High-speed solenoid valve (HSV) is the heart of electronic control fuel system for diesel engines, whose electromagnetic force (EF) determines the dynamic response speed of fuel system. The finite element model of HSV has been established and validated by experiment. Methods of experimental design and correlation analysis have been used for the simulation experiment. The effect laws of six key parameters' interactions on EF under HSV's overall operating conditions have been revealed from the results of the simulation. In addition, three key second-order factors' interaction principles are explained. Results show that under overall operating conditions HSV's EF is influenced not only by its parameters singly, but also parameters' interactions. Index terms: High-speed solenoid valve, electronic control fuel system, experimental design, interaction principles.
With the common-rail fuel injection systems widely used in diesel engines, the pilot injection strategy has been paid more attention for suppressing pollutants emissions and combustion noise. Using pilot injection strategies, leaner and more homogenous mixture formed in pilot spray results in the combustion process partially fulfill Premixed Charge Compression Ignition (PCCI). Therefore the combustion process of diesel engines with pilot injection strategy can be considered as partial PCCI (PPCI). Pilot injection causes the in-cylinder temperature increase before main injection, which shortens the ignition delay of main spray and consequently reduces the combustion noise, so that the pilot injection has potential to extend PPCI combustion model to high load operation. However, the mechanism of pilot injection effects on the combustion noise has not been fully understood, consequently it is difficult to estimate the lower combustion noise among different pilot injection conditions, that results in difficult selection of the pilot injection parameters in proper way. Thus, in this study, experiments were performed on a single-cylinder DI-diesel engine with pilot and main injection under high load operating conditions. The synthesized in-cylinder pressure levels (CPLs) in different frequency ranges as a novel method were proposed to analyze the pilot injection effects on combustion noise. The results reveal that pilot spray combustion mainly influences the high frequency combustion noise, and the later pilot injection timing causes the higher combustion noise. In the case of the short dwell between pilot and main injection, the increasing pilot injection quantity enhances the high frequency combustion noise. Meanwhile because of the pilot injection quantity increase, decrease of main injection quantity leads to lower combustion noise in middle frequency range.
Valve faults diagnosis technique of a diesel engine is studied deeply in this paper. The experiment of valve clearance and air leakage faults are done in a diesel engine, and cylinder head vibration and transient speed signals are measured synchronously on normal and fault conditions respectively. These signals are used to feature extraction. In order to avoid the leakage and aliasing of vibration signal’s frequent spectrum, resample method based on order tracking is proposed, and vibration signal was transformed from time domain to crank angle domain accurately. Considering the non-stationary characteristic of vibration signal, a series of intrinsic mode functions with different scales were obtained using the empirical mode decomposition method, and fault features parameters were extracted through 3D Hilbert spectrums of the intrinsic mode functions. Experimental results show that the method can effectively extract fault features of diesel engine and use them to realize the valve system faults diagnosis further.
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