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DUAL-FUEL HYDROGEN PICKUP TRUCKS Michael Sulatisky, Sheldon Hill, and Bryan Lung Saskatchewan Research Council 15 Innovation Boulevard Saskatoon, SK, Canada

ABSTRACT: Gasoline and diesel pickup trucks have been adapted to run on hydrogen utilizing dual-fuel electronic fuelinjection systems developed at the Saskatchewan Research Council (SRC). The hydrogen retrofit systems are designed for installation in General Motors pickup trucks equipped with the 6.0-L Vortec gasoline engine or the 6.6-L Duramax diesel engine. The vehicles can be operated in the dual-fuel mode or in the fossil-fuel mode when remote from the hydrogen fuelling station. Greenhouse gas emissions are reduced in proportion to the level of hydrogen substitution for fossil fuels, which is about 40 to 50% in normal driving. Emission tests in the hydrogen/gasoline vehicle indicate reductions in CO, NOx, and THC of 19 to 27%. In the diesel engine, tests indicate a 14% reduction in NOx emissions. The city and highway driving ranges on dual fuel are about 110 and 180 km, respectively. It is expected that the technology can be replicated on various engine platforms at a relatively low cost to help build hydrogen infrastructure. KEYWORDS: dual fuel, hydrogen, trucks, gasoline, diesel

INTRODUCTION Dual-fuel hydrogen pickup trucks have been developed that operate on variable combinations of hydrogen and gasoline and hydrogen and diesel fuel. On average, the mixture is about 40 to 50% on an energy equivalent basis in normal city and highway driving. This paper provides a description of the vehicles and results of performance and emissions tests. Photographs of the vehicles and various assemblies are provided as well. Three dual-fuel hydrogen vehicles have been developed at SRC utilizing the General Motors (GM) 1500 and 2500 pickup trucks as platforms: two operate on hydrogen and gasoline, and the third operates on hydrogen and diesel fuel. The benefits are as follows: • Dual-fuel vehicles provide a low-cost load for developing a hydrogen infrastructure in advance of fuel cell vehicles. • The vehicles are viewed as a bridge to fuel cell vehicles since the same fuel storage systems, safety systems, valves, regulators, and fittings are used in both types of vehicles. • The technology can be replicated on various engine platforms in large numbers at a relatively low cost. The developmental work was conducted with financial support from Ecce Energy Corporation, the Canadian Transportation Fuel Cell Alliance (CTFCA), Natural Resources Canada (NRCan), Saskatchewan Industry and Resources (SIR), and Saskatchewan Research Council (SRC). Note that NRCan, Precarn Inc., and SRC also supported earlier work related to intelligent control systems in fuel cell and natural gas vehicles that was the foundation of the hardware and software development [1]. Previous work in dual-fuel combustion has shown that fuel economy improvements of 7% to 10% are achievable in hydrogen enriched engines [2, 3]. This project builds on the success of a feasibility assessment that showed that peak combustion pressures, backfire, pre-ignition, and knock could all be controlled resulting in normal combustion with hydrogen while achieving substitution rates up to 100% depending on the load [4]. However, a trade-off exists in compression ignition engines between managing nitrous oxide (NOx) emissions and improving fuel economy. At this time, the dual-fuel hydrogen/diesel engine has been calibrated to provide lower NOx emissions as outlined in a subsequent section.

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In summary, this project involves the development of two dual-fuel vehicles: the first being a hydrogen/gasoline vehicle, and the second being a hydrogen/diesel vehicle. The development of these firstgeneration vehicles and their associated control systems provide platforms for optimization of fuel efficiency and emissions, while providing the ability to demonstrate hydrogen vehicles on the road.

DESCRIPTION OF DUAL-FUEL HYDROGEN VEHICLES The dual-fuel hydrogen retrofit system has been designed for installation in Chevrolet 1500 HD (heavy-duty, 1/2-ton) and GMC 2500 HD (3/4-ton) pickup trucks. These vehicles, which are shown in Figures 1 and 2, are either equipped with a 6.0-L Vortec gasoline engine or a 6.6-L Duramax diesel engine and have fourwheel-drive (4WD) transmissions. Weight specifications for the vehicles are summarized in Table 1.

