Study on Cold Start Influence Factors of Three Way Catalytic Converter

2013 ◽  
Vol 385-386 ◽  
pp. 172-175
Author(s):  
Hao Cai ◽  
Li Ping Yu ◽  
Jin Ke Gong ◽  
Yu He Geng ◽  
Ya Fei Liu
Keyword(s):  
Numerical Simulation ◽  
Ambient Temperature ◽  
Gas Phase ◽  
Catalytic Converter ◽  
Influence Factors ◽  
Cold Start ◽  
Gas Phase Reactions ◽  
Reactor Model ◽  
Exhaust Temperature ◽  
The Impact

This article has established a three-way catalytic converter reactor model of gas phase reactions and surface reactions. Based on this model, cold start transient emission numerical simulation has been done. The result shows that the influence of ambient temperature and exhaust temperature on the HC is much greater than the impact on the CO.

scholarly journals Testing and evaluation of cold-start emissions from a gasoline engine in RDE test at two different ambient temperatures

2021 ◽  
Vol 11 (1) ◽  
pp. 425-434
Author(s):  
Jacek Pielecha ◽  
Kinga Skobiej ◽  
Karolina Kurtyka
Keyword(s):  
Ambient Temperature ◽  
Gasoline Engine ◽  
Cold Start ◽  
Exhaust Emissions ◽  
Operating Parameters ◽  
Time Interval ◽  
Vehicle Speed ◽  
Passenger Cars ◽  
Ambient Temperatures ◽  
The Impact

Abstract In order to better reflect the actual ecological performance of vehicles in traffic conditions, both the emission standards and the applied emission tests are being developed, for example by considering exhaust emissions for a cold engine start. This article presents the research results on the impact of ambient temperature during the cold start of a gasoline engine in road emission tests. The Real Driving Emissions (RDE) tests apply to passenger cars that meet the Euro 6 emissions norm and they are complementary to their type approval tests. A portable emissions measurement system was used to record the engine and vehicle operating parameters, as well as to measure the exhaust emissions during tests. This allowed for parameters such as engine load, engine speed and vehicle speed to be monitored. The cold start conditions for two different temperatures (8°C and 25°C) were compared in detail. Moreover, the engine operating parameters, exhaust concentration values and road emissions for the 300 s time interval, were compared. The summary of the article presents the share of a passenger car’s cold start phase for each exhaust compound in the urban part of the test and in the entire Real Driving Emissions test depending on the ambient temperature.

scholarly journals The role of atom tunneling in gas-phase reactions in planet-forming disks

2019 ◽  
Vol 627 ◽  
pp. A45 ◽  
Author(s):  
J. Meisner ◽  
I. Kamp ◽  
W.-F. Thi ◽  
J. Kästner
Keyword(s):  
Gas Phase ◽  
Rate Constants ◽  
Reaction Rate ◽  
Tunneling Effect ◽  
Gas Phase Reactions ◽  
Disk Model ◽  
Reaction Rate Constants ◽  
T Tauri ◽  
Simple Molecules ◽  
The Impact

Context. Chemical Gas-phase reactions of simple molecules have been recently revised to include atom tunneling at very low temperatures. This paper investigates the impact of the increased reaction rate constant due to tunneling effects on planet-forming disks. Aims. Our aim is to quantify the astrophysical implications of atom tunneling for simple molecules that are frequently used to infer disk structure information or to define the initial conditions for planet (atmosphere) formation. Methods. We quantify the tunneling effect on reaction rate constants by using H2 + OH → H2O + H as a scholarly example in comparison to previous UMIST2012 rate constants. In a chemical network with 1299 reactions, we identify all chemical reactions that could show tunneling effects. We devise a simple formulation of reaction rate constants that overestimates tunneling and screen a standard T Tauri disk model for changes in species abundances. For those reactions found to be relevant, we find values of the most recent literature for the rate constants including tunneling and compare the resulting disk chemistry to the standard disk model(s), a T Tauri and a Herbig disk. Results. The rate constants in the UMIST2012 database in many cases already capture tunneling effects implicitly, as seen in the curvature of the Arrhenius plots of some reactions at low temperature. A rigorous screening procedure identified three neutral-neutral reactions where atom tunneling could change simple molecule abundances. However, by adopting recent values of the rate constants of these reactions and due to the layered structure of planet-forming disks, the effects are limited to a small region between the ion-molecule dominated regime and the ice reservoirs where cold (<250 K) neutral-neutral chemistry dominates. Abundances of water close to the midplane snowline can increase by a factor of two at most compared to previous results with UMIST2012 rates. Observables from the disk surface, such as high excitation (>500 K) water line fluxes, decrease by 60% at most when tunneling effects are explicitly excluded. On the other hand, disk midplane quantities relevant for planet formation such as the C-to-O ratio and also the ice-to-rock ratio are clearly affected by these gas-phase tunneling effects.

