Exhaust Gas Aftertreatment Systems Research Articles

DETERMINATION OF ACOUSTIC FEATURES OF CATALYTIC CONVERTERS OF ESHAUST SYSTEMS

The object of the presented work are ceramic blocks and diesel particulate filters manufactured by CORNING and applied in the development and serial production of the exhaust gas aftertreatment systems for cars and trucks, providing the required emission standards and noise regulations. The purpose of the work is the definition of acoustic parameters of the blocks for the further use of these data in the design of the system components applying finite-element modeling. A set of the blocks with different model parameters (diameter, length, and the cell density) was tested on acoustic stand using previously developed methods. Acoustic wave parameters have been identified for each block (namely, the comprehensive speed of sound and comprehensive density). The technique of the test preparation on acoustic test bench, the methodology and results of testing, the methodology and the processing of the results are presented. The estimation of measurement and calculation of errors are presented.

Lean-Burn Natural Gas Engines: Challenges and Concepts for an Efficient Exhaust Gas Aftertreatment System

High engine efficiency, comparably low pollutant emissions, and advantageous carbon dioxide emissions make lean-burn natural gas engines an attractive alternative compared to conventional diesel or gasoline engines. However, incomplete combustion in natural gas engines results in emission of small amounts of methane, which has a strong global warming potential and consequently makes an efficient exhaust gas aftertreatment system imperative. Palladium-based catalysts are considered as most effective in low temperature methane conversion, but they suffer from inhibition by the combustion product water and from poisoning by sulfur species that are typically present in the gas stream. Rational design of the catalytic converter combined with recent advances in catalyst operation and process control, particularly short rich periods for catalyst regeneration, allow optimism that these hurdles can be overcome. The availability of a durable and highly efficient exhaust gas aftertreatment system can promote the widespread use of lean-burn natural gas engines, which could be a key step towards reducing mankind’s carbon footprint.

Review of Recent After-Treatment Technologies for De-NOx Process in Diesel Engines

The removal of nitrogen oxides (NOx), which are major atmospheric pollutants, in exhaust gas after-treatment systems, has been studied extensively. The catalytic reduction of NOx in lean-burn environments is challenging in diesel after-treatment technology. The most relevant catalytic NOx reduction technologies for diesel engines are summarized in this review paper, focusing on current catalytic after-treatment systems for compliance with emission standards. Four promising after-treatment technologies for the abatement of tail-pipe NOx emissions are discussed: (i) lean NOx trap (LNT) and LNT combined with selective catalytic reduction (SCR) (LNT + SCR), (ii) Urea/NH3-SCR, (iii) Hydrocarbon-SCR (HC-SCR), and (iv) CO/H2-SCR. The relevant reaction mechanisms and current major challenges are reviewed in detail. The effects of the active phases and support modifications of the respective catalysts are examined to evaluate their contribution to the after-treatment systems. Major issues in practical applications, such as hydrothermal aging, chemical poison, and metallic additives for improving de-NOx performance, are extensively reviewed in this paper.

An analysis of the use of cruise control in a passenger car

Most vehicles are powered by internal combustion engines. Due to the nature of their operation they emit, among others, carbon dioxide which contributes to the greenhouse effect. CO2 production is strictly correlated with fuel consumption. The article presents the results of road tests of a passenger car with a spark-ignition engine meeting the Euro 6 emission norm. The test vehicle was equipped with a classic exhaust gas aftertreatment system – a three-way catalytic converter. The aim of the study was to verify the impact of the cruise control use on the vehicle fuel consumption. The measurements were based on Portable Emission Measurement System type mobile equipment for exhaust emission tests. The tests were carried out in real driving conditions travelling on an express way. Test drives took place on a route with variable topographic profile. Three test drives with different speeds were carried out, but the aim was to obtain an average speed of 130 km/h.

