Search

In this study, a 1D model was created using the Ricardo-Wave program for a single-cylinder, spark ignition, four-stroke, direct injection engine with a stroke volume of 398 cc. Air-fuel ratio (AFR), mixture temperature (MT), and start of injection (SOI) were used as fuel injection parameters. Using these parameters, 343 different cases were created. Brake power, thermal efficiency, and fuel consumption were used as engine performance parameters. By holding one injection parameter constant, a contour plot was created to examine the effect of the other two parameters on the engine performance parameter. According to the results, the effect of MT and SOI on brake power is 1%, the effect of AFR on brake power is 9.6%, the effect of MT and SOI on thermal efficiency is 1%, and the effect of AFR on thermal efficiency is 12.8%. The effect of MT and SOI on fuel consumption is 0.04%, the effect of AFR on fuel consumption is 22.9%, and the effect of AFR on brake specific fuel consumption is 22.9%. These results indicate that the most significant effect is provided by AFR, while MT and SOI also have a slight impact on engine performance. [ABSTRACT FROM AUTHOR]

The understanding of the ignition process is important for many practical and fundamental applications including safety, chemical conversion, flame stabilization, and internal combustion engines operation. The ignition process can be influenced by many factors, including the pre-ignition turbulence level. Turbulence can generally be generated intentionally by the introduction of gases into the combustion chamber, but it can also occur unintentionally, for example by a sudden release of gases into the atmosphere as a result of an accident. Through the small scale 20 L CFD simulations of the ignition process of a stoichiometric methane-air mixture at different ignition energies and levels of turbulence, the present work aims to create a simple operational map that correlates the ignition energy with the degree of turbulence to understand in which areas flame propagation is successful and in which it is not. Such a tool may be useful both for evaluating the operation of internal combustion engines, where ignition and flame propagation are desired phenomena, and for a preliminary assessment of the risk and probability of ignition. This approach may also be applied in the future to other gaseous (as in the case of hydrogen), liquid, or solid systems. [ABSTRACT FROM AUTHOR]

The development and renewal of the transport sector is a continuous and never-ending process. The technological revolution in the automotive industry has been discussed for a while. Vehicles with internal combustion engines, which are considered to be polluting, should be replaced by non-polluting or significantly less polluting ones. Recently, European countries are experiencing a major energy crisis. Both petroleum products and electricity are becoming more expensive, so vehicle consumers are increasingly asking the question, which is better: a vehicle with an internal combustion engine or an electric vehicle? This article examines the possibilities and perspectives of the development of electric vehicles in Lithuania, based on the best practices of other countries. [ABSTRACT FROM AUTHOR]

This work presents a simplified methodology for coupling the physics of a nanosecond-pulsed discharge to the process of supersonic combustion within a backward-facing step combustor. The phenomena of plasma and supersonic combustion are simulated separately and then coupled. Based on results reported in the literature, a zero-dimensional plasma model is built, considering only the kinetic effects of the nanosecond-pulsed discharge. A set of Favre-averaged compressible Navier-Stokes equations, as well as finite rate chemistry, is used in the combustion model and solved with a control-volume based technique. The plasma-supersonic combustion coupling process only considers the discharge as a source of O and H radical species. The calculated densities of the radicals generated during each pulse from the plasma model are periodically seeded inside the domain of the combustor. The proposed methodology is used to perform a novel simulation that involved the application of plasma to a wellknown supersonic combustion experiment. The temperature and species concentration contours show that the proposed methodology captures the main effects of the nanosecond-pulsed discharge on supersonic combustion. The ignition delay time is reduced when the plasma discharge was applied. In addition, the simulations show that the plasma causes a supersonic lowenthalpy mixture to ignite, confirming the capability of the methodology. [ABSTRACT FROM AUTHOR]

The N47 engine debuted in March 2007 in the facelifted BMW 1 Series E87 and E81 and was also available in the BMW 1 Series E82 and E88, which were introduced the same year. The N47 engine replaced the M47 engine that had been in production for 8 years. The M47 construction underwent several modifications, so the injection system was changed, the cylinder head now consists of two parts, and the engine block is made of aluminium. Two main versions of the N47 engine are known: N47D16 (1.6 L) and N47D20 (2.0 L). In the case of both versions, several models with different performances were born. After the distribution of BMW passenger cars equipped with the N47D20 engine, it received a lot of negative criticism due to malfunctions. In this article, I would like to present the maintenance of the engine, which can be used to avoid the failure of passenger cars equipped with the N47D20 diesel engine with huge material damage. [ABSTRACT FROM AUTHOR]

A way based on the temperature effect is investigated to adjust the longitudinal wave band gaps of one-dimensional epoxy/Terfenol-D phononic crystals. For both the cases (with and without consideration of demagnetization effect), the dependences of component materials' effective parameters on temperature are obtained by applying a nonlinear mechanical-magneto-thermal coupling constitutive model and fitting the experimental data, respectively. Further, the influence of temperature on the band structure of wave propagation in phononic crystals consisting of epoxy and Terfenol-D is discussed in detail. Meanwhile, the effects of magnetic field, pre-stress, and filling fraction are studied. Numerical results show that temperature has a significant influence on the band structure of wave propagation in phononic crystals: As temperature rises from -40?°C to 40?°C , the widths of the first, second, and fourth band gaps increase, while that of the third band gap decreases. In addition, the demagnetization effect should not be ignored under a low magnetic field. [ABSTRACT FROM AUTHOR]

Epitaxial Ba2FeMoO6 thin films were grown via pulsed laser deposition under low oxygen pressure and their structural, chemical, and magnetic properties were examined, focusing on the effects of oxygen pressure. The chemical disorder, off-stoichiometry in B site cations (Fe and Mo) increased with increasing oxygen pressure and thus magnetic properties were degraded. Interestingly, in contrast, negative magneto-resistance, which is the characteristics of this double perovskite material, was enhanced with increasing oxygen pressure. It is believed that phase segregation of highly disordered thin films is responsible for the increased magneto-resistance of thin films grown at high oxygen pressure. The anomalous Hall effect, which behaves hole-like, was also observed due to spin-polarized itinerant electrons under low magnetic field below 1?T and the ordinary electron-like Hall effect was dominant at higher magnetic fields. [ABSTRACT FROM AUTHOR]

