INVESTIGATION OF CYLINDER PRESSURE FOR H 2 /CH 4 MİXTURES AT DIFFERENT LOAD

Bilge Albayrak Çeper, S.Orhan Akansu, Nafiz Kahraman

INVESTIGATION OF CYLINDER PRESSURE FOR H2/CH4 MİXTURES AT

DIFFERENT LOAD

Dept. of Mechanical Engineering, Erciyes University Engineering Faculty, Kayseri, Turkiye

International Conference on Automotive Technologies November 13 – 14, 2008

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ABSTRACT In this study, an experimental study on the performance and

exhaust emissions of a spark ignition engine fuelled with methane-hydrogen mixtures (100%CH4, 10%H2-90%CH4, 20%H2-80%CH4, and 30%H2-70%CH4) were performed at full load and 65% full load for different excessive air ratio. This present work was carried out on a Ford engine. This is a four-stroke cycle four-cylinder spark ignition engine with a bore x stroke of 80.6x88 mm and a compression ratio of 10:1. Experiments were made on a constant engine speed of 2000 rpm. CO, CO2 and HC emission values and cylinder pressures were measured. The results showed that while the excessive air ratio increase, CO and CO2 emission values decrease.


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Why Natural gas –Hydrogen mixtures ? The energy system today is dominated by fossil fuels, which

are abundant and relatively inexpensive. Burning of the fossil fuels generates waste materials, mainly emissions to the atmosphere in the form of combustion fuel gases and dust, as well as some ash and/or clinker. These waste materials have hazardous effects on the environment, some of them locally, others with more widespread or even global impact. Natural gas (NG) is an extremely important source of energy for reducing pollution and maintaining a clean and healthy environment. In addition to being a domestically abundant and secure source of energy, the use of NG also offers a number of environmental benefits over other sources of energy, particularly other fossil fuels. Natural gas is composed primarily of methane which dominates its emission characteristics. Methane mixes readily with air and has a high octane rating which makes it a very good spark-ignition engine fuel.


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Traditionally, to improve the lean-burn capability and flame burning velocity of the natural gas engine under lean-burn conditions, an increase in flow intensity in cylinder is introduced, and this measure always increases the heat loss to the cylinder wall and increases the combustion temperature as well as the NOx emission. One effective method to solve the problem of slow burning velocity of natural gas is to mix the natural gas with the fuel that possesses fast burning velocity. Hydrogen is regarded as the best gaseous candidate for natural gas due to its very fast burning velocity, and this combination is expected to improve the lean-burn characteristics and decrease engine emissions.

Why Natural gas –Hydrogen mixtures ?


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The volumetric heat value of natural gas–hydrogen mixtures will decrease with the increase of hydrogen fraction in fuel blends, and this is due to the low volumetric heat value of hydrogen–air mixture compared to that of natural gas–air mixture at the stoichiometric condition.


Why Natural gas –Hydrogen mixtures ?

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Experimental apparatus and test procedure Table 1. General specifications of the Ford engine

The general specifications of the engine are shown in Table 1. A Cussons-P8601 brand hydrokinetic dynamometer was used for the tests. The schematic view of the test equipments is shown in Fig. 1

Bore 80.6 mm

Stroke 88 mm

Compression Ratio 10:1 -

Exhaust valve opening 55 BBDC

Exhaust valve closing 50 ATDC

Intake valve opening 13 BTDC

Intake valve closing 47 ABDC

1500 rpm spark timing 18 BTDC




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1-Engine Chassis, 2- Hydrokinetic Dynamometer, 3- Engine, 4- Engine Cooling Unit, 5-Air Tank, 6- Control Unit, 7- Main Fuel Tank, 8- Regulator, 9- Fuel Select Key, 10-Fuel Tank, 11-Mass Flow meter, 12- Exhaust Gas Analyzer

Figure 1. Experimental rig

3 2

5

7 10

812 6

4

1

11

9


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The in-cylinder pressure was measured with AVL type 8QP500C water cooled piezoelectric pressure transducer. The transducer is connected to a Cussons Model 4441 charge amplifier, which provides a calibrated voltage signal for display on a Signal Processing Rack 4410 oscilloscope. After that signal are exhibits in picoscobe 3425. Selected profiles subsequently transferred to a personal computer system for further analysis. Before experiments, pressure transducer is calibrated regularly in a pressurized gas chamber and the amplifier output versus gas chamber pressure is plotted. An example calibration curve of pressure transducer and charge amplifier output is shown in Figure 2..

