Research on Engine Braking Force and Critical Slope Length Based on Truck Power-to-Weight Ratio

Abstract

Addressing the current issue of inadequate safety on continuous longitudinal slopes of mountain highways caused by “vehicles not adapting to the road,” this paper constructs a model for calculating engine braking force and critical downhill slope length from the truck’s power-to-weight ratio perspective. First, the energy conversion process during the truck’s long downhill journey is analyzed based on energy conservation, and a suitable brake drum temperature rise model is selected and calibrated using real vehicle test data. Through simulation, the relationship between braking torque and rated engine power is quantified, and the mathematical model’s validity is confirmed by comparing the simulation results with model calculations. Finally, the downhill engine braking process for trucks is analyzed, and the quantitative relationship between speed and distance for trucks with varying power-to-weight ratios is determined using differential equations. By integrating the mainstream power-to-weight ratios of Chinese trucks and reasonable deceleration rates, a model for the vehicle speed and critical slope length of 5–8 kW/t power-to-weight ratio vehicles on 1%–12% longitudinal slopes is derived. The results of this research contribute to ensuring the braking safety of trucks with different weight ratios during continuous long downhill travel and provide a reference for establishing reasonable design indexes.