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2015-06-15 ...
  • June 15-17, 2015 (8:30 a.m. - 4:30 p.m.) - Troy, Michigan
Training / Education Classroom Seminars
Liquid fuel atomization and spray formation is the heart of the majority of stationary and mobile power generation machines that we rely on. This seminar focuses on the process of liquid atomization and spray formation and how it relates to fuel injection systems and emission of pollutants in modern engines. The seminar begins with background coverage of terminology, the purposes of liquid atomization and spray formation, and different designs of atomizers and nozzles employed in various industries. The focus is then directed to gasoline and diesel fuel injections, injector designs, and performance...
2015-06-03 ...
  • June 3-5, 2015 (8:30 a.m. - 4:30 p.m.) - Troy, Michigan
Training / Education Classroom Seminars
Fuel composition has had to change with the advent of more stringent emission regulations. Reformulated gasoline (RFG), for example, is vastly different from gasoline of even ten years ago. Tightening regulations on diesel emissions will dramatically change both diesel fuel and engine design. This three-day seminar will review the fundamentals of motor fuels, combustion and motor power generation. The primary content of the course provides a basic introduction to the technology, performance, evaluation, and specifications of current gasoline, diesel, and turbine fuels. The first day of the course...
2015-01-22
Event
Regulatory requirements, including the RFS, Tier 3 emissions standards, California’s LCFS program and CAFE standards are creating incentives to adjust gasoline formulations to enable cleaner, more efficient, and less carbon-intensive vehicles for the future. At the same time, fuel producers must contend with changing feedstocks and attempt to balance product slates in a global marketplace. The emergence of new sources, including natural gas and light, tight oil and increased use of biofuels have also impacted fuel production and the related petrochemical sector. It’s a changing world; will gasoline formulations change in the years ahead? This session will explore issues surrounding the future of gasoline formulation as fuel producers respond to global fuel utilization pressures, changing feedstock properties, regulatory guidance, and consumer expectations.
2014-11-11
Technical Paper
2014-32-0004
Yuma Ishizawa, Munehiro Matsuishi, Yasuhide Abe, Go Emori, Akira Iijima, Hideo Shoji, Kazuhito Misawa, Hiraku Kojima, Kenjiro Nakama
Abstract One issue of Homogeneous Charge Compression Ignition (HCCI) engines that should be addressed is to suppress rapid combustion in the high-load region. Supercharging the intake air so as to form a leaner mixture is one way of moderating HCCI combustion. However, the specific effect of supercharging on moderating HCCI combustion and the mechanism involved are not fully understood yet. Therefore, experiments were conducted in this study that were designed to moderate rapid combustion in a test HCCI engine by supercharging the air inducted into the cylinder. The engine was operated under high-load levels in a supercharged state in order to make clear the effect of supercharging on expanding the stable operating region in the high-load range. HCCI combustion was investigated under these conditions by making in-cylinder spectroscopic measurements and by analyzing the exhaust gas using Fourier transform infrared (FT-IR) spectroscopy. The results revealed that cool flame reactions were induced by increasing boost pressure when gasoline with a Research Octane Number of approximately 91 was used as the test fuel.
2014-11-11
Technical Paper
2014-32-0038
Silvana Di Iorio, Francesco Catapano, Paolo Sementa, Bianca Maria Vaglieco, Salvatore Florio, Elena Rebesco, Pietro Scorletti, Daniele Terna
Abstract Great efforts have been paid to improve engine efficiency as well as to reduce the pollutant emissions. The direct injection allows to improve the engine efficiency; on the other hand, the GDI combustion produces larger particle emissions. The properties of fuels play an important role both on engine performance and pollutant emissions. In particular, great attention was paid to the octane number. Oxygenated compounds allow increasing gasoline's octane number and play an important role in PM emission reduction. In this study was analyzed the effect of fuels with different RON and with ethanol and ethers content. The analysis was performed on a small GDI engine. Two operating conditions, representative of the typical EUDC cycle, were investigated. Both the engine performance and the exhaust emissions were evaluated. The gaseous emissions and particle concentration were measured at the exhaust by means of conventional instruments. Particle size distribution function was measured in the range from 5.6 nm to 560 nm by means of an Engine Exhaust Particle Sizer (EEPS).
