Criteria

Text:
Display:

Results

Viewing 1 to 30 of 17349
2016-05-18
Journal Article
2016-01-9043
Timo van Overbrueggen, Marco Braun, Michael Klaas, Wolfgang Schroder
Abstract The interaction of biofuel sprays from an outward opening hollow cone injector and the flow field inside an internal combustion engine is analyzed by Mie-Scattering Imaging (MSI) and high-speed stereoscopic particle-image velocimetry (stereo-PIV). Two fuels (ethanol and methyl ethyl ketone (MEK)), four injection pressures (50, 100, 150, and 200 bar), three starting points of injection (60°, 277°, and 297° atdc), and two engine speeds (1,500 rpm and 2,000 rpm) define the parameter space of the experiments. The MSI measurements determine the vertical penetration length and the spray cone angle of the ethanol and MEK spray. Stereo-PIV is used to investigate the interaction of the flow field and the ethanol spray after the injection process for a start of injection at 60° atdc. These measurements are compared to stereo-PIV measurements without fuel injection performed in the same engine [19].
2016-05-18
Technical Paper
2016-01-9074
Celeste Wilken, Stefan de Goede, Carl Viljoen
Abstract Gas to Liquids (GTL) diesel has been produced commercially for several years. GTL diesel is known for its excellent properties, including zero aromatics, near zero sulphur and a high cetane number. Most of the GTL diesel produced by commercial plants is utilised as a blend component, especially in blends up to 20%. In these applications, the cold flow properties are potentially less critical, as the cold flow properties of the blend will mostly be determined by the petroleum-derived component. In certain markets, however, it is possible that GTL diesel can be used as a neat diesel, therefore requiring good cold flow properties. An advantage of GTL technology is that the cold flow properties of GTL diesel can be tailored to meet the climatic requirements of a specific geographical area. In the current study, GTL diesel samples with cold flow properties ranging from ‘summer type’ to ‘winter type’ and varying intermediate cold flow qualities were evaluated.
2016-04-05
Technical Paper
2016-01-0297
Pulakesh Chakraborty, Ketan Kinage
The stringent regulations for emissions set by the government and the customers demand for improved fuel economy, better performance and drivability expectations is moderately increasing, creating new challenges for original equipment manufacturers. OEM’s are prompted to consider the employment of variable valve actuation mechanism in their next generation vehicles as a solution to meet the desired output. VVA is the term used to describe the method for the controlling the intake and exhaust valve timing, duration and valve lift event. The valve timings are critical events affecting the overall gas exchange process and the performance of the IC engine. Fixed parameters like target BSFC, emission norms, desired power output, desired torque output and volumetric efficiency help to select the optimum valve timings. The objective of the paper is to suggest a methodology for optimized valve timing for a high speed B hatch diesel engine.
2016-04-05
Technical Paper
2016-01-1566
Liangyao Yu, Xiaoxue Liu, Kefeng Yang, Xiaohui Liu, Shuhao Huo
This paper focuses on reviewing the existing studies of in-tire energy harvesting systems. Energy harvesting systems are widely applied in different areas. But studies in the application of energy harvesters embedded in tires for vehicle control are still rare, most of which focus on solving the problem of power supply of tire pressure sensors. Traditionally the sensors are powered by an embedded battery, which must be changed periodically due to the limited energy storage. Furthermore, the number of in-tire sensors will increase as safety of vehicles has drawn more attention, requiring more in tire electricity supply. So a substitution of the battery, the in-tire energy harvesting system, is worth studying. Currently introduced methods of in-tire energy harvesting principles include piezoelectric, electromagnetic and electrostatic. The source of the energy can be in tire vibration, deformation, rotation and so on.
