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Статті в журналах з теми "EGR dilution"

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Автор: Grafiati

Опубліковано: 14 березня 2023

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1

Wang, Li, Zhaoming Huang, Wang Tao, Kai Shen, and Weiguo Chen. "Economy and emission characteristics of the optimal dilution strategy in lean combustion based on GDI gasoline engine equipped with prechamber." Advances in Mechanical Engineering 13, no. 12 (December 2021): 168781402110381. http://dx.doi.org/10.1177/16878140211038100.

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EGR and excess-air dilution have been investigated in a 1.5 L four cylinders gasoline direct injection (GDI) turbocharged engine equipped with prechamber. The influences of the two different dilution technologies on the engine performance are explored. The results show that at 2400 rpm and 12 bar, EGR dilution can adopt more aggressive ignition advanced angle to achieve optimal combustion phasing. However, excess-air dilution has greater fuel economy than that of EGR dilution owing to larger in-cylinder polytropic exponent. As for prechamber, when dilution ratio is greater than 37.1%, the combustion phase is advanced, resulting in fuel economy improving. Meanwhile, only when the dilution ratio is under 36.2%, the HC emissions of excess-air dilution are lower than the original engine. With the increase of dilution ratio, the CO emissions decrease continuously. The NOX emissions of both dilution technologies are 11% of those of the original engine. Excess-air dilution has better fuel economy and very low CO emissions. EGR dilution can effectively reduce NOX emissions, but increase HC emissions. Compared with spark plug ignition, the pre chamber ignition has lower HC, CO emissions, and higher NO emissions. At part load, the pre-chamber ignition reduces NOX emissions to 49 ppm.

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2

Sarangi, Asish K., Gordon P. McTaggart-Cowan, and Colin P. Garner. "The Impact of Fuel Injection Timing and Charge Dilution Rate on Low Temperature Combustion in a Compression Ignition Engine." Energies 16, no. 1 (December 23, 2022): 139. http://dx.doi.org/10.3390/en16010139.

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Using high charge dilution low temperature combustion (LTC) strategies in a diesel engine offers low emissions of nitrogen oxides (NOx). These strategies are limited to part-load conditions and involve high levels of charge dilution, typically achieved through the use of recirculated exhaust gases (EGR). The slow response of the gas handling system, compared to load demand and fuelling, can lead to conditions where dilution levels are higher or lower than expected, impacting emissions and combustion stability. This article reports on the sensitivity of high-dilution LTC to variations in EGR rate and fuel injection timing. Impacts on engine efficiency, combustion stability and emissions are assessed in a single-cylinder engine and compared to in-cylinder flame temperatures measured using a borescope-based two-colour pyrometer. The work focuses on low-load conditions (300 kPa gross indicated mean effective pressure) and includes an EGR sweep from conventional diesel mode to high-dilution LTC, and sensitivity studies investigating the effects of variations in charge dilution and fuel injection timing at the high-dilution LTC condition. Key findings from the study include that the peak flame temperature decreased from ~2580 K in conventional diesel combustion with no EGR to 1800 K in LTC with low-NOx, low-soot operation and an EGR rate of 57%. Increasing the EGR to 64% reduced flame temperatures to 1400 K but increased total hydrocarbon (THC) and carbon monoxide (CO) emissions by 30–50% and increased fuel consumption by 5–7%. Charge dilution was found to have a stronger effect on the combustion process than the diesel injection timing under these LTC conditions. Advancing fuel injection timings at increasing dilution kept combustion instability below 2.5%. Peak in-cylinder temperatures were maintained in the 2000–2100 K range, while THC and CO emissions were controlled by delaying the onset of bulk quenching. Very early injection (earlier than 24 °CA before top-dead-centre) resulted in spray impingement on the piston crown, resulting in degraded efficiency and higher emissions. The results of this study demonstrate the potential of fuel injection timing modification to accommodate variations in charge dilution rates while maintaining low NOx and PM emissions in a diesel engine using low-temperature combustion strategies at part loads.

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3

Silva, M. F., P. T. Lacava, A. Penaranda, M. E. Sbampato, and L. R. L. R. Santos. "EXPERIMENTAL STUDY WITH DIFFERENT STRATEGIES AND AIR-DILUTION USING OPTICAL SI ENGINE FUELED WITH HYDRATED ETHANOL." Revista de Engenharia Térmica 21, no. 3 (February 8, 2023): 01. http://dx.doi.org/10.5380/reterm.v21i3.89663.

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Анотація:

Several dilution conditions techniques are used in internal combustion engines to increase fuel economy and reduce pollutant emissions, primarily nitrogen oxide (NOX), which are generated by the thermal pathway. Among the techniques, we can highlight air dilution (lean combustion) and exhaust gas recirculation (EGR). The control of these operations using different types of fuels and biofuels and their peculiarities, are of fundamental importance to remove the maximum efficiency from the process, generating the lowest level of emission and respecting the current legislation. Although several studies have achieved interesting results for reducing emissions and knocks thanks to the dilution of the air, it has been observed that the diluent without oxygen is more efficient. Although air dilution has a slightly lesser effect than EGR, this mode of operation can help to understand the dynamics of engine load dilution, mainly due to the complexity of EGR tests on research engines. Therefore, as a background, tests were carried out experimentally with air dilution in order to understand the behavior for the prediction of future tests with EGR. The tests were performed with hydrated ethanol and speeds of 1500 rpm and 2500 rpm. It was possible to observe that with increasing dilution, there is a gradual increase in the variability of the burn and its displacement to the region close to the inlet valve. It was observed that the dilution provided a decrease in the formation of NOX and CO and an increase in hydrocarbon emissions. Increased rotation due to increased turbulence causes changes in emission values.

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4

Atkins, M. J., and C. R. Koch. "The effect of fuel octane and dilutent on homogeneous charge compression ignition combustion." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 219, no. 5 (May 1, 2005): 665–75. http://dx.doi.org/10.1243/095440705x11202.

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This paper presents some experimental operating and combustion properties of homogeneous charge compression ignition (HCCI) combustion. HCCI operating range, start of combustion, burn duration, indicated mean effective pressure, indicated specific emissions, and indicated specific fuel consumption are evaluated as charge dilution and octane number are varied. Primary reference fuels with octane numbers of 20, 40, and 60 are used in this study. The autoignition properties of the air-fuel mixture are varied by changing the fuel octane number, percentage of exhaust gas recirculation (EGR), and air-fuel ratio, while holding the intake temperature, engine speed, and compression ratio constant. Results show that both the start of combustion and the burn duration are sensitive to mixture dilution (excess air or EGR). The fuel octane number is not an effective method of controlling the start of combustion or the burn duration but can be used to increase the load range of the HCCI engine. Both the NO x emissions and the indicated specific fuel consumption increase as the octane number is increased due to lower dilution and higher peak temperatures. Correct amounts of dilution are critical in controlling HCCI combustion. Separating dilution into EGR and excess air, it is found that a given amount of EGR is more effective at controlling the start of combustion and the burn duration than the same amount of excess air.