In order to ensure the safety of shore-based hydrogen bunkering operations, this paper takes a 2000-ton bulk hydrogen powered ship as an example. Firstly, the HAZID method is used to identify the hazards of hydrogen bunkering, then the probability of each scenario is analyzed, and then the consequences of scenarios with high risk based on FLACS software is simulated. Finally, the personal risk of bunkering operation is evaluated and the bunkering restriction area is defined. The results show that the personal risk of shore-based bunkering operation of hydrogen powered ship is acceptable, but the following risk control measures should be taken: (1) The bunkering restriction area shall be delineated, and only the necessary operators are allowed to enter the area and control the any form of potential ignition source; (2) The hose is the high risk hazards during bunkering. The design form of bunkering arm and bunkering hose is considered to shorten the length of the hose as far as possible; (3) A safe distance between shore-based hydrogenation station and the building outside the station should be guaranteed. The results have a guiding role in effectively reducing the risk of hydrogen bunkering operation. [ABSTRACT FROM AUTHOR]

The article presents results of scientific and experimental studies of the authors on operation of the tank equipment for ultrasonic purification of exhaust gases of internal combustion engines designed to reduce environmental pollution. The scheme of the experimental device implementing the principle of the tank equipment operation for ultrasonic cleaning of the motor vehicles exhaust gases is presented; the obtained experimental data of ultrasonic coagulation processes were processed and analyzed. Empirical relationships of the coagulation coefficient and its rate of change are derived from experimental data. [ABSTRACT FROM AUTHOR]

The magnetization behavior of a Permalloy thin-film (nominally Ni81Fe19) was investigated as a function of combined quasistatic and pulsed magnetic fields measured using magneto-optic Kerr effect magnetometry. We observed complex field dependent switching behavior that depends on the relative contributions to the total field of the quasistatic and pulsed fields. As the pulsed field amplitude was increased, complex switching behavior occurs for total fields in excess of the coercive field. A simple phenomenological domain wall propagation model suggests a qualitative understanding of this complex behavior based on Walker breakdown of the domain wall motion occurring in the Permalloy thin-film. [ABSTRACT FROM AUTHOR]

The aim of this paper is to review recent progress in detection and quantification of hydroperoxides, and to understand their reaction kinetics in combustion environments. Hydroperoxides, characterized by an OOH group, are ubiquitous in the atmospheric oxidation of volatile organic compounds (∼300 K), and in the liquid and gas phase oxidation of fuel components at elevated temperatures (∼400–1000 K). They are responsible for two-stage fuel ignition in internal combustion engines and they play an important role in the formation and evolution of secondary organic aerosols in the atmosphere. The introduction outlines the importance of hydroperoxide chemistry in combustion reaction processes. In addition to this main topic, the role of hydroperoxides in atmospheric and liquid phase oxidation chemistry is also introduced, for a more general perspective. The second part of this paper briefly reviews the mechanistic insights of hydroperoxide chemistry in combustion systems, including experimental detection of these reactive species before 2010. Since that time significant progress has been made by advanced diagnostic techniques like tunable synchrotron vacuum ultraviolet photoionization mass spectrometry and infrared cavity ring-down spectroscopy. The third chapter of this work summarizes progress in gas phase oxidation experiments to measure hydrogen peroxide, alkyl hydroperoxides, olefinic hydroperoxides, ketohydroperoxides, and more complex hydroperoxides that include as many as five oxygen atoms. The fourth section details recent advances in understanding the combustion chemistry of hydroperoxides, involving the formation of carboxylic acids and diones, as well as the development of oxidation models that include a third O 2 addition reaction mechanism. Finally, challenges are discussed, and perspectives are offered regarding the future of accurately measuring molecule-specific hydroperoxide concentrations and understanding their respective reaction kinetics. [ABSTRACT FROM AUTHOR]

Automotive manufacturers nowadays are constantly working on improving their internal combustion engines' performance by reducing the fuel consumption and emissions, without compromising the power generated. Manufacturers are therefore relying on virtual engine models that can be run on simulation software in order to reduce the amount of time and costs needed, in comparison with experiments done on engine test benches. One important element of the intake system of an internal combustion engine is the throttle valve, which defines the amount of air reaching the plenum before being drawn into the cylinders. This article discusses a widely used model for the estimation of air flow rate through the throttle valve in an internal combustion engine simulation. Experiments have been conducted on an isolated throttle valve test bench in order to understand the influence of different factors on the model's discharge coefficient. These experiments showed that the discharge coefficient varies with the pressure ratio across the throttle valve and with its angle. Furthermore, for each angle, this variation can be approximated with a linear model composed of two parameters: the slope and the Y-Intercept. These parameters are calibrated for different throttle valve angles. This calibration can be done using automotive manufacturers' standard engine test fields that are often available. This model is then introduced into an engine simulation model, and the results are compared to the experimental data of a turbocharged engine test bench for validation. They are also compared with a standard discharge coefficient model that varies only with the throttle valve angle. The results show that the new model for the discharge coefficient reduces mass flow estimation errors and allows expanding the applications of the throttle valve isentropic nozzle model. [ABSTRACT FROM AUTHOR]

