied on search equations that centered on the utilization of biomass and plastics as primary feedstocks in pyrolysis, with a particular emphasis on biochar generation and different technologies applied. The results showed that both plastic and biomass pyrolysis can contribute to reducing waste and mitigating greenhouse gas emissions. However, plastic pyrolysis can release harmful pollutants due to the presence of chlorine and other additives in plastics, which requires sophisticated emission control systems to be implemented. The production of biochar from sewage sludge is identified as a promising approach for phosphorus recovery, which can subsequently be utilized as a valuable fertilizer in agricultural applications. The data from this study contribute to exploring future applications at pilot and industrial scales for pyrolysis, with a critical assessment of the use of feedstocks. Moreover, this work provides information about current companies that are already operating on a large scale with pyrolysis and a map of the principal countries in Europe engaged in pyrolysis research, correlating the characteristics of the pyrolysis processes investigated.

Energy, exergy, sustainability, thermoeconomic, exergoeconomic, environmental and environmental-economic effects of novel boron-containing open cell geopolymer filter of a diesel engine on exhaust emissions

In this study, the energy, exergy, sustainability, thermoeconomic, exergoeconomic, environmental and environmental-economic based analyses are applied to the experimentally developed (3 % boric acid based) boron-doped geopolymer filter used for the diesel engine to assess it in a large engineering point of view. In this context, novel boron-doped filter exhaust after treatment system (BDF EAS) is compared with catalytic exhaust after treatment system (catalytic EAS) and unfiltered option (filterless) with engine loads of 50 Nm, 75 Nm and 100 Nm, while engine speeds are 1500 rpm, 1700 rpm, and 1900 rpm. The utilization of the newly developed BDF EAS has a significant effect on the exhaust emission particles. It effectively filters the particles compared to the original catalytic EAS of the engine. On the other hand, the developed BDF EAS has effective oxidation process for the emissions. So, the newly developed boron-doped filter can be used as a single device that has both of the Diesel Oxidation Catalyst (DOC) and Diesel Particulate Filter (DPF) specifications together. Hence, the new product of BDF EAS is environmentally benign system for the diesel engines and boron-doped geopolymer material can be used as an innovative material in the automotive industry's exhaust emission control system.

HYAQP: A Hybrid Meta-Heuristic Optimization Model for Air Quality Prediction Using Unsupervised Machine Learning Paradigms

In the current decade, presence of air pollution leads towards serious health conditions, including respiratory ailments, cardiovascular disorders, and lung cancer, which impacts both the lifespan and overall well-being of individuals. Moreover, the air pollution has the potential to have detrimental effects on the environment, resulting in destruction to ecosystems, decreased agricultural output and so on. Emission control systems, better fuels, stronger laws, energy efficiency improvements, and renewable energy promotion are helping industries reduce air pollution. To monitor the quality of air methods such as Particulate Matter (PM2.5), PM10, Ozone (O3), and other meteorological indicators exists. These measures pose real-time air quality however it fails to predict air quality. Predicting air quality helps reduce air pollution by enabling timely interventions and preventive measures to mitigate pollution peaks. Thus, in this research a hybrid version of optimization algorithm namely Hybrid Air Quality Prediction system (HYAQP) which is a combination of k-means clustering algorithm and meta-heuristic algorithm Sine Cosine Algorithm (SCA) is proposed. The HYAQP holds SCA integrated with k-means algorithm to find optimal cluster centroid for grouping the air data into three clusters good, poor, and moderate quality. Then the cluster which is nearer to the test instance is found and the instances present in those clusters are passed to K-Nearest Neighbor Regressor (K-NNR). Comparing HYAQP on mean absolute error it outperforms 62.9% than Multiple Linear Regression (MLR), 58.5% than Support Vector Regression (SVR), 45.5% than Vanilla-Long Short-Term Memory (Vanilla-LSTM), 44.4% than Sparrow Search Algorithm based-LSTM (SSA-LSTM) and 53.8% than K-Nearest Neighbor (KNN).

Assessment of Safety Barrier Performance in Environmentally Critical Facilities: Bridging Conventional Risk Assessment Techniques with Data-Driven Modelling

The failure of emission control systems in industrial processes undergoing emission regulations can cause severe harm to the environment. In this context, safety engineering principles can be applied to analyze process deviations and identify suitable safety barriers to mitigate harmful emissions during critical events. However, the selection, design, and assessment of proper safety barriers may be complex due to several contingencies such as the inability to perform extensive field tests on systems under strict emission regulations. In this study, an approach is proposed to couple conventional hazard identification techniques with a digital model of a flue gas treatment system to support the identification and performance assessment of safety barriers for emission control. Resilience analysis is used to evaluate the behavior of the most relevant safety barrier options, selected through a screening with conventional hazard identification tools. Barriers are simulated using the digital model of the system, gathering key information for their design and evaluation, and overcoming the limitations to field tests at the real plant. The methodology is illustrated with reference to acid gas removal in waste-to-energy facilities, a relevant example of an emission control system that is typically exposed to significant process deviations.

