Reitz RD

Shipping is one of the most efficient transportation modes for moving freight globally. International regulations concerning decarbonization and emission reduction goals drive rapid innovations to meet the 2030 and 2050 greenhouse gas reduction targets. The internal combustion engines used for marine vessels are among the most efficient energy conversion systems. Internal combustion engines dominate the propulsion system architectures for marine shipping, and current marine engines will continue to serve for several decades. However, to meet the aggressive goals of low-carbon-intensity shipping, there is an impetus for further efficiency improvement and achieving net zero greenhouse gas emissions. These factors drive the advancements in engine technologies, low-carbon fuels and fueling infrastructure, and emissions control systems. This editorial presents a perspective on the future of ship engines and …

The authors regret to inform that the following typographical errors are recorrected in this corrigendum. 1. Section 3.1:“The best-fit values Tref= 600 K and Pref= 0.3 MPa are chosen for Eq.(19). The trial-and-error results are shown in Fig. 1A and Fig. 2A of the f.” is corrected as “The best-fit values Tref= 600 K and Pref= 0.3 MPa are chosen for Eq.(21). The trial-and-error results are shown in Fig. 1A and Fig. 2A of the Appendix” 2. Section 3.4:“Using LFS_ref, the average relative error of the combustion model predictivity [Formula presented]= 29.6–47.6%, depending on the combustion metrics.” is corrected as “Using LFS_conv, the average relative error of the combustion model predictivity [Formula presented]= 29.6–47.6%, depending on the combustion metrics.” 3. Figure 23b: the correct label of the bottom sub-figure is [Formula presented]= 0.5:[Formula presented] 4. 4. Section 3.6:“For engine B at 2000 RPM, case 2 or [Formula presented]= 0.7 ([Formula presented]= 0.587,[Formula presented]= 0.912), case 3 or [Formula presented]= 0.6 ([Formula presented]= 0.509,[Formula presented]= 0.798), and case 3 or [Formula presented]= 0.5 ([Formula presented]= 0.414,[Formula presented]= 0.66) are obtained.” is corrected as “For engine B at 2000 RPM, case 2 or [Formula presented]= 0.7 ([Formula presented]= 0.587,[Formula presented]= 0.912), case 3 or [Formula presented]= 0.6 ([Formula presented]= 0.509,[Formula presented]= 0.798), and case 4 or [Formula presented]= 0.5 ([Formula presented]= 0.414,[Formula presented]= 0.66) are obtained”. 5. Section 3.6: Captions of Figs. 28 and 29:“case 4 [Formula presented]= 0.7 in Table 7” is corrected as …

The introduction of downsized, turbocharged Gasoline Direct Injection (GDI) engines in the automotive market has led to a rapid increase in research on Low-speed Pre-ignition (LSPI) and super-knock as abnormal combustion phenomena within the last decade. The former is characterized as an early ignition of the fuel–air mixture, primarily initiated by an oil–fuel droplet or detached deposit. Meanwhile, super-knock is an occasional development from pre-ignition to high intensity knocking through detonation, which is either initiated by a shock wave interacting with a propagating reaction and cylinder surfaces or inside a hotspot with a suitable heat release and reactivity gradient. The phenomenon can be divided into four stages, including LSPI precursor initiation, establishment and propagation of a pre-ignited flame, autoignition of end-gases and development to a detonation. LSPI and super-knock are rare …

We propose a novel dual-fuel combustion model for simulating heavy-duty engines with the G-Equation. Dual-Fuel combustion strategies in such engines features direct injection of a high-reactivity fuel into a lean, premixed chamber which has a high resistance to autoignition. Distinct combustion modes are present: the DI fuel auto-ignites following chemical ignition delay after spray vaporization and mixing; a reactive front is formed on its surroundings; it develops into a well-structured turbulent flame, which propagates within the premixed charge. Either direct chemistry or the flame-propagation approach (G-Equation), taken alone, do not produce accurate results. The proposed Dual-Fuel model decides what regions of the combustion chamber should be simulated with either approach, according to the local flame state; and acts as a “kernel” model for the G-Equation model. Direct chemistry is run in the regions …

