Design and Manufacture of ICE Test Module to Reduce Gasoline

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Design and Manufacture of ICE Test Module to Reduce Gasoline Consumption Using Oxyhydrogen Gas from an Alkaline Electrolyzer M. Horcasitas-Verdiguel,†,‡ J. M. Sandoval-Pineda,† B. A. Grunstein-Ramírez,§ L. F. Terán-Balaguer,∥ and R. de G. González-Huerta*,‡ †

Instituto Politécnico Nacional-ESIME-Azc, SEPI, Av. De las Granjas, No. 682, Azcapotzalco, CP 02250, México, CDMX Instituto Politécnico Nacional -ESIQIE, Laboratorio de Electroquímica y Corrosión, UPALM, CP 07738, México, CDMX § Instituto Politécnico Nacional-UPIITA, Av. IPN 2580, CP 07340, México, CDMX ∥ Xantronic S.A. de C.V., Rafael Campoy 811, Col. Pitic, CP 83150, México, Hermosillo-Sonora ‡

ABSTRACT: Internal combustion engine (ICE) vehicles are an important source of pollution gases; therefore, several research groups are implementing systems to reduce hydrocarbon emissions. Gasoline enrichment with alternative fuels such as ethanol, hydrogen, and others has been considered. This paper investigates the effect of a hydrogen−oxygen mixture (oxyhydrogen gas) injected to a gasoline ICE. The test module was adapted to a modified ICE with a hydrogen and oxygen intake system which is controlled by an electronic unit. Oxyhydrogen gas (OH2G) was produced by two water alkaline electrolyzers (WAEs) in a combined parallel-series arrangement, and their energy consumption ranged from 60 to 500 W with efficiency values between 50 and 65%. The WAEs used in this study were designed and built by our research group. The engine was working at a typical citydriving speed range from 1000 to 2000 rpm. The experimental work consisted of two main stages: In the first, the engine was tested only with gasoline, and in the second one, an oxyhydrogen gas volume was injected, and the total OH2G real intake in air flow was 903 smL min−1. Finally, the oxyhydrogen gas mixture allowed the reduction of gasoline consumption and contributed to a decrease in CO2 emissions.

1. INTRODUCTION Fossil fuel reserves around the world are somehow limited, and severe environmental pollution has promoted the development of several studies on gasoline economy, their consumption in internal combustion engines (ICEs), and the need for alternative clean and renewable energies. Alternative fuels such as ethanol, hydrogen, and some others have been used in automotive systems. Hydrogen generation offers the possibility of reversing the negative impact generated with the use of fossil fuels expelled to the environment and offers an alternative to meet the current demands of fuel and energy.1,2 The focus is now on the application of hydrogen in two basic forms: in hydrogen fuel cells and in ICEs. A fuel cell converts the chemical energy of the fuel directly into electricity; however, the cost of a PEM fuel cell is still higher than the one of conventional ICEs. Several global events indicate the fact that we are approaching to start an era in which new energy systems will be used; the hydrogen era as a clean and environmentally friendly fuel has started. On the other hand, the limited infrastructure for hydrogen distribution and the high costs for production and storage are obstacles to not allow the popularization of using hydrogen in several types of engines and devices.1−14 Comparatively, engines that use fuel−hydrogen mixtures have a reduced amount of total fuel consumption, providing better combustion and reduced contaminant emissions than the traditional fuel-powered engines.2 Shuofeng et al.1 investigated the performance effect of hydrogen−oxygen mixtures (oxyhydrogen) injected to a spark-ignited (SI) gasoline engine. The experiment was performed on a modified SI engine equipped with a hydrogen and oxygen injection system. The standard © 2016 American Chemical Society

enrichment of hydroxygen contributed to the reduction of HC and CO emissions. Chenglong et al.3 presented a comprehensive review of recent advances and fundamental research on hydrogen-enriched combustion. According to previous studies,4 the on-board hydrogen storage system adds extra weight to vehicles and increases the need of considering more safety issues. In recent years, the hydrogen generator, which produces gas in situ with an electrolysis process, provides a suitable solution for the hydrogen implementation on vehicles; the gas produced during the electrolysis contains oxygen, which is a combustion promoter. This is beneficial to obtain a fast and complete combustion of the fuel−air mixture.1−6 Few articles were found in which the integration of an alkaline electrolyzer to an ICE is considered. It is necessary to establish a small-scale manufacturing process for electrolyzers that can offer design security, installation, and operation of these devices. Alkaline electrolyzers have several availability advantages, flexibility, and high purity. Hydrogen production that uses water electrolysis requires improvements in energy efficiency, safety, durability, operability, and portability and also reduction in costs of installation and operation.

