Modelling and experimental validation of the performance of a digital displacement^® hydraulic hybrid truck

Abstract

The development, modelling and testing of a novel, fuel-efficient hydraulic hybrid light truck is reported. The vehicle used a Digital Displacement® pump/motor and a foam-filled hydraulic accumulator in parallel with the existing drivetrain to recover energy from vehicle braking and use this during acceleration. The pump/motor was also used to reduce gear-shift times. The paper describes the development of a mathematical vehicle model and the validation of this model against an extensive testing regime. In testing, the system improved the fuel economy of the vehicle by 23.5% over the JE05 midtown drive cycle. The validated mathematical model was then optimised and used to determine the maximum fuel economy improvement over the diesel baseline vehicle for two representative cycles (JE05 midtown and WLTP). It was found that the hybrid system can improve the fuel economy by 24%–43%, depending on the drive cycle. When this was combined with engine stop-start, the system improved the fuel economy of the vehicle by 29%–95%, depending on the drive cycle.

Design and experimental validation of a valve-distributed water radial piston pump

“…Eccentric cam-type RPPs use different equipment to displace the piston, such as an eccentric camshaft, crankshaft, or polygonal shaft. 5 RPPs can also be classified into different types in terms of the distribution type, for example, shaft distribution, 6 check-valve distribution, digital-valve distribution, and spool-valve distribution types. 7 Owing to the complete structural integrity of the driven shaft, valve-distribution-type RPPs can be used for high-pressure applications, for example, exceeding 40 MPa, compared with shaft-distribution-type RPPs.…”

“…Danfoss Power Solution Co., Ltd. innovatively developed a Digital Displacement pump to achieve a higher efficiency and faster response rate in hydraulic systems. 5 Manring and Williamson 8 conducted continuous studies to accurately obtain the mechanical and volumetric efficiencies of a Digital Displacement pump. Guo et al 3, 4, 7, 9 developed a spool-valve-distribution RPP and conducted a series of experimental, theoretical, and numerical studies to investigate its structural integrity, flow field of the discharge and suction circuits, dynamic characteristics, and flow ripple reduction.…”

Electro-Hydraulic Variable-Speed Drive Network Technology– First Experimental Validation

“…The success of digital hydraulic technology is dependent on the successful development of new components, especially sufficiently fast switching valves [1][2][3], and have been reported successfully applied in different applications [4][5][6][7][8][9][10][11]. Despite these efforts which have been ongoing for nearly four decades, this technology has yet to make a broad breakthrough in industry.…”

Electro-Hydraulic Variable-Speed Drive Networks—Idea, Perspectives, and Energy Saving Potentials

“…The field of digital hydraulics has mainly evolved via two paths being digital flow control units and digital displacement units. In both cases, the switching valves and their control play a crucial role for system performance and efficiency [1][2][3][4][5]; however, the energy saving perspectives of digital hydraulics are indeed present and potential application areas broad [6][7][8][9][10][11][12][13][14][15].…”