Showing papers on "Lean burn published in 2012"

A Lean Burn Gasoline Fueled Pre-Chamber Jet Ignition Combustion System Achieving High Efficiency and Low NOx at Part Load

Abstract: Turbulent Jet Ignition is an advanced spark initiated pre‐chamber combustion system for otherwise standard spark ignition engines. Combustion in the main chamber is initiated by jets of partially combusted (reacting) pre‐chamber products which provide a high energy ignition source. The resultant widely distributed ignition sites allow relatively small flame travel distances enabling short combustion durations and high burn rates. Demonstrated benefits include ultra lean operation (λ>2) at part load and high load knock limit extension. Previous jet ignition experimental results have highlighted high thermal efficiencies, high load capability and near zero engine out NOx emissions in a standard contemporary engine platform. Although previous results of this system have been very promising, the main hurdle has been the need for a dual fuel system, with liquid gasoline used in the main combustion chamber and small fractions of gaseous propane in the pre‐chamber. Initial attempts in replacing the pre‐chamber gaseous propane with liquid gasoline were problematic, although engine operation was successful at some operating conditions. The poor mixture preparation with liquid gasoline inside the small pre‐ chamber cavity due to the limited production injector hardware somewhat compromised the thermal efficiency, resulting in slight elevations in NOx emissions. Since specialized pre‐chamber injector hardware was not available for evaluation, the purpose of this paper is to demonstrate that this combustion system can operate robustly using gasoline, with vaporized gasoline found to be a successful pre‐chamber fuel substitute. With this concept at part load, the test engine recorded a 41.4% peak thermal efficiency, ultra lean operation past lambda 2.1, single digit engine out NOx emissions and a 20% peak fuel economy improvement over the baseline spark ignition system.

NOx storage and reduction in lean burn vehicle emission control: a catalytic engineer's playground

Abstract: The reduction of NOx (NO + NO2) in lean burn vehicle exhaust is the latest challenge for catalytic engineers to meet increasingly stringent emissions standards. The lean NOx trap (LNT) is an adsorptive catalytic reactor in which NOx is stored as nitrates in excess O2 and then reduced during a brief regeneration. The multi-functional Pt-based LNT catalyst must carry out NO oxidation, NOx storage, and NOx reduction, all within a 1–2 min cycle and achieve >95% NOx conversion. This review describes studies of the transient coupling between reaction and transport, and links between catalyst composition, structure, NOx conversion, and selectivity to N2 and NH3. A glimpse is offered of emerging lean NOx reduction technologies and the new challenges they pose.

Premixed Combustion Under Electric Field in a Constant Volume Chamber

Abstract: The effects of electric fields on outwardly propagating premixed flames in a constant volume chamber were experimentally investigated. An electric plug, subjected to high electrical voltages, was used to generate electric fields inside the chamber. To minimize directional ionic wind effects, alternating current with frequency of 1 kHz was employed. Lean and rich fuel/air mixtures for both methane and propane were tested to investigate various preferential diffusion conditions. As a result, electrically induced instability showing cracked structure on the flame surface could be observed. This cracked structure enhanced flame propagation speed for the initial period of combustion and led to reduction in flame initiation and overall combustion duration times. However, by analyzing pressure data, it was found that overall burning rates are not much affected from the electric field for the pressurized combustion period. The reduction of overall combustion time is less sensitive to equivalence ratio for methane/air mixtures, whereas the results demonstrate pronounced effects on a lean mixture for propane. The improvement of combustion characteristics in lean mixtures will be beneficial to the design of lean burn engines. Two hypothetical mechanisms to explain the electrically induced instability were proposed: 1) ionic wind initiated hydrodynamic instability and 2) thermodiffusive instability through the modification of transport property such as mass diffusivity.

Platinum group metal (pgm) catalyst for treating exhaust gas

Abstract: Provided are catalysts comprising a small pore molecular sieve embedded with platinum group metal (PGM) and methods for treating lean burn exhaust gas using the same.

Lean Combustion Technology for Internal Combustion Engines: a Review

Abstract: Lean burn is an effective way to improve spark ignition engine fuel economy. Lean combustion is generally considered as a timely solution to the more stringent environmental regulations and global weather concerns in the new era. However, the instability associated with the lean flame significantly keeps the lean combustion technique from being widely accepted as a major combustion technique for general applications. A comprehensive study has been made in this report on the investigations of various researchers and research organizations on the lean combustion technology as well as to give a review of the work which has recently been performed in the area of lean combustion.

Simultaneous NOx and hydrocarbon emissions control for lean-burn engines using low-temperature solid oxide fuel cell at open circuit.

