NO reduction by CO over TiO_2-γ-Al_2O_3 supported In/Ag catalyst under lean burn conditions

TiO2/γ-Al2O3 supported In/Ag catalysts were prepared by impregnation method,and investigated for NO reduction with CO as the reducing agent under lean burn conditions.The microscopic structure and surface properties of the catalysts were studied by N2 adsorption-desorption,X-ray diffraction,transmission electron microscopy,X-ray photoelectron spectroscopy,ultraviolet-visible spectroscopy,H2 temperature-programmed reduction and Fourier transform infrared spectroscopy.TiO2/γ-Al2O3 supported In/Ag is a good catalyst for the reduction of NO to N2.It displayed high dispersion,large amounts of surface active components and high NO adsorption capacity,which gave good catalytic performance and stability for the reduction of NO with CO under lean burn conditions.The silver species stabilized and improved the dispersion of the indium species.The introduction of TiO2 into the γ-Al2O3 support promoted NO adsorption and improved the dispersion of the indium species and silver species.

Three-Dimensional Models for Analyzing the Cyclic Variations in a Lean Burn CNG Engine

Three-dimensional models, consisting of the flame kernel formation model, flame kernel development model and natural gas single step reaction model, are used to analyze the contribution of cyclic equivalence ratio variations to cyclic variations in the compressed natural gas （CNG） lean burn spark ignition engine. Computational results including the contributions of equivalence ratio cyclic variations to each combustion stage and effects of engine speed to the extent of combustion variations are discussed. It is concluded that the equivalence ratio variations affect mostly the main stage of combustion and hardly influence initial kernel development stage.

Enhancement of Activity of SnO_(2)-doped In_(2)O_(3)/Al_(2)O_(3) Catalyst for NO Reduction with Propene in the Presence of H_(2)O and SO_(2)

The novel bimetallic Sn-Im/Al2O3 catalysts prepared by three methods for NO reduction by propene were investigated. The results showed that the catalytic activity was enhanced significantly in the presence of H2O on sol-gel catalyst, and the maximum NO conversion increased from 46% to 92%, even in the presence of 100 ppm SO2, NO conversion was still 80%.

Combustion and emission characteristics of a dual injection system applied to a DISI engine

Concerns about environmental pollution and energy shortages have increased worldwide. One approach to reduce CO2 emissions from gasoline engines is to achieve stratified charge combustion with various injection ratios using port fuel injection （PFI） and direct injection. The combustion and emission characteristics of a 4-valve direct injection spark ignition （DISI） engine equipped with a dual injection system were investigated while the injection ratio was varied. When the direct injection ratio increased, the lean limit A/F was extended. This suggests that the dual injection gasoline engine with both PFI and direct injection can meet severe vehicle emission and fuel economy requirements. The dual injection system had higher combustion pressure than that of either a conventional or direct injection systems. Therefore, the engine power of a dual injection DISI engine would be higher than that of a single injection DISI engine. However, NOx emissions increased compared with the emission levels in both PFI and DISI systems.

Storage-Reduction of NO_(x)over Combined Catalysts of Pt/Ba/Al_(2)O_(3)-Mn/Ba/Al_(2)O_(3):Carbon Monoxide as Reductant

Storage-reduction of NOx by carbon monoxide was investigated over combined catalysts of Mn/Ba/Al2O3-Pt/Ba/Al2O3. Combination of Mn/Ba/Al2O3 and Pt/Ba/Al2O3 catalysts in different ways showed excellent NOx storage-reduction performance and the content of Pt could be reduced by 50%. Not only the addition of 5Mn/15Ba/Al2O3 to 1Pt/15Ba/Al2O3 could improve its storage ability, but also enhance the NOx conversion consequently. NOx conversion over the combined catalysts （the combined catalysts Ⅰ and Ⅱ） was increased under dynamic lean-rich burn conditions, the maximum NOx conversion increased from 69.4% to respectively 78.8% and 75.7% over two combined catalysts.

Activity Enhancement of Pt/Ba/Al_(2)O_(3) Mixed with Mn/Ba/Al_(2)O_(3) for NO_(x) Storage-reduction by Hydrogen

Abstract： Mn/Ba/Al2O3 catalyst for NO oxidation-storage and Pt/Ba/Al2O3 catalyst mixed with Mn/Ba/Al2O3 for NOx storage-reduction by hydrogen were investigated. The results showed that Mn/Ba/Al2O3 had large nitrogen oxides storage capacity （397.9 μmolg^-1） under lean burn condition. When Pt/Ba/Al2O3 catalyst was mixed with Mn/Ba/Al2O3 in equal weight proportion, the NOx conversion increased between 250 ℃ and 500 ℃ under the dynamic lean-rich burn conditions, and the maximum NOx conversion increased from 95.4% to 98.2%. Mn/Ba/Al2O3 has promoted NOx storing in the lean stage and improved NOx reduction efficiency in the rich stage, these might result in higher NOx conversion over the low Pt loading content catalyst.

