**1. Introduction**

At the current rate of consumption, it is estimated that the crude oil reserves of the entire world will be depleted in less than 40 years. Due to an unstable international situation, the price of crude oil keeps rising, compelling the price of other fossil energies to soar. Because of its high dependency on imported energy, Taiwan is deeply affected by the crude oil price. Additionally, because of its low cost and high carbon number, fossil fuel has been the major fuel used in Taiwan. The enormous number of vehicles and motorcycles in Taiwan emit excess amounts of carbon dioxide, sulfur, and nitrogen; consequently, the level of greenhouse gas emissions in Taiwan far exceeds that of other countries. Because coal, natural gas, and petroleum will still be the major sources of energy in the short to medium term future; and since increasing energy efficiency is presently a globally acknowledged strategy; the use of new energy technologies for the transformation of traditional fuels into clean fuels - such as clean coal, fuel cells, and fuel reforming - is being promoted all over the world. Combining all the factors described, it has become necessary to quickly develop new energy and combustion techniques with existing equipment and resources to reduce air pollution produced by combustion.

Plasma-assisted reforming of hydrogen production is a promising energy utilization technology, and an increasing number of research units are conducting related experiments around the world. Plasma-assisted production of hydrogen is different from traditional hydrogen production approaches, and the equipment involved in the plasma-assisted production of hydrogen is small, easy to start, and economical; it can also increase overall thermal efficiency of internal combustion engine by combining with the hydrogen produced from the fuel reforming system.

The method of hydrogen production by plasma or catalytic converters with various hydrocarbon fuels has been studied by various researchers internationally. An arc generated plasma was used to facilitate the reforming reaction by heating. The heated mixture could be distributed to all of the passages in the reaction chamber by arc rotation driven by magnetic field. Water vapor could be directed into the system to lower the temperature of the electrodes via heat recycling to prevent the reaction region from over-heating, therefore extending the life of the system (Bromberg et al., 1997). The optimum settings and the cost of

Waste Heat Recycling for Fuel Reforming 357

reforming using external heating from the perspective of thermodynamics was studied. It was revealed that higher O/C ratios resulted in low thermal efficiency as a significant amount of fuel was found to be oxidated in the reforming process (Lutz et al., 2004). The reforming of exhaust gas recirculation (EGR) for producing H2 and CO was studied. By adding the contents of H2 and CO, the in-cylinder premixed combustion of engine would be enhanced; and then a super lean burn process, low NOx operations could be achieved (Zheng et al., 2004). A numerical simulation on the technique of pure external heating and the method of reusing partial oxidation produced through external heating of hydrogen were used for investigating thermal efficiency. The former was found to be of higher efficiency, which was enhanced with increasing H2O/Carbon ratio (Lutz et al., 2003). A small scale hydrogen producing system was designed with utilizing heat exchange to heat up the vapourising unit. The reforming thermal efficiency attained was as high as 78% while the methane conversion efficiency was 89%, capable of supplying a 1kW fuel cell (Seo et al., 2006). Dimethyl ether (DME) and methanol-reformed gas (MRG) were produced from methanol by onboard reformers utilising the exhaust heat from the engine. Because the reactions producing DME and MRG are endothermic, a part of exhaust heat energy can be recovered during the fuel reforming process. This research experimentally investigated characteristics of combustion, exhaust emissions, engine efficiency and overall thermal efficiency including the waste heat recovery through the fuel reforming in the HCCI combustion engine system (Shudo, 2006). Tri-reforming of natural gas using flue gas from power plants with the combination of heat transfer or heat exchange including reactor heat up and waste heat utilization was studied. The tri-reforming process could be applied to the production of synthetic gas by reforming of natural gas using gas mixtures (containing CO2, H2O, and O2) as co-feeds. As a result, the mitigation of CO2 could be achieved by waste heat recovery. However, various strategic considerations, technical approaches, and specific research directions have been presented. More research is necessary towards effective CO2 conversion into useful substances using renewable sources of energy (Song, 2006). The hydrogen production from low carbon fuels by using the plasma-catalyst hybrid converters with energy conservation was investigated. The energy saving schemes, namely, heat recycling and heat insulation were applied to enhance the hydrogen production. The results showed that the energy saving systems enabled the O2/C ratio to be decreased to reduce oxidation of hydrogen and carbon monoxide and thereby improving the concentration of hydrogen-rich gas. By heat recycling, the improvement in methane conversion efficiency in a lower fuel feeding rate was achieved; moreover, the hydrogen production increased significantly with the water-gas shifting reaction under the same operation parameters (Horng et al., 2008a, 2009). System analysis was conducted on a combined system for methane steam reforming comprising conventional hydrogen production and waste heat recovery from steelmaking. The results showed that the factors evaluated including the natural gas consumption, enthalpy flow, CO2 emission, cost, and exergy loss were improved for the waste heat recovery system. This supports the feasibility of hydrogen production from recovered waste heat. Moreover, the proposed system is expected to produce less CO2

emission due to less fuel consumption (Maruoka et al., 2010).

