bluuebunny/crossref_metadata_2025 huggingface dataset:
Simplified Method for Fuel Quality Prediction
Authors: Sivaraman Aravind , Ranganathan Sridhar , Tangirala Shashank , Rao G. Lakshmi Narayana
Published: November 2008

The objective of this work is to compare the quality of various diesel fuels using a normal engine and carrying out the test under the actual operating conditions of the engine, unlike the conventional test methods that uses standard test conditions. The standard test conditions involve the running of the diesel engine test rig at a speed of around 800 rpm, which is not the condition when the fuel is actually being used, as the operational speed of commercial engines is around 1500–2000 rpm. Also the non-engine based quality rating methods are not economically liable and are inaccurate as they depend too much on the chemical nature of the fuel. So, the objective of this work is to develop a generalized quality rating procedure with less number of parameters, with a simpler and cheaper method compared to other available methods. A single cylinder diesel engine was used to study the ignition quality of various reference fuels of known Cetane numbers. A relatively simple and compact setup was used, by modifying the existing test rig. The inlet manifold was incorporated with an airflow control valve so that the quantity of air let into the cylinder can be varied. The exhaust gas manifold was modified to enable easier observation of the exhaust gas. The single cylinder diesel engine was made to run at two distinct conditions, namely, the normal and white-puff / critical condition, with the reference fuels of known cetane numbers. The quantity of air available for the fuel to combust is the only difference between the two conditions. The air-fuel ratio of each fuel under both the conditions was continuously monitored. A correlation was developed between the critical air-fuel ratios and the corresponding Cetane numbers. From this correlation, a test fuel can be rated easily by finding the air-fuel ratio, by running it in the same engine at an identical load, at an instant when the “white puff” is observed.
An Approach for Investigating Adaptive Control Strategies to Improve Combustion Stability Under Dilute Operating Conditions
Authors: Edwards K. Dean , Wagner Robert M. , Theiss Timothy J. , Daw C. Stuart
Published: November 2008

Dilute operation of internal combustion engines through lean fueling and/or high levels of exhaust gas recirculation (EGR) is frequently employed to increase fuel efficiency, reduce NOx emissions, and promote enhanced combustion modes such as HCCI. The maximum level of dilution is limited by the development of combustion instabilities that produce unacceptable levels of cycle-to-cycle combustion variability. These combustion instabilities are frequently stimulated by the nonlinear feedback associated with the residual and recirculated exhaust gases exchanged between successive cycles. However, with the application of adaptive control, it is possible to limit the severity of the combustion variability and regain efficiency and emission reduction benefits that would otherwise be lost. In order to better characterize the benefits of adaptive control, we have employed a two-zone phenomenological combustion model to simulate the onset of combustion instabilities under dilute operating conditions and illustrate the impact of these instabilities on emissions and fuel efficiency. The two-zone in-cylinder combustion model is coupled to a WAVE engine-simulation code, allowing rapid simulation of several hundred successive engine cycles with many external engine parametric effects included. By applying adaptive feedback control to the WAVE model, we demonstrate how mitigation of the extreme combustion events can result in improved efficiency and reduced emissions levels. We expect that this approach can be used to estimate the potential benefits of implementing adaptive control strategies on specific engine platforms to achieve further efficiency and emission-reduction gains.
Projecting Emissions to Year 2020 From Diesel Locomotives in Canada
Authors: Eggleton Peter , Dunn Robert
Published: November 2008

Described are the methodology, database and example projections to the year 2020 of the cumulative emissions from diesel locomotives in Canada for a range of freight and passenger fleet activity profiles. The emissions include both the criteria air contaminants (CAC) harmful to human health and the principal greenhouse gases (GHG) covered by the Kyoto Protocol to the United Nations Framework on Climate Change. The projections show a continuous reduction in emissions intensities to 2020 as the Canadian railways acquire new locomotives meeting U.S. EPA Tier 2 and Tier 3 emissions limits to accommodate both increased traffic and units being retired.
Natural Gas Partial Oxidation and Reforming for Lean NOx Trap Catalysis Regeneration
Authors: Parks James E. , Tassitano Jim
Published: November 2008