High Activity SnO_2/Al_2O_3 Catalyst for NO Reduction in the Presence of Oxygen

The novel sol-gel SnO2/Al2O3 catalysts for selective catalytic reduction NO by propene under lean burn condition were investigated. The results showed thatthe maximum NO conversion was 82% on the SnO2/Al2O3 (5%Sn) catalyst, and the presence of H2O and SO2 improved the catalytic activity at low temperature. The catalytic activity of NO2 reduction by propene is much higher than that of NO at the entire temperature range, and the maximum NO2 conversion reached nearly 100% around the temperature 425℃.

Experimental study of stratified lean burn characteristics on a dual injection gasoline engine

Due to increasingly stringent fuel consumption and emission regulation,improving thermal efficiency and reducing particulate matter emissions are two main issues for next generation gasoline engine.Lean burn mode could greatly reduce pumping loss and decrease the fuel consumption of gasoline engines,although the burning rate is decreased by higher diluted intake air.In this study,dual injection stratified combustion mode is used to accelerate the burning rate of lean burn by increasing the fuel concentration near the spark plug.The effects of engine control parameters such as the excess air coefficient(Lambda),direct injection(DI)ratio,spark interval with DI,and DI timing on combustion,fuel consumption,gaseous emissions,and particulate emissions of a dual injection gasoline engine are studied.It is shown that the lean burn limit can be extended to Lambda=1.8 with a low compression ratio of 10,while the fuel consumption can be obviously improved at Lambda=1.4.There exists a spark window for dual injection stratified lean burn mode,in which the spark timing has a weak effect on combustion.With optimization of the control parameters,the brake specific fuel consumption(BSFC)decreases 9.05%more than that of original stoichiometric combustion with DI as 2 bar brake mean effective pressure(BMEP)at a 2000 r/min engine speed.The NO_(x) emissions before threeway catalyst(TWC)are 71.31%lower than that of the original engine while the particle number(PN)is 81.45%lower than the original engine.The dual injection stratified lean burn has a wide range of applications which can effectively reduce fuel consumption and particulate emissions.The BSFC reduction rate is higher than 5%and the PN reduction rate is more than 50%with the speed lower than 2400 r/min and the load lower than 5 bar.

Numerical and Experimental Investigation on the Performance of Lean Burn Catalytic Combustion for Gas Turbine Application

This manuscript presents our numerical and experimental results regarding the performance characteristics of lean bum catalytic combustion for gas turbine application. The reactant transport was assumed to be controlled by both bulk diffusion as well as surface kinetics, implemented by means of an approximate reaction rate equation and empirical coefficients to incorporate reaction mechanism. Experimental and numerical results were compared to examine the effects of methane mole fraction, inlet temperature, operating pressure, velocity and hydrogen spe- cies on combustion intensity. The results indicate that inlet temperature is the most significant parameter that im- pacts operation of the catalytic combustor and the most effective methods for improving the methane conversion are increasing the inlet temperature and increasing the methane mole fraction. Simulations from ID heterogene- ous plug flow model can capture the trend of catalytic combustion and describe the behavior of the catalytic mo- nolith in detail. The addition of hydrogen will provide heat release by the exothermie combustion reaction so that the reactants reach a temperature at which methane oxidation can light-off.

Part-load Performance Characteristics of a Lean Burn Catalytic Combustion Gas Turbine System

The purpose of this study is to compare the part-load performance of a lean burn catalytic combustion gas turbine (LBCCGT) system in three different control modes: varying fuel, bleeding off the fuel mixture flow after the compressor and varying rotational speed. The conversions of methane species for chemical process are considered. A 1D heterogeneous plug flow model was utilized to analyze the system performance. The actual turbomachinery components were designed and predicted performance maps were applied to system performance research. The part-load characteristics under three control strategies were numerically investigated. The main results show that: the combustor inlet temperature is a significant factor that can significantly affect the part-load characteristics of the LBCCGT system; the rotational speed control mode can provide the best performance characteristics for part-load operations; the operation range of the bleed off mode is narrower than that of the speed control mode and wider than that of the fuel only mode; with reduced power, methane does not achieve full conversion over the reactor at the fuel only control mode, which will not warrant stable operation of the turbine system; the thermal efficiency of the LBCCGT system at fuel only control strategy is higher than that at bleed off control strategy within the operation range.

Extremum seeking-based optimal EGR set-point design for combustion engines in lean-burn mode

In lean combustion mode,exhaust gas ratio(EGR)is a significant factor that affects fuel economy and combustion stability.A proper EGR level is beneficial for the fuel economy;however,the combustion stability(coefficient of variation(COV)in indicated mean effective pressure(IMEP))deteriorated monotonously with increasing EGR.The aim of this study is to achieve a trade-off between the fuel economy and combustion stability by optimizing the EGR set-point.A cost function(J)is designed to represent the trade-off and reduce the calibration burden for optimal EGR at different engine operating conditions.An extremum-seeking(ES)algorithm is adopted to search for the extreme value of J and obtain the optimal EGR at an operating point.Finally,a map of optimal EGR set-value is designed and experimentally validated on a real driving cycle.