Comparisons of particle size distribution from conventional and advanced compression ignition combustion strategies

Reactivity controlled compression ignition concept has been highlighted among the low temperature combustion strategies. However, this combustion strategy presents some problems related to high levels of hydrocarbon and carbon monoxide emissions at low load and high-pressure rise rate at high load. Therefore, to diminish these limitations, the dual-mode dual-fuel concept has been presented as an excellent alternative. This concept uses two fuels of different reactivity and switches from a dual-fuel fully premixed strategy (based on the reactivity controlled compression ignition concept) during low load to a diffusive nature during high load operation. However, the success of dual-mode dual-fuel concept depends to a large extent on the low reactivity/high reactivity fuel ratio and the injection settings. In this study, parametric variations of injection pressure and injection timing were experimentally performed to analyze the effect over each combustion process that encompasses the dual-mode dual-fuel concept and its consequent impact on gaseous and particles emissions, including an analysis of particle size distribution. The experimental results confirm how the use of an adequate injection strategy is indispensable to obtain low exhaust emission and a balance between the different pollutants. In the fully premixed reactivity controlled compression ignition strategy, the particles concentrations were dominated by nucleation mode; however, the increase in injection pressure and the advance of the diesel main injection timing provided a simultaneous reduction of nitrogen oxide and solid particles (accumulation mode). During the highly premixed reactivity controlled compression ignition strategy, the accumulation-mode particles increased, and their concentrations were higher when the diesel main injection timing advanced and injection pressure decreased, as well as there was a slight increase in nitrogen oxide emissions. Finally, in the dual-fuel diffusion strategy, the concentrations of accumulation-mode particles were higher and there was a considerable increase of these particles with the advance of the diesel main injection timing and the reduction of the injection pressure, while the nitrogen oxide emissions decreased.

Section: Resultsmentioning

confidence: 99%

Impact of injection settings on gaseous emissions and particle size distribution in the dual-mode dual-fuel concept

Bermúdez

Macián

Villalta

et al. 2019

“…The AFR IVC is calculated as the ratio between he usable air retained in the cylinder (excluding the air present in the IGR) and the injected fuel mass (m fuel ), as shown in Equation (8). The retained masses of fresh air (m air;ret ) and EGR (m EGR;ret ) are known variables obtained from Equations (4) and (5), since the TR is experimentally measured by the tracer gas method at each operating point.…”

Section: = (6)mentioning

confidence: 99%

“…The nucleation-mode represents the particles with sizes of less than 50 nm in diameter, although some authors define this limit as 30 nm. 7–9 The particles of the above mode are mainly constituted by condensed volatile or semi-volatile material and can nucleate to form new particles with a greater mass. 1,10 The accumulation-mode is formed for non-volatile particles between 30 nm and 1 µm and its chemical composition is of agglomerates of soot with or without volatile material absorbed on the surface.…”

Section: Introductionmentioning

confidence: 99%

Assessment of air management strategies on particulate number and size distributions from a 2-stroke compression-ignition engine operating with gasoline Partially Premixed Combustion concept

Bermúdez

Ruíz

Novella

et al. 2018

Bermúdez, V.; Ruiz, S.; Novella Rosa, R.; Soto-Izquierdo, L. (2018). Assessment of air management strategies on particulate number and size distributions from a 2-stroke compression-ignition engine operating with gasoline Partially Premixed Combustion concept. AbstractThe newly designed Partially Premixed Combustion (PPC) concept has demonstrated its potential to reduce NOx and particulate matter (PM) emissions combined with highly indicated efficiencies. However, it is highly dependent of the ignition characteristics of the fuel and the air/fuel mixture preparation. Therefore, the proper selection of an injection strategy, of the combustion chamber design and of the air management strategy are critical to ensuring successful PPC operation in the full engine map. The objective of the present investigation consists of evaluating the use of multiple air management strategies over the air/fuel effective equivalence ratio (ɸ eff ) and cylinder charge reactivity and its consequent impact on particle number (PN) emissions and particle size distribution. Tests were carried out in a newly designed 2-stroke HSDI CI engine operating with PPC concept using 95 Research Octane Number (RON) gasoline fuel. A Scanning Particle Sizer (SMPS) was used to measure the size distribution of engine-exhaust particles in the range from 6.3 to 237 nm. Three different steady-state operation modes in terms of indicated mean effective pressure (IMEP) and engine speed were investigated. The experiments showed an increase in PN emissions and a progressive shift in the particles size towards larger sizes, increasing the accumulation-mode particles and reducing the nucleation-mode particles with the decreasing of the differential pressure between intake and exhaust (ΔP) and the valve overlap (OLAP) period. Finally, the particle formation process was limited by the increase in the EGR rate.

“…This technology allows cooling the charge thus helping downsizing and compression ratio increase. While greatly improving the engine efficiency, particulates emission emerged as a new significant issue [1][2][3][4] . Therefore during the past few years worldwide emissions regulation were introduced to decrease particulates number (PN) and mass (PM) produced by spark ignited (SI) engines.…”

Section: Introductionmentioning

confidence: 99%

“…While greatly improving the engine efficiency, particulates emission emerged as a new significant issue. 1–4 Therefore, during the past few years, worldwide emissions regulation were introduced to decrease particulates number (PN) and mass (PM) produced by SI engines. Hence EURO VI in the European Union (EU) set a PM/PN limit to 4.5 mg/km and 6 × 10 11 part/km, respectively.…”

Section: Introductionmentioning

confidence: 99%

Experimental assessment of the sources of regulated and unregulated nanoparticles in gasoline direct-injection engines

Bardi

Pilla

Gautrot

2018

This work investigates nanoparticles formation process in light-duty GDI engines operated in homogeneous combustion. The analysis specifically focuses on the contribution of particles in the range of 10-23nm, which are expected to be taken into account in future emission regulations. Experiments were carried out on a single cylinder 0.4l displacement GDI optical engine. Exhaust gases were analysed by means of a commercial device (DMS500) to obtain a quantitative measurement of the particulates number and size. Optical diagnostics (broadband color imaging and liquid phase LIF) were employed to correlate the exhaust measurements to the in-cylinder physical phenomena. The main leverages to control soot particulates formation were investigated. The engine temperature was found to have a significant impact during the entire warm-up phase on the global particulates number (PN) and also on the relative contribution of the 10-23nm range to the total PN. Injection phasing has also a primary role in the formation of particulates in the small range of the spectrum when operating in mild stratified combustion mode. On the other hand, an increased in-cylinder aerodynamic (e.g. combined swirl-tumble motion) has a positive impact in reducing global particulates number but also causes an increase of the 10-23nm relative contribution. Optical diagnostics helped establishing a relationship between the detection of liquid film, the consequent pool fires and the exhaust gas measurements. The evaporation of the liquid film detected on the injector nozzle and the intake valve right after the injection appears to be decisive for the formation of nanoparticles in pool fire mode. The experimental results indicate that when pool fires were detected the PN increased drastically in the whole range of the spectrum including the 10-23nm range. Authors relate this effect to in-homogeneities in the fuel mixing field induced by the evaporation of the liquid film.