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  • Technical information

    ABB TurbochargingControlled pulse turbocharging of medium speed 5-cylinder diesel engines

  • 2

    Controlled pulse turbocharging of medium speed 5-cylinder diesel engines E. Codan a,1, I. Vlaskosa, N. Kyrtatos b,2, N. Alexandrakisb

    AbstractThe smoke emissions of turbocharged marine engines can besubstantial under severe transient load-change conditions.This is already causing problems in certain port areas, and itis to be expected that visible smoke will not be tolerated in anumber of coastal regions in the near future. The EU projectSMOKERMEN was therefore set up to study the application oftwo measures for reducing smoke emissions: controlled pulseturbocharging and air injection into the turbochargers com-pressor.

    This paper reports on the design of the two systems that weredeveloped and on the first engine test results, as well as onthe investigated systems potential for reducing smoke emis-sions. The combined effect of the two measures, as well asthe final configuration of the control system, will be studied inthe end phases of the project.

    Key Words: Smoke emissions; pulse turbocharging; jet assist;control system

    Contents

    1 Introduction 3

    2 Test engine 4

    3 Controlled pulse turbocharging 6

    4 Jet assist operation 9

    5 Engine measurements 10

    6 Combination of measures 13

    7 Summary 14

    Bibliography 15

    a ABB Turbo Systems AG, Bruggerstrasse 71a, CH-5401 Baden, Switzerlandb National Technical University of Athens Laboratory of Marine Engineering

    P.O. Box 64033, 157 10 Zografos, Athens Greece1 E-mail: ennio.codan@ch.abb.com, www.abb.com/turbocharging2 E-mail: nkyrt@naval.ntua.gr, www.lme.naval.ntua.gr

    Translation of the paper:Die Aufladung eines mittelschnelllaufenden 5-Zylinder Dieselmotors mit geregelter Stossaufladung. (10th Turbocharging Conference, Dresden, 22 23 September 2005)

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    The development goal of higher power densities for modernlarge diesel engines remains a permanent challenge for theturbocharging system. One possibility to increase the meanpiston speed has so far found little application. Increasingmean pressures and therefore increasing turbocharging pres-sure ratios have therefore still to be confronted.

    At the same time, the Miller process has proved successful asa means of improving engine efficiency while simultaneouslyreducing NOx emissions. An effective Miller process requireseven higher turbocharging pressures, however, with the resultthat single stage turbocharging is pushed to its maximum limits. Two stage turbocharging, which has often been consid-ered as an alternative in the past, has never met with as muchinterest as it does today.

    This development can result in the diesel engine receiving toolittle air from the turbocharging system in both steady-stateand transient part load operation a situation associated withhigher thermal loading and severe smoke emissions.

    It is known that pulse turbocharging, which was patented 80 years ago by A. Bchi (Swiss patent 122664, 1925), canmake a contribution towards improving the problem outlinedabove. The high pressure amplitudes which occur in small volume pipe systems at high turbine mean expansion ratioslead, however, to high dynamic loading of the turbine blades inthe upper power range and unacceptable losses in efficiency.One possibility for extending the application limits of pulse turbocharging is controlled pulse turbocharging [4].

    A further possibility for improving the transient behavior of theturbocharged diesel engine is the injection of compressed airat the compressor wheel of the turbocharger [5].

    The potential of both measures, together with a suitable control strategy, was investigated experimentally in theresearch project SMOKERMEN (SMOKe Emissions Reductionin Marine ENgines). SMOKERMEN is an EU project within the scope of the 5th Framework Programme, and is scheduledto last 42 months. The project partners are: Greek CIMAC Association ABB Turbo Systems AG Woodward Governor Nederland B.V. National Technical University of Athens Laboratory of

    Marine Engineering Germanischer Lloyd AG

    The project is to end this year (2005). Its current status isreported in the following.

    1 Introduction

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    2 Test engine

    The basic data of the test engine in the Laboratory of MarineEngineering at the National Technical University of Athens canbe seen in Table 1.