Abstract: The high fuel efficiency of lean-burn engines is associated with high temperature and excess oxygen during combustion and thus is associated with high-concentration NOx emission. This work reveals that very high concentration of NOx in the exhaust can be reduced and hydrocarbons (HCs) can be simultaneously oxidized using a low-temperature solid oxide fuel cell (SOFC). An SOFC unit is constructed with Ni–YSZ as the anode, YSZ as the electrolyte, and La0.6Sr0.4CoO3 (LSC)–Ce0.9Gd0.1O1.95 as the cathode, with or without adding vanadium to LSC. SOFC operation at 450 °C and open circuit can effectively treat NOx over the cathode at a very high concentration in the simulated exhaust. Higher NOx concentration up to 5000 ppm can result in a larger NOx to N2 rate. Moreover, a higher oxygen concentration promotes NO conversion. Complete oxidation of HCs can be achieved by adding silver to the LSC current collecting layer. The SOFC-based emissions control system can treat NOx and HCs simultaneously, and can be operat...

Lean Burn Performance of a Natural Gas Fuelled, Port Injected, Spark Ignition Engine

Abstract: This paper presents a study of the performance of a lean burn, natural gas fuelled, naturally aspirated, spark ignition engine for an E class vehicle. Engine performance and exhaust emissions (NO, CO, and UHC) data are first discussed. An energy balance of the engine operating at different loads and air-fuel ratios is then presented, and used to explain why engine efficiency varies with air-fuel ratio. Finally, the hot start drive cycle CO2e (CO2 equivalent) emissions are estimated for a vehicle with this engine. This shows a potential for significant reduction in vehicle greenhouse gas emissions compared to an equivalent gasoline fuelled vehicle. Copyright © 2012 SAE International.

Exhaust system including nox reduction catalyst and egr circuit

Abstract: An exhaust system for a vehicular lean burn internal combustion engine that emits oxides of nitrogen (NOx) and particulate matter (PM) is disclosed. The system comprises a NOx reduction catalyst for reducing NOx in the presence of a reductant, means for introducing reductant into a flowing exhaust gas and a source of hydrocarbon reductant, a nitrogenous reductant, and/or hydrogen, a filter for removing PM from exhaust gas flowing in the exhaust system and a low pressure exhaust gas recirculation (EGR) circuit for connecting the exhaust system downstream of the filter to an air intake of the engine. The EGR circuit comprises a IMOx adsorber catalyst (NAC) comprising a NO adsorbent.

Exhaust system having ammonia slip catalyst and egr circuit

Abstract: An exhaust system for a vehicular lean burn internal combustion engine that emits oxides of nitrogen (NOx) and particulate matter (PM) is disclosed. The system comprises a NOx reduction catalyst for reducing NOx in the presence of a nitrogenous reductant, means for introducing the nitrogenous reductant into a flowing exhaust gas, a filter for removing PM from exhaust gas flowing in the exhaust system and a low pressure exhaust gas recirculation (EGR) circuit for connecting the exhaust system downstream of the filter to an air intake of the engine. The EGR circuit comprises an ammonia oxidation catalyst.

Supported noble metal catalyst for treating exhaust gas

Abstract: Provided is a method for oxidizing short-chain saturated hydrocarbons in a lean burn exhaust gas, the method involving contacting the exhaust gas with a palladium or palladium/platinum catalyst disposed on a rare-earth stabilized zirconia support.

Effect of Engine Exhaust Parameters on the Hydrothermal Stability of Hydrocarbon-Selective Catalytic Reduction (SCR) Catalysts for Lean-Burn Systems

Abstract: A dual-catalyst bed composed of a reduction catalyst, Pd-sulfated zirconia, and an oxidation catalyst, CoOx/CeO2, was investigated for selective catalytic reduction (SCR) of NOx (NO and NO2) by hydrocarbons for use in lean-burn natural gas engines. The primary focus of this submission is to examine the hydrothermal stability of the dual-catalyst bed and improve its hydrothermal durability by studying the effect of the engine exhaust parameters. The main parameters investigated were the concentration and nature of the hydrocarbons and the reaction temperature. Both cyclic as well as time-on-stream experiments were conducted under various engine exhaust compositions and different reaction temperatures to establish the conditions that could improve the water tolerance of the dual-catalyst bed. The higher concentration of the hydrocarbon mixture in the simulated engine exhaust was seen to assist the water tolerance of the dual-catalyst bed. Experiments were performed to isolate and identify the primary compon...

