Lean Engine Research Articles

Lean or ultra-lean stretched planar methane/air flames

Lean premixed combustion has potential advantages of reducing pollutants and improving fuel economy. In some lean engine concepts, the fuel is directly injected into the combustion chamber resulting in a distribution of lean fuel/air mixtures. In this case, very lean mixtures can burn when supported by hot products from more strongly burning flames. This study examines the downstream interaction of opposed jets of a lean-limit CH 4/air mixture vs. a lean H 2/air flame. The CH 4 mixtures are near or below the lean flammability limit. The flame composition is measured by laser-induced Raman scattering and is compared to numerical simulations with detailed chemistry and molecular transport including the Soret effect. Several sub-limit lean CH 4/air flames supported by the products from the lean H 2/air flame are studied, and a small amount of CO 2 product (around 1% mole fraction) is formed in a “negative flame speed” flame where the weak CH 4/air mixture diffuses across the stagnation plane into the hot products from the H 2/air flame. Raman scattering measurements of temperature and species concentration are compared to detailed simulations using GRI-3.0, C 1, and C 2 chemical kinetic mechanisms, with good agreement obtained in the lean-limit or sub-limit flames. Stronger self-propagating CH 4/air mixtures result in a much higher concentration of product (around 6% CO 2 mole fraction), and the simulation results are sensitive to the specific chemical mechanism. These model-data comparisons for stronger CH 4/air flames improve when using either the C 2 or the Williams mechanisms.

Energy efficiency analyses of active flow aftertreatment systems for lean burn internal combustion engines

Energy efficiency analyses of active flow aftertreatment systems for lean burn internal combustion engines

NOxAbatement by Catalytic Traps: On the Mechanism of NOxTrapping Under Automotive Conditions

NO x adsorption was measured with a barium based NO x storage catalyst at an engine bench equipped with a lean burn gasoline direct injection engine (GDI). In order to study the influence of gas phase NO2 on the NO x storage efficiency two different precatalysts were used: One with excellent NO oxidation activity to produce a high NO2 concentration and another pre-catalyst without NO oxidation activity and therefore high NO concentration at the NO x storage catalyst inlet. Both pre-catalyst had excellent HC and CO conversion efficiency and therefore the CO and HC concentration at the NO x storage catalyst inlet was practically zero. No lean NO x reduction was observed. Under that conditions, experiments with NO x storage catalysts of different length show that a high NO2 inlet concentration did not enhance the NO x storage efficiency. Moreover, we observed reduction of NO2 to NO over the NO x storage catalyst. However, in presence of a high NO inlet concentration NO2 formation was observed which may proceed parallel to NO x storage.

Lean-Burn Catalysts from the Perspective of a Car Manufacturer. Early Work at Volkswagen Research

Lean burn engines offer significantly better fuel economy and also lower engine out emissions of gaseous pollutants than engines tuned to stoichiometric air-fuel ratio. However, the high oxygen excess in the exhaust prohibits the use of the 3-way-catalyst technology for further NOx reduction. New catalytic processes and catalyst materials had to be developed for NOx aftertreatment, to ensure that diesel engines and lean burn DI gasoline engines can comply with very stringent exhaust emissions standards. The paper describes the start and some aspects of the history of that development, from the viewpoint of a car company.

Continuous lean NOx reduction with hydrocarbons over dual pore system catalysts

In order to reduce CO2 emissions there is a trend towards an increased use of more fuel-efficient lean burn combustion engines and thus an increased need for deNOx catalysts for such engines. In this study a mechanical mixture of CoFER and HZSM-5 zeolites was studied as a dual pore system catalyst for the continuous lean reduction of NOx with isobutane as reducing agent. The degree of NOx conversion was found to be strongly dependent on the oxygen concentration in the gas mixture, and the highest degree of reduction was achieved with 10% O2. This optimum is explained by the need for NO2 as an intermediate for the catalyst to work efficiently, and that above a certain oxygen concentration O2 oxidises the hydrocarbon resulting in a lower reduction potential for NOx. At an operating temperature of 350°C the conversion of NOx to N2 was 52% under steady-state conditions, but the efficiency can be improved further by optimisation of the oxidising zeolite and of the mixing ratio of the two zeolites.