Program goals for the Advanced Reciprocating Engine Systems (ARES) program of the Department of Energy include efficiency and environmental goals. Lean-burn natural gas engines offer higher efficiency than engines that operate with Stoichiometric air-to-fuel mixtures; however, the excess oxygen in the exhaust of lean engines makes NOx reduction with catalytic aftertreatment difficult. Thus, advancing efficiency via lean combustion results in challenges to meet environmental goals. The lean NOx trap catalyst technology is capable of reducing NOx in lean exhaust and, thereby, enables the potential for lean combustion to meet both efficiency and environmental goals. During lean NOx trap catalysis, NOx in oxygen-rich exhaust is trapped on the catalyst by alkali or alkaline earth-based sorbate materials; then, upon exposure to oxygen-depleted exhaust, the NOx is released and reduced to nitrogen in a process called regeneration. The regeneration process renews the catalyst for more NOx trapping; the cyclic process repeats at periods on the order of a minute. Oxygen depletion during regeneration is accomplished by temporarily operating the catalyst at rich air-to-fuel ratios; traditionally, a variety of methods have been utilized to achieve rich conditions for the catalyst. In this presentation, research of a lean NOx trap on a lean natural gas engine will be presented. Natural gas from the engine supply was used to provide the reductant for the lean NOx trap regeneration process. The natural gas is injected into the exhaust system where oxidation and reforming catalysts partially oxidize and/or reform the natural gas into reductants suitable for lean NOx trap regeneration. Studies of the natural gas oxidation and reforming processes and their relation to NOx reduction performance will be presented.
An Improved Soot Formation Model for 3-D Diesel Engine Simulations
Authors: Boulanger Joan , Liu Fengshan , Neill W. Stuart , Smallwood Gregory J.
Published: November 2008

In this study, a phenomenological three-equation soot model was developed for modelling soot formation in diesel engine combustion based on considerations of acceptable computational demand and a qualitative description of the main features of the physics of soot formation. The model was developed based on that of Tesner et al. The model was implemented into the commercial STAR-CD CFD package and was demonstrated in the modelling of soot formation in a single-cylinder research version of Caterpillar 3400 series diesel engine with exhaust gas recirculation. Numerical results show that the new soot formulation overcomes most of the drawbacks in the existing soot models and demonstrates a robust and consistent behaviour with experimental observation. Compared to the existing soot models for engine combustion modelling, some distinct features of the new soot model include: no soot is formed at low temperature, minimal model parameter adjustment for application to different fuels, and there is no need to prescribe the soot particle size.
Analysis of the Rotating Arc Spark Plug in a Natural Gas Engine
Authors: Tassitano Jim , Parks James E.
Published: November 2008

Large natural gas engines are durable and cost-effective generators of power for distributed energy applications. Fuel efficiency is an important aspect of distributed generation since operating costs associated with fuel consumption are the major component of energy cost on a life-cycle basis; furthermore, higher fuel efficiency results in lower CO2 emissions. Leaner operation of natural gas engines can result in improved fuel efficiency; however, engine operation becomes challenging at leaner air-to-fuel ratios due to several factors. One factor in combustion control is ignition. At lean air-fuel mixtures, reliable and repeatable ignition is necessary to maintain consistent power production from the engine, and spark plug quality and durability play an important role in reliability of ignition. Here research of a novel spark plug design for lean natural gas engines is presented. The spark plug is an annular gap spark plug with a permanent magnet that produces a magnetic field that forces the spark to rotate during spark discharge. The rotating arc spark plug (RASP) has the potential to improve ignition system reliability and durability. In the study presented here, the RASP plug was operated in a small natural gas engine, and combustion stability (measured by the coefficient of variation of indicated mean effective pressure (IMEP)) was measured as a function of air-to-fuel ratio to characterize the ignition performance at lean mixtures. Comparisons were made to a standard J-plug spark plug.
A Numerical Study on the Effect of Water Addition on NO Formation in Counterflow CH4/Air Premixed Flames
Authors: Guo Hongsheng , Neill Stuart W. , Smallwood Gregory J.
Published: November 2008

The effect of water addition on NO formation in counterflow CH4/air premixed flames was investigated by numerical simulation. Detailed chemistry and complex thermal and transport properties were employed. The results show that the addition of water to a flame suppresses the formation of NO primarily due to the flame temperature drop. Among a lean, a stoichiometric and a rich premixed flame, the effectiveness of water addition is most significant for the stoichiometric flame and least for the rich flame, since the dominant NO formation mechanism varies. The addition of water also reduces the formation of NO in a flame because of chemical effect that increases the concentration of OH, while reduces the concentrations of O and H. Compared to the stoichiometric flame, the chemical effect is intensified in the lean and rich flames.
Experimental and Numerical Investigation of Stratified Exhaust Gas Recirculation (EGR) in a Spray Guided DI Gasoline Engine
Authors: Sarikoc Fatih , Kneifel Alexander , Xander Benedikt , Kettner Maurice , Spicher Ulrich
Published: November 2008