2. EXPERIMENTAL METHODOLOGY 2.1. Design of the Electrolyzer. There are two main electrolyzer groups: alkaline and polymeric.15 The polymeric electrolyzer allows the use of solid electrolytes, which facilitate the production of high purity Received: March 29, 2016 Revised: June 13, 2016 Published: July 14, 2016 6640

DOI: 10.1021/acs.energyfuels.6b00709 Energy Fuels 2016, 30, 6640−6645

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Energy & Fuels

potential problems were identified during the development of the final prototype. Under the APQP analytical methodology, a basic monitoring system was generated to identify each step of the electrolyzer manufacturing process. APQP includes considerations on materials, leaks, corrosion, electrode stacking, and the arrangement of the parallelseries configuration. The initial electrolyzer design requires a parameters diagram. Figure 3 describes the controlled and uncontrolled aspects that have an influence in the electrolyzer performance: design, inputs and outputs of the system, manufacturing, and failures. They will help to identify mistakes, noise, and the control variables. In order to evaluate how acceptable the electrolysis systems are, it is necessary to identify those parameters related to the performance.16 The main parameters should be analyzed. These parameters used for the evaluation of the electrolyzers include:

hydrogen, but requires expensive components. In this study, a water alkaline electrolyzer (WAE) was chosen as the hydrogen generator because the alkaline water electrolysis is one of the easiest way for hydrogen production, offering the advantage of simplicity and lower costs. The challenges to widespread use of alkaline water electrolysis are to reduce energy consumption, cost, and maintenance and to increase reliability, durability, and safety.15,16 Figure 1 illustrates the considerations for the electrolyzers manufacturing process, including design, materials, and security issues.

(a) Cell configurations: bipolar and monopolar configurations, electrodes gap, and flow velocity of the electrolytes. (b) Operating conditions: including voltage, current, temperature, pressure, type and electrolytes concentration, and the stability of electrode material. (c) External requirements: quality of water, gases, and safety standards.

Figure 1. Electrolyzer manufacturing process. A WAE manufacturing process was established by adapting the APQP (Advanced Product Quality Planning) methodology, which is an outline of procedures and techniques used to develop products and prototypes. APQP was used as a guide in the alkaline electrolyzer prototype development.17,18 Figure 2 shows the selected analytical methodology;

Figure 4. Diagram of operating alkaline water electrolysis. A basic water electrolyzer unit is composed by an anode (+), a cathode (−), a power supply, and an electrolyte; they are distributed as shown in Figure 4. After applying the direct current (DC), electrons flow from the negative terminal and the hydrogen production starts. Hydroxide ions (anions) are transferred through the electrolyte solution in the direction to the anode, taking the electrons back to the positive

Figure 2. APQP methodology to design the alkaline electrolyzer.

Figure 3. Parameters diagram. 6641

DOI: 10.1021/acs.energyfuels.6b00709 Energy Fuels 2016, 30, 6640−6645

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Figure 5. Test module schematic. terminal of the DC source. The electrolyzer system was designed to support up to 500 W (according to the APQP), with 4 cells connected in parallel and 4 cells connected in series. The electrolyzer system is composed by two stacks of 25 × 25 × 30 cm in length, height, and width, respectively. A total of 16 stainless steel (304) electrodes (20 × 20 × 2 mm) are in contact with a 5% alkaline (NaOH). This concentration was chosen to avoid drag NaOH, and that gas purification system was simpler. Stainless steel is considered as one of the most suitable electrodes material for alkaline electrolyzers, since it is relatively chemically stable, cheap, and with low overpotential (catalytic material for cathodic and anodic reactions); however, stainless steel electrodes do not resist high concentration alkaline solutions because they undergo a corrosion process. Therefore, an electrolyte concentration of 5% was used. The electrolyte reservoir has 400 cm3 per monocell with 1 cm width. The system is connected to a wet trap (electrolyte/bubbles separator) with a volume capacity of 800 cm3. There was no more electrolyte feeding during the electrolyzer operation. The hydrogen gas production ranged from 0.1 L min−1 up to 2.0 L min−1. The performance curve was obtained using a controlled current from 0.1 to 40 A. 2.2. Design and Manufacture of the ICE Test Module. 2.2.1. Design Considerations of the Test Module. Figure 5 shows the components connection used in the experimental test;19 the following operating conditions were considered: (a) Power source: 40 A at 12 V. (b) Available space for installing the alkali electrolyzer: 60 × 30 × 30 cm. (c) Engine type: monocylinder, manufactured by Honda Motors. (d) Engine characteristics: 9.7 Hp@8500 rpm; displacement: 124.1 cc; torque: 8.8 Nm@7500 rpm; and compression ratio 9. Figure 6 shows the theoretical fuel flow and airflow vs rpm of the engine. 2.2.2. Experimental Procedure. The experimentation was composed by the following procedure: First, the engine was operated by 30 min at 1400 rpm to enable stability of performance. Second, the engine was

tested only with gasoline at different rpm; they were 1000, 1200, 1400, 1600, 1800, and 2000 rpm. Third, a standard oxyhydrogen volume fraction was injected at the air intake to compare the effects of OH2G addition. The water alkaline electrolyzer produces hydrogen-to-oxygen, with a mole ratio of 2:1 (standard oxyhydrogen gas, sOH2G). A constant theoretical oxyhydrogen flow of 911 smL min−1 (standard milliliters per minute) was injected. It was observed that the engine accelerates when the oxyhydrogen gas was added; then the gasoline flow was reduced to maintain constant rpm. Finally, the gas combustion was analyzed through the MGA 1200 combustion analysis software considering different rpm. The fraction volume of the standard oxyhydrogen αOH2G in the gas intake was defined with1 αOH2G =

VH2 + VO2 VH2 + VO2 + Vair

100 % (1)

where (VH2 + VO2) is the standard oxyhydrogen volume and Vair is the volume of air fed to the engine. Table 1 shows the air, gasoline, and volume fraction of the standard oxyhydrogen gas calculated for the design of the electrolyzer. Considering Faraday’s law, a current of 160 A was calculated in order to produce 911 cm3 of OH2G. Figure 7 shows the behavior of the gasoline volumetric flow together with the OH2G gas vs rpm of the engine. In theory, a gasoline reduction of 0.18 mL min−1 was achieved when applying 911 smLOH2G min−1 of OH2G to the engine. The master control is in constant communication with four slave modules to control the systems. The slave modules have specific control tasks and generate the information on the flow in the system. Figure 8 shows the general control system diagram.

3. RESULTS AND DISCUSSIONS 3.1. The Electrolyzer System. The arrangement of 4 cells connected in series was used to create a supply current from 10 to 40 A, and the 4 cells connected in parallel were used to supply 10−12 V. Each monocell electrolyzer operates at around 3 V; this is useful to avoid the generation of hazardous six-valent chromium (Cr6+) in the anode. Cr6+ is generated when stainless steel electrodes undergo an oxidation process. Low potential (3 V) and low electrolyte concentration (5%) must be applied to minimize this process. Figure 9 shows the WAE diagram and a photograph of the parallel-series stack experimental arrangement. The typical polarization curve was tested at 25 °C. Figure 10 shows the resulting performance curve of the alkaline electrolyzer stack. The electrolyzer was operated for 100 h, and performance curves were obtained every 10 h. These showed a stable performance (Figure 10). It is important that the test of electrolyzer must be in a ventilated place without flammable materials (solvents, paper, etc.) around the area. The gas produced must be bubbled in distilled water to remove electrolyte dragged.

Figure 6. Theoretical flow of fuel and air supplied to the engine. 6642

DOI: 10.1021/acs.energyfuels.6b00709 Energy Fuels 2016, 30, 6640−6645

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Energy & Fuels Table 1. Gasoline Flow Reduction with Oxyhydrogen Gas Fed (at 20 A and 11.36 V) rpm

gasoline flow real (mL min−1)

gasoline flow with oxyhydrogen (mL min−1)

amount of reduced gasoline flow (mL min−1)

CO2 emission with gasoline (%)

CO2 emission with gasoline and oxyhydrogen gas (%)