Multi-gas sensor to detect simultaneously nitrogen oxides and oxygen

Abstract. Due to tightened emission limits, the efficiency of exhaust gas aftertreatment systems has to be further enhanced. Therefore, inexpensive and robust NOx sensors are required to be installed not only in automotive exhausts, but also in any other kind of combustion-based application. In this contribution, an impedimetric NOx sensor is presented. The impedance of a functional thick film (KMnO4, manufactured in a screen-printing technique on planar alumina substrates) depends selectively on the NOx concentration in the exhaust but shows a dependency on the oxygen concentration. Therefore, an additional temperature-independent resistive oxygen sensor structure was integrated on the same sensor platform. BFAT (BaFe0.74Al0.01Ta0.25O3−δ (BaFe0.74Al0.01Ta0.25O3−δ) was used for this purpose, and the measurement was conducted in the dc resistance mode. It serves not only to determine the oxygen concentration in the exhaust, but also to correct the oxygen dependency of the NOx sensor.

Experimental Investigation to Analyze the Effects of Oil Dilution on Unintended Acceleration in a Diesel Engine

Due to the gradual reinforcement of emission regulations, exhaust gas after-treatment systems have become more complicated, and various engine control algorithms have been applied to diesel engines. However, the misuse of advanced exhaust gas after-treatment systems could cause additional problems. For instance, diesel vehicles that use of a diesel particulate filter (DPF) generally require periodic active regeneration. While operating active regeneration by in-cylinder post-injection, the fuel impinging on the cylinder wall would become the cause of oil dilution. Furthermore, if, in the event of excessive oil dilution, engine oil overflows in the engine oil pan, engine stalling or unintended acceleration (engine over-run) can occur, as lube oil flows into the combustion chamber through the intake manifold. The present study tested engine overrun by overflowing engine oil diluted with fuel on various engine operating conditions and clarify the engine control factors effect on engine stalling or unintended acceleration using regression analysis. Vehicle tests based on engine test analysis were also conducted to evaluate and reproduce the influence of unintended acceleration by automotive lube oil backflow in real driving. Vehicle test results indicate that unintentional acceleration could occur due to oil dilution, which put the driver at risk.

Field tests and real-world exhaust gas emissions of a pure rapeseed oil-fuelled harvester in forestry: Testing a solution for combined water, soil, and climate protection

Using pure rapeseed oil fuel (R100) in forest machinery could be a measure that contributes to climate, water, and soil protection in forestry. However, forest machinery that is compatible with R100 is not currently available. The target of this research was to operate forest machinery with R100 in a field-test, to collect and evaluate the operational and real-world emission behaviour and to assess the environmental impact. Therefore, a modern forest harvester was modified to operate with R100 and was monitored from August 2017 until December 2018, under Bavarian working conditions. The behaviour during 2100 h of operation was mainly evaluated using information on productivity and operating fluid consumption compared to diesel fuel operation before the modifications were made. Compared to diesel fuel operation, no significant differences in the productivity of the harvester and the energy efficiency of the engine could be detected. With the fuel tempering system installed, the engine could be started at an ambient temperature as low as −20 °C. The results of the engine oil analysis and technical engine inspection after the field test indicate a failure-free operation of the engine and exhaust gas after-treatment system. Furthermore, a functional diagnosis of the harvester indicates that all of the additionally installed components were functioning and the engine, as well as the exhaust gas after-treatment system, were in an appropriate condition. The real driving emissions of nitrogen oxides, hydrocarbons, and carbon monoxide were measured at the beginning of and close to the end of the field test and compared to that of the harvester operating with diesel fuel. Statistical analysis showed no significant influence of the fuel type or the operation time with R100 on the emission behaviour. The emission results were well below the legal requirements for engine test stand measurements. Within the lifetime of the harvester it can be estimated that a turnover of 350,000 L of diesel fuel and 700 to 1050 tonnes of greenhouse gas emissions can be avoided. For the first time, the results indicate that it is technically possible to operate a modern forest harvester with R100 (even during hard winter conditions), and this is in compliance with emission requirements and can contribute to climate, soil, and water protection.

