Showing papers on "Lean burn published in 2009"

NOx abatement for lean-burn engines under lean–rich atmosphere over mixed NSR-SCR catalysts: Influences of the addition of a SCR catalyst and of the operational conditions

Abstract: Mixtures of equal amounts of a Pt–Rh/Ba/Al2O3 NOx storage reduction (NSR) model catalyst and Ag/Al2O3, Co/Al2O3 or Cu/ZSM-5 selective catalytic reduction (SCR) model catalyst were evaluated for the NOx removal activity under lean–rich atmosphere. NOx removal activity was increased by adding Co/Al2O3 or Cu/ZSM-5 to Pt–Rh/Ba/Al2O3 while adding Ag/Al2O3 had no significant influence. Experiments performed by using two catalytic beds (upstream Pt–Rh/Ba/Al2O3 and downstream Co/Al2O3 or Cu/ZSM-5) suggested that both SCR catalysts are able to reduce NOx with the NH3 produced during the rich step on Pt–Rh/Ba/Al2O3. Among the studied catalysts, the Pt–RhBa/Al2O3 + Cu/ZSM-5 physically mixed one showed the highest activity. This catalyst mixture presented an improved performance, as compared to the NSR catalyst, regardless of the reductant used (CO and/or H2) or of the reduction time (10, 5 or 2.5 s). The highest activity was obtained by using both CO and H2 as reductant during the rich pulse. The addition of water in the inlet gas led to a decrease of the NOx removal activity of the catalyst mixture. Nevertheless, the NOx removal activity of the mixed Pt–RhBa/Al2O3 + Cu/ZSM-5 catalyst was still significantly higher than that of Pt–RhBa/Al2O3.

Exhaust system for a lean burn ic engine

Abstract: An exhaust system(10) for a lean-burn internal combustion engine (12) comprises a first substrate monolith (16) comprising a catalyst for oxidising nitric oxide (NO) comprising a catalytic oxidation component followed downstream by a second substrate monolith (18) which is a wall-flow filter having inlet channels and outlet channels, wherein the inlet channels comprise a NO x absorber catalyst (20) and the outlet channels comprise a catalyst for selective catalytic reduction (22) of nitrogen oxides with nitrogenous reductant.

Effect of Compression Ratio on Cycle-by-Cycle Variations in a Natural Gas Direct Injection Engine

Abstract: Cycle-by-cycle variations of a natural gas direct-injection spark ignition engine at different compression ratios were investigated. The results show that the lean burn limit of the natural-gas direct injection engine can be extended to a larger overall excess air ratio compared with that of the homogeneous charge natural gas engine. The coefficient of variations (CoV) of indicated mean effective pressure decreases with the increase of compression ratio. However, CoV of indicated mean effective pressure is increased at high engine load when compression ratio is larger than 12. The cycle-by-cycle variations are more clearly demonstrated in CoV of indicated mean effective pressure rather than in CoV of cylinder peak pressure. Average values of flame development duration, main combustion duration, and total combustion duration are decreased and combustion is improved with increasing compression ratio. This is the reason for decreasing cycle-by-cycle variations in the natural gas direct-injection engine. Bett...

Green Engines Development Using Compressed Natural Gas as an Alternative Fuel: A Review

Abstract: Problem statement: The Compressed Natural Gas (CNG) is a gaseous form of natural gas, it have been recognized as one of the promising alternative fuel due to its substantial benefits compared to gasoline and diesel. Natural gas is produced from gas wells or tied in with crude oil production. Approach: Natural gas is promising alternative fuel to meet strict engine emission regulations in many countries. Compressed Natural Gas (CNG) has long been used in stationary engines, but the application of CNG as a transport engines fuel has been considerably advanced over the last decade by the development of lightweight high-pressure storage cylinders. Results: The technology of engine conversion was well established and suitable conversion equipment is readily available. For petrol engines or spark ignition engines there are two options, a bi-fuel conversion and use a dedicated to CNG engine. The diesel engines converted or designed to run on natural gas, there were two main options discussed. There are dual-fuel engines and normal ignition can be initiated. Natural gas engines can be operated at lean burn and stoichiometric conditions with different combustion and emission characteristics. Conclusions: In this study, the low exhaust gas emissions of CNG engines research and development were highlighted. Stoichiometric natural gas engines were briefly reviewed. To keep the output power, torque and emissions of natural gas engines comparable to their gasoline or diesel counterparts. High activity for future green CNG engines research and development to meet future stringent emissions standards was recorded in the study.