In this paper, results of experimental and numerical investigations of stratified exhaust gas recirculation in a single-cylinder gasoline engine are presented. The engine was operated in spray guided direct injection mode. The radial exhaust gas stratification was achieved by a spatial and temporal separated induction of exhaust gas and fresh air. The spatial separated induction was realized by specially shaped baffles in the inlet port. The temporally separated induction was performed by impulse charge valves, with one for the fresh air and one for the exhaust gas. From various possible strategies for time-dependent induction of fresh air and exhaust gas, three different strategies to stratify the exhaust gas were examined. The first strategy was characterized by a closed left inlet port. Due to the closed inlet port, the swirl motion of both fluids were in the same direction. So mixing effects between both fluids should be minimized. The intake of fresh air was after the intake of exhaust gas. Strategy two and three were characterized by a central induction of fresh air through both inlet ports. The exhaust gas was induced with a swirl motion. At strategy two, the induction of fresh air was before the induction of exhaust gas and at strategy three the temporal induction was vice versa. The in-cylinder flow was investigated using CFD simulation to quantify the distribution of fresh air and exhaust gas in the combustion chamber. These various concepts to stratify the exhaust gas were verified by experiments to evaluate the potential of these concepts to reduce NOx-emissions.
Piston Pin Hole Design Improvement for Engines of Higher Rating
Authors: Krishna Kumar B. , Jebaraj C. , Manivasagam S. , Mahadevan R.
Published: November 2008

This paper studies the effect of design improvements generally prescribed for the piston pin hole on induced stresses with the help of finite element analysis techniques. This decade has seen a very significant increase in the load rating of internal combustion engines. The engines develop a pressure to the tune of 180 bar and more, which needs to be supported by the pin hole, which rests on the piston pin. Predictions of the effect of the increased load on the pin hole and design modifications to support the higher load have become very important activities during the course of piston development. Two design modification options are studied in this paper. The first modification is based on reducing stress concentration by suitably machining a taper profile for a pre-calculated distance at the inner boss zone. The second modification is carried out by having pin hole longitudinal relieves, popularly known as lube slots. Any modification carried out in the pin hole has an influence on the stress distribution at the bowl zone. Therefore, in addition to the pin hole stress, a thorough study on the stress distribution in the bowl zone is also carried out. The numerical results obtained for the modified designs are compared with the base line configuration and the effects of the modifications are discussed in detail. The modifications are found to have a significant effect in reducing the pin hole hoop stress, which is tensile in nature. But at the same time, it has been observed that the tensile hoop stress value in the bowl area increases. Therefore, it is concluded that the suggested pin hole improvements can be carried out if the induced hoop stress values do not exceed the prescribed values for the selected material. Further studies were made to analyze the influence of thermal loading on the stress induced and also to analyze the influence of combined (mechanical and thermal) loading on the induced stress. The thermal hoop stress were compressive in nature and hence its influence on the combined loading is significant. In this paper the results are normalized and shown as tables and figures.
Prediction of Heat Flow and Temperature for Pistons With Improved Cooling Methods
Authors: Vignesh C. , Jebaraj C. , Manivasagam S. , Mahadevan R. , Srinivasan K.
Published: November 2008

This study deals with the prediction of the heat flow and temperature of an IC engine piston having different types of cooling methods. This decade has seen a very significant increase in the load rating of the internal combustion engines. There is a marked shift in the current engines from the conventional NA (Naturally Aspirated) engines. The presence of turbo chargers and super chargers has improved the power output by more than two times. The engines develop a pressure upto 180 bar and release very high heat energy. This has resulted in a piston crown temperature to the tune of 350 Deg. Centigrade. The increase in temperature will have a very serious effect on the lubricating oil, as at elevated temperature oil will have greatly reduced viscosity. Therefore, it is essential to bring the temperature down by having a proper cooling arrangement for the piston system. Two design options of cooling the piston are studied in this paper. In the first option piston is cooled by forcing a jet of oil towards the under-crown portion of the piston. The second option is having a cavity popularly known as cooling gallery, through which the jet of oil is allowed to circulate. The predictive study is carried out by using Finite Element Analysis Techniques. The numerical results obtained for the two options are compared with the base line configuration and the effects of the modifications are discussed in detail. In addition transient thermal analysis is done to predict the transient thermal hoop stress developed in the piston bowl. Since transient hoop stress is the main cause for fatigue failure of the piston bowl, a parametric study is carried out to study the effect of cooling methods on thermal hoop stress.
The Measurement of Valve Clearance in Engine Operating Conditions: A Simple Methodology and Results
Authors: Gaudino P. , Accongiagioco A. , Di Martino U. , Perrussio M.
Published: November 2008

Cam-to-follower clearance influences several aspects of engine operation: valve-train noise, which affects acoustic comfort: valve-train dynamics, which affects engine reliability and functionality; valve lift profile and phasing, which influences combustion cyclic stability especially at idle. If mechanical followers are used on an engine, then, depending on engine operating conditions and different thermal expansion between cylinder head and valve, the valve clearance changes. For this reason the initial and final cam ramps are designed in order to minimize the effects of these variations. When a new valve-train is designed the determination of the nominal valve clearance requires an in-depth knowledge of the above mentioned variations. An experimental evaluation of valve clearance in real engine operating conditions would be desirable. In this paper an extensive experimental activity at engine test bed is presented. A simple, economical and precise indicated methodology was set-up and developed in order to directly measure the angular position of the camshaft when each valve tappet starts to move: in this way valve clearance can be directly determined. These measurements were done in different engine operating conditions with respect to speed and load, and also in thermal and speed transient conditions, in order to determine valve clearance maps. On the intake side a maximum increase of 0.13 mm was found with respect to nominal value, while on the exhaust side a maximum decrease of 0.30 mm was determined. This last value was judged excessive, so some design changes were made in order to limit it: in particular a bi-metallic exhaust valve was tested. The improvement with this type of valve varied from 25% to 70% depending on engine load conditions.
High Fuel Economy Enabled by the Split Engine
Authors: Ross Marc , Lo´pez Alberto J. , Walker Frank H.
Published: November 2008