Abstract Biobutanol has demonstrated to be a superior alternative biofuel in internal combustion engine (ICEs). Acetone-butanol-ethanol (ABE) fermentation engineering is a typical technique for biobutanol production. However, the high costs and extra energy consumption in recovery process of biobutanol from intermediate fermentation solvent (i.e. ABE mixture) has obstructed its large-scale application. It is gaining increasing attention to investigate ABE as a potential alternative biofuel. ABE production and ABE combustion in ICEs have been widely studied, but these studies are rarely reviewed to favor understanding and popularization for ABE so far. In this work, the updated progress of ABE fermentation techniques is first summarized from the aspects: (i) selection of suitable strain; (ii) availability of cheaper substrates; (iii) development of fermentation engineering. Then, the research on ABE combustion in ICEs are concluded from the aspects: (i) physicochemical properties and tests in ICEs of ABE components; (ii) substitute for diesel in compression ignition engines; (iii) substitute for gasoline in spark ignition engines. These studies demonstrate that ABE is a better alternative for gasoline or diesel fuel due to the environmentally benign manufacturing process and the potential to improve energy efficiency and reduce pollutant emissions. However, ABE has not been intensively studied when compared to conventional alternative fuels (e.g. ethanol, butanol, biodiesel, etc.), for which considerable numbers of reports are available. Therefore, some challenges and future research directions are outlined in the end. This review is helpful for finding opportunities to make ABE as a feasible alternative biofuel in near future. [ABSTRACT FROM AUTHOR]

Nanodisk array with both sandwich structure of Au/ [Co/ Pt]n /Au and [Co/ Pt]n were fabricated by electron-beam lithography combined with ion milling process. Optical transmittance spectra revealed the excitation of localized surface plasmon resonance (LSPR) in Au/ [Co/ Pt]n /Au nanosandwich array. Magneto-optical (MO) properties were measured by a micro-Faraday system with objective lens design and laser source. Faraday rotation angle for sandwich structure increased considerably compared to that of [Co/ Pt]n, indicating enhancement in MO activity by excitation of LSPR. The optical and MO properties of nanosandwich array were fitted in the framework of average field approximation. [ABSTRACT FROM AUTHOR]

In this article, the overall combustion characteristics of non-edible linseed (Linum usitatissimum) biodiesel blended with petrodiesel (PD) are presented. The objective of the present study is to investigate the effect of a fraction of biodiesel in the blends, the variation of load (20 to 100% in a step of 20%) and compression ratio (CR) (14:1, 16:1, and 18:1) on combustion characteristics. The obtained result, compared with baseline fuel PD, is operated at rated CR 17.5:1. The result shows the higher value of cylinder combustion pressure (CP), a rate of pressure rise (RPR), cumulative heat release, combustion duration, and combustion mean gas temperature and lower ignition delay (ID) for biodiesel and its blends compared with PD. On an average, the ID increased by 30% and 3.3% at CR 14:1 and 16:1, respectively, and reduced by 28.3% at CR 18:1 for LB blends. [ABSTRACT FROM AUTHOR]

8 different natural stone types were exposed to exhaust gas under laboratory conditions to assess urban stone damage. 3 cm in diameter cylindrical test specimens were made from travertine, non-porous limestone, limestone, rhyolite tuff, sandstone, andesite, granite and marble. The samples were exposed for 1, 2, 4 and 8 hours to exhaust gas that was generated by compression ignition internal combustion engine. The exhaust emission was measured. The operating conditions of the engine were documented and several parameters (weight, density, ultrasonic pulse velocity, capillary water absorption, porosity) were measured before and after exhaust gas exposure. The tests indicate that despite the deposition of soot on the surface a significant material loss was recorded at rhyolite tuff (2m%) and at andesite (1m%). The penetration depth of soot was also different for different lithologies. A correlation was found between the ultrasonic pulse velocity and density of tested stones. [ABSTRACT FROM AUTHOR]

Fuel atomization in diesel compression ignition engines is significantly affected on the performance, evaporation, self-ignition, and emissions of the engine. Therefore, the quality of the spray atomization has to study at first. Algae-Derived renewable diesel fuel in a single hole nozzle atomizer has been chosen as an alternative fuel for diesel. The differences in physical properties of algae-derived renewable diesel, biodiesels (from palm and cooked oil) and pure diesel are effected on both spray characteristics and the internal nozzle flow. Numerical simulations are presented in this study using Eulerian-Eulerian technique to model the spraygas interaction. The spray moments model has been used to characterize the spray parameters. First, the model is validated against the spray tip penetration of diesel spray characteristics obtained from the experimental data conducted in house-code using constant volume spray chamber and the results show a good agreement. Then, comparisons were made among the selected fuels. The numerical simulations show that the algae-derived renewable diesel is very similar to pure diesel and can be used as an alternative fuel. [ABSTRACT FROM AUTHOR]

Highlights • Drived by the same power supply, MCPI generates 5 times more ignition energy than SI. • CH intensity of MCPI was 2.2 times larger than that of conventional SI. • Ignition time of MCPI was reduced by approximately 50%. • Lean ignition limit of scramjet combustor was extended by 20–26% through MCPI. Abstract Reliable and fast ignition of scramjet engine is quite important in consideration of high velocity and low pressure of inlet air. Successful ignition requires that sufficient ignition energy be injected into the flame kernel so that the flame propagates outwardly beyond the critical initial radius of the critical flame. Larger critical flame initiation radius is required during the preliminary stage of scramjet engine so advanced ignition technology for scramjet engines is urgently needed. In this study, multichannel plasma igniter (MCPI) is proposed to induce a relatively larger ignition kernel for the purpose of achieving successful ignition in scramjet engines. Ignition experiments in a model scramjet combustor fueled by ethylene were conducted with inflow conditions of Ma = 2.52, stagnation pressure P 0 = 1.6 MPa and stagnation temperature T 0 = 1600 K. Ignition processes of SI and MCPI at different fuel injection schemes were captured by CH∗ chemiluminescence imaging and flame luminosity imaging technology. Results reveal that MCPI with five channels generates 5 times more ignition energy than SI and MCPI can generate much larger plasma volume and activated area which can induce a relatively larger initial flame kernel. The CH intensity of MCPI was about 2.2 times larger than that of conventional SI. Besides, it was shown that the lean ignition limit of scramjet combustor through MCPI was extended by 20–26% than that through SI and the ignition time was reduced by approximately 50%. MCPI with an injection 10 mm upstream the cavity demonstrates the best performance in this study. [ABSTRACT FROM AUTHOR]

