Showing papers on "Lean burn published in 2008"

Development of Lean-Burn Low-NOx Combustion Technology at Rolls-Royce Deutschland

Abstract: Lean-burn combustion technology is identified to be the key technology for aero-engine combustion systems to achieve future legislative requirements for NOx. The lean-burn low NOx combustor development at Rolls-Royce Deutschland RRD for the upcoming generation of aero-engines is presented, which has been supported by the German aeronautical research programme. The down selection process of different injector concepts is described in detail to develop lean-burn fuel injection technology up to a technology level for engine application. Initial concept validation with testing on single sector combustion rigs applying advanced laser measurement techniques is followed by high power single sector emission tests to prove low emission characteristics. Climbing the level of technology readiness, which is in each phase substantiated by intense CFD simulations, the most promising low emissions design concepts have been investigated for unrestricted combustor operability compared to conventional rich burn systems. Altitude relight, weak extinction margins, fuel staging optimisation and combustion efficiency in the vicinity of staging points have been optimised on different sub-atmospheric, atmospheric, medium and high-pressure test vehicles. The validation process concludes with sub-atmospheric and high-pressure testing within a fully annular test environment before the final lean-burn fuel injector configuration has been selected for core engine testing to prove emission performance and operability of the fuel-staged combustion system. Two fuel injector configurations were successfully tested in a high-pressure fully annular rig. The combustor module and both injector standards have been cleared for core engine operation.Copyright © 2008 by Rolls Royce Ltd. & Co. KG

Experimental Study on Emissions of a Spark-Ignition Engine Fueled with Natural Gas-Hydrogen Blends

Abstract: An experimental investigation on the influence of the excess air ratio and hydrogen fraction on the emissions characteristics of a spark-ignition engine fueled with natural gas−hydrogen blends was conducted. The results indicate that the excess air ratio has a significant effect on the hydrocarbon (HC), NOx, CO, and CO2 concentration for both pure natural gas and natural gas−hydrogen blends. For a specified excess air ratio, HC emissions decrease with the increase of hydrogen fraction; the behavior is more obvious under the lean burn operation. The NOx concentration increases with the increase of hydrogen fraction, and NOx gets its peak value at an excess air ratio of 1.1. CO2 emissions decrease with increasing hydrogen fraction. Meanwhile, the addition of hydrogen into natural gas can extend the lean burn limit of a mixture. Thus, an engine fueled with natural gas−hydrogen blends operating under lean mixture conditions can get low emissions of HC, CO, CO2, and NOx.

Combustion and emission characteristics of a lean burn natural gas engine

Abstract: Lean burn is an effective way to improve spark ignition engine fuel economy. In this paper, the combustion and emission characteristics of a lean burn natural gas fuelled spark ignition engine were investigated at various throttle positions, fuel injection timings, spark timings and air fuel ratios. The results show that ignition timings, the combustion duration, the coefficient of variation (COV) of the indicated mean effective pressure (IMEP) and engine-out emissions are dependent on the overall air fuel ratio, spark timings, throttle positions and fuel injection timings. With the increase of the air fuel ratio, the ignition delays and combustion duration increases. Fuel injection timings affect ignition timings, combustion duration, IMEP, and the COV of the IMEP. Late fuel injection timings can decrease the COV of the IMEP. Moreover, the change in the fuel injection timings reduces the engine-out CO, total hydrocarbon (THC) emissions. Lean burn can significantly reduce NOx emissions, but it results in high cyclic variations.

