Natural Gas Applications in Thailand: Locomotive and Fishing Boat

Krisada Wannatong

Researcher, Engineering Research and Engine Test Department

PTT Research and Technology Institute, PTT Public Company Limited, THAILAND

1. Introduction

1.1 Projects Inspiration Natural gas, NG is one of the alternative energy sources for nowadays energy

crisis. In Thailand, natural gas has been utilized extensively, especially for transportation, since its cost is much lower than those of gasoline and diesel. The engine for natural gas could be the modified bi-fuel system or the modified DDF system for gasoline or diesel engine, respectively. It could also be the dedicated engine, originally designed for natural gas.

To promote the utilization of natural gas for the sake of energy crisis solution for Thailand, PTT Public Company (Limited), the leader in energy industrial of the country, has the cooperation with the government to put natural gas in many transportation projects. The paper reports 2 of those projects: natural gas for locomotive engine and for fishing boat engine.

1.2 Engine Conversion Principle Both locomotive engine and fishing boat engine could be converted to be a engine

fuelled by NG by Diesel Dual Fuel (DDF) principle, as shown in figure 2. In diesel engine operation mode, only air is introduced into the combustion chamber in the intake stroke before it is compressed in the compression stroke. At the end of the compression stroke, the diesel fuel is injected into the compressed air which has high temperature and pressure. Then, the combustion occurs and the power from combustion gas is transmitted to the piston, so called the power stroke. Finally, the combustion products are released in the exhaust stroke. In DDF operation mode, NG is mixed with air at the intake manifold and then introduced into the combustion chamber. Therefore, the amount of diesel fuel which is injected at the end of compression is less than original diesel mode.

Exhaust GasAir + NG +Less Diesel

Air + NGAir + NGDDF

Exhaust GasAir + DieselAirAirDiesel

ExhaustCombustionCompressionIntakeStroke

BasicDiagram

Exhaust GasAir + NG +Less Diesel

Air + NGAir + NGDDF

Exhaust GasAir + DieselAirAirDiesel

ExhaustCombustionCompressionIntakeStroke

BasicDiagram

Figure 1. DDF principle

Theoretically, it is easy to convert the original diesel engine into the DDF engine. However, practically, there are some factors that have to be concerned such as the accuracy of the gas flow rate control and the engine knock protection and control.

2. Project I: Natural Gas for Locomotive

PTT Public Company (Limited), Energy Policy and Planning Office, State Railway of Thailand had the joint project to utilize NG for locomotive. The objectives of the project were to test and demonstrate the use of NG as a co-fuel for the train and to study its performance. The details are descripted in the following topic.

2.1 Locomotive

The converted locomotive is GE Locomotive. There are two Cummins KTA50L engines locating inside the locomotive. The specifications of those engines are shown in table 1. The locomotive power system, as shown in figure 2, is considered as the hybrid system because the diesel engine does not drive the locomotive directly, but it drives an alternator to produce the electrical power for an electric motor which drives the locomotive wheels.

The locomotive engine power is divided into 9 steps: idle and steps 1-8

(notches 1-8). At each step, they have constant power as shown in figure 3. Table 1. Cummins KTA50L specification Displacement 50.3 LCylinder Block configuration Cast iron, 600V 16 CylinderGross Engine Power Output 1850 (1380.1) bhp (kW)Bore 158.8 mmStroke 158.8 mmPiston Speed 9.5 m/sCompression Ratio 13.9:1

Diesel Engine Alternator Motor Locomotive WheelsDiesel Engine Alternator Motor Locomotive Wheels

Figure 2. Locomotive power system diagram

Constant Power

V

I

12

345

67

8

Notch Speed (rpm) Power (kW)1 700 392 900 813 1100 1494 1290 2465 1440 3686 1565 4867 1690 5988 1800 782

Figure 3. Locomotive power step

2.2 Engine Conversion

Figure 4 shows DDF diagram of this project. Firstly, the high pressure of NG is reduced from 200 bar to 3 bar at the 1st and 2nd and from 3 bar to 0.1 bar at the 3rd pressure regulator. Since the pressure reduction is high, ice can occur inside and outside the regulators, which could lead to the damage. So, hot water from the engine radiator is used for preventing ice forming. Next, the low pressure NG flows through the control valve and mixes with air at a mixing box. Finally, the mixture flows into the combustion chamber in the intake stroke. The suitable NG flow rate at any pressure and temperature is controlled by gas control valve and gas electric control unit, ECU. In addition, ECU protects the engine from engine knock by reducing the gas flow rate when the engine knock onsets.