Direct Dual Fuel Stratification (DDFS) strategy is a novel Low Temperature Combustion (LTC) strategy that has comparable thermal efficiency to the Reactivity Controlled Compression Ignition (RCCI) strategy, while it offers more control over the combustion process and the rate of heat release. The DDFS strategy uses two direct injectors for the low- and high-reactivity fuels (gasoline and diesel) to benefit from the RCCI concept. In this study, the injection strategy of the injectors of a gasoline/diesel DDFS engine was optimized from the thermodynamic perspective to maximize exergy efficiency and minimize exergy destruction and an engine noise index. An artificial neural network was developed with 576 samples from a CFD code to predict the DDFS mode behavior, and the non-dominated sorting genetic algorithm (NSGA-II) was used to obtain the Pareto Front and the optimal solutions. Compared to the base case …

The possibility to operate current diesel engines in dual-fuel mode with the addition of an alternative fuel is fundamental to accelerate the energy transition to achieve carbon neutrality. The simulation of the dualfuel combustion process with 0D/1D combustion models is fundamental for the performance prediction, but still particularly challenging, due to chemical interactions of the mixture.The authors defined a novel data-driven workflow for the development of combustion reaction mechanisms and used it to generate a dual-fuel mechanism for Ammonia and Diesel Primary Reference Fuels (DPRF) suitable for efficient combustion simulations in heavy duty engines, with variable cetane number Diesel fuels.

Diesel piston-bowl shape is a key design parameter that affects spray-wall interactions and turbulent flow development, and in turn affects the engine’s thermal efficiency and emissions. It is hypothesized that thermal efficiency can be improved by enhancing squish-region vortices as they are hypothesized to promote fuel-air mixing, leading to faster heat-release rates. However, the strength and longevity of these vortices decrease with advanced injection timings for typical stepped-lip (SL) piston geometries. Dimple stepped-lip (DSL) pistons enhance vortex formation at early injection timings. Previous engine experiments with such a bowl show 1.4% thermal efficiency gains over an SL piston. However, soot was increased dramatically [SAE 2022-01-0400]. In a previous study, a new DSL bowl was designed using non-combusting computational fluid dynamic simulations. This improved DSL bowl is predicted to …

Engine spray models based on phase equilibrium have made great progress in simulating trans/supercritical engine spray processes, but there are inherent weaknesses in terms of efficiency and stability for the conventional phase equilibrium algorithm due to the iterative schemes for solving complex nonlinear equations. The low efficiency of the conventional algorithm limits the amount of detail that can be considered in the simulation, while the instability may lead to unphysical results or even simulation divergence. In this work, a method based on artificial neural networks (ANNs) was developed as a potential alternative to the conventional algorithm applied in the engine spray models to achieve fast and robust phase equilibrium calculations. Three ANNs were constructed, including isothermal-isobaric-ANN (TPn-ANN), isenthalpic-isobaric-ANN (HPn-ANN) and adiabatic-mixing-temperature-ANN (AMT-ANN …

G-Equation models represent propagating flame fronts with an implicit two-dimensional surface representation (level-set). Level-set methods are fast, as transport source terms for the implicit surface can be solved with finite-volume operators on the finite-volume domain, without having to build the actual surface. However, they include approximations whose practical effects are not properly understood. In this study, we improved the numerics of the FRESCO CFD code’s G-Equation solver and developed a new method to simulate kernel growth using signed distance functions and the analytical sphere-mesh overlap. We analyzed their role for simulating propane/air flames, using three wellestablished constant-volume configurations: a one-dimensional, freely propagating laminar flame; a disc-shaped, constant-volume swirl combustor; and torch-jet flame development through an orifice from a two-chamber device …