Study on cycle-by-cycle variations of combustion in a natural-gas direct-injection engine:

Abstract: In this paper, the cycle-by-cycle variations of a compressed-natural-gas (CNG) direct-injection (DI) engine were investigated. The results show that the CNG DI engine has a better lean burn capability, and misfire cycles and partial burn cycles exist when the engine operates at small equivalence ratio (w ,0.4). Meanwhile, the indicated mean effective pressure (IMEP) has a low value, and the high value of the coefficient of variation in the IMEP is presented in comparison with those operating at a high equivalence ratio. Cycles with a high maximum cylinder pressure correspond to the cycles of fast burning, and parameter interdependence is observed between the maximum cylinder gas pressure and its correspond- ing crank angle, between the maximum rate of pressure rise and its corresponding crank angle, and between the maximum cylinder pressure and the indicated mean effective pressure. Better parameter interdependence exists between the maximum cylinder pressure and the flame- developing period, between the maximum cylinder pressure and the rapid-burning period, and between the accumulated heat release amount per cycle and the indicated mean effective pressure. A small variation in the flame-developing duration will lead to a large variation in the rapid-burning duration under lean mixture combustion; the slow flame propagation speed of the lean mixture combustion is considered to lead to this phenomenon.

The Engine 3E Core Engine

Abstract: Engine 3E is the aero engine part of the German Aeronautics Research Program under which Rolls-Royce Deutschland developed key technologies for an all new core engine that incorporates major advances with regard to environmental friendliness, efficiency and economy. The derived E3E core engine will serve as a scalable baseline for the future two-shaft engine family in the medium take-off thrust range between 12 – 40 klb. The core consists of a highly loaded 9-stage HPC, a lean burn combustion chamber with internal fuel staging and a 2-stage shroudless HPT. On the basis of its high specific power, low NOx combustion and low manufacturing cost, it will enable significant improvements in SFC, emissions, unit cost and weight. The related technology demonstrator is currently in the final build and instrumentation phase for testing in an altitude test facility in first quarter 2008.Copyright © 2008 by Rolls-Royce Ltd & Co KG

Lean-Burn Stationary Natural Gas Reciprocating Engine Operation With a Prototype Fiber Coupled Diode End Pumped Passively Q-Switched Laser Spark Plug

Abstract: To meet the ignition system needs of large bore lean burn stationary natural gas engines a laser diode side pumped passively Q-switched laser igniter was developed and used to ignite lean mixtures in a single cylinder research engine. The laser design was produced from previous work. The in-cylinder conditions and exhaust emissions produced by the miniaturized laser were compared to that produced by a laboratory scale commercial laser system used in prior engine testing. The miniaturized laser design as well as the combustion and emissions data for both laser systems was compared and discussed. It was determined that the two laser systems produced virtually identical combustion and emissions data.

Control device of an internal combustion engine

Abstract: The control device of the internal combustion engine appropriately controls plural exhaust valves to effectively perform sulfur poisoning recovery in an exhaust gas purifying catalyst. The control device controls the internal combustion engine which performs lean burn. The exhaust system of the internal combustion engine includes: first exhaust valves and second exhaust valves provided in each of the plural cylinders; a first exhaust passage communicating with the first exhaust valves; a second exhaust passage communicating with the second exhaust valves; a first exhaust gas purifying catalyst provided at least one of the first exhaust passage and the second exhaust passage; and a second exhaust gas purifying catalyst provided on an exhaust passage downstream of a junction of the first exhaust passage and the second exhaust passage. The control means controls the exhaust valves such that an effect of rich combustion occurs more to the second exhaust gas purifying catalyst than to the first exhaust gas purifying catalyst, when performing rich combustion. By this, the consumption of the exhaust gas in the first exhaust gas purifying catalyst can be suppressed, and the temperature of the second exhaust gas purifying catalyst can be effectively risen. Therefore, the sulfur poisoning recovery and the like can be effectively performed.

Introduction and Perspectives

Abstract: Publisher Summary Studies of lean combustion are among the oldest in the combustion literature because its extreme represents the lean limit of inflammability, which has been a well-recognized hazard marker from the inception of combustion science. Lean combustion was considered only with regard to explosion hazards until the late 1950s, when lean flames were introduced as useful diagnostic tools for identifying detailed reaction behavior. This chapter presents the foundations of lean combustion including the roles of turbulence, flame front instabilities, and flame speed in controlling the robustness of the reaction. Lean combustion is employed in nearly all combustion technology sectors, including gas turbines, boilers, furnaces, and internal combustion (IC) engines. This wide range of applications attempts to take advantage of the fact that combustion processes operating under fuel lean conditions can have very low emissions and very high efficiency. Pollutant emissions are reduced because flame temperatures are typically low, reducing thermal nitric oxide formation. In addition, for hydrocarbon combustion, when leaning is accomplished with excess air, complete burnout of fuel generally results, reducing hydrocarbon and carbon monoxide (CO) emissions. Unfortunately, achieving these improvements and meeting the demands of practical combustion systems is complicated by low reaction rates, extinction, instabilities, mild heat release, and sensitivity to mixing.