コージェネレーション用希薄燃焼ガスエンジンの高効率化へ向けた取り組み(FP5 レシプロエンジンの環境対応技術)

Dramatic improvement in power generation efficiency has become the most urgent task for cogeneration systems. In this paper, 300kW class lean bum gas engine was improved mainly in the aspect of thermal efficiency. First, the differences between gas engines and diesel engines that had higher thermal efficiency were simulated. On the basis of these results, technical problems to be solved to achieve higher efficiency in gas engines were narrowed down to the several points. Then, the miller cycle and other methods which had possibility to solve these problems were applied to the experimental engine. Here, we verified that the application of these technologies to a pre-chamber lean bum gas engine did-help improve thermal efficiency. When these technologies were applied to the new gas engine, thermal efficiency was dramatically improved to over 43%, highest value in 300kW class engines.

Energy efficiency analyses of active flow aftertreatment systems for lean burn internal combustion engines

The use of three way catalytic converters in stoichiometric burn reciprocating internal combustion engine systems has proved to be an effective and efficient method for reducing the level of criteria pollutants. However, such passive systems have not been as successful in emission amelioration when combined with lean burn engines. This is because of the thermochemical nature of the exhaust gases generated by such engines. The high content of exhaust oxygen largely negates the effectiveness of three way catalytic converters, and the comparatively low temperature of the combusted gases means that supplemental energy has to be added to these gases to enable the converter to function correctly. This requirement severely reduces the energy efficiency of conventional passive aftertreatment systems. However, initial empirical studies have indicated that a possible means of improving the performance of aftertreatment devices when used with lean burn engine systems is to use active flow control of the exhaust gases. These results are reported in this paper. This concept has been further investigated by developing an energy efficiency analysis that enables the effects on aftertreatment performance of different gas flow rates, flow reversal frequencies and monolith solid properties to be investigated. Simulation results indicate that through active thermal management, the supplemental energy consumption can be drastically reduced.

Airplane Aeroelasticity: Practice and Potential

A perspective on the practice, issues, and potential of aeroelasticity is presented. The issues of cycle time reduction and improvements in the e delity of aeroelastic analysis need to be emphasized for aeroelasticity to support adequately the airplane cone guration development and cone guration decisions. The introduction of e y-by-wire control systems has increased the complexity as well as the e delity requirements for the aeroelastic analysis. The business cost of inaccuracies in loads and dynamics predictions can be seriously high. Therefore, innovative approaches should be encouraged to address these issues. Aeroelasticity has an opportunity to contribute to airplane design by evolving to become a more integrating discipline. Although many of the methods and processes in different subdisciplines are in place already, others need to be developed further for improved usability, efe ciency, e delity, and integration. The most challenging problems in realizing the full potential of aeroelasticity are not just technical but are also organizational in nature. The organizational issues are related to management of multidisciplinary teams in a lean engineering environment. Thus, to realize the multidisciplinary integrating potential of aeroelasticity and its contributions to thecone guration decisions, technical and managementforesight, leadership, and vision are required.

Lean engineering in the aerospace industry

While lean principles (developed by Womack and Jones) have been applied successfully to manufacturing and operations processes in many companies their application to engineering or new product introduction processes has been lacking. This paper introduces the principles of ‘lean engineering’ through some simple definitions, based on the original lean principles, and by describing applications of those principles in the aerospace industry via three case studies. The three case studies demonstrated the application of lean at three different levels of ‘process’ hierarchy, a detailed design activity level, a project management level and a design strategy level. The study concluded that while the application of lean principles in aerospace engineering processes (within new product introduction) is feasible for both large and small companies, the presence of a coherent and sustainable methodology was missing, as well as proper application of supporting management tools and technology.

Modelling the early stage of spark ignition engine combustion using the KIVA-3V code incorporating an ignition model

