1) The specific fuel consumption of cottonseed diesel fuel is higher than that of diesel fuel, and increases with the increase of cottonseed oil percentage. The specific fuel consumption of 40%, 50%, 60%, 70% cotton diesel oil and pure cottonseed oil is 5% higher than that of diesel oil under calibration conditions. 3%, 7. 3%, 8%, 10.9% and 16.2%. This is mainly due to the low calorific value of cottonseed oil, which is about 8% of that of diesel. Directly from the fuel consumption does not fully explain the economic problems, we should also discuss the thermal efficiency.
2) in order to evaluate the economy of engines, their effective efficiency can be compared. Under the calibration condition, see the table 2 in cotton blended with different mixing ratio. According to table 2, the efficiency of burning cotton diesel is very close to that of diesel fuel. According to the measured dynamometer diagram, the indicated efficiency of Daoxiang is 45.1% when using cottonseed oil and 4.2% when using diesel oil. It shows that when burning cottonseed oil, the combustion process is better, but the mechanical efficiency is low. The low mechanical efficiency may be due to the high viscosity, poor fluidity and high resistance of cottonseed oil, as well as the increase of advance angle of oil supply and the high pressure in cylinder, resulting in the increase of mechanical loss. Although the mechanical efficiency of cottonseed oil is low, the economy of the whole machine is close to that of diesel oil.
Therefore, from the two aspects of specific fuel consumption and thermal efficiency, the mixing ratio is 40 ~ 60%. LF8Uunder variable load conditions, the effective efficiency of diesel and cottonseed oil is shown in Fig. 3 under several JUs (speed and load change). It can be seen that the efficiency of cottonseed oil is slightly lower than that of diesel oil at high speed and low load, and the efficiency of cottonseed oil at low speed and high load (n=1600~185 Or/m i) is higher than that of diesel oil at calibration conditions. This may be due to the lower in-cylinder temperature, higher viscosity of cottonseed oil and poor atomization at low load. With the increase of load, the temperature in-cylinder increases, and the temperature at the injector increases, which reduces the viscosity of cottonseed oil and improves the atomization, thus improving the combustion process. At high load, for diesel fuel, the mixture becomes too thick due to the increase of circulating fuel supply, the combustion deteriorates J, and the knife decreases. For cottonseed oil, on the one hand, the engine temperature increases at high load.
1) Small-scale agricultural diesel engine without any modification, short-term internal combustion cotton-wood blend or pure cottonseed oil is completely feasible, the engine works normally, can achieve the calibration power, higher specific fuel consumption, but the effective efficiency is very close to the use of diesel. Cottonseed oil can be used as emergency fuel in the case of diesel oil shortage in rural areas, especially in the busy season of March and Autumn or in drought and flood control. 2) Cottonseed oil and diesel oil can be mixed in any proportion. In terms of specific fuel consumption and effective efficiency, the weight percentage of cottonseed oil in the mixture should be 40-60%. 3) Whether pure cottonseed oil or cottonseed-wood blend oil is used, the advance angle of oil supply must be increased, which is about 2-3 "C A" higher than that of diesel oil. 4) When cottonseed oil is used, the exhaust temperature is basically the same as that when diesel oil is used, but the exhaust smoke volume decreases significantly.
5) The ignition lag period of cottonseed oil is basically the same as that of diesel oil. The heat release rate of cottonseed oil is less than that of diesel oil at the initial stage of combustion, but greater than that of diesel oil at the later stage. The heat release of cottonseed oil is more uniform in the whole combustion process, and the end of combustion is earlier than that of diesel oil, and the afterburning rate is less than that of diesel oil. 6) compared with diesel fuel, diesel engine works more softly when burning cottonseed oil. 7) When cottonseed oil is used, the carbon deposit is more serious, but if it is used in a short time and the maintenance period is shortened appropriately, the effect will not be great. 8) When the ambient temperature exceeds 10 C, heating water in the water tank and using cotton-wood blend oil, it is not difficult to start the diesel engine directly, but it is difficult to start the diesel engine directly when using pure cottonseed oil. In winter, a set of preheating device can be designed to use exhaust heat to heat, or to start with diesel oil and then work with cottonseed oil. 9) adding a small amount of additives in cottonseed oil can reduce viscosity, improve atomization and reduce fuel consumption. This is a subject worthy of further experimental research.See the news list>>