Lean Hydrogen Combustion

Abstract: Publisher Summary This chapter discusses lean-burn hydrogen combustion in gas turbines and reciprocating IC engines. It explains that while utilizing hydrogen fuel poses some challenges, operating hydrogen combustion engines have already been demonstrated. The special features of hydrogen for lean burn include its high flame speed, low flammability limit, high mass-specific energy content, lack of carbon, and high molecular diffusivity. These properties, when properly exploited, can enhance flame stability at the low temperatures capable of limiting NOx formation and, depending on the source of the hydrogen, reduce or eliminate the emission of the greenhouse gas carbon dioxide. With these benefits come some significant challenges including compact fuel storage, potential explosion hazards, pre-ignition limited peak power in IC engines, and autoignition and flashback in gas turbines. This chapter discusses some advanced engine concepts for overcoming these challenges and ends with the optimistic view that lean hydrogen combustion could, with relatively little effort, provide an effective bridge to future carbon neutral fuel scenarios. The use of hydrogen in two applications, ICEs and gas turbine combustion systems, is also described in the chapter. In both of these applications lean premixed combustion technology using hydrogen-based fuels has already been successfully demonstrated.

Determination of Lean Burn Combustion Temperature Using Ultraviolet Emission

Abstract: Measurements of the ultraviolet emission spectrum emitted from a lean burn premixed natural gas flame were taken over a range of flame temperatures using a fiber-optic/CCD spectrometer. Combustion temperatures were determined by two methods: by measuring the unburned oxygen in the exhaust and by calculating the temperature using the fuel and airflows. These temperatures were correlated to ratios composed of the integrated intensity of the long wavelength region of the OH band between 310 to 340 nm (ratio's numerator) and that between 305 and 310 nm (ratio's denominator). Average local combustor flame temperatures at the end of the combustion zone may then be determined by tracking these ratios during combustor operation. The sensitivity of these ratios yields a 0.8% change in the ratios every 20 degF with a precision of plusmn30 degF or plusmn1% at 3000 degF with 95 % confidence bounds demonstrating the feasibility of this technique for use as a potential control parameter for gas turbine combustors burning natural gas and air mixtures. This method is well suited for the low equivalence ratios (< 1) required to reduce NOx and CO emissions. Other methods using peak ratios of different emission bands exhibit nonlinearity, lower sensitivity and greater uncertainty.

Method and system for closed loop combustion control of a lean-burn reciprocating engine using ionization detection

Abstract: A system and method for controlling knock in a lean burn internal combustion (IC) engine includes a spark plug having an electrode, and an electrical circuit configured to provide a first voltage to the electrode and detect an ion current during a thermal-ionization phase of the combustion process, and provide a second voltage to the electrode to create a spark and initiate a combustion process within a combustion chamber. The engine includes a controller configured to monitor the ion current for a knock condition that includes at least an incipient knock condition, determine a spark crank angle timing of the IC engine where the incipient knock occurs, and adjust the spark timing of the IC engine to operate at a crank angle that does not exceed a threshold level beyond an incipient knock set point.

SCR-LNT CATALYST COMBINATION FOR IMPROVED NOx CONTROL OF LEAN GASOLINE AND DIESEL ENGINES

Abstract: An aftertreatment system for use in a lean burn engine is disclosed. In one embodiment, the aftertreatment system includes a first catalyst in communication with an exhaust stream from the engine; a selective catalytic reduction catalyst in communication with the exhaust stream and positioned downstream of the first catalyst; and a lean NO x trap in communication with the exhaust stream and positioned downstream of the selective catalytic reduction catalyst; with the proviso that the first catalyst is not a selective catalytic reduction catalyst. A method for treating lean burn engine exhaust gases using the aftertreatment system is also disclosed.

