Chassis dynamometer emissions testing of 11 heavy-duty goods movement vehicles, including diesel, natural gas, and dual-fuel technology, compliant with US-EPA 2010 emissions standard were conducted. ...Results of the study show that three-way catalyst (TWC) equipped stoichiometric natural gas vehicles emit 96% lower NOx emissions as compared to selective catalytic reduction (SCR) equipped diesel vehicles. Characteristics of drayage truck vocation, represented by the near-dock and local drayage driving cycles, were linked to high NOx emissions from diesel vehicles equipped with a SCR. Exhaust gas temperatures below 250 °C, for more than 95% duration of the local and near-dock driving cycles, resulted in minimal SCR activity. The low percentage of activity SCR over the local and near-dock cycles contributed to a brake-specific NOx emissions that were 5–7 times higher than in-use certification limit. The study also illustrated the differences between emissions rate measured from chassis dynamometer testing and prediction from the EMFAC model. The results of the study emphasize the need for model inputs relative to SCR performance as a function of driving cycle and engine operation characteristics.
The aim of this study was to develop a model structure and to train a model based on chassis dynamometer datasets and subsequently use the trained model in conjunction with portable emission ...measurement system (PEMS) datasets in order to identify vehicles as possible high-NO
x
emitters. The long-short term memory (LSTM) model developed based on a single reference diesel vehicle dataset was applied to 12 diesel vehicle PEMS datasets in order to identify high-NO
x
emitters. The results showed that the vehicles that were manually identified as high emitting vehicles (i.e., control subjects) were also identified by the LSTM model to exceed real-world NO
x
emissions. Similarly, a random forest (RF) model was developed for a reference CNG vehicle and subsequently applied to 11 CNG vehicles, with a 0.2-g/bhp-hr NO
x
regulation limit, using PEMS data in order to identify any possible high NO
x
emitting vehicles. The results showed that the vehicles that were manually labeled as high emitters were also identified by the RF model to exhibit high real-world NO
x
emissions. The prediction results show that high NO
x
emitting vehicles had ratios of predicted versus measured NO
x
emissions that were lower than unity.
Experiments were conducted to characterize the particulate matter (PM)-size distribution, number concentration, and chemical composition emitted from transit buses powered by a USEPA 2010 compliant, ...stoichiometric heavy-duty natural gas engine equipped with a three-way catalyst (TWC). Results of the particle-size distribution showed a predominant nucleation mode centered close to 10 nm. PM mass in the size range of 6.04 to 25.5 nm correlated strongly with mass of lubrication-oil-derived elemental species detected in the gravimetric PM sample. Results from oil analysis indicated an elemental composition that was similar to that detected in the PM samples. The source of elemental species in the oil sample can be attributed to additives and engine wear. Chemical speciation of particulate matter (PM) showed that lubrication-oil-based additives and wear metals were a major fraction of the PM mass emitted from the buses. The results of the study indicate the possible existence of nanoparticles below 25 nm formed as a result of lubrication oil passage through the combustion chamber. Furthermore, the results of oxidative stress (OS) analysis on the PM samples indicated strong correlations with both the PM mass calculated in the nanoparticle-size bin and the mass of elemental species that can be linked to lubrication oil as the source.
The European Commission (EC) is in the process of finalizing the proposal for the upcoming legislative stage for light- and heavy-duty vehicles. The emission performance over extended operating ...conditions is under consideration. Furthermore, a tightening of the Solid Particle Number (SPN) limits with a parallel shift of the lowest detectable size from 23 to 10 nm has been suggested. This paper investigates the SPN emission performance of a Euro VI step E HDV and the potential offered by an advanced Diesel Particulate Filter (DPF) to meet the upcoming regulations. Cold start emissions at clean DPF state were found to be as high as 1.3 × 1012 #/kWh, while passive regeneration events could lead to hot start emissions of 3 × 1011 #/kWh. Improvements in the filtration efficiencies at clean state, similar to those offered by the advanced DPF (>99%), will be needed to tackle these operating conditions. The measurements also revealed the formation of 10 nm SPN in the Selective Catalytic Reduction (SCR) system, at a rate of ~1.2 × 1011 #/kWh. These levels lie above the proposed limit of 1011 #/kWh, highlighting the need to also control these non-volatile nanosized particles.
