The increasingly stringent emission and fuel economy regulations force the advancement of internal combustion engines towards higher power density and lower emissions. Knock and thermal limits are bottlenecks that prevent improvement of the spark ignition (SI) engines' thermal efficiency. Due to its significant knock mitigation and cooling abilities, water injection technology has great potentials in enhancing thermal efficiency of SI engines and thus, regains research attention in recent years. This paper aims to present a comprehensive review of water injection applications on SI engines. Various methods for the implementation of water injection in SI engines are introduced and compared. Methods to maximize the working efficiency of water injection and its detailed physical and chemical effects on combustion and emissions are discussed. It was found that, with different purposes, water injection can improve the combustion and performance of SI engines. Typically, better combustion phasing and thus higher thermal efficiency can be achieved especially under high load conditions. Emissions such as nitrogen oxides and soot can be largely suppressed. However, crucial issues such as water supply and wall wetting still restrict wide application of water injection technology. The detailed kinetic mechanisms of chemical effects and coupling of physical and chemical effects are needed to be investigated.

日益严格的排放和燃油经济性法规迫使内燃机向更高的功率密度和更低的排放发展。爆震和热限制是阻碍提高火花点火 (SI) 发动机热效率的瓶颈。由于其显着的减振和冷却能力，水喷射技术在提高 SI 发动机热效率方面具有巨大潜力，因此近年来重新获得研究关注。本文旨在对 SI 发动机上的注水应用进行全面回顾。介绍并比较了在 SI 发动机中实施注水的各种方法。讨论了最大限度提高注水工作效率的方法及其对燃烧和排放的详细物理和化学影响。研究发现，针对不同的目的，注水可以改善 SI 发动机的燃烧和性能。通常，可以实现更好的燃烧定相，从而实现更高的热效率，尤其是在高负载条件下。可以在很大程度上抑制氮氧化物和烟尘等排放物。然而，供水和壁面润湿等关键问题仍然制约着注水技术的广泛应用。需要研究化学效应的详细动力学机制以及物理和化学效应的耦合。可以在很大程度上抑制氮氧化物和烟尘等排放物。然而，供水和壁面润湿等关键问题仍然制约着注水技术的广泛应用。需要研究化学效应的详细动力学机制以及物理和化学效应的耦合。可以在很大程度上抑制氮氧化物和烟尘等排放物。然而，供水和壁面润湿等关键问题仍然制约着注水技术的广泛应用。需要研究化学效应的详细动力学机制以及物理和化学效应的耦合。