The Experiment Study Of Fuel Injection Strategy In The Supercharged Diesel Engine On Load Step Condition

In most of the time diesel engine operate in the city are in the transient operating conditions such as start and deceleration. Compared to the steady state conditions, diesel engine operating in the transient conditions occur deterioration of harmful emissions and fuel consumption, etc., Turbo technology used widely aggravates the consequences. In the face of increasingly prominent environmental problems as well as stringent emission regulations, improving the transient performance of diesel engine has become an important direction of the research of internal combustion engine industry. Therefore, this article under the operating condition of constant speed and increasing torque, a turbo electronically controlled common rail diesel engine transient performance was studied. Firstly, the early research is about compare the transient and steady state diesel engine performance comparison. In view of the transient smoke greatly increased and the deterioration of fuel consumption,using different fuel transient rate (FTR) and the section rail pressure control two methods to research transient combustion of diesel engine are studied respectively, focusing on the influence of the emissions and fuel economy. Tests involves in this are conducted under the1650r/min speed, load increasing from10%to100%within5s, the research content is as follows:Fuel transient rate stands the change of the total fuel in the circulation in the diesel engine under transient operating conditions, this study uses the simple broken line fuel transient rate instead of a uniform linear fuel transient rate, in the first paragraph of fuel changes in the rate of transient variable ratio and fuel inflection point load changes affect the performance of diesel engine transient are discussed in this paper, the experimental conclusions are as follows:1. Increasing the first paragraph FTR or the turning points of FTR will decrease the second paragraph transient, making the transient peak cylinder pressure and indicated mean pressure increasing, and quicken the speed of CA50over backwards from TDC(top dead center). Transient smoke diminishs at the beginning then occurs increasing, but NOx emission almost remain the same level.2. For each FTR broken line, under the condition of low FTR turning points, regardless of the rate of the first paragraph of FTR changing high and low, the diesel engine have lower emissions characteristics (FSN values are not more than9%), but high FTR turning points will not only cause the smoke rising rapidly, but also adverse to the effective fuel consumption rate; Although higher rate of the first paragraph of FTR has higher ability to reduce the smoke (minimum only65%of the original engine level), but the instantaneous fuel consumption rate effect deteriorated. Comprehensive emissions and fuel consumption performance, think that the first paragraph of FTR reach25%and FTR turning points before50%LCR (load change rate)will have a better effect.Section rail pressure control actually in the different stages of load rising begin to increase the rail pressure. Rail pressure increase’s stage of load and the degree of rail pressure increasing are the main factors to consider, then compare section rail pressure control and block rail pressure control, test results are as follows:1. The elevated rail pressure increasing can significantly reduce the speed of the CA50from TDC, and Rail pressure increase’s stage of load increasing, CA50has a tendency to accelerate away from TDC. The elevated rail pressure increasing will reduce the smoke emission, but the magnitude of the smoke reduction and rail pressure’s stage of load have a close relationship. At the early stage load, such as30%load and40%load, the minimum smoke after increasing rail pressure value can reach only half of the original engine level, and the average effective fuel compared to the original engine can decrease4%.2. Based on section rail pressure control and block rail pressure control test results, researchers determines section rail pressure control has more advantages. Compared block rail pressure control, when section rail pressure load began to increase from40%, the highest increasing rail pressure will make the smoke emission decrease35%, and the difference of average effective specific fuel consumption at this time is very small. So that the transient conditions in the experiment, section rail pressure control use40%load beginning and rail pressure increase from20MPa-25MPa relatively have more advantages.