Controlling automotive exhaust emissions: successes and underlying science

2005 ◽  
Vol 363 (1829) ◽  
pp. 1013-1033 ◽  
Author(s):  
Martyn V Twigg
Keyword(s):  
Carbon Monoxide ◽  
Nitrogen Oxides ◽  
Diesel Engines ◽  
Gasoline Engine ◽  
Photochemical Reactions ◽  
Exhaust Gas ◽  
Gas Temperature ◽  
Vehicle Exhaust ◽  
Lean Burn ◽  
Three Way Catalyst

Photochemical reactions of vehicle exhaust pollutants were responsible for photochemical smog in many cities during the 1960s and 1970s. Engine improvements helped, but additional measures were needed to achieve legislated emissions levels. First oxidation catalysts lowered hydrocarbon and carbon monoxide, and later nitrogen oxides were reduced to nitrogen in a two-stage process. By the 1980s, exhaust gas could be kept stoichiometric and hydrocarbons, carbon monoxide and nitrogen oxides were simultaneously converted over a single ‘three-way catalyst’. Today, advanced three-way catalyst systems emissions are exceptionally low. NO x control from lean-burn engines demands an additional approach because NO cannot be dissociated under lean conditions. Current lean-burn gasoline engine NO x control involves forming a nitrate phase and periodically enriching the exhaust to reduce it to nitrogen, and this is being modified for use on diesel engines. Selective catalytic reduction with ammonia is an alternative that can be very efficient, but it requires ammonia or a compound from which it can be obtained. Diesel engines produce particulate matter, and, because of health concerns, filtration processes are being introduced to control these emissions. On heavy duty diesel engines the exhaust gas temperature is high enough for NO in the exhaust to be oxidised over a catalyst to NO 2 that smoothly oxidises particulate material (PM) in the filter. Passenger cars operate at lower temperatures, and it is necessary to periodically burn the PM in air at high temperatures.

Materials Selection for Variable Geometry Turbine Nozzle for Gasoline Engine Application

2014 ◽  
Author(s):  
Vivek O. Shettigar ◽  
Apostolos Pesiridis
Keyword(s):  
Diesel Engines ◽  
Internal Combustion Engines ◽  
Gasoline Engine ◽  
Load Condition ◽  
Working Environment ◽  
Exhaust Gas ◽  
Variable Geometry ◽  
Gas Temperature ◽  
Performance Indices ◽  
Gasoline Engines

Turbocharging is a key technology for reducing emissions in modern automotive internal combustion engines. The application of turbochargers has been regarded as the next step in the downsizing I.C. Engines. The technology has demonstrated its ability to increase the power of small engines by over 30%. This technology had a few drawbacks such as selection of appropriate air-fuel ratio which could either provide better transient response at low load condition or provide increased power at full load condition. In the quest to obtain the benefits of the both conditions, Variable Geometry Turbochargers (VGTs) were introduced. They account for a significant share of the market in mechanical turbocharging for diesel engines. The most common and efficient type of flow control device in use in VGT is the pivoting vane array located at the inlet of the turbocharger. The technology has been effectively applied over the past 20 years in diesel engines due to their relatively lower exhaust gas temperature (compared to gasoline engines) which has allowed inexpensive materials to be used. This isn’t the case for gasoline engines due to their high exhaust gas temperatures. In light of this technical challenge, the current paper discusses the attempts at application of VGTs in gasoline engines and evaluates further material options which can be considered as appropriate candidates for use in the movable nozzle section of a VGT. Exhaust gases temperatures of up to 1050°C with the working pressures reaching in excess of 2 bar is the working environment of a typical VGT. A CFD analysis of appropriately selected materials is presented in this paper and was applied to a generic pivoting vane mechanism, producing results for the stresses and deformations experienced by the selected materials. This paper also includes cost and manufacturability discussion of requirements which will eventually dictate the choice of any given material for mass production. The material is chosen with the help of an in-depth selection processes such as the Paul and Beitz method which includes weighing factors and performance indices. Performance indices can be considered as groups of material properties which represent few important aspect of the performance of the component.