Combustion principles state that hydrogen has a high heating value and a high flame speed. If hydrogen can maintain the normal combustion efficiency in engine even at an extremely lean mixture, it would reduce fuel consumption and exhaust emissions. A small

a plasma–catalyst natural gas reformer were analyzed. Preliminary results showed that the specific energy consumption of a small scale plasma reformer can be effectively reduced through efficient thermal management and heat recycling (Bromberg et al., 2000). The characteristics of hydrogen production from isooctane were studied and reported that hydrogen yield at catalyst temperatures as high as 800oC was significantly improved by using a combined plasma/catalytic system (Sobacchi et al., 2002). Some researchers investigated autothermal reforming of methane and propane by 2 wt%-catalysts on alumina support. They proposed the activity level of the catalysts in descending order as: Rh > Pd > Ni > Pt > Co. They demonstrated that high activity was achieved by loading suitable amount of Ni, while under the same loading, activity was higher for the Rh-based catalyst (Ayabe et al., 2003). A plasma catalytic reactor was employed for the combined oxygensteam reforming of methane. It was found that by combining the dielectric barrier discharge (DBD) and a Ni catalyst the conversion of methane was not improved, but complete conversion of oxygen was achieved. Under a suitable temperature to maintain the Ni catalytically active, the product selectivities changed significantly (Pietruszka & Heintze, 2004). Preparation of intake mixture for reforming performance was investigated. It showed that feeding fuel via an intake swirl significantly facilitated the conversion efficiency of methane, and elevated the concentration of hydrogen. Both higher arc frequencies and longer retention time improving hydrogen concentration were also confirmed (Horng et al., 2007). The plasma converter on hydrogen production via methane reforming and the carbon deposit growth on the electrode surface were explored, and the microstructure of carbon was analyzed with scanning electron microscopy (SEM) and micro-Raman spectroscopy (Horng et al., 2006a). The reforming of aliphatic hydrocarbon such as methane, propane and neopentane, using non-thermal plasma was carried out. It demonstrated that reforming by combining carbon dioxide with methane and propane, yielded a higher H2/CO ratio than using neopentane. When using steam reforming, methane yielded the highest H2/CO ratio (Futamura et al., 2006). The literature on the field of hydrogen production assisted by nonthermal plasma reforming was reviewed by a group of researchers. They concluded that most of the existing reforming reactors were still being developed and advanced in research laboratories (Petitpas et al., 2007). The Tokyo Institute of Technology studied the plasma and the glid-arc reforming approaches and found that both of them required high temperature to produce hydrogen. In contrast, the dielectric barrier discharge (DBD) reforming approach could produce hydrogen at lower temperatures (between 400 and 600 °C) by adding water vapor in fuel (Nozaki & Okazaki, 2005).

Concerning the heat regeneration, a high energy level of thermal plasma to accelerate the reforming reaction was studied. It was suggested that the methods of heat insulation, heat regeneration and improved plasma catalysis could reduce the energy loss and improve methane conversion efficiency (Bromberg et al., 1999b). The utilization of phase change material (PCM) for heat-recovery was experimentally studied. Copper balls as the PCM were encapsulated by nickel film with/without an insertion of carbon or ruthenium as an inhibition layer. The results showed that the copper PCM with the thick film of nickel and an inactive layer between nickel and copper was available for producing hydrogen by hightemperature waste heat recovery (Maruoka et al., 2002). A high temperature plasma technique was applied on the reforming of methane or other hydrocarbon fuels to produce hydrogen-rich gas. To reduce energy loss and to increase methane conversion, heat could be insulated and exchanged at the plasma converter. Thermal efficiency of partial oxidation

