Floating Clamping Mechanism of PT Fuel Injector and Its Dynamic Characteristics Analysis

PT fuel injector is one of the most important parts of modern diesel engine.To satisfy the requirements of the rapid and accurate test of PT fuel injector,the self-adaptive floating clamping mechanism was developed and used in the relevant bench.Its dynamic characteristics directly influence the test efficiency and accuracy.However,due to its special structure and complex oil pressure signal,related documents for evaluating dynamic characteristics of this mechanism are lack and some dynamic characteristics of this mechanism can＇t be extracted and recognized effectively by traditional methods.Aiming at the problem above-mentioned,a new method based on Hilbert-Huang transform（HHT） is presented.Firstly,combining with the actual working process,the dynamic liquid pressure signal of the mechanism is acquired.By analyzing the pressure fluctuation during the whole working process in time domain,oil leakage and hydraulic shock in the clamping chamber are discovered.Secondly,owing to the nonlinearity and nonstationarity of pressure signal,empirical mode decomposition is used,and the signal is decomposed and reconstructed into forced vibration,free vibration and noise.By analyzing forced vibration in the time domain,machining error and installation error of cam are revealed.Finally,free vibration component is analyzed in time-frequency domain with HHT,the traits of free vibration in the time-frequency domain are revealed.Compared with traditional methods,Hilbert spectrum has higher time-frequency resolutions and higher credibility.The improved mechanism based on the above analyses can guarantee the test accuracy of injector injection.This new method based on the analyses of the pressure signal and combined with HHT can provide scientific basis for evaluation,design improvement of the mechanism,and give references for dynamic characteristics analysis of the hydraulic system in the interrelated fields.

Effect of pulsed laser process parameters on welding quality of automobile fuel injector

In this research, pulverization plate and base of a fuel injector in an automobile electronic-controlled engine was joined by pulsed laser welding. The different welding parameters were evaluated and effect of process parameters on joint characteristics was analyzed. The optimal process parameters were obtained as follows： welding current 120 A, welding speed 600 ram/rain, pulse duration 1.80 ms and pulse frequency 60 Hz. The microstructure of weld metal was investigated. Results show that the fusion zone is austenitic dendrite, the weld center is equiaxed grain, while the transition zone between fusion zone and weld center is mixed crystal with austenitic dendrite and equiaxed grain. The weld layered phenomenon was observed, and eddy caused by keyhole effect is the main reason for the formation of layered structure in molten pool.

Thermal Modeling of a Novel Heated Tip Injector for Otto Cycle Engines Powered by Ethanol

This work presents a thermal modeling of a new cold-start system technology designed for Otto cycle combustion based on the electromagnetic heating principle. Firstly, the paper presents a state-of-the-art review and presents the context of automobile industry where heated injectors are necessary. The novel method of electromagnetic heating principle to solve the cold-start problem is still in the development phase and it enables engine starting at low temperatures in vehicles powered by ethanol or flex-fuel vehicles (FFV). This new system technology should be available as an alternative to replace the existing system. Currently, the cold-start system uses an auxiliary gasoline tank, which brings some inconvenience for the user. Secondly, the aim was also to create a physical model that takes into consideration all the parameters involved on the heating process such as power heating and average heat transfer coefficient. The study is based on the lumped system theory to model the ethanol heating process. From the analysis, two ordinary differential equations arise, which allowed an analytical solution. Particularly, an ethanol heating curve inside the injector was obtained, an important parameter in the process. Comparison with experimental data from other authors is also provided. Finally, a sensitivity analysis of controlling parameters such as heating power and heat transfer coefficient variation. The paper is concluded with suggestions for further studies.

Visualization Experiment and Numerical Analysis of Cavitation Flow Characteristics in Diesel Fuel Injector Control Valve with Different Structure Design

Increasing the injection pressure has been proven an effective method to enhance performance and reduce pollutant of diesel engine.With the increase of the injection pressure,the cavitation damage problem inside common rail fuel injector is more significant,which has direct influences on reliability of diesel engine.While the most studies so far have focused on cavitation occurred in injector nozzle and its atomization characteristics,few researchers studied the cavitation phenomenon in fuel injector control valve.But due to the complexity of flow field and difficulty of experiment,the cavitation in control valve could not be fully described by existing theories.In this paper,the two-dimensional visualization experiment and numerical simulation of control valve was implemented to acquire the image of cavitation intuitively and validate the simulation method and model.Then a new structure design of control valve named convergent model was presented for comparison.The origin model and convergent model with different valve lifts were simulated in three dimensions.The results showed that the sheet cavitation occurred at the surface of seal cone and steel ball then turned to cloud cavitation in downstream area.The intensity of cavitation increased with the increase of valve lift.Convergent model could efficiently reduce the cavitation intensity near the seal area.This research could provide references for engineering optimization design of control valve.