Gerotor

Abstract: Gear pumps represent the majority of the fixed displacement machines used for flow generation in fluid power systems. In this context, the paper presents a review of the different methodologies used in the last years for the simulation of the flow rates generated by gerotor, external gear and crescent pumps. As far as the lumped parameter models are concerned, different ways of selecting the control volumes into which the pump is split are analyzed and the main governing equations are presented. The principles and the applications of distributed models from 1D to 3D are reported. A specific section is dedicated to the methods for the evaluation of the necessary geometric quantities: analytic, numerical and Computer-Aided Design (CAD)-based. The more recent studies taking into account the influence on leakages of the interactions between the fluid and the mechanical parts are explained. Finally the models for the simulation of the fluid aeration are described. The review brings to evidence the increasing effort for improving the simulation models used for the design and the optimization of the gear machines.

Abstract: An engine is disclosed. According to one embodiment of the present invention, the engine comprises a compressor, and combustor, and an expander. The compressor compresses ambient air. The combustor burns the compressed air, and produces exhaust gases. The expander receives the exhaust gases from the combustor, and expands the exhaust gases. The compressor may be a gerotor compressor or a piston compressor having variable-dead-volume control. The expander may be a gerotor expander or a piston expander having variable-dead-volume control. In another embodiment, an engine comprises a piston compressor, a combustor, a piston expander, and a pressure tank. The piston compressor compresses ambient air. The combustor burns the compressed air, and produces exhaust gases. The piston expander receives the exhaust gases from the combustor, and expands the exhaust gases. The pressure tank receives and stores the compressed air from the compressor. In another embodiment, a gerotor compressor or a gerotor expander comprises an inner gerotor, and an outer gerotor. The inner gerotor and the outer gerotor are driven so that they do not touch. The gerotors may be cantilevered or non-cantilevered.

Abstract: The paper presents geometric and kinematic aspects that constitute a premise to the modelling and simulation of gerotor lubricating oil pumps. With reference to a commercial oil pump two different modelling approaches of the pumping elements are addressed: the classical integralderivative approach and the new derivative-integral approach. The latter, based on volumes swept by vector rays, is easier to implement and requires less computer time at equal accuracy. Two approaches to modelling are also detailed that feature different reticulations of the pump and consequently involve a different number of ordinary differential equations (ODE). Depending on the extent and detail of expected informations, either 4 or N+2 ODE must be solved, N being the number of variable volume chambers in the pump. Finally, numerical results of the simulation code, developed in the AMESim environment, have been compared with experimental results presented elsewhere [4].

Abstract: This paper documents an extensive study aimed at a better understanding of the peculiarities and performance of crankshaft mounted gerotor pumps for IC engines lubrication. At different extents, the modelling, simulation and testing of a specific unit are all considered. More emphasis, at the modelling phase, is dedicated to the physical and mathematical description of the flow losses mechanisms; the often intricate aspects of kinematics being deliberately left aside. The pressure relief valve is analysed at a considerable extent as is the modelling of the working fluid, a typically aerated subsystem in such applications. Simulation is grounded on AMESim, a relatively novel tool in the fluid power domain, that proves effective and compliant with user deeds and objectives. Testing, at steady-state conditions, forms the basis for the progressive tuning of the simulation model and provides significant insight into this type of volumetric pump. INTRODUCTION The reduction of development time of new IC engines prototypes is a key issue in providing automotive industries with enhanced competitive strength. To reach this goal a need exists for the assessment of accurate design approaches that will significantly and beneficially impact subsequent testing. Simulation is certainly a major benefit in achieving optimal performance in systems and components being designed. It is the purpose of this paper, in view of the simulation of the complete IC engine lubrication system, to provide an effective mathematical prediction of gerotor lubricating oil pumps. Basically, the unit consists of a pair of gear shaped elements mated so that each tooth of the inner gear is always in sliding contact with the outer gear to form sealed pockets of fluid. Both gears rotate in the same direction at low relative speeds with the inner gear being slightly faster. Fluid enters the chamber with increasing volume, is trapped in the spaces between the teeth and is transported to the outlet. A schematic of the pump core is shown in Fig. 1. The equivalent hydraulic circuit is presented in Fig. 2. Oil is taken in from the tank (oil sump), passes through the inlet duct and is filtered (strainer F1). Delivered flow is further filtered in F2, and, pending on pressure level, excess flow is recirculated to inlet through a pressure limiting valve VL. Downstream of junction G4, port P connects pump delivery to lubricating oil consumers (U). Figure 1: Pump core schematic Figure 2: Equivalent hydraulic circuit