Expreiments Research On Diesel Engine Performance Under Preheat Fuel

As the IV stage of the "compression ignition engines, the fuel gas spark ignition engines and automobile pollutants emission limits and measurement methods (China III, IV, V stage)"(GB17691-2005)had been fully implemented, the diesel engine electronic control technology can effectively reduce the fuel consumption and emissions through flexibly control all conditions’injection quantity, injection pressure and injection timing, and it is represented by the high pressure common rail technology had been concerned by each automobile manufacturers. With the advantages of large compression ratio, high conversion efficiency of fuel to work and low oil consumption, almost all diesel engines used by automobiles can save 30% fuel than the gasoline engines with the same dynamic properties. However, the effect of diesel oil to engine operation in low temperature performance is so great, it can cause faults such as the engine unable to start, the engine cut out (i.e., hang a wax) in the process of driving, poor fuel combustion conditions, emission deterioration an so on. So the study of diesel (0#、-20# and -35# diesel) preheating effect on engine performance gradually in-depth is worth.In this article, through a large number of reading about diesel engines, power to improve energy conservation and pollution reduction as well as the applications of biodiesel at home and abroad literature, summed up the specific impact of the diesel temperature change on the engine’s performance, fuel economy and emissions. Then studied the relation between the fuel temperature and the physical properties of the fuel, the spray characteristics of engine and the combustion characteristic.Experimental results show that the diesel oil’s density, viscosity and elastic modulus of decreases when the diesel temperature increase, and cause decreases of the engine’s accumulator pipe pressure, fuel injection quantity and injection rate, and the engine’s spray evaporation rate can be improved. Physical and chemical parameters and the change of the diesel engine injection performance will make the performance of the engine cylinder pressure and the parameters such as maximum combustion pressure in cylinder reduced, the main combustion period extended at the same time. With the engine fuel injection quantity is reduced, natural showed a trend of low fuel consumption. When the fuel temperature in 50-90 ℃, the fuel consumption rate of three grades of diesel will decrease 0.85%,0.78% and 0.67% every 10℃increased. Due to the total heat released in a single injection of fuel combustion in the cylinder, the mean effective pressure in the cylinder is low, so that the engine’s power decreased on a small scale. When the fuel temperature in 50-90℃, the power of three grades of diesel will decrease 0.43%,0.47%and 0.56%every 10℃ increased. The extended main combustion stage lead to a higher exhaust temperature, and inlet the temperature through turbo device. Fuel can cracking huge amounts of carbon particles under high temperature, so that the engine emission pollutant concentration was increased, the phenomenon will more obvious when the fuel contents higher wax and the pour point depressant is added in the fuel.