Figure 2 Calibration curved

0 1000 2000 3000 4000 5000Voltage [mV]

0

10

20

30

40

50

60

70

80

Pre

ssur

e[B

ar]

y(x)=-0.20184+0.014728x


Calibration

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The experimental results in this investigation were obtained from four cylinders, four strokes, water cooled, fuel engines having 80.6 mm bore and 88 mm stroke with a compression ratio of 10. The fuel blends with different fractions were used which is 100/0, 90/10, 80/20 and 70/30 CH4/H2 proportions by varying excessive air ratio for 2000 rpm at full load and 65% full load. The effects of most influential operating variables such as excessive air ratio on cylinder pressure, brake thermal efficiency, CO, CO2 and HC emissions are tested.


Emission Parameters

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Figure 3 Cylinder pressure values versus the Crank angle for different H2 fraction at full load and 65% full load

-40 -20 0 20 40 60Crank Angle [CA]

0

5

10

15

20

25

30

35

40

45

50

Pre

sure

[Bar

]

%0%10%20%30

65% Full Load EAR 1.05

H2

-60 -40 -20 0 20 40 60Crank Angle [CA]

0

5

10

15

20

25

30

35

40

45

50

Pre

sure

[Bar

]

%0%10%20%30

Full Load EAR 1.05

H2

Cylinder Pressure


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Figure 4 Cylinder pressure values versus the Crank angle for different H2 fraction at full load and 65% full load.

Cylinder Pressure

-60 -40 -20 0 20 40 60Crank Angle [CA]

0

5

10

15

20

25

30

35

40

45

50

Pre

sure

[Bar

]

%0%10%20%30

65% Full Load EAR 1.2

H2

-60 -40 -20 0 20 40 60Crank Angle [CA]

0

5

10

15

20

25

30

35

40

45

50

Pre

sure

[Bar

]

%0%10%20%30

Full Load EAR 1.2

H2


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Figure 5 Variation of CO emissions versus EAR for different H2 fraction at full load and 65% full load.

0.95 1.00 1.05 1.10 1.15 1.20 1.25 1.30 1.35Excessive Air Ratio

0.0

0.3

0.6

0.9

1.2

1.5

1.8

2.1

2.4

2.7

3.0

CO

%

65% Full Load

% 0% 10% 20% 30

H2


0.0

0.3

0.6

0.9

1.2

1.5

1.8

2.1

2.4

2.7

3.0

CO

[%]

Full Load

% 0% 10% 20% 30

H2


Emissions

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Figure 6 Variation of CO2 emissions versus EAR for different H2 fraction at full load and 65% full load.


7.5

8.0

8.5

9.0

9.5

10.0

10.5

11.0

11.5

12.0

CO

2%

65% Full Load

% 0% 10% 20% 30

H2


7.5

8.0

8.5

9.0

9.5

10.0

10.5

11.0

11.5

12.0

CO

2[%

]

Full Load

% 0% 10% 20% 30

H2


Emissions

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Figure 7 Variation of HC emissions versus EAR for different H2 fraction at full load and 65% full load.


100

125

150

175

200

225

250

275

300

325

350

HC

[ppm

]

65% Full Load

% 0% 10% 20% 30

H2


100

125

150

175

200

225

250

275

300

325

350

HC

[ppm

]

Full Load

% 0% 10% 20% 30

H2


Emissions

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Figure 8 Brake thermal efficiency values versus the EAR for different H2 fraction at full load and 65%

full load.

0.9 1.0 1.1 1.2 1.3 1.4Excessive Air Ratio

0.12

0.14

0.16

0.18

0.20

0.22

0.24

0.26

Bra

keT

herm

alE

ffic

ienc

y(n

BT)

% 0

% 30% 20% 10

H265% Full Load

0.9 1.0 1.1 1.2 1.3 1.4Excessive Air Ratio

0.12

0.14

0.16

0.18

0.20

0.22

0.24

0.26

Bra

keT

herm

alE

ffic

ienc

y(n

BT)

% 0

% 30% 20% 10

H2Full Load


Efficiency

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Conclusions

An experimental study on performance and emission of a spark ignition engine operating on CH4 with 0, 10%, 20%, and 30% (in volume) hydrogen enrichment was conducted. The main results are summarized as follows.

The experimental measurements gave the results coherent with literature data.

Increasing the EAR leads to a decrease in peak pressure values. Increasing with H2 amount, peak pressure values are closing to TDC. HC, CO2 and CO emissions values decrease with increasing

hydrogen percentage. While at lean mixtures, CO2 emission values are decreasing, at rich mixtures, CO2 emission values are increasing.

Increasing with EAR, CO emissions values are decreasing Brake thermal efficiency values increase, while increasing H2

percentage.


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Thank you.


INVESTIGATION OF CYLINDER PRESSURE FOR H 2 /CH 4 MİXTURES AT DIFFERENT LOAD

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