07.optimizing combustion in an single cylinder gdi si engine

8/17/2019 07.Optimizing Combustion in an Single Cylinder GDI SI Engine

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Optimizing Combustion in an SingleCylinder GDI SI Engine

Stelian Tarulescu, Radu Tarulescu and Cristian-Ioan Leahu

Abstract Throughout the world, many efforts are being made to improve the

thermal ef ciency of automotive internal combustion engines (Sellnau et al. in

GDCI multi-cylinder engine for high fuel ef ciency and low emissions 2015). Inthis paper, the AVL 475 cc GDI Single Cylinder Research Engine 5405 was tested

over a range of steady-state operating conditions using a modern injection system.

Calibration mapping was conducted over a wide range of operating conditions, in

order to optimize the combustion. The tests was made at Transilvania University of

Braşov, ICDT — Research & Development Institute. This tests include simulations

for different engine loads and regimes, modifying one by one the engine’s intake

parameters, operational parameters and atmospheric conditions. The mixture for-

mation and combustion processes of the fuel will be monitored through the test bed

component software, AVL FIRE Commander 7.06c —

IAV, AVL PUMA Open Test Bed Automation and AVL Indicom software. In order to optimize the combustion,

the engine map was modied. The main parameters that was changed are: the

amount of fuel per cycle, ignition timing for rst and second injection, excess air

factor λ , for different intake pressures, engine speeds and loads. In the next gure is

presented the engine map for the analyzed engine.

Keywords Combustion Optimize Engine Gasoline

S. Tarulescu (&) R. Tarulescu C.-I. Leahu

Transilvania University of Brasov, Eroilor Boulevard, 29, 500036 Brasov, Romania

e-mail: [email protected]

R. Tarulescu


C.-I. Leahu


© Springer International Publishing Switzerland 2016

C. Andreescu and A. Clenci (eds.), Proceedings of the European Automotive

Congress EAEC-ESFA 2015, DOI 10.1007/978-3-319-27276-4_37

395


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Introduction

The new Euro 6 regulations regarding CO2 emissions and regulated emissions

including NOx

, CO, HC, and particulate matter (PM) are demanding advancedinternal combustion engines with greatly improved combustion processes. While

diesel engines are already very ef cient, they are challenged to meet future emis-

sions standards at reasonable cost. Gasoline engines are preferred by customers, but

the ef ciency of gasoline engines is relatively low (Ghadikolaei 2014).

Gasoline Direct Injection (GDI) is an increasingly popular type of fuel injection

system employed in modern four-stroke gasoline engines. The gasoline is highly

pressurized, and injected by high voltage driven injectors via a common rail fuel line

directly into the combustion chamber of each cylinder, as opposed to conventional

single or multi-point fuel injection that happens in the intake manifold tract, or

cylinder port. The major advantages of a GDI engine are lower emission levels,

increased fuel ef ciency and higher engine power output. In addition, the cooling

effect of the injected fuel and the more evenly dispersed combustion mixtures and

temperatures allow for improved ignition timing settings which are an equally

important system requirement. Emissions levels can be more accurately controlled

with the GDI system. The lower levels are achieved by the precise control over the

amount of fuel, air and ignition settings which are varied according to the engine load

conditions and ambient air temperature (Gajbhiye and Chincholkar 2013).

In order to obtain data and optimize solutions for GDI engines, a research

program was developed at Transilvania University of Braşov, ICDT — Research &Development Institute. The research stand is an AVL single cylinder test bed for

gasoline and diesel engines (Fig. 1). For the present paper, the tests was made on a

AVL 475 cc GDI Single Cylinder Research Engine 5405. The single cylinder can

be setup in several congurations (with multipoint injection, with direct injection,

with turbocharger). There will be tested the fuel mixture formation combustion

process and the influence of turbocharged engine. The engine with transparent

quartz cylinder is built for the visualization of internal processes from outside using

a high speed movie camera. The piston with quartz head allows lming the internal

processes with the help of a system of mirrors. The mixture formation and com-bustion processes of the fuel will be monitored through the test bed component

software, AVL FIRE Commander 7.06c — IAV (AVL 2013).

Methodology

In the present study ware made tests in order to improve the combustion for one

research engine. The results can be used to improve the processes of GDI gasolineengines in order to reduce the exhaust emissions and fuel consumption (Verlag 2014).

Single Cylinder Research Engine 5405 specications are: Bore: 82 mm; Stroke:

90 mm; Displacement: 475 ccm; Max. speed: 6000 rpm; Rated power: 20 kW

396 S. Tarulescu et al.


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natural aspirated; Rotation inertia approx. 0,4 kgm2; Combustion concept:

Homogeneous, λ = 1; Compression ratio: 11.5:1.

The test bed have some other components and systems: Balancer System for SCRE; MPFI Conversion Kit, Conversion kit for AVL Gasoline Direct

Injection SCRE from GDI to Multi Point Fuel Injection (MPFI) operation;

Conversion Kit: Optical Topworks 514 Gasoline GDI; Mirror Unit for Optical

Measurements; AVL Engine Control Unit (AVL ETU 427); Coolant and condi-

tioning Unit 577; AVL Fuel mass flow meter — Type Flex Fuel; AVL Fuel tem-

perature control; Intake Air Consumption Measurement Device; Particle Evaluation

— Micro Soot Sensor Continuous Measurement of Soot Concentration; AVL

PUMA Open Test bed Automation; Exhaust Gas analyzer, Model GA-21plus (AVL

2013).The used software used for intake and combustion process optimization is AVL

FI2RE Commander 7.06c — IAV. AVL FIRE was developed to solve the most

demanding flow problems in respect to geometric complexity and chemical and

physical modeling. FIRE offers a comprehensive computational fluid dynamics

solution: a powerful set of modules, features and capabilities, pre-and

post-processing integrated in a common environment and workflows and meth-

ods effectively supporting the use of the software to solve any problem accurately

(AVL 2013).

The software used for engine parameters monitoring is AVL Indicom software.

During cycle based data acquisition the value of cycle time must vary all the time.

For combustion tests several parameters will be monitored: engine speed, intake

fuel pressure, cylinder maximum pressure, intake air pressure, spark ignition time,

Fig. 1 AVL single-cylinder compact test bed used for GDI research

Optimizing Combustion in an Single Cylinder GDI SI Engine 397


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injection start moment, injection time, rail pressure, exhaust temperature and

mixture ratio (Excess Air — λ ). They are presented in the Table 1.

The rst set of tests was made using a standard engine map (in AVL FI2RE). For

following tests the spark ignition time and air excess coef cient ware optimized.

The tests was made for different engine loads and engine speeds. Also, one set of

tests was made for one direct injection per cycle and other set of tests was made for

two injections per cycle (First DI injection and Second DI injection). The setup was

made in AVL FI2RE software as is showed in Fig. 2 (AVL 2013).

In Fig. 3 is presented the main menu used for intake and combustion

parameters optimization. The engine load is controlled through manifold

Table 1 Engine parameters

SPEED

(rpm)

IMEP

(bar)

PMAX

(bar)

AI

50 %

(°CA)

P

Intake

(mbar)

SA

(°CA)

SOI

(CA)

DOI

(ms)

P

RAIL

(bar)

T

EXH

(°C)

Lambda

(–)

1000 3.00 17.40 25.00 −

303.5 −

20 −

280 1850 100 240 1.00

Fig. 2 AVL FI2RE working sheet — number of injections/cycle and duration of injection

Fig. 3 AVL FI2RE menu — engine map parameters



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pressure. The engine speed is set using the main control system (AVL Puma

interface). The intake parameters are controlled by set the number of injections

(rst, second or third direct injection and one indirect injection). The fuel

mixture can be adjusted by varying the amount of fuel injected per cycle (in-

jection period — (μs)). The ignition time is also set in crank angle degrees beforetop dead center.

The parameters changes were made to obtain an optimal single cylinder pressure

curve and more optimal combustion (no detonations). In the Fig. 4 are presented the

intake, ignition and combustion features for 475 cc GDI Single Cylinder Research

Engine.

Tests were done for one specic engine speed and one engine load by modifying

the following parameters: number of injections, amount of fuel injected per cycle

and ignition time (spark moment) before top dead center (TDC).

In order to control the quality of the combustion and exhaust emission level it was used exhaust gas analyzer, Model GA-21plus. For each test (in order to

optimize intake and combustion parameters) were recorded values of the main

pollutants (as seen in the example working page in Fig. 5) (GA-21 plus 2013).

Fig. 4 Engine parameters monitoring with AVL Indicom software



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Results

In order to achieve an engine map for optimal functioning ware tested several

values for the ignition moment (crank angle) and the amount of fuel injected per

cycle. Tests were made for a big range of engine speeds and throttle positions

(engine loads). For example we chose a set of tests made under the following

conditions: engine speed *2000 rpm; manifold pressure *500 mbar; sparkmoment before TDC: −18 → −26 °CA; injection period: 900 → 1300 μs; intake

with one injection or two injections per engine cycle.

For each test, there were measured the emissions to determine optimum com-

bustion and pollution level. The results are presented in Figs. 6, 7, 8, 9, 10 and 11.

The lowest levels of CO2 were recorded for the values of the spark advance

angle before TDC of 20 to 22 °CA, when the duration of injection was selected

1200 μs. Also, for a selected value of 22 °CA, when injection time/engine cycle is

variable, the lowest value of CO2 is registered for 1100 μs.