Figure 1: Hydrogen-Gasoline GM 1500 HD Crew Cab

Figure 2: Hydrogen-Diesel GM 2500 HD Extended Cab

Table 1: Weight Specifications for GM Pickup Trucks, kg (lb)

Dual Fuel Hydrogen/ Gasoline Hydrogen/ Gasoline Hydrogen/ Diesel

Vehicle

Drive

Cab/Box

Chev 1500 HD

4WD

Crew/Short

GMC 2500 HD

4WD

Extended/Regular

GMC 2500 HD

4WD

Extended/Regular

Gross Vehicle Weight 3900 (8600) 3900 (8600) 4200 (9200)

Curb Weight

Payload

2619 (5762) 2619 (5762) 2570 (5653)

1290 (2838) 1290 (2838) 1524 (3352)

The main technical features are as follows: •

On-average, the vehicles substitute between 40 and 50% hydrogen for gasoline or diesel fuel in typical combinations of city and highway driving resulting in driving ranges between 110 and 180 km under normal driving conditions.

•

At idle and very light cruise the gasoline vehicle operates on up to 100% hydrogen while the diesel operates on up to 60% hydrogen.

•

At maximum power the vehicles operate on 100% gasoline or 100% diesel fuel; hence, there is no power loss.

•

The vehicles can be switched to gasoline or diesel fuel when remote from the hydrogen fuelling station; hence, driving range is not an issue.

•

Hydrogen fuel purity at 99% is acceptable. 2/8

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•

The vehicles exhibit no power loss and no abnormal combustion characteristics. Peak pressures, rates of pressure rise, engine knock, pre-ignition, detonation, and cycle-to-cycle pressure variations are all managed reliably.

•

When operating in the dual-fuel mode, the original equipment manufacturer’s (OEMs) on-board diagnostic (OBD) system continues to function. Hence, the “check-engine” light will illuminate if there are any codes or malfunctions. Note, however, that we have not yet developed an OBD system for the dual-fuel operation, nor are we monitoring the hydrogen injectors or regulators for malfunctions. The same set points in the OBD system are used in the dual-fuel mode as in the fossil fuel mode.

Each vehicle is equipped with the following components as shown in Figures 3 to 8: •

Tank assembly: Each vehicle is equipped with one, 150-L Dynetek cylinder storing 3.5 kg of hydrogen at 350 bar (5000 psi) as shown in Figure 3. Also shown in the figure are the fuelling probe, a quarter-turn valve, and a high-pressure Tescom regulator. The tank assembly is enclosed by an aluminium box with tool compartment as shown in Figure 4.

¼-Turn Valve

Fill Probe

Hydrogen Gas Detectors

Figure 3: Storage Tank Assembly

•

Figure 4: Tank Enclosure and Tool Area

Under-hood assembly: The following components are used: Keihin injectors, low-pressure Tescom regulator, GFI valves as shown in Figure 5. No modifications (valves, rings, etc.) were made to the engines. Engine power and torque specifications are the same as for the OEM designations: o o

Gasoline engine: model LQ4, 6.0 litre, 300 hp (224 kW) at 4400 rpm and 360 ft-lb torque at 4000 rpm; and Duramax diesel engine: model LLY, 6.6 litre, 310 hp (230 kW) at 3000 rpm and 605 ft-lb torque at 1600 rpm (model LBZ also available at 360 hp with 650 ft-lb).

•

Electronic controller: This has been designed for dual-fuel, multi-port fuel injection and is located behind the rear seat as shown in Figure 6. A relay box and injector drivers are also located behind the rear seat. Inputs include: manifold pressure, engine speed, air flow, and temperature. Work is currently underway to consolidate the electronic controller, relays, and injector drivers into one package.