Lean-Burn Spark-Ignited Internal Combustion Engines

Abstract: Transportation accounts for approximately 25% of total energy consumption in most industrialized countries, and since the fuel comes entirely from fossil fuels this represents an even greater proportion of total greenhouse gas emissions. In addition to greenhouse gas emissions, the emission of unburned hydrocarbons (HCs), particulate matter, and nitrogen oxides from transportation sources are of particular concern because they are released primarily in heavily populated areas, resulting in poor urban air quality. Improving the efficiency of internal combustion engines, therefore, as well as reducing the level of pollutant emissions, is of great interest for both light- and heavy-duty vehicles. Modern light- and medium-duty vehicles with spark-ignited engines are equipped with three-way catalytic converters which are very effective in reducing the output of unburned HCs, carbon monoxide, and nitrogen oxides. Medium- and heavyduty vehicles usually employ diesel engines, and although these may be fitted with an oxidation catalyst to reduce carbon monoxide and unburned HCs, they do not affect the high level of nitrogen oxide emissions produced by these engines. There is a need, therefore, for improved engine technology which addresses the need both to increase thermal efficiency, and reduce engine-out emissions from these vehicles. As seen in Chapter 2, one way to simultaneously increase efficiency and reduce emissions is to use spark-ignited engines which operate with an air–fuel mixture that is much leaner than the normal stoichiometric mixture used in most such engines. This “lean-burn” strategy is particularly effective for reducing nitrogen oxide emissions since these are very temperature dependent, and lean mixtures burn with a lower flame temperature due to the heat sink provided by the excess air. Thermal efficiency is also increased with lean combustion, since the ratio of specific heats increases monotonically with excess air ratio. The efficiency of lean-burn spark-ignition engines during part-load operation is further increased compared to stoichiometric-charge engines, since a greater throttle opening is required to achieve a given power output. This larger throttle opening reduces the “pumping losses” inherent in any engine operating with a partly closed throttle.

Experimental Examination of Prechamber Heat Release in a Large Bore Natural Gas Engine

Abstract: A common solution in reducing NOx emissions to meet new emission regulations has been lean burn combustion. However, with very lean air∕fuel (A∕F) ratios, both carbon monoxide and hydrocarbon emissions become unacceptably high due to the spark misfiring and combustion instabilities. In order to mitigate this, a prechamber ignition system is often used to stabilize combustion at very lean A∕F ratios. In this paper, the heat release in a retrofit prechamber system installed on a large bore natural gas engine is examined. The heat release analysis is based on dynamic pressure measurements both in the main chamber and prechamber. The Woschni correlation is utilized to model heat transfer. Based on heat release modeling and test data analysis, the following observations are made. Main chamber heat release rates are much more rapid for prechamber ignition compared to spark ignition. During combustion in the prechamber, much of the fuel flows into the main chamber unreacted. About 52% of the mass in the prechamber, at ignition, flows into the main chamber during prechamber combustion. Prechamber total heat release, pressure rise, and maximum jet velocity all increase with increasing prechamber equivalence ratio. Prechamber combustion duration and coefficient of variation of peak pressure are minimized at a prechamber equivalence ratio of about 1.09.

Exhaust gas cleaning apparatus for lean burn internal combustion engine

Abstract: An exhaust gas cleaning apparatus includes a LNT, a fuel adding device, an exhaust gas returning passage, and a controller. The LNT is provided in an exhaust gas passage of an engine. The fuel adding device is located upstream of the LNT to add fuel to exhaust gas flowing through the exhaust pipe. The exhaust gas returning passage branches off from the exhaust gas passage at a position downstream of the fuel adding device. The controller controls the apparatus to selectively operate in one of first and second modes according to the operating condition of the engine. In the first mode, the fuel adding device adds the fuel to the exhaust gas with the exhaust gas returning passage closed; in the second mode, the exhaust gas is partially returned to an intake air passage through the exhaust gas returning passage without the fuel being added by the fuel adding device.