a plasma–catalyst natural gas reformer were analyzed. Preliminary results showed that the specific energy consumption of a small scale plasma reformer can be effectively reduced through efficient thermal management and heat recycling (Bromberg et al., 2000). The characteristics of hydrogen production from isooctane were studied and reported that hydrogen yield at catalyst temperatures as high as 800oC was significantly improved by using a combined plasma/catalytic system (Sobacchi et al., 2002). Some researchers investigated autothermal reforming of methane and propane by 2 wt%-catalysts on alumina support. They proposed the activity level of the catalysts in descending order as: Rh > Pd > Ni > Pt > Co. They demonstrated that high activity was achieved by loading suitable amount of Ni, while under the same loading, activity was higher for the Rh-based catalyst (Ayabe et al., 2003). A plasma catalytic reactor was employed for the combined oxygensteam reforming of methane. It was found that by combining the dielectric barrier discharge (DBD) and a Ni catalyst the conversion of methane was not improved, but complete conversion of oxygen was achieved. Under a suitable temperature to maintain the Ni catalytically active, the product selectivities changed significantly (Pietruszka & Heintze, 2004). Preparation of intake mixture for reforming performance was investigated. It showed that feeding fuel via an intake swirl significantly facilitated the conversion efficiency of methane, and elevated the concentration of hydrogen. Both higher arc frequencies and longer retention time improving hydrogen concentration were also confirmed (Horng et al., 2007). The plasma converter on hydrogen production via methane reforming and the carbon deposit growth on the electrode surface were explored, and the microstructure of carbon was analyzed with scanning electron microscopy (SEM) and micro-Raman spectroscopy (Horng et al., 2006a). The reforming of aliphatic hydrocarbon such as methane, propane and neopentane, using non-thermal plasma was carried out. It demonstrated that reforming by combining carbon dioxide with methane and propane, yielded a higher H2/CO ratio than using neopentane. When using steam reforming, methane yielded the highest H2/CO ratio (Futamura et al., 2006). The literature on the field of hydrogen production assisted by nonthermal plasma reforming was reviewed by a group of researchers. They concluded that most of the existing reforming reactors were still being developed and advanced in research laboratories (Petitpas et al., 2007). The Tokyo Institute of Technology studied the plasma and the glid-arc reforming approaches and found that both of them required high temperature to produce hydrogen. In contrast, the dielectric barrier discharge (DBD) reforming approach could produce hydrogen at lower temperatures (between 400 and 600 °C) by adding water

Concerning the heat regeneration, a high energy level of thermal plasma to accelerate the reforming reaction was studied. It was suggested that the methods of heat insulation, heat regeneration and improved plasma catalysis could reduce the energy loss and improve methane conversion efficiency (Bromberg et al., 1999b). The utilization of phase change material (PCM) for heat-recovery was experimentally studied. Copper balls as the PCM were encapsulated by nickel film with/without an insertion of carbon or ruthenium as an inhibition layer. The results showed that the copper PCM with the thick film of nickel and an inactive layer between nickel and copper was available for producing hydrogen by hightemperature waste heat recovery (Maruoka et al., 2002). A high temperature plasma technique was applied on the reforming of methane or other hydrocarbon fuels to produce hydrogen-rich gas. To reduce energy loss and to increase methane conversion, heat could be insulated and exchanged at the plasma converter. Thermal efficiency of partial oxidation

vapor in fuel (Nozaki & Okazaki, 2005).