Direct Numerical Simulation of Turbulent Heat Transfer Across a Mobile, Sheared Gas-Liquid Interface

2003 ◽  
Vol 125 (6) ◽  
pp. 1129-1139 ◽  
Author(s):  
D. Lakehal ◽  
M. Fulgosi ◽  
G. Yadigaroglu ◽  
S. Banerjee
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Gas Phase ◽  
Liquid Interface ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Flow Data ◽  
Prandtl Numbers ◽  
The Impact

The impact of interfacial dynamics on turbulent heat transfer at a deformable, sheared gas-liquid interface is studied using Direct Numerical Simulation (DNS). The flow system comprises a gas and a liquid phase flowing in opposite directions. The governing equations for the two fluids are alternately solved in separate domains and then coupled at the interface by imposing continuity of velocity and stress. The deformations of the interface fall in the range of capillary waves of waveslope ak=0.01 (wave amplitude a times wavenumber k), and very small phase speed-to-friction velocity ratio, c/u*. The influence of low-to-moderate molecular Prandtl numbers Pr on the transport in the immediate vicinity of the interface is examined for the gas phase, and results are compared to existing wall-bounded flow data. The shear-based Reynolds number Re* is 171 and Prandtl numbers of 1, 5, and 10 were studied. The effects induced by changes in Pr in both wall-bounded flow and over a gas-liquid interface were analyzed by comparing the relevant statistical flow properties, including the budgets for the temperature variance and the turbulent heat fluxes. Overall, Pr was found to affect the results in very much the same way as in most of the available wall flow data. The intensity of the averaged normal heat flux at high Prandtl numbers is found to be slightly greater near the interface than at the wall. Similar to what is observed in wall flows, for Pr=1 the turbulent viscosity and diffusivity are found to asymptote with z+3, where z+ is the distance to the interface, and with z+n, where n>3 for Pr=5 and 10. This implies that the gas phase perceives deformable interfaces as impermeable walls for small amplitude waves with wavelengths much larger than the diffusive sublayers. Moreover, high-frequency fluctuating fields are shown to play a minor role in transferring heat across the interface, with a marked filtering effect of Pr. A new scaling law for the normalized heat transfer coefficient, K+ has been derived with the help of the DNS data. This law, which could be used in the range of Pr=1 to 10 for similar flow conditions, suggests an approximate Pr−3/5 relationship, lying between the Pr−1/2 dependence for free surfaces and the Pr−2/3 law for immobile interfaces and much higher Prandtl numbers. A close inspection of the transfer rates reveals a strong and consistent relationship between K+, the frequency of sweeps impacting the interface, the interfacial velocity streaks, and the interfacial shear stress.

scholarly journals Numerical Analysis of an Impinging Jet Reactor for the CVD and Gas-Phase Nucleation of Titania

1993 ◽  
Vol 335 ◽  
Author(s):  
Suleyman A. Gokoglu ◽  
G. D. Stewart ◽  
J. Collins ◽  
D. E. Rosner
Keyword(s):  
Gas Phase ◽  
Impinging Jet ◽  
Gas Phase Reactions ◽  
Reactor Model ◽  
Deposition Rates ◽  
Numerical Predictions ◽  
Model Predictions ◽  
Phase Nucleation ◽  
Chemically Reacting ◽  
The Mathematical Model

AbstractWe model a cold-wall atmospheric pressure impinging jet reactor to study the CVD and gas-phase nucleation of TiO2 from a titanium tetra-iso-propoxide (TTIP)/oxygen dilute source gas mixture in nitrogen. The mathematical model uses the computational code FIDAP and complements our recent asymptotic theory for high activation energy gas-phase reactions in thin chemically reacting sublayers. The numerical predictions highlight deviations from ideality in various regions inside the experimental reactor. Model predictions of deposition rates and the onset of gas-phase nucleation compare favorably with experiments. Although variable property effects on deposition rates are not significant (∼11% at 1000K), the reduction of rates due to Soret transport is substantial (∼75% at 1000K).

Impact of Gas-Phase Reactions on SOFC Systems Operating on Diesel and Biomass-Derived Fuels

2010 ◽  
Vol 638-642 ◽  
pp. 1118-1124 ◽  
Author(s):  
In Yong Kang ◽  
Hans Heinrich Carstensen ◽  
Anthony M. Dean
Keyword(s):  
Gas Phase ◽  
Diesel Fuel ◽  
Gas Phase Reactions ◽  
Deposit Formation ◽  
Olefin Production ◽  
Detailed Kinetic Model ◽  
Fuel Mixing ◽  
Gas Reactions ◽  
The Impact ◽  
Fuel Fraction