2016-04-05
Technical Paper
2016-01-0295
Sentao Miao, Yan Fu, Margaret Strumolo, Boxiao Chen, Xiuli Chao, Erica Klampfl, Michael Tamor
With increasing evidence for climate change in response to greenhouse gasses (GHG) emitted by human activities, pressure is growing to reduce fuel consumption via increased vehicle efficiency and to replace fossil fuels with renewable fuels. While real-world experience with bio-ethanol, and a growing body of research on many other renewable fuel pathways, provides some guidance as to the cost of renewable transportation fuel, there has been little work comparing that cost to alternative means of achieving equivalent GHG reductions. In earlier work, we developed an optimization model that allowed the transportation and electricity generating sectors to work separately or jointly to achieve GHG reduction targets, and showed that cooperation can significantly reduce the societal cost of GHG reductions.
2016-04-05
Technical Paper
2016-01-0899
Takashi Hoshino, Farrukh Qureshi, Nicholas Virostko, Elizabeth Schiferl, Ananda Gajanayake, Motoji Hiroki, Tomoya Higuchi, Keita Ishizaki
The growing need for improved fuel economy is a global challenge due to continuously tightening environmental regulations targeting lower CO2 emission levels via reduced fuel consumption in vehicles. In order to reach these fuel efficiency targets, it necessitates improvements in hardware by applying advanced technologies in design, materials and surface treatments etc., as well as matching lubricant formulations with appropriate chemistry in. Axle lubricants have a significant impact on fuel economy. Importantly, they can be tailored to deliver maximum operation efficiency over either specific or wide ranges of operating conditions. The proper lubricant technology with well-balanced chemistries can simultaneously realize both fuel economy and hardware protection, which are commonly known to be having a trade-off relationship.
2016-04-05
Technical Paper
2016-01-1051
Jeremy Walker, Josh Lierer, Riccardo Calza, Sundar Rajan Krishnan, Kalyan Srinivasan, Hossein Toghiani
This paper presents results from a GT-POWER engine model of a Weber 850 cc, two-cylinder spark ignition engine operating on E-85 and gasoline. The simulations utilizes a two-zone combustion model with the Woschni cylinder heat transfer model. Simulation results are compared to baseline experimental data of a naturally aspirated (NA) version of the two-cylinder Weber multipurpose engine (MPE). The turbocharged (TC) engine version was obtained from the manufacturer for the EcoCAR 3 advanced vehicular technology competition (AVTC). Experimental data and simulation results are used to develop and optimize a semi-predictive combustion model. Additionally, brake thermal efficiency data generated is being used to create a simplified, fast running model implemented in real time within the Mississippi State University (MSU) EcoCAR 3 team’s systems-level vehicle model for the turbocharged (TC) version of the MPE 850 engine operating on E-85.
2016-04-05
Technical Paper
2016-01-0875
Ludvig Adlercreutz, Andreas Cronhjort, Johannes Andersen, Roy Ogink
Abstract With alternative fuels having moved more into market in light of their reduction of emissions of CO2 and other air pollutants, the spark ignited internal combustion engine design has only been affected to small extent. The development of combustion engines running on natural gas or Biogas have been focused to maintain driveability on gasoline, creating a multi fuel platform which does not fully utilise the alternative fuels’ potential. However, optimising these concepts on a fundamental level for gas operation shows a great potential to increase the level of utilisation and effectiveness of the engine and thereby meeting the emissions legislation. The project described in this paper has focused on optimising a combustion concept for CNG combustion on a single cylinder research engine. The ICE’s efficiency at full load and the fuels characteristics, including its knock resistance, is of primary interest - together with part load performance and overall fuel consumption.
2016-04-05
Journal Article
2016-01-0885
Earl Christensen, Robert L. McCormick, Jenny Sigelko, Stuart Johnson, Stefan Zickmann, Shailesh Lopes, Roger Gault, David Slade
Abstract Adoption of high-pressure common-rail (HPCR) fuel systems, which subject diesel fuels to higher temperatures and pressures, has brought into question the veracity of ASTM International specifications for biodiesel and biodiesel blend oxidation stability, as well as the lack of any stability parameter for diesel fuel. A controlled experiment was developed to investigate the impact of a light-duty diesel HPCR fuel system on the stability of 20% biodiesel (B20) blends under conditions of intermittent use and long-term storage in a relatively hot and dry climate. B20 samples with Rancimat induction periods (IPs) near the current 6.0-hour minimum specification (6.5 hr) and roughly double the ASTM specification (13.5 hr) were prepared from a conventional diesel and a highly unsaturated biodiesel. Four 2011 model year Volkswagen Passats equipped with HPCR fuel injection systems were utilized: one on B0, two on B20-6.5 hr, and one on B20-13.5 hr.