reforming using external heating from the perspective of thermodynamics was studied. It was revealed that higher O/C ratios resulted in low thermal efficiency as a significant amount of fuel was found to be oxidated in the reforming process (Lutz et al., 2004). The reforming of exhaust gas recirculation (EGR) for producing H2 and CO was studied. By adding the contents of H2 and CO, the in-cylinder premixed combustion of engine would be enhanced; and then a super lean burn process, low NOx operations could be achieved (Zheng et al., 2004). A numerical simulation on the technique of pure external heating and the method of reusing partial oxidation produced through external heating of hydrogen were used for investigating thermal efficiency. The former was found to be of higher efficiency, which was enhanced with increasing H2O/Carbon ratio (Lutz et al., 2003). A small scale hydrogen producing system was designed with utilizing heat exchange to heat up the vapourising unit. The reforming thermal efficiency attained was as high as 78% while the methane conversion efficiency was 89%, capable of supplying a 1kW fuel cell (Seo et al., 2006). Dimethyl ether (DME) and methanol-reformed gas (MRG) were produced from methanol by onboard reformers utilising the exhaust heat from the engine. Because the reactions producing DME and MRG are endothermic, a part of exhaust heat energy can be recovered during the fuel reforming process. This research experimentally investigated characteristics of combustion, exhaust emissions, engine efficiency and overall thermal efficiency including the waste heat recovery through the fuel reforming in the HCCI combustion engine system (Shudo, 2006). Tri-reforming of natural gas using flue gas from power plants with the combination of heat transfer or heat exchange including reactor heat up and waste heat utilization was studied. The tri-reforming process could be applied to the production of synthetic gas by reforming of natural gas using gas mixtures (containing CO2, H2O, and O2) as co-feeds. As a result, the mitigation of CO2 could be achieved by waste heat recovery. However, various strategic considerations, technical approaches, and specific research directions have been presented. More research is necessary towards effective CO2 conversion into useful substances using renewable sources of energy (Song, 2006). The hydrogen production from low carbon fuels by using the plasma-catalyst hybrid converters with energy conservation was investigated. The energy saving schemes, namely, heat recycling and heat insulation were applied to enhance the hydrogen production. The results showed that the energy saving systems enabled the O2/C ratio to be decreased to reduce oxidation of hydrogen and carbon monoxide and thereby improving the concentration of hydrogen-rich gas. By heat recycling, the improvement in methane conversion efficiency in a lower fuel feeding rate was achieved; moreover, the hydrogen production increased significantly with the water-gas shifting reaction under the same operation parameters (Horng et al., 2008a, 2009). System analysis was conducted on a combined system for methane steam reforming comprising conventional hydrogen production and waste heat recovery from steelmaking. The results showed that the factors evaluated including the natural gas consumption, enthalpy flow, CO2 emission, cost, and exergy loss were improved for the waste heat recovery system. This supports the feasibility of hydrogen production from recovered waste heat. Moreover, the proposed system is expected to produce less CO2 emission due to less fuel consumption (Maruoka et al., 2010).

Combustion principles state that hydrogen has a high heating value and a high flame speed. If hydrogen can maintain the normal combustion efficiency in engine even at an extremely lean mixture, it would reduce fuel consumption and exhaust emissions. A small

Waste Heat Recycling for Fuel Reforming 359

An on-board plasmatron converter was used for hydrocarbon fuel reforming. The study proved that both high carbon and low carbon fuels could efficiently generate hydrogen-rich gas; and once it was directed into the engine, the thermal efficiency and NOx and CO emissions of the engine were evidently improved (Rabinovich et al., 1994). The investigation on the exhaust gas reforming of gasoline was carried out. The reformed fuel was fed to an engine as an additive to gasoline. The study on the effects of reformed fuel addition on engine performance at extreme lean burn conditions was performed. Results showed that low levels of NOx and HC emissions were achieved with the improved thermal efficiency and extended lean burn operation (Jamal et al., 1996). The hydrogen producing systems for powering vehicles were explored. The characteristics of different fuels on reducing exhaust emissions were compared and reported that the shape design of a reaction chamber could improve thermal management, reduce heat lost and optimize incubation time (Bromberg et al., 1999a). Hydrogen-rich gas produced from a plasmatron fuel converter with the exhaust gas recirculation (EGR) approach was directed into an internal combustion engine. The results showed that the NOx emission was evidently reduced with low level of HC emission

In summary, a fuel reformer for hydrogen production is to be a promising way in the future; and it would be one of the directions for application in internal combustion engines and fuel cells. This study attempts to develop a set of plasma fuel converter with waste heat recycling. The reformation of methane for hydrogen production is investigated, and the results are anticipated to serve as a reference for future research on the reformation of other fuels, including natural gas, or biogas. The application of this system is expected to improve the thermal efficiency and the exhaust emissions of engines. Additionally, the applications of fuel converters on fuel cells would be becoming popular. The stationary fuel converters could be applied for producing hydrogen on solid oxide fuel cells (SOFC). As for the portable fuel cells, if the purity of reformate gas can be achieved, the portable hydrogen generating device could be carried onboard vehicles directly to power vehicles with proton

This study focuses on the energy conservative plasma fuel converters with waste heat recycling; a photo and a schematic diagram of the experimental equipment of the system are shown in Fig. 1 and Fig. 2, respectively. The reaction chamber was comprised of three subsystems: the fuel and gas supply system, the arc generation system, and the reformate gas sampling and analyzing system. The fuel and gas supply system was comprised a fuel nozzle and a flow meter. For the arc generation system, a car ignition system was used with a signal generator and an induction coil to generate arc. Converting car ignition system into a small high voltage DC power supply is practical, as it enabled the system to be directly equipped on-board, and the use of the existing equipment reduced the required space and cost of power supply. The anode of the sparking electrode was constructed by removing the earth electrode of spark plug, while the cathode was the reaction chamber itself. The

under cold-start of the engine (Bromberg et al., 2001).

exchange membrane fuel cells (PEMFC).