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5

Pamminger, Michael, Buyu Wang, Carrie M. Hall, Ryan Vojtech, and Thomas Wallner. "The impact of water injection and exhaust gas recirculation on combustion and emissions in a heavy-duty compression ignition engine operated on diesel and gasoline." International Journal of Engine Research 21, no. 8 (January 8, 2019): 1555–73. http://dx.doi.org/10.1177/1468087418815290.

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Steady-state experiments were conducted on a 12.4L, six-cylinder heavy-duty engine to investigate the influence of port-injected water and dilution via exhaust gas recirculation (EGR) on combustion and emissions for diesel and gasoline operation. Adding a diluent to the combustion process reduces peak combustion temperatures and can reduce the reactivity of the charge, thereby increasing the ignition-delay and, allowing for more time to premix air and fuel. Experiments spanned water/fuel mass ratios up to 140mass% and exhaust gas recirculation ratios up to 20vol% for gasoline and diesel operation with different injection strategies. Diluting the combustion process with either water or EGR resulted in a significant reduction in nitrogen oxide emissions along with a reduction in brake thermal efficiency. The sensitivity of brake thermal efficiency to water and EGR varied among the fuels and injection strategies investigated. An efficiency breakdown revealed that water injection considerably reduced the wall heat transfer; however, a substantial increase in exhaust enthalpy offset the reduction in wall heat transfer and led to a reduction in brake thermal efficiency. Regular diesel operation with main and post injection exhibited a brake thermal efficiency of 45.8% and a 0.3% reduction at a water/fuel ratio of 120%. The engine operation with gasoline, early pilot, and main injection strategy showed a brake thermal efficiency of 45.0% at 0% water/fuel ratio, and a 1.2% decrease in brake thermal efficiency for a water/fuel ratio of 140%. Using EGR as a diluent reduced the brake thermal efficiency by 0.3% for diesel operation, comparing ratios of 0% and 20% EGR. However, a higher impact on brake thermal efficiency was seen for gasoline operation with early pilot and main injection strategy, with a reduction of about 0.8% comparing 0% and 20% EGR. Dilution by means of EGR exhibited a reduction in nitrogen oxide emissions up to 15 g/kWh; water injection showed only up to 10 g/kWh reduction for the EGR rates and water/fuel ratio investigated.

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6

Alger, Terrence, Raphael Gukelberger, and Jess Gingrich. "Impact of EGR Quality on the Total Inert Dilution Ratio." SAE International Journal of Engines 9, no. 2 (April 5, 2016): 796–806. http://dx.doi.org/10.4271/2016-01-0713.

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7

Zhang, Zheng, and David M. Cohen. "Hypotonicity increases transcription, expression, and action ofEgr-1in murine renal medullary mIMCD3 cells." American Journal of Physiology-Renal Physiology 273, no. 5 (November 1, 1997): F837—F842. http://dx.doi.org/10.1152/ajprenal.1997.273.5.f837.

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In cells of the murine renal inner medullary collecting duct (mIMCD3) cell line, acute hypotonic shock (50% dilution of medium with sterile water but not with sterile 150 mM NaCl) increased Egr-1 mRNA abundance 2.5-fold at 6 h, as determined by Northern analysis. This increase was accompanied by increased Egr-1 transcription, as quantitated by luciferase reporter gene assay. Increased transcription was dose dependent, additive with other Egr-1 transcriptional activators, and occurred in the absence of overt cytotoxicy, as quantitated via a fluorometric viability assay. In addition, hypotonic stress increased Egr-1 protein abundance, which was accompanied by augmented Egr-1-specific DNA binding ability, as measured via electrophoretic mobility shift assay. Increased DNA binding was further associated with increased transactivation by Egr-1, demonstrated through transient transfection of mIMCD3 cells with a luciferase reporter gene driven by tandem repeats of the Egr-1 DNA consensus sequence. Taken together, these data indicate that hypotonic stress activates Egr-1 transcription, translation, DNA binding, and transactivation in renal medullary cells. This phenomenon might play a role in the acquisition of the adaptive phenotype in response to hypotonic stress in cells of the renal medulla in vivo.

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8

Zhao, Y., Z. Wang, G. J. Xu, and M. D. Li. "Impact of EGR on the surface functional groups of diesel engine particles based on NEXAFS." RSC Advances 6, no. 62 (2016): 57363–70. http://dx.doi.org/10.1039/c6ra08165g.

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The thermal, dilution and chemical effects of EGR result in relatively significant changes in the formation environment, in the physical and chemical reactions of particles and in the functional groups of the matter that constitutes the particles.

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9

Allenby, S., W.-C. Chang, A. Megaritis, and M. L. Wyszyński. "Hydrogen enrichment: A way to maintain combustion stability in a natural gas fuelled engine with exhaust gas recirculation, the potential of fuel reforming." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 215, no. 3 (March 1, 2001): 405–18. http://dx.doi.org/10.1243/0954407011525737.

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An experimental study was carried out to evaluate the potential of hydrogen enrichment to increase the tolerance of a stoichiometrically fuelled natural gas engine to high levels of dilution by exhaust gas recirculation (EGR). This provides significant gains in terms of exhaust emissions without the rapid reduction in combustion stability typically seen when applying EGR to a methane-fuelled engine. Presented results give the envelope of benefits from hydrogen enrichment. In parallel, the performance of a catalytic exhaust gas reforming reactor was investigated in order that it could be used as an onboard source of hydrogen-rich EGR. It was shown that sufficient hydrogen was generated with currently available prototype catalysts to allow the engine, at the operating points considered, to tolerate up to 25 per cent EGR, while maintaining a coefficient of variability of indicated mean effective pressure below 5 per cent. This level of EGR gives a reduction in NO emissions greater than 80 per cent in all test cases.

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10

Yoo, Heecheong, Bum Park, Honghyun Cho, and Jungsoo Park. "Performance Optimization of a Diesel Engine with a Two-Stage Turbocharging System and Dual-Loop EGR Using Multi-Objective Pareto Optimization Based on Diesel Cycle Simulation." Energies 12, no. 22 (November 6, 2019): 4223. http://dx.doi.org/10.3390/en12224223.