2016-04-05
Technical Paper
2016-01-0869
Jai Gopal Gupta, Avinash Kumar Agarwal
Abstract Fuel injection pressure (FIP) is one of the most important factors affecting diesel engine performance and particulate emissions. Higher FIP improves the fuel atomization, which results in lower soot formation due to superior fuel-air mixing. The objective of this spray study was to investigate macroscopic and microscopic spray parameters in FIP range of 500-1500 bar, using a solenoid injector for biodiesel blends (KB20 and KB40) and baseline mineral diesel. For these test fuels, effect of ambient pressure on macroscopic spray characteristics such as spray penetration, spray area and cone angle were investigated in a constant volume spray chamber (CVSC). Microscopic spray characteristics such as velocity distribution of droplets and spray droplet size distribution were measured in the CVSC at atmospheric pressure using Phase Doppler Interferometry (PDI).
2016-04-05
Technical Paper
2016-01-0868
Nikhil Sharma, Avinash Kumar Agarwal
Abstract The development of advanced gasoline direct injection (GDI) injector requires in-depth investigations of macroscopic and microscopic spray characteristics. Over the years, GDI injectors have undergone exponential improvement to be able to deliver fuel at high injection pressure. High fuel injection pressure (FIP) leads to superior fuel atomization, and consequently superior fuel-air mixing. Present investigations aim to improve our fundamental knowledge of the furl-air mixture preparation mechanisms of different test fuels. Experiments were conducted to study spray breakup of GDI injector. This study focuses on the spray investigations using Phase Doppler Interferometry (PDI) for the measurement of various spray related studies such as determination of arithmetic mean diameter (AMD), sauter mean diameter (SMD) and spray droplet velocity distributions.
2016-04-05
Technical Paper
2016-01-0883
Walter Mirabella, Francesco Avella, Marco Di Girolamo, Tim Abbott, Oliver Busch
Abstract A thorough bibliographic survey was carried out to collect literature-available information about blending octane numbers (BONs) of most widely used ethers by the refining industry (mainly MTBE and ETBE). The intention was to review the publicly reported BONs values, to suggest the most appropriate figures for future reference, while also understanding the causes of the differences. Summary tables feature all BON values, either explicitly reported in literature or calculated based on experimental results. Due to synergistic intermolecular interactions with hydrocarbons, BONs typically depend on base stock composition. The octane gain tends to grow as the paraffin content in the base stock increases. Moreover BONs tend to decrease as the octane numbers (ON) of the base stock increase.
2016-04-05
Technical Paper
2016-01-0884
Timothy H. Lee, Yilu Lin, Xiangyu Meng, Yuqiang Li, Karthik Nithyanandan
Abstract Acetone-Butanol-Ethanol (ABE) is an intermediate product in the ABE fermentation process for producing bio-butanol. As an additive for diesel, it has been shown to improve spray evaporation, improve fuel atomization, enhance air-fuel mixing, and enhance combustion as a whole. The typical compositions of ABE are in a volumetric ratio of 3:6:1 or 6:3:1. From previous studies done in a constant volume chamber, it was observed that the presence of additional acetone in the blend caused advancement in the combustion phasing, but too much acetone content led to an increase in soot emission during combustion. The objective of this research was to investigate the combustion of these mixtures in a diesel engine. The experiments were conducted in an AVL 5402 single-cylinder diesel engine at different speeds and different loads to study component effects on the various engine conditions.
2016-04-05
Technical Paper
2016-01-0880
Carlos Alberto Romero, Ricardo Acosta, Juan Lopez
Abstract It is the aim of the present paper to communicate some preliminary results of the research in progress related to the introduction of LPG as a supplementing fuel for the Colombian power grid supply. Most of the power units operating in Colombian oil wells are running on Diesel fuel and natural gas. Other fuels like LPG, heavy and dual fuel have received attention in recent years, due partially to the necessity to relieve the national overall petroleum dependency problem, and also because of the availability of a sizable amount of LPG derived from natural gas purification. In an effort to assess the use of LPG as a fuel alternative to Diesel and natural gas in oil wells, a field study has been carried out.
2016-04-05
Technical Paper
2016-01-0882
Martin Tuner
Abstract Alternative fuels have been proposed as a means for future energy-secure and environmentally sustainable transportation. This review and benchmarking show that several of the alternative fuels (e.g. methanol, ethanol, higher alcohols, RME, HVO, DME, and biogas/CNG) work well with several different engine concepts such as conventional SI, DICI, and dual fuel, and with the emerging concepts HCCI, RCCI, and PPC. Energy consumption is in most cases similar to that of diesel or gasoline, with the exception of methanol and ethanol that use less energy, especially in SI engines. Tailpipe emissions of CO2 with respect to engine work output (tank-to-output shaft) can be reduced by more than 15% compared to a highly efficient gasoline SI engine, and are the lowest with CNG / lean-burn SI and with alcohols in several engine concepts. Alternative fuels are considered safe and in most cases are associated with reduced risk with respect to cancer and other health and environmental issues.
2016-04-05
Journal Article
2016-01-0879
Toby Rockstroh, Gareth Floweday, Celeste Wilken
Abstract The benefits of blending ethanol into gasoline fuel are well established. Ethanol’s high latent heat of vaporisation and chemical auto-ignition resistance combine in producing significant knock resistance, enabling higher compression ratio and/or higher charge boosting. Its high flame speed characteristics result in shorter burn durations. Its high knock resistance and rapid burning enable ignition phasing optimisation. These factors all improve the efficiency of spark ignition (SI) engines. Current “flex-fuel” vehicles are designed to operate on both conventional gasoline as well as blends containing higher volumes of ethanol and/or methanol, the former being commonly known as E85. The American Society for Testing and Materials ASTM D5798 specification for ethanol fuel blends was adapted in 2011 to prescribe a minimum ethanol content of 51 % with the remainder able to consist of low octane blending streams.
2016-04-05
Technical Paper
2016-01-0878
Ahmed Elwardany, Jihad Badra, Jaeheon Sim, Muneeb Khurshid, Mani Sarathy, Hong Im
Abstract The US Department of Energy has formulated different gasoline fuels called ''Fuels for Advanced Combustion Engines (FACE)'' to standardize their compositions. FACE I is a low octane number gasoline fuel with research octane number (RON) of approximately 70. The detailed hydrocarbon analysis (DHA) of FACE I shows that it contains 33 components. This large number of components cannot be handled in fuel spray simulation where thousands of droplets are directly injected in combustion chamber. These droplets are to be heated, broken-up, collided and evaporated simultaneously. Heating and evaporation of single droplet FACE I fuel was investigated. The heating and evaporation model accounts for the effects of finite thermal conductivity, finite liquid diffusivity and recirculation inside the droplet, referred to as the effective thermal conductivity/effective diffusivity (ETC/ED) model.
