Measurement and simulation of pollutant emissions from marine diesel combustion engine and their reduction by water injection

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Abstract

Taking into account the complexity and cost involved to conduct an experimental investment, the recourse to a tool of simulation, which in turn entails access to information by measurement, offers an effective and fast alternative to deal with the problem of pollutant emissions from internal combustion engines. An analytical model based on detailed chemical kinetics employed to calculate the pollutant emissions of a marine diesel engine gave results, in general, satisfactory compared to experimentally measured results. Especially the NO emission contents are found higher than the standards limiting values set out by the International Maritime Organisation (IMO). Thus, this study is undertaken in order to reduce as much as possible these emissions.

The reduction of pollutant emissions is apprehended with water injection.

Introduction

Energy produced by powerful diesel engines is largely used in marine propulsion, because of their favourable reliability and their significant output. However, the increasingly constraining legislations, aiming to limiting the pollutant emissions from the exhaust gas produced by these engines, tend to perform their supremacy [1], [2].

Many studies were undertaken, on the experimental and analytical level as well, in order to study the mechanisms which govern the generation of the various produced pollutants [3], [4], [5]. The analysis of the pollutant emissions and their reduction in the exhaust gas of the medium speed turbocharged marine diesel engine, constitutes the principal objective of this study.

With advanced research and in spite of the computer’s high capacity, it is still impossible, in combustion, to treat at the same time complex kinetics and industrial turbulent flow conditions. The majority of the studies treated the detailed chemistry of combustion in association with ideal flow reactor conditions [5], [6]. The various simulations carried out in this work are based on the computer code marketed by Reaction Design, the CHEMKIN package, which is developed by the Sandia laboratories.

Comparisons of the numerical predictions with the experimental results carried out on a real unit at use aboard a car ferry ship made it possible to analyze the validity of the numerical results.

Section snippets

Experimental study

The unit selected for measurements is a power generating unit in operating on a car ferry ship during its docking in the harbour. The diesel engine unit is a WARTSILA NSD type 6R32 LNE having characteristic given in Table 1 with a nominal power of 2460 kW. The measured values taken in exhaust gas were carried out using a Testo350 (Precision ±5% m.v.) gas analyzer which made it possible to timely record with accuracy the % O2, % CO2, NO, SO2, temperature and pressure.

The measurements were carried

Numerical study

It is often difficult to carry out a straight away parametric study on an real unit since the combustion study is generally complex with simultaneous presence of several physical and chemical phenomena which vary from a model to another according to the aero thermo chemical conditions of the application. For that, it is necessary to be able mathematically to describe the aero thermo chemical phenomena which controls the various processes present in a real combustion chamber.

In spite of the great

Study of water injection

Therefore a subsequent study has been done to reduce this NO emission [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19] by water injection (Fig. 7). The objective of this study is to analyze the influence of water injection [17], [18] in the combustion chamber of the diesel engine on the different pollutant emissions.

In order to study the influence of water injection we choose the case of the power of 1470 kW related to admission air having a temperature of Tadm =

Conclusion

To address problems of global air pollution due to the pollutant emission from fuel oil engine combustion, it is necessary to understand the mechanisms by which pollutants are produced in combustion processes. In the present work, an experimental and numerical study is carried out on a unit being actually used aboard a car ferry ship. A numerical model based on a detailed chemical kinetics scheme is used to calculate the emissions of CO2, NO and SO2 in an internal combustion engine model having

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