•

Safety and instrumentation system: The safety system has been designed to detect hydrogen leakage at the storage tank and in the engine compartment as shown in Figures 3 and 5. For redundancy, two hydrogen detectors are located at the storage cylinder and two in the engine compartment. A gauge package in the cab, as shown in Figure 7, indicates where the leakage is occurring at each of the four hydrogen detectors and the severity, as follows: o o

solid green indicates normal operation; flashing green indicates that sensor operation may be faulty or the ignition is off; 3/8

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o o

flashing amber indicates a leak at 10% of the lower explosive limit; flashing red indicates that the leak is at 20% of the lower-explosive limit; at this point solenoid valves close isolating the leak, and the vehicle automatically switches to gasoline or diesel operation.

o

Relay Box Controller

Hydrogen Gas Detectors

Fuel Injectors Injector Drivers

Figure 5: Under-Hood Assembly

Figure 6: Relay Box, ECU, Injector Drivers

•

Wiring harness: Made for eight hydrogen and eight gasoline fuel injectors (four diesel) and integrated with gas detection system and the safety shutdown system.

•

Hydrogen fuel gauge: A gauge in the cab indicates the percent of hydrogen in the storage tank as shown in Figure 7.

•

Figure 7: Hydrogen Fuel Gauge and Hydrogen Detector Monitor •

Figure 8: Dual-Fuel Hydrogen Switch

Dual-fuel switch: When the toggle switch shown in Figure 8 is moved to the up position, the vehicle is switched to dual-fuel operation, and a green indicator light illuminates. When the switch is move in the down position, the vehicle is switched to gasoline (or diesel fuel) and the indicator light switches off. Note that the safety system will switch the vehicle to operate on gasoline or diesel fuel if a hydrogen leak is detected. Currently, the vehicle is switched to hydrogen manually when the engine is warm and off hydrogen when the tank is near empty, Development work is underway to do this automatically.

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PERFORMANCE AND EMISSIONS Fuel Economy, Percent Substitution, and Driving Range SRC’s dual-fuel hydrogen systems have been developed for General Motors heavy-duty (HD) pickup trucks with the 6.0-L gasoline and 6.6-L Duramax diesel engines. At this time fuel economy measurements and driving range have only been determined based on city and highway measurements on the road. Fuel economy measurements in the laboratory on a chassis dynamometer according to the transient city (FTP75) and highway driving cycles have not been completed. Note as well that information on city and highway fuel economy is not available for these vehicles in Fuel Economy Guides in Canada or the United States because they are not classed as light-duty vehicles. Hydrogen/Gasoline Vehicles Percentage hydrogen substitution for gasoline, fuel economy, and driving range are shown for on-road tests on a 2005 GMC Sierra 4WD pickup truck in the city and on the highway in Table 2. Note that the testing was conducted during the winter when the ambient temperature ranged between -1 and -11oC. In city driving, the average speed was about 24 km/h over a 7.5 km course with about 2.5-km residential, 2.5-km freeway, and 2.5-km industrial. The percentage hydrogen substitution for gasoline was 46.2% in the city at an average speed of 27.8 km/h and 42.2% on the highway at an average speed of 105 km/h on an energy equivalent basis. The fuel economy was slightly better on dual fuel than on gasoline, which is consistent with references 2 and 3. The driving range on dual-fuel was 108 km in the city and 177 km on the highway. However, the vehicle can be switched to gasoline operation when the hydrogen tank is empty. Table 2: Dual-Fuel Hydrogen/Gasoline, Percent Substitution, Fuel Economy and Driving Range, 2004 GMC 2500 Sierra 4WD Pickup Truck: Type City Highway

Average Fuel Economy (L/100km) (mpg) 24.4 11.6

Percent Hydrogen

Ambient Temp (oC)

Average Speed (km/h)

Gasoline

0

-11 to -2

24.4

Dual-Fuel

46.2

-4 to -7

27.8

23.7

11.9

108

Gasoline

0.0

-1.0

103.0

16.5

17.2

595

Dual-Fuel

42.2

-1.0

105.0

15.8

17.9

177

Fuel

Driving Range (km) 402

The results of road tests for various driving conditions are summarized in Table 3 for the 2005 Chevrolet 1500 HD pickup truck utilizing the hydrogen/gasoline dual-fuel system. Measurements were made under the following conditions: highway driving, driving downtown in slow-moving traffic, city driving to the airport, and driving to an industrial area. To obtain the data on driving range, the tank was filled to 350 bar (5000 psi), and the vehicle was driven in various types of traffic in two-wheel-drive mode without carrying any payload. Table 3: Dual-Fuel Hydrogen/Gasoline Percent Substitution, Fuel Economy, and Driving Range, 2005 Chevrolet 1500 HD Pickup Truck Average Speed

