The diesel engine has excellent fuel economy and endurable reliability, and is widely used by various countries as the main power for trucks. However, pollutants such as NOx and IM emitted by diesel vehicles are the major source of pollution in the atmosphere. Therefore, China is gradually tightening regulations on automobile emissions. The diesel fuel injection system plays an important role in the engine's emissions, thus prompting the emergence and application of new fuel injection systems such as common-rail fuel injection systems. However, most of the original engines use in-line fuel injection pumps. Changing the new fuel injection system requires a major structural modification of the engine. A large number of engine optimization test tasks are required. 14 51. Therefore, the implementation of European emissions in some parts of China is currently implemented. Under the premise of laws and regulations, through the use of a new fuel injection pump calibration method, the injection fuel pump cylinders to control the uneven degree of fuel injection, improve diesel emissions, so that the engine to meet European emissions regulations to achieve the level of European emissions, is a feasible method .

The conventional fuel injection pump calibration method usually strictly controls the injection amount of the calibration point and the maximum torque point and the unevenness of each cylinder, and controls the unevenness of the injection amount of each cylinder at the idle point more loosely, and the position of the small rack. Fund Projects: National Key Projects of the Ministry of Education (99A04020210) 1 1 Fuel Injection Pumps ç–‹ 1.1 Fuel Injection Pump Calibration Equipment To accurately calibrate the fuel injection pump, we used the French company EFS on the test bed of ZEXEL's 15NP injection pump. The EM2 single-flow meter measures the injection quantity of each cylinder, its precision is 06mm3. The position of the injection pump rack is precisely controlled by the stepper motor. The test bench is calibrated for the fuel injection pump. The model of the injection pump is P76G11, a mechanical full-scale governor.

1.2 Injector Pump Calibration Method The in-line fuel injection pump usually controls the non-uniformity of the injection quantity of each cylinder at the calibration point and the maximum torque point strictly, and controls the non-uniformity of the injection quantity of each cylinder at idle. There is no special control over the position of the small rack, and the non-uniformity of the injection amount of each cylinder in the small rack position reaches ±10 or more. In order to overcome the deterioration caused by the large uneven fuel injection quantity of each cylinder due to the small rack position, the calibration method of the fuel injection pump adopted in this paper is to determine the displacement of a certain small rack, and to control the rack of the injection pump by a stepping motor. The right moves to the required position, uses a single flowmeter to measure the fuel injection of each cylinder, and repeatedly adjusts the fuel injection pump according to the measurement result until the unevenness of the fuel injection of each cylinder meets the requirements. The same steps as above are used to adjust the fuel injection rate at the idle point, the maximum torque point, and the calibrated power point of the fuel injection pump, and the non-uniformity of the injection quantity of each cylinder is controlled to the required value. When the position of the small rack is different from each other in the degree of unevenness of the injection amount of each cylinder, and only when the adjustment of the injection pump cannot meet the requirements, the replacement of the plunger of the pump is realized. The calibration process of the fuel injection pump needs to be adjusted several times during the calibration of the fuel injection pump so that the unevenness of the injection volume of each cylinder of the injection pump's small rack position, idle speed, calibration point, and maximum torque point is controlled. Within the required value.

1.3 Calibration results of fuel injection pump The above calibration method was used to calibrate a P76S11 type fuel injection pump. In some control points, the injection fuel pump's non-uniformity of fuel injection in each cylinder is shown in Table 2. Test major equipment name Model dynamometer Japan Ono eddy current Dynamometer Exhaust Gauge HORBAMEXA-7000 Exhaust Analyzer Particle Sampling System HOR1BA MDLT-1302TMA Particle Sampling System Combustion Analyzer Japan Ono CB466 Combustion Analyzer Smoke Meter AVL 439 Exhaust Smoke Meter Table 1CA6110 Engine Performance Parameters Item Parameters Engine Type Direct Injection Number of strokes 4 Number of cylinders 6 Displacement/L7.127 Intake method Pressurized intercooled cylinder bore stroke mm110/125 Calibrated power/W155 Calibration speed/(Imil-1) 2500 Combustion chamber type After using this calibration method The cyclical oil supply of each cylinder has a varying degree of change, in which the first cylinder's cyclical oil supply changes the most.

It is the result of comparing the cyclic oil supply of the first full-load part of the first cylinder before and after calibration.