Exhaust gas purification method using selective reduction catalyst

Abstract: An exhaust gas purification method for reducing selectively NOx in exhaust gas, which is exhausted from a lean burn engine, such as a boiler, a gas turbine or a lean-burn-type gasoline engine, a diesel engine, with a selective reduction catalyst and ammonia, characterized in that an aqueous solution of urea is spray-supplied to the selective reduction catalyst, comprising at least the following zeolite (A) and the hydrolysis promotion component of urea (B), and it is contacted at 150 to 600oC, and ammonia is generated in a ratio of [NH3/NOx=05 to 15] to NOx in exhaust gas, as converted to ammonia, and a nitrogen oxide is decomposed into nitrogen and water; ·zeolite (A): zeolite comprising an iron element ·hydrolysis promotion component (B) : a complex oxide comprising at least one kind selected from titania or titanium, zirconium, tungsten, silicon or alumina

Novel Fluidized Bed Reactor for Integrated NOX Adsorption-Reduction with Hydrocarbons

Abstract: In order to avoid the negative impact of excessive oxygen in the combustion flue gases on the selectivity of most hydrocarbon selective catalytic reduction (HC-SCR) catalysts, an integrated NOx adsorption-reduction process has been proposed in this study for the treatment of flue gases under lean burn conditions by decoupling the adsorption and reduction into two different zones. The hypothesis has been validated in a novel internal circulating fluidized bed (ICFB) reactor using Fe/ZSM-5 as the catalyst and propylene as the reducing agent. Effects of propylene to the NOx molar ratio, flue gas oxygen concentration, and gas velocity on NOx conversion were studied using simulated flue gases. The results showed that increasing the ratio of HC:NO improved the reduction performance of Fe/ZSM-5 in the ICFB reactor. NOx conversion decreased with an increasing flue gas flow velocity in the annulus U{sub A} but increased with an increasing reductant gas flow velocity in the draft tube U{sub D}. The NOx adsorption ratio decreased with increasing U{sub A}. In most cases, NOx conversion was higher than the adsorption ratio due to the relatively poor adsorption performance of the catalyst. Fe/ZSM-5 showed a promising reduction performance and a strong inhibiting ability on the negative impactmore » of excessive O{sub 2} in the ICFB reactor, proving that such an ICFB reactor possessed the ability to overcome the negative impact of excessive O{sub 2} in the flue gas using Fe/ZSM-5 as the deNOx catalyst. 22 refs., 10 figs.« less

Combustion and Emission Characteristics of a Natural Gas Engine under Different Operating Conditions

Abstract: Natural gas is a promising alternative fuel of internal combustion engines. In this paper, the combustion and emission characteristics were investigated on a natural gas engine at two different fuel injection timings during the intake stroke. The results show that fuel injection timing affects combustion processes. The optimum spark timing (MBT) achieving the maximum indicated mean effective pressure (IMEP) is related to fuel injection timing and air fuel ratio. At MBT spark timing, late fuel injection timing delays ignition timing and prolongs combustion duration in most cases. But fuel injection timing has little effect on IMEP at fixed lambdas. The coefficient of variation (COV) of IMEP is dependent on air fuel ratio, throttle positions and fuel injection timings at MBT spark timing. The COV of IMEP increases with lambda in most cases. Late fuel injection timings can reduce the COV of IMEP at part loads. Moreover, engine-out CO and total hydrocarbon (THC) emissions can be reduced at late fuel injection timing.