The use of diesel fuel to power a solid oxide fuel cell (SOFC) presents several challenges. A major issue is deposit formation in either the external reformer, the anode channel, or within the SOFC anode itself. These deposits are generally poly-aromatic hydrocarbons (PAHs) produced either by gas-phase pyrolysis of the fuel or by catalytic reactions. In this report we describe n-hexane and ethylene pyrolysis experiments under conditions relevant to reformer or SOFC operation (τ=~1s, T=550~900°C, P~0.8 atm) to explore the potential for gas-phase reactions to produce deposit precursors. N-hexane is very reactive under these conditions and forms significant amounts of olefins (mainly ethylene) which can lead to deposits. The ethylene experiments also demonstrated that higher molecular weight species (deposit precursors) are rapidly formed. Under autothermal reforming conditions, such pyrolytic reactions are possible upstream of the catalyst bed if the fuel, air, and steam streams are not fully mixed. If part of the fuel does not mix with the oxidizer it will simply pyrolyze. At the same time, the remaining fuel fraction mixes with the entire oxidant inlet and thus creates higher local oxidant to fuel ratios than expected. Reaction of this leaner mixture can lead to temperature overshoots as more CO2 is formed. We have used a validated detailed kinetic model for ethane to explore the impact of incomplete fuel mixing on reforming performance. If only half the fuel mixes with the oxidants, this approach predicts formation of ethylene in the pyrolysis zone and excess CO2 with associated very high temperatures in the oxidation zone. This case could result in both excessive deposit formation as well as potential thermal damage to the downstream catalyst. On the other hand, assuming perfect fuel mixing under exothermic ATR conditions (τ=~1s, Ti=800°C, S/C=1.25, O/C=1.4), the gas phase reactions alone are sufficient to drive the system to equilibrium (no olefins or methane formed) due to the substantial increase in temperature. These results demonstrate the necessity for complete mixing of the fuel stream with the oxidant streams to limit both olefin production (and subsequent deposit formation) as well as the temperature overshoots. The model predictions for ethane as fuel suggest that the temperature should be kept below 500oC and the residence time in the mixing region should be minimized to avoid these undesired gas reactions. Since actual diesel fuel is expected to be even more reactive than ethane, the impact of gas-phase reactions is expected to be even greater than predicted in this study.

Ignition Stability Improvement and Emission Reduction via Multiple Ignition Sites Strategy Under Cold Start and Transient Conditions

2021 ◽  
Author(s):  
Xiaoxi Zhang ◽  
Xiao Yu ◽  
Simon Leblanc ◽  
Ming Zheng ◽  
Jimi Tjong
Keyword(s):  
Catalytic Converter ◽  
Cold Start ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Lean Burn ◽  
Engine Operation ◽  
Warm Up ◽  
Spark Timing ◽  
Engine Stability ◽  
The Impact

Abstract Downsizing, turbocharging, and lean burn strategies offer improved fuel efficiency and engine-out emissions to that of conventional spark ignition engines. However, maintaining engine stability becomes difficult, especially at low load and low speed operation such as cold start conditions. Under cold start operation, the spark timing is retarded to rush catalyst warm-up temperature followed by advancing the spark timing for engine stability. In this sequence, securing ignition while using retarded spark timing is difficult because of the cold cylinder walls and low engine loads. Through previous investigations, the noval multiple ignition sites strategy demonstrated its capability to expend lean burn boundaries beyond traditional single core spark plug and improve cycle to cycle variation. In this work, multisite ignition is tested on a production 4-cylinder direct injection spark ignition engine. A large number of tests are performed on the engine to investigate the impact of ignition strategy on emissions and stability during catalytic converter warm up period as part of the cold-start operation. Results show that the three-core spark igniter shortens the ignition delay thus providing a wider stable spark timing window for stable engine operation. As a result, the concentration of unburnt fuel in the exhaust gas can be reduced before the catalyst reaches the light-off temperature.

scholarly journals Cold start emissions of passenger cars with gasoline and diesel engines in Real Driving Emissions tests

2019 ◽  
Vol 179 (4) ◽  
pp. 160-168 ◽  
Author(s):  
Jacek PIELECHA ◽  
Jerzy MERKISZ ◽  
Karolina KURTYKA ◽  
Kinga SKOBIEJ
Keyword(s):  
Ambient Temperature ◽  
Diesel Engines ◽  
Test Procedure ◽  
Cold Start ◽  
Exhaust Emissions ◽  
Exhaust Emission ◽  
Passenger Cars ◽  
Compression Ignition Engines ◽  
Vehicle Operation ◽  
The Impact

Modernization of passenger cars and constant development of existing legislation lead to a reduction of exhaust emissions from these vehicles. In accordance with package 3 of the RDE test procedure, the European Commission has extended testing methods by including exhaust emissions during a cold start. The article compares the research results on the impact of ambient temperature during the cold start of spark-ignition and compression-ignition engines in road emission tests. The tests were carried out in line with the requirements of the RDE test procedure for passenger cars meeting the Euro 6d-Temp emissions standard. The obtained results were analyzed, i.e. there were compared the engine and vehicle operation parameters and the values of road exhaust emissions, during the cold start of gasoline and diesel engines at the ambient temperature of approximately 25oC.The summary presents the share of cold start phase of a passenger car (at the ambient temperature of around 25oC) for each exhaust emission compound in the urban part of the test, and in the entire RDE test, depending on the engine type used.

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