Research on The Ultra-Low Emission Technology in Internal Combustion Engine

Increasing the efficiency of internal combustion engines is a technologically proven and cost effective approach to dramatically improving the fuel economy of the nation’s fleet of vehicles in the near- to midterm, with the corresponding benefits of reducing our dependence on foreign oil and reducing carbon emissions. This review paper discusses on the research of ultra-low emission technology in internal combustion engine. Efficiency can be increased by improving combustion processes, minimizing engine losses such as friction, reducing the energy penalty of the emission control system and using recovered waste energy in propulsion. Compliance with exhaust emission regulations will be mandated and requires after-treatment technologies integrated with the engine combustion approaches. Fuels under consideration include hydrocarbon-based. Because of their relatively low cost, high performance, and ability to utilize renewable fuels, internal combustion engines, including those in hybrid vehicles, will continue to be critical to our transportation infrastructure for decades.

High-Temperature Behavior of Laser Electrodispersion-Prepared Pd/ZSM-5 Hydrocarbon Traps under CO Oxidation Conditions.

Zeolites and metal-doped zeolites are now widely considered as low-temperature hydrocarbon traps to be a part of emission control systems in automobiles. However, due to the high temperature of exhaust gases, the thermal stability of such sorbent materials is of great concern. To avoid the thermal instability problem, in the present work, laser electrodispersion was used to deposit Pd particles on the surface of ZSM-5 zeolite grains (SiO2/Al2O3 = 55 and SiO2/Al2O3 = 30) to obtain Pd/ZSM-5 materials with a Pd loading as low as 0.03 wt.%. The thermal stability was evaluated in a prompt thermal aging regime involving thermal treatment at temperatures up to 1000 °C in a real reaction mixture (CO, hydrocarbons, NO, an excess of O2, and balance N2) and a model mixture of the same composition with the exception of hydrocarbons. Low-temperature nitrogen adsorption and X-ray diffraction analysis were used to examine the stability of the zeolite framework. Special attention was paid to the state of Pd after thermal aging at varied temperatures. By means of transmission electron microscopy, X-ray photoelectron spectroscopy, and diffuse reflectance UV-Vis spectroscopy, it was shown that palladium, having been initially located on the surface of zeolite, undergoes oxidation and migrates into the zeolite's channels. This enhances the trapping of hydrocarbons and their subsequent oxidation at lower temperatures.

Analysis of homogeneous charge compression ignition combustion strategy and its current application

Under the pressure of energy and environmental problems, peoples demand for high-efficiency and low-pollution power sources is becoming more and more urgent. In this case, the HCCI combustion engine was developed. A new combustion method combining premixed combustion gas and low-temperature combustion was developed: it relies on a uniform formed mixture by premixed combustion gas and the lower cylinder temperature when combustion happened to reduce PM and NOX emissions simultaneously. The HCCI combustion adopts high compression ratio ignition and multi-point combustion in the cylinder, which makes its lean mixture have high thermal efficiency, and the engine performance can reach a better condition.The research and development goal of HCCI technology is to surpass compression ignition and spark ignition engines in performance and emissions. Because HCCI engine has the advantages of the first two, and its emission control system only needs to rely on its own operating characteristics and emission characteristics to reduce pollutant emissions.So if HCCI combustion can be truly mature and commercialized on a large scale, it will be a major innovation in the development history of internal combustion engines.

Effects of including a NOx storage component on a TWC when using a lean spark ignition gasoline engine combined with a passive SCR system✰

A three-way catalyst (TWC) and a TWC with a NOx storage component (NS-TWC) were evaluated on a lean spark ignition (SI) engine platform to reduce the fuel consumption and emissions of a passive selective catalytic reduction (pSCR) emission control system. The pSCR system is an approach for controlling NOx emissions from lean SI engines. It relies on onboard NH3 generation over a TWC during brief periods of fuel-rich operation. The NH3 is then stored on a downstream SCR catalyst and is available for NOx reduction during subsequent periods of lean engine operation. The NS-TWC addition enabled longer lean operation and more efficient NH3 use, which lowered fuel penalty of the pSCR system. Over a pseudo-transient drive cycle, the lean SI engine with pSCR that included NS-TWC demonstrated a 8.3% reduction in gasoline consumption over stoichiometric-only engine operation, and the NOx and non-CH4 organic gas emissions were consistent with Environmental Protection Agency (EPA) Tier 3 levels. The CO emissions, primarily from rich operation, exceeded the EPA Tier 3 levels. A cleanup catalyst (CUC) with high oxygen storage capacity was used to oxidize tailpipe CO during rich excursions by using the stored oxygen from the preceding lean operation. Although the CUC decreased CO emissions and reduced NH3 slip, some of the NH3 was converted back to NOx. Furthermore, rich CO control remains challenging. The results of this work demonstrate significant improvement in fuel consumption and emissions with a modified pSCR system architecture.

