Page 1 of 6

Journal for Studies in Management and Planning

Available at

http://edupediapublications.org/journals/index.php/JSMaP/

e-ISSN: 2395-0463

Volume 02 Issue 11

November 2016

Available online: http://edupediapublications.org/journals/index.php/JSMaP/ P a g e | 327

Flow and Concentration Variation between the Cylinders of a

Diesel Engine

1K.Sathish, 2 Mr.G.Veerendra Naik

1pg Scholar, Depeartment of Mechanical Engineering, Gandhi Academy of Technical Education-Kodad

2 Assistant Professor, Depeartment of Mechanical Engineering, Gandhi Academy of Technical Education-Kodad

ABSTRACT:

The demands on tomorrows diesel engines

regarding fuel consumption and emission

levels keep getting more difficult to fulfill.

Due to this fact, the control demand is

getting bigger and bigger. To be able to

comply with the Euro 6 standards, it is

believed that engine control need to be

conducted individually from cylinder to

cylinder if the need for after-treatment

systems should be minimized. Scania’s

approach to handle emission levels so far

has been to use exhaust gas recirculation

(EGR). To be able to optimize the use of

EGR it is necessary to know how the inert

gases, water and carbon dioxide, are

distributed between the cylinders. The

distribution variation become even more

difficult to predict since the EGR is cooled,

sometimes leading to condensation of some

of the water content. The condensation of

water and its behavior in the inlet manifold

is studied in this thesis. Different ways of

measuring non-uniformity in the gas

composition between cylinders with respect

to EGR in general and water content in

particular are evaluated. Using these

results, measurements have been conducted

on an engine and conclusions are drawn

from them. The conclusions are that uneven

distribution of above all liquid water, due to

puddle formation, have an impact on

emission formation that should be accounted

for in some of the examined operating

conditions.

1.INTRODUCTION:

Emission legislations keep getting more and

more stringent. Among the manufacturers of

heavy trucks and buses, there are a few

concepts used generally to reduce the

vehicle out emissions. With the diesel

engine, the combustion is typically

conducted in an environment with an excess

of oxygen. The most difficult emissions to

control in modern diesel engines are

typically NOx and particulates, commonly

abbreviated PM. Several after-treatment

systems exist, the most commonly used are

Page 2 of 6

Journal for Studies in Management and Planning

Available at

http://edupediapublications.org/journals/index.php/JSMaP/

e-ISSN: 2395-0463

Volume 02 Issue 11

November 2016

Available online: http://edupediapublications.org/journals/index.php/JSMaP/ P a g e | 328

selective catalytic reduction - SCR, NOx- adsorber, oxidizing catalysts, and particulate

filters. Scania’s approach, however, is

mainly focused on preventing the emissions

to form already in the combustion chamber.

One issue in the control systems of Scania’s

engines today is that the emission reducing

systems are not controlled for individual

cylinders. To do this, more information

regarding both the amount, as well as the

composition, of the gases that enter each

cylinder is needed. The goal with this thesis

is to evaluate different ways of measuring

gas composition in the inlet manifold on a

cylinder-individual basis. Also covered by

the scope of the thesis is performing

measurements based on the evaluation,

using those measurements to try and

determine the localization and behavior of

liquid water in the inlet manifold. And

looking at the general distribution of EGR

gas between the cylinders.

1.1.The Scania EGR concept

To achieve a reduction of emission

formation inside the combustion chamber,

exhaust gases are used to dilute the charge

air (exhaust gas recirculation, from here on

the acronym “EGR” will be used both for

the gas and for the concept). Because the

exhaust gases are very hot (it’s not

uncommon with temperatures exceeding 500

◦C), they need to be cooled to raise the

density and to prevent heating of the charge

air mixture. The system used on the engine

on which calculations and measurements has

been conducted consists of some different

parts. It utilizes an advanced common-rail

fuel system that is able to deliver fuel at

high pressures, it also incorporates a

variable geometry turbo-charger. For the

EGR, the exhaust gases are sampled just

before the turbine and led past a

proportional valve and on to a cooling

system. After being cooled down, the EGR

and the fresh air are mixed together before

the inlet manifold.

1.1.1 Water condensation

When the EGR is cooled from

approximately 500 ◦C down to temperatures

well below 100 ◦C, water is condensed. This

is believed to occur mainly in the cooling

system. Theoretical calculations based on

CO2 concentrations in the exhaust gas as

well as pressure and temperature after the

cooler gives a picture of at which

operational points condensation should

occur. It is potentially a big problem since

high levels of EGR is used, resulting in high

relative humidity as well as large amounts of

water (several per cents volume part) in the

Page 3 of 6

Journal for Studies in Management and Planning

Available at

http://edupediapublications.org/journals/index.php/JSMaP/

e-ISSN: 2395-0463

Volume 02 Issue 11

November 2016

Available online: http://edupediapublications.org/journals/index.php/JSMaP/ P a g e | 329

intake. While the EGR in gas phase

probably blends quite well with the fresh air

(measurements of CO2 concentration in the

inlet manifold show steady and reliable

values), the liquid water could easily be un- evenly distributed between the cylinders. In

this thesis, there will be attempts to measure

the distribution of both water as well as

carbon dioxide.

1.1.2 The effect of EGR

As mentioned earlier, the biggest challenge

in large diesel engines today is to reduce

particulates and nitrous oxides, and at the

same time maintain the high fuel efficiency.

The reason that EGR is helpful in doing this

is because there is a trade-off between high

efficiency and low NOx formation. This

trade-off is based on combustion

temperature, where a high combustion

temperature will give high efficiency but at

the same time oxidize nitrogen. A high

combustion temperature also helps oxidizing

particulates, therefore introducing another

trade-off between particulates and nitrous

oxides. One solution to this problem is to

use high injection pressures to increase the

length of the fuel-jet before it starts burning,

this is called “lift-off”, thereby increasing

the air-fuel mixing and reducing particulate

formation. At the same time it is possible to

lower the local peak combustion

temperature by diluting the fresh air and

thereby the oxygen, increasing the distance

between the locations where oxidation can

occur. This is done by introducing inert

gases, either by containing burnt gases from

the previous cycle, or by the use of EGR.

The use of inert gases also affect the average

combustion temperature by increasing the

mass in the cylinder. The use of EGR is

currently the main course that Scania has

taken to comply with future legislation

demands.

1.1.3 Importance of uniformity

The NOx formation rate as function of local

temperature is approximately exponential,

and due to the connection between EGR- fraction and combustion temperature it

follows that NOx formation is dependent on

EGR-fraction in an exponential manner.

This is shown by Magnus Andersson in [1]

where he measures NOx output as a function

of inert EGR (EGR / _). A high use of EGR

can affect fuel economy and particulate

formation negatively because it requires a

more workload from the compressor to keep

_ at the same level, thereby increasing the

pumping-work. Therefore it is important not

to use an excessive amount of EGR. If the

inert gases in the EGR is distributed un-