Results of numerical and experimental investigations of a high-velocity flow in a plane channel with sudden expansion in the form of a backward-facing step, which is used for flame stabilization in a supersonic flow, are presented. The experiments are performed in the IT-302M high-enthalpy short-duration wind tunnel under the following test conditions: Mach number at the combustor entrance 2.8, Reynolds number 30 · 106 m−1, and total temperature T0 = 2000 K, i.e., close to flight conditions at M = 6. The numerical simulations are performed by solving full unsteady Reynolds-averaged Navier-Stokes equations supplemented with the k-ω SST turbulence model and a system of chemical kinetics including 38 forward and backward reactions of combustion of a hydrogen-air mixture. Three configurations of the backward-facing step are considered: straight step without preliminary actions on the flow, with preliminary compression, and with preliminary expansion of the flow. It is demonstrated that the backward-facing step configuration exerts a significant effect on the separation region size, pressure distribution, and temperature in the channel behind the step, which are the parameters determining self-ignition of the mixture. The computed results show that preliminary compression of the flow creates conditions for effective ignition of the mixture. As a result, it is possible to obtain ignition of a premixed hydrogen-air mixture and its stable combustion over the entire channel height. [ABSTRACT FROM AUTHOR]

Converting corncobs into fuel ethanol is different from converting stover because cobs have higher hemicellulose and lower lignin than stover. Current research provides life‐cycle assessments of greenhouse gas (GHG) emissions for stover ethanol but lacks such assessments for corncob ethanol. This study attempts to fill this gap by estimating the lifecycle energy consumption and carbon emissions for corncob ethanol using the GREET (Greenhouses gases, Regulated Emissions, and Energy use in Transportation) model. Our well‐to‐pump (WTP) estimate of fossil fuel consumption is 0.51–0.84 MJ MJ−1 of ethanol produced. The estimated GHG emissions are 39.44–49.97 gCO2eq/MJ of ethanol; about 90% is attributed to the conversion process. If glucose and xylose are co‐fermented, it requires 10% less energy and emits about 20% fewer GHGs from well to pump. The estimates are sensitive to the variations in corn yield and hydropower supply. Pump‐to‐wheel emissions are also assessed for representative vehicles with spark‐ignition engines in China. We find that hybrid and plug‐in hybrid electric vehicles have 18–20% lower emissions than internal combustion engine vehicles (ICEVs), and flexible‐fuel vehicles using E85 have similar WTP emissions to ICEVs. © 2018 Society of Chemical Industry and John Wiley & Sons, Ltd [ABSTRACT FROM AUTHOR]

A plug-in hybrid electric vehicle (PHEV) uses an internal combustion engine to extend its cruising range, and to produce the electric power needed to be supplied to its electric motor when the charge level of the vehicle's battery becomes low and reaches a predetermined state of charge (SOC). This paper provides a better solution by replacing the internal combustion engine of a PHEV with a small-size photovoltaic (PV) module located on the roof of the PHEV, and a micro wind turbine located in front of the PHEV, behind the condenser of the air conditioning system. Thus, this study proposes a novel battery/PV/wind hybrid power source to be utilized in PHEVs. The power source equipped with vehicle-to-grid (V2G) technology is composed of a 19.2-kWh Lithium (Li)-ion battery used as the main energy storage device, and a PV module and a wind energy conversion system. A prototype of the battery/PV/wind hybrid power source has been constructed and utilized in a PHEV. Experimental verifications are presented that demonstrate utilizing the PV module and micro wind turbine adds 19.6 km to the cruising range of a PHEV with the weight of 1880 kg during two sunny days, and provides higher power efficiency (91.2%) and speed (121 km/h). Highly accurate dc-link voltage regulation and producing an appropriate three-phase stator current for the traction motor by using pulse width modulation technique are the other contributions of this paper. [ABSTRACT FROM AUTHOR]

In these days, there is a paradigm shift from internal-combustion-engine vehicles to electric vehicles. Most electric vehicles developed include batteries mounted at the bottom, near the rear wheels. Hence, the robust design of underbody parts against the impact of external bodies or random stone chipping needs to be made. In this study, the mathematical modeling and statistical probability analysis of stone chipping and tire slip are performed for identifying and confirming the critical zones of the vehicle underbody that may be damaged by stone chipping. Thereby, stone chipping can be predicted by simulations using the employed mathematical model, before conducting experimental verification using the existing methods. Furthermore, the development cost and time can be reduced because the elements of the designed underbody can be analyzed for robustness, and the safety factor can be established during the design stage. [ABSTRACT FROM AUTHOR]

Knocking combustion has been extensively studied in internal combustion engines in order to achieve higher thermal efficiency. However, the inherent mechanism for knocking combustion under homogenous charge compression ignition (CI) conditions has not been fully understood. In this study, the strong knocking characteristics under CI conditions were parametrically investigated through theoretical analysis and rapid compression machine (RCM) experiments, with addressing knocking intensity (KI) limits and autoignition (AI) modes. The characteristic time and energy release concerned with AI were firstly numerically obtained through constant-volume adiabatic conditions. It is found that despite longer ignition delay time within milliseconds and excitation time within microseconds, iso-octane shows almost the same level of maximum explosive pressure and obvious higher energy density compared with n-heptane with low octane rating, indicating the potential of strong knocking occurrence. Then, knocking characteristics were investigated through RCM experiments operated under different thermodynamic conditions for the different octane rating fuels. It shows that strong knocking combustion characterizing super-knock events is observed for both n-heptane and iso-octane. Meanwhile, initial pressure showed greater impact on knocking combustion, manifesting significant increases in KI at high pressures. The influence from initial temperature becomes more obvious for iso-octane fuel at low pressures with long ignition delay time. Finally, the AI modes for different knocking scenarios were qualitatively assessed through Bradley’s diagram, allowing for the uncertainties of hot-spot sizes and temperature gradients. It shows that most AI modes of strong knocking combustion were located in the developing detonation regime, illustrating the possibility of super-knock under CI conditions with high thermodynamic conditions. [ABSTRACT FROM AUTHOR]