Exhaust purifying system for internal combustion engine

Abstract: In an internal combustion engine including an NSR catalyst and an SCR, to provide an exhaust purifying system that can limit aggravation of emissions by allowing the SCR to recover effectively from degraded performance caused by poisoning. An exhaust purifying system for an internal combustion engine capable of a lean burn operation includes an NSR catalyst disposed in an exhaust passage of the internal combustion engine; an SCR disposed downstream of the NSR catalyst; means for detecting sulfur poisoning of the SCR; and means for increasing a bed temperature of the SCR when the poisoning detecting means detects sulfur poisoning of the SCR. The temperature increasing means includes bank control, stoichiometric control, and rich spike control, any one of which is selected for performance according to an operating condition of the internal combustion engine.

Nox emission control system for hydrocarbon fueled power source

Abstract: A method of reducing NOx in a lean burn engine exhaust stream from a hydrocarbon burning engine may be first passing the exhaust stream over a thrifted diesel oxidation catalyst that substantially completes the oxidation of carbon monoxide to carbon dioxide and the oxidation of hydrocarbons (HC) to carbon dioxide and water. Next, separate additions of ozone and ammonia or urea may be introduced to the exhaust gas stream upstream of the catalytic reduction reactor at temperatures below 250 degrees Celsius. The additions of ozone and ammonia or urea modify the exhaust gas composition to improve the performance of NOx reduction catalysts in the catalytic reduction reactor. At temperatures above 250 degrees, the ozone addition may be reduced or eliminated, while the ammonia addition can be controlled as a function of the amount of NOx in the exhaust stream and the temperature of the catalytic reduction reactor.

Exhaust aftertreatment systems for gasoline and alternative-fueled engines, with reduction of HC, CO, NOx, and PM

Abstract: An exhaust gas emissions aftertreatment system for spark-ignition engines, which simultaneously reduces the particulate matter, HC, CO, and NOx content of the exhaust. Various embodiments of the system have both a closely-coupled TWC device, and an under-floor treatment device. The under-floor device has either TWC or NOx reduction functionality, depending on whether the engine is run under stiochiometric or lean burn operating conditions.

Exhaust system for lean-burn internal combustion engine comprising PD-AU-Alloy catalyst

Abstract: An apparatus (10) comprising a lean burn internal combustion engine (12) and an exhaust system (14) comprising one or more catalytic aftertreatment component (18, 20, 22), wherein one or more catalytic aftertreatment component comprises a catalyst composition comprising an alloy consisting of palladium and gold on a metal oxide support.

Flame Propagation Speed of CO2 Diluted Hydrogen-Enriched Natural Gas and Air Mixtures

Abstract: Adding hydrogen into natural gas can extend its lean burn capacity, improve engine performance at low load operation, and reduce unburned hydrocarbon emissions at the cost of increased NOx emissions. In this paper, flame propagation of premixed CO2 diluted natural gas/hydrogen/air mixtures under various initial pressures was studied by using a constant volume combustion bomb together with high-speed Schlieren photography. Laminar flame speed and laminar burning velocity as well as Markstein length and flame thickness were obtained for the diluted stoichiometric fuel/air mixtures with different natural gas/hydrogen fractions and diluent ratios under normal, reduced, and elevated pressures. The results showed that both unstretched flame speed and unstretched burning velocity are reduced with the increase of diluent ratio as well as initial pressure (except when the hydrogen fraction is 80%). Hydrogen-enriched natural gas with higher hydrogen fraction can tolerate relatively more diluent gas.

The lean burn direct-injection jet-ignition flexi gas fuel LPG/CNG engine

Abstract: This paper explores through engine simulations the use of LPG and CNG gas fuels in a 1.5 liter Spark Ignition (SI) four cylinder gasoline engine with double over head camshafts, four valves per cylinder equipped with a novel mixture preparation and ignition system comprising centrally located Direct Injection (DI) injector and Jet Ignition (JI) nozzles. With DI technology, the fuel may be introduced within the cylinder after completion of the valve events. DI of fuel reduces the embedded air displacement effects of gaseous fuels and lowers the charge temperature. DI also allows lean stratified bulk combustion with enhanced rate of combustion and reduced heat transfer to the cylinder walls creating a bulk lean stratified mixture. Bulk combustion is started by a Jet Ignition (JI) system introducing in the main chamber multiple jets of reacting gases for enhanced rate of combustion, initiating main chamber burning in multiple regions with reduced sensitivity to mixture state and composition. Coupling of JI and DI allows the development of a lean burn engine making possible operation up to main chamber overall fuel-to-air equivalence ratios reducing almost to zero and throttle-less load control by quantity of fuel injected as in the diesel engine. Results are presented in terms of maps of brake specific fuel consumption (BSFC) and efficiency and maximum power densities. Load variations are obtained by varying the air to fuel equivalence ratio from ?=1 up to ?=6.6. Maximum power densities running ?=1 are 80 hp/liter (60 kW/liter) with CNG and almost 90 hp/liter (67 kW/liter) with LPG. BSFCs are as low as 200 and 190 g/kWh and brake efficiencies are up to 39 and 37% respectively with LPG and CNG running lean ?=1.65. Low BSFCs and high brake efficiencies are possible from 25 to 100% of engine load.

