At present, in order to meet the global requirements for energy conservation and environmental protection, my country has introduced stricter regulations on exhaust emissions from diesel generators. Approved by the State Council, the national third-stage emission standard (referred to as national 3 emission) is implemented nationwide for all non-road diesel generators.
The continuous strictness of emission regulations has promoted the technological progress of diesel generators. From the perspective of development trends, common rail and unit pumps are relatively mature National 3 technologies, but because their core components are monopolized by foreign companies, domestic companies have to assemble Not only the price is high, but also the supply is problematic. In order to solve this problem, HuaChai Deutz generator manufacturer, a Sino-US joint venture brand, has developed a new type of fuel injection system “in-line” after years of practice and research on the basis of analyzing the development of diesel generator emission control technology. Pump + electronic governor + cooling ECR”, this technology has been successful in China. This technology has obvious advantages in terms of cost and maintenance, which is in line with the actual situation in China and has been favored by various enterprises. Next, the editor of Cummins manufacturer will focus on the development of the fuel system in this technical idea.
In order to meet the National 3 emission regulations, it is determined that the combustion performance of diesel generators must be improved, and the fuel system, as the “heart” of diesel generators, is the top priority of research and development. The design and development idea of HuaChai Deutz manufacturer is: the injection pressure at the nozzle end of the fuel system should reach 130MPa or more; the top clearance plunger couple is used to realize the fuel injection timing; the electronic governor is used to improve the system response speed and meet the European load response test (ELR) test cycle requirements.
fuel injection pump design
To increase the injection pressure of the fuel system, the pressure at the pump end must be increased first. For the in-line pump, the most direct measure is to increase the fuel supply rate. Therefore, the adopted solution is: based on the enhanced Pz mechanical pump, the diameter of the plunger is increased , to increase the cam lift; at the same time, in order to increase the reliability while ensuring the oil supply rate remains unchanged, the idea of “large lift and small plunger diameter” is adopted, that is, in the design and calculation, the cam should be increased as much as possible to meet the requirements. Lift size, and increase the plunger diameter size as small as possible. In this way, under the same pump end pressure, the contact stress of the camshaft can be reduced, and the volumetric efficiency of the high-pressure oil chamber of the plunger can be improved. Finally, the cam lift is designed to be 14mm, the plunger diameter is designed to be 12mm, and it is matched with the small-diameter fuel injection nozzle, which greatly increases the injection pressure of the nozzle end of the fuel system, far exceeding 130MPa, meeting the fuel supply requirements. The test results related to the fuel injection pressure are shown in Figure 1. In addition, due to the increase of the fuel injection pressure of the fuel system, the driving torque of the fuel injection pump also increases, which leads to a decrease in the reliability of the traditional mechanical advancer. . In order to solve this problem, the current method is to cancel the traditional mechanical advancer and design and develop the top clearance plunger couple to meet the fuel injection timing requirements. Through the test, the fuel injection advance characteristic of the improved fuel injection pump can fully meet the requirements.
Actuator Design and Structural Arrangement
At present, domestic actuators mainly include proportional electromagnet actuators and stepping motor actuators. In the design scheme, the proportional electromagnet with large thrust is selected as the actuator. It has the advantages of simple structure, high reliability, large thrust, and fast response. Features, can achieve precise control of displacement, and easy maintenance. In the cloth table where the proportional electromagnet is connected with the pull rod of the fuel injection pump, using a lever mechanism to connect the actuator and the pull rod is a common connection method. This method can shorten the space size of the governor, but in the process of adjusting the fuel supply In the middle, it is easy to produce a dead angle of fuel supply, which makes the fuel injection pump stuck, and the extra lever mechanism is easily damaged and has poor reliability. For this reason, the executive element and the pull rod can be directly connected, that is, the linear push control method is adopted to avoid the above-mentioned problems, making the governor more simple, effective and reliable.
Design of electronic governor
At present, the electronic governors researched at home and abroad mostly adopt the displacement control method, and the displacement of the fuel injection pump pull rod is adjusted through the electronically controlled actuator, so as to achieve the purpose of controlling the circulating fuel supply. There are mainly four aspects involved in the design of the electronic governor. Structural arrangement of the electronic governor The optimization of the overall layout ensures the installation of the electric adjustable pump on the diesel generator and avoids the modification of the original machine as much as possible. In the design of the shape of the governor, combined with the limited installation space of the diesel generator, the structure is compact, and this requirement is taken into account in the design of each component, and its peripheral size is controlled to save space. The electronically adjusted fuel system improves the combustion efficiency of the diesel generator itself, and optimizes the matching of the diesel generator, such as: improving the design of the combustion chamber; improving the design of the valve mechanism; improving the design of the intake and exhaust system; improving the booster system, adjusting the supply Oil advance angle and other measures can effectively reduce NO emissions, and at the same time balance the content of NO and particles in the emissions to meet the requirements of emission standards. .
Features and layout of position sensors
Among various position sensors, the Hall position sensor has a simple structure and small size, which is convenient for installation in the governor. The selection of this sensor can effectively save space and help optimize the overall size and structure of the governor; in addition, The sensor is cheap, the sensitivity can fully meet the design requirements, and the production cost can be reduced.
HuaChai Deutz generator manufacturer designed and developed this complete set of electronically adjustable fuel system. The system is combined with existing mature models to meet the national 3 emission standards through matching. Firstly, the fuel injection pump and injector are designed and improved to increase the injection pressure to more than 160MPa, which makes the fuel atomized particles smaller, the fuel and gas mixed more fully, and the combustion is further improved; secondly, the electronic governor is designed, and the governor It not only improves the response of the fuel system, but also has the characteristics of small size, simple structure, reliable performance, and convenient use and maintenance; the ESC test cycle results show that compared with the original machine, the NO is reduced by 10%, and the particles are reduced by 60%. requirements of emission standards.