Specifying a hydraulic regenerative braking system for an articulated urban delivery vehicle
Previous research has shown that hydraulic systems offer potentially the lightest and smallest regenerative braking technology for heavy goods vehicles. This paper takes the most practical embodiment of a hydraulic system for an articulated urban delivery vehicle and investigates the best specification for the various components, based on a simulated stop-start cycle. The potential energy saving is quantified.
Fuel and emission impacts of heavy hybrid vehicles.
Hybrid powertrains for certain heavy vehicles may improve fuel economy and reduce emissions. Of particular interest are commercial vehicles, typically in Classes 3-6, that travel in urban areas. Hybrid strategies and associated energy/emissions benefits for these classes of vehicles could be significantly different from those for passenger cars. A preliminary analysis has been conducted to investigate the energy and emissions performance of Class 3 and 6 medium-duty trucks and Class 6 school buses under eight different test cycles. Three elements are associated with this analysis: (1) establish baseline fuel consumption and emission scenario's from selected, representative baseline vehicles and driving schedules; (2) identify sources of energy inefficiency from baseline technology vehicles; and (3) assess maximum and practical potentials for energy savings and emissions reductions associated with heavy vehicle hybridization under real-world driving conditions. Our analysis excludes efficiency gains associated with such other measures as vehicle weight reduction and air resistance reduction, because such measures would also benefit conventional technology vehicles. Our research indicates that fuel economy and emission benefits of hybridization can be very sensitive to different test cycles. We conclude that, on the basis of present-day technology, the potential fuel economy gains average about 60-75% for Class 3 medium-duty trucks and 35% for Class 6 school buses. The fuel economy gains can be higher in the future, as hybrid technology continues to improve. The practical emissions reduction potentials associated with vehicle hybridization are significant as well.
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.