# Investigation of the Behaviors of Methanol Spray Impingement and Wall Wetting
## 4 Conclusions  
In this paper, the influence of the spray distance (\(D_{imp}\)), wall temperature (\(T_{null}\)), and injection pressure (\(P_{inj}\)) on macro characteristics and wall adhesion characteristics of methanol spray was studied experimentally. The main conclusions were as follows,  
(1) The change of \(D_{imp}\) had a great influence on the shape of spray that, with the increase of \(D_{imp}\), the overall shape of spray before impacting the wall changed from conical to cylindrical. In addition, due to the increase of \(D_{imp}\), the action time of air resistance on spray was prolonged, resulting in greater kinetic energy loss, and more droplets turned from \"splash\" to \"adhesion\" after impinging. Therefore, \(H_{i}\) and \(W_{i}\) were negatively correlated with \(D_{imp}\), but \(M_{f}\) was positively correlated with \(D_{imp}\).  
(2) There were non-monotonical behaviors of the film characteristics versus wall temperature due to a competition between a higher plate droplet temperature difference and a lower heat convection coefficient caused by partial film boiling. \(A_{f}\), \(T_{f}\) and \(M_{f}\) were negatively correlated with \(T_{null}\). However, when \(T_{null}\) continued to rise from 373 K to 423 K, the Leidenfrost effect appeared, increasing \(T_{f}\) and \(M_{f}\).  
(3) \(H_{i}\) and \(W_{i}\) were positively correlated with \(P_{inj}\). The increase of \(P_{inj}\) also led to a larger \(A_{f}\), but when \(P_{inj}\) was 400 kPa, it corresponded to the highest \(T_{f}\) and \(M_{f}\). When \(P_{inj}\) was further increased to 500 kPa, the increase of droplet kinetic energy also led to the \"splash\" behavior of film-forming droplets, resulting in the decline of \(T_{f}\) and \(M_{f}\).  
This study is helpful in further improving the accuracy of the numerical methanol engine model and optimizing the injection strategy of methanol engine. In addition, since  
Figure 19: (**a**) Fuel film area \(A_{f}\), (**b**) Fuel film thickness \(T_{f}\) and (**c**) Fuel film mass \(M_{f}\) on the wall under different \(P_{inj}\) (300 kPa to 500 kPa).  
the actual injection angle of most PFI engines is around 30 degrees, the effect of the injection angle will be further studied later.  
Y.-J.Z.: Conceptualization, data curation, writing--original draft, writing--review and editing. Y.-J.W.: funding acquisition, conceptualization, writing--review and editing. H.J.: writing--review and editing. S.-H.L.: funding acquisition, conceptualization. All authors have read and agreed to the published version of the manuscript.  
This research was funded by [the National Natural Science Foundation of China] grant number [52176128] and [the Shaanxi Provincial Key R&D Program] grant number [2019 ZDLGY15-10]. And The APC was funded by [the National Natural Science Foundation of China (Grant Nos. 52176128)]  
Not applicable.  
The data presented in this study are available on request from the corresponding author.  
The work in Xi'an Jiaotong University was supported by the National Natural Science Foundation of China (Grant Nos. 52176128) and the Shaanxi Provincial Key R&D Program (Grant No. 2019 ZDLGY15-10).  
The authors declare no conflict of interest.