Internal combustion engine i.e. lean-burn spark-ignition engine, operating method for vehicle, involves storing ammonia on ammonia-selective catalytic reduction device fluidly serially connected downstream of catalytic device

Abstract: The method involves controlling an internal combustion engine (10) to a preferred air/fuel ratio to generate an engine-out exhaust gas feedstream including preferred concentrations of nitric oxide, carbon monoxide, and hydrogen. The nitric oxide, carbon monoxide, and hydrogen are converted to ammonia across a catalytic device (48), and the ammonia is stored on an ammonia-selective catalytic reduction device (50) fluidly serially connected downstream of the catalytic device, where the ammonia-selective catalytic reduction device includes a catalytic material comprising a base metal. An independent claim is also included for an engine control system comprising an internal combustion engine system.

Using Hythane as a Fuel in a 6-Cylinder Stoichiometric Natural-gas Engine

Abstract: Combination of right EGR rates with turbocharging has been identified as a promising way to increase the maximum load and efficiency of heavy duty spark-ignited 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. However dilution limit is limited in these types of engines because of the lower burnings rate of natural gas with higher EGR rates. One way to extend the dilution limit of a natural gas engine is to run the engine with Hythane (natural gas+ some percentage hydrogen). Previously benefits of hydrogen addition to a Lean Burn natural-gas fueled engine was investigated [1] however a complete study for stoichiometric operation was not performed.This paper presents measurements made on a heavy duty 6-cylinder natural gas engine. Three different experiments were designed and tested to investigate first of all if the engine encounters too severe knocking problems, second how and why, Hythane affect the running and finally how lean limit and dilution limit will be improved. The experiments were performed successfully and the results showed no significant differences between natural gas and Hythane in terms of efficiency and emissions when engine operates stoichiometric. (Less)

Engine Control System Implementing Lean Burn 6-Stroke Cycle

Abstract: A control system (12) for an engine (10) having a combustion chamber (22) is disclosed. The control system may have a fuel injector (40) configured to selectively inject fuel into the combustion chamber, and a controller (54) in communication with the fuel injector. The controller may be configured to activate the fuel injector during a first compression stroke to initiate fuel injection in an amount and at a timing that results in a stratified lean air/fuel mixture within the combustion chamber during a first combustion event of a six- stroke cycle. The controller may also be configured to activate the fuel injector during a first power stroke to initiate fuel injection in an amount and at a timing that results in a homogenous lean air/fuel mixture within the combustion chamber during a second combustion event of the same six-stroke cycle.

Air separation membranes : an alternative to EGR in large bore natural gas engines.

Abstract: Air Separation Membranes (ASM) could potentially replace Exhaust Gas Recirculation (EGR) technology in engines due to the proven benefits in NOx reduction but without the drawbacks of EGR. Previous investigations of Nitrogen Enriched Air (NEA) combustion using nitrogen bottles showed up to 70% NOx reduction with modest 2% nitrogen enrichment. The investigation in this paper was performed with an ASM capable of delivering at least 3.5% NEA to a single cylinder spark ignited natural gas engine. Low Temperature Combustion (LTC) is one of the pathways to meet the mandatory ultra low NOx emissions levels set by regulatory agencies. In this study, a comparative assessment is made between natural gas combustion in standard air and 2% NEA. Enrichment beyond this level degraded engine performance in terms of power density, Brake Thermal Efficiency (BTE), and unburned hydrocarbon (UHC) emissions for a given equivalence ratio. The ignition timing was optimized to yield maximum brake torque for standard air and NEA. Subsequently, conventional spark ignition (SI) was replaced by laser ignition (LI) to extend lean ignition limit. Both ignition systems were studied under a wide operating range from ψ: 1.0 to the lean misfire limit. It was observed that with 2% NEA, for a similar fuel quantity, the equivalence ratio (Ψ) increases by 0.1 relative to standard air conditions. Analysis showed that lean burn operation along with NEA and alternative ignition source such as LI could pave the pathway for realizing lower NOx emissions with a slight penalty in BTE.Copyright © 2009 by ASME