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The effects of an electric supercharger (eS) and a dual-loop exhaust gas recirculation (EGR) system on a passenger car’s diesel engine’s emissions and fuel efficiency under various worldwide harmonized light-duty vehicles test procedure (WLTP) reference operation points were investigated using a one-dimensional engine cycle simulation, called GT-Power. After heavy EGR application, the in-cylinder pressure and temperature declined due to a dilution effect. As eS power and rpm increased, the brake-specific fuel consumption (BSFC) decreased because the effects of the air flow rate increased. However, it was unavoidable that nitrogen oxide (NOx) emissions also increased due to the higher in-cylinder pressure and temperature. To induce more EGR to the intake system, a dual-loop EGR system was applied with eS at different low-pressure EGR (LP-EGR) fractions (0, 0.25, 0.5, 0.75, and 1.0). Under these conditions, a design of experiment (DoE) procedure was carried out and response surface plots of the BSFC and brake-specific NOx (BSNOx) were prepared. A multi-objective Pareto optimization method was used to improve the trade-off in results between the BSFC and BSNOx. Through optimization, optimal Pareto fronts were obtained, which suggested design parameters for eS power and rpm to control the engine under various LP fraction conditions.

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11

Szybist, James P., and Derek Splitter. "Effects of Fuel Composition on EGR Dilution Tolerance in Spark Ignited Engines." SAE International Journal of Engines 9, no. 2 (April 5, 2016): 819–31. http://dx.doi.org/10.4271/2016-01-0715.

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12

Zhao, H., J. Hu, and N. Ladommatos. "In-cylinder studies of the effects of CO2 in exhaust gas recirculation on diesel combustion and emissions." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 214, no. 4 (April 1, 2000): 405–19. http://dx.doi.org/10.1243/0954407001527727.

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This paper reports the results of the effects of CO2 in exhaust gas recirculation (EGR) on diesel combustion and emissions. The experiments were carried out on a specially designed single-cylinder diesel engine. In-cylinder measurements were obtained from the optically accessible swirl chamber using high-speed shadowgraphy, the two-colour method and laser extinction. Furthermore, in-cylinder pressure measurements from the combustion chambers were used to derive the heat release rates during combustion. Two experiments were carried out on the effects of CO2 on diesel combustion and pollutant formation. In the first series of experiments, CO2 was used to replace some of the oxygen in the intake mixture, which simulated the dilution effect of conventional EGR. This so-called replacement EGR method was characterized by the typical NOx and smoke trade-off, where NOx reduction was accomplished at the expense of exhaust smoke. In the second series of tests, CO2 was added to the intake charge so that the oxygen concentration in the combustion chamber was not affected. In this additional EGR method, CO2 was found to suppress both NOx and smoke emissions. The mechanisms of these two different EGR modes on diesel combustion and emissions were examined using the above in-cylinder measurement techniques and exhaust emission analysis.

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13

Nakano, M., Y. Mandokoro, S. Kubo, and S. Yamazaki. "Effects of exhaust gas recirculation in homogeneous charge compression ignition engines." International Journal of Engine Research 1, no. 3 (June 1, 2000): 269–79. http://dx.doi.org/10.1243/1468087001545173.

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Ignition control is an important issue in homogeneous charge compression ignition (HCCI) engines, which have the advantages of low NOx emission and high thermal efficiency. In this study, the effect of the exhaust gas recirculation (EGR) on the ignition control of HCCI engines is discussed using an engine cycle simulation in which a homogeneous mixture is assumed. Auto-ignition of 65 per cent iso-octane + 25 per cent toluene + 10 per cent n-heptane, which is used as a fuel to evaluate the characteristics of a gasoline-like fuel, is represented by a detailed reaction model. The dilution by EGR delays the ignition timing when the charged gas temperature is not changed by EGR. The temperature rise of the charged gas promotes auto-ignition. Based on these characteristics, it was suggested that the ignition timing could be controlled by EGR with temperature control, when the amount of fuel supply is constant. This control method can also be applied to control of the air-fuel ratio (A/F) in the cylinder while maintaining the optimum ignition timing. In spite of the difference in the A/F and the EGR ratios, no significant difference was found in the pressure rise rate at combustion and the NOx emission when the ignition timing was the same.

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14

Ladommatos, N., S. M. Adelhalim, H. Zhao, and Z. Hu. "The effects of carbon dioxide in exhaust gas recirculation on diesel engine emissions." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 212, no. 1 (January 1, 1998): 25–42. http://dx.doi.org/10.1243/0954407981525777.

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The investigation was conducted on a high-speed direct injection diesel engine and was concerned with the effects of exhaust gas recirculation (EGR) on diesel engine combustion and emissions. In particular, the effects of carbon dioxide (CO2), a principal constituent of EGR, on combustion and emissions were analysed and quantified experimentally. The use of CO2 to displace oxygen (O2) in the inlet air resulted in: reduction in the O2 supplied to the engine (dilution effect), increased inlet charge thermal capacity (thermal effect), and, potentially, participation of the CO2 in the combustion process (chemical effect). In a separate series of tests the temperature of the engine inlet charge was raised gradually in order to simulate the effect of mixing hot EGR with engine inlet air. Finally, tests were carried out during which the CO2 added to the engine air flow increased the charge mass flowrate to the engine, rather than displacing some of the O2 in the inlet air. It was found that when CO2 displaced O2 in the inlet charge, both the chemical and thermal effects on exhaust emissions were small. However, the dilution effect was substantial, and resulted in very large reductions in exhaust oxides of nitrogen (NO x) at the expense of higher particulate and unburned hydrocarbon (uHC) emissions. Higher inlet charge temperature increased exhaust NO x and particulate emissions, but reduced uHC emissions. Finally, when CO2 was additional to the inlet air charge (rather than displacing O2), large reductions in NOx were recorded with little increase in particulate emissions.

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15

Gukelberger, Raphael, Terrence Alger, Barrett Mangold, Jeff Boehler, and Corey Eiden. "Effects of EGR Dilution and Fuels on Spark Plug Temperatures in Gasoline Engines." SAE International Journal of Engines 6, no. 1 (April 8, 2013): 447–55. http://dx.doi.org/10.4271/2013-01-1632.

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16

Zhang, Zheng, Xiao-Yan Yang, and David M. Cohen. "Hypotonicity activates transcription through ERK-dependent and -independent pathways in renal cells." American Journal of Physiology-Cell Physiology 275, no. 4 (October 1, 1998): C1104—C1112. http://dx.doi.org/10.1152/ajpcell.1998.275.4.c1104.

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Acute hypotonic shock (50% dilution of medium with sterile water, but not with isotonic NaCl) activated the extracellular signal response kinase (ERK) mitogen-activated protein (MAP) kinases in renal medullary cells, as measured by Western analysis with a phospho-ERK-specific antibody and by in vitro kinase assay of epitope-tagged ERKs immunoprecipitated from stable HA-ERK transfectants. Hypotonicity also activated the transcription factor and ERK substrate Elk-1 in a partially PD-98059-sensitive fashion, as assessed by chimeric reporter gene assay. Consistent with these data, hypotonic stress activated transcription of the immediate-early gene transcription factor Egr-1 in a partially PD-98059-sensitive fashion. Hypotonicity-inducible Egr-1 transcription was mediated in part through 5′-flanking regions containing serum response elements and in part through the minimal Egr-1 promoter. Elimination of the Ets motifs adjacent to key regulatory serum response elements in the Egr-1 promoter diminished the effect of hypotonicity but failed to abolish it. Interestingly, hypotonicity also transiently activated p38 and c-Jun NH2-terminal kinase 1, as determined by immunoblotting with anti-phospho-MAP kinase antibodies. Taken together, these data strongly suggest that hypotonicity activates immediate-early gene transcription in renal medullary cells via MAP kinase kinase-dependent and -independent mechanisms.

