Criteria

Text:
Sector:
Display:

Results

Viewing 421 to 450 of 86944
2018-04-03
Technical Paper
2018-01-0205
Hao Chen, Hanyang Zhuang, David L. Reuss, Volker Sick
The turbulent in-cylinder air flow and the unsteady fuel injection lead to a highly transient air fuel mixing process in spark-ignition direct-injection (SIDI) engines, which requires further investigation. In this study, time-resolved particle image velocimetry (TRPIV) was employed to measure the air flow and fuel spray with one crank-angle degree (CAD) resolution at 1300 rpm in an optically accessible single-cylinder SIDI engine. The measurement was conducted at the center tumble plane, bisecting the spark plug and fuel injector. 84 consecutive cycles were recorded for three engine conditions, i.e. (1) non-fueled motored condition, (2) homogeneous-charge mode with start of injection (SOI) at 50 CAD after top dead center exhaust (aTDCexh), and (3) stratified-charge mode with SOI at 270 aTDCexh. The air flow structure, kinetic energy, and tumble ratio were examined to quantify the effect of the fuel spray on the air flow. Relevance index (-1
2018-04-03
Technical Paper
2018-01-0204
Daniele Farrace, David Sakellarakis, Michele Bolla, Yuri M. Wright, Konstantinos Boulouchos
Formation of soot in an auto-igniting n-dodecane spray under diesel engine relevant conditions has been investigated numerically. The bulk of research thus far has addressed turbulence-chemistry interaction by coupling highly diffusive turbulence models with more sophisticated combustion models. Instead, this study employs the advanced sub-grid scale k-equation model in the framework of a Large Eddy Simulation (LES) together with the uninvolved Direct Integration approach. A reduced n-heptane chemical mechanism has been employed and artificially accelerated in order to predict the ignition for n-dodecane accurately. Soot processes have been modelled with an extended version of the semi-empirical, two-equation model of Leung, which considers C2H2 as the soot precursor and accounts for particle inception, surface growth by C2H2 addition, oxidation by O2, oxidation by OH and particle coagulation.
2018-04-03
Technical Paper
2018-01-0203
Insuk Ko, Kyoungdoug Min, Stefano Fontanesi, Federico Rulli
Large Eddy Simulation (LES) applications to Internal Combustion Engine (hereafter ICE) flows are constantly growing, due to the increase of computing resources and the availability of suitable CFD codes, methods and practices. LES superior capability to model spatial and temporal evolution of turbulent flow structures with reference to RANS makes it a promising tool to describe, and possibly motivate, ICE cycle-to-cycle variability (CCV) and cycle-resolved events such as knock and misfire. Despite the growing interest towards LES in the academic community, applications to ICE flows are still limited. One of the reasons for such discrepancy is to be found in the uncertainty in the estimation of the computational cost of LES. This in turn is mainly dependent on grid density, CFD domain extent, time step size and overall number of cycles to be run. Grid density is directly linked to the possibility to reduce modelling assumptions for sub-grid scales.
2018-04-03
Technical Paper
2018-01-0202
Devyani Patil, Yue Wang, Long Liang, Karthik Puduppakkam, Ahmed Hussein, Chitralkumar Naik, Ellen Meeks
Advanced research in Spark Ignition (SI) engine has been focused on dilute combustion concepts. For example, exhaust gas recirculation is used to lower both fuel consumption and pollutant emissions while maintaining or enhancing engine performance, durability and reliability. These advancements achieve higher engine efficiency but may deteriorate combustion stability. One symptom of instability is a large Cycle to Cycle Variations (CCV) in the in-cylinder flow and combustion metrics. Large-Eddy Simulation (LES) is a Computational Fluid Dynamics (CFD) method that may be used to quantify CCV through numerical prediction of the turbulent flow and combustion processes in the engine over many engine cycles. In this study, we focus on evaluating the capability of LES to predict the in-cylinder flows and gas exchange processes in a motored SI engine installed with a transparent combustion chamber (TCC), comparing with recently published data.
2018-04-03
Technical Paper
2018-01-0201
Yashas Karaya, Srinivasa Krishna Addepalli, J M Mallikarjuna
Gasoline direct injection (GDI) engines have gained popularity in the recent times because of lower fuel consumption and exhaust emissions. But in these engines, the mixture preparation plays an important role which affects combustion, performance and emission characteristics of the engine. The mixture preparation, in turn, depends mainly upon fuel injector location and orientation. Therefore, in this study, an attempt has been made to understand the effect of fuel injector location and nozzle-hole orientation on the mixture preparation, performance and emission characteristics of a GDI engine. The mixture stratification inside the combustion chamber is characterized by a parameter called “stratification index” which is based on average equivalence ratio at different zones in the combustion chamber. The analysis is carried out on a four-stroke wall-guided GDI engine by computational fluid dynamics (CFD) analysis using the CONVERGE software.