**2.1 Experimental equipment** 

**2. Experimental equipment and methodology** 

specifications of the arc generating system are shown in Table 1 (a).

plasma fuel reformer was used to ionize the mixture of gasoline and air, and the reformate gas was directed into the internal combustion engine. The results clearly indicated that the low levels of NOx, CO and HC were obtained simultaneously (Cohn et al., 1996). The combustion characteristics of a hydrogen-gasoline mixture via mathematical models were explored. It was obtained that the best thermal efficiency was acquired at 8.0 % of hydrogen by mass, and the specific energy consumption was significantly improved at 10 % of hydrogen by mass. It also found that most of the pollutants emitted by engines were produced during the cold-start and warming-up processes. Using hydrogen-rich gas produced by fuel converters as an auxiliary fuel for the engine, or using it with catalysts in the exhaust pipes for rapidly heating the engine would greatly increase the energy using efficiency during the cold start and warming up; it would also reduce the emission of pollutants during the cold start of the engine, and reduce the emission of NOx, CO, and HC in the driving condition of the vehicle (Al-Janabi & Al-Baghdadi, 1999). The performance of hydrogen fueled carbureted and fuelinjected SI engine was compared. The results revealed that the fuel-injected engine gave better output power and had a lower risk of backfiring (Verhelst & Sierens, 2001). Recycled exhaust and added methane and air for reforming with a honeycomb catalyst was studied on an HCCI (Homogenous Charge Compression Ignition) engine. By reusing the heat from the exhaust and adding external heat for partial oxidation reforming, steam reforming and water-gas shifting, the effect of temperature on reformate gas concentration and fuel conversion efficiency was investigated (Peucheret et al., 2005).

A set of small plasma fuel converter was designed for hydrogen production and applied on a 4-stroke motorcycle with a heat storing catalyst in the exhaust pipe to reduce exhaust emission. The results demonstrated that the exhaust emissions produced by the engine were extremely low in the cold-start process (Horng et al., 2006b). The driving performance and exhaust emission characteristics of a 125cc motorcycle equipped with an onboard plasma reformer for producing hydrogen-rich gas was investigated. The produced hydrogen-rich gas was induced into the internal combustion engine as supplementary fuel. It showed that the NOX emission was improved by 56.8% under a constant speed of 40 km/h. During transient driving condition, the improvement of 16%- 41% in NOX concentration was achieved. The emissions of the motorcycle were also analysed on a chassis dynamometer tracing an ECE-40 driving pattern. The NOX emission was improved by 34%, as was the HC emission by 4.08%, although the CO emission was increased (Horng et al., 2008b). The performance of an engine by fuel injection with hydrogen was investigated, and the results showed that the knocking and backfiring were absent. The experiments included three operating parameters, namely, ignition timing, injection timing and equivalence ratio, all of which were optimised for the engine performance in terms of good thermal efficiency, good brake mean effective pressure, and low NOx emission (Mohammadi et al., 2007). The effect of hydrogen addition to a natural gas engine on engine performance and emission was studied. The results showed that adding hydrogen in lean burn condition could improve the thermal efficiency of engine with reducing the CO and HC emissions. However, an increase in NOx emission was obtained in the process due to the increase in the combustion temperature. They further showed that by modifying the ignition timing, the NOx emission could be reduced to that similar to the original fuelling system (Ma et al., 2007).