Fig. 5 Interface for exhaust gas analyzer model GA-21plus — parameters

CO2 level for one injection/cycle

17,2

16,8

15,7

16

16,2

15,6

15,8

16

16,2

16,4

16,6

16,8

17

17,2

17,4

C O 2 [ % ]

CO2 level for two injections/cycle

16,2

15,8

15,9

16,3

16,4

15,7

15,8

15,9

16

16,1

16,2

16,3

16,4

16,5

C O 2 [ % ]

Fig. 6 Variation of CO2 with spark advance to TDC for one and two injections/cycle



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The lowest values of CO were recorded for 22 °Crk, when the duration of

injection was selected 1200 μs. Also, for a selected value of 22 °Crk, when injection

time/engine cycle is variable, the lowest value of CO is registered for 1100 and

1200 μs.

The lowest values of NOx were recorded for 24 and 26 °Crk, when the duration

of injection was selected 1200 μs. Also, for a selected value of 22 °Crk, when

injection time/engine cycle is variable, the lowest value of CO is registered for 900

and 1100 μs.

CO2 level for one injection/cycle

16,9

16

15,4

15,7

16

15,2

15,4

15,6

15,816

16,2

16,4

16,6

16,8

17

Duration of injection [µs]

C O 2

[ % ]

CO2 level for two injections/cycle

16 16

15,8

15,9

16

15,75

15,8

15,85

15,9

15,95

16

16,05


C O 2 [ % ]

Fig. 7 Variation of CO2 with duration of injection/cycle for one and two injections/cycle

CO level for one injection/cycle

31

20

18

26

29

15

20

25

30

35

C O [ p p m ]

CO level for two injections/cycle

25

21

15

18

23

15

20

25

30

35

C O [ p p m ]

Fig. 8 Variation of CO with spark advance to TDC for one and two injections/cycle

CO level for one injection/cycle

43

21 2018

31

15

20

25

30

35

40

45


C O [ p p m ]

CO level for two injections/cycle

32

18

14 15

22

10

15

20

25

30

35

40


C O [ p p m ]

Fig. 9 Variation of CO with duration of injection/cycle for one and two injections/cycle



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It can be concluded that for optimum combustion and reduced emission values at

exhaust pipe will choose the spark advance angles of 20 to 22 °Crk and injection

times per cycle of 1100–1200 μs. Also, an intake with two injections per cycle, one

pilot and a main injection would be the best solution for optimum performance.

In order to achieve a complete map of the engine, will optimize intake and

combustion parameters for as many speeds and engine loads as possible.

Conclusions

Using the previous researches and extensive simulation work, a vast set of tests was

made on an experimental single cylinder engine with gasoline direct injection

(GDI). Central to these tests was a fuel injection system and injection strategy

combined with engine parameters optimization. This produced robust ignition with

very clean, ef cient, and stable combustion.

In order to achieve an engine map for optimal functioning ware tested several

values for the ignition timings and the amount of fuel injected per cycle. Tests were

NOx level for one injection/cycle

4 4

3

1 1

0

1

2

3

4

5

N O x

[ p p m ]

NOx level for two injections/cycle

2 2 2

1 1

0

1

2

3

4

5

18 20 22 24 26

N O

x [ p p m ]

Fig. 10 Variation of NOx with spark advance to TDC for one and two injections/cycle

NOx level for one injection/cycle

1 1

2

3

6

0

1

2

3

4

5

6


N O x [ p p m ]

NOx level for two injections/cycle

1 1 1

2 2

0

1

2

3

4

5


N O x [ p p m ]

Fig. 11 Variation of NOx with duration of injection/cycle for one and two injections/cycle



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made for a big range of engine speeds and loads. For a complete map of the engine,

there will be optimize intake and combustion parameters for as many speeds and

engine loads as possible. An engine map example is presented in Fig. 12.

Acknowledgments We hereby acknowledge the structural founds project PRO-DD (POS-CCE,

O.2.2.1., ID 123, SMIS 2637, ctr. No 11/2009) and Transilvania University of Brasov for pro-

viding the infrastructure used in this work.

References

AVL (2013) Tutorials and books for engines test cell equipments usageFlue Gas Analyser GA-21 plus (2013) Operating manual, Madur electronics. Vienna — Austria

Gajbhiye PK, Chincholkar SP (2003) Review on electronically assisted gasoline direct injection

4-stroke single cylinder engine system. Int J Sci Res (IJSR). India Online ISSN: 2319-7064

Sellnau M, Moore W, Sinnamon J, Hoyer K, Foster M, Husted H (2015) GDCI multi-cylinder

engine for high fuel ef ciency and low emissions. Copyright © 2015 SAE International,

Published 14 Apr 2015

Ghadikolaei MA (2014) History of Gasoline Direct Compression Ignition (GDCI) engine — a

review. IJRET Int J Res Eng Technol 03(01). eISSN: 2319-1163, pISSN: 2321-7308,

Available @ http://www.ijret.org

Verlag Europa-Lehrmittel (2014) Modern automotive technology, 2nd edn. Nourney, Vollmer

GmbH & Co. KG, Germany, ISBN 978-3-8085-2302-5

Fig. 12 Engine mar — intake and combustion parameters


07.optimizing combustion in an single cylinder gdi si engine

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