2014-11-11
Technical Paper
2014-32-0063
Daniela Siano, Fabio Bozza, Danilo D'Agostino, Maria Antonietta Panza
Abstract In the present work, an Auto Regressive Moving Average (ARMA) model and a Discrete Wavelet Transform (DWT) are applied on vibrational signals, acquired by an accelerometer placed on the cylinder block of a Spark Ignition (SI) engine, for knock detection purposes. To the aim of tuning such procedures, the same analysis has been carried out by using the traditional MAPO (Maximum Amplitude of Pressure Oscillations) index and an Inverse Kinetic Model (IKM), both applied on the in-cylinder pressure signals. Vibrational and in-cylinder pressure signals have been collected on a four cylinder, four stroke engine, for different engine speeds, load conditions and spark advances. The results of the two vibrational based methods are compared and in depth discussed to the aim of highlighting the pros and cons of each methodology. The presented outcomes show the capability of the vibration based detection algorithms in accurately monitor the presence of knock phenomena, and to determine its intensity according to the IKM and MAPO based methods.
2014-11-01
Technical Paper
2014-01-9080
James E. Anderson, Timothy J. Wallington, Robert A. Stein, William M. Studzinski
Abstract Modification of gasoline blendstock composition in preparing ethanol-gasoline blends has a significant impact on vehicle exhaust emissions. In “splash” blending the blendstock is fixed, ethanol-gasoline blend compositions are clearly defined, and effects on emissions are relatively straightforward to interpret. In “match” blending the blendstock composition is modified for each ethanol-gasoline blend to match one or more fuel properties. The effects on emissions depend on which fuel properties are matched and what modifications are made, making trends difficult to interpret. The purpose of this paper is to illustrate that exclusive use of a match blending approach has fundamental flaws. For typical gasolines without ethanol, the distillation profile is a smooth, roughly linear relationship of temperature vs. percent fuel distilled. Hence the use of three points on the curve (T10, T50, and T90, defined as the 10%v, 50%v, and 90%v evaporated temperatures) has been sufficient to define their volatility-related behavior in engines.
2014-11-01
Technical Paper
2014-01-9079
Yongming Bao, Qing Nian Chan, Sanghoon Kook, Evatt Hawkes
Abstract The spray development of ethanol, gasoline and iso-octane has been studied in an optically accessible, spark-ignition direct-injection (SIDI) engine. The focus is on how fuel properties impact temporal and spatial evolution of sprays at realistic ambient conditions. Two optical facilities were used: (1) a constant-flow spray chamber simulating cold-start conditions and (2) a single-cylinder SIDI engine running at normal, warmed-up operating conditions. In these optical facilities, high-speed Mie-scattering imaging is performed to measure penetrations of spray plumes at various injection pressures of 4, 7, 11 and 15 MPa. The results show that the effect of fuel type on the tip penetration length of the sprays depends on the injection conditions and the level of fuel jet atomisation and droplet breakup. It is observed that at 4 MPa injection pressure, the tip penetration length of ethanol sprays is shorter than that of gasoline sprays, likely due to lower injection velocity and increased nozzle loss associated with higher density and increased viscosity of ethanol, respectively.
2014-11-01
Technical Paper
2014-01-9081
Giuseppe Genchi, Emiliano Pipitone
In the last years new and stricter pollutant emission regulations together with raised cost of conventional fuels resulted in an increased use of gaseous fuels, such as Natural Gas (NG) or Liquefied Petroleum Gas (LPG), for passenger vehicles. Bi-fuel engines represent a transition phase product, allowing to run either with gasoline or with gas, and for this reason are equipped with two separate injection systems. When operating at high loads with gasoline, however, these engines require rich mixtures and retarded combustions in order to prevent from dangerous knocking phenomena: this causes high hydrocarbon (HC) and carbon monoxide (CO) emissions together with high fuel consumption. With the aim to exploit the high knock resistance of NG maintaining the good performances of gasoline, the authors experienced, in a previous work [1], the simultaneous combustion of NG-gasoline mixtures on a series production Spark Ignition (SI) engine, obtaining, with respect to pure gasoline operation, strong reduction in pollutant emissions, noticeable efficiency increase and no significant power losses.
