Determination of Tool Profile for the Milling of Three Screw Pump Rotor

partially_open2The rotors of three screw pumps are commonly machined using shaped milling cutters. The determination of the exact shape of the cutter is very important, since a high precision in the machining is required to obtain a high volumetric efficiency of the pump. This paper describes a method to determine the theoretical shape of the cutter, starting from the characteristic parameters of the pump. The rotors are modeled in space by helicoids. Then, the contact line between the tool and the workpiece is determined and this allows us to define the exact cutter profile, with a suitable reference system transformation.MIMMI G.; PENNACCHI P.Mimmi, Giovanni; Pennacchi, PAOLO EMILIO LINO MARI

DETC2006-99487 ON DESIGN AND PERFORMANCE OF INTERNAL EPITROCHOIDAL PUMPS

ABSTRACT In this study an analysis of rotor profiles geometry in internal epitrochoidal pumps and a systematic study of their performance as a function of the geometrical parameters are introduced. Internal pumps are used in various fields, like automotive, alimentary, or medical-scientific. This machines consist of two rotors: generally the inner rotor has epitrochoidal profile and the profile of the outer rotor is determined as conjugate to the inner one. The rotor geometry and the final performance of the whole machine has been studied by many researchers, using different methods. In this paper the construction of the profiles is performed by the theory of gearing, in order to calculate performance indexes. In particular the pump type with epitrochoidal outer rotor has been considered. Even if it is impossible to establish an optimal profile valid for every application, the analysis of the results obtained allows to choose the design parameters, in order to optimize the shape of the rotors for any particular application. INTRODUCTION Internal lobe pumps, usually called gerotors, have been widely studied in the last decades. These machines are constituted by a cylindrical housing and two rotors rotating at different angular velocities with a fixed ratio. The inner rotor transmits the motion to the outer one by a number of contact points equal to the number of lobes of the inner rotor plus one. The chambers in which the fluid is elaborated are enclosed by the same contact points, so that their volume varies during rotary motion. In order to separate the high and low pressure zones, a common solution consists in realizing suitable inlet and discharge ports in the housing plates (se

Diaphragm design improvement for a metering pump

Since the membrane has to separate the process fluid from the oil circuit in metering diaphragm pumps, it is the critical component of these machines. Sometimes, depending on the operating conditions, the membrane may crack and it is necessary to disassemble the pump and replace this component part. Therefore it is important to improve the design of the membrane to avoid this. In this paper, the behaviour of a membrane mounted in a metering diaphragm pump has been simulated by using f.e.m. An accurate analysis of the results has allowed the membrane to be redesigned in a more rational way and to improve its performance

Experimental analysis of paddling efficiency of elite and non-elite athletes with instrumented canoe sprint C1

Canoeing is an on-water sport admitted by the International Canoe Federation (ICF) and Canoe Sprint became an Olympic discipline in 1936: its programme includes events over 200 m, 500 m and 1000 m. There are numerous Canoe events in single (C1), double (C2) and four (C4) boats. In this discipline the canoeist is kneeling on one knee, and uses a single-bladed flat paddle. In the same way as kayaking, canoeing is a sport whereby propulsion of the boat is derived mainly from muscle actions of the upper body. Conversely, the kneeling position of the canoeist influences the dynamic behaviour of the hull and the force stroke exerted by the single-bladed paddle results in augmented ‘fluctuation’ of the average speed, in greater roll angle and wider pitch span of the canoe with respect to the kayak boat. Besides, the flat shape of the paddle determines the particular paddling technique. In canoeing high forces must be applied at high stroke rates and athletes are coached both in stroke technique and power or resistance training. Elite athletes stand out for the style and efficiency of the stroke, for power and resistance and for skills in the race strategy. Biomechanical measures of canoeing is an important asset to improve performance. In addition comparing results from test to test enables monitoring of an athlete's yearly, and year-to-year improvement. Finally, the experimental analysis of the main kinematical and dynamical parameters allows to examine the shape of the force curves for stroke error detection purposes and to reduce the ineffective hull movements. In this paper the performance and the paddling technique of two elite and two non-elite canoeists are presented by means of an on-water experimental apparatus. Moreover a comparison between the drive phase of the stroke in kayaking and canoeing is proposed. The goals of this research project were to (1) develop a system for on-the-water measurement of paddling performance in kayaking and canoeing, (2) demonstrate the potential of such a system to quantify efficiency and then (3) compare the main kinematical and dynamical parameters of single K1 and C1 boats and the technique differences in paddling style

Computation of Pressure Loads in Three Screw Pump Rotors

In the present paper the loads, usually modeled as a force and a moment, on the rotors of a three screw pump have been analyzed. These loads, due to the pressure of the working fluid, are periodical, so their actions on the rotors vary. The calculations of the loads are possible thanks to the exact mathematical model of the sectors of surface of the rotors where the pressure works. The computation of the loads is determined as a function of the rotation angle and it is useful for the comprehension of some phenomena, such as the vibration induced and the noise generation, and for the design of a possible balancing system of the rotor loads. On the basis of the results of the calculations described, we can obtain the different types of actions on the rotors. The central screw presents loads different from those of the two satellite screws. In particular we show how the loads depend on the design parameters, especially on the pitch. The criteria for the optimum design of this parameter are indicated in detail

Diaphragm design improvement for a metering pump

Since the membrane has to separate the process fluid from the oil circuit in metering diaphragm pumps, it is the critical component of these machines. Sometimes, depending on the operating conditions, the membrane may crack and it is necessary to disassemble the pump and replace this component part. Therefore it is important to improve the design of the membrane to avoid this. In this paper, the behaviour of a membrane mounted in a metering diaphragm pump has been simulated by using FEM. An accurate analysis of the results has allowed the membrane to be redesigned in a more rational way to improve its performance

Computation of Pressure Loads in Three Screw Pump Rotors

In the present paper the loads, usually modeled as a force and a moment, on the rotors of a three screw pump have been analyzed. These loads, due to the pressure of the working fluid, are periodical, so their actions on the rotors vary. The calculations of the loads are possible thanks to the exact mathematical model of the sectors of surface of the rotors where the pressure works. The computation of the loads is determined as a function of the rotation angle and it is useful for the comprehension of some phenomena, such as the vibration induced and the noise generation, and for the design of a possible balancing system of the rotor loads. On the basis of the results of the calculations described, we can obtain the different types of actions on the rotors. The central screw presents loads different from those of the two satellite screws. In particular we show how the loads depend on the design parameters, especially on the pitch. The criteria for the optimum design of this parameter are indicated in detail