Method and apparatus for increasing the operating efficiency of a liquid-flow machine
BACKGROUND OF THE INVENTION 
     This invention relates in general to a liquid-flow machine. More particularly, this invention relates to a method and apparatus for increasing the operating efficiency of such a machine. 
     To increase the amount of liquid conveyed per unit time in known liquid-flow machines and to improve the efficiency of such machines, i.e., to minimize operating losses, machine contours in contact with the liquid stream have been modified in an attempt to produce flow patterns as free of turbulence within the machines as possible. In addition, the contact surfaces have been ground as smooth as possible for increasing the operating pressure of the machines. A reduction of sound emission through the machine housings to the outside has been effectuated by separate sound insulation. 
     Such measures are not only costly but can be improved by further techniques, if at all, only to a relatively small degree. 
     An object of the present invention is to provide an improved liquid-flow machine. 
     Another, concomitant, object of the present invention is to provide a method and an associated apparatus for increasing the operating efficiency of a liquid-flow machine. 
     Another object of the present invention is to provide such a method and apparatus which achieve better operation without special design measures for all possible kinds and types of liquid-flow machines. 
     Another, more particular, object of the present invention is to provide such a machine, such a method and such an apparatus in which conveyed liquid flow can be increased considerably with reduced driving power. 
     Another particular object of the present invention is to provide such a machine, such a method, and such a apparatus in which an increase in the operating pressure can be achieved while reducing driving power. 
     Yet another particular object of the present invention is to provide such a machine, such a method and such an apparatus wherein sound emission from the liquid-flow machine can be reduced. 
     SUMMARY OF THE INVENTION 
     A method for increasing the operating efficiency of a liquid-flow machine comprises, in accordance with the present invention, the steps of: (a) feeding a working fluid to an input of the machine, (b) adding to the working fluid, at a point upstream of an input, a substantially controlled number of macromolecular bodies acting as friction reducing agents, and (c) operating the machine with the working fluid including the macromolecular bodies. 
     An apparatus for increasing the operating efficiency of a liquid flow machine having an input connected to an inflow line for receiving a working fluid comprises, in accordance with the present invention, a friction reducing device connectable to the inflow line for adding to the working fluid, at a point upstream of the input of the liquid-flow machine, a substantially controlled number of macromolecular bodies acting as friction reducing agents. Advantageously, a sensor or detector is operably couplable to the machine for measuring the rate of flow of the working fluid through the machine. A control unit is operatively connected to the friction reducing device and to the sensor or detector for controlling, in response to the throughput of the working fluid measured by the detector, the rate that the macromolecular bodies are added to the working fluid by the friction reducing device. 
     Accordingly, a liquid-flow machine in accordance with the present invention comprises: (a) a working unit utilizing a working fluid, (b) an inflow line connected to an input of the working unit for delivering the working fluid thereto, and (c) a friction reducing device connected to the inflow line for adding to the working fluid, at a point upstream of the input of the working unit, a substantially controlled number of macromolecular bodies acting as friction reducing agents. The liquid-flow machine advantageously further comprises a detector coupled to the working unit for measuring the rate of flow of the working fluid through the machine and a control unit operatively connected to the friction reducing device and to the detector for controlling, in response to the throughput of the working fluid measured by the detector, the rate that the macromolecular bodies are added to the working fluid by the friction reducing device. 
     The macromolecular substances introduced into the working fluid upstream of the input to the working unit of the liquid-flow machine are advantageously polymers, particularly polyacrylamides, or tensides, or inorganic fibers. The macromolecular bodies can take the form of a powder or a liquid solution. As set forth above, the macromolecular bodies are injected into or added to the flowing working fluid in a quantity matched to the mass throughput of the working liquid, whereby a steady supply of the friction reducing agents or flow accelerators is provided to the working fluid entering the working unit of the liquid-flow machine. 
     The quantity of the friction reducing agents, i.e., the macromolecular bodies, is relatively small in comparison with the quantity of the inflowing working fluid and, accordingly, the consumption of the macromolecular bodies, in a method in accordance with the present invention, is small during operation of the liquid-flow machine. 
     A method in accordance with the present invention is particularly well adapted for liquid-ring machines wherein a vane wheel drives a liquid ring in a housing. In the circulating operation of such machines, working liquid is returned to the machine from a liquid separator disposed downstream of a gas outlet. The amount of liquid required for replacing the lost liquid is small and the amount of friction reducing agent required is even smaller. 
     Tests with a liquid-ring vacuum pump, Siemens type 2BE 1, 2 or 3, have shown that the use of polyacrylamide of different concentrations (50 ppm and 96 ppm) in the working liquid results in an increase in output of approximately 10% or more as a function of the suction pressure, particularly in the operating range of interest. In addition, the power requirements can likewise be lowered by approximately 10% or more, while a greater reduction of sound level can be achieved. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The sole FIGURE of the drawing is a diagram of a liquid-flow machine including an apparatus in accordance with the present invention for increasing the operating efficiency of the liquid-flow machine. 
    
    
     DETAILED DESCRIPTION 
     As illustrated in the drawing, a liquid pump 1 is connected at an input to an inflow line 2 and at an output to a discharge line 3. Working fluid is conveyed to liquid pump 1 via inflow line 2 and flows out from the pump via discharge line 3. To input line 2 is connected a supply tank or reservoir 5 containing a powder or liquid solution of friction reducing agents, preferably organic macromolecular bodies such as polyacrylamides or tensides. 
     A dosing device 4 for controlling the number of friction reducing agents injected or added to the working fluid in inflow line 2 is disposed in a delivery line 8 extending from supply tank 5 to inflow line 2. The rate at which macromolecular bodies are added to the inflowing working fluid in varied by dosing device 4 in response to signals from a sensor or detector 6 disposed in discharge line 3 for measuring the mass throughput of the working fluid through liquid pump 1. Dosing device 4 and detector 6 cooperate to ensure that the friction reducing macromolecular bodies are released into the inflowing working fluid at such a rate that the inflowing fluid has a constant percentage of the macromolecular bodies per unit volume. In this manner, the suction power reduction caused by the temperature rise of the working fluid per se can be more than compensated. 
     Although the invention has been described in terms of particular embodiments and modifications, one of ordinary skill in the art, in light of this teaching, can generate additional embodiments and modifications without departing from the spirit of or exceeding the scope of the claimed invention. Accordingly, it is to be understood that the drawings and descriptions herein are proffered by way of example to facilitate comprehension of the invention and should not be construed to limit the scope thereof.