Evaluation of pure rapeseed oil as a renewable fuel for agricultural machinery based on emission characteristics and long-term operation behaviour of a fleet of 18 tractors

The usage of locally produced pure rapeseed oil fuel (R100) according to fuel standard DIN 51605 in agricultural machinery can contribute to protecting the climate, water, and soil. Besides economic aspects, uncertainties concerning the long-term operation reliability and limited exhaust emissions of R100-operated agricultural machinery are hindering market entry. Thus, the aim of this research is to evaluate field experiences, such as downtimes and repairs, engine oil quality, and cold start behaviour, over a total period of more than 50,000 operation hours with 18 tractors. The tested tractors range from European Union exhaust gas stages I to IV and were configured for the use of R100. Additionally, performance, nitrogen oxides, and particulate matter were measured on a tractor test stand. The tractors demonstrated their full functionality under usual Bavarian farm conditions in daily use. Within the tractor fleet, no serious engine damage was observed, while minor malfunctions and necessary repairs occurred just occasionally. The operational reliability of the tested rapeseed-oil-fuelled tractors seemed to be comparable to that of diesel-fuelled tractors. The results of recurrent power and fuel consumption measurements gave no indication of engine deterioration. Furthermore, measurements proved that differences in exhaust gas emissions between R100 and diesel operation were marginal. Tractor models with exhaust gas after treatment systems were characterized by low emissions of nitrogen oxides and particulate matter in particular. With the 18 tractors running on R100, about 220 tonnes of CO2eq per year were saved on average from 2015 to 2017. It can be concluded that the usage of pure rapeseed oil fuel (R100) in compatible agricultural machinery is an implementable alternative to diesel fuel and can make an important contribution to reducing greenhouse gas emissions in agriculture. Nevertheless, there are some challenges to solve, particularly for modern agricultural machines with engines with exhaust gas aftertreatment systems.

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.

Statistically supported real driving emission calibration: Using cycle generation to provide vehicle-specific and statistically representative test scenarios for Euro 7

The progression of emission legislation has intensified the efforts of the automotive industry to develop improved exhaust gas after-treatment systems. The requirement to fulfill Euro 6d-TEMP in real-world driving scenarios, the already significant calibration effort for Euro 6d and the Euro 7 emission standards in discussion have significantly increased the work load for calibration engineers and the requirements for testing resources. Many original equipment manufacturers are implementing taskforces in order not to have to discard the planned start of production for their products, and some are even already forced to reduce their product portfolio. This is due to the diverse testing matrix required to cover all possible real driving emissions test scenarios. One big challenge is the extension and possible variation of boundary conditions regarding ambient temperatures, traffic conditions, road gradients and other varying driving resistances. Moreover, the test duration can cause considerable differences in the measured emissions, even if the same route is driven repeatedly. Addressing these challenges makes the application of a dedicated, event-targeted emission calibration mandatory. Since only a few sequences of the time-consuming road tests are relevant for improving the emission calibration, the methodology presented in this article focuses on the exact reproduction of these emission events on an emission chassis dynamometer with the aim of implementing calibratable solutions for these events. This is done using a real driving emission-cycle-generator which creates real driving emission compliant severe test scenarios and which focuses on the statistical relevance related to the typical product specific operation. The underlying generation process accesses a large database with real driving emission measurement results focusing on vehicle- or vehicle-group-specific challenges, using statistical approaches. It will be demonstrated how this procedure reduces test time and how it helps to tackle the substantial real driving emission work-load, while providing a dependable base to achieve real driving emission legislation compliance.

Emission of Toxic HCN During NOx Removal by Ammonia SCR in the Exhaust of Lean-Burn Natural Gas Engines.