scholarly journals Improving Efficiency, Extending the Maximum Load Limit and Characterizing the Control-Related Problems Associated With Higher Loads in a 6-Cylinder Heavy-Duty Natural Gas Engine

2010 ◽  
Author(s):  
Mehrzad Kaiadi ◽  
Per Tunestal ◽  
Bengt Johansson
Keyword(s):  
Natural Gas ◽  
Compression Ratio ◽  
Diesel Engines ◽  
Maximum Load ◽  
Exhaust Gas ◽  
Gas Temperature ◽  
Heavy Duty ◽  
Load Limit ◽  
Overall Efficiency ◽  
Exhaust Gas Temperature

High EGR rates combined with turbocharging has been identified as a promising way to increase the maximum load and efficiency of heavy duty spark ignition Natural Gas engines. With stoichiometric conditions a three way catalyst can be used which means that regulated emissions can be kept at very low levels. Most of the heavy duty NG engines are diesel engines which are converted for SI operation. These engine’s components are in common with the diesel-engine which put limits on higher exhaust gas temperature. The engines have lower maximum load level than the corresponding diesel engines. This is mainly due to the lower density of NG, lower compression ratio and limits on knocking and also high exhaust gas temperature. They also have lower efficiency due to mainly the lower compression ratio and the throttling losses. However performing some modifications on the engines such as redesigning the engine’s piston in a way to achieve higher compression ratio and more turbulence, modifying EGR system and optimizing the turbocharging system will result in improving the overall efficiency and the maximum load limit of the engine. This paper presents the detailed information about the engine modifications which result in improving the overall efficiency and extending the maximum load of the engine. Control-related problems associated with the higher loads are also identified and appropriate solutions are suggested.

scholarly journals The effects of exhaust gas recirculation on NOx storage pathway

2021 ◽  
Vol 268 ◽  
pp. 01017
Author(s):  
Jin Zhao ◽  
Zhijun Li ◽  
Shilong Li ◽  
Shijin Shuai ◽  
Shiyu Liu ◽  
...  
Keyword(s):  
Storage Capacity ◽  
Gasoline Engine ◽  
Exhaust Gas Recirculation ◽  
Exhaust Gas ◽  
Storage Process ◽  
Lean Burn ◽  
Langmuir Hinshelwood Mechanism ◽  
Nitrate And Nitrite ◽  
Increasing Temperature ◽  
Gas Recirculation

A LNT (lean NOx trap) model coupled with EGR (exhaust gas recirculation) was developed based on the Langmuir–Hinshelwood mechanism to investigate the EGR effects on NOx adsorption pathway of LNT catalysts with temperature changed in range 150℃~550℃. Both the nitrate and nitrite adsorption paths were considered for the NOx storage process in the model as well as the spillover of stored NOx between Ba and Pt sites. The data and validation for modelling were from literatures of predecessors and our previous lean-burn gasoline engine experiment*. The model quantified the contributions of both nitrate route and nitrite route to the NOx storage with change of EGR rate (0%~30%) under raw emission atmosphere from tested gasoline engine. The model captured key feature of different trends of nitrate route and nitrite route with increasing temperature (150℃~550℃) under EGR rate varying from 0% to 25%. The LNT model provided insight of reaction mechanism for interpreting the behaviour of NOx storage with change of GER rate and temperature, which contributed to improve the NOx storage capacity when mapping EGR rate for lean-burn engine and catalyst operation strategy optimization.