2016-04-05
Technical Paper
2016-01-0877
Preetham Churkunti, Jonathan M. S. Mattson, Christopher Depcik
Abstract Biodiesel is a potential alternative to Ultra Low Sulfur Diesel (ULSD); however, it often suffers from increased fuel consumption in comparison to ULSD when injection timings and/or pressures are similar. To decrease fuel consumption, increasing biodiesel injection pressure has been found to mitigate the issues associated with its relatively high viscosity and lower energy content. When doing so, the literature indicates decreased emissions, albeit with potentially greater nitrogen oxide (NOx) emissions in contrast to ULSD. In order to better understand the trade-off between fuel consumption and NOx emissions, this study explores the influence of fuel injection pressure on ULSD, Waste Cooking Oil (WCO) biodiesel, and their blends in a single-cylinder compression ignition (CI) engine. In particular, fuel injection pressures and timings for WCO biodiesel and blended fuels are adjusted to attempt to mimic the in-cylinder pressure profile of operation using ULSD.
2016-04-05
Journal Article
2016-01-0876
George Karavalakis, Yu Jiang, Jiacheng Yang, Thomas Durbin, Jukka Nuottimäki, Kalle Lehto
Abstract Gaseous and particulate matter (PM) emissions were assessed from two current technology heavy-duty vehicles operated on CARB ultra-low sulfur diesel (ULSD), hydrotreated vegetable oil (HVO) blends, and a biodiesel blend. Testing was performed on a 2014 model year Cummins ISX15 vehicle and on a 2010 model year Cummins ISB6.7 vehicle. Both vehicles were equipped with diesel oxidation catalysts (DOC), diesel particulate filter (DPF), and selective catalytic reduction (SCR) systems. Testing was conducted over the Heavy-Duty Urban Dynamometer Driving Schedule (UDDS) and Heavy Heavy-Duty Diesel Truck (HHDDT) Transient Cycle. The results showed lower total hydrocarbons (THC), non-methane hydrocarbons (NMHC), and methane (CH4) emissions for the HVO fuels and the biodiesel blend compared to CARB ULSD. Overall, nitrogen oxide (NOx) emissions showed discordant results, with both increases and decreases for the HVO fuels.
2016-04-05
Technical Paper
2016-01-0855
Xiucheng Zhu, Sanjeet Limbu, Khanh Cung, William De Ojeda, Seong-Young Lee
Abstract Dimethyl Ether (DME) is considered a clean alternative fuel to diesel due to its soot-free combustion characteristics and its capability to be produced from renewable energy sources rather than fossil fuels such as coal or petroleum. To mitigate the effect of strong wave dynamics on fuel supply lines caused due to the high compressibility of DME and to overcome its low lubricity, a hydraulically actuated electronic unit injector (HEUI) with pressure intensification was used. The study focuses on high pressure operation, up to 2000 bar, significantly higher than pressure ranges reported previously with DME. A one-dimensional HEUI injector model is built in MATLAB/SIMULINK graphical software environment, to predict the rate of injection (ROI) profile critical to spray and combustion characterization.
2016-04-05
Technical Paper
2016-01-0852
Nwabueze Emekwuru
Abstract The results of the numerical characterization of the hydrodynamics of Soybean Oil Methyl Ester (SME) fuel spray using a spray model based on the moments of the droplet size distribution function are presented. A heat and mass transfer model based on the droplet surface-areaaveraged temperature is implemented in the spray model and the effects on the SME fuel spray tip penetration and droplet sizes at different ambient gas temperature (300 K to 450 K) and fuel temperature (300 K to 360 K) values are evaluated. The results indicate that the SME fuel spray tip penetration values are insensitive to variations to the fuel temperature values but increase with increasing ambient gas temperature values. The droplet size values increase with increasing SME fuel temperature. The fuel vapor mass fraction is predicted to be highest at the spray core, with the axial velocity values of the droplets increasing with increases in the SME fuel spray temperature.
