Xiaoli Yu

Research on a pneumatic hybrid engine with regenerative braking and compressed-air-assisted cranking

With the aim of improving the energy efficiency of conventional vehicles, this paper proposes a pneumatic hybrid engine concept, which features regenerative braking and compressed-air-assisted cranking functions. In the regenerative braking mode, the engine works as a two-stroke compressor and converts the kinematic energy of the vehicle into compressed air. In the two-stroke air motor mode, a throttle valve in the intake manifold is used to block the ambient air, and an electropneumatic solenoid valve is employed to control the compressed-air injection. The compressor mode is modelled on the basis of thermodynamics and gas dynamics theories and is improved according to the bench test results of a single-cylinder engine converted from a two-cylinder diesel engine. Transient engine cranking tests are also conducted and are discussed. Urban driving-cycle simulation results show that the fuel consumption of a light-duty vehicle with a pneumatic hybrid system can be reduced by 8%.

A Thermal Equilibrium Analysis of Line Contact Hydrodynamic Lubrication Considering the Influences of Reynolds Number, Load and Temperature.

Thermal effects such as conduction, convection and viscous dissipation are important to lubrication performance, and they vary with the friction conditions. These variations have caused some inconsistencies in the conclusions of different researchers regarding the relative contributions of these thermal effects. To reveal the relationship between the contributions of the thermal effects and the friction conditions, a steady-state THD analysis model was presented. The results indicate that the contribution of each thermal effect sharply varies with the Reynolds number and temperature. Convective effect could be dominant under certain conditions. Additionally, the accuracy of some simplified methods of thermo-hydrodynamic analysis is further discussed.

Preliminary study on compressed air powertrain of a rescue vehicle for mine accidents

This paper investigates the feasibility of applying a compressed air powertrain to mine rescue vehicles, which require strict explosion-proof and flame-proof characteristics. Based on both simulation and preliminary tests of a single-cylinder air-powered engine prototype, the concept of compressed air powertrain for a rescue vehicle is proposed. Compared to conventional internal combustion engines, the exhaust emissions of the proposed air-powered engine concept are innoxious and its gas temperature is very low, which guarantees the safety and explosion-proof requirements. Preliminary selection and matching of both a transmission and final gear reduction are carried out, considering vehicle traction and air consumption performance characteristics. Simulation results show that given properly designed drivetrain gear ratios, the air-powered rescue vehicle can reach a speed of 7 km/h with gear 1 on a 30% slope road. Compared to current products, its feasibility in driving mileage and traction performance are further confirmed.