Reducing greenhouse gas and pollutant emissions is one of the most stringent priorities of our society to minimize their dramatic effects on health and environment. Natural gas (NG) engines, in particular at lean conditions, emit less CO2 in comparison to combustion engines operated with liquid fuels but NG engines still require emission control devices for NOx removal. Using state‐of‐the‐art technologies for selective catalytic reduction (SCR) of NOx with NH3, we evaluated the interplay of the reducing agent NH3 and formaldehyde, which is always present in the exhaust of NG engines. Our results show that a significant amount of highly toxic hydrogen cyanide (HCN) is formed. All catalysts tested partially convert formaldehyde to HCOOH and CO. Additionally, they form secondary emissions of HCN due to catalytic reactions of formaldehyde and its oxidation intermediates with NH3. With the present components of the exhaust gas aftertreatment system the HCN emissions are not efficiently converted to non‐polluting gases. The development of more advanced catalyst formulations with improved oxidation activity is mandatory to solve this novel critical issue.

Effect of pressure boost on the diesel performance and gaseous emission with fuel spray pressure up to 3000 bar

The study presents the results of a single-cylinder engine modeling that assesses the effect of turbochargers on diesel performance and gaseous emission with the fuel injection pressure up to 3000 bar. 3D modeling is performed in Fire ESE Diesel. The results show that indicator power, soot, HC increase, and BSFC, NOx decrease when using turbochargers. The boost pressure increases from 1 to 3.5 bar, the indicator power and BSFC vary tremendous, while the boost pressure increases from 3.5 to 4.5 bar, the indicator power, and BSFC change slowly. Indicator power grows by 15 %, BSFC reduces 16.6 %, NOx value goes down by 85 % and soot value goes up by 92.9 %, the maximum value of HC goes up by 51.6 % with a boost pressure of 4.5 bar and SOI at 17° BTDC. When the SOI falls, BSFC reduces and the maximum value of this reduction is 6.4 %, while indicator power increases by 5.6 % with the boost pressure of 3.5 bar. NOx value goes down by 70.3 % and soot value goes up by 88.6 % with the boost pressure of 4.5 bar. With the SOI of 5° BTDC, the turbocharging pressure from 2.5 to 4.5 bar, gaseous emissions meet the EURO V standard without the use of exhaust gas after-treatment systems.

ABOUT THE IMPLEMENTATION OF THE NATIONAL SYSTEM OF LABELING OF ROAD VEHICLES REGARDING LEVEL OF ENVIRONMENTAL HAZARD

Key aspects, problematic issues, and the proposals for implementation of possible variant of an efficient system of labeling of road vehicles regarding an actual level of environmental hazard (LEH) in the unified system of coordinates are considered. It is taking into account vehicle age, technical condition and other factors, and based on available data on vehicle`s design and indicators, defined not only by the standards of the European Union (environmental standards “Euro”) but also by the standards of other regions of the world, in particular, the North American market. The proposed system can serve as a fundamental element in promoting the development of international trade and improving the quality of vehicle fleet upgrades in Ukraine, reducing the tax burden on citizens during the acquisition of vehicles (which makes it possible to invest in more modern and environmentally friendly vehicles), due to the introduction in Ukraine, similarly with the practice of EU Member States, of a differentiated and fair fiscal policy using the “polluter pays” principle, and other instruments to encourage the use of more environmentally friendly vehicles, differentiated restrictions and preferences for access to infrastructure, including the establishment by local communities of a flexible system of differentiated ecological zones for transport. The proposed universal, convenient and efficient LEH system, and appropriate labeling of vehicles of all major categories, will also stimulate the creation of a system of restoration of the ecological properties of vehicles in the country by the planned replacement of the replacement elements of the exhaust gas after-treatment systems, stimulate the “retrofitting” with the improvement of the ecological properties vehicles being in operation, and include in the same system both “traditional” internal combustion engines and technology of electric vehicles as well. Keywords: road vehicles, adduced pollutant`s emissions, labeling of environmental hazard (LEH).