Half the engine displacement of popular cars and light trucks would be adequate for most driving. The split engine (SE) is introduced here as a concept to improve the fuel economy of light-duty vehicles with large spark-ignition internal combustion engines. It operates with a small-displacement portion of the engine for typical driving and activates the secondary portion of the engine to assist with high-power driving. SE is different from cylinder deactivation; the two portions of the engine have independent crankshafts which connect through a one-way clutch, a mechanical diode with indexing features to achieve the correct relative phase of the engine sections. For illustration, 6- and 8-cylinder SE are proposed and simple versions are modeled analytically. The 6-cylinder SE consists of two inline 3-cylinder engines of equal or near-equal displacement. The 8-cylinder SE consists of two opposed horizontal 4-cylinder engines of the same displacement. SE and cylinder deactivation are also compared. Moments of inertia and the time to connect both engine sections smoothly are estimated. Fuel economy improvements with SE are estimated for the EPA urban and highway cycles.
Influence of EGR on Soot/NOx Production in a Light-Duty Diesel Engine
Authors: Ciatti Stephen A. , Miers Scott A. , Ng Henry K.
Published: November 2008

A study to explore the effect of EGR upon combustion in a light-duty automotive style diesel engine was performed. The engine used in this study was a Mercedes 1.7L 4 cylinder, direct injected turbodiesel with a common rail injection system. The engine was operated at 2500 RPM, 50% load, with constant rail pressure and injection duration. An endoscope imaging system built by AVL, called the VisioScope™, was used to acquire in-cylinder optical images of combustion events. These images were processed to extract soot radiation temperatures and soot volume fraction for each pixel. The results were compared to global engine measurements using piezo-electric pressure transducers, an emissions bench, and a scanning mobility particle sizer (SMPS) to characterize particulates. It was discovered that the optical data correlated well with the global measurements, allowing for in-depth analysis of the mechanisms of emissions formation at three different EGR levels (0%, 10%, 19%). Several conclusions were reached, including the correlation of soot radiation temperature with NOx production and the correlation of soot luminosity with engine-out PM. Each of these factors was determined as a function of EGR level.
Numerical Prediction of Fluid Flow and Diesel Combustion in a Pre-Chamber and Main Chamber
Authors: Ramadan Bassem H. , Ahire Prashant
Published: November 2008

In this study computational fluid dynamics (CFD) was used to model fluid flow and diesel combustion in an IC engine that uses a pre-chamber and a main-chamber. The pre-chamber is located in the cylinder head and a bowl in the piston serves as the main chamber. The study considers the effect of diesel combustion in the pre-chamber on turbulence generation and hence fuel-air mixing and combustion in the piston-bowl. Diesel fuel was injected directly into the pre-chamber and the piston bowl at different times. In order to better determine the effect of pre-chamber combustion on the main chamber combustion, various pre-chamber injection timings were considered. The results show that pre-chamber combustion caused the average cylinder pressure to increase by up to 20% in some cases.
Simulation of an Automotive Catalytic Converter Internal Flow
Authors: Ramadan Bassem H.
Published: November 2008

Catalytic converters have been used for a number of years in the United States to control automotive pollution. A catalytic converter needs to reach a certain temperature before the chemical reactions take place (light-off). Recently, the new regulations on emission standards have prompted a reconsideration of the design of automotive catalytic converters in order to reduce the light-off period of the catalyst. The catalytic converter light-off period is very Important since almost 80% of the emissions from vehicles occur within the first three minutes after cold start in the FTP-75 test. In order to meet these new regulations, current studies have suggested that the catalyst should be “close-coupled”; that is fitted close to the engine exhaust manifold. In order to design “close-coupled” converters, the designer may have to resort to truncated inlet and outlet cones, or distorted inlet pipes due to space limitations. Hence, it is very difficult to achieve good mixing of the exhaust gas, and a good flow distribution at the inlet cross section of the monolith. Based on such a current status in the study of the catalytic converter, the present work focuses on the time-dependent flow patterns, both in the exhaust manifold and the catalytic converter using Computational Fluid Dynamics (CFD). A three-dimensional grid model of an engine exhaust manifold and a close-coupled catalytic converter was developed and analyzed. The flow simulations were performed using KIVA-3 for non-reacting flow fields. These simulations were performed with transient boundary conditions applied at the inlet to the exhaust runners to simulate the opening and closing of exhaust valves. The CFD results were used to study flow uniformity under different operating conditions and to identify the best location for the oxygen sensor.
Development and Testing of a 6-Cylinder HCCI Engine for Distributed Generation
Authors: Flowers Daniel L. , Martinez-Frias Joel , Espinosa-Loza Francisco , Killingsworth Nick , Aceves Salvador M. , Dibble Robert , Kristic Miroslav , Bining Avtar
Published: November 2008

