Reduction Of Cold-start Emissions Research Articles

Cold-start emission reduction of the gasoline-powered vehicle utilizing a novel method

Most vehicle tailpipe emissions are related to the cold-start condition. In the present study, a novel methodology is introduced to trap the cold-start emissions. A numerical model is used to investigate the method implementation on the vehicle’s cold-start emissions. Model is validated with the experimental data. Three different driving cycles are simulated to understand the effects of the employed method. The results show that the light-off temperature is independent of the driving cycle, while the light-off time is highly dependent on the driving behavior. The presented concept is more effective for traffic conditions and the low required powers of the vehicle. The most emission reduction is related to the emissions with moderate increment after catalyst light off. Therefore, the most considerable reduction is related to the NOx emission in all driving conditions, while method implementation is not beneficial for CO reduction compared to NOx. The emission reduction varies from 20% (WLTC) to 35% (NEDC) for CO emission, from 25% (WLTC) to 34% (NEDC and FTP75) for HC emission and 41% (FTP75) to 51% (NEDC) for NOX emission. This idea would help gasoline-powered vehicles to pass more strict emissions such as Euro7 in the coming future.

Research on the impact of new OBD diagnostic items on the emission of China 6 light-duty vehicles

The new diagnostic items such as fuel system, VVT and cold start emission reduction strategy are tested for several vehicles meeting the requirements of the China 6 emission standards of light-duty vehicles. The test results show that the fuel system fault will increase the emissions of NMHC, NOx, CO and other pollutants by 0.7-7.5 times, and the emissions of lean mixture, rich mixture and uneven cylinder to cylinder faults will increase to different degrees; VVT fault will increase NMHC and CO emissions by 1.2-2.9 times and NOx by 1.6-6.1 times; The failure of cold start emission reduction strategy will increase NMHC, NOx and CO emissions by 4.2-9.0 times and NOx by 2.1-2.2 times; It is necessary to strengthen the monitoring of these diagnostic items and tighten the requirements in the future emission standards.

Computational Modeling Predicts the Stability of Both Pd+ and Pd2+ Ion-Exchanged into H-CHA.

Passive NOx adsorbers (PNA) using Pd/zeolites have emerged as a promising solution for the reduction of cold-start emissions from vehicle exhaust. However, the nature of the active sites and the mechanisms underlying NOx adsorption in Pd/zeolites remain a subject of ongoing investigation. In this study, we employ quantum chemical simulations to investigate the structure of Pd species in cation-exchange sites at isolated Al and Al pairs in the 6-ring and 8-ring of the CHA framework, before the introduction of NOx. Our calculations show that the speciation of Pd in these exchange sites strongly depends on the precise Al arrangement within the framework, as well as the operating conditions. Ionically dispersed Pd is found to be the most favorable species over a wide range of oxidizing and reducing conditions. Small oligomers of PdO and metallic Pd do not appear to be competitive at either isolated Al or Al pairs. Notably, our calculations show that ion exchange sites other than next-next-nearest neighbor Al pairs in the 6-ring will be preferentially occupied by Pd+ instead of Pd2+. The stability of Pd+ in the zeolite environment is an interesting contrast with its rareness in molecular Pd compounds. Nonetheless, a detailed analysis of the electronic structure shows that predicted Pd oxidation states are consistent with chemical intuition for all complexes investigated in this study. We also discuss the potential ambiguity in Pd characterization provided by typical experimental techniques such as XANES, EXAFS and UV-VIS, and highlight the need for additional EPR spectroscopy studies to further elucidate the initial Pd speciation in zeolites for PNA applications.

Reduction of Cold-Start Emissions for a Micro Combined Heat and Power Plant

Decentralized power generation by combined heat and power plants becomes increasingly popular as a measure to advance the energy transition. In this context, a substantial advantage of small combined heat and power plants is based on the relatively low pollutant emissions. However, a large proportion of the pollutant emissions is produced during a cold-start. This fact is not reflected in governmental and institutional emission guidelines, as these strongly focus on the emission levels under steady-state conditions. This study analyzes the spark advance, the reference air/fuel ratio and an electrically heated catalyst in terms of their potential to reduce the cold-start emissions of a micro combined heat and power plant which uses a natural gas fueled reciprocating internal combustion engine as prime mover and a three-way catalytic converter as aftertreatment system. Based on these measures, control approaches were developed that account for the specific operating conditions of the class of small combined heat and power plants, e.g., full-load operation and flexible, demand-driven runtimes. The experimental data demonstrates that even solutions with marginal adaptation/integration effort can reduce cold-start emissions to a great extent.

