Development and experimental investigation of a rapid non-premixed injection technique for hydrogel extinguishants

• Proposes a novel non-premixed, rapid preparation method for hydrogel extinguishants. • Addresses the challenge of long-range projection of high-concentration hydrogels. • Enhances the jetting efficiency and fire-extinguishing performance of hydrogel extinguishants. • Provides a scalable solution for the widespread use of eco-friendly hydrogel extinguishants. Hydrogel extinguishants, owing to their high water absorption capacity, prolonged moisture retention, strong surface adhesion, and environmental compatibility, have demonstrated considerable advantages in thermal insulation and multi-scenario fire suppression. However, the rapid preparation and long-range delivery of high-concentration hydrogels remain critical technical challenges. In this study, a non-premixed, rapid preparation, and long-distance projection method based on a coaxial jet configuration is proposed for the first time. To validate this approach, a mixed jetting platform is integrated onto a firefighting vehicle, enabling on-site hydrogel synthesis and delivery. Field experiments were conducted under representative conditions, including forest–grassland and chemical storage tank scenarios, along with evaluations of the thermal insulation performance of the resulting hydrogel layers. Results show that within 30 s of mixed jetting, a uniformly mixed hydrogel coating exceeding 3 mm in thickness was formed over an 85 m target area, adhering effectively to vegetation surfaces. Continuous jetting for 230 s produced coatings up to 30 mm thick on tank surfaces located 82 m away. Thermal insulation tests conducted over 10 min revealed that the uncoated substrate surface temperature reached 540 °C, while the hydrogel-coated sample remained at just 34 °C, indicating a 16-fold enhancement in thermal resistance. These findings confirm that the proposed method significantly improves both the projection performance and the fire-extinguishing efficacy of hydrogel extinguishants. The approach provides a scalable and sustainable solution for large-scale fire mitigation and supports ecological restoration in post-fire environments.