2014-10-13
Technical Paper
2014-01-2554
Fabio Bozza, Vincenzo De Bellis, Daniela Siano
Abstract Control of knock phenomenon is becoming more and more important in modern SI engine, due to the tendency to develop high boosted turbocharged engines (downsizing). To this aim, improved modeling and experimental techniques are required to precisely define the maximum allowable spark advance. On the experimental side, the knock limit is identified based on some indices derived by the analysis of the in-cylinder pressure traces or of the cylinder block vibrations. The threshold levels of the knock indices are usually defined following an heuristic approach. On the modeling side, in the 1D codes, the knock is usually described by simple correlation of the auto-ignition time of the unburned gas zone within the cylinders. In addition, the latter methodology commonly refers to ensemble-averaged pressure cycles and, for this reason, does not take into account the cycle-by-cycle variations. In this work, an experimental activity is carried out to characterize the effects of cyclic dispersion on knock phenomena for different engine speeds, at full load operations and referring to a spark advance of borderline knock.
2014-10-13
Technical Paper
2014-01-2573
Zhi Wang, Fang Wang, Shi-Jin Shuai
Abstract This paper studied the knock combustion process in gasoline HCCI engines. The complex chemical kinetics was implemented into the three-dimensional CFD code with LES (Large eddy simulation) to study the origin of the knock phenomena in HCCI combustion process. The model was validated using the experimental data from the cylinder pressure measurement. 3D-CFD with LES method gives detailed turbulence, species, temperature and pressure distribution during the gasoline HCCI combustion process. The simulation results indicate that HCCI engine knock originates from the random multipoint auto-ignition in the combustion chamber due to the slight inhomogeneity. It is induced by the significantly different heat release rate of high temperature oxidation (HTO) and low temperature oxidation (LTO) and their interactions. Pressure wave occurrence can be explained by the fact of significant pressure gradients in HCCI combustion field, which caused by multipoint auto-ignition in constant-volume heat release.
2014-10-13
Technical Paper
2014-01-2674
Gerardo Valentino, Stefano Iannuzzi
The use of biodiesel or oxygenated fuels from renewable sources in diesel engines is of particular interest because of the low environmental impact that can be achieved. The present paper reports results of an experimental investigation performed on a light duty diesel engine fuelled with biodiesel, gasoline and butanol mixed, at different volume fractions, with mineral diesel. The investigation was performed on a turbocharged DI four cylinder diesel engine for automotive applications equipped with a common rail injection system. Engine tests were carried out at 2500 rpm, 0.8 MPa of brake mean effective pressure selecting a single injection strategy and performing a parametric analysis on the effect of combustion phasing and oxygen concentration at intake on engine performance and exhaust emissions. The experiments demonstrated that the fuel properties have a strong impact on soot emissions. Blends composed of diesel-gasoline or diesel-butanol determined the maximum reduction in smoke emissions compared to the diesel fuel.
2014-10-13
Technical Paper
2014-01-2673
Amine Labreche, Fabrice Foucher, Christine Rousselle
Abstract In this work, the first injection of gasoline was maintained at 30 CAD Before TDC and the second one was swept between 10 CAD Before TDC to 5 CAD After TDC, in order to demonstrate the ideal positioning of the second injection. The results showed that when it was placed near TDC, low emissions, acceptable noise and acceptable efficiencies could be obtained. The effect of EGR, simulated by N2 addition, was also studied. As expected, globally the effect of the EGR rate was to delay the combustion phasing and to decrease NOx emissions. The optimal EGR dilution rate was found to be 30% with respect to the cycle-to-cycle variation criterion (< 5%). Increasing the dilution rate increased HC, CO and PM emissions, due to a considerable delay in combustion phasing caused by the reduction in the fuel reaction rate and the in-cylinder lack of oxygen when the EGR rate reached 30%. The impact of the fuel mass distribution between the two injections was also considered. This experiment showed that splitting the fuel mass equally between the injections is not the optimal solution.
2014-10-13
Technical Paper
2014-01-2682
Yong Qian, Lifeng Zhu, Zhen Huang, Xing-cai Lu
Abstract An experimental study was conducted on the combustion and emissions characteristics of duel fuel sequential combustion (DFSC) mode on a single-cylinder engine, applying port injection of n-heptane combined with in-cylinder direct injection of commercial gasoline, ethanol and n-butyl alcohol, respectively. Three-stage combustion, which consists of low- and high-temperature combustion of premixed n-heptane and high temperature combustion of directly injected gasoline-like fuels were observed. The effects of the premixed ratio and overall heating values per cycle on the combustion characteristics and emissions were investigated. The experimental results show that: with the increasing of premixed ratio and overall heating values per-cycle, the ignition timing of the directly injected fuels advances and the maximum pressure and maximum mass-averaged temperature increase. Furthermore, the CO emissions increase to a peak point and then decrease with the increase of premixed ratio and overall heating values.