Cold-Start Emission Reduction Potential and Limitations of Commercial Passive Hydrocarbon Adsorbers

Effective control of hydrocarbon (HC) emissions during cold start is critical to meeting more stringent future emission standards, and the passive HC adsorber is one possible technology to improve cold-start HC emission control. HC adsorbers for gasoline applications typically contain zeolite materials for HC storage and a noble metal-based three-way catalyst (TWC) for oxidation of stored HCs, both of which are susceptible to hydrothermal aging. In the present study, state-of-the-art HC adsorbers from two catalyst suppliers were evaluated for their cold-start HC emission reduction potential. After aging at 800 °C, the HC adsorbers tested provided reasonably high conversion efficiencies for aromatics and a moderate level of conversion for olefins but were not able to control paraffins to a significant degree. This resulted in a total HC conversion efficiency of 40–50% over the best HC adsorber for the simulated feed stream used in this study. The overall adsorber performance can be improved somewhat by increasing the noble metal loading or the O2 concentration in the feed stream and was found to be sensitive to adsorber volume (space velocity). After aging at 900 °C, however, none of the HC adsorbers tested was able to convert more than 10% of the HC in the feed.

Reduction of Cold-Start Emissions through Valve Timing in a GDI Engine

Reduction of Cold-Start Emissions through Valve Timing in a GDI Engine

Tracking Controller Design for MIMO Nonlinear Systems With Application to Automotive Cold Start Emission Reduction

The main contribution of this paper is the development of a nonlinear multiple-input, multiple-output (MIMO) tracking controller design using a discrete time sliding control approach. A Lyapunov stability analysis is used to prove the asymptotic stability of both the output errors as well as the parameter estimation errors. The application of the “New Invariance Principle” is key to the proof of the parameter error convergence. The developed approach is applied to the cold start emissions problem. The software design process for automotive powertrains on vehicles is growing increasingly complex. Verification and validation provides a systematic procedure to follow for the implementation of control algorithms on physical systems. However, errors can arise that prove costly if not mitigated early on in the verification and validation process. Therefore, the detection and mitigation of potential uncertainties early on in the design process is vital. In this work, the determination of the system model uncertainty is the focus of an adaptation algorithm designed in parallel with a discrete time, MIMO sliding controller. The unknown parameter representing the model uncertainty is updated online in order to decrease tracking error and control effort. The MIMO formulation allows for implementation of both coupled and decoupled frameworks, thus providing a basis for the algorithm to be utilized on a variety of complex vehicle systems. The control algorithms are implemented on a cold start emissions engine model as a case study. A matlab simulink environment is used for simulation results, and an engine test cell is used for experimental validation. Simulation results demonstrate that the algorithm drives tracking error to zero in a fraction of the run time and that the algorithm may be applied with equal efficacy to coupled and decoupled systems. Experimental results demonstrate the ability of the adaptation algorithm to estimate uncertainty in the engine and decrease tracking error.

Fuel reduction and electricity consumption impact of different charging scenarios for plug-in hybrid electric vehicles

Plug-in hybrid electric vehicles (PHEVs) consume both gasoline and grid electricity. The corresponding temporal energy consumption and emission trends are valuable to investigate in order to fully understand the environmental benefits. The 24-h energy consumption and emission profile depends on different vehicle designs, driving, and charging scenarios. This study assesses the potential energy impact of PHEVs by considering different charging scenarios defined by different charging power levels, locations, and charging time. The region selected for the study is the South Coast Air Basin of California. Driving behaviors are derived from the National Household Travel Survey 2009 (NHTS 2009) and vehicle parameters are based on realistic assumptions consistent with projected vehicle deployments. Results show that the reduction in petroleum consumption is significant compared to standard gasoline vehicles and the ability to operate on electricity alone is crucial to cold start emission reduction. The benefit of higher power charging on petroleum consumption is small. Delayed and average charging are better than immediate charging for home, and non-home charging increases peak grid loads.

Secondary air injection

The new emission stages, Euro 6 in Europe and SULEV /PZEV in the USA, pose severe challenges on the quality of a car engine’s combustion and exhaust aftertreatment systems. Since most of today’s systems achieve very good emission control results under hot operating conditions, the tougher challenges are presented by the reduction of cold-start emissions and the rapid heating of the exhaust aftertreatment system. The following article by Pierburg and Audi shows how secondary air assists in achieving these goals besides examining other aspects of the secondary air process.

Application of alumina supported gold-based catalysts in total oxidation of CO and light hydrocarbons mixture

Gold nanoparticles supported on alumina have been produced using the anionic exchange method and ammonia washing procedure. The catalysts are tested in the reaction of total oxidation of a mixture of light hydrocarbons and carbon monoxide in order to study the possibility of application in the reduction of cold start emissions. The obtained results are promising according to the temperature range observed for the oxidation of unsaturated hydrocarbons. The results obtained for acetylene confirms the difference of oxidation of this hydrocarbon over gold catalysts. An ageing procedure has been employed. This procedure does not affect the comportment of the catalysts versus hydrocarbon oxidation.

