A COMPREHENSIVE APPROACH TO ENSURING ENVIRONMENTAL AND FIRE SAFETY OF FIRE TRUCK POWER UNITS

This article examines the environmental and fire safety aspects of fire engine powertrains equipped with sophisticated exhaust gas aftertreatment systems. The objective of this study is to develop a comprehensive approach to assessing and ensuring the safety of fire engine powertrains based on an analysis of actual operating conditions and the adaptation of diagnostic methods. The study utilizes theoretical modeling, a full-scale experiment, and statistical analysis. Two critical operating modes are formalized: prolonged idling (R1) and operation with a significant boost level with the fire engine stationary to drive the pump (R2). A one-dimensional non-stationary model of the catalytic converter is adapted to predict thermal conditions. The results demonstrate that the R2 mode creates an extreme thermal load on the fuel-catalytic system. Modeling reveals that when the mixture is enriched, the temperature of the ceramic substrate in the axial zone of the catalytic converter can reach 950–980 °C, leading to thermal failure. The inadequacy of standard control methods has been experimentally proven: in the R2 mode, critical excesses in pollutant and hydrocarbon emissions and the temperature of the catalytic converter housing (up to 845 °C) were recorded, undetectable at idle. A direct link was established between the use of low-quality fuel (increased content of sulfur, aromatic hydrocarbons, water) and the degradation of the fuel-catalytic system, accompanied by its overheating. Scientific novelty lies in the identification of a consistent relationship between the load-speed cycles of fire trucks, the thermal state of the fuel-catalytic systems and the risk of fire, as well as obtaining information on its serviceability by testing the diesel engine in free acceleration mode. The practical significance lies in recommendations for fire departments, including the implementation of the free acceleration method for diagnosing the fire and environmental safety of the fuel systems of fire trucks with monitoring the temperature of the catalytic converter; setting temperature thresholds to ensure fire-safe operation of the catalytic converter; tightening fuel quality control; adjusting maintenance schedules to account for operating time under extreme conditions.