Advantages of Fuels with High Resistance to Auto-ignition in Late-injection, Low-temperature, Compression Ignition Combustion

Energy Conversion and Management

et al. 2015

154

ElsevierBenajes Calvo, JV.; García Martínez, A.; Monsalve Serrano, J. (2015). Effects of direct injection timing and blending ratio on RCCI combustion with different low reactivity fuels. Energy Conversion and Management. 99:193-209. doi:10.1016/j.enconman.2015.04.046. Effects of Direct injection timing and Blending Ratio on RCCI combustion with different Low Reactivity FuelsEnergy Conversion and Management, Volume 99, 2015, Pages 193-209. http://dx.doi.org/10.1016/j.enconman.2015 AbstractThis work investigates the effects of the direct injection timing and blending ratio on RCCI performance and engine-out emissions at different engine loads using four low reactivity fuels: E10-95, E10-98, E20-95 and E85 (port fuel injected) and keeping constant the same high reactivity fuel: diesel B7 (direct injected). The experiments were conducted using a heavy-duty single-cylinder research diesel engine adapted for dual-fuel operation. All the tests were carried out at 1200 rpm. To assess the blending ratio effect, the total energy delivered to the cylinder coming from the low reactivity fuel was kept constant for the different fuel blends investigated by adjusting the low reactivity fuel mass as required in each case. In addition, a detailed analysis of the air/fuel mixing process has been developed by means of a 1-D in-house developed spray model.Results suggest that notable higher diesel amount is required to achieve a stable combustion using E85. This fact leads to higher NOx levels and unacceptable ringing intensity. By contrast, EURO VI NOx and soot levels are fulfilled with E20-95, E10-98 and E10-95. Finally, the higher reactivity of E10-95 results in a significant reduction in CO and HC emissions, mainly at low load.

Section: Introductionmentioning

confidence: 78%

Effects of direct injection timing and blending ratio on RCCI combustion with different low reactivity fuels

Benajes

Molina

Energy Conversion and Management

et al. 2015

154

“…Gasoline-like fuels generally present properties of high volatility and higher resistance to autoignition compared with diesel fuel as presented by Kalghatgi in different studies [8] [9]. These fuels have been tested extensively focusing on performance [9] and emissions at high load operation [10].…”

Section: Introductionmentioning

confidence: 99%

Gasoline effects on spray characteristics, mixing and auto-ignition processes in a CI engine under Partially Premixed Combustion conditions

López

García-Oliver

Applied Thermal Engineering

et al. 2014

Recent research has shown that one of the paths to reduce pollutant emissions in diesel engines is to bring the operating conditions towards those of a gasoline engine, through homogeneous combustion and high octane fuels. Reduced soot, NOx, and fuel consumption are some of the benefits of using gasoline fuel combined with EGR in compression ignition engines in partially premixed combustion modes. Thus, a comparative study using diesel fuel and gasoline has been conducted focusing on the spray characteristics, mixing and autoignition process in these new combustion modes using a conventional diesel injection system. In this work, an experimental study has been carried out comparing the effects of penetration and cone angle under non-evaporating conditions for both fuels in a constant volume test rig. Besides, liquid length measurements and combustion process under partially premixed combustion (PPC) conditions in a single cylinder transparent engine have been done. The analysis of the results for both fuels shows no major differences on penetration and spray cone angle between them. Under vaporizing conditions, diesel spray exhibited a significantly longer liquid length than gasoline, due to the higher volatility of gasoline.In quantitative terms, liquid length was found to be 1.8 to 2.4 times longer for the diesel fuel. 1D spray model calculations confirmed the experimental results.The combustion process evaluation under PPC conditions shows differences in ignition delay and RoHR even under same thermodynamic conditions. Besides, Combustion images indicate differences in the autoignition and combustion process for diesel and gasoline fuels. Gasoline shows lower soot radiation and better combustion phasing.Differences in the mixing process evaluated with the 1D model show the mixing process is governed mainly by the fuel reactivity, the ignition delay and, to a lower extent, by the spray characteristics. The overall equivalence ratio obtained through the 1D model at the start of combustion is leaner for the gasoline case. This results agrees with a longer ignition delay for this fuel, due to lower fuel reactivity, and with the lower light intensity detected in the combustion images, where the leaner the equivalence ratio the lower the intensity.

“…The use of gasoline provides more flexibility to achieve the required extra mixing time at medium-high loads [21]. Several studies confirmed gasoline PPC as a promising method to control the heat release rate providing a reduction in NOx and soot emissions [19][22] [23]. However, the concept has demonstrated difficulties at low load conditions [24][25] using gasoline with octane number greater than 90, concluding that the use of a low reactivity fuel under PPC conditions provide some control on combustion phasing but still do not offers the possibility of cycle-to-cycle control.…”

Section: Introductionmentioning

confidence: 99%

The role of the in-cylinder gas temperature and oxygen concentration over low load reactivity controlled compression ignition combustion efficiency

Desantes

Benajes

et al. 2014

Energy

Several studies carried out with the aim of improving the RCCI concept in terms of thermal efficiency conclude that the main cause of the reduced efficiency at light loads is the reduced combustion efficiency. The present study used both a 3D computational model and engine experiments to explore the effect of the oxygen concentration and intake temperature on RCCI combustion efficiency at light load. The experiments were conducted using a single-cylinder heavy-duty research diesel engine adapted for dual fuel operation.Results suggest that it is possible to achieve an improvement of around 1.5% in the combustion efficiency with both strategies studied; the combined effect of intake temperature and in-cylinder fuel blending as well as the combined effect of oxygen concentration and incylinder fuel blending (ICFB). In addition, the direct comparison of both strategies suggests that the combustion losses trend is mainly associated to the in-cylinder equivalence ratio stratification, which is determined by the diesel to gasoline ratio in the blend since the injection timing is kept constant for all the tests. Moreover, the combined effect of the intake temperature and ICFB promotes a slight improvement in the combustion losses over the combined effect of the oxygen concentration and ICFB. KEYWORDS