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17

Wu, Chao, Kang Song, Shaohua Li, and Hui Xie. "Impact of Electrically Assisted Turbocharger on the Intake Oxygen Concentration and Its Disturbance Rejection Control for a Heavy-duty Diesel Engine." Energies 12, no. 15 (August 5, 2019): 3014. http://dx.doi.org/10.3390/en12153014.

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The electrically assisted turbocharger (EAT) shows promise in simultaneously improving the boost response and reducing the fuel consumption of engines with assist. In this paper, experimental results show that 7.8% fuel economy (FE) benefit and 52.1% improvement in transient boost response can be achieved with EAT assist. EAT also drives the need for a new feedback variable for the air system control, instead of the exhaust recirculation gas (EGR) rate that is widely used in conventional turbocharged engines (nominal system). Steady-state results show that EAT assist allows wider turbine vane open and reduces pre-turbine pressure, which in turn elevates the engine volumetric efficiency hence the engine air flow rate at fixed boost pressure. Increased engine air flow rate, together with the reduced fuel amount necessary to meet the torque demand with assist, leads to the increase of the oxygen concentration in the exhaust gas (EGR gas dilution). Additionally, transient results demonstrate that the enhanced air supply from the compressor and the diluted EGR gas result in a spike in the oxygen concentration in the intake manifold (Xoim) during tip-in, even though there is no spike in the EGR rate response profile. Consequently, there is Nitrogen Oxides (NOx) emission spike, although the response of boost pressure and EGR rate is smooth (no spike is seen). Therefore, in contrast to EGR rate, Xoim is found to be a better choice for the feedback variable. Additionally, a disturbance observer-based Xoim controller is developed to attenuate the disturbances from the turbine vane position variation. Simulation results on a high-fidelity GT-SUTIE model show over 43% improvement in disturbance rejection capability in terms of recovery time, relative to the conventional proportional-integral-differential (PID) controller. This Xoim-based disturbance rejection control solution is beneficial in the practical application of the EAT system.

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18

Libkind, I. I., and A. V. Gonturev. "Calculation studies of the influence of exhaust gas recirculation on the characteristics of the natural gas-fueled diesel engine." Journal of Physics: Conference Series 2061, no. 1 (October 1, 2021): 012065. http://dx.doi.org/10.1088/1742-6596/2061/1/012065.

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Abstract When converting diesel engines to run on natural gas on the gas-diesel cycle, additional problems arise associated with the high thermal stress of the exhaust valves and valve seats at high loads and engine speeds. There is also an increase in NOx emissions due to higher combustion temperatures of natural gas. One of the ways to improve the economic and environmental performance of engines operating on a gas-diesel cycle with a lean air-fuel mixture is to optimize the combustion of the air-fuel mixture by using an exhaust gas recirculation system (EGR). The principle of operation of this system is as follows: exhaust gas entering the intake manifold and further into the combustion chamber reduces the oxygen concentration in the air-fuel mixture, which leads to a dilution effect and, accordingly, to a decrease in combustion temperature and a decrease in NOx content. In order to study the influence of EGR on the dual-fuel gas and diesel engine parameters in the AVL Boost software package, a computer model of the existing 6ChN13/15 engine was developed. A low-pressure EGR system with an exhaust gas cooler was simulated on this engine. Values of NOx emissions, brake specific fuel consumption (BSFC) and brake efficiency have been obtained at different recirculation rate by calculation method. These values allow to estimate the feasibility of using a cooled EGR in a natural gas-fueled diesel engine.

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19

Denton, Bradley, Christopher Chadwell, Raphael Gukelberger, and Terrence Alger. "Design and Implementation of a D-EGR® Mixer for Improved Dilution and Reformate Distribution." SAE International Journal of Engines 10, no. 3 (March 28, 2017): 892–97. http://dx.doi.org/10.4271/2017-01-0647.

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20

Siokos, Konstantinos, and Robert Prucka. "Transient Operation and Over-Dilution Mitigation for Low-Pressure EGR Systems in Spark-Ignition Engines." SAE International Journal of Engines 11, no. 5 (September 17, 2018): 525–38. http://dx.doi.org/10.4271/03-11-05-0035.

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21

Zaidaoui, H., T. Boushaki, A. Koched, JC Sautet, B. Sarh, and I. Gökalp. "Experimental Study of EGR Dilution and O2 Enrichment Effects on Turbulent Non-Premixed Swirling Flames." Combustion Science and Technology 193, no. 2 (June 26, 2020): 280–89. http://dx.doi.org/10.1080/00102202.2020.1786375.

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22

Abdelgader Agilah Saleh Gheidan, Mazlan Abdul Wahid, and Mohd Fairus Mohd Yasin. "Investigations on Emission Characteristics of Methane in Small Scale a Swirl Flameless Combustor: Using Preheating Air Diluted CO2 and N2 Gas at Various Temperatures." Journal of Advanced Research in Fluid Mechanics and Thermal Sciences 100, no. 2 (December 31, 2022): 113–37. http://dx.doi.org/10.37934/arfmts.100.2.113137.

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In order to reduce the damage to the environmental, it is desirable to have low emission combustion and high-efficiency system of operation. In achieving this, the multi-stages and exhaust gas recirculation (EGR) were adopted to reduce NOx formation during combustion. In this paper, a numerical study of the impact of diluted preheated oxidizer variables on NOx emissions from methane combustion was performed. This study utilizes Computational Fluid Dynamics (CFD) analysis to determine the influence of preheating fuel and air on the combustion efficiency when asymmetric vortex flameless was applied on different supply tangential air location at different oxygen concentrations. The design parameters utilized are diluted N2 and CO2, oxygen concentrations of 10%, 7% and 5%, and air temperatures that were set at 300 K, 500 K, 700 K and 900 K, respectively. The exhaust gas recirculation (EGR) was simulated using CO2 gas and N2 gas. The results show that by oxygen concentration has direct relationship with NOx emission for all equivalence ratios. Apart from that, CO2 dilution air offers better results than N2 dilution in reducing NOx emissions. In terms of preheating air, higher NOx emission was observed with the increase of air temperature. However, the effect of preheating air on the NOx emission is greater than the effect of preheating of fuel. Based on these results, numerous ports were considered important to achieve a good mix of air and fuel. The analysis outcome shows that more inlet tangential air has a significant influence on combustion temperature and NOx emission.