2 experimental program experiments in the CA6110 engine using the original fuel injection pump and the new calibration fuel injection pump on the engine operating characteristics of the typical point of the experimental analysis, and in accordance with ECER49 standards for the engine thirteen conditions discharge experiments. Due to the limitation of experimental conditions, it is not possible to measure the in-cylinder pressures of 6 cylinders at the same time. Therefore, the first cylinder with a large difference in cycle fuel injection volume before and after calibration is selected to measure the in-cylinder pressure. A pressure sensor is installed on the cylinder head of the first cylinder to measure the pressure in the cylinder. Hall sensors are installed on the flywheel to determine the top dead center signal and travel signal of the engine. The combustion process analysis uses a combustion analyzer. The performance parameters of the engine are shown in Table 1. The main equipment used in the test is shown in Table 2. 3 Experimental results and analysis 31 The influence of cylinder pressure and pressure increase rate and the maximum cylinder pressure of the first cylinder which is the full load of the engine 1 500r/nin And maximum pressure increase rate comparison chart. It can be seen that, with the newly calibrated fuel injection pump, the injection fuel pump cylinders have greatly improved the uniformity of fuel injection, the original fuel injection amount is greatly different, and the injection volume of the cylinder is reduced to the average injection volume of each cylinder. Horizontally, the maximum pressure and maximum pressure increase rate in the engine cylinder are reduced, the premixed combustion of the engine is less, the maximum combustion temperature is reduced, and the high-temperature combustion time is also shortened, not only making the engine work softer, but more importantly Effectively reduce NOx emissions.

The maximum pressure in the cylinder at different speeds is compared with that of the engine. It can be seen that with the newly calibrated fuel injection pump, no matter whether it is 2500rmin high speed or 1500rmin low speed, NO x emissions will be obviously reduced, CO emissions will increase, and HC emissions will increase sometimes, partly or at full load. cut back. This is because after adopting the newly calibrated fuel injection pump, the engine's maximum pressure in the cylinder and maximum pressure increase rate are reduced by strictly controlling the circulating fuel supply of the engine and increasing the uniformity of each cylinder, and the engine is in a large pre-mixed area. With a low combustion rate, the maximum combustion temperature reached in the combustion chamber of the diesel engine is reduced, and the residence time of the burned gas at a high temperature is reduced, resulting in a reduction in NOx emissions.

The emission of CO increased because the combustion temperature in the cylinder was low by improving the unevenness of the injection volume of each cylinder of the fuel injection pump. The combustion caused by lean burnout and flame quenching caused by low temperature was incomplete. The CO in the gas rises.

The trend of changes in HC emissions is somewhat confusing, illustrating the complexity of the causes of HC formation. It can be seen that by strictly controlling the non-uniformity of the fuel injection quantity of each cylinder of the fuel injection pump, the combustion temperature in the cylinder is reduced, the partial mixture of the gas mixture is too thin, and the wall quenching may be the main factor that causes the increase of HC emission in most operating conditions. .

From the results of the thirteen engine condition emissions from the engine, the same pattern of changes can be found. That is, while the NOx emissions are significantly reduced, the emissions of M, HC and CO are increasing.

Although from a trend point of view, NOx and PM emissions remain the opposite trend. However, it is particularly noteworthy that after the newly calibrated fuel injection pump was used, NOx emissions decreased from 7815 g/(kWh) to 5.50 g/(kWh) and decreased by 42%. PM emissions increased from 0/(kWh) to 0208 g. /(1Wh) The PM emission increase is only /(1Wh) is not very high, and the engine's emission characteristic h)'s NOx emission is already very low. It is entirely possible to raise the engine's emissions to Europe by appropriately increasing the injection advance angle. It is the newly calibrated fuel injection pump, using the original engine fuel injection advance angle and the injection advance angle 2 ° A ahead of the engine thirteen conditions discharge results comparison chart. This is because after the injection advance angle is increased, the maximum combustion temperature reached in the combustion chamber of the diesel engine is increased, and the residence time of the burned gas at a high temperature is increased, resulting in an increase of NOx emissions. On the other hand, an increase in the injection advance angle will make the mixture more homogeneous and burn more, thus reducing the HC emission value. The advantage of this method is that it not only reduces the overall engine emissions, but also increases the engine's fuel injection timing and engine combustion, improving the engine's economy.

The emission values ​​of 13 operating conditions at different fuel supply advance angles 4 Conclusion (1) After adopting the fuel injection pump with the new calibration method, the engine cylinder pressure and pressure increase rate are significantly reduced.

(2) After the injection pump with the new calibration method, the NOx emissions of the engine are greatly improved. Although the PM emission increases, the increase rate of PM is significantly lower than that of NOx reduction. At the same time, by appropriately increasing the advancement angle of the fuel supply, the emission of the engine can reach the Euro emission level.

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