This paper describes the technical approach for converting a Caterpillar 3406 natural gas spark ignited engine into HCCI mode. The paper describes all stages of the process, starting with a preliminary analysis that determined that the engine can be operated by preheating the intake air with a heat exchanger that recovers energy from the exhaust gases. This heat exchanger plays a dual role, since it is also used for starting the engine. For start-up, the heat exchanger is preheated with a natural gas burner. The engine is therefore started in HCCI mode, avoiding the need to handle the potentially difficult transition from SI or diesel mode to HCCI. The fueling system was modified by replacing the natural gas carburetor with a liquid petroleum gas (LPG) carburetor. This modification sets an upper limit for the equivalence ratio at φ∼0.4, which is ideal for HCCI operation and guarantees that the engine will not fail due to knock. Equivalence ratio can be reduced below 0.4 for low load operation with an electronic control valve. Intake boosting has been a challenge, as commercially available turbochargers are not a good match for the engine, due to the low HCCI exhaust temperature. Commercial introduction of HCCI engines for stationary power will therefore require the development of turbochargers designed specifically for this mode of operation. Considering that no appropriate off-the-shelf turbocharger for HCCI engines exists at this time, we are investigating mechanical supercharging options, which will deliver the required boost pressure (3 bar absolute intake) at the expense of some reduction in the output power and efficiency. An appropriate turbocharger can later be installed for improved performance when it becomes available or when a custom turbocharger is developed. The engine is now running in HCCI mode and producing power in an essentially naturally aspirated mode. Current work focuses on developing an automatic controller for obtaining consistent combustion in the 6 cylinders. The engine will then be tested for 1000 hours to demonstrate durability. This paper presents intermediate progress towards development of an HCCI engine for stationary power generation and next steps towards achieving the project goals.
The Effects of Thermochemical Dissociation in Ice Heat Release Evaluation
Authors: Brusca S. , Lanzafame R. , Messina M.
Published: November 2008

Thermochemical dissociation affects the thermodynamics properties of the gases that are present in the products in the cylinder and in the exhaust of an Internal Combustion Engine. At temperature levels greater than the frozen one, the thermodynamics properties of the mixture are different from those evaluated for a “frozen composition” mixture. The most accurate ICE heat release models evaluate the CNHR and the ROHR on the basis of thermodynamic properties of the species present in cylinder gases during the combustion process. In the current paper the authors have evaluated the effects of thermochemical dissociation on ICE heat release.
Modeling Diesel Spray Flame Lift-Off, Sooting Tendency and NOx Emissions Using Detailed Chemistry With Phenomenological Soot Model
Authors: Kong Song-Charng , Sun Yong , Reitz Rolf D.
Published: November 2008

A detailed chemistry-based CFD model was developed to simulate the diesel spray combustion and emission process. A reaction mechanism of n-heptane is coupled with a reduced NOx mechanism to simulate diesel fuel oxidation and NOx formation. The soot emission process is simulated by a phenomenological soot model that uses a competing formation and oxidation rate formulation. The model is applied to predict the diesel spray lift-off length and its sooting tendency under high temperature and pressure conditions with good agreement with experiments of Sandia. Various nozzle diameters and chamber conditions were investigated. The model successfully predicts that the sooting tendency is reduced as the nozzle diameter is reduced and/or the initial chamber gas temperature is decreased, as observed by the experiments. The model is also applied to simulate diesel engine combustion under PCCI-like conditions. Trends of heat release rate, NOx and soot emissions with respect to EGR levels and start-of-injection timings are also well predicted. Both experiments and models reveal that soot emissions peak when the start of injection occurs close to TDC. The model indicates that low soot emission at early SOI is due to better oxidation while low soot emission at late SOI is due to less formation. Since NOx emissions decrease monotonically with injection retardation, a late injection scheme can be utilized for simultaneous soot and NOx reduction for the engine conditions investigated in this study.
Comparisons of Combustion Simulations Using a Representative Interactive Flamelet Model and Direct Integration of CFD With Detailed Chemistry
Authors: Kong Song-Charng , Kim Hoojoong , Reitz Rolf D. , Kim Yongmo
Published: November 2008