DUAL BED CATALYST SYSTEM FOR NOx REDUCTION IN LEAN-BURN ENGINE EXHAUST

Abstract: A method for reducing nitrogen oxides including NO and NO 2 in an exhaust stream also including oxygen, carbon monoxide and hydrocarbons at a temperature above about 150° C. includes oxidizing NO in the exhaust stream to NO 2 , adding diesel fuel hydrocarbons and their oxygenates to the exhaust stream for the reduction of nitrogen oxides, and flowing the exhaust stream through a dual bed catalyst system including a first bed and a second bed, wherein the first bed is a single layer catalyst bed and the second bed is a double layer catalyst bed including a first layer and a second layer to reduce the nitrogen oxides to N 2 .

카뷰레터 니들 밸브를 이용한 26cc 소형원동기의 희박 연소 특성

Abstract: This paper presents the effects of access air factors and throttle open degrees on the performance of a small spark-ignition gasoline engine The engine used in this paper was a single cylinder, diaphragm carburetor, two-stroke, air-cooled 26cc engine for brush cutter The rpm, torque, fuel consumption and HC, CO, NOx emission were measured under lean burn conditions on the opened area ratios and engine loads respectively The results showed that the maximum power and minimum fuel consumption could be obtained leaner mixture tuning decreases HC and CO emission

Low Temperature Combustion Using Nitrogen Enrichment to Mitigate NOx From Large Bore Natural Gas Fueled Engines

Abstract: Low Temperature Combustion (LTC) is identified as one of the pathways to meet the mandatory ultra low NOx emissions levels set by regulatory agencies. This phenomenon can be realized by utilizing various advanced combustion control strategies. The present work discusses nitrogen enrichment using an Air Separation Membrane (ASM) as a better alternative to the mature Exhaust Gas Re-circulation (EGR) technique currently in use. A 70% NOx reduction was realized with a moderate 2% nitrogen enrichment while maintaining power density and simultaneously improving Fuel Conversion Efficiency (FCE). The maximum acceptable Nitrogen Enriched Air (NEA) in a single cylinder spark ignited natural gas engine was investigated in this paper. Any enrichment beyond this level degraded engine performance both in terms of power density and FCE, and unburned hydrocarbon (UHC) emissions. The effect of ignition timing was also studied with and without N2 enrichment. Finally, lean burn versus stoichiometric operation utilizing NEA was compared. Analysis showed that lean burn operation along with NEA is one of the effective pathways for realizing better FCE and lower NOx emissions.Copyright © 2008 by UChicago Argonne LLC, Operator of Argonne National Laboratory

Control unit of internal combustion engine

Abstract: The control device of the internal combustion engine appropriately controls plural exhaust valves to effectively perform sulfur poisoning recovery in an exhaust gas purifying catalyst. The control device controls the internal combustion engine which performs lean burn. The exhaust system of the internal combustion engine includes: first exhaust valves and second exhaust valves provided in each of the plural cylinders; a first exhaust passage communicating with the first exhaust valves; a second exhaust passage communicating with the second exhaust valves; a first exhaust gas purifying catalyst provided at least one of the first exhaust passage and the second exhaust passage; and a second exhaust gas purifying catalyst provided on an exhaust passage downstream of a junction of the first exhaust passage and the second exhaust passage. The control means controls the exhaust valves such that an effect of rich combustion occurs more to the second exhaust gas purifying catalyst than to the first exhaust gas purifying catalyst, when performing rich combustion. By this, the consumption of the exhaust gas in the first exhaust gas purifying catalyst can be suppressed, and the temperature of the second exhaust gas purifying catalyst can be effectively risen. Therefore, the sulfur poisoning recovery and the like can be effectively performed.

