Study on the leakage of plunger pair under static condition in high-pressure common rail injector considering deformation effect

Plunger pair is the key component of high pressure common rail injector and its sealing performance is very important. Therefore, it is of great significance to study the leakage mechanism of plunger pair. Under static condition, the high-pressure fuel flow in the gap of the plunger pair caused the deformation of the plunger pair structure and the temperature rise of fuel. For a more comprehensive and accurate study, the effect of deformation, including elastic deformation and thermal expansion, the physical properties of fuel, including density, viscosity and specific heat capacity, as well as the influence of plunger posture in the plunger sleeve, including concentric, eccentric, and inclination condition, are considered in this paper. Firstly, the mathematical models including Reynolds equation, film thickness equation, non-isothermal flow equation, parametric equation of fuel physical property, and section velocity equation are established. The numerical analysis based on finite difference method for the solution of these models is given, which can simultaneously solve for the fuel film pressure distribution, temperature distribution, thickness distribution, distribution of fuel physical properties, and leakage rate. The models are validated by comparing the calculated leakage rates with the measurements. The effects under different posture of plunger are discussed too. Some of the conclusions provided good guidance for the design of high-pressure common rail injector.

Study on Influencing Factors and Laws of Fuel Injection Consistency of Common Rail Injector

In order to study the influence of parameters of common rail injector internal components on cycle injection consistency, its simulation model is established by AMESim, and the model is validated by the experimental injection rate data. The effects of solenoid valve spring preload, gag bit lift, fuel discharge hole diameter, fuel inlet hole diameter, needle valve lift, needle valve preload and nozzle diameter on the change of injection quantity under different operating conditions are studied by simulation method, and the impact weight of each parameter on fuel injection consistency is analyzed. The results show that the preload of solenoid valve, fuel discharge hole diameter, oil inlet hole diameter, needle valve lift and nozzle diameter are the main parameters affecting the consistency of cycle injection. The percentages of five parameters influencing on the consistency of cyclic injection are 8.68-16.84%, 11.41-23.68%, 17.2086-37.74%, 12.772-18.34% and 9.69-37.27% respectively.

Simulation Study on the Influence of Injector Coupling Leakage on Fuel Injection

In order to study the effect of fuel leakage of an ultra-high pressure common rail injector control valve coupling on fuel injection performance, a simulation model was established by AMESim and the accuracy was verified by fuel injection test data. The leakage law of couples with different clearances was analyzed by using numerical simulation method and then the influence of control valve coupling on fuel injection performance was analyzed. The results demonstrate that the increase of the matching clearance of the slide valve coupling makes the start time of needle valve advanced and delay its end time. The injection rate and injection duration increase with the increase of the matching clearance of slide valve coupling. The increase of the matching clearance of the control plunger coupling keeps the start time of the needle valve unchanged at first, and then delay slightly, while the end time remains unchanged at first, and then show the trend of advance. The injection rate and injection duration decrease with the increase of the matching clearance of plunger coupling.

Development of common rail lube oil injector for large two-stroke marine diesel engines

The two-stroke crosshead diesel engines, nowadays moving the majority of merchant vessels, have lubrication systems which significantly contribute to their overall emissions, since they work on total loss basis: a relevant fraction of lubricant enters the exhaust duct, increasing total exhaust emissions. This paper demonstrates that a viable solution to reduce lubrication system related emissions can be found in the application of a new common rail type ( CR) lubrication system. Particularly, in the first part of this study, a common rail injector was simulated and numerically optimized by means of AMESim. The main parameters influencing lube oil injected mass were identified, with the purpose to design a highly time responsive injector. Therefore, a CR injector was realized and experimentally characterized by means of a dedicated test cell, defining the lube oil injection map over the entire engine load range. Finally, full scale engine tests allowed to evaluate oil loss at exhaust, proposing, and applying the Sulfur tracing methodology. A comparison with a pulse jet lubrication system demonstrated a relevant reduction in oil loss: 100% engine load testes demonstrated decreases ranging from 56.2% to 63.3%, while once fixed the lube oil feed rate to 0.8 g/kWh a maximum reduction in oil loss equal to 66.7% was reached. These results allow nominating the common rail lubrication system as a feasible solution to significantly reduce oil loss at exhaust of large two-stroke marine diesel engines.

Assessment of Technical Condition of an Accumulator Common Rail Injector by Temperature of its Units

This paper presents a method for the vehicle speed estimation with a Fuzzy Logic based algorithm. The algorithm acquires the measurements of the yaw rate, steering angle, wheel velocities and exploits a set of five Fuzzy Logics dedicated to different driving conditions. The technique estimates the speed exploiting a weighted average of the contributions provided by the longitudinal acceleration and the credibility assigned by the Fuzzy Logics to the measurements of the wheels’ speed. The method is experimentally evaluated on an all-wheel drive electric racing vehicle and is valid for the front and rear wheel drive configurations. The experimental validation is performed by comparing the obtained estimation with the result of computing the speed as the average of the linear velocity of the four wheels. A comparison to the integral of the vehicle acceleration over time is reported.