2014-10-13
Technical Paper
2014-01-2690
Werner E. Holly, Thomas Lauer, Henrik Schuemie, Shinsuke Murakami
Abstract The combustion efficiency of large gas engines is limited by knocking combustion. Due to fact that the quality of the fuel gas has a high impact on the self-ignition of the mixture, it is the aim of this work to model the knocking combustion for fuel gases with different composition using detailed chemistry. A cycle-resolved knock simulation of the fast burning cycles was carried out in order to assume realistic temperatures and pressures in the unburned mixture Therefore, an empirical model that predicts the cyclic variations on the basis of turbulent and chemical time scales was derived from measured burn rates and implemented in a 1D simulation model. Based on the simulation of the fast burning engine cycles the self-ignition process of the unburned zone was calculated with a stochastic reactor model and correlated to measurements from the engines test bench. A good agreement of the knock onset could be achieved with this approach.
2014-10-13
Technical Paper
2014-01-2694
Jay Anderson, Scott Miers, Thomas Wallner, Kevin Stutenberg, Henning Lohse-Busch, Michael Duoba
Abstract Two modern light-duty passenger vehicles were selected for chassis dynamometer testing to evaluate differences in performance end efficiency resulting from CNG and gasoline combustion in a vehicle-based context. The vehicles were chosen to be as similar as possible apart from fuel type, sharing similar test weights and identical driveline configurations. Both vehicles were tested over several chassis dynamometer driving cycles, where it was found that the CNG vehicle exhibited 3-9% lower fuel economy than the gasoline-fueled subject. Performance tests were also conducted, where the CNG vehicle's lower tractive effort capability and longer acceleration times were consistent with the lower rated torque and power of its engine as compared to the gasoline model. The vehicles were also tested using quasi-steady-state chassis dynamometer techniques, wherein a series of engine operating points were studied. When the indicated thermal efficiency at each point was calculated, it was found that the CNG vehicle typically exhibited lower thermal efficiency.
2014-10-13
Technical Paper
2014-01-2695
Amrit Singh, David Anderson, Mark Hoffman, Zoran Filipi, Robert Prucka
Abstract The recent advent of highly effective drilling and extraction technologies has decreased the price of natural gas and renewed interest in its use for transportation. Of particular interest is the conversion of dedicated diesel engines to operate on dual-fuel with natural gas injected into the intake manifold. Dual-fuel systems with natural gas injected into the intake manifold replace a significant portion of diesel fuel energy with natural gas (generally 50% or more by energy content), and produce lower operating costs than diesel-only operation. Diesel-natural gas engines have a high compression ratio and a homogeneous mixture of natural gas and air in the cylinder end gases. These conditions are very favorable for knock at high loads. In the present study, knock prediction concepts that utilize a single step Arrhenius function for diesel-natural gas dual-fuel engines are evaluated. A heavy duty diesel engine with the capability of running both natural gas and diesel is operated at points where knock occurs and the cylinder pressure traces are recorded.
2014-10-13
Technical Paper
2014-01-2754
Yanfei Li, Hengjie Guo, Jian-Xin Wang, Hongming Xu
Abstract n-butanol has been recognized as a promising alternative fuel for gasoline and may potentially overcome the drawbacks of methanol and ethanol, e.g. higher energy density. In this paper, the spray characteristics of gasoline and n-butanol have been investigated using a high pressure direct injection injector. High speed imaging and Phase Doppler Particle Analyzer (PDPA) techniques were used to study the spray penetration and the droplet atomization process. The tests were carried out in a high pressure constant volume vessel over a range of injection pressure from 60 to 150 bar and ambient pressure from 1 to 5 bar. The results show that gasoline has a longer penetration length than that of n-butanol in most test conditions due to the relatively small density and viscosity of gasoline; n-butanol has larger SMD due to its higher viscosity. The increase in ambient pressure leads to the reduction in SMD by 42% for gasoline and by 37% for n-butanol. Based on the development of droplet velocity, it is found that the strong interaction between fuel jets could change the fuel distribution in the region close to the nozzle and this may be the joint effect of cavitation inside the nozzle and the vacuum near the nozzle caused by the high-speed fuel jets.