Autoignition of fuel/air mixtures is a determining process in internal combustion engines. Ignition can start either homogeneously in the gas phase after compression or in the vicinity of hot surfaces. While ignition properties of commercial fuels are conventionally described by a single quantity (octane number), it is known that some fuels have a varying propensity to the two processes. We present a new experimental concept that generates well-controlled temperature inhomogeneities in the shock-heated gases of a high-pressure shock tube. A shock-heated reactive mixture is brought into contact with a heated silicon nitride ceramic glow plug. The glow-plug temperature can be set up to 1200 K, higher than the post-reflected-shock gas temperatures (650–1050 K). High-repetition-rate chemiluminescence imaging is used to localize the onset of ignition in the vicinity of the hot surface. In experiments with ethanol, the results show that in most cases under shock-heated conditions, the ignition begins inhomogeneously in the vicinity of the glow plug and is favored because of the high wall temperature. Additionally, the interaction of geometry, external heating, and gas-dynamic effects was investigated by numerical simulations of the shock wave in a non-reactive flow. [ABSTRACT FROM AUTHOR]

Experimental studies with four different strut setups are conducted to investigate the effect of strut length on combustion performance of a trapped vortex combustor (TVC). The experimental results indicate that ignition, lean blowout (LBO) and combustion efficiency depend to a great extent upon the length of the strut. The longer struts show prominent advantages in terms of ignition and LBO, whereas the shorter ones perform rather poorly. Interestingly, the combustion efficiency achieved by the shorter struts is higher than the longer ones. Furthermore, RANS based simulations are also performed to explain the experimental results. From the detailed numerical simulations, it can be inferred that the poor ignition performance and LBO limits of the shorter struts are mainly caused by the great amount of mainstream air entrained into the cavity. And the higher combustion efficiency achieved by the shorter struts is mainly attributed to much more wake regions formed behind the struts. [ABSTRACT FROM AUTHOR]

Together with renewed legislations, the automotive industry and research centers continue their efforts to develop internal combustion engine (ICE) technologies that consume less fuel and more environmentally. The basic step in developing efficient and environmentally ICEs is to ensure that the parameters affecting the in-cylinder combustion and the exact combustion. Although there are many parameters that affect each other, such as fuel consumption, emissions and noise, the main source of these results is the in-cylinder combustion event. Control of combustion initiation, ignition delay, and combustion must be well understood as all output will affect it. Although many parameters in today’s ICE technology such as fuel temperature are controlled by sensors and instantly evaluated with Electronic Control Unit (ECU), optimization of feedback is provided by analyzing the factors affecting ignition delay. The factorial design method is used in this optimization study which examines the parameters of engine speed, load and fuel temperature. In this optimization study, it has been found that the engine speed, load and fuel temperature significantly influence ignition delay in different sizes. [ABSTRACT FROM AUTHOR]

Dual-pulse laser-induced plasma ignition of kerosene in cavity at model scramjet engine is studied. The simulated flight condition is Ma 6 at 30 km, and the isolator entrance has a Mach number of 2.92, a total pressure of 2.6 MPa and a stagnation temperature of 1650 K. Two independent laser pulses at 532 nm with a pulse width of 10 ns, a diameter of 12 mm and a maximum energy of 300 mJ are focused into cavity for ignition. The flame structure and propagation during transient ignition processes are captured by simultaneous CH* and OH* chemiluminescence imaging. The entire ignition process of kerosene can be divided into five stages, which are referred as turbulent dissipation stage, quasi-stable state, combustion enhancement stage, reverting stage and combustion stabilization stage. A local closed loop of propagations of the burning mixtures from the shear layer into the recirculation zone of cavity is revealed, which the large-scale eddy in the shear layer plays a key role. The enhancement of mass exchange between shear layer and the recirculation zone of cavity could promote the flame propagation process and enhance the ignition capability as well as extend the ignition limits. A cavity shear-layer stabilized combustion of kerosene is established in the supersonic flow roughly 3.3 ms after the laser pulse. Chemical reactions mainly occur in the shear layer and the near-wall zone downstream of the cavity. The distribution of OH* is thicker than CH* at stable combustion condition. [ABSTRACT FROM AUTHOR]

This article presents a non-resonant magneto-mechanical vibration energy harvester. When externally excited, the energy harvester converts vibrations into electric charge using a guided levitated magnet oscillating inside a multi-turn coil that is fixed around the exterior of the energy harvester. The levitated magnet is guided using four oblique mechanical springs. A prototype of the energy harvester is fabricated using additive manufacturing. Both experiment and model are used to characterize the static and dynamic behavior of the energy harvester. Measured restoring forces show that the fabricated energy harvester retains a mono-stable potential energy well with desired stiffness nonlinearities. Results show that magnetic spring results in hardening effect which increases the resonant frequency of the energy harvester. Additionally, oblique mechanical springs introduce geometric, negative, nonlinear stiffness which improves the harvester’s response towards lower frequency spectrum. The unique design can produce a tunable energy harvester with multi-well potential energy characteristics. A finite element model is developed to estimate the average radial flux density experienced by the multi-turn coil. Also, a lumped parameter model of the energy harvester is developed and validated against measured data. Both upward and downward frequency sweeps are performed to determine the frequency response of the harvester. Results show that at higher excitation levels hardening effects become more apparent, and the system dynamic response turns into non-resonant. Frequency response curves exhibit frequency jump phenomena as a result of coexistence of multiple energy states at the frequency branch. The fabricated energy harvester is hand-held and measures approximately 100.5 [cm 3 ] total volume. For a base excitation of 1.0 g [m/s 2 ], the prototype generates a peak voltage and normalized power density of approximately 3.5 [V] and 0.133 [mW/cm 3 g 2 ], respectively, at 15.5 [Hz]. [ABSTRACT FROM AUTHOR]

Lean combustion in gasoline engine can reduce nitrogen oxide emission and fuel consumption greatly. However, as the fuel-air ratio approaches the lean-burn limit, the energy required to initiate the combustion increases dramatically, and the flame propagation speed decreases substantially. To enhance the lean combustion and expand the lean-burn limit of a sparkignition engine, a high-voltage nanosecond pulsed plasma is introduced to initiate the combustion of the engine. Discharge process and chemical reactions are calculated separately due to an essential difference in their timescales. The effect of discharge induced active particles on the ignition of the gasoline engine is studied, which shows that the ignition is primarily associated with the faster development of chain reaction due to O and O3 produced by the electron-impact dissociation in the discharge phase; these active particles can greatly shorten ignition delay time. The combustion enhancement for lean mixture is more pronounced than the stoichiometric gases, which indicates that the nonequilibrium plasma has a great potential to extend the lean-burn limit. [ABSTRACT FROM AUTHOR]