1st & 2nd PressureRegulator200 3 bar

3rd PressureRegulator

3 0.1 bar

GasControlValve Mixing Box

(Diffuser)Intake Air

EngineRadiator

ECU

Intake Pressure

Exh. Temp

Knock Sensor

Intake Temp

Gas Leak

Gas Storage200 bar NG

Hot Water from Engine

Cold Water from PRS

Figure 4. DDF system for locomotive

2.3 Natural Gas Supply System Since NG has ca. 5 times less energy density than that of diesel fuel, so the larger container is needed. In this project, the gas cylinders were packed in the 12 ft. standard container as shown in figure 5. The container was carried by tender car located behind the locomotive as shown in figure 6. Permanently, the pressure regulator and piping system were installed in the tender car.

• NG Cylinder Capacity: 210 liter• Number of Cylinder: 48 Cyls.• Total Capacity 10,080 liter• ~2.5 ton NG @ 200 bar

(a)

(b) (c) Figure 5. Gas container: a) design, b) construction, and c) gas Container

LocomotiveGas Container

Figure 6. NG container position

2. Pressure Regulator3. Piping

1. Gas container

Figure 7. NG supply system

In order to fill the fuel, an empty NG container will be replaced by the full one from a mother gas station by a loading truck as shown in figure 8.

Figure 8. NG fueling

2.4 Engine Test There were 2 types of engine test: the engine static load test and the field test. The objectives of the static load test were to calibrate the engine, to determine the performance and emission while the objective of the field test was to evaluate the engine reliability and durability.

2.4.1 Static Load Test

The static load test had been done by replacing the electric motor by a water column. The electrical power which is produced by the alternator will be used for heating the water as shown in figure 9. The power of the engine was divided into 9 steps as shown in figure 3. The original diesel fuel and DDF (the pilot diesel pluses the 76% Methane NG which is the regular NG currently used for transportation in Thailand) were used under the same power output. The measured parameters and NG properties are shown in tables 2 and 3, respectively.

Power from Diesel Engine Alternator Water columnPower from Diesel Engine Alternator Water column

Figure 9. Static load test

Table 2. The measured parameters Temperature Exhaust Emission Engine PerformanceExhaust HC Diesel ConsumptionCooling Water CO NG ConsumptionEngine Oil Black Smoke PowerFuel

Table 3. Natural Gas specification (from east of Thailand) Methane 76.397 mole%

Ethane 6.278 mole%

Propane 2.058 mole%

I-Butane 0.46 mole%

N-Butane 0.423 mole%

I-Pentane 0.131 mole%

N-Pentane 0.081 mole%

C6 Plus 0.081 mole%

CO2 13.444 mole%

Nitrogen 1.943 mole%

Specific Gravity 0.7629 SGU

GHV (sat) 37,000 BTU/kg

2.4.2 Fields Test

The converted locomotive was implemented for the freight train which carries the 1,500 ton container from Lad Kra Bang Station to Leam Cha Bang Port. The route with the overall distance of 140 km is shown in figure 10. Diesel fuel and NG fuel consumption were measured.

Figure 10. The route for field test

2.5 The Combustion Process in DDF

The combustion process in atypical DDF engine depend on many parameters such as the type of gaseous, the pilot fuel, the intake temperature and etc. There are in principle three mode of combustion process. First mode, when very lean gaseous fuel-air mixture is admitted, only pilot diesel fuel in the spray zone is burned. The flame from pilot diesel cannot (or too slowly) propagate to ignite the mixture zone. This incomplete combustion can be indicated by low thermal efficiency and high concentrations of the unburned hydrocarbon and carbon monoxide in exhaust gas.