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23

HUNICZ, Jacek, and Michał GĘCA. "An investigation of supercharged CAI engine with internal gas recirculation and direct gasoline injection." Combustion Engines 150, no. 3 (September 1, 2012): 63–71. http://dx.doi.org/10.19206/ce-117032.

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Influence of boost pressure on combustion process and exhaust emission in controlled auto-ignition (CAI) engine was studied. The examinations were carried out using single-cylinder engine with fully variable valvetrain and gasoline direct injection. In order to achieve auto-ignition in-cylinder temperature was elevated with the use of internal gas recirculation (EGR) obtained via the negative valve overlap (NVO) technique. Fuel dilution obtained via increase of intake pressure resulted in substantial reduction of cylinder-out nitrogen oxides emission. However application of boosting resulted in excessive advance of auto-ignition timing and increase of pressure rate rise (PRR) at higher engine loads.

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24

Liu, Y. Lucy, Priyangi Malaviarachchi, and Peter Dean Emanuel. "Restoring Cell Responsiveness to GM-CSF and IL-3 by PTEN Is Via Controlling the Regulation of Egr-1 In TF-1a Cell Line." Blood 116, no. 21 (November 19, 2010): 2504. http://dx.doi.org/10.1182/blood.v116.21.2504.2504.

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Abstract Abstract 2504 Cytokine independence is a common event in leukemia. The mechanism is often linked to deregulation of Ras/PI3K, Ras/MAP, and JAK/STAT pathways. PTEN, a major negative regulator of the Ras pathway, was initially isolated as a tumor suppressor in a variety of malignancies. We recently reported that PTEN is deficient in 67% of juvenile myelomonocytic leukemia (JMML) patients. Other groups have also found alterations of PTEN, PI3K, or AKT in 47.7% of T-cell acute lymphoblastic leukemia. Mice who are rendered pten-deficient develop myeloproliferative disorders and acute myeloid and lymphoid leukemias, and the leukemia-initiating stem cell in these mouse models could be distinguished from the normal hematopoietic stem cell by a differential response to rapamycin. The transcription factor, Egr-1, has been known to be a positive regulator of PTEN expression. It plays an important role in controlling proliferation as well as mobilization of hematopoietic stem cells. It is unknown whether PTEN had a feedback loop on regulating Egr-1 expression. Since poorly differentiated progenitors are often mobilized to the peripheral blood in leukemia patients, we hypothesized that PTEN deficiency alters the feedback loop of Egr-1 in response to cytokine stimulation. In this manner, PTEN deficiency might contribute to the cytokine independence observed in many types of leukemia. In order to evaluate this hypothesis we investigated the role of PTEN in cells responding to GM-CSF stimulation in the leukemia cell line, TF-1a. TF-1a is PTEN deficient as well as cytokine independent, and displays a constitutively high expression of Egr-1. We restored PTEN expression in TF-1a cells. This was accomplished by packaging the coding sequence of wild-type PTEN in a retrovirus vector, pBMN-GFP, that carried a gene encoding green fluorescent protein (GFP). TF-1a cells were transfected with pBMN-PTEN-GFP or pBMN-GFP by spinoculation. The pure population of transfected cells was sorted by FACS, followed by limiting dilution. The transfected single colonies were expanded for further evaluation of PTEN expression and biological function. Data from these experiments showed: 1) over-expression PTEN in TF-1a down-regulated the expression of Egr-1 and restored the responsiveness of Egr-1 to GM-CSF stimulation, 2) PTEN restored the responsiveness of TF-1a to GM-CSF and IL-3, and 3) these events are CREB-independent. In conclusion, our data demonstrates that PTEN contributes to the cell responsiveness to GM-CSF and IL-3, and has a negative feedback role to regulate Egr-1 expression in TF-1a cells. In addition to Egr-1 regulating PTEN in a positive manner, our data indicates the presence of a feedback loop from PTEN back to Egr-1. This appears to be an event independent of CREB. Disclosures: No relevant conflicts of interest to declare.

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25

Zhou, Lei, Yixiong Ding, A. Qian Li, Yuntong Song, Zongkuan Liu, and Haiqiao Wei. "Experimental study of gasoline engine with EGR dilution based on reactivity controlled turbulent jet ignition (RCTJI)." Fuel 331 (January 2023): 125744. http://dx.doi.org/10.1016/j.fuel.2022.125744.

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26

Xie, Fangxi, Wei Hong, Yan Su, Miaomiao Zhang, and Beiping Jiang. "Effect of external hot EGR dilution on combustion, performance and particulate emissions of a GDI engine." Energy Conversion and Management 142 (June 2017): 69–81. http://dx.doi.org/10.1016/j.enconman.2017.03.045.

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27

Lim, Gi-Hun, Jun-Hyuk Park, Young Choi, Sun-Youp Lee, and Yong-Min Kim. "Comparison of Combustion Characteristics On the Basis of the Dilution Ratio in Diesel Engines with LPL EGR." Transactions of the Korean Society of Mechanical Engineers B 35, no. 5 (May 1, 2011): 525–31. http://dx.doi.org/10.3795/ksme-b.2011.35.5.525.

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28

Kang, Min Gyun, and Inyong Ohm. "Effect of Intake Flow Control Method on Part Load Performance in SI Engine(2) - EGR Characteristics and Comparison of Dilution Method." Transactions of the Korean Society of Automotive Engineers 22, no. 4 (May 1, 2014): 121–30. http://dx.doi.org/10.7467/ksae.2014.22.4.121.

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29

Wang, Hu, Daojian Liu, Tianyu Ma, Laihui Tong, Zunqing Zheng, and Mingfa Yao. "Thermal efficiency improvement of PODE/Gasoline dual-fuel RCCI high load operation with EGR and air dilution." Applied Thermal Engineering 159 (August 2019): 113763. http://dx.doi.org/10.1016/j.applthermaleng.2019.113763.

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30

Baratta, Mirko, Silvestru Chiriches, Prashant Goel, and Daniela Misul. "CFD modelling of natural gas combustion in IC engines under different EGR dilution and H2-doping conditions." Transportation Engineering 2 (December 2020): 100018. http://dx.doi.org/10.1016/j.treng.2020.100018.

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31

Zhao, Lifeng, and Defu Wang. "Combined Effects of Cooled EGR and Air Dilution on Butanol–Gasoline TGDI Engine Operation, Efficiency, Gaseous, and PM Emissions." ACS Omega 5, no. 12 (March 23, 2020): 6556–65. http://dx.doi.org/10.1021/acsomega.9b04279.

