Development Project of Hydrogen Engine System for Heavy Duty Vehicles

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1 Development Project of Hydrogen Engine System for Heavy Duty Vehicles Yoshio Sato Atsuhiro Kawamura* Environment Research Department National Traffic Safety and Environment Laboratory (NTSEL) 42-27, 7-chome, Jindaiji-higashi Chofu-city, Tokyo, Japan Abstract Now, movement in the world is shifting toward ecological and sustainable action with the influence of the global warming and other environmental issues. Hydrogen engine vehicles have an opportunity to support the decarbonization of the society. This project is the first step to develop a DISI (Direct-Injection Spark-Ignition) multicylinder hydrogen ICE (Internal Combustion Engine) system aimed at combining high power output and low NOx emission. The results of the first activities of the project are as follows: 1) High-pressure hydrogen gas direct injectors with a compact body size and control responsiveness that are suitable for the transient driving of the multi-cylinder hydrogen engine were developed. 2) The performance of the developed hydrogen engine system was evaluated, and the target output was obtained. 3) JE mode transient emission testing of the hydrogen engine system with NSR catalyst and oxidation catalyst was carried out; it showed emissions lower than those specified by the JAPAN 9 emission regulations. Key Words: hydrogen fuel, internal combustion engine, heavy duty vehicles. 1. Introduction In order to prevent air pollution and global warming, the introduction of environmentally-friendly vehicles in both categories (passenger cars and freight trucks) is strongly demanded. To satisfy this demand, electricity and hydrogen, which do not emit CO 2 during consumption, have attracted attention as energy sources for future vehicles. Designers are currently developing passenger cars and shuttle buses that use a battery and a hydrogen FC. For small- and medium-sized trucks, diesel *Former NTSEL researcher hybrid systems can be put into practical use. However, a battery or a hydrogen FC cannot be used in large-sized (heavy duty) trucks, which currently require a high power output. For the aforementioned reasons, the DISI (Direct - Injection Spark-Ignition) multi-cylinder hydrogen ICE (Internal Combustion Engine) system development project for heavy-duty vehicles is promoted by the Nextgeneration Environmentally Friendly Vehicle Development and Commercialization Project (EFV21) of the Ministry of Land, Infrastructure, and Transport (MLIT) of Japan as one of the technical candidates that can greatly reduce the air pollution and global warming contribution of such trucks. 2. Targets of the development project The performance target for the multi-cylinder hydrogen engine system is shown in Table 1. In this project, as for the past development concept about the hydrogen engine system, the high output power and the coexistence of the low exhaust emissions were difficult [1] [2]. Four cylinder was chosen as the minimum number of the cylinders that a stable performance will be able to provide. This table describes a high-performance hydrogen engine system with output and fuel consumption equal to that of a multi-cylinder NA (Natural Aspiration) diesel engine and with ultra-low emissions that meet the JAPAN 9 emission regulations when tested using the Japanese transient emission testing mode for heavy-duty vehicles (JE). Table 1. Performance targets of the project Item Output power Emissions (by JE drive mode) Fuel economy 1 kw by 4-cylinder naturally aspirated (NA) NOx: Less than. g/kwh PM: Near-zero level Target performance CO 2 /CO/NMHC: Near-zero levels The same level as NA base engine ISBN:

2 3. High-pressure hydrogen gas injector A high-pressure hydrogen gas direct injector will be necessary for realizing the high-performance multicylinder hydrogen engine. The injector will be compact in size and able to instantaneously inject a large quantity of hydrogen into the high-pressure combustion chamber. The high-pressure hydrogen gas direct injector developed in this project is shown in Figure 1. This injector is based on a common-rail type direct injector for the base diesel engine, thus maintaining installation compatibility. The hydrogen gas is supplied at a maximum pressure of MPa to maintain its independence from the flow of the working fluid. The opening and closing of the needle valve are performed by controlling the spill amount of a working fluid (diesel oil) supplied from a common rail by the timing of an electromagnetic valve. Thus, this injector aims at achieving the high-speed response needed for multiple-stage injection in the future [3]. In the future specification, non-fuel will be used as the working fluid. A performance evaluation of the four cylinder hydrogen engine system equipped with four pieces of experimentally-produced injectors (injection pressure 1 MPa and working fluid pressure 6 MPa) was performed in which the system was operated for approximately 1 hours. The injectors showed a linear relationship between signals from the idling equivalency injection quantity (about 3 milligrams per injection) and the maximum output equivalency injection quantity (about 27 milligrams per injection), as shown in Figure 2. In addition, leakages from the needle valve sheets were maintained at less than 1 milliliters per minute at standard temperature and pressure (STP). Electric magnet Working fluid drain port Servo valve Flow control plate H 2 inlet Working fluid inlet H 2 (Max. MPa) Working fluid drain Working fluid (Max. 1 MPa) Nozzle cap (a)photo Lift sensor Needle valve H 2 Injection (b)cross-sectional drawing Figure 1. Common-rail type high-pressure hydrogen gas direct injector Injection Rate (mg/cycle) Injection Rate (mg/cycle) Cylinder NO: 4 3 Injector ID: Cylinder NO: 1 Injector ID: 2 y=13.78x R 2 =.96 y=12.91x R 2 = Injection Rate (mg/cycle) Injection Rate (mg/cycle) Cylinder NO: 3 3 Injector ID: 2 1 Cylinder NO: 2 Injector ID: 3 y=12.43x -.1 R 2 =.9 y=13.8x - 7. R 2 = Figure 2. Injection characteristics of the injectors ISBN:

3 4. Performance of developed hydrogen engine The specifications of the multi-cylinder hydrogen engine are shown in Table 2. The combustion chamber configuration is shown in Figure 3, whereas the specifications of the NO x reduction catalyst system are shown in Table 3. The base engine is a mass-produced 4.7-liter Direct-Injection four-cylinder turbo diesel engine (HINO JD) for medium-duty trucks with a GVW of tons. The main remodeling of the base engine involves a reduction of the compression ratio (from 18 to 12.7), an addition of a spark plug to the hole for the glow plug, and a disassembly of the turbocharger. The injector is placed at the center of the combustion chamber of the engine. Base engine Engine type Cooling system No. of valves Engine displacement Bore Stroke Compression ratio Fuel Injector EGR system Ignition system Aspiration Table 2. Specifications of hydrogen engine Item Hino JD-TC 4-cycle inline 4-cylinder Water cooled 4 valves SOHC L 112 mm 1 mm 12.7 : 1 Hydrogen gas Name of injector: TCU Hole type: Dia. 1.2 mm 11 holes (Main: 1 holes, Sub: 1 hole) Injection pressure: 1 MPa Water cooled EGR Spark ignition Specification Natural aspirated (NA) Table 3. Specifications of NOx reduction catalyst system Item Type Content Diameter Cell Thickness Cell Density Composition Primary Catalyst NSR Catalyst 4 L mm.1 mm 93 cells/cm 2 Pt/Rh Secondary Catalyst Oxidation Catalyst 4 L mm.1 mm 93 cells/cm 2 Pt The nozzle hole was designed to discharge a radiating spray so that hydrogen gas is dispensed equally throughout the combustion chamber. Additionally, a side hole was added to the nozzle so that hydrogen gas passes near the spark plug to enable firing to be performed at the end of injection (EOI). The experimental system for the performance examination of the multi-cylinder hydrogen engine system is shown in Figure 4. The engine control was performed using a three-dimensional control map of engine speed and accelerator position for the injection timing, the duration of the injection, the ignition timing, the opening level of the throttle valve, and the opening level of the exhaust gas recirculation (EGR) valve. The working fluid pump for the injectors was driven by an electric motor working at a constant pressure of 6 MPa. It was followed the JAPAN 9 emission regulations using the transient emission testing mode (JE) as closely as possible. The measuring method for exhaust emissions used raw exhaust measurement, and the measuring method for PM used full flow dilution measurement. Injector Spark plug Intake valves Spark plug Top of injector (Nozzle cap) 22 deg I.D. 71 Piston Combustion chamber Injection directions Top of injector (Nozzle cap) Exhaust valves Figure. 3 Combustion chamber configuration of four cylinder hydrogen engine ISBN:

4 ECU Combustion analyzer & Data logger 1 EGR cooler Exhaust MS type Exhaust gas H gas Cam & Crank angle analyzer 2 analyzer analyzer (Direct) (CVS) Exhaust gas temp. Cylinder Laminar press. NOx sensor flow meter EGR H 2 gas injectors Air temp. valve for NSR catalyst Full Intake Catalyst (NSR flow press. + Oxidation) dilution Throttle valve Spark 1 plugs MPa Thermal mass Thermal mass Working fluid flow meters with H 2 gas direct flow meter with pump for surge tanks (for injectors surge tank (for Sampling common-rail injectors) reducing agent) FTIR filter for. PM 6 MPa MPa Engine Regulator dynamometer Common-rail (Working Coriolis mass Data logger 2 Motor fluid for injector operation) flow meter H 2 gas Figure 4. Schematic diagram of experimental apparatus of four cylinder hydrogen engine Brake power (kw) Max. torque of NA test engine (measured): Power of charged base engine: operated with diesel fuel Max. power of NA test engine (measured): operated with hydrogen Set torque of NA test engine (for JE): Set power of NA test engine (for JE): , 1,4 1,8 2, 2,6 3, 3,4 Engine speed (min -1 ) Figure. Engine performance curve Torque of charged base engine: operated with diesel fuel Target max. power by NA engine: Brake torque (Nm) ISBN:

5 The measurement results of the output performance of the four cylinder NA hydrogen engine system and the set point (bold line) of the later JE mode emission testing are shown in Figure. The output performance (dashed line) of the base engine (DI turbo diesel engine) is shown in the same figure. An output exceeding the aim of this project (1 kw) and the same torque as that of the base engine at low engine speed were confirmed. In addition, the electricity consumption of the working fluid pump was around 1.4 kw. Improvement of the engine drive of the working fluid pump and further output improvement by turbo-charging will be included in our future research efforts.. Emission test results of hydrogen engine The emission results of the JE mode transient testing mode are shown in Figure 6. Because it was the control specifications that complicated control logic cannot make, the construction of controlling it had difficulty with NOx reduction in JE mode transient emission testing mode. Therefore, the reducing of the NSR catalyst enough before starting the test was performed. As a result, the NOx emission was very low at the diesel oxidation catalyst (DOC) outlet because of the effect of the storage of NOx emission at the NSR catalyst. Moreover, NOx, CO, NMHC and particulate matter (PM) concentrations were below JAPAN 9 emission regulations. The capacity of the NSR catalyst is assumed to be suitable for engine displacement; however, the possibility of its diminution may need to be investigated in the future. The emission of CO 2 was about.9 g/kwh. A decrease in the working fluid was not confirmed for the injectors in all examinations. Because an increase in THC and CO 2 in exhaust was observed under conditions of acceleration, deceleration, or high load, the measured CO 2 and PM seem to originate from engine oil. Thus, reduction of the inflow of the engine oil to the cylinder Emission (g/kwh) Reguration.2 Engine out (without EGR) Engine out (with EGR) DOC out (With EGR)...1. will be necessary when further reduction of CO 2 and PM are required in the future. 6. Conclusions The planned development of a hydrogen engine system for heavy-duty trucks is one of the technological candidates for air pollution reduction and global warming prevention for the large-sized (heavy-duty) trucks supporting Japanese freightage. This project is the first in Japan to develop a DISI multi-cylinder hydrogen engine system aimed at combining high power output and low NOx emission. The following results were achieved during the initial work on this project: 1) High-pressure (Max. MPa) hydrogen gas direct injectors with a compact body size and control responsiveness corresponding to the transient driving of the four cylinder hydrogen engine (operated hydrogen pressure 1MPa) were developed. 2) The performance of the four cylinder hydrogen engine system was evaluated, and the target output (1 kw by NA) was obtained. 3) JE mode transient emission testing of the four cylinder hydrogen ICE system with NSR catalyst and DOC was carried out and showed the feasibility of reducing emissions to levels below those specified in the JAPAN 9 emission regulations. For further performance enhancement of the multicylinder hydrogen engine system, improved stability and durability of the high-pressure hydrogen gas direct injector and optimization of the transient control system will be necessary. By the present, the effective method for fuel consumption evaluation is not offered [4] []. Fuel consumption evaluation of the DI hydrogen engine will require the development of a method for highpressure hydrogen consumption measurement at transient operation. In addition, with respect to unregulated substances such as N 2 O in the NSR catalyst [6], it will be necessary to devise a combustion strategy such as moderate injection and/or ignition near the TDC that enables further NOx reduction at the engine outlet and expanded coverage. In these efforts, it will be necessary to perform the visualization and the CFD simulation of high-pressure hydrogen injection/mixture formation. These are in progress now partly in the next efforts of this project. And the development of an in-vehicle hydrogen tank system will also be necessary for realizing trucks using the DISI multi-cylinder hydrogen ICE system... NOx CO NMHC PM Figure 6. Emission test results (JE mode test) ISBN:

6 7. References [1] Helmut Eichlseder, Thomas Wallner, Raymond Freymann, Juergen Ringler, "The Potential of Hydrogen Internal Combustion Engines in a Future Mobility Scenario", SAE paper , Future Transportation Technology Conference, Costa Mesa, June 3. [2] Gerrit Kiesgen, Manfred Klueting, Christian Bock, Hubert Fischer, "The New 12-Cylinder Hydrogen Engine in the 7 Series: The H2 ICE Age Has Begun", SAE paper , 6 SAE World Congress, Detroit, April 6. [3] Kimitaka Yamane, Masakuni Oikawa, Tomonori Kitaura, Kouta Mawatari, Takashi Kondo, Yasuo Takagi, Yoshio Sato and Yuichi Goto, A Development of a High Pressure H2 Gas Injector with High Response by Using Common-Rail Injection System for Direct Injection H2 Fuelled Engines, WHEC (World Hydrogen Energy Conference) 16, Lyon, June 6. [4] Robert J. Natkin, Xiaoguo Tang, Kathleen M. Whipple, Daniel M. Kabat, William F. Stockhausen, "Ford Hydrogen Engine Laboratory Testing Facility", SAE paper , SAE 2 World Congress, Detroit, March 2. [] James Francfort, Don Karner, "Hydrogen ICE Vehicle Testing Activities", SAE paper , 6 SAE World Congress, Detroit, April 6. [6] Atsuhiro Kawamura, Tadanori Yanai, Yoshio Sato, Kaname Naganuma, Kimitaka Yamane and Yasuo Takagi, Summary and Progress of the Hydrogen ICE Truck Development Project, SAE paper , SAE International Journal of Commercial Vehicle, 2(1), October Acknowledgments This work was performed under the Next-generation Environmentally Friendly Vehicle Development and Commercialization Project (EFV21) of the Ministry of Land, Infrastructure, and Transport (MLIT) of Japan. The authors greatly appreciate the assistance of this organization and its personnel. ISBN: