Abstract:The effective density and mixing state of particles emitted from a natural gas–diesel dual fuel engine are investigated. Measurements were conducted at three different fuel compositions including 100% diesel fuel (0% NG), 75% diesel–25% natural gas (25% NG) and 50% diesel–50% NG (50% NG). The particle effective density was measured using a differential mobility analyzer in series with a centrifugal particle mass analyzer. A catalytic stripper at 350 °C was employed upstream of the centrifugal particle mass ana… Show more
“…In this respect, there have been considerable improvements in engine technologies such as the utilization of renewable fuels, electrification, and development of hybrid engines. Recently, in the context of compression ignition (CI) engines, more advanced combustion strategies such as dual-fuel (DF) combustion have been proposed and used as viable solutions to provide higher efficiency and lower emissions compared to the conventional CI engines [1][2][3][4][5] . The idea of DF combustion in CI engines is to burn one (or a combination of) low reactivity fuel(s) (LRF), such as methane, with the assistance of a high reactivity fuel (HRF), such as diesel.…”
In dual-fuel compression ignition engines, a high-reactivity fuel, such as diesel, is directly injected to the engine cylinder to ignite a mixture of low-reactivity fuel and air. This study targets improving the general understanding on the dual-fuel ignition phenomenon using zero-dimensional homogeneous reactor studies and three-dimensional large eddy simulation together with finite-rate chemistry. Using the large eddy simulation framework, n-dodecane liquid spray is injected into the lean ambient methane–air mixture at [Formula: see text]. The injection conditions have a close relevance to the Engine Combustion Network Spray A setup. Here, we assess the effect of two different chemical mechanisms on ignition characteristics: a skeletal mechanism with 54 species and 269 reaction steps (Yao mechanism) and a reduced mechanism with 96 species and 993 reaction steps (Polimi mechanism). Altogether three ambient temperatures are considered: 900, 950, and 1000 K. Longer ignition delay time is observed in three-dimensional large eddy simulation spray cases compared to zero-dimensional homogeneous reactors, due to the time needed for fuel mixing in three-dimensional large eddy simulation sprays. Although ignition is advanced with the higher ambient temperature using both chemical mechanisms, the ignition process is faster with the Polimi mechanism compared to the Yao mechanism. The reasons for differences in ignition timing with the two mechanisms are discussed using the zero-dimensional and three-dimensional large eddy simulation data. Finally, heat release modes are compared in three-dimensional large eddy simulation according to low- and high-temperature chemistry in dual-fuel combustion at different ambient temperatures. It is found that Yao mechanism overpredicts the first-stage ignition compared to Polimi mechanism, which leads to the delayed second-stage ignition in Yao cases compared to Polimi cases. However, the differences in dual-fuel ignition for Polimi and Yao mechanisms are relatively smaller at higher ambient temperatures.
“…In this respect, there have been considerable improvements in engine technologies such as the utilization of renewable fuels, electrification, and development of hybrid engines. Recently, in the context of compression ignition (CI) engines, more advanced combustion strategies such as dual-fuel (DF) combustion have been proposed and used as viable solutions to provide higher efficiency and lower emissions compared to the conventional CI engines [1][2][3][4][5] . The idea of DF combustion in CI engines is to burn one (or a combination of) low reactivity fuel(s) (LRF), such as methane, with the assistance of a high reactivity fuel (HRF), such as diesel.…”
In dual-fuel compression ignition engines, a high-reactivity fuel, such as diesel, is directly injected to the engine cylinder to ignite a mixture of low-reactivity fuel and air. This study targets improving the general understanding on the dual-fuel ignition phenomenon using zero-dimensional homogeneous reactor studies and three-dimensional large eddy simulation together with finite-rate chemistry. Using the large eddy simulation framework, n-dodecane liquid spray is injected into the lean ambient methane–air mixture at [Formula: see text]. The injection conditions have a close relevance to the Engine Combustion Network Spray A setup. Here, we assess the effect of two different chemical mechanisms on ignition characteristics: a skeletal mechanism with 54 species and 269 reaction steps (Yao mechanism) and a reduced mechanism with 96 species and 993 reaction steps (Polimi mechanism). Altogether three ambient temperatures are considered: 900, 950, and 1000 K. Longer ignition delay time is observed in three-dimensional large eddy simulation spray cases compared to zero-dimensional homogeneous reactors, due to the time needed for fuel mixing in three-dimensional large eddy simulation sprays. Although ignition is advanced with the higher ambient temperature using both chemical mechanisms, the ignition process is faster with the Polimi mechanism compared to the Yao mechanism. The reasons for differences in ignition timing with the two mechanisms are discussed using the zero-dimensional and three-dimensional large eddy simulation data. Finally, heat release modes are compared in three-dimensional large eddy simulation according to low- and high-temperature chemistry in dual-fuel combustion at different ambient temperatures. It is found that Yao mechanism overpredicts the first-stage ignition compared to Polimi mechanism, which leads to the delayed second-stage ignition in Yao cases compared to Polimi cases. However, the differences in dual-fuel ignition for Polimi and Yao mechanisms are relatively smaller at higher ambient temperatures.
“…This was mainly due to reduction in FIP, which resulted in inferior fuel–air mixing and led to higher NPN. 28 The effect of inferior fuel atomization was also observed in APN. These trends showed that the variations in TPN were mainly due to APN variations.…”
Section: Resultsmentioning
confidence: 89%
“…This was mainly due to the higher in-cylinder temperature (due to diffusion combustion), which prevented the condensation of gaseous species and led to slightly smaller particulates. 28,29 In CDC mode, particle number concentration increased with increasing engine load and relatively larger particles were emitted due to the presence of higher fuel quantity. Nano-particle concentration was significant in the CDC mode, which increased the health risk potential of CDC mode compared to PCCI combustion mode.…”
In this experimental study, a production grade engine was modified to operate in two combustion modes, namely conventional diesel combustion (CDC) and premixed charge compression ignition (PCCI) combustion, depending on the engine load. For mode switching, an open electronic control unit was programmed to operate the engine in PCCI combustion mode up to medium engine loads and then automatically switching it to CDC mode at higher engine loads, by varying the fuel injection parameters and the exhaust gas recirculation rate. For performance and emission characterization in the entire load range (idling-to-full load) of the test engine, a test cycle of 300 s was used, which included CDC mode, PCCI combustion mode, and transition between these two modes. Results showed that both mineral diesel and B20 (20% biodiesel blended with mineral diesel, v/v) fueled PCCI combustion resulted in significantly lower NOx and particulate emissions compared to baseline CDC. Relatively lower exhaust gas temperature in PCCI combustion mode led to slightly inferior engine performance and higher concentration of unregulated emission species such as SO2, HCHO, and so on. B20-fueled engine resulted in relatively lower unregulated emission species and particulates compared to the mineral diesel–fueled engine in both the combustion modes. In CDC mode, contributions of accumulation mode particles were significantly higher compared to nucleation mode particles. Relatively lower emission of aromatic compounds in PCCI combustion mode compared to CDC mode was another important finding of this study; however, B20-fueled engines resulted in slightly higher emissions of aromatic compounds.
“…In order to potentially solve the problems including environmental pollution and the shortage of fossil fuels, various environmental-friendly automobile technologies have been proposed in the past few decades. In addition to the efforts on the design of combustion chamber, 1 fuel or water injection strategy 2–4 and alternative fuel, 5,6 the application of hybrid propulsion system is also one of the potential solutions to improve the overall energy fuel saving and reduce the emissions.…”
In this study, a new form of hybrid pneumatic combustion engine based on compressed air injection boosting is proposed. The hybrid pneumatic combustion engine regenerates the wasted energy during engine brake to improve the engine performance achieving better fuel economy. The mathematic model of the hybrid pneumatic combustion engine including a supercharged engine and the compressed air tank has been established. The steady-state and transient performance of the engine are analysed. Results show that the air injection boosting system can effectively improve the steady-state performance. Under the speed of 1900 r/min and 100% load, the engine torque and power can be increased from 1039 N m, 206.9 kW to 1057 N m, 210 kW by adopting air injection boosting with the injection pressure of 0.5 MPa. Effects of air injection parameters are also studied, showing that better performance can be achieved under higher air tank pressure and larger injection hole diameter. In addition, a transient analysis is completed under the speed of 1100 r/min. The result shows that when air injection boosting is used, the responding time of the engine to an instant load increase can be potentially reduced from 5.5 to 3.5 s under the injection pressure and duration of 0.5 MPa and 3 s. Meanwhile, the tank pressure has limited influence on the transient performance of the engine.
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