623 多断層型触媒装置によるコールドスタートエミッションの低減(OS5 21世紀に挑むエンジン技術)

623 多断層型触媒装置によるコールドスタートエミッションの低減(OS5 21世紀に挑むエンジン技術)

Thermal stability of metal-supported catalysts for reduction of cold-start emissions in a wood-fired domestic boiler

The aim of the present work is to develop a catalyst based on a mixture of manganese oxides and platinum supported on a metallic monolith for abatement of emissions from wood combustion, particularly during the cold-start phase. The activity and the thermal stability of the catalysts have been studied in the laboratory, before performing tests in a wood-stove. The effect of the hydrothermal treatment at 900°C on the adherence of the washcoat onto a metallic substrate was studied using scanning electronic microscope. It revealed well-adhering washcoat onto the metallic support due to the growth of the alumina whiskers during the treatment. The influence of the amount of washcoat, as well as the influence of the concentration of manganese oxides in it (Mn: 5 to 20 mol%/Al 2O 3) on the activity of fresh and hydrothermally-treated catalysts were studied. The activity tests were carried out using a mixture of carbon monoxide, naphthalene and methane in the presence of air, steam and carbon dioxide to resemble the flue gases from wood combustion. On the fresh catalysts, containing the same total amount of manganese, a high concentration of manganese oxides in the washcoat favoured the oxidation of carbon monoxide and naphthalene, whereas a lower concentration of manganese oxides in the washcoat gave higher activity for the oxidation of methane. An increased total amount of manganese oxides in the catalysts, which had the same amount of washcoat, resulted in an increase in activity for the oxidation of the three combustibles. After thermal treatment at 900°C for 270 h in steam, most of the manganese oxide catalysts were activated for the oxidation of carbon monoxide and naphthalene while only being slightly deactivated for the oxidation of methane. The addition of manganese oxides in the washcoat, however, lowers the temperature of the γ- to α-alumina phase transformation. Platinum (0.5 mol%) was added to the manganese oxide (10 mol%) catalyst to improve its activity. A platinum catalyst was also tested for comparison. The platinum and the mixed catalysts showed similar activity for the oxidation of carbon monoxide and naphthalene, while the mixed catalysts were more active for the oxidation of methane. A similarly mixed MnO x –Pt (10–0.5 mol%) catalyst supported on Al 2O 3 stabilised with 3% lanthanum, but at larger scale, was tested in a wood-stove. The possibility of pre-heating the catalyst during the start-up phase was studied. The tests revealed a strong decrease of the carbon monoxide and unburned hydrocarbons emissions during the start-up phase when the catalyst was pre-heated with hot air compared with no pre-heating or no catalyst.

Use of an Electrically Heated Catalyst to Reduce Cold-Start Emissions in a Bi-Fuel Spark Ignited Engine

Reduction of cold-start emissions using electrically-heated catalyst (EHC) technology was the focus of this work. Comprehensive emission measurements of CO, CO2,NOx, and total hydrocarbons (THC) are reported for a spark-ignited engine operated on baseline gasoline and compressed natural gas (CNG). Electric heating times of 0, 20, and 40 s with and without secondary air injection were investigated. The 40-second electric catalyst heating with secondary air injection scenario yielded the greatest catalyst system (EHC+OEM three-way catalyst) conversion efficiencies for THC, CO, and NOx for gasoline and natural gas fueling. Electric catalyst heating coupled with secondary air injection significantly improved THC and CO emissions for gasoline fueling. THC oxidation was difficult for CNG fueling due to the high content of nonreactive methane in the fuel. The independence of NOx emissions on heating time was demonstrated for all fueling cases.

A study to investigate the capability of adsorbents for reduction of cold-start emissions

Most of the emissions (about 60 per cent) from automobiles occur during a cold start before the catalytic converter becomes active. The use of an adsorbent trap for temporary storage of emitted hydrocarbons before catalysts attain the light-off temperature in the converter has been investigated as a means for reduction of cold-start emissions. The hydrocarbon emissions can be reduced significantly if the hydrocarbons are retained by the trap until catalysts reach the light-off temperature. The effect of engine speed on the emission of NO x, CO and hydrocarbons and their subsequent retention in the adsorption trap was studied. A hydrophobic adsorbent, Hisiv-1000, and molecular sieve 13X were used individually and in conjunction in the trap to adsorb hydrocarbons. Although significant amounts of hydrocarbons were adsorbed in the trap initially, they were released from the trap rather quickly even before catalysts reached the light-off temperature.