ISO 20155:2017 船舶および海洋技術—船舶用ポンプの流れに起因するパイプ内騒音源特性の試験方法 | ページ 2

Foreword

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This document was prepared by Technical Committee ISO/TC 8, Ships and marine technology, Subcommittee SC 8, Ship design.

Introduction

In hydraulic fluid power systems of ships, power is transmitted through a liquid under pressure. Pumps are components that convert rotary mechanical power into hydraulic fluid power. During the process of converting mechanical power into hydraulic power, flow and pressure fluctuations and structure-borne vibrations are generated. These fluid-borne and structure-borne vibrations, which are generated primarily by the unsteady flow produced by the pump, are transmitted through the connected piping system.

The fluid-borne vibration generated by a pump is called pressure ripple or flow induced noise. For pumps used for coolant and drainage in ships, flow induced noise can be transmitted along the piping and radiated into the surrounding water area through a pipe mouth outboard the ship, which produces noise pollution and disturbs the environment including marine mammals.

The level of flow induced noise for a pump depends upon not only the characteristics of the pump itself, but also the circuit in which the pump is installed. Thus, the determination of flow induced noise by a pump is complicated by the interaction between the pump and the circuit. The directly measured data using hydrophones inserted in pipe reaches connecting the pump cannot reflect noise source characteristics of the pump. The method adopted to measure the flow induced noise of a pump should be such as to eliminate the interaction.

ISO 10767-1 and ISO 10767-2 provide the test methods for the positive displacement pump with the precision and simplified method, respectively, where the pump is treated as a single port acoustic source and its source characteristics expressed by two parameters of source strength as well as source impedance can be obtained. For other common pumps with two ports, the sound field between the inlet and outlet of a pump is inter-coupling, source characteristics cannot be fully expressed by two parameters, but expressed by up to six parameters, i.e. source pressures at the inlet and outlet of a pump and four elements in a 2 × 2 impedance matrix. There is a need to establish a new standard about a test method for noise source characteristics of a pump, based on two-port acoustic source model.

The source characteristics of flow induced noise are used for evaluating the hydrodynamic noise feature of the pump. The measured results can be compared for pumps of different types and manufacture. This will enable the pump designer to evaluate the effects of design modifications and help hydraulic system designers to avoid selecting pumps having high noise levels.

The method is based upon the application of plane wave transmission line theory to the analysis of noise propagation in hydraulic systems. By adopting a two-port model with noise source and evaluating the impedance characteristics of the pump using a secondary-source method, it is possible to obtain the source strength of the pump, independent of the circuit that the pump locates.

1 Scope

This document specifies a test method for determining flow induced in-pipe noise source characteristics of a ship-used pump as a two-port sound source in laboratory conditions by measuring acoustic pressures in the pipe reaches of inlet and outlet.

The test method is applicable to all types of centrifugal pumps with a diameter over 50 mm operating under steady conditions.

The suitable frequency range of the test method is about 10 Hz to 1 000 Hz, and the upper frequency is dependent on the inner diameter of the pipe, in which the plane acoustic wave propagates.

2 Normative references

The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

3 Terms and definitions

For the purposes of this document, the following terms and definitions apply.

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Bibliography