Experimental Analysis, Modeling, and Control of Volumetric Radial-Piston Pumps

Abstract

An experimental-theoretical study has been carried out on high-pressure volumetric radial-piston pumps for diesel fuel injection systems. The dependence of the pump inducted flow rate on speed and load was investigated and the characteristic curve of the pump cooling-lubrication circuit was derived. The head-capacity curves were determined for different types of pumps at different revolution speeds and compared with the injector flow requirements in order to evaluate the pressure-control strategy efficiency. An insight into the ageing effects on the pump performance was also provided. Furthermore, the dynamic pump behavior was investigated, with specific reference to the flow-rate ripple at the delivery port. A general analytical expression has been derived for the volumetric efficiency. Furthermore, a specific procedure has been developed and applied to the experimental evaluation of the fuel leakages in pressure control valve (PCV) integrated pumps. Finally, the mechanical-hydraulic efficiency of the pump has experimentally been assessed as a function of head and speed in order to obtain a reliable evaluation of the pump shaft power and torque at different working conditions.

Determination of the transfer function between the injected flow-rate and high-pressure time histories for improved control of common rail diesel engines

“…The theoretical time history, plotted with a dashed line, was computed by simulating the pump compression phase and taking into account both the fluid compressibility and thermal effects related to fuel compressibility, according to the procedure described in Catania and Ferrari. 5 The sudden flow-rate increases that occur at time instants t = 6 ms, t = 26 ms and t = 46 ms refer to the pump delivery valve opening timings. The experimental time history, reported with a solid line, was obtained from a prototypal flowmeter that is capable of evaluating the instantaneous flow-rate in high-pressure liquid flows.…”

“…The FMV is instead placed at the CR high-pressure pump inlet, and it controls the flow-rate sucked by the pump on the basis of the injector requirements. 5 In all of the abovementioned configurations, the control system can only influence the injected flow-rate indirectly, by conditioning the time-averaged pressure level, upstream of the injector, in the rail where the pressure sensor is installed. On the other hand, the injected flow-rate and the injected volume depend on the pressure transients at the injector nozzle, which are significantly different from those in the rail, and on other mechanical variables, since the needle kinematics affects the restricted needle-seat passage flow-area to a great extent.…”

Fully predictive Common Rail fuel injection apparatus model and its application to global system dynamics analyses

“…The instantaneous volume of each pumping chamber can be expressed as a function of q and its mathematical formula depends on the cam and piston geometry. 22 A constant value of K leak can be used in equation 3, 22 even though a more accurate K leak formula, which depends linearly on p nom in order to take dilation into account, can also be applied. The simpler approach, in which K leak is assumed constant, has been proved to be able to predict the experimental volumetric efficiency data for p nom 41400 bar with a lower inaccuracy than 4% and with a further penalty of 2% compared to the formula that makes K leak depends linearly on p nom (the latter approach makes the inaccuracy be lower than 2% up to 1400 bar).…”

“…Innovative injector hydraulic layouts, such as pressure-balanced pilot valves, [17][18][19] three-way pilot valves, 20 pressure-amplified injectors 21 or bypass ducts that connect the delivery to the control chamber of the injector, have been applied to improve the dynamic performance, to reduce power losses and to increase the maximum pressure. Furthermore, attention has also been paid to the design and experimental analysis of high-pressure pumps 22,23 and to the effect of the piping system dimensions on multiple injections. 14,24,25 A major branch of the recent research on fuel injection systems is focused on the fluid dynamical interaction between pump dynamics, rail pressure control system action and internal injector transients during both steady-state and unsteady engine working conditions.…”

Piezo-actuated common rail injector structure and efficient design

“…Also the rail pressure can be elevated to very high levels [14] without affecting the hydraulic efficiency of the injection-system. Evidently, the no return-flow also enables the CR high-pressure pump to get minimized and removes the need for a recirculated-fuel cooler [15], in any case for injection systems controlled with fuel metering valve [16].…”