The evolution of early stages of homogeneous mixture combustion in spark ignition (SI) engines represents a critical period that greatly affects the whole combustion process. A proper description of this critical phase represents a major issue, which could strongly influence the overall model predictive capability (i.e. model ability to reproduce the real engine behaviour for a large range of operating conditions without any major tuning). Such requirements become even more important for the simulation of last-generation gasoline direct injection or lean stratified engines, where ignition could determine the functionality of the engine itself. In this paper, after a detailed analysis of the ignition physical process and its modelling issues, the predictive capability of the KIVA-3V code has been improved by substituting the original ignition procedure with a more detailed kernel evolution model based on the one presented by Herweg and Maly in 1992. The ignition model introduced in a KIVA-3V version already modified by the authors (re-zoning algorithm, combustion and turbulence models, cylinder wall heat transfer, etc.) has then been tested in order to assess its level of accuracy in describing this complex phenomenon, by varying the most critical engine operating conditions and keeping combustion tuning parameters unchanged. After comparing ignition model results with the corresponding ones presented by Herweg and Maly, a specific application of the overall model (KIVA-3V + ignition model + turbulent combustion model) has been made to perform an analysis of a compressed natural gas (CNG) fuelled engine for heavy-duty applications. To this aim, the in-cylinder combustion history and the related processes as the temperature distribution and NOx formation have been calculated and verified with reference to the experimental data measured in a wide range of operating conditions of an IVECO turbocharged engine.

Prediction of Knocking Occurrence and Evaluation of Combustion Systems in Pre-chamber Lean Burn Gas Engine

Prediction of knocking occurrence was examined in order to quantify knocking phenomena and evaluate combustion systems in pre-chamber lean burn gas engine. By the temperature two region combustion model and thermodynamics diagnostics the temperature of end gas was calculated. Empirical relations of instantaneous temperature and pressure of end gas for induction time was conducted by experiment of single cylinder engine. The single cylinder engine has a bore of 165 mm, a stroke of 185 mm and pre-chamber system with compression ratio of 13.2. Prediction of knocking occurrence was examined by Livengood-Wu integral. It was found that the temperature two region model could express combustion of pre-chamber gas engine and could evaluate combustion systems in pre-chamber lean burn gas engine.

A109 A lean burn Miller cycle gas engine with a high thermal efficiency and low NOx emissions for a co-generation system Comparison of LIVC and EIVC Miller cycle

A109 A lean burn Miller cycle gas engine with a high thermal efficiency and low NOx emissions for a co-generation system Comparison of LIVC and EIVC Miller cycle

ERRATUM: LEAN ENGINEERING FOR MASS HOUSING — DESIGN, MANUFACTURE AND SITE ERECTION

ERRATUM: LEAN ENGINEERING FOR MASS HOUSING — DESIGN, MANUFACTURE AND SITE ERECTION

Ignition timing control of homogeneous charge compression ignition engines by pulsed flame jets

In diesel engines, most of the fuel is burned in a diffusion combustion phase, which inherently leads to the formation of excessive amounts of soot and NOx emissions. In order to decrease soot and NOx emissions simultaneously, the concept of a lean homogeneous charge compression ignition engine has been proposed. The onset of the combustion of the engine depends on the autoignition of the fuel, so it is quite difficult to control the ignition timing. On the other hand, it has been revealed that Pulsed Flame Jet (PFJ) has a great potential to enhance ignition reliability and burning rate in lean mixtures. In this article, autoignition characteristics of n -butane/air mixtures in a rapid compression machine (RCM) were shown first. The appearance of low temperature flames was observed in autoignition of n -butane in the RCM used here, and it was realized that the final compression conditions in the RCM correspond to the upper end of the low-temperature range of the positive temperature dependence region of ignition delay. Then the combustion tests with PFJ were carried out and it was demonstrated that the onset of combustion can be controlled by PFJ, and it was revealed that PFJ has a potential for the ignition timing control of the homogeneous charge compression ignition engine.

LEAN ENGINEERING FOR MASS HOUSING — DESIGN, MANUFACTURE AND SITE ERECTION

There is a tremendous housing shortage in the world that can only be overcome by innovative designs and enlightened production management, such as lean construction. This paper presents a method for fast and low-cost erection of apartment housing units that have architectural flexibility, manufacturing flexibility, and erection flexibility. Flexibility is one of the fundamental aspects of lean manufacturing. The paper describes an innovative design using cam and nut jointing methods for large panel erection, and presents characteristics of an appropriate structural system to correspond to the mechanical jointing and quick erection needs. Current precast plants can quickly acquire capabilities to manufacture large panels as per the stated design using cam and nut. The cam screw and cam nut scheme is conducive to quick erection, besides being capable of withstanding all structural and natural loads. Erection speeds using this method are estimated to be about ten times as fast as conventional methods, thereby facilitating lean production. This paper presents an overall lean approach to the design, manufacture, and construction of this innovative housing system. It is believed that only through innovative systems can future technology needs of the world be met.