1000 1200 1400 1600 1800 2000

2.43 ± 0.08 2.81 ± 0.10 2.96 ± 0.15 3.05 ± 0.14 3.27 ± 0.09 3.91 ± 0.04

2.02 ± 0.08 2.23 ± 0.06 2.36 ± 0.09 2.42 ± 0.07 2.88 ± 0.11 3.11 ± 0.18

0.41 0.57 0.59 0.62 0.38 0.79

4.50 ± 0.26 5.79 ± 0.29 6.65 ± 0.20 7.60 ± 0.20 7.75 ± 0.23

2.33 ± 0.17 3.31 ± 0.31 3.71 ± 0.31 4.20 ± 0.23 5.07 ± 0.27

ηWAE =

E H2 E EC

(2)

where EH2 is the energy produced with the hydrogen and EEC is the energy consumed by the electrolyzer. EH2 (kWh) is calculated using the following equation E H2 =

(P − Pv) 2 298 VOH2G (0.0899)(33) 3 760 (T + 273)

(3)

where VOH2G is the volume of oxyhydrogen produced (L), 2/3 is a constant for considering only the volume of hydrogen produced, P is local pressure (585 mmHg in México City), Pv is the water vapor pressure (18 mmHg), T is the room temperature (25 °C), 0.089 g/L is the hydrogen density, and 33 Wh/g is the specific energy produced by the hydrogen. The theoretical oxyhydrogen gas produced is calculated assuming the hydrogen and oxygen as ideal gases (using eq 3). EEC is the energy consumed by the electrolyzer in kWh, and it was calculated with eq 4

Figure 7. Theoretical graph: rpm vs gasoline volumetric flow vs fraction of the oxyhydrogen added.

The amount of oxyhydrogen gas produced was determined with an Agilent Technologies (ADM) Universal Gas Flowmeter. Energy efficiency relates the amount of energy output with respect to energy input. Another way to evaluate the efficacy of the water electrolyzer is to consider the output of hydrogen production with respect to the total electrical energy applied to the system.16 The WAE efficiency, ηWAE, can be defined by eq 2

E EC = (VE)(IE)(t )

(4)

where VE is the electrolyzer operation voltage, IE is the applied current, and t is the operation time in hours. The efficiency (ηWAE) is an important parameter to compare different electrolyzer technologies. It is a critical criterion to observe either energy or hydrogen production.16 Figure 11 shows the

Figure 8. General control system diagram. 6643

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Figure 9. Water alkaline electrolyzer diagram and picture parallel-series stack.

interface (HMI) displays all the values, and the master controller selects the accelerator position to control the rpm of the engine. The power source includes two modules. One module uses a Pulse Width Modulation (PWM) to control the WAE. The second module has two output cards. They were used to feed each stack. Additionally, it gets data to measure the WAE electric parameters (voltage and power). The digital tachometer is an important component; it transmits to the master controller the engine angular speed and determines the gasoline flow. The last one is a security module, which reads pressure and temperature to maintain safe working conditions. If any parameter goes beyond the limits, the system will stop automatically. Initially, the engine was fed just with gasoline; the system was tested in the automatic mode with a fixed gasoline volume of 10 mL. The time to consume this fuel was monitored at different rpms. The time was measured three times for each rpm, and average values were calculated. Finally, the engine was fed with gasoline and the oxyhydrogen gas, at similar operating conditions, and the obtained readings are shown in Table 1. Experimental results show that, at 20 A and 11.36 V, the electrolyzer system produces 903 smLOH2G min−1 of oxyhydrogen gas and the electrolyzer efficiency corresponds to 50%. Figure 13a shows the gasoline volumetric flow for each rpm, and Figure 13b shows that CO2 emissions are reduced when the oxyhydrogen is fed into the engine. Water is obtained instead.

Figure 10. Performance curve of the alkaline electrolyzer stack.

4. CONCLUSIONS A reduction in the gasoline consumption was observed when hydrogen−oxygen mixtures (oxyhydrogen gas) were injected to an ICE. The manufacturing process of a WAE prototype was established considering the APQP methodology. An experimental module was adapted to a modified ICE, equipped with a hydrogen−oxygen mixture injection system. A PWM based unit was implemented to generate the electric current required for the electrolyzer as well as an HMI unit to display and control the amount of gasoline injected to the ICE. In the experiment, the oxyhydrogen gas was produced by two water alkaline electrolyzers (WAE), one group connected in parallel and the other one in series. The energy consumption ranged from 60 to 500 W, which corresponds to 43−65% of efficiency. In the first stage, the test was performed with only gasoline. In the second stage, a standard oxyhydrogen volume (903 smL min−1) was added to the ICE and the total intake air flow. The oxyhydrogen gas enrichment system allowed the reduction of gasoline consumption. For example, at 1000 rpm, the reduction of gasoline consumption was 0.412 mL min−1, and at 2000 rpm, it was 0.7993 mL min−1. The gasoline engines always exhaust large