Diesel engine simulation results using two different combustion models are presented in this study, namely the Representative Interactive Flamelet (RIF) model and the direct integration of CFD and CHEMKIN. Both models have been implemented into an improved version of the KIVA code. The KIVA/RIF model uses a single flamelet approach and also considers the effects of vaporization on turbulence-chemistry interactions. The KIVA/CHEMKIN model uses a direct integration approach that solves for the chemical reactions in each computational cell. The above two models are applied to simulate combustion and emissions in diesel engines with comparable results. Detailed comparisons of predicted heat release data and in-cylinder flows also indicate that both models predict very similar combustion characteristics. This is likely due to the fact that after ignition, combustion rates are mixing controlled rather than chemistry controlled under the diesel conditions studied.
Numerical Simulation of the Dynamic Response of a Diesel Fuel Injector Using CFD
Authors: Yi Yong , Egelja Aleksandra , Sung Clement J.
Published: November 2008

The development of a very high pressure diesel fuel injection system has been one of the key solutions to improve engine performance and to reduce emissions. The diesel fuel management in the injector directly affects how the fuel spray is delivered to the combustion chamber, and therefore affects the mixing, combustion and the pollutants formation. To design such a very high pressure diesel fuel injection system, an advanced CFD tool to predict the complex flow in the fuel injection system is required in the robust design process. In this paper, a novel 3D CFD dynamic mesh with cavitation model is developed to simulate the dynamic response of the needle motion of a diesel fuel injector corresponding to high common rail pressure and other dimensional design variables, coupling with the imbalance of the spring force and the flow force (pressure plus viscous force). A mixture model is used for cavitation resulting from high speed flow in fuel injector. Due to the lack of experimental data, the model presented in this paper is only validated by a limited set of experimental data. Required meshing strategy is also discussed in the paper.
A Phenomenological Model for Combustion and Emissions in Small Bore, High Speed, Direct Injection Diesel Engines
Authors: Henein N. A. , Singh I. P. , Zhong L. , Poonawala Y. , Singh J. , Bryzik Walter
Published: November 2008

This paper introduces a phenomenological model for the fuel distribution, combustion, and emissions formation in the small bore, high speed direct injection diesel engine. A differentiation is made between the conditions in large bore and small bore diesel engines, particularly regarding the fuel impingement on the walls and the swirl and squish gas flow components. The model considers the fuel injected prior to the development of the flame, fuel injected in the flame, fuel deposited on the walls and the last part of the fuel delivered at the end of the injection process. The model is based on experimental results obtained in a single-cylinder, 4-valve, direct-injection, four-stroke-cycle, water-cooled, diesel engine equipped with a common rail fuel injection system. The engine is supercharged with heated shop air, and the exhaust back pressure is adjusted to simulate actual turbo-charged diesel engine conditions. The experiments covered a wide range of injection pressures, EGR rates, injection timings and swirl ratios. Correlations and 2-D maps are developed to show the effect of combinations of the above parameters on engine out emissions. Emphasis is made on the nitric oxide and soot measured in Bosch Smoke Units (BSU).
An Investigation of the Low Temperature Combustion Regime (LTC) in a Small Bore HSDI Diesel Engine
Authors: Singh Jasmeet , Poonawala Yusuf , Singh Inderpal , Henein Naeim A. , Bryzik Walter
Published: November 2008

The low temperature combustion regime (LTC) has been known to simultaneously reduce both NOx and smoke emissions. The concept is to burn the fuel vapor-air charge, low in oxygen concentration, at low temperatures to reduce the formation of both NOx and smoke emissions. The paper investigates two combustion concepts in the LTC regime, the MK (modulated kinetics) and the smokeless locally rich diesel combustion and proposes a new strategy for a further reduction in emissions with minimum penalty in fuel economy. Tests were carried out under simulated turbo charged conditions on a single cylinder, small bore HSDI diesel engine with a re-entrant bowl combustion chamber. The engine is equipped with a common rail fuel injection system. Tests covered a wide range of injection pressures, EGR rates, injection timings and swirl ratios to determine their individual and collective contributions in engine-out emissions and fuel economy within this combustion regime. The proposed strategy is based on the results of this experimental investigation.
Combustion Development Investigation in a Common Rail Multi-Jet Diesel Engine With Up to 4 Injections per Engine Cycle
Authors: Ponti Fabrizio , Serra Gabriele , Siviero Carlo
Published: November 2008

Newly developed technologies for modern diesel engines allow designing injection patterns with many degrees of freedom. Multi-jet engines, for example, can perform up to 5 injections within the same engine cycle: Position and duration of each injection, together with rail pressure and EGR rate can be chosen in order to properly design the desired in-cylinder combustion process. This means that during the injection system setup process all the free parameters have to be set to the desired value. If all the injection parameters variations have to be investigated in order to properly set their values, a huge amount of experimental tests should be needed. From this point of view, in order to reduce the need for test bench experimental work, the development of a combustion model can be very useful, to help determining the best injection configuration, and therefore the desired combustion into the cylinder. Single zone combustion models seem to be suitable for this task, thanks to the quick response they can give, and the possibility of using them for control purposes. In the paper a model developed for injection patterns with up to 4 injections is used in order to describe the combustion behavior as a function of the injection parameters. A properly designed set of tests has been performed in order to identify the combustion model. The obtained results give information on the way the combustion parameters, for example the combustion delays (i.e. the time delays between each Start Of Injection SOI, and the corresponding Start Of Combustion SOC), or the amount of fuel burnt for each injection are modified as the combustion process proceeds into the cylinder or as the injection parameters change. The information obtained can be in the following used in order to design the desired injection pattern, using the identified model as a virtual experimental tests generator.
Evaluation and Development of Simple Evaporation Models Used in Spray Simulations
Authors: Yao G. F.
Published: November 2008