Process for the reduction of nitrogen oxides and sulphur oxides in the exhaust gas from internal combustion engine

Abstract: Method for reducing oxides of nitrogen and sulphur in exhaust gas from a lean burn internal combustion engine

Development and Analysis of a Controlled Hot Surface Ignition System for Lean Burn Gas Engines

Abstract: Spark ignition constitutes the most common way of mixture inflammation for gas engines of CHP units (combined heat and power). However, spark plug durability is limited due to spark erosion. High maintenance costs as a result of frequent spark plug replacements are the consequence. Beside the durability aspect, the inflammation of lean mixtures makes high demands on the inflammation process itself. Due to the small reactive mixture volume, the level of air-fuel ratio as well as the efficiency increase is limited. The ignition by means of a hot surface enables an increase of the reactive mixture volume and, as a result, an enhancement of the lean burn limit.A hot surface ignition (HSI) system was developed for stationary lean burn operation in due consideration of low manufacturing costs and electrical characteristics that allow a reliable control of the ignition timing. The main component of the inflammation element is a pin-shaped glow plug, whose temperature can be regulated by adjusting the electrical power. Due to external influences such as fluctuating ambient pressure and gas quality a control unit is essential for securing an optimal combustion phasing of the engine.Several designs of hot surface ignition, including passive prechamber and shielded versions, were tested on a single cylinder test bed engine operating with a homogeneous air-petrol mixture. The engine tests were accompanied by 3D flow simulations. The trials showed that the power consumption, and hence the temperature of the hot surface, as well as the flow conditions around the glow plug have a strong influence on the ignition timing. Furthermore, a strong correlation between the mean combustion chamber temperature and combustion phasing became evident. Based on this coherence, it was possible to develop a closed-loop control that adjusts the combustion phasing by controlling the combustion chamber temperature at a stationary operating point.The shielded inflammation element stood out to be the target-aiming version of hot surface ignition. It is characterised by an accelerated inflammation which allows reducing the cycle-to-cycle variations compared to prechamber spark ignition and, hence, to enhance the lean burn limit. As a result, a significant improvement of the efficiency-NOx trade-off is possible.The obtained results provide the basis for further trials on a gas engine CHP module operating with natural gas.Copyright © 2012 by ASME

A Reduced Chemical Kinetic Mechanism for CFD Simulations of High BMEP, Lean-Burn Natural Gas Engines

Abstract: Recent developments in numerical techniques and computational processing power now permit time-dependent, multi-dimensional computational fluid dynamic (CFD) calculations with reduced chemical kinetic mechanisms (approx. 20 species and 100 reactions). Such computations have the potential to be highly effective tools for designing lean-burn, high BMEP natural gas engines that achieve high fuel efficiency and low emissions. Specifically, these CFD simulations can provide the analytical tools required to design highly optimized natural gas engine components such as pistons, intake ports, precombustion chambers, fuel systems and ignition systems. To accurately model the transient, multi-dimensional chemically reacting flows present in these systems, chemical kinetic mechanisms are needed that accurately reproduce measured combustion data at high pressures and lean conditions, but are of sufficient size to enable reasonable computational times. Presently these CFD models cannot be used as accurate design tools for application in high BMEP lean-burn gas engines because existing detailed and reduced mechanisms fail to accurately reproduce experimental flame speed and ignition delay data for natural gas at high pressure (40 atm and higher) and lean (0.6 equivalence ratio (ϕ) and lower) conditions. Existing methane oxidation mechanisms have typically been validated with experimental conditions at atmospheric and intermediate pressures (1 to 20 atm) and relatively rich stoichiometry. These kinetic mechanisms are not adequate for CFD simulation of natural gas combustion in which elevated pressures and very lean conditions are typical. This paper provides an analysis, based on experimental data, of the laminar flame speed computed from numerous, detailed chemical kinetic mechanisms for methane combustion at pressures and equivalence ratios necessary for accurate high BMEP, lean-burn natural gas engine modeling. A reduced mechanism that was shown previously to best match data at moderately lean and high pressure conditions was updated for the conditions of interest by performing sensitivity analysis using CHEMKIN. The reaction rate constants from the most sensitive reactions were appropriately adjusted in order to obtain a better agreement at high pressure lean conditions. An evaluation of this adjusted mechanism, “MD19”, was performed using Converge CFD software. The results were compared to engine data and a remarkable improvement on combustion performance prediction was obtained with the MD19 mechanism.Copyright © 2012 by ASME

Experimental investigation of the effects of hydrogen enhanced combustion in si and ci engines on performance and emissions

Abstract: Hydrogen enhanced combustion (HEC) is promoted as an end-user add-on that has the capability of reducing both engine tailpipe emissions and fuel consumption. An experimental investigation was carried out to measure the effect s of HEC in typical engines through laboratory dynamometer test ing. Three engines ‐ (1) a carburetted petrol engine, (2) a fu el injected petrol engine and (3) a diesel engine ‐ were tested to investigate the effects of adding hydrogen to the a ir intake of the engines and measure the effects on performance and emissions (HC, CO and CO 2). The engines were tested at different engine speeds and loads to simulate a wid e range of operating conditions. The hydrogen was produced from the electrolysis of a solution of distilled water and s odium hydroxide using two different electrolyser designs. The electrolyser constructions were suitable for automo tive applications, that is, small in size and consuming current within the capability of a typical car alternator. Both th e hydrogen and oxygen that were produced by electrolysis were adde d to the engine‘s intake during the tests. Results showed th at the addition of HHO is most effective in stabilizing an d enhancing the combustion of lean air-fuel mixtures inside the petrol injected engine, allowing for lower HC, CO and CO2 emissions. Thus hydrogen enhanced combustion could play a role in stabilizing lean burn petrol engines.

