[hal-01077636] Influence of biodiesel and diesel fuel blends on the injection rate and spray injection under cold conditions

Fossil fuel supplies are decreasing every day due to excessive energy requirements This problem can be solved by partly replacing fossil fuel with renewable biodiesel fuel However during the star-up of the engines under cold temperatures conditions can be different where biodiesel are used due to the low fuel injection pressure and the high cloud point and high pour point It is consequently of interest to understand the behavior of the injector under cold conditions when operating with biodiesel and the impact on the combustion process This article presents the experimental study of diesel fuel and biodiesel blends on injection flow Bosh CRI 31 piezoelectric injection was used The injectors are used on present diesel engine Five fuels were tested diesel fuel winter diesel fuel two diesel– biodiesel blends B20 B50 and pure biodiesel B100 Injection pressures were set at 30-60 MPa for the study of the injection flow characteristics in room temperature non-vaporizing conditions and cold conditions Under cold temperature268 K and 265 K the experimental results show that not effect of the injection delay all fuels the delay closing in the fuel of injection increases with the biodiesel content B100 fuel showing the most delayed closing at cold temperature the discharge coefficient for all fuels is lower than at room temperature By increasing the fraction of biodiesel in the blend the discharge coefficient does not change significantly The viscosity of fuel seems pilot the closing delay and influence the discharge coefficient but for negative temperature it seems not be the alone property to modify the injector performance In fact with B100 the discharge coefficient tends to be strong lower than that of diesel and biodiesel blended fuels However By decreasing the temperature of fuel the discharge coefficient tends to be same for diesel fuel and biodiesel blends The result for spray behavior shows that spray penetration increases and spray angle strongly decreases Those behaviors are particularly clear for the B100 fuel In effect when the temperature is reduced to a value close to the fuel cloud point their flow abilities and spray behaviors are worsened Introduction Biodiesel is a very interesting fuel because it is renewable thus increasing energy security environmentally friendly and has a higher cetane number and a lower sulfur and aromatic content The main disadvantages of biodiesel are its higher viscosity lower energy content higher cloud point and pour point higher nitrogen oxide NOx emissions lower power and high price 1 However many countries can produce their own biodiesel and blends with diesel fuel of 2-20% 23 Governments eg the European Union the USA have stipulated that fuel should be blended with biodiesel 3 although consumers are unconvinced about the use of biodiesel fuel blends in automotive engines because of concerns about combustion efficiency pollutant emissions and the effects on engine components Attentions are especially focused on pollutant emissions from biodiesel fuelled vehicles as in 2014 they have to respect Euro VI regulations The new standards include the cold-start problems evaluation of post-treatment strategies and EGR at low temperature Quality cold start at 266 K is a benefit that will become increasingly stringent For these temperatures the viscosity is greater The blending of biodiesel with diesel fuel causes of the cloud point the cold filter plugging point CFPP pour point or to increase which can clog the fuel lines and filters of the vehicle's fuel system 4



from HAL : Dernières publications http://ift.tt/1oOroAT