Effect of Support Materials on Pd Methane Oxidation Catalyst Using Dynamic Estimation Method

2020 ◽  
Author(s):  
Yoshifuru Nitta ◽  
Yudai Yamasaki
Keyword(s):  
Active Sites ◽  
Estimation Method ◽  
Pd Catalyst ◽  
Exhaust Gas ◽  
Gas Temperature ◽  
Ch4 Oxidation ◽  
Lean Burn ◽  
Support Materials ◽  
Dynamic Estimation ◽  
Oxidation Performance

Abstract In the maritime industry, lean burn gas engines have been expected to reduce emissions such as NOx, SOx and CO2. On the other hand, the slipped methane, which is the unburned methane (CH4) emitted from lean burn gas engines have a concern for impact on global warming. It is therefore important to make a progress on the exhaust aftertreatment technologies for lean burn gas engines. As a countermeasure for the slipped methane, Palladium (Pd) catalyst for CH4 oxidation can be expected to provide one of the most feasible methods because Palladium (Pd) catalyst for CH4 oxidation can activate in the lower temperature. However, recent studies have shown that the reversible adsorption by water vapor (H2O) inhibits CH4 oxidation on the catalyst and deactivates its CH4 oxidation capacity. It can be known that the CH4 oxidation performance is influenced by active sites on the Pd catalyst. However, measuring methods for active sites on Pd catalyst under exhaust gas conditions could not be found. Authors thus proposed a dynamic estimation method for the quantity of effective active sites on Pd catalyst in exhaust gas temperature using water-gas shift reaction between the saturated chemisorbed CO and the pulse induced H2O. The previous study clarified the relationship between adsorbed CO volume and Pd loading in gas engine exhaust gas temperature and revealed the effects of flow conditions on the estimation of adsorbed CO volume. However, in order to improve CH4 oxidation performance on Pd catalyst under exhaust gas conditions, it is important that effects of support materials on active sites should clarify. This paper introduced experimental results of estimation of absorbed CO volume on different support materials of Pd catalysts by using the dynamic evaluation method. Experimental results show that chemisorbed CO volume on Pd/Al2O3 catalyst exhibits higher chemisorbed CO volume than that of Pd/SiO2 and Pd/Al2O3-SiO2 catalyst in 250–450 °C. These results can provide a part of the criteria for the application of Pd catalyst for reducing the slipped methane in exhaust gas of lean burn gas engines.

Development of the New NOx Reduction Catalyst With Hydrocarbons and the Cleanup Systems of Exhaust Gases for Lean-Burn Gas Engines

1999 ◽  
Author(s):  
Yukimaro Murata ◽  
Shigeo Satokawa ◽  
Ken-ichi Yamaseki ◽  
Hiromichi Yamamoto ◽  
Hiroshi Uchida ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Nox Reduction ◽  
Reducing Agent ◽  
Exhaust Gas ◽  
Lean Burn ◽  
Scr Catalyst ◽  
Exhaust Gases ◽  
Scr System ◽  
Three Way Catalyst ◽  
Al2o3 Catalyst