Product low‐carbon design, manufacturing, logistics, and recycling: An overview

AbstractDue to the worsening world climate crisis, reducing carbon emissions throughout product operations has become an issue that the manufacturing industry must face. In order to gain competitive advantage, this paper aims to explore low carbon design techniques for product life cycle: including low carbon design, low carbon manufacturing, low carbon logistics and low carbon recycling, as they are highly relevant to reducing carbon emissions. This paper proposes a portfolio structure for low carbon operations, consisting of a target layer, a strategy layer, and a support layer, aimed at improving energy efficiency and reducing carbon emissions. To emphasize the maximization of economic, environmental, and social advantages, the objective layer establishes a system of goals for low‐carbon product design. The strategy layer proposes four low‐carbon product design technologies: low‐carbon product design, manufacturing, transportation, and recycling. The support layer emphasizes the importance of operational systems and support platforms for low‐carbon products, such as low‐carbon design systems, energy information collection systems, energy optimization support systems, carbon emission monitoring and control systems, and low‐carbon management systems. However, successful implementation of low carbon manufacturing is challenging due to the complexity of low carbon manufacturing and the uniqueness of each company. Therefore, this paper suggests applying a life‐cycle‐oriented low‐carbon operation model to various manufacturing enterprises and exploring models that reflect actual manufacturing practices to achieve the goal of low‐carbon manufacturing.This article is categorized under: Sustainable Development > Goals

Targeted electrochemical reduction of carcinogenic N-nitrosamines from emission control systems within CO2 capture plants

N-Nitrosamines are one of the environmentally significant byproducts from aqueous amine-based post-combustion carbon capture systems (CCS) due to their potential risk to human health. Safely mitigating nitrosamines before they are emitted from these CO2 capture systems is therefore a key concern before widescale deployment of CCS can be used to address worldwide decarbonization goals. Electrochemical decomposition is one viable route to neutralize these harmful compounds. The circulating emission control waterwash system, commonly installed at the end of the flue gas treatment trains to minimize amine solvent emissions, plays an important role to capture N-nitrosamines and control their emission into the environment. The waterwash solution is the last point where these compounds can be properly neutralized before becoming an environmental hazard. In this study, the decomposition mechanisms of N-nitrosamines in a simulated CCS waterwash with residual alkanolamines was investigated using several laboratory-scale electrolyzers utilizing carbon xerogel (CX) electrodes. H-cell experiments revealed that N-nitrosamines were decomposed through a reduction reaction and are converted into their corresponding secondary amines thereby neutralizing their environmental impact. Batch-cell experiments statistically examined the kinetic models of N-nitrosamine removal by a combined adsorption and decomposition processes. The cathodic reduction of the N-nitrosamines statistically obeyed the first-order reaction model. Finally, a prototype flow-through reactor using an authentic waterwash was used to successfully target and decompose N-nitrosamines to below the detectable level without degrading the amine solvent compounds allowing them to be return to the CCS and lower the system operating costs. The developed electrolyzer was able to efficiently remove greater than 98% of N-nitrosamines from the waterwash solution without producing any additional environmentally harmful compounds and offers an effective and safe route to mitigate these compounds from CO2 capture systems.

Machine Learning-Aided Remote Monitoring of NOx Emissions from Heavy-Duty Diesel Vehicles Based on OBD Data Streams

Most of the current, popular approaches to monitoring real driving NOx emissions are based on direct measurement. However, due to the uncertainty of sensor-based measurements, such methods cannot always be used to accurately screen out the malfunctions of an emission control system. In this paper, a random forest (RF) model which extracts information from on-board diagnostics (OBD) data streams transmitted by a remote emission management vehicle terminal (REMVT) is proposed to provide a specific emission method for the online screening of high NOx emissions. First, two particular forms of modeling, random forest and logistic regression (LR), are laid out as representatives of nonparametric models and specified linear models. These two models were trained, validated and compared using OBD data collected from three China-VI heavy-duty diesel vehicles (HDDVs). The results show that as a data-driven, highly adaptive and robust learning method, the RF model can more accurately identify an abnormal emission state. Finally, a further validation was conducted, in which another China-VI HDDV was tested in two typical states, including a fault state and a normal state. The results indicated that the RF model could clearly distinguish the out-of-control emission condition from the normal operation state. The outcome of this research verifies the feasibility of using a machine learning model to process remote OBD data on HD vehicles and to identify high emissions in the case of an in-use fleet. On this basis, more sophisticated combined models and multi-stage models could be developed.