Figure 11. WAE efficiency vs electrolyzer power.

obtained ηWAE vs electrolyzer power. An efficiency of around 50% for low temperature (25−60 °C) in alkaline water electrolysis is considered to be good.1 3.2. Test Module Performance. Figure 12a shows the experimental test module, and Figure 12b shows the installation control system.19 The master controller reads data from the slave cards and makes calculations to determine the current value required to produce the oxyhydrogen gas. The human machine 6644

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Figure 12. (a) Test module and (b) control system.

Figure 13. (a) Reduction gasoline flow and (b) CO2 produced with oxyhydrogen. (4) Abdel-Aal, H. K.; Sadik, M.; Bassyouni, M.; Shalabi, M. Int. J. Hydrogen Energy 2005, 30, 1511−1514. (5) Lilik, G. K.; Zhang, H.; Herreros, J. M.; Haworth, D. C.; Boehman, A. L. Int. J. Hydrogen Energy 2010, 35, 4382−4398. (6) Hailin, Li; Karim, G. A. Int. J. Hydrogen Energy 2004, 29, 859−865. (7) Szwaja, S.; Bhandary, K. R.; Naber, J. D. Int. J. Hydrogen Energy 2007, 32, 5076−87. (8) Gomes Antunes, J. M.; Mikalsen, R.; Roskilly, A. P. Int. J. Hydrogen Energy 2008, 33, 5823−28. (9) Gomes Antunes, J. M.; Mikalsen, R.; Roskilly, A. P. Int. J. Hydrogen Energy 2009, 34, 6516−22. (10) Saravanan, N.; Nagarajan, G. Int. J. Hydrogen Energy 2008, 33, 1769−75. (11) Ji, C.; Wang, S.; Zhang, B. Int. J. Hydrogen Energy 2010, 35, 5714− 22. (12) Ji, C.; Wang, S. Int. J. Hydrogen Energy 2009, 34, 3546−56. (13) Ji, C.; Wang, S. Int. J. Hydrogen Energy 2009, 34, 7823−34. (14) Saravanan, N.; Nagarajan, G.; Kalaiselvan, K. M.; Dhanasekaran, C. Renewable Energy 2008, 33, 422−427. (15) Carmo, M.; Fritz, D. L.; Mergel, J.; Stolten, D. Int. J. Hydrogen Energy 2013, 38, 4901−4934. (16) Zeng, K.; Zhang, D. Prog. Energy Combust. Sci. 2010, 36, 307−326. (17) Horcasitas Verdiguel, M. Optimización y manufactura de un electrolizador alcalino para la producción de hidrógeno. Masters Thesis, IPN-ESIME-Azc., Mexico D.F, 2014. ́ (18) Aguilar García, E. Evaluación electroquimica de distintos arreglos de electrolizadores alcalinos. Bachelor Thesis, IPN-ESIQIE, CDMX, Mexico, June 2015. (19) Grunstein-Ramirez, B. A.; Ruiz-Hernandez, E.; Meneses-Rayas, G. D.; González Huerta, R. de G. Design, construction and implementation of electronic control module for the enrichment of hydrogen in combustion engines; XV International Congress of the MHS, CINVESTAV, México, 2015.

amounts of toxic emissions; CO2 emissions are reduced when oxyhydrogen is fed into the engine. In this case, CO2 emissions were replaced by water. The increment of gas contaminants from transportation vehicles is motivating researchers for the use of alternative fuels. Hydrogen offers the greatest potential and benefits for the environment and energy supply. The use of hydrogen/ hydrocarbon fuel mixtures reduces storage and combustion challenges presented when using only hydrogen in ICEs.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Phone: (+52) 55 57296000, ext. 54246. Fax: (+52) 55 57296000, ext. 46140. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work has been supported by multidisciplinary project IPNSIP 1683 (2015-2016) and CONACYT: project PEI 231094 (2016) and Programa de Redes Temáticas/RTH2. Authors thank technical support given by CINVESTAV, Ing. Sebastián Citalán and Dr. Omar Solorza.

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REFERENCES

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DOI: 10.1021/acs.energyfuels.6b00709 Energy Fuels 2016, 30, 6640−6645