    Table 1: Main data of 5L16/24 NTUA test bed engine

    Configuration In-line

    Number of cylinders 5

    Power output 500 kW

    Rotational speed 1200 rpm

    Bore 160 mm

    Stroke 240 mm

    Compression ratio 15.5 :1

    Maximum combustion pressure 180 bar

    Mean effective pressure 20.7 bar

    Mean piston speed 9.6 m/s

    Turbocharging System Constant pressure

    Turbocharger ABB TPS 48-EX

    The engine is connected to a 4-quadrant electric brake fromAEG, allowing any desired transient load profiles to be pro-grammed. In its original state, the engine was fitted with aconstant pressure turbocharger combined with jet assist forload acceptance as well as with a conventional controller.

    The reference status of the engine is defined by the fitting ofthe following components. A TPS 48-EX from ABB was used as turbocharger (Fig. 1),

    with the turbine end arranged as standard and with a prototype compressor stage adapted for the engine.

    The engines mechanical governor was replaced by a highlyefficient ATLAS electronic controller from the Woodwardcompany. This controller can be coupled as required to aconventional UG8 actuator (mechanical-hydraulic) or to anall-electronic Pro-Act actuator.

    4.0

    4.4

    4.8

    5.2

    c [-]

    V298 [m3/s]1.2 2.0 2.8 3.6 4.4

    Com

    pre

    ssor

    pre

    ssur

    e ra

    tio

    Volume flow

    F31

    F32

    F33

    TPS

    48-

    TPS

    52-

    TPS

    57-

    TPS

    61-

    TPS . .-E

    TPS . .-D

    Fig. 1a: Operating range of TPS. . -D/E/F [1, 2]. Fig. 1b: Cross sectional view of TPS. . -F [2].

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    The measuring method was adapted to the requirements ofthe project. The AVL INDISET system is used to record andevaluate the data. A torque measuring system from the Manner company permits periodic recording of the enginetorque.

    Germanischer Lloyd is responsible for measuring the emis-sions. The following components were measured: NOx, HC,CO, opacity in transient engine operation, and additionally theparticle emissions in quasi-steady-state operation.

    The main engine power and emissions were measured onthree different ships (Fig. 2) in order to characterize typical collective loadings and emission spectra for marine engines.Operation of the auxiliary generators was also included in themeasurements on two of the ships. Representative operatingconditions were defined on the basis of these measurements(Fig. 3), which were later tested on the test bed.

    Power

    NOx D

    CO D

    Opacity

    HC W

    0

    10000

    20000

    30000

    40000

    0

    1.0

    2.0

    3.0

    4.0

    10:01 10:59 11:57 12:54 13:52 14:49 15:47

    Pow

    er [k

    W],

    NO

    x [p

    pm

    /10]

    , H

    C [p

    pm

    ]

    Op

    acity

    [%];

    CO

    [pp

    m*1

    00]

    Time

    Fig. 3: Example of dynamic measurement on a container ship.

    Fig. 2: Ships for the load profiles and emission measurements by GL.

    CMV Tokyo Express, main engine, 2002-12-27 2003-12-28

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    3 Controlled pulse turbocharging

    Modifications to the pipe system and turbine stage are neces-sary to provide controlled pulse turbocharging of the engine.These are described below.

    3.1 Exhaust gas pipe systemBefore describing the detailed layout of the pulse pipe system,it is useful to provide a brief survey of the basic principles ofpulse turbocharging.

    Pulse turbocharging in scavenged engines requires cylindergroups in which the individual cylinders do not mutually interfere during scavenging. It is known from experience thatdisturbances may not be expected if the firing interval between two cylinders in the same group satisfies the follow-ing conditions: 120 KW or 240 KW

    3-pulse turbocharging satisfies the conditions and providesthe best compromise between pulse effect at part load andacceptable loss of efficiency at high engine power.

    Groups of four cylinders are highly problematic for pulse turbocharging, with the result that various types of pulseconverter have been developed. 2-pulse turbocharging satis-fies the conditions described above and has a very goodpulse effect at part load. The highly irregular turbine admissionleads to a relatively high loss of efficiency in the upper loadrange.

    Large engines rarely have 5 cylinders, one reason being thatthe turbocharging is problematic. The firing interval 144 CAdoes not satisfy the above conditions. An undivided systemcan be considere

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