plasma fuel reformer was used to ionize the mixture of gasoline and air, and the reformate gas was directed into the internal combustion engine. The results clearly indicated that the low levels of NOx, CO and HC were obtained simultaneously (Cohn et al., 1996). The combustion characteristics of a hydrogen-gasoline mixture via mathematical models were explored. It was obtained that the best thermal efficiency was acquired at 8.0 % of hydrogen by mass, and the specific energy consumption was significantly improved at 10 % of hydrogen by mass. It also found that most of the pollutants emitted by engines were produced during the cold-start and warming-up processes. Using hydrogen-rich gas produced by fuel converters as an auxiliary fuel for the engine, or using it with catalysts in the exhaust pipes for rapidly heating the engine would greatly increase the energy using efficiency during the cold start and warming up; it would also reduce the emission of pollutants during the cold start of the engine, and reduce the emission of NOx, CO, and HC in the driving condition of the vehicle (Al-Janabi & Al-Baghdadi, 1999). The performance of hydrogen fueled carbureted and fuelinjected SI engine was compared. The results revealed that the fuel-injected engine gave better output power and had a lower risk of backfiring (Verhelst & Sierens, 2001). Recycled exhaust and added methane and air for reforming with a honeycomb catalyst was studied on an HCCI (Homogenous Charge Compression Ignition) engine. By reusing the heat from the exhaust and adding external heat for partial oxidation reforming, steam reforming and water-gas shifting, the effect of temperature on reformate gas concentration and fuel conversion efficiency was investigated (Peucheret et al., 2005).

A set of small plasma fuel converter was designed for hydrogen production and applied on a 4-stroke motorcycle with a heat storing catalyst in the exhaust pipe to reduce exhaust emission. The results demonstrated that the exhaust emissions produced by the engine were extremely low in the cold-start process (Horng et al., 2006b). The driving performance and exhaust emission characteristics of a 125cc motorcycle equipped with an onboard plasma reformer for producing hydrogen-rich gas was investigated. The produced hydrogen-rich gas was induced into the internal combustion engine as supplementary fuel. It showed that the NOX emission was improved by 56.8% under a constant speed of 40 km/h. During transient driving condition, the improvement of 16%- 41% in NOX concentration was achieved. The emissions of the motorcycle were also analysed on a chassis dynamometer tracing an ECE-40 driving pattern. The NOX emission was improved by 34%, as was the HC emission by 4.08%, although the CO emission was increased (Horng et al., 2008b). The performance of an engine by fuel injection with hydrogen was investigated, and the results showed that the knocking and backfiring were absent. The experiments included three operating parameters, namely, ignition timing, injection timing and equivalence ratio, all of which were optimised for the engine performance in terms of good thermal efficiency, good brake mean effective pressure, and low NOx emission (Mohammadi et al., 2007). The effect of hydrogen addition to a natural gas engine on engine performance and emission was studied. The results showed that adding hydrogen in lean burn condition could improve the thermal efficiency of engine with reducing the CO and HC emissions. However, an increase in NOx emission was obtained in the process due to the increase in the combustion temperature. They further showed that by modifying the ignition timing, the NOx emission could be reduced to that

similar to the original fuelling system (Ma et al., 2007).

An on-board plasmatron converter was used for hydrocarbon fuel reforming. The study proved that both high carbon and low carbon fuels could efficiently generate hydrogen-rich gas; and once it was directed into the engine, the thermal efficiency and NOx and CO emissions of the engine were evidently improved (Rabinovich et al., 1994). The investigation on the exhaust gas reforming of gasoline was carried out. The reformed fuel was fed to an engine as an additive to gasoline. The study on the effects of reformed fuel addition on engine performance at extreme lean burn conditions was performed. Results showed that low levels of NOx and HC emissions were achieved with the improved thermal efficiency and extended lean burn operation (Jamal et al., 1996). The hydrogen producing systems for powering vehicles were explored. The characteristics of different fuels on reducing exhaust emissions were compared and reported that the shape design of a reaction chamber could improve thermal management, reduce heat lost and optimize incubation time (Bromberg et al., 1999a). Hydrogen-rich gas produced from a plasmatron fuel converter with the exhaust gas recirculation (EGR) approach was directed into an internal combustion engine. The results showed that the NOx emission was evidently reduced with low level of HC emission under cold-start of the engine (Bromberg et al., 2001).

In summary, a fuel reformer for hydrogen production is to be a promising way in the future; and it would be one of the directions for application in internal combustion engines and fuel cells. This study attempts to develop a set of plasma fuel converter with waste heat recycling. The reformation of methane for hydrogen production is investigated, and the results are anticipated to serve as a reference for future research on the reformation of other fuels, including natural gas, or biogas. The application of this system is expected to improve the thermal efficiency and the exhaust emissions of engines. Additionally, the applications of fuel converters on fuel cells would be becoming popular. The stationary fuel converters could be applied for producing hydrogen on solid oxide fuel cells (SOFC). As for the portable fuel cells, if the purity of reformate gas can be achieved, the portable hydrogen generating device could be carried onboard vehicles directly to power vehicles with proton exchange membrane fuel cells (PEMFC).