Diesel piston-bowl shape is a key design parameter that affects spray-wall interactions and turbulent flow development, which, in turn, affects the engine’s thermal efficiency and emissions behavior. Previous simulations and experiments in a small-bore diesel engine with a stepped-lip (SL) piston showed that efficiency increases are due to faster mixing-controlled heat-release, which were correlated with the strength and longevity of squish-region vortices [1, 2]. These vortices are believed to promote fuel-air mixing, leading to increased heat-release rates, but their strength and longevity decreased with advanced injection timing. Simulations predicted that a dimple stepped-lip (DSL) piston can enhance vortex formation at near-TDC injection timings, which is hypothesized to further improve peak thermal efficiency and reduce emissions [2]. In a previous study [3], engine experiments showed that a baseline DSL piston bowl was able to achieve a 1.4% thermal efficiency gain when compared against a SL piston, but soot emissions increased dramatically, with no penalty in NOx emissions. A design sensitivity study using non-combusting CFD simulations was performed to improve the design of the DSL bowl. This led to a DSL bowl with shallower, narrower, and steeper-curved dimples that are further out into the squish region, leading to stronger and more rotationally energetic vortices for early injection timings. This improved bowl is fabricated and used in the current study in a medium-duty diesel engine, and its performance is compared against that with the production SL piston.

Spray-wall interactions in diesel engines have a strong influence on turbulent flow evolution and mixing, which influences the engine’s thermal efficiency and pollutant-emissions behavior. Previous optical experiments and numerical investigations of a stepped-lip diesel piston bowl focused on how spray-wall interactions influence the formation of squish-region vortices and their sensitivity to injection timing. Such vortices are stronger and longer-lived at retarded injection timings and are correlated with faster late-cycle heat release and soot reductions, but are weaker and shorter-lived as injection timing is advanced. Computational fluid dynamics (CFD) simulations predict that piston bowls with more space in the squish region can enhance the strength of these vortices at near-TDC injection timings, which is hypothesized to further improve peak thermal efficiency and reduce emissions. The dimpled stepped-lip (DSL) piston is such a design.In this study, the in-cylinder flow is simulated with a DSL piston to investigate the effects of dimple geometry parameters on squishregion vortex formation via a design sensitivity study. The rotational energy and size of the squish-region vortices are quantified. The results suggest that the DSL piston is capable of enhancing vortex formation compared to the stepped-lip piston at near-TDC injection timings. The sensitivity study led to the design of an improved DSL bowl with shallower, narrower, and steeper-curved dimples that are further out into the squish region, which enhances predicted vortex formation with 27% larger and 44% more rotationally energetic vortices compared to the baseline DSL bowl. Engine …

With the exponentially increasing computational power of modern computers, multi-dimensional computational fluid dynamicsComputational fluid dynamics (CFD) has found more and more applications in diesel engine research, design, and development since its initiation in the late 1970s. Enhanced understanding of the physical processes of diesel combustionCombustiondiesel and correspondingly improved numerical models and methods have both driven simulations using multi-dimensional CFDMulti-dimensional CFD tools from qualitative description towards quantitative prediction. To numerically resolve the complex physics of diesel combustion requires modelling of turbulent flows, high-pressure spray developmentSpraydevelopment, as well as combustion chemistry and relevant mechanism of pollutant formation. This chapter reviews the basic approach of multi-dimensional CFD modelling of diesel …

The adverse environmental impact of fossil fuel combustion in engines has motivated research towards using alternative low-carbon fuels. In recent years, there has been an increased interest in studying the combustion of fuel mixtures consisting mainly of hydrogen and carbon monoxide, referred to as syngas, which can be considered as a promising fuel toward cleaner combustion technologies for power generation. This paper provides an extensive review of syngas production and application in internal combustion (IC) engines as the primary or secondary fuel. First, a brief overview of syngas as a fuel is presented, introducing the various methods for its production, focusing on its historical use and summarizing the merits and drawbacks of using syngas as a fuel. Then its physicochemical properties relevant to IC engines are reviewed, highlighting studies on the fundamental combustion characteristics, such as …