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32

Bresler, Matthew, William Attard, and Ronald Reese. "Investigation of Alternative Ignition System Impact on External EGR Dilution Tolerance in a Turbocharged Homogeneous Direct Injected Spark Ignited Engine." SAE International Journal of Engines 8, no. 4 (September 1, 2015): 1967–76. http://dx.doi.org/10.4271/2015-01-9043.

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33

Oh, Heechang, Dongwon Jung, Jinwook Son, Soohyung Woo, David Roth, Jerry Song, Youngmyung Kweon, and Joonsik Hwang. "Effect of Divided Exhaust Period in a High Efficiency TGDI Engine." Energies 14, no. 19 (October 4, 2021): 6343. http://dx.doi.org/10.3390/en14196343.

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The divided exhaust period (DEP) concept was applied to a high-efficiency gasoline engine and its impact on various engine performance aspects were investigated. To this end, key design parameters of DEP components were optimized through 1-D engine simulation. The designed DEP components were fabricated and experimental verification was performed through an engine dynamometer test. The developed DEP engine shows suitable performance for electrified vehicles, with a maximum thermal efficiency of 42.5% as well as a wide sweet spot area of efficiency over 40%. The improvement in thermal efficiency was mainly due to a reduction in pumping loss. Notably, the reduction in pumping loss was achieved under high exhaust gas recirculation (EGR) flow conditions, where further improvements in fuel consumption could be achieved through a synergistic combination of DEP implementation and high dilution combustion. Furthermore, a significantly improved catalyst light-off time, uncharacteristic in turbocharged engines, was confirmed through a simulated cold-start catalyst heating engine test.

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34

Bresler, Matthew, William P. Attard, and Ronald Reese. "ERRATUM: Investigation of Alternative Ignition System Impact on External EGR Dilution Tolerance in a Turbocharged Homogeneous Direct Injected Spark Ignited Engine." SAE International Journal of Engines 8, no. 5 (September 1, 2015): 2402. http://dx.doi.org/10.4271/2015-01-9043.01.

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35

Gong, Changming, Xiankai Si, and Fenghua Liu. "Comparative analysis on combustion and emissions between CO2 and EGR dilution GDI engine at half-load, stoichiometric and lean-burn conditions." Fuel 309 (February 2022): 122216. http://dx.doi.org/10.1016/j.fuel.2021.122216.

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36

Gong, Changming, Xiankai Si, and Fenghua Liu. "Comparative analysis on combustion and emissions between CO2 and EGR dilution GDI engine at half-load, stoichiometric and lean-burn conditions." Fuel 309 (February 2022): 122216. http://dx.doi.org/10.1016/j.fuel.2021.122216.

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37

Al-Qurashi, Khalid, Angela D. Lueking, and André L. Boehman. "The deconvolution of the thermal, dilution, and chemical effects of exhaust gas recirculation (EGR) on the reactivity of engine and flame soot." Combustion and Flame 158, no. 9 (September 2011): 1696–704. http://dx.doi.org/10.1016/j.combustflame.2011.02.006.

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38

Pan, Mingzhang, Weiwei Qian, Rong Huang, Xiaorong Zhou, Haozhong Huang, Xuezhi Pan, and Zhibo Ban. "Effects of EGR Dilution on Combustion and Emission Performance of a Compression Ignition Engine Fueled with Dimethyl Carbonate and 2-Ethylhexyl Nitrate Additive." Energy & Fuels 33, no. 9 (September 3, 2019): 8683–93. http://dx.doi.org/10.1021/acs.energyfuels.9b01494.

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39

Pan, Mingzhang, Rong Huang, Jinyang Liao, Tiancheng Ouyang, Zeyuan Zheng, Delin Lv, and Haozhong Huang. "Effect of EGR dilution on combustion, performance and emission characteristics of a diesel engine fueled with n-pentanol and 2-ethylhexyl nitrate additive." Energy Conversion and Management 176 (November 2018): 246–55. http://dx.doi.org/10.1016/j.enconman.2018.09.035.

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40

Wei, Wei, Xu He, Hairong Zhu, Junfa Duan, and Gaolin Qin. "Effect of Different Combustion Modes on the Performance of Hydrogen Internal Combustion Engines under Low Load." Sustainability 14, no. 10 (May 17, 2022): 6095. http://dx.doi.org/10.3390/su14106095.

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Detailed hydrogen–air chemical reaction mechanisms were coupled with the three-dimensional grids of an experimental hydrogen internal combustion engine (HICE) to establish a computational fluid dynamics (CFD) combustion model based on the CONVERGE software. The effects of different combustion modes on the combustion and emission characteristics of HICE under low load were studied. The simulation results showed that, with the increase in excess hydrogen, the equivalent combustion and excessive hydrogen combustion modes with medium-cooled exhaust gas recirculation (EGR) dilution could improve the intensity of the in-cylinder combustion of HICE, increase the peak values of pressure and temperature in the cylinder, and then improve the indicated thermal efficiency of HICE under low load. However, larger excessive hydrogen combustion could weaken the improvement in performance; therefore, the performance of HICE could be comprehensively improved by the adoption of excessive hydrogen combustion with a fuel–air ratio below 1.2 under low load. The obtained conclusions indicate the research disadvantages in the power and emission performances of HICE under low load, and they are of great significance for the performance optimization of HICE. Furthermore, a control strategy was proposed to improve the stability of HICE under low load.

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41

Li, Ruina, Zhong Wang, and Guangju Xu. "Study on Carbonyl Emissions of Diesel Engine Fueled with Biodiesel." International Journal of Chemical Engineering 2017 (2017): 1–12. http://dx.doi.org/10.1155/2017/1409495.

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Biodiesel is a kind of high-quality alternative fuel of diesel engine. In this study, biodiesel and biodiesel/diesel blend were used in a single cylinder diesel engine to study the carbonyl emissions. The result shows that carbonyl pollutants of biodiesel and biodiesel/diesel blend are mainly aldehyde and ketone compounds with 1–3 carbon atoms, and formaldehyde concentration is higher than 80% of the total carbonyl pollutants for biodiesel. The formaldehyde concentration peak is reduced with the increase of intake temperature (T), intake pressure (P), and exhaust gas recirculation (EGR) ratio and increased with the increase of compression ratio (ε). When excess air coefficient (λ) is lower than 1.7, the formaldehyde concentration is increased with the increase of excess air ratio. When λ is higher than 1.7, the formaldehyde concentration is reduced with the increase of excess air ratio. The dilution of air can reduce formaldehyde concentration in the premixed flame of diesel effectively; however, it has less effect on biodiesel. Among the fuel pretreatment measures of adding hydrogen, CO, and methane, the addition of hydrogen shows the best effect on reducing formaldehyde of biodiesel.

