An Investigation On The Effect Of Fuel Sensitivity On Partially Premixed Combustion With Gasoline-like Fuels

Partially premixed combustion(PPC)of gasoline-like fuels has great potential in achieving high efficient and clean combustion,and has become a hot topic in recent years.Fuel characteristics have a great important impact on engine combustion and emission characteristics,especially for fuel octane numbers.However,with the innovation of modern engine technology,RON and MON are obviously no longer applicable to evaluate the anti-knock performance of modern engine.Fuel sensitivity becomes a new and popular research direction to evaluate the anti-knock performance of modern engine.In this paper,the effects of different fuel sensitivity under different RON on combustion and emission of partially premixed combustion are systematically studied.In this paper,the experiment was carried out on a single cylinder test engine.Toluene reference fuel is used in the test,and two groups of fuel are set according to different RON.In the first group the RON of the fuel is 92,including the different fuel sensitivity 0,2,5,8 and 11 respectively.The 92# gasoline was added for comparison.The another group,the fuel RON is 70,including the different fuel sensitivity of 0,2,5 and 8,respectively.For the RON92 fuel group,the experiments were carried out respectively under two loads and to compared.And then the compare between the two group under the higher load has been carried out.The experimental results show that the more toluene the fuel contains,the larger the fuel sensitivity is,the worse the spontaneous ignition is,the longer the ignition delay is,the sufficient fuel and gas mixing,the higher the premixed combustion ratio and the higher the maximum pressure rise rate.Under the high loads,fuel sensitivity has a little effect on maximum pressure rise rate.In the RON92 fuel group,as for the fuel with low fuel sensitivity,indicate thermal efficiency is higher when the EGR rate is low under high load.As for the fuel with larger sensitivity,the indicate thermal efficiency is higher When the EGR rate is higher.But the results of RON70 fuel group are different.The fuel with low fuel sensitivity get the high indicates thermal efficiency.Compared with toluene reference fuel,the maximum pressure rise rate of 92# gasoline is highest.because the 92# gasoline has highly volatile,so the premixed combustion ratio is high.Compared with the RON92 fuel,the RON70 fuel has a larger proportion of diffused combustion.The effect of fuel sensitivity on CA50 was significantly different between the RON92 and RON70 groups.In the RON70 fuel,the RON70 fuel has a slightly higher pressure rise rate due to its high activity.Compared with the fuel of RON92 group,the fuel of RON70 group has a small proportion of premixed combustion,so the maximum pressure rise rate is generally 20%~30% less than that of RON92 group.The fuel sensitivity of different RON has different effects on combustion characteristics of partial premixed combustion.Under the condition of small load,the maximum pressure rise rate decreases slightly with the EGR rate increases,but the phenomenon is not obvious.the maximum pressure rise rates among different fuels is minimal.When the EGR is 0,the maximum pressure rise rate is the minimum.At the same EGR rate,the indicate thermal efficiency of the fuel with higher fuel sensitivity is lower.It indicates that under different loads,the fuel sensitivity S coupling different RON have different influence on the indicated thermal efficiency.under higher load,the lower the fuel sensitivity is,the less NOx emission is;the larger the fuel sensitivity,the greater the soot emission is.The NOx emissions of the RON70 group were lower than those of the RON92 group.Compared with the RON92 group,the soot emission of RON70 is higher.Under low load condition,NOx and soot emissions are lower,but due to the combustion stability issue,THC and CO emission increase obviously.fuel with fuel sensitivity S 2 can obtain more stable combustion stability.The experimental results show that,the optimization of fuel sensitivity and other parameters according to different working conditions and octane numbers is an effective way to achieve the goal of high-efficiency cleaning of partially premixed combustion in a larger working range.