Modeling the combustion of volatile organic compound (VOC) ethane in monolithic catalytic converter

Air pollution a potential environmental problem is caused mostly by the burning of fuels both in the transport sectors and industrial sectors. Motor vehicles are one of the significant growing air pollution contributors who produce a considerable amount of volatile organic compounds (VOCs) and other pollutants. The rising concern about the environmental effect of the exhaust emission pollutants has led to the need for the development of progressively efficient catalytic converters and exhaust gas after-treatment systems. Mathematical modeling is an essential way to understand the processes occurring in the catalytic converter, and it plays a critical part in improving and designing the existing models. A mathematical model has been formed for both non-catalytic and catalytic reactions based on mass and heat transfer for the oxidation of VOC ethane. Modeling equations have been solved with an implicit scheme, and numerical calculations have carried out using Matlab software. The results have been compared, obtained from the two reactions mechanisms.

Combined near-ambient pressure photoelectron spectroscopy and temporal analysis of products study of CH4 oxidation on Pd/γ-Al2O3 catalysts

Vehicles that run on natural gas must be equipped with an exhaust gas after-treatment system to burn their unavoidable CH4 slip, which must not be released into the environment as CH4 is a potent greenhouse gas. Pd is known as a highly active catalyst material for CH4 oxidation. For this study, Pd was deposited on a γ-Al2O3 support and the as-received samples were pre-reduced and pre-oxidized, respectively. Near-Ambient Pressure Photoelectron Spectroscopy and the Temporal Analysis of Products methodology were combined to understand that both electronic states, namely PdO and Pd°, are active for the CH4 oxidation reaction, whereby the superior activity of the pre-reduced Pd/γ-Al2O3 catalyst was ascribed to the spill-over of OH-groups from the support to Pd. It was found that the reaction products, CO, CO2 and H2, were strongly and, to a large extent, adsorbed on the catalyst surface and were involved in reversible chemical interactions on the catalyst surface during the CH4 oxidation reaction on the Pd/γ-Al2O3 catalyst.

Late Fuel Post-Injection Influence on the Dynamics and Efficiency of Wall-Flow Particulate Filters Regeneration

Late fuel post-injections are the most usual strategy to reach high exhaust temperature for the active regeneration of diesel particulate filters. However, it is important to optimise these strategies in order to mitigate their negative effect on the engine fuel consumption. This work aims at understanding the influence of the post-injection parameters, such as its start of injection and its fuel quantity, on the duration of the regeneration event and the fuel consumption along it. For this purpose, a set of computational models are employed to figure out in a holistic way the involved phenomena in the interaction between the engine and the exhaust gas aftertreatment system. Firstly, an engine model is implemented to evaluate the effect of the late fuel post-injection pattern on the gas properties at the exhaust aftertreatment system inlet in different steady-state operating conditions. These are selected to provide representative boundary conditions of the exhaust gas flow concerning dwell time, exhaust temperature and O 2 concentration. In this way, the results are later applied to the analysis of the diesel oxidation catalyst and wall-flow particulate filter responses. The dependence of the diesel particulate filter (DPF) inlet temperature is discussed based on the efficiency of each post-injection strategy to increase the exhaust gas temperature. Next, the influence on the dynamics of the regeneration of the post-injection parameters through the change in gas temperature and O 2 concentration is finally studied distinguishing the pre-heating, maximum reactivity and late soot oxidation stages as well as the required fuel consumption to complete the regeneration process.

Hydrogen Production via the Catalytic Partial Oxidation of Ethanol on a Platinum–Rhodium Catalyst: Effect of the Oxygen-to-Ethanol Molar Ratio and the Addition of Steam

To produce hydrogen for automotive exhaust gas aftertreatment systems, the catalytic partial oxidation of ethanol over a platinum–rhodium catalyst supported on alumina is examined via experimental ...

