Internal combustion engines have played a crucial role in the advancement of society. Consequently, there has been a persistent need to enhance their efficiency and performance. The water-injected six-stroke engine is based on conventional four-stroke engines, producing additional power by injecting water into the hot combustion products during the expansion stroke, thereby increasing the overall engine efficiency. However, a comprehensive review that consolidates existing knowledge and identifies future research opportunities in six-stroke engine technology is lacking. This study addresses this gap by thoroughly examining the thermodynamic operation of six-stroke engines and analyzing the impact of water injection on engine performance. The review covers literature from 1994 to 2023, categorizing studies based on the modeling approach, working fluid, thermodynamic cycle, and consideration of heat transfer. Among the 18 analyzed articles, predominantly published from 2015 to 2019, half utilize analytical models, while the rest employ experimental models addressing heat transfer losses. Notably, water injection exhibits a substantial influence, manifesting as a 5.18% increase in brake power and a 1.55% enhancement in thermal efficiency, particularly with acetylene as the working fluid. Finally, a literature overview of water injection in hot gas environments within the engine cylinder was conducted in addition to a preliminary thermodynamic analysis of the Otto and Diesel cycles to compare different configurations outlined in the literature. The lack of studies, experimental setups, and non-idealized models that consider factors such as heat transfer or water evaporation during injection is evident. By critically synthesizing the available literature, this study offers valuable insights into the potential advantages, limitations, and prospects of six-stroke engine studies.

内燃机在社会进步中发挥了至关重要的作用。因此，一直需要提高其效率和绩效。喷水六冲程发动机基于传统四冲程发动机，通过在膨胀冲程期间将水注入热燃烧产物来产生额外的动力，从而提高发动机的整体效率。然而，缺乏整合现有知识并确定六冲程发动机技术未来研究机会的全面审查。本研究通过彻底检查六冲程发动机的热力学运行并分析注水对发动机性能的影响来解决这一差距。该综述涵盖 1994 年至 2023 年的文献，根据建模方法、工作流体、热力循环和传热考虑对研究进行分类。在主要于 2015 年至 2019 年发表的 18 篇分析文章中，一半采用分析模型，其余则采用解决传热损失的实验模型。值得注意的是，注水表现出显着的影响，表现为制动功率增加 5.18%，热效率提高 1.55%，特别是在乙炔作为工作流体的情况下。最后，除了对奥托循环和柴油循环进行初步热力学分析之外，还对发动机气缸内热气体环境中的注水进行了文献综述，以比较文献中概述的不同配置。显然缺乏考虑注射过程中传热或水蒸发等因素的研究、实验装置和非理想化模型。通过批判性地综合现有文献，本研究为六冲程发动机研究的潜在优势、局限性和前景提供了宝贵的见解。