Description

(km/h)

Hydrogen Driving Average Substitution Range Fuel Economy (L/100 km) (%) (km)

105

16.0

30

290

Downtown driving in bumper-to-bumper traffic

0 to 60

30.0

76

60

Downtown and freeway to airport in light traffic

0 to 105

13.0

56

190

Industrial area and highway with a prolonged stop for a train 0 to 105

14.3

51

200

Overall

18.3

53

170

Highway driving against a headwind

0 to 105

The overall driving range for the combination of city and highway driving was 170 km (105 miles) at an average hydrogen substitution rate of 53%, as shown in the bottom row of the table. After this point the 5/8

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vehicle was switched to operate on gasoline. For highway driving at 105 km/h while pushing a headwind, the driving range was 290 km, and the substitution rate for hydrogen was 30%. For this case, the fuel economy was 16.0 L/100 km. Under light load, the substitution rate was 76% hydrogen, which reduced the driving range on hydrogen to about 60 km. Combined driving through downtown traffic and then on the freeway to the airport resulted in a 56% level of substitution and a driving range of 190 km (118 miles). Note that the substitution rate at idle was 100%. Hydrogen/Diesel Vehicle On-road monitoring results for the dual-fuel, hydrogen/diesel pickup truck in the winter are shown in Table 4. The average substitution rate of hydrogen for diesel fuel on an energy equivalent basis was 50% in the city and 26% on the highway; however, the substitution rate was 60% at idle. The driving range on dual fuel in the city and highway were 102 and 189 km, respectively. Note that the fuel economy was assumed to be the same on dual fuel and diesel fuel to perform the calculation. Table 4: Dual-Fuel Hydrogen/Diesel Percent Substitution, Fuel Economy, and Driving Range, 2001 GMC 2500 HD Pickup Truck Type City Highway

Fuel

Percent Hydrogen

Diesel Dual Fuel Diesel Dual Fuel

0 50 0 26

Ambient Temp (oC) -1 to -20 -1 to -17 -4 to -14 -6.0

Average Fuel Economy (L/100km) (mpg) 18 15 18 15 12 23 12 23

Average Speed (km/h) 25 25 105 105

Driving Range (km) 532 102 787 189

Commercial pickup trucks of the above types utilize from 3500 to 8000 litres of fossil fuel per year; hence, a considerable amount of hydrogen would be utilized in fleet applications at hydrogen substitution rates of 40 to 50%. Filling once per day over a year would consume 750 kg of hydrogen, which is equivalent to about 3000 litres of gasoline (assuming a 3 kg average fill and 250 fills per year). Steady-State Emissions Results Steady-state emission measurements were conducted on the dual-fuel vehicles at various loads and substitution levels on a chassis dynamometer at SRC. The results are summarized in Figures 9 to 12. 2004 GM Siverado HD 4 x 4, Hydrogen/Gasoline, Steady-State Emission Tests, Reduction in Carbon Dioxide CO2 Reduction (%)

100 % CO2 Reduction

80 60 40 20 0 H2 = 100% Idle

H2 = 57% H2 = 38% H2 = 29% H2 = 16% H2 = 14% Light

LightMed

Medium

MedHeavy

Heavy

Load Figure 9: Percentage Reduction in Carbon Dioxide Emissions, Dual Fuel versus Gasoline

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As indicated in Figure 9, substitution levels for the hydrogen/gasoline vehicle ranged from 100% at idle to 14% at heavy load, and carbon dioxide (CO2) emissions were reduced in proportion to the level of substitution. For example, under light load CO2 emissions were reduced by about 52% for a hydrogen substitution rate of 57% (on an energy equivalent basis). Carbon monoxide (CO), nitrous oxide (NOx), and total hydrocarbon (THC) emissions were also reduced by the hydrogen dual-fuel system in the gasoline vehicle. Average emissions reductions for the tests from light to heavy load ranged from 20 to 28%, as shown in Figure 10. 2004 GM Siverado HD 4 x 4, Hydrogen/Gasoline, Steady-State Emission Tests Average % Reduction in CO, NOx, THC