In order to successfully cope with the trend of mitigating climate change as outlined in the recommendations of Paris (COP21) and Glasgow (COP26) Climate Agreements, propulsion technologies must be able to achieve the highest CO2 reduction, within very short time scales. To achieve this challenging goal, electric powertrains powered by batteries charged using renewable energy represents not only a public mandate but also the focus of research efforts of the relevant academic and industrial communities. However, this technology cannot answer all the various needs concerning personal mobility, sustainability and feasibility. Hence, in parallel an important role will be played by internal combustion engines (ICE) fed with non-fossil hydrocarbons and hydrogen (H2). 1 Today, internal combustion engines using fossil fuels generate about 25% of the world’s power and they are responsible for about 17% of the …

Recent research on thermal reciprocating engines has focused on the influence of lubricant oil on the combustion process, which can lead to highly undesired super-knock events. Low-Speed Pre-Ignition (LSPI) events severely limit the further development of Direct Injection Spark Ignition Engines (DISI), preventing high efficiencies from being achieved.However, there is still a lack of knowledge about the fundamental mechanisms leading to LSPI, due to the complex phenomena involved and the interaction between lubricant oil and fuel. Understanding how the presence of lubricant oil traces affects gasoline chemical reactivity is an essential step for performing successful numerical simulations aimed at predicting the onset of LSPI phenomena. Reaction mechanisms able to predict oil-fuel

Reactivity-controlled compression ignition (RCCI) is a promising energy conversion strategy to increase fuel efficiency and reduce nitrogen oxide (NOx) and soot emissions through improved in-cylinder combustion process. Considering the significant amount of conducted research and development on RCCI concept, the majority of the work has been performed under steady-state conditions. However, most thermal propulsion systems in transportation applications require operation under transient conditions. In the RCCI concept, it is crucial to investigate transient behavior over entire load conditions in order to minimize the engine-out emissions and meet new real driving emissions (RDE) legislation. This would help further close the gap between steady-state and transient operation in order to implement the RCCI concept into mass production. This work provides a comprehensive review of the performance and …

Increasing thermal and fuel efficiency in Internal Combustion Engines (ICEs) requires thorough investigations on the combustion process and its thermodynamics. The first law of thermodynamics expresses the balance of the energy, while the second law specifies the maximum achievable work. In this article, Low-Temperature Combustion (LTC) strategies, including Homogeneous Charge Compression Ignition (HCCI), Reactivity Controlled Compression Ignition (RCCI), Partially Premixed Combustion (PPC), and Direct Dual-Fuel Stratification (DDFS) were analyzed by the first and second law approaches, and they were compared with ideal-diesel cycle and Conventional Diesel Combustion (CDC). HCCI and RCCI had the highest exergy efficiency of 50.8% and 49.2%, respectively, compared to other cases, and exergy destruction in these cases was the lowest (25.3% and 27.5%, respectively). Although all …

Direct Dual Fuel Stratification (DDFS) is a novel LTC strategy among other strategies which uses two direct injectors in the combustion chamber, similar to Reactivity-Controlled Compression Ignition (RCCI), but resulting in more authority over the combustion process and the rate of heat release. DDFS has comparable thermal efficiency to RCCI and HCCI, as well as extra-low NOx and soot emissions, and it also is able to meet the EURO6 emission mandate without using aftertreatment under optimized conditions. Thus, it is crucial to optimize the injection strategy of both injectors in a DDFS engine. Artificial Neural Networks (ANNs) are used to develop a model for predicting engine performances and pollution. A multi-objective optimization analysis was performed to minimize NOX, soot and fuel consumption simultaneously using the non-dominated sorting genetic algorithm (NSGA-II) for the injection parameters of …