The Impact of Compressor Exit Conditions on Fuel Injector Flows

Abstract: This paper examines the effect of compressor generated inlet conditions on the air flow uniformity through lean burn fuel injectors Any resulting nonuniformity in the injector flow field can impact on local fuel air ratios and hence emissions performance The geometry considered is typical of the lean burn systems currently being proposed for future, low emission aero engines Initially, Reynolds-averaged Navier-Stokes (RANS) computational fluid dynamics (CFD) predictions were used to examine the flow field development between compressor exit and the inlet to the fuel injector This enabled the main flow field features in this region to be characterized along with identification of the various stream-tubes captured by the fuel injector passages The predictions indicate the resulting flow fields entering the injector passages are not uniform This is particularly evident in the annular passages furthest away from the injector centerline which pass the majority of the flow which subsequently forms the main reaction zone within the flame tube Detailed experimental measurements were also undertaken on a fully annular facility incorporating an axial compressor and lean burn combustion system The measurements were obtained at near atmospheric pressure/temperatures and under nonreacting conditions Time-resolved and time-averaged data were obtained at various locations and included measurements of the flow field issuing from the various fuel injector passages In this way any nonuniformity in these flow fields could be quantified In conjunction with the numerical data, the sources of nonuniformities in the injector exit plane were identified For example, a large scale bulk variation (+/−10%) of the injector flow field was attributed to the development of the flow field upstream of the injector, compared with localized variations (+/−5%) that were generated by the injector swirl vane wakes Using this data the potential effects on fuel injector emissions performance can be assessed

Effect of silver loading on the lean NOx reduction with methanol over Ag-Al2O3

Abstract: The influence of silver loading on the lean NO x reduction activity using methanol as reductant has been studied for alumina supported silver catalysts. In general, increasing the silver loading (0-3 wt%), in Ag-Al 2 O 3 , shifts or extends the activity window, for lean NO x reduction towards lower temperatures. In particular Ag-Al 2 O 3 with 3 wt% silver is active for NO x reduction under methanol-SCR conditions in a broad temperature interval (200-500 C), with high activity in the low temperature range (maximum around 300 C) typical for exhaust gases from diesel and other lean burn engines. Furthermore, increasing the C/N molar ratio enhances the reduction of NO x . However, too high C/N ratios results in poor selectivity to N 2 . © 2013 Springer Science+Business Media New York.

Ambient temperature NOx emission control for lean-burn engines by electro-catalytic tubes

Abstract: Lean-burn gasoline and diesel automobiles can have superior fuel efficiency but require advanced DeNO x technology. For a catalytic converter to be put underneath the passenger cars, it must be compact enough. Effective automotive DeNO x treatment should start at ambient temperature to avoid a heating period when the pollutant cannot be effectively treated. An electro-catalytic honeycomb, composed of electro-catalytic tubes, would fulfill this size requirement. This work demonstrates that effective lean DeNO x can be performed at ambient temperature by an electro-catalytic tube. The DeNO x activity is relatively insensitive to the variation of temperature from 200 to 600 °C and increases slightly when temperature decreases from 200 °C to ambient, but is quite sensitive to that of either the oxygen concentration or the NO x concentration. When the oxygen concentration and the NO x concentration increase from 0.5 to 14% and from 250 to 3800 ppm, respectively, the DeNO x activities increase considerably. The NO conversion also increases with decreasing NO x concentration below 250 ppm, when there is zero NO 2 yield; these can result in zero NO x emission.

3-D Numerical Study of Effect of Flow Parameters upon the Uniformity of NH3 in Urea-SCR

Abstract: Nowadays, due to the stringent engine emission norms, an efficient technique is required to reduce oxides of nitrogen (NOX) from automobiles especially from the lean burn engines. Although Urea Selective Catalytic Reduction (SCR) is capable of satisfying these norms, the ammonia slip nullifies its advantages. Ammonia slip is mainly due to the lack of uniformity of ammonia at the monolith entrance. The uniformity of ammonia distribution mainly depends upon the flow parameters of exhaust gas and the injection parameters of urea water solution. The current study addresses the effect of flow parameters, temperature and flow rate of exhaust gas on the injection pressure. The results obtained reveals useful guidelines for enhancing the uniformity of ammonia in Urea-SCR.