Hydrogen engine: research and development (R&D) programmes in Indian Institute of Technology (IIT), Delhi

Active research in the development of hydrogen-fuelled low-emission engines is being pursued at the Engines and Unconventional Fuels Laboratory of the Indian Institute of Technology (IIT), for a period of close to two decades. This paper highlights the significant pursuits and attainments of the research and development (R&D) activities carried out in IIT, Delhi on hydrogen-operated engines. Both spark ignition (SI) and compression ignition engine test rigs have been developed and instrumented for the use of hydrogen fuel. Several existing petroleum-fuelled engine configurations have been modified by taking care to observe that the converted system does not need substantial hardware modifications. Various fuel induction techniques have been experimentally evaluated keeping in view the temperamental combustion characteristic of this fuel. Curative and preventive steps have been adopted and suitable retrofits and subsystems have been installed at the appropriate locations to preclude the possibility of any undesirable combustion phenomena such as backfire, knocking and rapid rate of pressure rise. Performance, emission and combustion characteristics of the systems have been determined. It has been observed that an appropriately designed timed manifold injection system can overcome the problem of backfire in a hydrogen engine. NO x emission level from a hydrogen-operated SI engine can be drastically reduced by way of lean engine operation.

Adsorption and pressure swing desorption of NOx in Na-Y zeolite: experiments and modeling.

Pressure swing NOx adsorption-desorption cycles were performed in the temperature range 200-350 degrees C using a fixed adsorbent bed of compressed Na-Y pellets and using a honeycomb coated with Na-Y powder. The experiments were performed using a synthetic gas mixture mimicking exhaust from a lean burn internal combustion engine. Na-Y zeolite coadsorbs NO and NO2 as N2O3, which in the regeneration were displaced by competitively adsorbed water molecules from a hydrated air stream. The performance of the fixed bed in these NOx adsorption and displacement desorption processes were modeled with a one-dimensional model. The kinetic and thermodynamic parameters from the fixed bed model were implemented in a model for the operation of the monolith. The experimental adsorption and desorption NOx concentration profiles in the monolith were reasonably well reproduced by the model. The water content of the flushing stream and the stripping gas flow rate are key process parameters. Technically, both parameters can be optimized in a valveless system with rotating honeycomb adsorbent comprising a NOx adsorption, a water injection and a NOx evacuation section.

Analysis and Optimization of NOx Storage Catalysts for Lean Burn Otto or Diesel Engines

Analysis and Optimization of NOx Storage Catalysts for Lean Burn Otto or Diesel Engines

A Study of Ignition Characteristic on Premixed Lean DI Diesel Engine.

Recently, pre-mixed lean mixture combustion has attracted attention, and many researchers are investigating compression ignition of a pre-mixed lean mixture. Previous research in our laboratory has shown that low NOx emission combustion is obtained by PREDIC (PREmixed lean Dlesel Combustion) . However some problems still remain, such as higher fuel consumption because of lack of ignition timing control, compared to conventional diesel combustion. So in this study the ignition ; characteristic was researched. As the result, it was cleared that the ignition timing was depended on the cylinder gas temperature and the ignitability of the fuel.

(3-04) Development of the Lean Burn Miller Cycle Gas Engine((AF-2)Alternative Fuels 2-Gas Engines)

Cogeneration systems, using natural gas engine, have been increased because of low NOx emission and low particulate emission. But recently electric power company have been reduced the price of electric power, so it is necessary to increase power generation efficiency of gas engine. To improve thermal efficiency of gas engine, we applied the Miller cycle to the lean burn gas engine. And we improved combustion system and turbocharger for Miller cycle. In order to decide compression ratio and expansion ratio, we used a cycle simulation and a single cylinder test engine. Compression ratio was set to 11 and expansion ratio was set to 15. Inlet swirl ratio was reduced to prevent knocking. In case of low swirl, the combustion rate was decreased, so ignition timing could be advanced. In case of Miller cycle, high boost pressure is necessary to keep engine power. So we developed the high pressure ratio and high efficiency turbocharger. And high durability type spark plug and electrical fuel supply system were applied for high reliability. Finally thermal efficiency of Miller cycle gas engine reached to 42%(Power generation efficiency is 40%). We confirmed that 42% of thermal efficiency during 4000Hr. We have already put 280kW cogeneration package in the market.