PERFORMANCE CRITERIA OF 

 PULSE-JET PROPELLERS 



Michael Schmiechen 



Versuchsanstalt fur Wasserbau und Schiffbau 

 Berlin, Germany 



ABSTRACT -'-^ : -:.•••!- ^^ v. . 



Starting from the fundamental concepts and principles of hydrodynamics 

 component efficiencies of pulse-jet propellers are defined, which may 

 be directly compared for various propulsion devices. Some of the 

 problems encountered in the evaluation of the criteria defined are dis- 

 cussed and the problem of propeller-hull-interaction is treated as far 

 as possible. .- • . , . 



1. INTRODUCTION 



With the recent interest in jet propulsion of ships, the lack of clear-cut 

 concepts and generally adopted procedures to define and evaluate performance 

 criteria of propulsion devices has often been felt; Brandau, 1967. The concep- 

 tual and experimental difficulties to overcome this situation are considerable 

 not only in the field of conventional and pump-jet propulsion, but even more in 

 the field of pulse-jet propulsion. 



Due to his engagement in various projects concerning pulse-jet propellers 

 at the Berlin Towing Tank, the author had the opportunity to tackle the problems 

 encountered in performance evaluation from different points of view. Some of 

 the ideas and procedures that have evolved from this work and may be useful in 

 a wider range of applications will be presented here in a systematic account. 



In fact, the aim of the present paper is to reconstruct some well-known 

 concepts of the theory of propulsion, to the effect that they may be applied to any 

 type of propulsion device. For this reason the model considered and the con- 

 cept formulation will be as general as necessary right from the beginning. 

 Starting with the extremely specialized model of the actuator disk would, in this 

 context, not be adequate. Although periodically acting propellers will be consid- 

 ered in general the case of steadily acting propellers will be included as a limit- 

 ing case. 



The method of presentation adopted will be axiomatic, but the exposition 

 will not be formalized. The main interest rests on the logical consequences of 

 the principles and the link-up of the various concepts introduced, the knowledge 

 of which should be the basis of any discussion and work in the field. Though 

 there is a strong demand for orientation towards easily measurable integral 

 magnitudes as far as the evaluation is concerned, this cannot be the only guideline 



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