Appropriate spray modeling in multidimensional simulations of diesel engines is well known to affect the overall accuracy of the results. More and more accurate models are being developed to deal with drop dynamics, breakup, collisions, and vaporization/multiphase processes; the latter ones being the most computationally demanding. In fact, in parallel calculations, the droplets occupy a physical region of the in-cylinder domain, which is generally very different than the topology-driven finitevolume mesh decomposition. This makes the CPU decomposition of the spray cloud severely uneven when many CPUs are employed, yielding poor parallel performance of the spray computation. Furthermore, mesh-independent models such as collision calculations require checking of each possible droplet pair, which leads to a practically intractable O (np 2/2) computational cost, np being the total number of droplets in the …

Most multidimensional engine simulations spend much time solving for non-equilibrium spray dynamics (atomization, collision, vaporization). However, their accuracy is limited by significant grid dependency, and the need for extensive calibration. This is critical for modeling cold-start diesel fuel post injections, which occur at low temperatures and pressures, far from typical model validation ranges. At the same time, resolving micron-scale spray phenomena would render full Eulerian multiphase calculations prohibitive. In this study, an improved phase equilibrium based approach was implemented and assessed for simulating diesel catalyst heating operation strategies. A phase equilibrium solver based on the model by Yue and Reitz [1] was implemented: a fully multiphase CFD solver is employed with an engineering-size engine grid, and fuel injection is modeled using the standard Lagrangian parcels approach …

While forced induction strategies such as turbocharging can increase the power output and extend the load limit of engines operating on low temperature combustion strategies such as reactivity controlled compression ignition, the low exhaust enthalpy prevalent in these strategies requires the use of high backpressures to attain high turbocharger efficiencies, leading to high pumping losses and in turn poor fuel economy. Hence, there is a need to improve the exhaust energy utilization by the turbocharger such that the negative effects of the high backpressure requirements are offset. One turbocharger operating strategy that has the potential to enhance exhaust enthalpy conversion by the turbine is active control turbocharging (ACT), in which the rack position of a variable geometry turbocharger (VGT) is actuated using a continuously varying sinusoidal signal whose frequency is proportional to engine speed. In this study, the impact of ACT on turbocharger performance and fuel economy of a light-duty reactivity controlled compression ignition engine equipped with a VGT is investigated through coupled GT-POWER/KIVA-3V simulations at a medium-load cruise operating condition. A design of experiments study was executed in which the rack position amplitude and phase angle were independently varied, and the turbine efficiency, compressor efficiency, crankshaft torque, and brake specific fuel consumption were tracked for each run. The results show that ACT operation significantly increased the torque output while improving fuel economy over baseline VGT operation, but the range of actuation signal amplitude ratio was limited to 40% of the …

A one-dimensional, non-equilibrium, compressible law of the wall model is proposed to increase the accuracy of heat transfer predictions from computational fluid dynamics (CFD) simulations of internal combustion engine flows on engineering grids. Our 1D model solves transient turbulent Navier-Stokes equations for mass, momentum, energy and turbulence under the thin-layer assumption, using a finite-difference spatial scheme and a high-order implicit time integration method. A new algebraic eddy-viscosity closure, derived from the Han-Reitz equilibrium law of the wall, with enhanced Prandtl number sensitivity and compressibility effects, was developed for optimal performance, after several eddy viscosity sub-models were tested for turbulence closure, including the two-equation kepsilon and k-omega, which gave insufficient performance. Validation against pulsating channel flow experiments highlighted the superior capability of the 1D model to capture transient near-wall velocity and temperature profiles, and the need to appropriately model the eddy viscosity using a low-Reynolds method, which could not be achieved with the standard two-equation models. The results indicate that the non-equilibrium model can capture the near-wall velocity profile dynamics (including velocity profile inversion) while equilibrium models cannot, and simultaneous heat flux prediction errors are reduced by up to one order of magnitude. The proposed optimal configuration reduced heat flux error for the pulsating channel flow case from 18.4%(Launder-Spalding law of the wall) down to 1.67%.

