Study On The Engine Cycle In Actual Operation Of Loader

Since October 1,2014,all non road mobile diesel engines approved for the emission of pollutants must comply with the third stage of the national emission standards for the non road diesel engines.For engines with power output from 75 to130 kW or 130 to 560 kW,the NO_x emission limit is lowered by about 35%compared with the second stage and the PM limit does not change.At present,the electronically controlled high pressure common rail technology is used to meet the third stage emission standards.But the emission test was carried out with only eight steady state conditions,whether the actual operating conditions of the working machines are consistent with the regulation cycle and the emission can meet the requirements of the stage III standard is still unknown.Therefore,it is necessary to collect and analyze the common working conditions of working machines,and to extract the typical cycle which can reflect the real working characteristics and evaluate NO_x specific emission based on the typical cycle.To find out the key operating regions where NOx emission needs to be particularly optimized in the typical cycle,the typical cycle was converted into the engine’s actual steady state cycle by using the fuzzy C means clustering algorithm for guiding the engine’s optimization.There are many kinds of working machines,the wheel loader which is the most common is selected as the research object,NO_x emission in the actual operation is tested by the NO_x sensor and the engine’s working conditions are collected through ECU.The main research contents are as follows:(1)For the engine that will be installed on the loader,the universal characteristic test,NRSC and NRTC were conducted on the engine test bench and the emission characteristics of the engine were analyzed.Then the engine operating conditions and NO_x emission data were collected during the actual working cycle tests of loader.Statistical analysis of the real-life use condition of the loader was conducted.(2)The engine speed was used to identify the individual cycles in the continuous measurements.When the individual cycle was identified and separated,the dynamic time warping distance were calculated between two cycles then the two cycles were alined according to the best matching path of dynamic time warping distance.After alined,the Pearson correlation coefficient between the two cycles was calculated and the correlation coefficient matrix was acquired.The typical cycle of the engine was extracted according to the correlation coefficient matrix and the representativeness of the engine typical cycle was verified.And the NOx specific emissions were calculated based on the short loading cycles.(3)The engine typical cycle was clustered by using the fuzzy C means clustering algorithm and the actual steady state cycle of the engine was acquired.The NOx contribution ratio of each working condition to the whole cycle was calculated,the actual steady state cycle points were sorted and grouped according to the NOx contribution ratio,the high NO_x contribution ratio conditions need to be optimized firstly.This method was verified on the engine test bench through NRTC cycle,the experimental results show that the NOx emission of the NRTC cycle can be effectively reduced by optimizing the steady state point which were clustered from the NRTC cycle.