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42

Ricci, Federico, Roberto Martinelli, Luca Petrucci, Gabriele Discepoli, Carlo Nazareno Grimaldi, and Stefano Papi. "Streamers Variability Investigation of a Radio-Frequency Corona Discharge in an Optical Access Engine at Different Speeds and Loads." E3S Web of Conferences 312 (2021): 07021. http://dx.doi.org/10.1051/e3sconf/202131207021.

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Engine research community interest in the Radio-Frequency corona-based ignition systems is currently gaining in importance mainly due to their capability to ensure robust combustion at challenging operating conditions such as very lean mixture and/or high EGR dilution. The benefits of Corona low-temperature plasma foster the early flame development thanks to combustion precursors production and to a more energetic and volumetric discharge, resulting in a larger amount of involved mixture. The corona discharge generates ionizing waves, named streamers, whose temporal and spatial variability in orientation, length and branching can affect the combustion onset and, therefore, the engine cycle-to-cycle variability. In this work, the discharge natural luminosity of a RF corona igniter, characterized by four tips electrodes, was recorded in an optically accessible engine via high-speed camera detection. A preliminary statistical analysis of the spatial and temporal streamer variability was performed by operating in motored conditions. Four different engine speeds and two different loads were explored in order to deeply investigate the streamer behaviour at diverse engine operating conditions. A comparison between a motored and a lean operating condition is also proposed to analyse, at a specific engine speed, the mixture influence on the streamers propagation before the start of the combustion.

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43

Rausen, D. J., A. G. Stefanopoulou, J. M. Kang, J. A. Eng, and T. W. Kuo. "A Mean-Value Model for Control of Homogeneous Charge Compression Ignition (HCCI) Engines." Journal of Dynamic Systems, Measurement, and Control 127, no. 3 (August 23, 2004): 355–62. http://dx.doi.org/10.1115/1.1985439.

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A Mean Value Model (MVM) for a Homogeneous Charge Compression Ignition (HCCI) engine is presented. Using a phenomenological zero-dimensional approach with five continuous and three discrete states we first model the effects of the Exhaust Gas Recirculation (EGR) valve, the exhaust Rebreathing Lift (RBL), and the fueling rate on the state of charge in the cylinder at intake valve closing. An Arrhenius integral is then used to model the start of combustion, θsoc. A series of simple algebraic relations that captures the combustion duration and heat release is finally used to model the state of charge after the HCCI combustion and the Location of Peak Pressure (LPP). The model is parametrized and validated using steady-state test data from an experimental gasoline engine at the General Motors Corporation. The simple model captures the temperature, pressure, air-to-fuel ratio, and inert gas fraction of the exhausted mass flow. This characterization is important for the overall HCCI dynamics because the thermodynamic state (pressure, temperature) and concentration (oxygen and inert gas) of the exhausted mass flow affect the next combustion event. The high dilution level in HCCI engines increases the significance of this internal feedback that generally exists to a smaller extent in conventional spark-ignition and compression-ignition internal combustion engines.

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44

Shah, Ashish, Per Tunestal, and Bengt Johansson. "Investigation of Performance and Emission Characteristics of a Heavy Duty Natural Gas Engine Operated with Pre-Chamber Spark Plug and Dilution with Excess Air and EGR." SAE International Journal of Engines 5, no. 4 (September 24, 2012): 1790–801. http://dx.doi.org/10.4271/2012-01-1980.

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45

Hallquist, Å. M., M. Jerksjö, H. Fallgren, J. Westerlund, and Å. Sjödin. "Particle and gaseous emissions from individual diesel and CNG buses." Atmospheric Chemistry and Physics Discussions 12, no. 10 (October 22, 2012): 27737–73. http://dx.doi.org/10.5194/acpd-12-27737-2012.

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Abstract. In this study size-resolved particle and gaseous emissions from 28 individual diesel-fuelled and 7 compressed natural gas (CNG)-fuelled buses, selected from an in-use bus fleet, were characterised for real-world dilution scenarios. The method used was based on using CO2 as a tracer of exhaust gas dilution. The particles were sampled by using an extractive sampling method and analysed with high time resolution instrumentation EEPS (10 Hz) and CO2 with non-dispersive infrared gas analyser (LI-840, LI-COR Inc. 1 Hz). The gaseous constituents (CO, HC and NO) were measured by using a remote sensing device (AccuScan RSD 3000, Environmental System Products Inc.). Nitrogen oxides, NOx, were estimated from NO by using default NO2/NOx ratios from the road vehicle emission model HBEFA 3.1. The buses studied were diesel-fuelled Euro II–V and CNG-fuelled Enhanced Environmental Friendly Vehicles (EEVs) with different after-treatment, including selective catalytic reduction (SCR), exhaust gas recirculation (EGR) and with and without diesel particulate filter (DPF). The primary driving mode applied in this study was accelerating mode. However, regarding the particle emissions also a constant speed mode was analysed. The investigated CNG buses emitted on average higher number of particles but less mass compared to the diesel-fuelled buses. Emission factors for number of particles (EFPN) were EFPN, DPF = 8.0 ± 3.1 × 1014, EFPN, no DPF =2.8 ± 1.6 × 1015 and EFPN, CNG = 7.8 ± 5.7 × 1015 (kg fuel−1). In the accelerating mode size-resolved EFs showed unimodal number size distributions with peak diameters of 70–90 nm and 10 nm for diesel and CNG buses, respectively. For the constant speed mode bimodal average number size distributions were obtained for the diesel buses with peak modes of ~10 nm and ~60 nm. Emission factors for NOx expressed as NO2 equivalents for the diesel buses were on average 27 ± 7 g (kg fuel)−1 and for the CNG buses 41 ± 26 g (kg fuel)−1. An anti-relationship between EFNOx and EFPM was observed especially for buses with no DPF and there was a positive relationship between EFPM and EFCO.

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46

Hallquist, Å. M., M. Jerksjö, H. Fallgren, J. Westerlund, and Å. Sjödin. "Particle and gaseous emissions from individual diesel and CNG buses." Atmospheric Chemistry and Physics 13, no. 10 (May 27, 2013): 5337–50. http://dx.doi.org/10.5194/acp-13-5337-2013.