Internal combustion (IC) engines played a key role in the industrial revolution and the progress of civilization. IC engine research has been ongoing to achieve higher efficiency and lower pollutant emissions, motivated by the energy dilemma, global warming, and increasingly stringent emissions standards. The compression ignition (CI) engine, that is, the diesel engine, is widely used in both stationary and mobile applications, and has drawn increasing interest in recent decades because of its promising potentials in efficient and clean combustion. Although emission after-treatment systems, such as the diesel particle filter (DPF), lean NOx trap (LNT), and selective catalytic reduction (SCR) are effective in the reduction of tailpipe emissions, they also have problems of cost, durability, and fuel economy penalty. Therefore, intense research has been focused on in-cylinder technologies, such as multiple injections …

Low temperature combustion strategies have demonstrated high thermal efficiency with low pollutant emissions (e. g., oxides of nitrogen and particulate matter), resulting from reduced heat transfer losses and lean air-fuel mixtures. One such advanced compression ignition combustion strategy, Reactivity Controlled Compression Ignition (RCCI), has demonstrated improved control over the heat release event due to the introduction of in-cylinder stratification of equivalence ratio and chemical reactivity via direct injection of a high-reactivity fuel into a premixed low-reactivity fuel/air mixture. The nature of the RCCI strategy provides inherent fuel flexibility, however, the direct injection strategy must be tailored to the combination of premixed and direct injected fuel chemistry and engine operating conditions to optimize efficiency and emissions. In this work, a 0-D methodology for predicting the required fuel stratification for a desired heat release rate profile for kinetically controlled stratified-charge combustion strategies is proposed. The methodology, referred to as Fuel Stratification Analysis (FSA), was inspired by a similar approach which utilized ignition predictions calculated via a Livengood-Wu integral approach correlated with experimental heat release profiles to determine in-cylinder temperature stratification in homogeneous charge compression ignition (HCCI) combustion. The methodology proposed in this work expands upon this method to include strategies involving fuel stratification (such as RCCI). Reacting and non-reacting CFD simulations were performed with the KIVA3V release 2 code to validate the CFD. Reacting simulations were …

Internal combustion (IC) engines operating on fossil fuel oil provide about 25% of the world’s power (about 3000 out of 13,000 million tons oil equivalent per year—see Figure 1), and in doing so, they produce about 10% of the world’s greenhouse gas (GHG) emissions (Figure 2). Reducing fuel consumption and emissions has been the goal of engine researchers and manufacturers for years, as can be seen in the two decades of ground-breaking peer-reviewed articles published in this International Journal of Engine Research (IJER). Indeed, major advances have been made, making today’s IC engine a technological marvel. However, recently, the reputation of IC engines has been dealt a severe blow by emission scandals that threaten the ability of this technology to make significant and further contributions to the reduction of transportation sector emissions. In response, there have been proposals to replace …

Direct dual fuel stratification (DDFS) strategy benefits the advantages of the RCCI and PPC strategies simultaneously. DDFS has improved control over the heat release rate, by injecting a considerable amount of fuel near TDC, compared to RCCI. In addition, the third injection (near TDC) is diffusion-limited. Consequently, piston bowl geometry directly affects the formation of emissions. The modified piston geometry was developed and optimized for RCCI by previous scholars. Since all DDFS experimental tests were performed with the modified piston profile, the other piston profiles need to be investigated for this strategy. In this article, first, a comparative study between the three conventional piston profiles, including the modified, stock, and scaled pistons, was performed. Afterward, the gasoline injector position was shifted to the head cylinder center for the stock piston. NOX emissions were improved; however …

One promising pathway to directly control combustion is Direct Dual Fuel Stratification (DDFS). DDFS has comparable thermal efficiency to RCCI, acceptable levels of emissions, and lower cyclic variation. The primary drawback of DDFS is soot production owing to the diffusion-limited nature of the near-TDC injection. In this paper, E10 (10% ethanol in gasoline by volume) and E85 were studied as alternative fuels to gasoline to tackle soot formation. In the first step, E10 and E85 were compared, and the best alternative to gasoline was chosen based on emissions and performance. E10 reduced soot by 40%, and E85 eradicated soot completely. However, E85 had 25 times higher NOX than gasoline. Next, diesel energy fraction and its start of injection (SOI2) were swept to explore the domain of the reactivity controlled regime. It was found that for SOI2s before −80° ATDC, the regime was premixed, and for SOI2s after …