Abstract Development of cleanup technology for combustion waste is more and more necessary today. The emissions of stationary natural-gas-fueled engines can be purified by in-engine methods and by treatment of the exhaust gases. This paper describes the latter technologies. There are two conventional technologies for nitrogen oxides (NOx) reduction methods by the three-way catalyst and the selective catalytic reduction (SCR). The three-way catalyst operates only well within a narrow air-to-fuel ratio window, but when the exhaust gas is too lean, the NOx will not be removed. The SCR of NOx in exhaust gas has the advantage that the engine process itself does not have to be adapted and closely controlled as in case of extended lean-burn technologies. Ammonia or urea injected into the exhaust gas must be used as the reducing agent with conventional SCR system. However, the addition of a SCR system for the small or middle size cogeneration system, it would pose problems regarding cost and space for storage and injection of the reducing agent. Therefore, we have examining the catalyst which is able to reduce NOx with hydrocarbons (HC) containing in exhaust gas itself, and we developed the new HC-SCR catalyst. The de-NOx system using the HC-SCR catalyst has numerous advantages as follows: 1) Compactness and low cost: catalyst unit only 2) High efficiency: adaptation of lean-burn technology for engine operation 3) High performance: excellent catalytic activity and durability 4) Safeties: no use of ammonia as a reducing agent In this study, we report the catalytic activity of the new catalyst and propose a total cleanup system for exhaust gases of lean-burn gas engines. Alumina-supported silver (Ag/Al2O3) was used for the new catalyst. When the measurement was carried out with one reducing gas in the reactant gas each, propane and propane were most effective for NOx reduction, ethane and ethylene were secondly effective for NOx reduction. Practical test of the Ag/Al2O3 catalyst was carried out using a real exhaust gas from a 400 kW class lean-bum gas engine. The full-size catalyst was obtained by washcoating the catalyst powder on a metallic monolithic honeycomb substrate (size: 650 mm ϕ × 324 mmL, 200 cells/inch2). When the engine was operated at 400 kWe output, temperature of the exhaust gas was 762 K and GHSV was 17635 h−1. The NOx conversion was reached to 30% and the catalytic activity was maintained after the operation for more than 2000 hr. Conventional alumina-supported platinum (Pt/Al2O3) catalysts were mounted to exhaust gas line for cleanup test. The emission of CO and aldehydes was in the exhaust gas, but it could be highly removed by the Pt/Al2O3 catalyst. Practical tests of this catalyst were carried out using 300–400 kW class lean-burn gas engines. GHSV of these catalysts were about 50,000 h−1. The CO and aldehydes conversion were reached to more than 90% and the catalytic activities were maintained after the operation for about 10,000 hr.

scholarly journals Examination of Metal Doped Zeolite as Catalyst to Reduce NOX Emission from Lean Burn Gasoline Engines

2019 ◽  
Vol 9 (1S) ◽  
pp. 45-50
Keyword(s):  
Gasoline Engine ◽  
Fuel Injection ◽  
Catalytic Converter ◽  
Nox Emission ◽  
Gasoline Direct Injection ◽  
Oxidation Catalyst ◽  
Gas Temperature ◽  
Lean Burn ◽  
Exchange Method ◽  
Gasoline Engines

Lean burn gasoline direct injection (GDI) engines are the most preferred gasoline engines because of their low fuel consumption and high thermal efficiency. However, these engines produce exhaust gases that are particularly rich in oxygen and therefore the present three-way catalytic converter (TWC) is not suitable for converting the generated NOX emission into Nitrogen gases. In this present work, a new method of reducing Nitrogen Oxides emission in a gasoline engine is attempted by using an ordinary oxidation catalyst together with a deNOX(zeolite-based) catalyst. In this work, Na-form of ZSM-5 zeolite was used as a catalyst and cupric chloride (CuCl2 ) and ferric chloride (FeCl3 ) where used as transition metals. Cu-ZSM5 and Fe-ZSM5 catalyst were prepared separately in our laboratory. Na+ ion exchange method is used to prepare the catalyst. After that Cu-ZSM% and Fe- ZSM5 catalyst were washcoated separately onto the blank monoliths. Oxidation monoliths ( for oxidation of CO and HC into CO2 and H2O) were purchased directly from market. One oxidation monolith and one zeolite coated monolith were placed in a stainless steel container and canned with inlet and outlet cones ( forming catalytic convertor ). Experiments were conducted on a 2 cylinder Multi Point Port Fuel Injection engine along with a dynamometer. Exhaust emissions such as NOX, CO, HC, O2 , CO2 were measured with AVL Di-gas-444 Analyzer. Exhaust gas temperature is measured with the use of a thermocouple. Firstly load tests (4, 7, 10, 13, and 16KW) were conducted on the engine without catalytic convertor was fixed close to the outlet pipe and the test were conducted again with same loading condition as mentioned above. Then by the same above procedure is followed to conduct test with Cu-ZSM5 and Fe-ZSM5 catalytic convertors. From the results it is observed that both Cu and Fe zeolite catalyst minimize emissions than the commercial catalytic converter.