2018-04-03
Technical Paper
2018-01-0200
Corinna Netzer, Tim Franken, Lars Seidel, Harry Lehtiniemi, Fabian Mauss
Water injection is a promising technology to improve the fuel efficiency of turbo-charged gasoline engines. Additionally, this technology is believed to enable the efficient operation of the three-way-catalyst also at high load conditions. In this numerical analysis, we investigate the effect of water on the combustion chemistry and the thermodynamics using 3D CFD RANS. In the first step, the influence of different amounts of steam on ignition delay time, laminar flame speed and heat capacity is investigated. In the second step, the impact of water vaporization is analyzed for different injection strategies, such as port and direct injection. Therefore, the water mass flow and the injection pressure are varied. A steady-state, medium speed, high-load operating point is investigated with focus on the effect of water injection on fuel efficiency, knock tendency and exhaust temperature.
2018-04-03
Technical Paper
2018-01-0198
Riccardo Scarcelli, Anqi Zhang, Thomas Wallner, Douglas Breden, Anand Karpatne, Laxminarayan Raja, Isaac Ekoto, Benjamin Wolk
While the spark-ignition (SI) engine technology migrates towards challenging combustion regimes (dilute and boosted operation), advanced ignition technologies generating non-equilibrium types of plasma have continued to receive significant attention from the automotive industry as a potential replacement for conventional spark-plugs. However there are no models currently that can describe the non-thermal plasma ignition process in the computational fluid dynamics (CFD) codes that are widely used in the engine multi-dimensional modeling community. A key question for the engine modelers that are trying to describe the non-equilibrium ignition physics concerns the characteristics of the non-equilibrium plasma. A key challenge is represented by the plasma formation timescale (nanoseconds) that can hardly be resolved within a full engine cycle (milliseconds) simulation.
2018-04-03
Technical Paper
2018-01-0197
Raouf Mobasheri, Mahdi Seddiq
An advanced 3D-CFD computational study was done in order to study the simultaneous effects of diesel injection pressure and single injection timing on the amounts of pollutant emissions and engine performance in a heavy duty, single cylinder iso-butanol/Diesel reactivity controlled compression ignition (RCCI) engine. A reduced chemical n-heptane-n-butanol-PAH mechanism which consists of 76 species and 349 reactions was used to simulate the combustion process of the dual-fuel diesel engine. The baseline operation case was validated with Wang et al. research work and good agreements between in-cylinder mean pressure, the rate of heat release and amounts of pollutant emissions such as NOx, Particulate Matter (PM), unburnt hydrocarbons (UHC) and carbon monoxide (CO) was obtained. Twenty-one different strategies based on two variables (diesel direct injection timing and diesel injection pressure) have been investigated.
2018-04-03
Technical Paper
2018-01-0196
Noah Van Dam, Magnus Sjöberg, Sibendu Som
Large-eddy Simulations (LES) have been carried out to investigate spray variability and its effect on cycle-to-cycle flow variability in a direct-injection spark-ignition (DISI) engine under non-reacting conditions. Initial simulations were performed of an injector in a constant volume spray chamber. Detailed measurements of the spray including quantitative mixing data are used to validate a simulation spray set-up for the stepped-bore multi-hole gasoline direct injection (GDI) injector. A random seed perturbation methodology was used to generate shot-to-shot spray variability in the LES, and comparisons of both mean and standard deviations were made for quantities with sufficient experimental data. After validation, the same spray set-up was used to simulate the same injector in an optically accessible DISI engine.
2018-04-03
Technical Paper
2018-01-0195
Federico Perini, Kenji Hiraoka, Yuji Oda, Akihiro Yuuki, Christopher Rutland, Rolf Reitz
Modeling ignition kernel development in spark ignition engines is crucial to capturing the sources of cyclic variability, both with RANS and LES simulations. Appropriate kernel modeling must ensure that energy transfer from the electrodes to the gas phase has the correct timing, rate and locations, until the flame surface is large enough to be represented on the mesh by the G-Equation level-set method. However, in most kernel models, geometric details driving kernel growth are missing: either because it is described as Lagrangian particles, or because its development is simplified, i.e., down to multiple spherical flames. In this work, we focused on the geometry of kernel development, and developed a new, Triangulated Lagrangian Ignition Kernel model. One (or multiple, if it restrikes) spark channel is initialized as a one-dimensional Lagrangian particle thread.
2018-04-03
Technical Paper
2018-01-0194
Haiwen Ge, Nam Hyo Cho
Pressure ringing in internal combustion engine is observed in in-cylinder pressure measurement, which may be due to combustion dynamics, pressure oscillation inside the combustion chamber, and inside a recessed drilled hole for cylinder pressure sensor installation. In the present study, combustion process of a production diesel engine instrumented with pressure sensors in the cylinder head was analyzed using 3D CFD software CONVERGE. The engine utilized in this analysis is a 2-valve 4.5L 4-cylinder heavy-duty direct-injection diesel engine for off-road applications. Various combustion models such as Shell/CTC ignition-combustion model, SAGE model with n-Heptane mechanism of Chalmers University, and ECFM-3Z model were employed to review their capability in capturing pressure ringing phenomena. The raw pressure signal from measurement and simulation was analyzed by FFT.
2018-04-03
Technical Paper
2018-01-0193
Alberto Broatch, Ricardo Novella, Josep Gomez-Soriano, Pinaki Pal, Sibendu Som
It is challenging to develop highly efficient and extremely clean engines, while meeting user expectations in terms of performance, comfort and driveability. One of the critical aspects in this regard is combustion noise control. Combustion noise represents about 40 percent of the overall engine noise in typical turbocharged diesel engines. The understanding of noise generation is intricate due to its inherent complexity and measurement limitations. Therefore, current efforts are focused on developing efficient strategies to understand the combustion noise mechanisms in order to reduce engine noise while maintaining high efficiency and low pollutant emissions.
2018-04-03
Technical Paper
2018-01-0242
Adam B. Dempsey, Patrick Seiler, Kenth Svensson, Yongli Qi
In this study single-cylinder engine experiments and computational fluid dynamics (CFD) modeling were used to evaluate the classic two-step Hiroyasu soot model. A broad range of direct injected (DI) combustion systems were investigated to assess the predictive accuracy of the soot model as a design tool for modern DI diesel engines. Experiments were conducted on a 2.5 liter single-cylinder engine. Combustion system combinations included 3 unique piston bowl shapes and 7 variants of a common rail fuel injector. The pistons were a Tier 4 final production piston, a re-entrant piston, and a Volvo WAVE-like piston. The injectors featured 6 or 7 holes and systematically varied included spray angle from 120 to 150 degrees and hole size from 170 to 273 microns. Two nominal operating conditions were studied: 25% and 100% load at 1800 rpm. Start of injection timing sweeps at varied injection pressures were run at two exhaust gas recirculation (EGR) levels at each load condition.
2018-04-03
Technical Paper
2018-01-0244
Puneet Valecha, Chinmaya Mishra, PMV Subbarao, Pranab Das
The rising expectation from engine designers to address the increasingly stringent emission norms while retaining and enhancing the engine performance, demands a comprehensive understanding of critical in-cylinder combustion parameters. In this context, experimental research has been the traditional favourite vis-à-vis analytical modelling due to the inherent entanglement associated with the complex chain chemical reactions with the fuel burning rate. Besides, the complexity of modelling the interlinked set of chemical reactions to determine heat release and other combustion characteristics has been prohibitive. In this context, Wiebe function has been a pathfinder for engineering applications as it bypasses the simultaneous and sequential interdependent chain and branching reactions by a continuous, general macroscopic reaction rate expression. However, the suitability of single Wiebe functions were restricted to mostly SI engines.
2018-04-03
Technical Paper
2018-01-0247
Ricardo Novella
A genetic algorithm optimization methodology is applied to the design of the combustion system of a heavy-duty (HD) Diesel engine fueled with dimethyl ether (DME). The study has two objectives, the optimization of a conventional diesel combustion system aiming to achieve US2010 targets and the optimization of a stoichiometric combustion system coupled with a three way catalyst (TWC) to further control NOx emissions and achieve US2030 emission standards. These optimizations include the key combustion system related hardware, bowl geometry and injection nozzle design as input factors, together with the most relevant air management and injection settings. The GA was linked to the KIVA CFD code and an automated grid generation tool to perform a single-objective optimization. The target of the optimizations is to improve net indicated efficiency (NIE) while keeping NOx emissions, peak pressure and pressure rise rate under their corresponding target levels.
2018-04-03
Technical Paper
2018-01-0246
Hu Chien Su, Harsh Goyal, Lewis Clark, Sanghoon Kook, Evatt Hawkes, Qing Nian Chan, Srinivas Padala, Minh Khoi Le, Yuji Ikeda
The present study explores the effect of in-cylinder generated non-thermal plasma on hydroxyl and soot development. Three optical diagnostics of electronically excited hydroxyl (OH*) chemiluminescence, Planar Laser Induced Fluorescence of OH (OH-PLIF) and Planar Laser Induced Incandescence (PLII) are performed in a single-cylinder optical diesel engine. Plasma was generated using a newly developed Microwave Discharge Igniter (MDI), which has the potential to accentuate the formation of active radical pools as well as suppress soot formation while stimulating soot oxidation. Methyl Decanoate fuel was specifically selected for diagnostics due to its low beam attenuation which is required for OH-PLIF and PLII.
2018-04-03
Technical Paper
2018-01-0249
Jonathan Martin, Andre Boehman, Rutvik Topkar, Sumit Chopra, Uday Subramaniam, Heng Chen
In recent years, several unconventional fueling modes have been developed for dual-fuel compression-ignition (CI) engines. One such mode is reactivity controlled compression ignition (RCCI), which utilizes both a high-octane fuel (HOF) and a high-cetane fuel (HCF) via separate injection systems. RCCI has been tested with many fuels, but there have been relatively few tests on the intermediate modes that exist in between RCCI and conventional diesel combustion. For this purpose, a quantitative classification system of fueling modes was created and used to test incremental changes in the fueling mode of a 1.9L GM turbodiesel engine, shifting between conventional diesel combustion (CDC) and RCCI at a single speed/load point. This engine used a 5:2 mass ratio blend of propane and dimethyl ether (DME) as its HOF and ultra-low-sulfur diesel (ULSD) as its HCF.
2018-04-03
Technical Paper
2018-01-0248
Jonathan M. S. Mattson, Chenaniah Langness, Christopher Depcik
The recent increase in natural gas availability has made compressed natural gas (CNG) an option for fueling the transportation sector of the United States economy, particularly in dual-fuel operation alongside ultra low sulfur diesel in standard compression ignition engines. This work investigates the usage of natural gas mixtures at varying Energy Substitution Rates (ESR) within a high compression ratio single-cylinder engine, including performance and heat release modeling of dual-fuel combustion. Results from this work demonstrate the differing behavior of utilizing CNG at various substitution rates, including low-ESRs (7-18%) where operation is not dissimilar from that of normal operation, moderate-ESRs (40-50%) where combustion begins to change but significant changes to engine operation (i.e. injection timing) are not required, and high-ESRs (60-85%) where relatively large changes to injection behavior are required to achieve optimized operation.
2018-04-03
Technical Paper
2018-01-0251
Jaykumar Yadav, Dr A Ramesh
Butanol can be produced from renewable sources and is a promising alternative engine fuel. Experiments were conducted on a turbocharged three cylinder automotive common rail diesel engine that was modified to accommodate solenoid based butanol port fuel injectors. The engine was run in the dual fuel mode with diesel being directly injected. Blends of water and butanol (up to 30% water by mass) were injected. Initially diesel was injected as a single pulse per cycle and the timing was always set at the one for best efficiency. The engine speed was kept at 1800 rpm at different fixed load conditions. Open engine controllers were used for varying the injection parameters of diesel and butanol. Standard instrumentation was used for emissions. Combustion parameters were obtained from average cylinder pressure crank angle data processed using in-house developed software.
2018-04-03
Technical Paper
2018-01-0253
Vittorio Ravaglioli, Fabrizio Ponti, Federico Stola, Matteo De Cesare, Filippo Carra
The continuous development of modern Internal Combustion Engine (ICE) management systems is mainly aimed at complying with upcoming more stringent regulations throughout the world. Performing an efficient combustion control is crucial for efficiency increase and pollutant emissions reduction. These aspects are even more crucial for innovative Low Temperature Combustions (such as RCCI), mainly due to the high instability and the high sensitivity to slight variations of the injection parameters that characterize this kind of combustion. Optimal combustion control can be achieved through a proper closed-loop control of the injection parameters. The most important feedback quantities used for combustion control are engine load (Indicated Mean Effective Pressure or Torque delivered by the engine) and center of combustion (CA50), i.e. the angular position in which 50% of fuel burned within the engine cycle is reached.
2018-04-03
Technical Paper
2018-01-0250
Jesus Benajes, Antonio Garcia, Javier Monsalve-Serrano, Vicente Boronat
The dual-fuel combustion mode known as reactivity controlled compression ignition (RCCI) allows an effective control of the combustion process by means of modulating the in-cylinder fuel reactivity depending on the engine operating conditions. This strategy has been found to be able to avoid the NOx-soot trade-off appearing during conventional diesel combustion (CDC), with diesel-like or better thermal efficiency in a great part of the engine map. The role of the low reactivity fuel properties and engine settings over RCCI combustion has been widely investigated in literature, concluding that the direct-injected fuel injection timing is a key parameter for controlling the in-cylinder fuel stratification. From this, it can be inferred that the physical and chemical characteristics of the direct-injected fuel should have also an important role on the RCCI combustion process.
2018-04-03
Technical Paper
2018-01-0252
Zeeshan Ahmad, Janak Aryal, Olli Ranta, Ossi Kaario, Ville Vuorinen, Martti Larmi
A developing practical approach of dual fuel combustion facilitates the fuel flexibility and provide a base to utilize diverse fuels in internal combustion engines. The abundance of natural gas and its clean burning property due to its lower C/H ratio has drawn the interest toward it. In addition, natural gas has high octane number and high auto-ignition temperature, which makes it a potential fuel to employ as a primary fuel in typical diesel engines with high compression ratio resulting in diesel like efficiency. In this study, DF-combustion involving methane (99.8% pure) as a primary fuel and diesel as a pilot fuel is subjected. In diesel-methane DF combustion, the combustion of lower reactivity fuel methane initiates through the energy provided by compression ignited pilot amount of high reactivity diesel fuel. The experimental investigation of DF-combustion was carried out by a natural luminosity optical method.
2018-04-03
Technical Paper
2018-01-0255
John Roberts, Sage Kokjohn, Deyang Hou, Yiqun Huang
Gasoline compression ignition (GCI) combustion is a promising solution to address increasingly stringent efficiency and emissions regulations imposed on the internal combustion engine. However, the high resistance to auto-ignition of modern market gasolines makes low load compression ignition (CI) operation difficult. Accordingly, a method that enables the variation of the fuel reactivity on demand is an ideal solution to address low load stability issues. Metal engine experiments were conducted on the single cylinder medium duty research engine. The fuels used for this study were 87 octane gasoline (primary fuel stream) and diesel fuel (reactivity enhancer). Initial tests demonstrated load extension down to idle conditions with only 20% diesel by mass, which was reduced to 0% at loads above 3 bar IMEPg.
2018-04-03
Technical Paper
2018-01-0254
Maciej Mikulski, Praveen Ramanujam Balakrishnan, Erik Doosje, Cemil Bekdemir
The Reactivity Controlled Compression Ignition (RCCI) concept for dual-fuel engines has challenges of which some can be overcome using Variable Valve Actuation (VVA) approaches. For various fuel combinations, the engine research community has shown that running dual-fuel engines in RCCI mode, improves thermal efficiency and results in ultra-low engine-out NOx and soot. Depending on available hardware, however, stable RCCI combustion is limited to a certain load range. At low load the combustion efficiency can drop significantly, whereas at high load the maximum in-cylinder pressure can easily exceed the engine design limit. In this paper, three VVA measures to increase load range, improve combustion efficiency, and perform thermal management are presented. Simulation results demonstrate the potential of these VVA measures for a heavy-duty engine running on natural gas and diesel.
2018-04-03
Technical Paper
2018-01-0256
Anand Nageswaran Bharath, Rolf Reitz, Christopher Rutland
Although turbocharging can extend the high load limit of Low Temperature Combustion (LTC) strategies such as Reactivity Controlled Compression Ignition (RCCI), the low exhaust enthalpy prevalent in these strategies necessitates the use of high exhaust pressures for improving turbocharger efficiency, causing high pumping losses and poor fuel economy. To mitigate these pumping losses, the Divided Exhaust Period (DEP) concept is proposed. In this concept, the exhaust gas is directed to two separate manifolds: the blowdown manifold which is connected to the turbocharger, and the scavenging manifold that bypasses the turbocharger. By separately actuating the exhaust valves using variable valve actuation, the exhaust flow is split between two manifolds, thereby reducing overall engine backpressure and lowering pumping losses. In this paper, results from zero-dimensional and one-dimensional simulations of a multi-cylinder RCCI light-duty engine equipped with DEP are presented.
2018-04-03
Technical Paper
2018-01-0257
Ezio Mancaruso, Luigi Sequino, Maria Cristina Cameretti, Roberta De Robbio, Raffaele Tuccillo
Dual-fuel technology has the potential to offer significant improvements in the emissions of carbon dioxide from light-duty compression ignition engines. The dual-fuel (diesel/natural gas) concept represents a possible solution to reduce emissions from diesel engines by using natural gas (methane) as an alternative fuel. Methane was injected in the intake manifold while the diesel oil injected directly into the engine. The present work describes the results of a combined numerical and experimental study on combustion process of a common rail diesel engine supplied with natural gas and diesel oil. In particular, the aim is to study the effect of increasing methane concentration at constant injected diesel amount on both pollutant emissions and combustion evolution. The study of dual-fuel engines that is carried out in this paper aims at the evaluation of the CFD potential, by a 3-dimensional code, to predict the main features of this particular technology.
2018-04-03
Technical Paper
2018-01-0226
Yu Zhang, Praveen Kumar, Yuanjiang Pei, Michael Traver, David Cleary
This research aims to utilize gasoline compression ignition (GCI) to achieve low engine-out NOx emissions with high fuel efficiency, thereby offering a potential pathway to address the future low tailpipe NOx standard (0.027 g/kWh) proposed by the California Air Resources Board (CARB). The experimental work was conducted in a model year 2013 Cummins ISX15 heavy-duty diesel engine, covering a load range of 5 to 15 bar BMEP at 1375 rpm. The engine compression ratio was reduced from the production level of 18.9 to 15.7. In this work, four gasolines with research octane number (RON) ranging from 58 to 93 were studied. Overall, GCI operation resulted in enhanced premixed combustion, markedly improved NOx-soot tradeoffs, and similar fuel efficiency compared to diesel combustion. By employing a split fuel injection strategy and a lower fuel injection pressure, the RON80 gasoline showed improved fuel efficiency at 5 bar BMEP when compared to the baseline ULSD.
2018-04-03
Technical Paper
2018-01-0227
Ryan M. Ogren, Song-Charng Kong
In this study both double and triple injection strategies were used with fuel pressures up to 300 and 250 MPa respectively. Tests were conducted at medium load conditions with cooled, high pressure EGR at a ratio of 40% and higher. A four-cylinder production engine, featuring double turbochargers with one variable geometry turbocharger, was tested. The double injection strategy consisted of a 20% close coupled pilot injection while the triple injection strategy introduced a post injection consisting of 10% the total cycle fuel. Results of this study do not indicate an advantage to extreme fuel pressure. The increased air entrainment reduces soot while increasing the premixed burn heat release, mean cylinder temperature and NOx. Compared to the double injection scheme, triple injections achieved much lower soot for the same EGR rate with only a small NOx penalty.
2018-04-03
Technical Paper
2018-01-0228
Stephen Busch, Kan Zha, Eric Kurtz, Alok Warey, Richard Peterson
In light- and medium-duty diesel engines, piston bowl shape influences thermal efficiency, either due to changes in wall heat loss or to changes in the heat release rate. The relative contributions of these two factors are not clearly described in the literature. In this work, two production piston bowls are adapted for use in a single cylinder research engine: a conventional, re-entrant piston, and a stepped-lip piston. An injection timing sweep is performed at constant load with each piston, and heat release analyses provide information about thermal efficiency, wall heat loss, and the degree of constant volume combustion. Zero-dimensional thermodynamic simulations provide further insight and support for the experimental results. The effect of bowl geometry on wall heat loss depends on injection timing, but changes in wall heat loss cannot explain changes in efficiency.
2018-04-03
Technical Paper
2018-01-0229
Robbert Willems, Robbert Dreezen, P.C. Bakker, Bart Somers
Post-injection strategies prove to be a valuable option for reducing soot emission, but experimental results often differ from publication to publication. These discrepancies are likely caused by the selected operating conditions and engine hardware in separate studies. Efforts to optimize not only engine-out soot, but simultaneously also fuel economy and emission of nitrogen oxides (NOx) complicate the understanding of post-injection effects even more. Still, the large amount of published work on the topic is gradually forming a consensus. In the current work, a Design-of-Experiments (DoE) and regression analysis are used to investigate the influence of a variety of operating conditions on optimal post-injection scheduling. The study targets emissions of soot and NOx, as well as fuel economy. Experiments are conducted on a heavy-duty compression ignition engine at an intermediate load and two common engine speeds.
Viewing 421 to 450 of 86944