Lagrangian spray modeling represents a critical boundary condition for multidimensional simulations of in-cylinder flow structure, mixture formation and combustion in internal combustion engines. Segregated models for injection, breakup, collision and vaporization are usually employed to pass appropriate momentum, mass, and energy source terms to the gas-phase solver. Careful calibration of each sub-model generally produces appropriate results. Yet, the predictiveness of this modeling approach has been questioned by recent experimental observations, which showed that at trans-and super-critical conditions relevant to diesel injection, classical atomization and vaporization behavior is replaced by a mixing-controlled phase transition process of a dense fluid. In this work, we assessed the shortcomings of classical spray modeling with respect to real-gas and phase-change behavior, employing a …

Interactions between fuel sprays and stepped-lip diesel piston bowls can produce turbulent flow structures that improve efficiency and emissions, but the underlying mechanisms are not well understood. Recent experimental and simulation efforts provide evidence that increased efficiency and reduced smoke emissions coincide with the formation of long-lived, energetic vortices during the mixing-controlled portion of the combustion event. These vortices are believed to promote fuel-air mixing, increase heat-release rates, and improve air utilization, but they become weaker as main injection timing is advanced nearer to the top dead center (TDC). Further efficiency and emissions benefits may be realized if vortex formation can be strengthened for near-TDC injections. This work presents a simulation-based analysis of turbulent flow evolution within a stepped-lip combustion chamber. A conceptual model summarizes …

Fuel injection rate laws are one of the most important pieces of information needed when modeling engine combustion with computational fluid dynamics. In this study, a simple phenomenological model of a common-rail injector was developed and calibrated for the Bosch CRI2.2 platform. The model requires three tunable parameter fits, making it relatively easy to calibrate and suitable for injector modeling when high-fidelity information about the internal injector’s geometry and electrical circuit details are not available. Each injection pulse is modeled as a sequence of up to four stages: an injection needle mechanical opening transient, a full-lift viscous flow inertial transient, a Bernoulli steady-state stage, and a needle descent transient. Parameters for each stage are obtained as polynomial fits from measured injection rate properties. The model enforces total injected mass, and the intermediate stages are only …

Applying a suitable design optimization technique is a crucial task for optimizing compression ignition engines because of the time-consuming process of optimization even with advanced supercomputers. Traditional computational fluid dynamics (CFD) used in conjunction with design of experiment (DOE) methods requires executing the CFD model several times. A response surface is usually fitted to relate the inputs to the outputs, which is often created based on linear regression. This method is not well suited to capture interaction effects between inputs and nonlinearities existing during engine combustion. A combination of genetic algorithm (GA) and CFD tools usually eventuates better optimum results. However, the CFD simulations must be executed sequentially, resulting in extremely high computational times, which makes it impossible to apply an optimization study using a single desktop computer. The …

Recent research highlights the influence of the presence of lubricant oil droplets on the combustion process in Direct Injection Spark Ignition (DISI) engines. Lubricant oil is considered to be the main responsible agent for the onset of pre-ignition phenomena, which can escalate highly undesired super-knock events. Moreover, lubricant oil plays a primary role in the generation of very fine soot particle emissions. In the present work, a reduced reaction mechanism is developed for modeling the combustion of gasoline-oil mixtures, allowing one to simulate the variation in ignitability of gasoline-like fuels induced by the presence of lubricant oil. In this study, a single hydrocarbon species, namely n-Hexadecane (n-C16H34), is shown to reproduce lubricant oil chemical and physical characteristics. Great effort has been performed to identify the most significant reaction pathways to reduce the complexity of the chemistry …