Coal is currently the most abundant fossil fuel and has many applications.To replace heavy oils used in boilers,pulverized coals are mixed with water,forming coal-water slurry(CWS).CWS is highly viscous and therefore changes the fluid flow of boiler tubes and spray characteristics of atomizers.This study experimentally investigated the characteristics of high-viscosity fluid spray from a twin-fluid atomizer.The characteristics included spray angle,flow field velocity,and particle size distribution.The results indicated that the gas–liquid ratio(GLR)and viscosity were the primary parameters influencing the spray characteristics of high-viscosity fluids.At a GLR of <0.159,the spray angle increased as GLR increased.The particle size of highly viscous droplets was expressed in terms of Sauter mean diameter(SMD).SMD increased with increasing GLR but decreased as viscosity increased.In addition,SMD changed when flow field position varied.SMD was the smallest when the droplet was located at the center of the spray flow field.As the droplet moved toward the outer area of the flow field,its particle size increased.When the GLR of high-viscosity CWS was <0.159,the CWS exhibited unfavorable spray effects; however,as GLR increased,the spray effects enhanced.The findings of this study facilitated understanding the spray characteristics of high-viscosity fluid and how the performance of CWS atomizers can be enhanced.