Given the droplet surface temperature distribution versus time derived from the recent numerical modeling and experimental measurements of a single droplet evaporation, the gas side heat and mass transfer equations used in simple evaporation models for spray simulation in CFD codes are first evaluated. A new model for droplet evaporation is formulated. Instead of using the infinite or conduction limited models for liquid side heat transfer, in the new model, the liquid side heat transfer is simulated based on the Nusselt number. The model is validated against the published data and was found to be accurate in representing the gas and liquid side heat and mass transfer of a single droplet evaporation.
CFD Modeling of the Performance of a Prechamber for Use in a Large Bore Natural Gas Engine
Authors: Kirkpatrick Allan , Kim Gi-Heon , Olsen Daniel
Published: November 2008

The topic of this paper is the performance of a prechamber for use in a large bore two stroke natural gas engine. With increased regulation of emissions from stationary natural gas engines, there has been interest in modification of the combustion process, such as extending the lean limit, to reduce NOx emissions. One promising combustion technique uses an ignition prechamber. CFD models of a prechamber and the cylinder were developed in order to simulate the performance of a prechamber ignition system. The modeling included a full three dimensional transient analysis with scavenging, moving piston, and main chamber fuel injection. The CFD analysis included the fuel injection into the prechamber, pressurization by the inflowing main chamber gases, spark ignition, combustion, and flame propagation into the main combustion chamber. The computations indicated that the prechamber is more well mixed than the main engine chamber, with the prechamber mixture close to stoichiometric for better ignition. There is a strong, well-organized vortex in the prechamber induced by the incoming jet from the main chamber. The combustion flame in the prechamber travels in the direction of the gas vortex along lines of increasing equivalence ratio. The flame then propagates across the main cylinder in a very uniform fashion, indicating that there is sufficient energy to ignite the lean, partially mixed mixture in the main chamber. The orientation of the prechamber nozzle was also investigated, and an orientation of twenty degrees relative to the main chamber was found to produce a flame that did not impinge on the piston.
High Efficiency Energy Conversion System Based on Modified Brayton Cycle
Authors: Borissov Anatoli A. , Borissov Alexander A. , Kramer Kenneth K.
Published: November 2008

Each year, the users in the U.S. alone spend over $100 billion on various type of engines to produce power — electrical, mechanical, and thermal. Despite technological advances, most all of these power generation systems have only been fine tuned: the engine efficiencies may have been improved slightly, but the underlying thermodynamic principles have not been modified to effect a drastic improvement. The result is that most engines in service today suffer from two major problems: low fuel efficiency and emission of high levels of polluting gases in the exhaust gases. The current state of propulsion engines or distributed generation technologies using heat engines shows an average efficiency of between 20% and 40%. These low efficiencies in a high–cost energy market indicate a great need for more efficient technologies. This paper describes a new method of achieving a very high efficiency, namely optimizing every stage of the thermodynamic process-Brayton cycle. Two modified processes, such as isothermal compression and recuperation, add about 35% efficiency to the conventional Brayton cycle, making 60% efficiency for modified Brayton cycle. By utilizing a positive displacement compressor and expander with a novel vortex combustion chamber and a vortex recuperator, high levels of efficiency with low emissions and noise are possible. The prototype engine with low RPM and high torque has been built which use continuous combustion of different fuels under a constant pressure. First results of the engine’s components testing are presented.
Optimization of Radial Convective Radiating Fin Geometry for Single Cylinder Internal Combustion Engine (ICE): Entropy Generation Minimization
Authors: Taufiq B. N. , Mahlia T. M. I. , Masjuki H. H. , Faizul M. S. , Mohamad E. Niza
Published: November 2008

This study attempts to calculate the optimal geometry of convective-radiating radial of ICEs fin arrays using entropy generation method. The analysis is conducted to achieve the balance between entropy generation due to heat transfer and entropy generation due to fluid friction. In designing of the thermal system, it is important to minimize thermal irreversibilities, because the optimal geometry found while the entropy generation rate is minimized. In this study, the entropy generation minimization (EGM) technique based on fin thickness is applied to study the thermodynamic irreversibility caused by heat transfer and fluid irreversibility in radiating convective radial fin arrays. In addition, the cost parameters of fin optimum thickness is also considered and presented. The entropy generation is found to be strongly influenced by emissivity of fin material surface and increasing the cross flow fluid velocity will enhance the heat transfer rate that will reduce the heat transfer irreversibility.
Precombustion Chamber Design and Performance Studies for a Large Bore Natural Gas Engine
Authors: Olsen Daniel B. , Adair Jessica L. , Willson Bryan D.
Published: November 2008