2014-10-13
Technical Paper
2014-01-2743
Luca Marchitto, Simona Merola, Cinzia Tornatore, Gerardo Valentino
Abstract Alcohols are largely used in spark-ignition (SI) engines as alternative fuels to gasoline. Particularly, the use of butanol meets growing interest due to its properties that are similar to gasoline, if compared with other alcohols. This paper aims to make a comparative analysis on the atomization process of gasoline and n-butanol fuel injected by a multi-hole injector nozzle for spark ignition engines. Phase Doppler Anemometry technique was applied to investigate the behavior of a spray emerging from a six-hole nozzle for direct injection spark ignition engine applications. Commercial gasoline and pure n-butanol were investigated. The fuels were injected at two pressures: namely at 5 and 10 MPa, in a test vessel at quiescent air conditions, ambient temperature and backpressure. Droplets diameter and velocity were estimated along the axis and on the edge direction of a jet through Phase Doppler Anemometry in order to provide useful information on the atomization process. Gasoline and n-butanol provided different results in droplets size and velocity.
2014-10-13
Technical Paper
2014-01-2616
Toby Rockstroh, Victor Burger, Andy Yates, Dylan Smit
Abstract This paper investigated the laminar flame speed behavior of a matrix of ten spark-ignition fuels and fuel components using a spherical combustion bomb. The analysis methodology relied solely on the in-bomb pressure data. For each fuel measurements were performed at five different air-fuel ratios covering a mixture range from lean to rich. Six repeat combustion pressure traces were recorded for each air-fuel ratio, with each record containing approximately 90 data points. The entire sequence was performed at two initial temperatures resulting in a database of over 5000 individual calculations of laminar flame speed per fuel. A regression technique was employed to determine the relevant flame-speed parameters. The fuel matrix included synthetic and conventional crude-derived gasoline fuels as well as a selection of blend components that could be used in the formulation of synthetic gasoline. The laminar flame speed results were interpreted against standard fuel specification analyses as well as the molecular weights, RON, MON results and detailed chemical compositional analyses obtained with two-dimensional gas chromatography.
2014-10-13
Technical Paper
2014-01-2608
Zhengyang Ling, Alexey Burluka, Ulugbek Azimov
Abstract Replacing the conventional fossil fuel totally or partially with alcohols or ethers in spark-ignition (SI) engine is a promising way to reduce pollutant emissions. A large number of studies on alcohol-containing blends in SI engines could be found in the literature. Nonetheless, investigations of ether-containing blends are by far much less numerous, especially for modern boosted engines. Blending with ether compounds might change the burning rate at high pressure, which consequently changes the anti-knock properties of these fuels and leads to a deterioration in the vehicle drivability. This work reports experiments carried out in two one-cylinder engines: one is a naturally aspirated, variable compression ratio engine, and the other is a strongly charged optical engine. Three fuels with different RON and MON numbers were tested: Iso-octane, a blend Ethyl Tert Butyl Ether (ETBE) with a primary reference fuel, and a commercial gasoline fuel containing 5% by volume of ethanol (E05).
2014-10-13
Technical Paper
2014-01-2620
Francesco Catapano, Silvana Di Iorio, Paolo Sementa, Bianca Maria Vaglieco
The growing concerns over the pollutant emissions as well as the depletion of fossil fuel led to the research of advanced combustion mode and alternative fuels for the reduction both of fuel consumption and exhaust emissions. The dual-fuel injection system can be used to improve the engine performance and reduce the fossil fuel consumption performing simultaneously a direct-injection (DI) and a port-fuel-injection (PFI) of different fuels. Ethanol is one of the most promising alternative fuels for SI engines. It offers high anti-knock quality because of the high octane number; moreover, being an oxygenated fuel is very effective in particle emissions reduction. On the other hand, it is characterized by lower energy density mainly because of the low lower heating value (LHV). The aim of the paper is the investigation of the ethanol-gasoline dual fuel combustion on engine performance and emissions. The experimental activity was carried out in a single cylinder engine for two wheel vehicles with a displacement of 250 cc.