Second mode, a further increase in the gaseous fuel concentration in the cylinder charge, to the level associated with the corresponding local effective flame propagation limit of the gaseous fuel, the combustion will extend to the whole mixture. This combustion process can be indicated by high output power, high thermal efficiency and low exhaust emission.

Third mode, a further increase in the gaseous fuel concentration in the cylinder

charge, to the level that the auto ignition could be onset outside the combustion zone: this leads to the engine knock.

2.6 Results and Discussion I

2.6.1 Static Load Test Result The objective of engine calibration is to maximize the replacement of diesel fuel by NG while maintaining the power output as that of the original diesel mode. The calibration result of the engine is shown in figure 11 where the replacement percentage could be determined:

DieselumptionDieselConsDDFumptionDieselConstreplacemen

,,% =

0%10%20%30%40%50%60%70%80%90%

N2 N3 N4 N5 N6 N7 N8

Notch

Repl

acem

ent

Engine 1Engine 2

Figure 11. Engine Calibration result

However, at the maximum replacement, at each load, the engine component

temperature, engine thermal efficiency and engine exhaust emission are different, as shown in figures 12 to figure 16. The reasons are:

a) At light load, the engine temperature is very low (as shown in figure 12:

Notches 2-3). The combustion process corresponds to first mode of DDF combustion. This combustion mode indicated by low thermal efficiency as show in figure 14, higher exhaust temperature as show in figure 12, as compared to the original diesel, and high exhaust emission as shown in figure 15. Therefore, the replacement is limited by thermal efficiency and exhaust emission.

b) At part load (Notches 4-6), the engine temperature increasing, the

combustion mode could be considered as the second mode of DDF combustion which

indicated by higher thermal efficiency, lower different temperature between DDF and Diesel mode, lower CO and HC emissions.

c) At high load (Notches 7-8), the engine has high temperature. The

combustion process corresponds to second mode of DDF combustion. This combustion mode indicated by high thermal efficiency, lower exhaust emission and has same level of exhaust temperature as original diesel. However, when increase mixer concentration, some of NG mixer zone can be ignited by itself before flame propagates into it which correspond to third mode of DDF combustion. Therefore, the replacement is low and limited by the engine knock.

Figure 16 shows the black smoke result. From result show that the black

smoke level of Diesel and DDF engine are almost same. The reason is this locomotive use turbo diesel engine which normally low black smoke level. Therefore, used of DDF not show the significant difference.

0

100

200

300

400

500

600

700

0 10 20 30 40

Diesel: T Exh.

DDF: T Exh.

0

20

40

60

80

100

120

0 10 20 30 40

time (min)

Tem

pera

ture

(o C)

Diesel: T Air in

Diesel: T Cooling Water

Diesel: T Lube

Diesel: T Engine Room

DDF: T Air in

DDF: T Cooling Water

DDF: T Lube

DDF: T Engine Room

N2N3

N4N5 N6 N7 N8

Figure 12 the comparison of engine component temperatures, diesel and DDF Engine

0%

5%

10%

15%

20%

25%

30%

35%

N2 N3 N4 N5 N6 N7 N8

Notch

Ther

mal

Eff.

Diesel: E1Diesel: E2DDF: E1DDF: E2

Figure 13. Thermal efficiency of diesel and DDF Engine

00.050.1

0.150.2

0.250.3

0.350.4

0.450.5

N2 N3 N4 N5 N6 N7 N8

Notch

CO, %

Vol

.

DieselDDF

Figure 14. CO emission of diesel and DDF Engine

0

100

200

300

400

500

600

700

800

N2 N3 N4 N5 N6 N7 N8

Notch

HC,

ppm

Vol

.

DieselDDF

Figure 15. HC emission of diesel and DDF Engine

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

N2 N3 N4 N5 N6 N7 N8

Notch

Bocs

h Sm

oke

Num

ber DieselDDF

Figure 16. Black smoke emission of diesel and DDF Engine

2.6.2 Field Test Result

The converted locomotive was implementing for freight train which carries the

container 1,500 ton from Lad Kra Bang to Leam Cha Bang Port as shown in figure 10. The distance between those stations about 140 km. The test result is shown in figure 17.