Ignition delay times of dimethyl carbonate DMC were measured using low- and high-pressure shock tubes and in a rapid compression machine (RCM). In this way, the effect of fuel concentration (0.75% and 1.75%), pressure (2.0, 20, and 40 atm) and equivalence ratio (0.5, 1.0, 2.0) on ignition delay times was studied experimentally and computationally using a chemical kinetic model. Experiments cover the temperature range of 795–1585 K. Several models from the literature were used to perform simulations, thus their performances to predict the present experimental data was examined. Furthermore, the effect of the thermodynamic data of the CH 3 O(C O)Ȯ radical species and the fuel consumption reaction CH 3 O(C O)OCH 3 ⇄ CH 3 O(C O)Ȯ + ĊH 3 , on the simulations of the ignition delay times of DMC was analyzed using the different models. Reaction path and sensitivity analyses were carried out with a final recommended model to present an in-depth analysis of the oxidation of DMC under the different conditions studied. The final model uses AramcoMech 2.0 as the base mechanism and includes a DMC sub-mechanism available in the literature in which the reaction CH 3 O(C O)OCH 3 ⇄ CH 3 O(C O)Ȯ + ĊH 3 has been modified. Good agreement is observed between calculated and experimental data. The model was also validated using available experimental data from flow reactors and opposed flow diffusion and laminar premixed flame studies showing an overall good performance. [ABSTRACT FROM AUTHOR]

Transient mixing and ignition mechanisms in a simplified pre-chamber/main-chamber system are investigated using direct numerical simulation (DNS) with detailed chemical kinetics. Full ignition and flame propagation processes in the premixed methane/air mixtures are simulated. Ignition, the progress and topology of flame evolution, and the mean burning velocity in the main chamber are analyzed in detail. Four important phases in the ignition and flame propagation processes are identified based on the flame structure development in the main chamber, the pressure and velocity evolution at typical points in both the pre-chamber and main chamber. Results show that the intermediate species OH, CH 2 O, and HO 2 are critical for flame stabilization and propagation in the main chamber due to their high reactivity. This is sorted as the chemical effect that the pre-chamber jet acts on the main chamber. The high temperature jet also brings heat and unburned fuel into the main chamber, which are sorted as thermal and enrichment effect, respectively. The heat release rate is found to be approximately proportional to the product of CH 2 O and OH mass fractions, which could be regarded as a reliable and effective marker for the heat release rate of methane/air mixtures. It is found that the mean burning velocity in the main chamber can be elevated up to 30 times under the condition investigated. [ABSTRACT FROM AUTHOR]

The initial ignition characteristic of fuel spray in a diesel engine is of great significance in the cold start problem. In this paper, the constant volume combustion vessel was applied to simulate the practical diesel engine condition near the end of the compression stroke and investigate the autoignition threshold temperature and other ignition characteristics for the fuel spray such as ignition delay time and initial ignition location. First, the influence of the ambient temperature and the ambient density in the vessel on ignition delay time, initial ignition location, and fuel mixture autoignition threshold temperature was researched. Then, the influence of fuel injection pressure and the plate surface temperature on ignition delay time and initial ignition location were also investigated in this paper. The results have shown that the autoignition threshold temperature was approximately 803 K for the fuel spray in the combustion vessel, which simulated the practical diesel engine condition and the ignition delay time for both free jet and impinging jet increasing with the ambient temperature and the ambient density decreasing, respectively. The experimental map has also been developed to show the zone where initial ignition would occur with the different ambient temperatures and the ambient densities for the diesel fuel; the change of the injection pressure has no obvious influence on ignition delay time, but it reduces ignition success rate. The ignition delay time becomes longer as the plate surface temperature reduces and the variation rate of ignition delay time differs greatly in different temperature zones. [ABSTRACT FROM AUTHOR]

Being one typical cyclo-alkane class component of commercial jet and diesel fuels, decalin has two fused six-membered rings and so far few studies of decalin were accessible to its oxidation mechanism. So that this study aims to propose a skeletal mechanism of decalin oxidation that facilitates the formulating of surrogate fuels applicable in power device like engines. In this study, a skeletal mechanism of decalin oxidation was developed based on the decoupling methodology. It contains 42 species and 163 reactions, in which a simplified mechanism for the oxidation of C 2 –C 10 is used to model the oxidation of heavy hydrocarbons for the prediction of the ignition characteristics, while the mechanism of H 2 /CO/C 1 was considered in details for the prediction of intermediate species concentrations. Among all intermediate combustion products, C 2 H 2 is designated as the most important soot precursor and will be used to predict soot tendency in the future study. The present skeletal mechanism was extensively validated against available fundamental experiments in regard of decalin oxidation under engine relevant conditions, wherein the temperature and pressure were relatively high. The computational results indicated that the predicted ignition delay in shock tubes and species concentrations in jet stirred reactors as well as in laminar premixed flames agree reasonably well with the measurements. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Machine Construction & Maintenance is the property of Institute for Sustainable Technologies - National Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Straight vegetable oils may be a promising alternative to fossil diesel fuel. Fuels to be used in compression ignition engines have to meet several specifications, including the requirement of a certain ignition characteristic. The ignition characteristic is described by the cetane number of a fuel and measured using engine or constant volume combustion chamber device based methods. However, none of these standardized methods is directly applicable for straight vegetable oils. As a result cetane numbers of vegetable oils with the same origin and indicated in literature can vary by several cetane number units. Furthermore, the known cetane numbers of commonly used oils such as rapeseed or soybean oil are lower than that of conventional diesel fuel. In contrast, emission testing of these oils using modern diesel engines under high load conditions indicated an ignition behavior comparable to that of diesel fuel. Thus, the task of this research was to determine the ignition characteristic of nine different straight vegetable oils and two oil mixtures using a constant volume combustion chamber device equipped with a high pressure fuel injection system. The ignition characteristic was provided using primary reference fuel calibration. The calibration was done at different combustion chamber temperatures and injection pressure levels representing various engine load conditions. The determined ignition characteristics were expressed in terms of an estimated cetane number of vegetable oils (ECNO). In contrast to conventional diesel fuel, the ECNO of vegetable oils was found to be strongly influenced by both, combustion chamber temperature and injection pressure. With rising temperature and injection pressure, the ECNO was observed to increase and exceed that of diesel fuel for certain vegetable oils. Thus, it was recommended to use two ECNO to provide a meaningful definition of the ignition characteristic of vegetable oil fuels. One should reflect the ignition characteristic at low load engine points and was determined with an injection pressure of 500 bar and a combustion chamber temperature of 852 K. The other one should be valid for intermediate and high engine load conditions. This was determined using an injection pressure of 1000 bar at a temperature of 923 K. A high linear correlation could be found between the degree of saturation of the fatty acids present in the oils and their ECNO. The ECNO was higher for oils with a low amount of monounsaturated and especially polyunsaturated fatty acids. [ABSTRACT FROM AUTHOR]

