Numerical And Experimental Study Of A New Amplified High Pressure Common-rail System

Compared with high pressure common-rail system without augment structure,most parts of the new amplified high pressure common-rail system are under arelatively low pressure environment, so the system could get a high fuel pressure aswell as the low requirement of tightness. And it fits the industrial conditions of ourcountry very much. At the meantime, the system could achieve different fuel injectionmodes and injection rates through flexible control methods to meet the demand ofdifferent engines’operating conditions.For the new amplified high pressure common-rail system, the text analyzes thetotal oil and total energy needed by the system as well as the structure of hydraulicvalve. Then we take the works of simulation and experiments. We defined the fuelefficiency and energy efficiency to measure the oil and energy needed by the system;we also make sure the best structure of hydraulic valve for the lowest energyconsumption in three different structures.The text analyzes the system’s working principle, then divides the system intofour kinds of mathematical models: the centralized volume control equation, the valveelement movement equations, couplings leaked equations and electromagneticcomputational model. Then we established the simulation model by Flowmaster,which includes oil pump, solenoid valve, pipes, augment module, injector andhydraulic valves. At last, we verified the solenoid valve model, injector model andaugment model through the experiments.The total oil and energy needed by the system are indicated by the fuel efficiencyand energy efficiency. The factors that affect fuel efficiency and energy efficiency ofthe system are studied. The factors include the rail pressure, the diameters of controlchamber’s oil inlet hole and outlet hole, the pressured chamber volume. The researchresults show that: When the rail pressure increases, the fuel efficiency also increasesgreatly, but the energy efficiency declined largely. There is a trade-off relationshipbetween them. The return oil drops down as the diameters of oil inlet hole and outlethole decreases, and it leads to the improvement of both fuel efficiency and energyefficiency. Furthermore, the oil inlet hole’s diameter has a larger consequence on fueland energy efficiency than the oil outlet hole’s diameter. At last, the pressuredchamber volume’s enlargement will increase the return oil as oil compressibility. Andrail pressure is lower, this effect is more obvious. So the pressured chamber volumeshould be reduced as much as possible to avoid the decline of fuel and energy efficiency.We pointed out three different structures of hydraulic valves: ball valve,ball-slide valve and slide valve. And based on it, the simulation model is established.The results indicates: compared with the other two structures, slide valve avoids thephenomenon of direct fuel leak under high pressure condition; at the meantime, slidevalve solves the problem of throttle loss in the fuel flow process which has enoughflow area.