Precombustion chamber (PCC) ignition is a common method for extending the lean limit and reducing combustion variability in large bore (36–56 cm) natural gas engines. An important component that commonly fails and requires regular replacement, besides the spark plug, is the checkvalve. The checkvalve meters fuel flow into the PCC. In this program the use of an electronic valve for monitoring fuel to the PCC instead of the checkvalve is investigated. Metering the fuel into the PCC with an electronic valve provides a number of different options for improving performance in addition to the benefit of extended valve life. PCC nozzle design is also evaluated as a means for improving PCC and engine performance. Additionally, emissions formation in the PCC is evaluated through the use of a separate pressure transducer in the PCC and a fast sample valve that extracts gas from the PCC.
Development of an Open Path Laser Ignition System for a Large Bore Natural Gas Engine: Part 1 — System Design
Authors: Ahrens David L. , Yalin Azer P. , Olsen Daniel B. , Kim Gi-Heon
Published: November 2008

Using a laser, as opposed to a conventional (electrical) spark plug, to create a combustion initiating spark is potentially advantageous for several reasons: flexibility in choosing and optimizing the spark location, in particular to move the spark away from solid heat sinks; production of a more robust spark containing more energy; and obviation of electrode erosion problems. These advantages may lead to an extension of the lean limit, an increase in engine thermal efficiency, and the concomitant benefits of reduced pollutant emissions. This paper presents the design of a laser ignition system appropriate for a large bore natural gas engine. Design considerations include: optimization of spark location, design of beam delivery system and optical plug, and mitigation of vibration and thermal effects. Engine test results will be presented in the second paper of this two-paper series.
Modeling of Wall Film Formed by Impinging Spray Using a Fully Explicit Integration Method
Authors: Cazzoli Giulio , Forte Claudio , Vitali Cristiano , Pelloni Piero , Bianchi Gian Marco
Published: November 2008

A wall film model has been implemented in a customized version of KIVA-3 code developed at University of Bologna. The model simulates the dynamics of a liquid wall film generated by impinging sprays by solving the mass, momentum and energy equations of a two-dimensional liquid flow over a three-dimensional surface under the basic hypothesis of a ‘thin laminar flow’. The major phenomena taken into account in the present model are: wall film formation by impinging spray; body forces, such as gravity or acceleration of the wall; shear stress at the interface with the gas and no slip condition on the wall; momentum contribution and dynamic pressure generated by the tangential and normal component of the impinging drops; film evaporation by heat exchange with wall and surrounding gas. The governing equation have been integrated in space by using a finite volume approach with a first order upwind differencing scheme and they have been integrated in time with a fully explicit method. Particular care has been taken in numerical implementation of the model. Two different test cases reproducing PFI gasoline and DI Diesel engine wall film conditions have been simulated. The comparisons with experimental data show that the present wall film model well reproduces the evolution in time and the spatial distribution of the liquid film thickness in both cases.
Ignition Characteristics of Methane-Air Mixtures at Elevated Temperatures and Pressures
Authors: Klett Gregory M. , Gupta Sreenath , Bihari Bipin , Sekar Raj
Published: November 2008

Lean operation of natural gas fired reciprocating engines has been the preferred mode of operation as it allows low NOx emissions and simultaneous high overall efficiencies. In such engines, the operation point is often close to where the ignition boundary and the knock limiting boundary cross-over. While knocking is, to a large extent, limited by engine design, ignition of lean-mixtures is limited by the mode of ignition. Since significant benefits can be achieved by extending the lean-ignition limits, many groups have been researching alternate ways to achieve ignition reliably. One of the methods, laser ignition, appears promising as it achieves ignition at high pressures and under lean conditions relatively easily. However, most of the current knowledge about laser ignition is based on measurements performed at room temperature. In this paper, ignition studies on methane-air mixtures under in-cylinder conditions are presented. A Rapid Compression Machine (RCM) was designed to reproduce typical in-cylinder, conditions of high temperature (∼ 490°C) and pressure (∼ 77 Bar) at the time of ignition. Experiments were performed comparing conventional coil based ignition (CDI) and laser ignition on methane-air mixtures while varying pressure and equivalence ratio systematically. It was observed that substantial gains are possible with the use of laser ignition as it extends the lean-ignition limit to the flammability limit, i.e., φ = 0.5. On the other hand, conventional CDI ignition could not ignite mixtures leaner than φ = 0.6. Also, faster combustion times and shorter ignition delays were observed in the case of laser ignition. Through scans performed for minimum required laser energies (MRE), it was noted that the measured values were substantially higher than those reported elsewhere. However, the trends of these values indicate that a laser ignition system designed for φ = 0.65 will successfully operate under all other equivalence ratios of a typical lean-burn engine.