2016-04-05
Technical Paper
2016-01-0690
Yanzhao An, Shengping Teng, Xiang Li, Jing Qin, Hua Zhao, Zhang Song Zhan, Tie Gang Hu, Bin Liu, Jing Zhong
Abstract In the present study, we developed a reduced TRF-PAH chemical reaction mechanism consisted of iso-octane, n-heptane and toluene as gasoline surrogate fuels for GDI (gasoline direct injection) spark ignition engine combustion simulation. The reduced mechanism consists of 85 species and 232 reactions including 17 species and 40 reactions related to the PAHs (polycyclic aromatic hydrocarbons) formation. The present mechanism was validated for extensive validations with experimental ignition delay times in shock tubes and laminar flame speeds in flat flame adiabatic burner for gasoline/air and TRF/air mixtures under various pressures, temperatures and equivalence ratios related to engine conditions. Good agreement was achieved for most of the measurement. Mole fraction profiles of PAHs for n-heptane flame were also simulated and the experimental trends were reproduced well.
2016-04-05
Journal Article
2016-01-0689
Magnus Sjöberg, Wei Zeng
Abstract Well-mixed lean or dilute SI engine operation can provide efficiency improvements relative to that of traditional well-mixed stoichiometric SI operation. However, the realized gains depend on the ability to ensure stable, complete and fast combustion. In this work, the influence of fuel type is examined for gasoline, E30 and E85. Several enabling techniques are compared. For enhanced ignition stability, a multi-pulse (MP) transient plasma ignition system is compared to a conventional high-energy inductive spark ignition system. Combined effects of fuel type and intake-gas preheating are examined. Also, the effects of dilution type (air or N2-simulated EGR) on lean efficiency gains and stability limits are clarified. The largest efficiency improvement is found for lean gasoline operation using intake preheating, showing the equivalent of a 20% fuel-economy gain relative to traditional non-dilute stoichiometric operation.
2016-04-05
Technical Paper
2016-01-0699
Jacob McKenzie, Wai K. Cheng
Abstract An ignition delay correlation encompassing the effects of temperature, pressure, residual gas, EGR, and lambda (on both the rich and lean sides) has been developed. The procedure uses the individual knocking cycle data from a boosted direct injection SI engine (GM LNF) operating at 1250 to 2000 rpm, 8-14 bar GIMEP, EGR of 0 to 12.5%, and lambda of 0.8 to 1.3 with a certification fuel (Haltermann 437, with RON=96.6 and MON=88.5). An algorithm has been devised to identify the knock point on individual pressure traces so that the large data set (of some thirty three thousand cycles) could be processed automatically. For lean and for rich operations, the role of the excess fuel, air, and recycled gas (which has excess air in the lean case, and hydrogen and carbon monoxide in the rich case) may be treated effectively as diluents in the ignition delay expression.
2016-04-05
Technical Paper
2016-01-0702
Gautam Kalghatgi, Kai Morganti, Ibrahim Algunaibet, Mani Sarathy, Robert Dibble
An earlier paper has shown the ability to predict the phasing of knock onset in a gasoline PFI engine using a simple ignition delay equation for an appropriate surrogate fuel made up of toluene and PRF (TPRF). The applicability of this approach is confirmed in this paper in a different engine using five different fuels of differing RON, sensitivity, and composition - including ethanol blends. An Arrhenius type equation with a pressure correction for ignition delay can be found from interpolation of previously published data for any gasoline if its RON and sensitivity are known. Then, if the pressure and temperature in the unburned gas can be estimated or measured, the Livengood-Wu integral can be estimated as a function of crank angle to predict the occurrence of knock. Experiments in a single cylinder DISI engine over a wide operating range confirm that this simple approach can predict knock very accurately.
2016-04-05
Journal Article
2016-01-0703
Yoshihiro Imaoka, Kiyotaka Shouji, Takao Inoue, Toru Noda
Abstract Technologies for improving the fuel economy of gasoline engines have been vigorously developed in recent years for the purpose of reducing CO2 emissions. Increasing the compression ratio is an example of a technology for improving the thermal efficiency of gasoline engines. A significant issue of a high compression ratio engine for improving fuel economy and low-end torque is prevention of knocking under a low engine speed. Knocking is caused by autoignition of the air-fuel mixture in the cylinder and seems to be largely affected by heat transfer from the intake port and combustion chamber walls. In this study, the influence of heat transfer from the walls of each part was analyzed by the following three approaches using computational fluid dynamics (CFD) and experiments conducted with a multi-cooling engine system. First, the temperature rise of the air-fuel mixture by heat transfer from each part was analyzed.