2014-10-13
Technical Paper
2014-01-2618
Martin Pechout, Ales Dittrich, Michal Vojtisek-Lom
Abstract An ordinary, unmodified port fuel injection spark ignition automobile engine with closed-loop air-fuel ratio control and a three-way catalyst was operated on two butanol isomers, n-butanol and iso-butanol, and their blends with gasoline at steady-state operating points covering both common and potentially problematic regimes. The engine control unit was able to maintain the air-fuel ratio while running on both butanol isomers and their blends with gasoline. Only small changes in the heat release rates, small and insignificant decrease in exhaust gas temperatures, and no excessive increase in emissions were observed. Under commanded enrichment operation, the maximum torque, air-fuel ratio and exhaust emissions were comparable among nearly all fuels tested. The exhaust gas temperatures were comparable among fuels, with a moderate increase observed in some regimes during operation with high share of n-butanol in fuel. For both n-butanol and iso-butanol, startability was significantly worsened with more than 30% of alcohol by volume in the fuel.
2014-10-13
Technical Paper
2014-01-2654
Mohsen Salem Radwan, Osayed Sayed Mohamed Abu-Elyazeed, Y. A. Attai, M. E. Morsy
Abstract Jojoba bio-diesel is one of the most promising bio-fuels to replace gas oil in diesel engines. Therefore, the main object of the present work was to measure and correlate the pressure rise ignition delay of jojoba bio-diesel and its blends with gas oil behind incident shock waves in a shock tube. For this purpose, a shock tube test set up was designed and manufactured. It was fully instrumented for delay measurement with two piezo-electric pressure transducers, dual mode charge amplifier, data acquisition card and a computer with suitable LabVIEW software. The test variables included the type of fuel (percentage of Jojoba bio-diesel in the blend with gas oil), equivalence ratio, ignition temperature and ignition pressure. It was found that jojoba bio-diesel exhibited a lower ignition delay in comparison with that of gas oil. Rich or lean mixtures produce long delays, whilst the minimum delay occurred near the stoichiometric mixture. Also, it was found that the ignition delay of jojoba bio-diesel blends with gas oil reduced considerably as the ignition temperatures and pressures increased.
2014-10-13
Technical Paper
2014-01-2824
Piotr Bielaczyc, Andrzej Szczotka, Joseph Woodburn
Abstract Ethanol has a long history as an automotive fuel and is currently used in various blends and formats as a fuel for spark ignition engines in many areas of the world. The addition of ethanol to petrol has been shown to reduce certain types of emissions, but increase others. This paper presents the results of a detailed experimental program carried out under standard laboratory conditions to determine the influence of different quantities of petrol-ethanol blends (E5, E10, E25, E50 and E85) on the emission of regulated and unregulated gaseous pollutants and particulate matter. The ethanol-petrol blends were laboratory tested in two European passenger cars on a chassis dynamometer over the New European Driving Cycle, using a constant volume sampler and analyzers for quantification of both regulated and unregulated emissions. The emissions results revealed non-linear or insignificant changes in response to the addition of ethanol to the base fuel regarding certain parameters; and linear responses regarding others.
2014-10-13
Technical Paper
2014-01-2612
Yuhan Huang, Guang Hong, Ronghua Huang
Abstract The work reported in this paper contributes to understanding the effects of ethanol/gasoline ratio on mixture formation and cooling effect which are crucial in the development of EDI+GPI engine. The spray simulations were carried out using a commercial CFD code. The model was verified by comparing the numerical and experimental results of spray shapes in a constant volume chamber and cylinder pressure in an EDI+GPI research engine. The verified model was used to investigate the fuel vaporization and mixture formation of the EDI+GPI research engine. The effect of the ethanol/gasoline ratio on charge cooling has been studied. Compared with GPI only, EDI+GPI demonstrated stronger effect on charge cooling by decreased in-cylinder temperature. However, the cooling effect was limited by the low evaporation rate of the ethanol fuel due to its lower saturation vapour pressure than gasoline's in low temperature conditions. The cooling effect of EDI increased with the increase of ethanol/gasoline ratio until the ratio reached 58% (by volume).