scholarly journals EXPERIMENTAL INVESTIGATION ON THE EFFECT OF ADDING CYCLOHEXANONE TO GASOLINE IN SI ENGINE EMISSIONS AND PERFORMANCE

2021 ◽  
Vol 21 (4) ◽  
pp. 259-273
Author(s):  
Abed Al-Khadhim M. Hassan ◽  
Sadeq Abdul-Azeez Jassam
Keyword(s):  
Heat Balance ◽  
Gasoline Engine ◽  
Direct Injection ◽  
Calorific Value ◽  
Experimental Tests ◽  
Spark Ignition Engine ◽  
Exhaust Gas ◽  
Gas Temperature ◽  
Brake Mean Effective Pressure ◽  
Exhaust Gas Temperature

The aim of the present work is to investigate the influence of adding some ketone compounds on the performance, emissions, heat balance and exhaust gas temperature of spark ignition engine. The ketone used in this study is cyclohexanone (C6H10O). This ketone has been added to the base fuel (gasoline) with three concentration ranges (3, 6 and 9%) respectively. All experimental tests were carried out on gasoline engine type (Nissan QG18DE), four cylinders, 4-stroke, direct injection, with compression ratio (9.5:1). The acquired results showed that adding of ketones affect the physical properties of gasoline. Where the density changed from (710 kg/m3) for net gasoline to (740.8 kg/m3) for cyclohexanone at adding ratio of (9%). The octane number also increased from (86) for pure gasoline to (97.7) for fuel with 9% cyclohexanone. The calorific value will be decrease from (43000 kJ/kg) for gasoline to (42077.5) for cyclohexanone at adding ratio of (9%). The addition of ketones improves the emissions characteristic of engine. The best reduction of (UHC, CO_2, CO and NOx) was (49.04, 22.43, 35.02 and 42.14%) recorded by cyclohexanone addition at ratio of (9%). In the case of performance, all parameters of performance improved by adding ketones. The brake specific fuel consumption reduced by (8.9%) by adding (9%) of cyclohexanone which recorded as the best reduction through all types. The best increment of brake power, brake thermal efficiency, brake mean effective pressure and volumetric efficiency was (17.3, 8.98, 17.25 and 12.7%) is achieved by adding (9%) of cyclohexanone. Also, the exhaust gas temperature will be increase by adding ketones. The percentage increasing of exhaust gas temperature was (28.31%) recorded by cyclohexanone addition at ratio of (9%). In the case of heat balance, the best increment of total heat internal energy was (6.59) at (9%) of cyclohexanone.  

Calculating the Speed of Sound in an Engine Exhaust Stream

2008 ◽  
Author(s):  
Justin D. Keske ◽  
Jason R. Blough
Keyword(s):  
Chemical Composition ◽  
Speed Of Sound ◽  
Gasoline Engine ◽  
Combustion Process ◽  
Exhaust Gas ◽  
Gas Temperature ◽  
Fuel Blend ◽  
Atmospheric Air ◽  
Exhaust Gases ◽  
Exhaust Stream

The actual speed of sound in the exhaust medium of an engine plays an extensive role in the noise attenuation characteristics of the engine’s muffler system. For 2-stroke engine applications, the speed of sound in the exhaust gas also greatly affects how the expansion chamber is tuned to maintain maximum power output. The combustion process in an engine creates exhaust gases that differ from the composition of atmospheric air. This difference in chemical composition and humidity content yield a different density and ratio of specific heats. These ultimately yield different sound speeds in the exhaust gases compared to atmospheric air. This paper performs a full chemical analysis of the combustion process in an internal combustion gasoline engine to yield the chemical composition of the of the exhaust gases. An algorithm is written to calculate the speed of sound in the exhaust stream. The inputs of the algorithm include measurements of temperature, pressure, and relative humidity of the ambient intake air, specification of the gasoline/ethanol fuel blend, and a direct measurement of the exhaust gas temperature. Comparisons are made between sound speed approximation calculations based on air to calculations obtained by the algorithm.

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