2016-04-05
Technical Paper
2016-01-0700
Johannes Mutzke, Blane Scott, Richard Stone, John Williams
Abstract Knocking combustion places a major limit on the performance and efficiency of spark ignition engines. Spontaneous ignition of the unburned air-fuel mixture ahead of the flame front leads to a rapid release of energy, which produces pressure waves that cause the engine structure to vibrate at its natural frequencies and produce an audible ‘pinging’ sound. In extreme cases of knock, increased temperatures and pressures in the cylinder can cause severe engine damage. Damage is thought to be caused by thermal strain effects that are directly related to the heat flux. Since it will be the maximum values that are potentially the most damaging, then the heat flux needs to be measured on a cycle-by-cycle basis. Previous work has correlated heat flux with the pressure fluctuations on an average basis, but the work here shows a correlation on a cycle-by-cycle basis. The in-cylinder pressure and surface temperature were measured using a pressure transducer and eroding-type thermocouple.
2016-04-05
Technical Paper
2016-01-0701
Katsuya Matsuura, Keito Nakano, Keisuke Shimizu, Norimasa Iida, Yoshihisa Sato
Abstract Knock is a factor hindering enhancement of the thermal efficiency of spark ignition engines, and is an unsteady phenomenon that does not necessarily occur each cycle. In addition, the heat release history of the flame also fluctuates from cycle to cycle, and the auto-ignition process of the unburned mixture (end-gas), compressed by the global increase in pressure due to release of chemical energy, is affected by this fluctuation. Regarding auto-ignition of the end-gas, which can be the origin of knock, this study focused on the fluctuation of the flame heat release pattern, and used a zero-dimensional (0D) detailed chemical reaction calculation in an attempt to analyze and examine the consequence on the end-gas compression and auto-ignition process of changes in the i) start of combustion, ii) combustion duration and iii) center of heat release of the flame.
2016-04-05
Technical Paper
2016-01-0704
Jacob McKenzie, Wai K. Cheng
Abstract The combustion process after auto-ignition is investigated. Depending on the non-uniformity of the end gas, auto-ignition could initiate a flame, produce pressure waves that excite the engine structure (acoustic knock), or result in detonation (normal or developing). For the “acoustic knock” mode, a knock intensity (KI) is defined as the pressure oscillation amplitude. The KI values over different cycles under a fixed operating condition are observed to have a log-normal distribution. When the operating condition is changed (over different values of λ, EGR, and spark timing), the mean (μ) of log (KI/GIMEP) decreases linearly with the correlation-based ignition delay calculated using the knock-point end gas condition of the mean cycle. The standard deviation σ of log(KI/GIMEP) is approximately a constant, at 0.63. The values of μ and σ thus allow a statistical description of knock from the deterministic calculation of the ignition delay using the mean cycle properties
2016-04-05
Technical Paper
2016-01-0709
Michael Bunce, Hugh Blaxill
Abstract Increasingly stringent global fuel economy and carbon dioxide (CO2) legislation for light duty passenger cars has created an interest in unconventional operating modes. One such mode in spark ignition (SI) gasoline engines is lean combustion. While lean operation in SI engines has previously demonstrated the ability to reduce fuel consumption, the degree of enleanment capability of the system is limited by increasingly unstable combustion in the lean region, particularly for homogeneous lean approaches. MAHLE Jet Ignition® (MJI) is a pre-chamber-based combustion system that extends this lean limit beyond the capabilities of modern SI engines by increasing the ignition energy present in the system. This allows the engine to exploit the benefits of homogeneous ultra-lean (λ > ∼1.6) combustion, namely reduced fuel consumption and reduced emissions of nitrogen oxides (NOx). Pre-chamber combustors such as that utilized in MJI have been studied extensively for decades.
Viewing 1 to 30 of 17349