| The vehicle population of China has been increasing quickly with the development of economy; meanwhile, huge energy consumption and environment problem have arisen. Following the stricter laws and government policies, engine factories are striving to reduce the emission from diesel through increasing post processing systems. In this situation, SCR post processing of diesel has become the first choice of engine factories with its superiority. Urea pump is an important part of the urea solution injection measuring system in SCR post processing system. The main function of urea pump is extracting the urea solution from the urea box and maintaining the pressure to a certain level, and then transporting the urea solution to the jet unit to meet the quantity of flow and pressure requirements of jet measuring system. So the reliability of urea pump is crucial in the functioning of SCR post processing system. In real vehicle, urea measuring pumps are divided into air-assisted and non-air-assisted. In practice, urea pump has a high failure rate. Engine factories are difficult to decide the uniformity and deterioration among different pumps because of the differences in operating environments. This research project aims at designing and manufacturing a set of general type of multi-station urea pump duration testing machine, as well as testing the reliability of urea pump through off-line duration test.At first, designing and making a multi-station urea pump offline duration testing machine. According to the requirement of multi-station and characteristics of this offline duration test (actual reaction of the urea ejected by the testing station in reduction pipe is not needed), a specific urea box structure and visible spray element structure have been designed. Meanwhile, a commonly used station is designed to match pumps from different factories by collecting information of normal urea measuring pump in China market. In order to simulate the real working condition of urea pump, the liquid used in the test is urea solution. Thus, a strict sealing test is conducted in the designing process to guarantee the duration performance of the testing machine in the offline duration test. The existence of urea spray in the exhaust port makes it necessary to install filtration unit. Testing machine is equipped with compressor and air bottle, as well as external air supply joint for the convenience of using external air in the laboratory of factory.Then, designing an off-line controlling system which can control emitted dose of the urea pump by sending message to CAN main line. The emitted dose can be both a fixed value and a set of value. The duration of the offline endurance test can be controlled by setting the circulation. The controlling system can both control the whole pumps and control a single one and has the ability to record the real-time data. It can also supervise each pump in real-time by analyzing the message sent by the pump. Besides, the system allows the communication between upper computer and multiple CAN joints which share the same address.At last, the rationality and reliability of the testing machine has been verified by conducting a functioning test of the testing machine. Then, a 1000-hour duration test has been conducted.10 randomly selected pumps from 3 different brands (8 air-assisted pumps and 2 non-assisted pumps) are numbered to be tested in a manual operation of accuracy test. By comparing and analyzing the data from both pretest and posttest, the uniformity, difference and degradation degree among the pumps can be judged to draw a conclusion. |
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