Emission Reduction (%)

30.0 25.0 20.0 15.0 10.0 5.0 0.0 CO

NOx

THC

Average Emissions from Light to Heavy Load

Figure 10: Percentage Reductions in CO, NOx, and THC Emissions, Dual Fuel versus Gasoline Figures 11 and 12 compare the emissions of the hydrogen/diesel pickup truck on dual fuel with diesel fuel. For the same fuel economy at a substitution rate of 42% hydrogen, NOx emissions were reduced by 14%, and CO emissions were reduced by 86%. An oxidation catalyst was added to reduce CO emissions in the dual-fuel vehicle; however, the catalyst was not used for diesel-only operation. Note that 2005 diesel pickup trucks from GM have an oxidation catalyst, but they did not have them in 2001 model-year. Dual-Fuel Hydrogen/Diesel GM 2500 HD Pickup Truck Emissions: 42% Hydrogen, 41 hp (Optimized Controller) 600

NOx and CO (ppm)

500

Diesel Dual Fuel

400 300 200 100 0 CO NOx 6.6-L Duramax Diesel Engine

Figure 11: Steady-State Emissions of CO and NOx, Dual Fuel versus Diesel

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Dual-Fuel Hydrogen/Diesel GM 2500 HD Pickup Truck Emissions: 42% Hydrogen, 41 hp (Optimized Controller) 100.0 % Reduction

Percent Reduction

80.0 60.0 40.0 20.0 0.0

CO NOx 6.6-L Duramax Diesel Engine

Figure 12: Percent Reduction in CO, and NOx, Dual Fuel versus Diesel CONCLUSIONS AND RECOMMENDATIONS Based on the developmental work and testing conducted in this project, the following conclusions can be drawn: 1. Dual-fuel technology allows hydrogen to displace on-average from 40 to 50% of the fossil fuel used in conventional internal combustion engines in typical driving in the city and on the highway. At idle, hydrogen substitution rates are 100% and 60% for the gasoline and diesel trucks, respectively. 2. The driving range on dual fuel is about 110 km in the city and 180 km on the highway under normal driving conditions. 3. The vehicles exhibit no power loss or abnormal combustion characteristics. 4. The vehicles retain adequate cargo space and can function adequately in commercial applications. 5. Hydrogen/gasoline operation demonstrates lower criteria air contaminant emissions (including NOx) compared to gasoline operation in steady-state emission testing. 6. Hydrogen/diesel operation demonstrates 14% lower NOx and over 80% reduction in CO emissions utilizing an oxidation catalyst in steady-state emission testing. 7. The vehicles include an advanced hydrogen safety system that was developed by SRC. 8. A functioning OEM on-board diagnostic system is maintained for the dual-fuel gasoline and diesel vehicles. However, the fossil-fuel calibration is used, and we do not monitor the hydrogen components for fault codes. Dual-fuel hydrogen vehicles can be used to bridge the gap between conventional vehicles and fuel cell vehicles, and the technology appears to be sufficiently mature to allow it to move from the developmental phase to the demonstration phase. Hence, it is recommended that dual-fuel hydrogen vehicles be demonstrated in fleet applications as a step on the road to commercialization.

REFERENCES 1. Sulatisky, M., et al., “Intelligent Control Systems for Fuel Cell and Natural Gas Vehicles,” SRC Publication 11305-1E02. 2. Karim, G.A., Klat S.R., “Hydrogen as a Fuel in Compression Ignition Engines,” J.Mech.Eng, ASME 1976; 98:3439. 3. Kumar, M.S., Ramesh, A., and Nagalingam, B., “Use of Hydrogen to Enhance the Performance of a Vegetable Oil-Fuelled Compression Engine,” International Journal of Hydrogen Energy 28 (2003), 1143-1154. 4. Hill, S., Lung, B., and Sulatisky, M., “Development of First-Generation Hydrogen Vehicles,” SRC Publication No. 11741-2C05, November 2005.

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