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Viewing 361 to 390 of 86934
2018-04-03
Technical Paper
2018-01-0185
Varun Haresh Nichani, Roberto Jaime, Satbir Singh, Xiaofeng Yang, Volker Sick
Large-eddy simulations (LES) of a motoring single-cylinder engine with transparent combustion chamber (TCC-II) are carried out using a commercially available computer code, CONVERGE. Numerical predictions are compared with high-speed particle image velocimetry (PIV) measurements. Predictions of two spatial discretization schemes namely, numerically stabilized central difference scheme (CDS) and fully upwind scheme are compared. Four different sub-grid scale (SGS) models; a non-eddy viscosity dynamic structure turbulence (DST) model of Pomraning and Rutland [AIAA Journal, 40, 2002], one-equation eddy-viscosity (1-Eqn) model of Menon et al. [Computers and Fluids, 1995], a zero-equation eddy-viscosity model of Vreman [Physics of Fluids, 2004] and the zero-equation standard Smagorinsky model [Smagorinsky, 1963] are employed on two different grid configurations. Additionally, simulations are also performed by deactivating the LES SGS models.
2018-04-03
Technical Paper
2018-01-0186
Christian Ibron
This CFD study focuses on the influence of the nozzle diameter on the mixing process and the soot formation and oxidation process in a heavy-duty diesel engine. The CAD simulation is based on the Reynolds Averaged Navier-Stokes approach. The engine set-up is similar to an experimental case that enables smokeless spray combustion. The aim of the paper is to improve the understanding of the physics of the mixing process in a real engine environment with the attention to scrutinize its effect on combustion and soot emission. Two non-reacting cases with different nozzle diameters but constant injection pressure and their corresponding reacting cases are simulated with dynamic mesh motion and fuel spray modeling. The influence of combustion on the mixing process is analysed and the simulation results are compared with the measurement data. The differences in the mixing process between a constant volume vessel and a dynamic combustion chamber with piston motion are evidenced.
2018-04-03
Technical Paper
2018-01-0187
Pinaki Pal, Christopher Kolodziej, Seungmok Choi, Alberto Broatch, Josep Gomez-Soriano, Yunchao Wu, Tianfeng Lu, Yee Chee See, Sibendu Som
Knock is a major bottleneck to achieving higher efficiency in Spark-Ignition (SI) engines. The recent trends of boosting, downsizing and downspeeding have exacerbated this issue by driving engines toward higher power density and higher load duty cycles. Apart from the engine operating conditions, fuel anti-knock quality is a major determinant of the knocking tendency in engines, as quantified by its octane number (ON). The ON of a fuel is based on an octane scale which is defined according to the standard octane rating methods for Research Octane Number (RON) and Motor Octane Number (MON). These tests are performed in a single cylinder Cooperative Fuel Research (CFR) engine. In the present work, a virtual CFR engine model based on 3D computational fluid dynamics (CFD) was developed.
2018-04-03
Technical Paper
2018-01-0188
Guangfei Zhu, Krishna Pattabiraman, Federico Perini, Christopher Rutland
A swept-volume method of calculating the volume swept by the flame during each time step is developed and used to improve the calculation of fuel reaction rates. The improved reaction rates have been applied to the ignition model and coupled with the level set G-equation combustion model. In the ignition model, a single initial kernel is formed after which the kernel is convected by the gas flow and its growth rate is determined by the flame speed and thermal expansion due to the energy transfer from the electrical circuit. The predicted ignition kernel size was compared with the available experimental data and good agreements were achieved. Once the ignition kernel reaches a size when the fully turbulent flame is developed, the G-equation model is switched on to track the mean turbulent flame front propagation.
2018-04-03
Technical Paper
2018-01-0181
Vignesh Pandian Muthuramalingam, Anders Karlsson
This work utilizes previously developed VSB2 (Volvo Stochastic Blob and Bubble) multicomponent fuel spray model to study significance of using non-ideal thermodynamics for droplet evaporation under direct injection engine like operating conditions. Non-ideal thermodynamics is used to account for vapor-liquid equilibrium arising from evaporation of multicomponent fuel droplets. In specific, the evaporation of ethanol/iso-octane blend is studied in this work. Two compositions of the blend are tested, E-10 and E-85 respectively (the number denotes percentage of ethanol in blend). The VSB2 spray model is implemented into OpenFoam CFD code which is used to study evaporation of the blend in constant volume combustion vessel. Liquid and vapor penetration lengths for the E-10 case are calculated and compared with the experiment. The simulation results show good agreement with the experiment. Simulation is performed with two methods- ideal and non-ideal thermodynamics respectively.
2018-04-03
Technical Paper
2018-01-0182
Chaolin Zhang, Bo Hu, Chenguang lai, Hailin Zhang, Ling Qin, Xiaoli Leng, Wenpeng Huang
One-dimensional(1D) simulation tools, the computing speed of which is relatively fast , usually solve simple complexity problems. The solving process of 1D tools is mostly based on one-dimensional dynamic equations and empirical laws and in some cases it cannot obtain a similar accuracy with the three-dimensional(3D) simulation tools, which is usually time-consuming. The 1D-3D co-simulation, which combines the advantages of the two simulation tools while minimizes the disadvantages, is a method that integrates and runs the two simulation tools concurrently. Specially, coupled simulations can offer detailed information where needed 3D domain while offer system level information in the rest of the whole system. The approach not only minimizes the computational cost, but avoids demand for imposing accurate boundary conditions to the 3D simulation.
2018-04-03
Technical Paper
2018-01-0183
Jinlong Liu, James Szybist, Cosmin Dumitrescu
Modern 3D CFD IC engine simulations are extremely complex for the regular user due to the use of complex phenomenological sub-models with solution-adaptive mesh refinement and coarsening, and improved chemistry solvers. This study used ANSYS® Forte, Version 17.2, an IC engine CFD software package, to investigate two tuning constants that influence flame propagation in 3D CFD SI engine simulations: the stretch factor coefficient, C_ms and the flame development coefficient, C_m2. After identifying several C_m2-C_ms pairs that matched experimental data at one operating conditions, simulation results showed that except for HC emissions, the engine models that used different C_m2-C_ms sets predicted similar combustion performance, when the spark timing, engine load, and engine speed were changed from the operating condition used to validate the CFD simulation.
2018-04-03
Technical Paper
2018-01-0179
mohammed jaasim Mubarak ali, Francisco Hernandez Perez, Aliou sow PhD, Hong Im
Super-knock that occurs in spark ignition (SI) engines is investigated using two-dimensional (2D) numerical simulations. The temperature, pressure, velocity, and mixture distributions are obtained and mapped from a top dead center slice of full cycle three-dimensional (3D) engine simulations. Ignition is triggered at one end of the cylinder and a hot spot of known temperature was used to initiate a pre-ignition front to study super-knock. The computational fluid dynamics code CONVERGE was used for the simulations. A minimum grid size of 25 μm was employed to capture the shock wave and detonation inside the domain. The Reynolds averaged Navier-Stokes (RANS) method was employed to represent the turbulent flow and gas phase combustion chemistry was represented using a reduced chemical kinetic mechanism for primary reference fuels. A multi-zone model, based on a well-stirred reactor assumption, was used to solve the reaction terms.
2018-04-03
Technical Paper
2018-01-0178
Mozhgan Rahimi Boldaji, Aimilios Sofianopoulos, Sotirios Mamalis, Benjamin Lawler
A CFD investigation has been conducted to study the efficiency and emissions characteristics of Thermally Stratified Compression Ignition (TSCI) combustion with direct water injection. The motivation for using this new low temperature combustion mode is its ability to control the heat release process by introducing a forced thermal stratification using direct injection of water. The added degree of control over the combustion process allows for a significantly broader operable load range compare to HCCI. The effect of injection parameters including the mass, pressure, start of injection (SOI) timing, and spray pattern have been shown previously to affect the heat release of TSCI and its induced thermal stratification. In the present work, the efficiency and emissions considerations were investigated in detail. The 3-D CFD model was implemented in CONCERGE CFD coupled with detailed chemical kinetics.
2018-04-03
Technical Paper
2018-01-0180
Sundararaj Senthilkumar, Ssheshan P, U Chandrasekhar PhD
Design of Gas turbine engines demands for better aerodynamic characteristics, which in turn helps in controlling emissions. The need of an innovative and high precision aerodynamic design changes require a large amount of testing with less product development duration. So the development of an integrated approach for predicting flow in a gas turbine combustor is of cardinal important in the field of gas turbine engines. In the present work, it is aimed at developing an integrated approach for combustor modeling involving rapid prototyping and water tunnel testing to assess the cold flow numerical simulations; the physical model will be subjected to cold flow visualization and parametric studies and CFD analysis to demonstrate its capability for undergoing rigorous cold flow testing. A straight through annular combustors with axial swirler is chosen for the present study because of it has low pressure drop, less weight and used widely in modern day aviation engines.
2018-04-03
Technical Paper
2018-01-0174
Marco Del Pecchia, Sebastiano Breda, Alessandro D'Adamo, Stefano Fontanesi, Adrian Irimescu, Simona Merola
The detailed study of part-load conditions is essential to characterize engine-out emissions in key operating conditions. The relevance of part-load operation is further emphasized by the recent regulation (e.g. WLTP standard). The combustion development at part-load operations depends on a complex interplay between moderate turbulence levels (low engine speed and tumble ratio), low in-cylinder pressure and temperature and stoichiometric-to-lean mixture quality (to maximize fuel efficiency at partial loads). From a modelling standpoint, the reduced turbulence intensity compared to full-load operations complicates the interaction between different sub-models (e.g. re-consideration of the flamelet hypothesis adopted by common combustion models). In this paper the authors focus on chemistry-based simulations for laminar flame speed of gasoline surrogates at conditions typical of part-load operations.
2018-04-03
Technical Paper
2018-01-0176
Jann Koch, Stefan Geringer, Daniele Farrace, Sushant Pandurangi, Michele Bolla, Yuri M. Wright, Konstantinos Boulouchos
Large Eddy Simulation (LES) of premixed turbulent combustion in a confined cylinder setup at engine relevant conditions has been carried out for three different initial turbulence intensities, mimicking different flame propagation regimes. Direct Numerical Simulation (DNS) of the setup under investigation provides the reference data to be compared against. The DNS fields have been filtered on the LES grid and are used as initial conditions for the LES at onset of combustion, guaranteeing a direct comparability of the single realizations between the modeled and reference data. Two different combustion models, the G-Equation and LES-CMC premixed are compared with respect to their predictive capabilities as well as their usability and computational cost. While the G-Equation is a widely adopted approach for industrial applications and usually relies on a tunable turbulent flame speed closure, the novel LES-CMC comes as a tuning parameter free model.
2018-04-03
Technical Paper
2018-01-0173
Vesselin Krassimirov Krastev, Luca Silvestri, Gino Bella
The interest in URANS/LES hybrids, for the simulation of turbulent flows in Internal Combustion Engines, is consistently growing. An increasing number of applications can be found in the specialized literature for the past few years, including both seamless and zonal hybrid formulations. Following this trend, we have already developed a DES-based zonal modeling technique, which was found to have adequate scale-resolving capabilities in several engine-like reference tests. In the present paper we further extend our study, by evaluating the effects of the underlying turbulence model and of the grid quality/morphology on the scale-resolved part of the flow. For that purpose, we consider DES formulations based on an enhanced version of the k-g URANS model and on the URANS form of the popular RNG k-e model. The simulated test cases include a static intake valve geometry and a reference reciprocating piston/cylinder assembly.
2018-04-03
Technical Paper
2018-01-0175
Douglas P. Breden, Anand Karpatne, Laxminarayan Raja
The maximum lifetime of a spark plug is limited by electrode erosion. Over the course of millions of repeated sparking events, the electrode material ablates and the electrode gap increases which degrades performance. Once a critical gap is reached, the spark plug is no longer operational and must be replaced. Due to the long relevant time scales over which erosion occurs, and the difficulty of analyzing the spark plug environment during operation, determining spark plug lifetime typically requires extensive field testing. The objective of this work is use a computational model that can accurately simulate the electrode erosion process and make predictions on the effective lifetime. The problem is challenging in that there are a vast range of time scales, all of which must be resolved to model the erosion. Time scales range from milliseconds needed to resolve arc physics up to days and weeks for time timescales of electrode deformation due to ablation.
2018-04-03
Technical Paper
2018-01-0169
Victor Tizon Otero, Stephen Samuel
The thermal management of a Formula 1 car is a challenging task as it involves multiple components, systems and multiple sources of thermal energy. The present work attempts to model a representative F1 car following 2018 F1 regulations directly linked to the cooling systems requirements and performance. The main purpose of this work is to simulate the steady and transient behavior of the cooling system when the vehicle is in a qualifying lap, and during the entire race, including the wait in the starting grid and the pit stops. This model includes the sub-models representing internal combustion engine, hybrid powertrain, vehicle, driver and an appropriate cooling system composed of radiators, pumps and expansion tanks. This work validates the cooling system of a representative 2018 F1 car for the Silverstone Circuit. This model is capable of simulating the overall thermal performance of the F1 car for sizing the cooling system for most of the F1 circuits.
2018-04-03
Technical Paper
2018-01-0170
Andreas Kaechele, Marco Chiodi, Michael Bargende
The simulation of transient engine behavior has gained importance mainly due to stringent emission limits, measured under real driving conditions, and the concurrently demanded vehicle performance. This is especially true for turbocharged engines, as combustion engine and turbocharger form a complex system in which the components influence each other causing for example the well-known turbo-lag. Because of this strong interaction, the components cannot be analyzed separately during a transient load case as they mutually determine their boundary conditions. Three dimensional simulations of full engines in stationary operating points have become practicable several years ago and will remain a valuable tool in virtual engine development; however the next logical step is to extend this approach into the transient domain.
2018-04-03
Technical Paper
2018-01-0172
Yu-Hung Chang, Angela Wu, David Reuss, Volker Sick
Turbulent flow within the cylinder of a reciprocating internal combustion (IC) engine plays a fundamental role that affects engine performance, exhaust emissions, and in particular, their cycle-to-cycle variation. In efforts to predictively simulate engine performance, large-eddy simulation (LES) continues to find increasing interest and with enhanced computational capabilities, LES begins to become a design tool. Validation of LES as well as further enhancements can be guided by experimental data, such as results from particle image velocimetry (PIV) measurements. In this context, this paper discusses the analysis of subgrid-scale (SGS) contributions to LES and assesses appropriate cut-off scales at which the SGS model can derive quantitative scaling information from resolved scale input. Residual stress is one of the most frequently unclosed parameters in SGS models.
2018-04-03
Technical Paper
2018-01-0165
Qirui Yang, Michael Bargende, Michael Grill
With the increasingly strict emission regulations and economic demands, variable valve trains are gaining in importance in Diesel engines. The valve control strategy has a great impact on the in-cylinder charge motions, turbulence level, thus also on the combustion and emission formation. In order to predict in-cylinder charge motions and turbulence properties for a working process calculation, a zero-/quasi-dimensional flow model is developed for the Diesel engines with a fully variable valve train. For the purpose of better understanding the in-cylinder flow phenomena, detailed three-dimensional CFD simulations of the intake and compression strokes are performed at different operating conditions with various piston configurations. In the course of model development, global in-cylinder charge motions are assigned to idealized flow fields.
2018-04-03
Technical Paper
2018-01-0171
Abhishek Y. Deshmukh, Tobias Falkenstein, Heinz Pitsch, Maziar Khosravi, David van Bebber, Michael Klaas, Wolfgang Schroeder
The obligation for the development of highly efficient and low-emission combustion engines has renewed the interest in Compressed Natural Gas (CNG) engines using a Direct Injection (DI) system. DI-CNG is a promising technology because it can take advantage of high compression ratio potentially surpassing the thermal efficiency of spark-ignition engines, as well as eliminating the problem of low volumetric efficiency in port-injected gas engines by removing throttle valves similarly to diesel engines. Additionally, in contrast to diesel fuel, CNG burns without soot emissions due to high hydrogen to carbon ratio. It is presently available at low cost from natural sources and may be available through renewable sources in future as world-wide researchers are trying to synthesize carbon-based fuels using electricity. However, DI-CNG engines have not been widely used so far despite of these advantages, partly due to design problems.
2018-04-03
Technical Paper
2018-01-0164
Pradhan S, Jeemon P K
Superchargers are engine driven positive displacement devices which increase the air mass flow into the engine, thereby leading to better combustion. This gives an advantage of extracting more power from the same engine, thereby reducing emissions and achieving a better fuel economy. With emission norms getting more and more stringent, the need for boosting engine intake air becomes very important. The roots type supercharger works on the principle of backflow compression, where in, air in a plenum at higher constant pressure leaks into chambers which discharge air into this plenum. This discharge of air from chambers is effected by rotating members called lobes in a close toleranced housing, thereby forming chambers. Since the rotors rotate at high speeds, safe clearances must be maintained between housing and rotors. These clearances result in axial ad radial leakage paths between chambers which lead to a reduction in mass flow rate for the said pressure ratio.
2018-04-03
Technical Paper
2018-01-0166
Pavel Brynych, Jan Macek, Ricardo Novella, Kevin Thein
The current 1D models of two-stroke engine scavenging use a scavenging curve, which determines dependence of burnt gas fraction in exhaust port on current burnt gas fraction in a cylinder. This dependence eliminates classic dependence of charging efficiency on delivery ratio with the well-known phases of burnt gas perfect expelling, mixing with fresh charge or even short-circuit scavenging, i.e., direct escaping fresh charge in an exhaust port. They can be found using time-consuming 3D simulations of scavenging flow together with scavenging curves. The direct use of charging efficiency dependence is not possible during the integration of differential equations for 1D model, since it would need iteration during every integration step. The three described phases, depending on the amount of of gas delivered through an inlet port, are present, nevertheless, at any two-stroke engine, although with different timing and intensity.
2018-04-03
Technical Paper
2018-01-0161
Graham Conway, Dennis Robertson, Chris Chadwell, Joseph McDonald, Daniel Barba, Mark Stuhldreher, Aaron Birckett
The thermal efficiency benefits of low-pressure loop (LPL) EGR on spark-ignition engine combustion are well known. One of the greatest barriers facing adoption of LPL-EGR, on high power-density applications, is the challenge of boosting. Variable nozzle turbines (VNT) have recently been developed for gasoline applications operating at high exhaust gas temperatures (EGT). The use of a single VNT as a boost device was preferred to two-stage boosting system or a 48 V electronic boost device for this study. A predictive model was created based on engine testing results from a 1.6 L turbocharged GDI engine [1]. The model was tuned so that it predicted burn-rates and end-gas knock over an engine operating map with varying speed, load, EGR rate and fuel type.
2018-04-03
Technical Paper
2018-01-0160
Alberto Broatch, Pablo Olmeda, Jaime Martin, Josep Salvador-Iborra
To face the current challenges of the automotive industry, there is a need of computational models capable to reproduce the engine behavior at low-temperature and low-pressure conditions. Internal combustion engines are complex and interconnected systems where many processes take place and influence each other. In this work, different models were developed and set-up to make possible the simulation of hydraulic circuits and the heat transfer processes taking place among them and the other engine elements. After its development, the models were implemented in a global 0D engine model. Engine simulations were compared with steady-state tests and the WLTP cycle. Trends of coolant and oil temperatures and flow rates were correctly predicted.
2018-04-03
Technical Paper
2018-01-0163
Kai Deppenkemper, Can Özyalcin lng, Markus Ehrly lng, Markus Schoenen, Dirk Bergmann, Stefan Pischinger
The cold start and heating phase of passenger car diesel engines is essential to comply with the actual emission legislation targets. The initially low temperature level of the exhaust gas aftertreatment system components results in a very low conversion efficiency. Therefore, the authors have investigated the potential of valve train variabilities systematically in terms of pollutants and CO2 emission reduction as well as to support the heating behavior of the exhaust gas aftertreatment system on a full size engine and demonstrator vehicle. Within these investigations, an extended engine speed and load range has been considered relevant for real driving operation. This publication deals with the introduction of a new approach of 1D engine simulation modelling for full-transient engine operation. It merges the engine process together with the aftertreatment simulation in the diesel engine development.
2018-04-03
Technical Paper
2018-01-0225
Bradley Denton, Daniel Christopher Bitsis, Jason Miwa
With increasing diesel engine emissions regulations and the desire to increase overall thermal efficiency of the engine, various combustion concepts have been explored. One of the potential pathways to higher efficiency is through reduction of in-cylinder heat transfer. In this paper, a concept aimed at decreasing in-cylinder heat transfer through increased piston temperature is explored. In order to increase piston temperature and ideally reduce in-cylinder heat transfer, a Zero-Oil-Cooling (ZOC) piston concept was explored. To study this concept, the test engine was modified to allow piston oil cooling to be deactivated so that its impact on parameters such as BTE, piston temperature, and emissions could be evaluated. The engine was equipped with in-cylinder pressure measurement for combustion analysis as well as a piston temperature telemetry system to evaluate piston crown temperature. This paper will discuss the process by which the engine was modified to achieve ZOC and tested.
2018-04-03
Technical Paper
2018-01-0222
Joseph Camm, Martin Davy, Xiaohang Fang, Luke Doherty, Matthew McGilvray, Felix Foerster
A new reflected shock tube facility, the Cold Driven Shock Tube (CDST), has been designed, built and commissioned at the University of Oxford, specifically for high temperature, high pressure fuel spray and chemical kinetics research. From cold, quiescent conditions, the initiation of a shock wave propagating towards one end of the tube, and reflecting from the sealed end, creates a nominally quiescent high temperature, high pressure slug of gas, inside which may contain pre-mixed fuel vapour for auto-ignition studies or into which liquid fuel may be injected for fuel spray studies. The facility has been created as part of the ‘Ultra Efficient Engines and Fuels’ collaborative project, funded by the EPSRC in the UK. It is anticipated that these experiments will support fundamental research for future IC engine and fuel technologies, which will demand ever higher thermal efficiency and ever lower harmful emissions.
2018-04-03
Technical Paper
2018-01-0223
Tayyar Ozel, Matthew J. Hall, Ron Matthews
Manufacturers of light-duty Diesel engines are currently facing unprecedented scrutiny due to alleged emissions cheating and concerns of federal and local governments regarding the effect of Diesel emissions on urban air quality. Light duty vehicles must meet emissions standards established as standardized drive cycles using chassis dynamometers, while heavy-duty Diesel engines must comply with emissions regulations established by standardized torque and engine speed versus time test cycles on an engine dynamometer. It is recognized that these standardized tests are approximations for actual real-world driving conditions. Because actual driving practices can deviate significantly from these cycles, actual Diesel engine emissions can be significantly greater than those measured during the standard cycles, leading to high levels of pollutants being emitted.
2018-04-03
Technical Paper
2018-01-0221
Stefano D'Ambrosio, Fabio Gaia, Daniele Iemmolo, Alessandro Mancarella, Nicolò Salamone, Roberto Vitolo, Gilles Hardy
The premixed charge compression ignition (PCCI) is an advanced combustion mode aimed to simultaneously reduce exhaust emissions of particulate matter and nitrogen oxides with respect to conventional diesel combustion, thanks to a partially premixed charge and a low temperature combustion. In this work PCCI combustion has been implemented by means of an early single injection strategy and high amounts of recirculated exhaust gas. Starting from a Euro VI commercial on-road production engine, the engine hardware has been modified in order to optimize PCCI operations, adopting a smaller turbo group, new combustion chamber and injectors, and a dedicated high-pressure exhaust gas recirculation system. Results in terms of engine performance and exhaust emissions in steady-state operations are presented in this work, comparing the original Euro VI calibration on the conventional engine to the PCCI calibration on the optimized hardware engine.
2018-04-03
Technical Paper
2018-01-0218
Matthew Ratcliff, Jonathan Burton, Petr Sindler, Earl Christensen, Lisa Fouts, Robert McCormick
The knock-limiting effects of a set of surrogate gasolines all having nominally 100 research octane number (RON), approximately 11 octane sensitivity (S), and a heat of vaporization (HOV) range of 390 – 595 kJ/kg were investigated. A single cylinder engine derived from a GM Ecotec direct injection (DI) engine was used to perform load sweeps at a fixed intake air temperature of 50°C, as well as knock-limited load measurements across a range of intake air temperatures. Both DI and pre-vaporized fuel (supplied by a fuel injector mounted far upstream of the intake valves and heated intake runner walls) experiments were performed to separate the chemical and thermal effects of the fuels’ knock resistance. The DI load sweeps showed no effects of fuel composition or HOV on the knock-limited performance, i.e., the data suggest that HOV may act as a thermal contributor to S under the conditions studied.
2018-04-03
Technical Paper
2018-01-0219
Jonathan M. S. Mattson, Christopher Depcik
Diesel knock and ringing combustion in compression ignition (CI) engines are largely an unavoidable phenomenon and are partially related to the overall effectiveness of the fuel injection process. Modern electronic fuel injection systems have been effective at reducing the intensity of knock in CI engines, largely through optimization of fuel injection timing, as well as higher operating pressures that promote enhanced fuel and air mixing. In this effort, a single-cylinder CI engine was tested under a number of different injection strategies, including a comparison of mechanical and electronic injection systems, increasing fuel injection pressures for biodiesel fuels, and the usage of dual-fuel combustion with compressed natural gas (CNG). Using in-cylinder pressure traces and engine operational data, the difference in injection mechanisms, fuel preparation, and their effects on knock intensity is clearly illustrated.
Viewing 361 to 390 of 86934