The design of bipolar plates is critical for improving the performance of proton exchange membrane fuel cells (PEMFCs). In this research, a new additional outlet based on a PEMFC’s parallel flow field was proposed, and three different positions of outlet were designed on the target side of gas flowing in parallel channels. The results revealed that the additional outlets are able to increase the gas speed through channels near the additional outlets, which results in a lower water saturation and a more uniform distribution of oxygen concentration at the interface between the catalyst layer (CL) and gas diffusion layer (GDL). With the variation of the outlet position in the target side, it was found that the additional outlet set in the middle of the target side exhibits the highest increase of peak power density, namely, 13%. Furthermore, the optimal position of the additional outlet was proved to be suitable for PEMFCs with various active surface areas, indicating the universality of the present results in the study.

The automobile industry puts forward higher requirements for the design and manufacture of steel pistons. However, the welding of 42CrMo steel pistons still has unsolved technical problems, especially welding defects that cannot be directly detected, such as pores, which are easily generated inside the weld. A plasma experiment of laser-metal active gas arc (MAG) hybrid welding 42CrMo steel was conducted in this paper, and plasma signals inside and outside the keyhole were detected during the laser welding, leading laser laser-MAG hybrid welding, and leading arc laser-MAG hybrid welding of 42CrMo steel. The characteristic parameters such as electron temperature and electron density were calculated and analyzed to investigate the relationship between plasma behavior and the formation of weld porosity in the welding process of 42CrMo steel. Based on the fluctuations in plasma electron temperature and electron density, the prediction of pore formation in the weld of 42CrMo steel was made, aiming to provide guidance for achieving a stable and reliable laser-MAG hybrid welding process for 42CrMo steel.

The application bottleneck of laser welding is being gradually highlighted due to a high prevalence of porosity. Although laser welding technology has been well applied in fields such as vehicle body manufacturing, the suppression of weld porosity in the laser welding of stainless steel containers in the pharmaceutical industry is still challenging. The suppression of bottom porosity was investigated by applying ultrasonic vibration, changing welding positions and optimizing shielding gas in this paper. The results indicate that bottom porosities can be suppressed through application of ultrasonic vibration at an appropriate power. The keyhole in ultrasound-assisted laser welding is easier to penetrate, with better stability. No obvious bulge at the keyhole rear wall is found in vertical down welding, and the keyhole is much more stable than that in flat welding, thus eliminating bottom porosity. The top and bottom shielding gases achieve the minimal total porosities, without bottom porosity.