## 1 Introduction  
The goal of future diesel engine development will be a reduction in emissions and an improvement in thermal efficiency. High-quality mixtures are the key to achieving these objectives, as they enable greater energy savings and emission reductions. The quality of oil and gas mixtures is determined by the jet atomization performance of diesel fuel. To enhance this performance, researchers have conducted extensive research and numerous trials. [PERSON] found that the spray tip penetration (STP) at low temperatures was faster than the STP at high temperatures [1]. [PERSON] et al. noted that increasing the injection pressure at low injection pressures resulted in a significant reduction in the maximum droplet diameter, and increasing the injection pressure at high injection pressures resulted in a non-significant reduction in the maximum droplet diameter [2]. [PERSON] et al. found that as the injection pressure increased, the STP increased, the droplet velocity increased, and the Sauter Mean Diameter (SMD) decreased [3]. [PERSON] et al. found that low temperatures inhibited spray evaporation more significantly for larger orifice diameters [4]. [PERSON] et al. pointed out that higher spray temperatures and ambient pressures were favorable for jet mixing [5]. [PERSON] et al. found that injection pressure and ambient density had a considerable impact on spray characteristics, and an increase in injection pressure from 50 Mpa to 150 Mpa resulted in a 33.2% enhancement in the vapor-phase penetration of diesel fuel [6]. [PERSON] et al. found that pressure fluctuations inside the nozzle became more intense as the injection pressure was increased and that higher injection pressures increased the spray cone angle (SCA). For every 20 Mpa increase in injection pressure, the SMD decreased by about 9% [7]. [PERSON] investigated the effect of nozzle inlet chamfering angle on diesel spray characteristics, and the results showed that a sharp nozzle inlet produced finer droplets, and STP was smaller [8]. [PERSON] et al. found that the spraying velocity of two-hole asymmetric nozzles was slower than that of single-hole nozzles at the beginning of spraying, and the difference between the two spraying velocities was not obvious when the spraying developed stably [9]. [PERSON] et al. experimentally investigated 20 types of multiple-hole nozzles with different orifice diameters, orifice lengths, and other parameters, and the orifice diameter had a greater impact on the spray, and other parameters and their interactions had an impact on the spray, but none of them had as much impact as the orifice diameter [10]. [PERSON] et al. improved the spray atomization performance of fuel by the ducted fuel injection (DFI) technique of adding a pipe at a certain position of the nozzle outlet [11; 12; 13]. In recent years, researchers have no longer been confined to cylindrical orifices and have begun to investigate the mechanisms by which different orifice shapes enhance the spray atomization process. [PERSON] et al. found that the effect of different tapers on STP in the non-evaporating condition was insignificant, but the SCA was smaller for conical nozzles [14]. [PERSON] et al. found that gas-phase penetration was faster for conical nozzles [15]. [PERSON] et al. concluded that the SCA increased with an increase in injection pressure and that it was greater for elliptical than for circular nozzles [16]. [PERSON] et al. found that the liquid jet from elliptical nozzles exhibited an increase in instability at the same injection pressure [17]. [PERSON] et al. found that circular nozzles had smaller spray widths and smaller SCAs, and STP was shorter for elliptical nozzle shapes than for circular nozzle shapes [18]. [PERSON] et al. 's study found that cavitation improved the primary atomization and brought about the asymmetric jet structure of elliptical nozzle shapes, the fragmentation ratio tended to decrease with increasing eccentricity, and the SCA also decreased gradually [19]. [PERSON] et al.