Decomposition of Al2O3-Supported PdSO4 and Al2(SO4)3 in the Regeneration of Methane Combustion Catalyst: A Model Catalyst Study

Exhaust gas aftertreatment systems play a key role in controlling transportation greenhouse gas emissions. Modern aftertreatment systems, often based on Pd metal supported on aluminum oxide, provide high catalytic activity but are vulnerable to sulfur poisoning due to formation of inactive sulfate species. This paper focuses on regeneration of Pd-based catalyst via the decomposition of alumina-supported aluminum and palladium sulfates existing both individually and in combination. Decomposition experiments were carried out under hydrogen (10% H2/Ar), helium (He), low oxygen (0.1% O2/He), and excess oxygen (10% O2/He). The structure and composition of the model catalysts were examined before and after the decomposition reactions via powder X-ray diffraction and elemental sulfur analysis. The study revealed that individual alumina-supported aluminum sulfate decomposed at a higher temperature compared to individual alumina-supported palladium sulfate. The simultaneous presence of aluminum and palladium sulfates on the alumina support decreased their decomposition temperatures and led to a higher amount of metallic palladium than in the corresponding case of individual supported palladium sulfate. From a fundamental point of view, the lowest decomposition temperature was achieved in the presence of hydrogen gas, which is the optimal decomposition atmosphere among the studied conditions. In summary, aluminum sulfate has a two-fold role in the regeneration of a catalyst—it decreases the Pd sulfate decomposition temperature and hinders re-oxidation of less-active metallic palladium to active palladium oxide.

Fundamentals of Sulfate Species in Methane Combustion Catalyst Operation and Regeneration—A Simulated Exhaust Gas Study

Emission regulations and legislation inside the European Union (EU) have a target to reduce tailpipe emissions in the transportation sector. Exhaust gas aftertreatment systems play a key role in low emission vehicles, particularly when natural gas or bio-methane is used as the fuel. The main question for methane operating vehicles is the durability of the palladium-rich aftertreatment system. To improve the durability of the catalysts, a regeneration method involving an efficient removal of sulfur species needs to be developed and implemented on the vehicle. This paper tackles the topic and its issues from a fundamental point of view. This study showed that Al2(SO4)3 over Al2O3 support material inhibits re-oxidation of Pd to PdO, and thus hinders the formation of the low-temperature active phase, PdOx. The presence of Al2(SO4)3 increases light-off temperature, which may be due to a blocking of active sites. Overall, this study showed that research should also focus on support material development, not only active phase inspection. An active catalyst can always be developed, but the catalyst should have the ability to be regenerated.

Smart rule-based diesel engine control strategies by means of predictive driving information

The increasing connectivity of future vehicles allows the prediction of the powertrain operational profiles. This technology will improve the transient control of the engine and its exhaust gas aftertreatment systems. This article describes the development of a rule-based algorithm for the air path control, which uses the knowledge of upcoming driving events to reduce especially [Formula: see text] and particulate (soot) emissions. In the first section of this article, the boosting and the lean [Formula: see text] trap systems of a diesel powertrain are investigated as relevant sub-systems for shorter prediction horizons, suitable for Car-to-X communication range. Reference control strategies, based on state-of-the-art engine control unit algorithms and suitable predictive control logics, are compared for the two sub-systems in a model in the loop simulation environment. The simulation driving cycles are based on Worldwide harmonized Light-duty Test Cycle and Real Driving Emissions regulations. Due to the shorter, and consequently more probable, prediction horizon and the demonstrated emission improvements, a dedicated rule-based algorithm for the air path control is developed and benchmarked in the Worldwide harmonized Light-duty Test Cycle as described in the second part of this article. Worldwide harmonized Light-duty Test Cycle test results show an improvement potential for engine-out soot and [Formula: see text] emissions of up to 5.2% and 1.2%, respectively, for the air path case and a reduction of the average fuel consumption in Real Driving Emissions of up to 1% for the lean NOx trap case. In addition, the developed rule-based algorithm allows the adjustment of the desired NOx–soot trade-off, while keeping the fuel consumption constant. The study concludes with brief recommendations for future research directions, as for example, the introduction of a prediction module for the estimation of the vehicle operational profile in the prediction horizon.