The experiments aimed at investigating the effect of real-world engine load conditions on nanoparticle emissions from a Diesel Particulate Filter and Selective Catalytic Reduction after-treatment ...system (DPF-SCR) equipped heavy-duty diesel engine. The results showed the emission of nucleation mode particles in the size range of 6–15 nm at conditions with high exhaust temperatures. A direct result of higher exhaust temperatures (over 380 °C) contributing to higher concentration of nucleation mode nanoparticles is presented in this study. The action of an SCR catalyst with urea injection was found to increase the particle number count by over an order of magnitude in comparison to DPF out particle concentrations. Engine operations resulting in exhaust temperatures below 380 °C did not contribute to significant nucleation mode nanoparticle concentrations. The study further suggests the fact that SCR-equipped engines operating within the Not-To-Exceed (NTE) zone over a critical exhaust temperature and under favorable ambient dilution conditions could contribute to high nanoparticle concentrations to the environment. Also, some of the high temperature modes resulted in DPF out accumulation mode (between 50 and 200 nm) particle concentrations an order of magnitude greater than typical background PM concentrations. This leads to the conclusion that sustained NTE operation could trigger high temperature passive regeneration which in turn would result in lower filtration efficiencies of the DPF that further contributes to the increased solid fraction of the PM number count.
This study was aimed at experimentally investigating the impact of diesel/natural gas (NG) dual-fuel retrofitting onto gaseous emissions emitted by i) legacy, model year (MY) 2005 heavy-duty engines ...with cooled EGR and no after-treatment system, and ii) a latest technology engine equipped with DPF and urea-SCR after-treatment systems that is compliant with 2010 US-EPA emissions standards. In particular, two different dual-fuel conversion kits were evaluated in this study with pure methane (CH₄) being used as surrogate for natural gas. Experiments were conducted on an engine dynamometer over a 13-mode steady-state test cycle as well as the transient FTP required for engine certification while gaseous emissions were sampled through a CVS system.
Tailpipe NOₓ emissions were observed at a comparable level for diesel and diesel/CH₄ dual-fuel operation for the 2010 compliant engine downstream the SCR. However, a reduction of ∼26% in diesel exhaust fluid (DEF) consumption was measured for dual-fuel operation, corroborating with engine-out NOₓ concentrations that were observed to be ∼32% lower as compared to diesel-only operation, indicating that the addition of natural gas significantly decreased NOₓ emissions formed during the combustion process. On the other hand, dual-fuel operation of the non after-treatment equipped, legacy engines showed conflicting NOₓ emissions results. While NOₓ emissions were observed to reduce for one of the legacy engines by ∼25%, dual-fuel operation of the second legacy engine resulted in a 6.6% increase in brake-specific NOₓ.
Carbon dioxide emissions (CO₂) were observed to decrease across all steady-state engine load modes and by 3 to 8% over the transient FTP cycle with no specific trend towards an engine technology. Methane addition to the post-2010 engine, however, resulted in the highest overall CO₂ reduction for the given amount of CH₄ injected. Additionally, this study was focusing on evaluating possible greenhouse gas benefits (i.e. tank to exhaust) from diesel/NG retrofitting as a function of engine technology. It was observed that despite the reduction in CO₂ emissions the global warming potential (GWP) benefits of dual-fuel operation were outweighed by a significant increase in methane-hydrocarbon (MHC) emissions, specifically by factors of 1.6 and 2.3-4.8 for the post-2010 and legacy engines, respectively.
The Council of State is the consultative constitutional body par excellence in the institutional architecture of the Grand Duchy of Luxembourg. It is a major actor in legislative procedure, along ...with parliament and the government. This procedure is characterised by a shuttle between the Council of State and the Chamber of Deputies and the existence of a three month suspending veto granted to the Council of State. The Council of State can be compared to a reflection chamber and its opinions can therefore have a considerable influence on the preparation and, sometimes, the content of legal standards in Luxembourg. The question regularly arises as to whether the political system of the Grand Duchy of Luxembourg does not actually turn out to be bicameral and whether the Council of State is in fact an upper chamber. In order to answer this question, it is necessary to delve into the history of the Council of State, whose roots go back well before its creation in 1856.
In comparison to legacy engine technology, natural gas vehicles have become cleaner and more efficient. Improved fueling infrastructure has supported the growth of natural gas vehicles in the ...heavy-duty sector. The heavy-duty transportation industry greatly favors the use of diesel engine technology compared to alternative fuel strategies. Local regulations and economic incentives, however, have helped to spur adoption of natural gas vehicles in certain heavy-duty vocations. Studies have shown lower distance-specific oxides of nitrogen (NOx) emissions from the stoichiometric three-way catalyst (TWC) equipped natural gas engines compared to diesel engines equipped with diesel particulate filters (DPF) and selective catalytic reduction (SCR). This review details the progress in natural gas engine technology, presents changes to emissions rate due to technology advancements, and compares natural gas engine emissions to those of modern diesel engines.
•Natural gas engines are favorable to achieve regional air quality standards, especially NOx.•Important to control fugitive methane emissions to realize low GHG emissions.•Effect of natural gas engine aging on the regulated emissions rate is seldom reported.
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