Lean-burn operation for natural gas/air mixtures: the dual-fuel engines

Abstract: The research activity on internal combustion engines is increasingly cast to find an alternative solution to reduce the wide utilization of petroleum fuels like diesel oil and gasoline, for environmental, political and economic concerns. Natural gas (NG) is an ideal fuel to be operated in internal combustion engines, since its characteristics allow for much lower environmental impact and reduced fuel consumption with respect the conventional fuels. It also is particularly suitable to be operated under high volumetric compression ratio engines, thus providing higher efficiency, and moreover it is characterized by a wide flammability range. This latter aspect promotes the employment of a lean burn strategy, thus further increasing the engine efficiency and reducing the exhaust emissions. The dual-fuel natural gas/diesel concept allows extending the lean flammability limit of NG with respect to SI-NG operations and simultaneously reducing the NOX-PM trade-off affecting diesel combustion. Such a technology consists in introducing NG as main fuel in a conventional diesel engine. A certain amount of diesel pilot injection is preserved to act as the ignition source for the air/NG mixture. The easiness of dual-fuel conversion makes such technology rather inviting especially as a retrofit for the existing diesel vehicles, which could not meet the more and more stringent emission regulations in the future. In the present study, the dual-fuel combustion process with its inherent complexity is investigated both from an experimental and a numerical point of view. The experimental activity has the main target to analyze the problems connected with the conversion of a heavy-duty diesel engine to dual-fuel operation, and to put into evidence the influence of the main engine parameters on performance and pollutants formation. The numerical activity, characterized by a mixed 1-D/3-D approach, has been carried out with the initial target of a correct understanding of the complex dual-fuel combustion mechanism. A detailed multi-dimensional simulation of the whole working cycle of the engine has been subsequently performed, to provide for the correct representation of the fluid-dynamic effect involved in dual-fuel operations. Such an approach allows for the complete description of the engine overall behavior and the dual-fuel combustion in detail.

Emission Characteristic of Turbocharged Lean Burn CNG Engine

Abstract: In order to study emission characteristic of turbocharged lean burn CNG engine,an experimental research was conducted to examine the influence of the air fuel ratio,ignition timing and the oxidation catalyst converter on the emission characteristic.The result shows that NOx emissions increase initially and then decrease,but NMHC emissions decrease initially and increase as the air fuel ratio increases.Additionally the NOx emissions decrease initially and then increase as the engine speed increases.The lowest NOx emission value occures for 1600~1800r/min.Under the constant manifold absolute pressure,with increase of ignition advanced angle,NMHC emissions decrease initially and then increase,NOx emissions increase.After installing the I type oxidation catalyst converter,NOx,CH4,CO and NMHC emissions are reduced by 15%,97%,78% and 60% respectively.The result shows turbocharging lean burn in combination of oxidation catalyst converter is an effective technical way for CNG engine.

Transient lean burn air-fuel ratio linear parameter-varying control using input shaping

Abstract: Transient air-fuel ratio control for lean burn engines is essential to achieve improved fuel economy and strict federal emission regulations. Unlike conventional Spark Ignition (SI) engines, lean burn engines are no longer operating in a narrow band around stoichiometric resulting in a very challenging air-fuel ratio tracking problem. An approach to combine an input shaping method together with Linear Parameter Varying (LPV) feedback control is proposed in this paper to solve the transient air-fuel ratio tracking problem. LPV air-fuel ratio control has been shown to regulate the air-fuel ratio at steady state engine operating conditions, reduce the variability of the closed-loop system, reject disturbance and guarantee robustness and stability in the presence of variable time delays. In this paper, an input shaping method is used to reduce the cost of feedback, and thereby enhance the air-fuel ratio tracking performance during engine transient operations. The prefilter is designed based on the closed-loop dynamics resulting from the LPV design. A systematic input shaping prefilter design process is developed. The designed prefilter successfully extends the closed-loop air-fuel ratio tracking bandwidth. Simulation results using Federal Test Procedure (FTP) drive cycle data are used to demonstrate the effectiveness of the input shaping prefilter. Moreover, the designed prefilter is structurally simple and computationally efficient.