2014-10-13
Technical Paper
2014-01-2547
Daniela Siano, Maria Antonietta Panza, Danilo D'Agostino
Abstract The easiest way to identify knock conditions during the operation of a SI engine is represented by the knowledge of the in-cylinder pressure. Traditional techniques like MAPO (Maximum Amplitude Pressure Oscillation) based method rely on the frequency domain processing of the pressure data. This technique may present uncertainties due to the correct specification of some model parameters, like the band-pass frequency range and the crank angle window of interest. In this paper two innovative techniques for knock detection, which make use of the in-cylinder pressure, are explained in detail, and the results are compared with those coming from the MAPO method. The first procedure is based on the use of statistical analysis by applying an Auto Regressive (AR) technique, while the second technique makes use of the Discrete Wavelet Transform (DWT). The data useful for the analysis have been acquired on a high compression ratio four cylinder, spark ignition engine. Results demonstrate that the analyzed methods give quite similar outcomes but they also highlight that AR and DWT techniques present an higher sensitivity for soft knock detection.
2014-10-13
Technical Paper
2014-01-2607
Karel Steurs, Christopher Blomberg, Konstantinos Boulouchos
Abstract Knock is often the main limiting factor for brake efficiency in spark ignition engines and is mostly attributed to auto-ignition of the unburned mixture in front of the flame. In order to study knock in a systematic way, spark angle sweeps with ethanol and iso-octane have been carried out on single cylinder spark ignition engine with variable intake temperatures at wide open throttle and stoichiometric premixed fuel/air mixtures. Much earlier and stronger knock can be observed for iso-octane compared to ethanol at otherwise same engine operating conditions due to the cooling effect and higher octane number of ethanol, leading to different cycle-to-cycle variation behavior. Detailed chemical kinetic mechanisms are used to compute ignition delay times at conditions relevant to the measurements and are compared to empirical correlations available in literature. The different correlations are used in a knock model approach and are tested against the measurement data. The importance of using accurate ignition delay time expressions in predicting the correct timing for the onset of knock is illustrated for both ethanol and iso-octane.
2014-10-13
Technical Paper
2014-01-2664
Akira Iijima, Naoya Ito, Takashi Shimada, Masanori Yamada, Hideo Shoji
Abstract Knocking combustion experiments were conducted in this study using a test engine that allowed the entire bore area to be visualized. The purpose was to make clear the detailed characteristics of knocking combustion that occurs accompanied by cylinder pressure oscillations when a Homogeneous Charge Compression Ignition (HCCI) engine is operated at high loads. Knocking combustion was intentionally induced by varying the main combustion period and engine speed. Under such conditions, knocking in HCCI combustion was investigated in detail on the basis of cylinder pressure analysis, high-speed photography of the combustion flame and spectroscopic measurement of flame light emissions. The results revealed that locally occurring autoignition took place rapidly at multiple locations in the cylinder when knocking combustion occurred. In that process, the unburned end gas subsequently underwent even more rapid autoignition, giving rise to cylinder pressure oscillations. In addition, when the engine speed and main combustion period were varied, it was found that the intensity of the cylinder pressure oscillations, i.e., knocking intensity PKI, correlated strongly with the maximum pressure rise rate per unit time dP/dtmax [MPa/msec].
2014-10-13
Technical Paper
2014-01-2686
Fan Zhang, Soheil Zeraati Rezaei, Hongming Xu, Shi-Jin Shuai
Abstract Combustion behaviour and emissions characteristics of different blending ratios of diesel and gasoline fuels (Dieseline) were investigated in a light-duty 4-cylinder compression-ignition (CI) engine operating on partially premixed compression ignition (PPCI) mode. Experiments show that increasing volatility and reducing cetane number of fuels can help promote PPCI and consequently reduce particulate matter (PM) emissions while oxides of nitrogen (NOx) emissions reduction depends on the engine load. Three different blends, 0% (G0), 20% (G20) and 50% (G50) of gasoline mixed with diesel by volume, were studied and results were compared to the diesel-baseline with the same combustion phasing for all experiments. Engine speed was fixed at 1800rpm, while the engine load was varied from 1.38 to 7.85 bar BMEP with the exhaust gas recirculation (EGR) application. Results show that, compared to the diesel baseline, the total particle number concentration of G50 was reduced by up to 50% and 90% and count median diameter (CMD) was reduced by 25% and 75% at medium and low loads respectively.
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