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Анотація:

Abstract. In this study size-resolved particle and gaseous emissions from 28 individual diesel-fuelled and 7 compressed natural gas (CNG)-fuelled buses, selected from an in-use bus fleet, were characterised for real-world dilution scenarios. The method used was based on using CO2 as a tracer of exhaust gas dilution. The particles were sampled by using an extractive sampling method and analysed with high time resolution instrumentation EEPS (10 Hz) and CO2 with a non-dispersive infrared gas analyser (LI-840, LI-COR Inc. 1 Hz). The gaseous constituents (CO, HC and NO) were measured by using a remote sensing device (AccuScan RSD 3000, Environmental System Products Inc.). Nitrogen oxides, NOx, were estimated from NO by using default NO2/NOx ratios from the road vehicle emission model HBEFA3.1. The buses studied were diesel-fuelled Euro III–V and CNG-fuelled Enhanced Environmentally Friendly Vehicles (EEVs) with different after-treatment, including selective catalytic reduction (SCR), exhaust gas recirculation (EGR) and with and without diesel particulate filter (DPF). The primary driving mode applied in this study was accelerating mode. However, regarding the particle emissions also a constant speed mode was analysed. The investigated CNG buses emitted on average a higher number of particles but less mass compared to the diesel-fuelled buses. Emission factors for number of particles (EFPN) were EFPN, DPF = 4.4 ± 3.5 × 1014, EFPN, no DPF = 2.1 ± 1.0 × 1015 and EFPN, CNG = 7.8 ± 5.7 ×1015 kg fuel−1. In the accelerating mode, size-resolved emission factors (EFs) showed unimodal number size distributions with peak diameters of 70–90 nm and 10 nm for diesel and CNG buses, respectively. For the constant speed mode, bimodal average number size distributions were obtained for the diesel buses with peak modes of ~10 nm and ~60 nm. Emission factors for NOx expressed as NO2 equivalents for the diesel buses were on average 27 ± 7 g (kg fuel)−1 and for the CNG buses 41 ± 26 g (kg fuel)−1. An anti-relationship between EFNOx and EFPM was observed especially for buses with no DPF, and there was a positive relationship between EFPM and EFCO.

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47

Cruccolini, Valentino, Carlo N. Grimaldi, Gabriele Discepoli, Federico Ricci, Luca Petrucci, and Stefano Papi. "An Optical Method to Characterize Streamer Variability and Streamer-to-Flame Transition for Radio-Frequency Corona Discharges." Applied Sciences 10, no. 7 (March 27, 2020): 2275. http://dx.doi.org/10.3390/app10072275.

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Анотація:

In recent years, radio-frequency corona ignition gained increasing interest from the engine research community because of its capability to extend the engine stable operating range in terms of lean and EGR dilution. The corona discharge generates streamers coming from a star-shaped electrode, generally consisting of four or five tips. The temporal and spatial variability of such streamers in length, orientation, and branching can be factors that affect the combustion onset and, therefore, engine cycle-to-cycle variability. Generally, the latter is reduced with respect to a conventional spark igniter at the same air–fuel ratio, but still present. In this work, analysis on the corona discharge and on the subsequent combustion onset was carried out in an optically accessible engine by means of the detection, via high-speed camera, of the natural luminosity of streamers and flames. A method to characterize spatial and temporal variability in motored conditions is firstly presented. A statistical analysis of the streamer behavior was performed, by separately analyzing the streamers generated by each tip of the star-shaped electrode. Finally, an original method aimed at determining the moment of the first flame appearance, caused by the combustion onset, is presented. The outcome of this work can be used to improve the knowledge on corona discharge, in particular on the stochastic behavior that characterizes the streamers. The presented optical analysis can also be adapted to other volumetric, single- or multi-point ignition systems.

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48

Grajetzki, Philipp, Takahiro Onda, Hisashi Nakamura, Takuya Tezuka, and Kaoru Maruta. "Investigation of the chemical and dilution effects of major EGR constituents on the reactivity of PRF by weak flames in a micro flow reactor with a controlled temperature profile." Combustion and Flame 209 (November 2019): 13–26. http://dx.doi.org/10.1016/j.combustflame.2019.06.021.

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49

Oliver, Kruger, Thorp, and Prescott. "Determination of the lowest dilution of aluminium acetate solution able to inhibit in vitro growth of organisms commonly found in chronic suppurative otitis media." Journal of Laryngology & Otology 114, no. 11 (November 2000): 830–31. http://dx.doi.org/10.1258/0022215001904365.

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Burow’s solution has been found to inhibit the in vitro growth of most commonly occurring bacteria found in the discharging ear. These organisms were inoculated onto appropriate agar plates that contained serial dilutions of aluminium acetate. Results show that the lowest dilution able to inhibit the growth of these organisms lies between a 1:80 and a 1:160 dilution of Burow’s solution.

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50

Awad, Hazem S. A. M., Khalil Abo-Amsha, Umair Ahmed, and Nilanjan Chakraborty. "Comparison of the Reactive Scalar Gradient Evolution between Homogeneous MILD Combustion and Premixed Turbulent Flames." Energies 14, no. 22 (November 16, 2021): 7677. http://dx.doi.org/10.3390/en14227677.

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Moderate or intense low-oxygen dilution (MILD) combustion is a novel combustion technique that can simultaneously improve thermal efficiency and reduce emissions. This paper focuses on the differences in statistical behaviours of the surface density function (SDF = magnitude of the reaction progress variable gradient) between conventional premixed flames and exhaust gas recirculation (EGR) type homogeneous-mixture combustion under MILD conditions using direct numerical simulations (DNS) data. The mean values of the SDF in the MILD combustion cases were found to be significantly smaller than those in the corresponding premixed flame cases. Moreover, the mean behaviour of the SDF in response to the variations of turbulence intensity were compared between MILD and premixed flame cases, and the differences are explained in terms of the strain rates induced by fluid motion and the ones arising from flame displacement speed. It was found that the effects of dilatation rate were much weaker in the MILD combustion cases than in the premixed flame cases, and the reactive scalar gradient in MILD combustion cases preferentially aligns with the most compressive principal strain-rate eigendirection. By contrast, the reactive scalar gradient preferentially aligned with the most extensive principal strain-rate eigendirection within the flame in the premixed flame cases considered here, but the extent of this alignment weakened with increasing turbulence intensity. This gave rise to a predominantly positive mean value of normal strain rate in the premixed flames, whereas the mean normal strain rate remained negative, and its magnitude increased with increasing turbulence intensity in the MILD combustion cases. The mean value of the reaction component of displacement speed assumed non-negligible values in the MILD combustion cases for a broader range of reaction progress variable, compared with the conventional premixed flames. Moreover, the mean displacement speed increased from the unburned gas side to the burned gas side in the conventional premixed flames, whereas the mean displacement speed in MILD combustion cases decreased from the unburned gas side to the middle of the flame before increasing mildly towards the burned gas side. These differences in the mean displacement speed gave rise to significant differences in the mean behaviour of the normal strain rate induced by the flame propagation and effective strain rate, which explains the differences in the SDF evolution and its response to the variation of turbulence intensity between the conventional premixed flames and MILD combustion cases. The tangential fluid-dynamic strain rate assumed positive mean values, but it was overcome by negative mean values of curvature stretch rate to yield negative mean values of stretch rate for both the premixed flames and MILD combustion cases. This behaviour is explained in terms of the curvature dependence of displacement speed. These findings suggest that the curvature dependence of displacement speed and the scalar gradient alignment with local principal strain rate eigendirections need to be addressed for modelling EGR-type homogeneous-mixture MILD combustion.

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