"INTRODUCTION This Item is concerned with the design and performance of ejectors and jet pumps. Such devices are characterised by the use of the kinetic energy of one fluid stream (the primary flow) to drive a second fluid stream (the secondary flow) by direct mixing. The fluids may be gases or liquids and the secondary stream is not necessarily the same fluid as the primary. For some applications the secondary stream@ and the primary stream also@ may contain solid particles. The design parameters@ requirements and methods vary considerably@ depending on whether the working fluids are gases@ liquids@ solids-in-fluids or combinations of these@ and each type is therefore considered in a separate Data Item. The terms ""ejector"" and ""jet pump"" are alternative names for the same device and the term ""injector"" is also used. Purpose and Scope of this Item This Data Item provides information for design and performance evaluation of ejectors and jet pumps in which both working fluids are liquids. A technique for the optimum design of a jet pump or ejector is presented; the method is based on the equations of continuity and momentum conservation and includes empirical coefficients that allow for losses in the different components. The performance of an ejector or jet pump of given dimensions may be determined from an appropriate performance characteristic curve@ which fully describes the operation of the device. A comprehensive series of such curves is presented@ based on a large number of empirical and analytical data. Layout of this Item Section 3 of this Item discusses briefly some applications of ejectors and jet pumps. Section 4 describes the principles of ejector operation and defines the different components. These may vary considerably with application and Section 4 considers some of the possible configurations. Section 5 describes a design method which will determine the on-design operating conditions and optimum dimensions for an ejector or jet pump when the primary and secondary working fluids are both liquids. The method is suitable for primary and secondary fluids of equal or differing densities. Mechanical design aspects are considered in Section 5.5. Section 6 describes a method by which the performance of an existing ejector or jet pump may be evaluated. Performance charts are presented for the case when the working fluids are of equal density together with corrections allowing for differing densities. Section 7 describes@ briefly@ more complicated ejector designs@ such as multi-nozzle or annular ejectors or multi-stage configurations@ and considers their advantages in certain situations. Section 8 discusses the problem of cavitation and includes a definition for cavitation index. The index characterises the conditions under which cavitation occurs and may be used to predict the onset of this phenomenon. Methods for improving cavitation performance are also described. Section 9 presents worked examples showing the application of both the design and the performance prediction methods. Section 10 lists all the sources of information used in compiling this Data Item and includes further sources of reference which may be helpful to the engineer. Appendix A contains a glossary of terms used in describing jet pump components@ design parameters and performance. Appendix B presents a detailed theoretical analysis of the flow through an ejector@ based on one-dimensional flow representations of mass and momentum conservation@ and includes the development of equations used to describe efficiency and the onset of cavitation. Appendix C presents flow charts outlining the design and performance prediction procedures."
ESDU 85032-1985 history
1985ESDU 85032-1985 EJECTORS AND JET PUMPS - DESIGN AND PERFORMANCE FOR INCOMPRESSIBLE LIQUID FLOW