Neat (100%) n-butanol was implemented in a direct injection (DI) compression ignition (CI) engine. The ignition, combustion, and emission characteristics at low engine load (below 6.5 bar IMEP), including near idling, were investigated. The engine experiments were performed using a modern common rail type single cylinder DI CI engine with a compression ratio of 18.2:1. Chemical kinetic simulations were also conducted to analyze the ignition characteristics of the experiments. The research results showed that neat n-butanol could not be auto-ignited at normal intake temperature and pressure conditions due to its low reactivity. However, the use of a high intake pressure of 0.75 bar gauge, and an injection timing of −26° ATDC at 5.0 bar IMEP, enabled auto-ignition even without the use of intake heating. One possible reason for this was attributed to the enhancement of the low temperature reaction regime. The ignition timing advancement sensitivity to intake pressure was approximately 1.0 °CA/0.1 bar at 5.0 bar IMEP, and a higher intake pressure allowed a wider injection timing range. A neat n-butanol fueled DI CI engine had a five times longer ignition delay and a 85% longer combustion duration than the same engine fueled with diesel at 2.0 bar IMEP. However, the combustion duration tended to shorten rapidly with increasing engine load, which was the opposite tendency to diesel. At low load, the nitrogen oxides (NOx) and soot emissions were very low compared to those of diesel, whereas the total hydrocarbons (THC), formaldehyde (HCHO), and carbon monoxide (CO) were higher than those of diesel. Carbon dioxide (CO 2 ) emission was lower than that of diesel. This could be due to the reduced CO oxidation and the lower carbon content in n-butanol. Finally, by combining the previously published results with these results in this research, fuel injection strategies and intake oxygen conditions required to achieve low NOx (≤0.60 g/kWh) and soot (≤0.02 g/kWh) emissions and moderated maximum cylinder pressure rise rate (≤10 bar/°CA) were summarized over a wide load range of 2.0–11.5 bar IMEP. [ABSTRACT FROM AUTHOR]

To study the effects of hydrogen direct injection strategies on the characteristics of combustion and emissions of hydrogen–gasoline engines, an experimental engine platform was built with gasoline intake injection and hydrogen direct injection. The effects of hydrogen injection pressure and injection timing at a minimum advance for the best torque on the characteristics of engine combustion and emissions were studied at a constant engine speed, air–fuel ratio, and hydrogen fraction. The test results showed that when the heat that was released in the cylinder was constant, a 10% hydrogen fraction had a significant influence on the engine’s performance, combustion, and emissions. Hydrogen direct injection greatly improved the combustion stability of lean-burn mixtures of the engine, and significantly improved the mean effective pressure and thermal efficiency. Hydrogen injection at optimum ignition timing would significantly shorten the flame-development period and rapid combustion duration. The heat release was more concentrated, which increased the cylinder pressure. With an excess air ratio of 1.5, the addition of hydrogen significantly reduced CO emissions, but HC emissions increased slightly. A lean burn could contribute to the reduction of NO x emissions, whereas the addition of hydrogen would increase it. [ABSTRACT FROM AUTHOR]

The aim of this study is to investigate the effects of nanoparticles type, nanoparticles size, and droplet size on the ignition probability of the diesel fuel. Also, the effect of metal oxide nanoparticles on the ignition delay of diesel fuel droplets is studied. A series of hot plate ignition tests are conducted for diesel fuel with and without Al 2 O 3 , TiO 2 and Fe 3 O 4 nanoparticles at different concentrations (up to 0.05 wt.%). The experimental results show that the ignition probability of the diesel fuel significantly increases in the presence of metal oxide nanoparticles. The ignition probabilities of diesel/Al 2 O 3 and diesel/Fe 3 O 4 nanofuels are almost similar and higher than that of diesel/TiO 2 nanofuel. Results for diesel/Al 2 O 3 show that the nanoparticle size does not affect the ignition probability of nanofuel. Moreover, results indicate that the ignition probability decreases by increasing the droplet size. Investigations show that the ignition delay for diesel fuel droplets decreases in the presence of Al 2 O 3 nanoparticles. [ABSTRACT FROM AUTHOR]

