Current Issue : October-December Volume : 2023 Issue Number : 4 Articles : 5 Articles
The structure of the pressure swirl nozzle is the key factor affecting the atomization quality. Optimal design of nozzle structure is conducive to improving the atomization quality and has important significance for improving the efficiency and stability of the combustor. The effect of the swirl section diameter, the contraction section angle, the straight section diameter, and the expansion section angle on the spray cone angle and the liquid film thickness is studied by numerical simulation. The results show that the liquid film thickness and spray cone angle both decrease with the increase of the expansion section angle. As the straight section diameter increases, the spray cone angle and liquid film thickness both increased. Both the spray cone angle and the liquid film thickness have an optimal contraction angle value that is 60° and 45°, respectively. The increase in the ratio of the swirl section diameter to the straight section diameter can increase the liquid axial velocity. When the nozzle outlet has an expansion angle, the thickness of the liquid film is reduced. When the expansion section angle, the straight section diameter, the contraction section angle, and the swirl section diameter of the nozzle is 30°, 4 mm, 45°, and 12 mm, respectively, the atomization performance of this nozzle is the best....
The marine diesel engine is an important power machine for ships. Traditional machine learning methods for diesel engine fault diagnosis usually require a large amount of labeled training data, and the diagnosis performance may decline when encounters vibrational and environmental interference. A transfer learning convolutional neural network model based on VGG16 is introduced for diesel engine valve leakage fault diagnosis. The acquired diesel engine cylinder head vibration signal is first converted to time domain, frequency domain, and wavelet decomposition images. Secondly, the VGG16 deep convolutional neural network is pretrained using the ImageNet dataset. Subsequently, fine tuning the network based on the pretrained basic parameters and image enhancement methods. Finally, the well-trained model is adopted to train and test the target dataset. In addition, the cosine annealing learning rate setting method is used to make the learning rate close to the global optimal solution. Experimental results show that the proposed method has higher accuracy and better robustness against noise with a small sample dataset than traditional methods and deep learning models. This study not only demonstrates a novel view for the diagnosis of marine diesel engine valve leakage, but also provides an applicable diagnosis method for other similar issues....
This paper investigates the broaching process of phosphor-bronze (C54400) under different cutting conditions, and the influential factors on cutting force and surface quality are studied. The simulated cutting force implementing the force model based on the energy components also agrees with the results of experiments. In the first part, different cutting velocities of VC 5, 10, 15, and 20 m/min are studied. In the second part, harmonic vibrations in the form of a sine wave with precise amplitude (A 1 m/min) and frequencies (F 55, 65, 85, and 95 Hz) are added in the direction of the cutting velocity. The results revealed that an increase in the cutting velocity from 5 to 20 m/min results in a 40% enhancement in surface quality and a 20% decrease in the cutting force. Additionally, harmonic vibrations of higher frequencies can also contribute to a 35% higher surface quality and a 20% lower cutting force. This study will ultimately improve productivity in industries where broaching is considered the main manufacturing approach, such as automotive and aerospace, in which precision and accuracy are of paramount importance....
Aiming at the problem that, under certain extreme conditions, relying on tire force or tire angular velocity to represent the longitudinal velocity of the unmanned vehicle will fail, this paper proposes a longitudinal velocity estimation method that fuses LiDAR and inertial measurement unit (IMU). First, in order to improve the accuracy of LiDAR odometry, IMU information is introduced in the process of eliminating point cloud motion distortion. Then, the statistical characteristic of the system noise is tracked by an adaptive noise estimator, which reduces the model error and suppresses the filtering divergence, thereby improving the robustness and filtering accuracy of the algorithm. Next, in order to further improve the estimation accuracy of longitudinal velocity, time-series analysis is used to predict longitudinal acceleration, which improves the accuracy of the prediction step in the unscented Kalman filter (UKF). Finally, the feasibility of the estimation method is verified by simulation experiments and real-vehicle experiments. In the simulation experiments, medium- and high-velocity conditions are tested. In high-velocity conditions (0–30 m/s), the average error is 1.573 m/s; in the experiment, the average error is 0.113 m/s....
Different investigations of the union of dissimilar materials such as stainless steel and different castings have been carried out, but rapid cooling immediately after welding has not been considered, in this work it was investigated how rapid cooling affects the metallurgical microstructure and consequently the mechanical properties. The effect of welding parameters on the microstructure and mechanical properties of the joint between dissimilar metals, an E-308-16 austenitic stainless steel and Gray Cast Iron was also analyzed. Gray cast iron samples (GCI) were fabricated, welded and cooled. The main welding parameters studied in this work are the welding technique and the type of filler electrodes. Flux-coated electrode E-308-16 was applied for this different joint. An experimental study was carried out for the analysis of welded joints of similar and dissimilar steels. The microstructure of the welded joints was analyzed using an optical microscope, in the base metals, heat affected zone (HAZ) and filler metal. The mechanical properties of the welded joints were evaluated by Vickers microhardness and tensile strength tests. The hardness profile showed differences in hardness between the base metals, the heat affected zone and the filler metal. The metallurgical microstructures observed along the welded areas corresponded to the profile. The hardness differences determined the effect on the mechanical and metallurgical characteristics of the welded samples as a result of the cooling rate differences. This research work is important because it allows us to analyze the possibility of reworking pieces of dissimilar materials by welding or, failing that, to determine if this may or may not be possible....
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