Lateral stability analysis of the tractor/full trailer combination vehicle
This paper presents a linear dynamics model of tractor/full trailer with six degrees of freedom, and a series of simulations are performed on obstacle avoidance manoeuvers in which the combination vehicle moves at a constant forward speed. It is found that the ratio of the peak lateral acceleration of the full trailer's center of gravity (CG) to that of the tractor is 2.3, meanwhile, the articulated angle of the trailer is larger than that of the dolly. This phenomena, defined as the ‘rearward amplification ratio’(RWA), leads vehicle to rollover easily. A larger wheelbase of trailer would be useful to improve the lateral stability of the combination vehicle but it is limited by width of the road. Acting a resistive torque on the turntable can be absolutely effective in improving the dynamics stability of the tractor/full trailer combination vehicle but if acted at hitch point it has little improvement.
Study on Directional Stability of B-Double Vehicle Combination
B-double is one kind of vehicle combinations with three vehicle units structurally and widely applied in cargo transport, so its directional stability analysis is crucial but more complex than a car. Directional stability was related with vehicle operating conditions and structure parameters. A basic linear dynamic model with four degrees of freedom for B-double was developed with a special method for simplification in a calculation process. The method was verified from the simulation results with MATLAB. The step input is tractor’s steering wheel angle, so the steady-state yaw rate gains with understeer gradient for three vehicle units were solved. Steady-state relative gain was also derived and has an impact on directional stability, which could be influenced by the structure parameters, such as body mass (cargo weight), tire cornering stiffness of rear axle, location of mass center, wheelbase, and location of articulated point. The results indicate that increasing body mass and tire cornering stiffness of rear axle appropriately, moving backward mass center, and moving forward articulated points could increase the understeer gradient, which results in the improvement of directional stability. It is theoretical basis for the stability tests and structure design of B-double.
HYPERGOLIC REACTION MECHANISMS OF CATALYTICALLY PROMOTED FUELS WITH ROCKET GRADE HYDROGEN PEROXIDE
Abstract The coupling of the physical and chemical processes controlling the ignition delays (τ ign ) of hypergolic propellants complicates the direct analysis of the transient ignition processes. The transport properties of both the propellants and the ambient gas, and the heat of vaporization and reaction affect τ ign and must be considered experimentally. Furthermore, since hypergolic ignition occurs, by definition, on contact, the mechanics of initial contact and subsequent mixing can affect τ ign and must also be considered. Experimental results from a study of the hypergolic ignition of a catalytically promoted fuel with rocket grade hydrogen peroxide (RGHP) are presented. Statistical analysis of the experimental data was conducted to evaluate the relative effects of RGHP concentration, initial ambient pressure, and the ambient gas on τ ign . At RGHP concentrations of less than 92% in water, stable ignition was difficult to achieve. At sufficiently high Lewis number, an oscillatory ignition process is observed. A phenomenological model comprising mixing, RGHP decomposition, fuel heating and vaporization, and auto-ignition is presented and compared to the experimental results.