Straight vegetable oils attracted attention several times as alternative fuel for mobile machinery. Certain efforts have already been undertaken to enable the usage of the high viscous oils in compression ignition engines. While physical properties are well specified for different kind of oils, only few information is available on the ignition behavior of vegetable oils under modern engine like conditions. Therefore, the ignition behavior of nine different vegetable oils and two oil mixtures was investigated using the Advanced Fuel Ignition Delay Analyser (AFIDA). The AFIDA is a modern constant volume combustion chamber apparatus equipped with a high pressure injection system. Analysis was performed at combustion chamber temperatures ranging from 796 K to 967 K and at air density levels of 4.7 kg/m 3 , 9.3 kg/m 3 and 17.7 kg/m 3 . Ignition behavior was correlated to the structure indices average number of carbon atoms and average number of double bonds. Both were calculated using the fatty acid composition of the oils. Ignition delay decreased with rising temperature and air density. Coconut oil ignited first at every temperature except for the lowest air density level. Start of combustion was always last for linseed oil, followed by camelina and soybean oil. Ignition delay increased linearly with rising average number of double bonds and decreasing average number of carbon atoms. The effect of the average number of double bonds on ignition delay was more pronounced than that of carbon chain length. Fatty acids with two or more carbon-carbon double bonds led mostly to a stronger increase in ignition delay compared to those with only one double bond. [ABSTRACT FROM AUTHOR]

Rapid compression machines (RCMs) are widely used to acquire experimental insights into fuel autoignition and pollutant formation chemistry, especially at conditions relevant to current and future combustion technologies. RCM studies emphasize important experimental regimes, characterized by low- to intermediate-temperatures (600–1200 K) and moderate to high pressures (5–80 bar). At these conditions, which are directly relevant to modern combustion schemes including low temperature combustion (LTC) for internal combustion engines and dry low emissions (DLE) for gas turbine engines, combustion chemistry exhibits complex and experimentally challenging behaviors such as the chemistry attributed to cool flame behavior and the negative temperature coefficient regime. Challenges for studying this regime include that experimental observations can be more sensitive to coupled physical-chemical processes leading to phenomena such as mixed deflagrative/autoignitive combustion. Experimental strategies which leverage the strengths of RCMs have been developed in recent years to make RCMs particularly well suited for elucidating LTC and DLE chemistry, as well as convolved physical-chemical processes. Specifically, this work presents a review of experimental and computational efforts applying RCMs to study autoignition phenomena, and the insights gained through these efforts. A brief history of RCM development is presented towards the steady improvement in design, characterization, instrumentation and data analysis. Novel experimental approaches and measurement techniques, coordinated with computational methods are described which have expanded the utility of RCMs beyond empirical studies of explosion limits to increasingly detailed understanding of autoignition chemistry and the role of physical-chemical interactions. Fundamental insight into the autoignition chemistry of specific fuels is described, demonstrating the extent of knowledge of low-temperature chemistry derived from RCM studies, from simple hydrocarbons to multi-component blends and full-boiling range fuels. Emerging needs and further opportunities are suggested, including investigations of under-explored fuels and the implementation of increasingly higher fidelity diagnostics. [ABSTRACT FROM AUTHOR]

Recent advances in fuel research have identified many benefits associated with heating fuels before they are injected into internal combustion engines, including improved cold starting and reduced greenhouse gas emissions. Extensive research has also been carried out into alternative, renewable biofuels. Of these, ethanol, which is normally used in ethanol-gasoline blends, is one of the most promising. However, although the characteristics and uses of heated fuel have been much discussed in the literature, it is important to improve our understanding of the fuel-heating process, which frequently involves nucleate boiling. This paper describes a comprehensive, novel experimental study of nucleate boiling in pure gasoline, ethanol and gasoline-ethanol blends. The heat transfer coefficient, critical heat flux and hysteresis effect are analyzed for each test fluid, and some considerations on the pressure effect are presented. For all the gasoline-ethanol blends, the heat transfer coefficient and critical heat flux increased with increasing pressure. Addition of ethanol to gasoline did not significantly change the heat transfer coefficient until the mole fraction exceeded 35%. The behavior of the heat transfer coefficient and critical heat flux indicates the existence of an azeotrope close to an ethanol mole fraction of 20%. Finally, gasoline exhibited partial nucleation during increasing heat flux at pressures greater than 202 kPa . Addition of ethanol to pure gasoline gradually eliminated this behavior until total nucleation was achieved. [ABSTRACT FROM AUTHOR]

In this article, a finite element (FE) formulation accounting for multiphysics response of multilayered magneto-electro-elastic (MEE) plates in the thermal environment has been presented. The equilibrium equations of motion are attained using the principle of total potential energy and coupled constitutive relations of MEE material. Maxwell’s equation of electrostatics and magnetostatics are used to model the electric and magnetic behavior. The influence of various through thickness temperature distributions on the static parameters of stepped functionally graded magneto-electro-elastic ( SFG- MEE) plates is investigated. Further, an extra attention has been devoted to evaluate the effect of product properties (pyroelectric and pyromagnetic coupling), boundary conditions and aspect ratio on the direct (displacements, electric potential and magnetic potential) and derived quantities (stresses, electric displacement, and magnetic flux density) of the SFG- MEE plate. A comparative study is also carried out to analyse the effect of stacking sequence, boundary conditions, pyroeffects, length-to-width ratio and aspect ratios of the SFG- MEE plate. The credibility of the proposed FE model is verified with the results available in the literature. It is expected that the findings in this article may be useful for accurate design and analysis of MEE structures under the thermal environment. [ABSTRACT FROM AUTHOR]

Combustion phasing is the main obstacle to the development of controlled auto-ignition based (CAI) engines to achieve low emissions and low fuel consumption operation. Fuel combinations with substantial differences in reactivity, such as diesel/compressed natural gas (CNG), show desirable combustion outputs and demonstrate great possibility in controlling the combustion. This paper discusses a control method for diesel/CNG mixture combustion with a variation of fuel composition and fuel stratification levels. The experiments were carried out in a constant volume combustion chamber with both fuels directly injected into the chamber. The mixture composition was varied from 0 to 100% CNG/diesel at lambda 1 while the fuel stratification level was controlled by the injection phasing between the two fuels, with gaps between injections ranging from 0 to 20 ms. The results demonstrated the suppressing effect of CNG on the diesel combustion, especially at the early combustion stages. However, CNG significantly enhanced the combustion performance of the diesel in the later stages. Injection gaps, on the other hand, showed particular behavior depending on mixture composition. Injection gaps show less effect on combustion phasing but a significant effect on the combustion output for higher diesel percentage (≥'70%), while it is contradictive for lower diesel percentage (<70%). [ABSTRACT FROM AUTHOR]