The load (notch) distribution is averaged from 58 tests. The result shows that notch 7 and no load are usually used. Unfortunately, at no load, DDF system can not be used because of the bad thermal efficiency. Moreover, notch 7 is close to high load that knock can be onset very easily. Therefore, the percentage replacement will keep low to avoid the engine knock. Finally, it has been found that average % replacement of the locomotive on this application is ca. 31% with the efficiency loss of 10 %.

Figure 17 also shows the comparison of average percentage replacement between (go) departure route and arrival (back) route. The comparison shows that back route has more average percentage replacement. The reason is that the height from the sea level of Leam Cha Bang Port is lower than that of Lad Kra Bang Station 50 m.

0%

5%

10%

15%

20%

25%

30%

n1 n2 n3 n4 n5 n6 n7 n8 noload

Notch

% o

f use

d

goback

Figure 17. Average of 58 tests of load (notch) distribution for implementation of NG Locomotive on Lard Kra Bang Station to Leam Cha Bang Port

3. Project II: Natural Gas for Fishing Boat

There are two fishing boats converted to DDF engines as shown in figure 18.

The first one is a trawler used for fishing with ring nets, which is empowered by a 150 hp GARDNER engine. The second one is a lighted boat used for squid catching, which is empowered by a 330 hp HINO EK100 engine.

(a) (b) Figure 18. a) a trawler and b) a lighted boat

3.1 Engine Conversion The engine conversion for fishing boat is based on DDF principal like that for

locomotive but it is simpler. Only basic equipments were installed into the engine, such as pressure regulator for pressure reduction and gas mixer as shown in figure 19.

(a) (b) Figure 19. a) gas mixer and b) gas mixer position

3.2 Natural Gas Supply System

It is difficult to fill NG for fishing boat because it is normally operated

offshore. So, just five 70 liters of water gas cylinders were prepared for engine test. These cylinders were installed at the bottom of each fishing boat as shown in figure 20.

Figure 20. NG cylinder pack for fishing boat

3.3 Engine Calibration The objective of these engines calibration was to maximize the replacement at

the fishing boat operating condition. The trawler is normally running at its full load while the lighted boat is normally running with a constant speed of 700 rpm and at a constant load of 30 kW. This condition is used for generating the electric power of squid fishing boat: it is only 10 % of the full power. Therefore, the engine cannot run with the best efficiency.

3.4 Result and Discussion II From the engine test at the fishing boats operating conditions, we found that

the diesel fuel can be replaced by NG about 31% for trawler boat. The reason of this

low replacement is the engine is running with full load condition, which is closed to the knock limit. For the lighted boat, the suitable replacement that gives the maximum fuel saving is about 50 %. The reason is that the engine is operated at 10% of full load. This condition corresponds to the first mode of combustion process which the engine has low temperature and the combustion process may not completed.

4. Conclusion

The DDF principle was demonstrated on two projects, the locomotive and fishing boat. For locomotive, the converted engines still keep the same power output but need more 10% energy input. The engine produces more unburned hydrocarbon and carbon monoxide exhaust emission especially at low load. However, at high load, the engine still has efficiency close to the original diesel engine. The limitation of NG percentage at low load is the poor efficiency and high exhaust emission whereas the limitation of NG percentage at high load is the engine knock.

For the locomotive, the field test result indicates that the average replacement

is 31%. The reasons of low replacement are that the locomotive is usually operated at either no load or high load condition. These conditions have zero and low replacement, respectively.

For fishing boat, the average replacement is about 31% for a trawler boat and

50% for lighted boat. The engines could not be calibrated to their best efficiencies because they were limited by operating conditions.

These demonstrated project results show that the converted DDF engines have low engine efficiency, low replacement and high exhaust emission. They need more improvement for a commercial feasibility. 5. Reference 1. Z.LIU and G.A. KARIM, “Knock Characteristics of Dual-Fuel Engines Fuelled with Hydrogen Fuel,” Int. J. Hydrogen Energy, Vol. 20 No. 11, pp. 919-924, 1995