Formation of formaldehyde in lean-burn gas engines

Abstract: In recent times stationary gas engines, especially those fuelled with poor gases such as biogas or landfill gas, have shown amounts of formaldehyde (HCHO) emissions exceeding the given limits of the German emission regulation TA Luft. In order to achieve compliance with the emission regulations, research was conducted at the Lehrstuhl fur Verbrennungskraftmaschinen of the Technische Universitat Munchen to discover the source of formaldehyde emissions as well as determining the influence of internal engine modifications on emissions. This research project No. 918 was initiated by the Forschungsvereinigung Verbrennungskraftmaschinen e. V. (FVV, Research Association for Combustion Engines). For investigations a 4-l and a 1.7-l single-cylinder SI engine were used.

Effect of Hydrogen Addition on Idle Performance of a Spark-Ignited Gasoline Engine at Lean Conditions with a Fixed Spark Advance

Abstract: Spark-ignited engines always suffer high specific fuel consumption, emissions, and cyclic variation at idle and lean conditions. An experimental investigation aiming at extending the engine lean burn limits and improving the engine economic and emissions performance with hydrogen addition at idle conditions was carried out on a 4-cylinder spark-ignited (SI) gasoline engine. The engine was modified to permit hydrogen and gasoline to be injected into the intake ports simultaneously to realize a hybrid hydrogen−gasoline engine (HHGE). The hydrogen and gasoline flow rates were governed by a hybrid electronic control unit (HECU). Three hydrogen volumetric fractions of 0, 3, and 6% in the intake were applied to investigate the effects of hydrogen addition on engine thermal efficiency, combustion duration, cyclic variation, and emissions at idle conditions using a fixed spark advance. Under each hydrogen enrichment level, the engine was gradually leaned by reducing the gasoline flow rate until the coefficient of...

Control apparatus and method of internal combustion engine

Abstract: A control apparatus of an internal combustion engine performs control to warn- up a catalyst. More specifically, the control apparatus keeps a wastegate valve (WGV) open when the temperature of the catalyst is less than a predetermined temperature and closes the wastegate valve (WGV) when the temperature of the catalyst becomes equal to or greater than the predetermined temperature. The control apparatus executes control to increase and decrease the fuel injection quantity such that the internal combustion engine alternately switches between lean burn and rich burn when the wastegate valve is closed. Accordingly, rich gas and lean gas can be reliably mixed in the catalyst, and CO can be reliably combusted in the catalyst. Therefore, the catalyst can be promptly warmed up while CO, HC, and the like can be appropriately suppressed from flowing through the catalyst.

Experimental Study on the Operating Range Restrictions of a Lean-burn Turbocharged SI Natural Gas Engine

Abstract: An experimental investigation aiming at extending the operating range of lean-burn turbocharged spark-ignition (SI) CNG engine was conducted on a six-cylinder throttle body injection CNG engine. Cylinder pressure was recorded by using a high sampling frequency transducer, thus allowing the analysis of pressure characteristics introduced by knock. Coefficient of variations (COV) in indicated mean effective pressure (IMEP) was used to define lean misfire. The effects of various engine parameters on an engine’s lean burn capability, knock limit, and preturbo temperature limit were examined at various operating conditions. The results indicate that a lean-burn SI CNG engine’s operating range is sensitively affected by the mechanical structure of the engine, excess air ratio, spark timing, load, engine speed, intake temperature, ambient humidity, etc. For the turbocharged engine, preturbo temperature is also a key consideration in extending the operating range of the engine.