Effect of Hydroxy HHO Gas Addition on Performance

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  See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/223432759 Effect of hydroxy (HHO) gas addition onperformance and exhaust emissions incompression ignition engines  Article   in  International Journal of Hydrogen Energy · October 2010 DOI: 10.1016/j.ijhydene.2010.07.040 CITATIONS 33 READS 1,766 3 authors , including:Kadir AydinCukurova University 53   PUBLICATIONS   458   CITATIONS   SEE PROFILE All content following this page was uploaded by Kadir Aydin on 10 January 2016. The user has requested enhancement of the downloaded file. All in-text references underlined in blue are added to the srcinal documentand are linked to publications on ResearchGate, letting you access and read them immediately.  Effect of hydroxy (HHO) gas addition on performance andexhaust emissions in compression ignition engines  Ali Can Yilmaz, Erinc¸ Uludamar, Kadir Aydin* Department of Mechanical Engineering, C¸ukurova University, 01330 Adana, Turkey a r t i c l e i n f o Article history: Received 8 May 2010Received in revised form5 July 2010Accepted 5 July 2010Available online xxx Keywords: HydrogenHydroxyEnrichmentCombustionPerformanceEmissions a b s t r a c t In this study, hydroxy gas (HHO) was produced by the electrolysis process of differentelectrolytes (KOH (aq) , NaOH (aq) , NaCl (aq) ) with various electrode designs in a leak proof plexiglass reactor (hydrogen generator). Hydroxy gas was used as a supplementary fuel ina four cylinder, four stroke, compression ignition (CI) engine without any modification andwithout need for storage tanks. Its effects on exhaust emissions and engine performancecharacteristics were investigated. Experiments showed that constant HHO flow rate at lowengine speeds (under the critical speed of 1750 rpm for this experimental study), turnedadvantages of HHO system into disadvantages for engine torque, carbon monoxide (CO),hydrocarbon (HC) emissions and specific fuel consumption (SFC). Investigations demon-strated that HHO flow rate had to be diminished in relation to engine speed below 1750 rpmdue to the long opening time of intake manifolds at low speeds. This caused excessivevolume occupation of hydroxy in cylinders which prevented correct air to be taken into thecombustion chambers and consequently, decreased volumetric efficiency was inevitable.Decreased volumetric efficiency influenced combustion efficiency which had negativeeffectsonenginetorqueandexhaustemissions.Therefore,ahydroxyelectroniccontrolunit(HECU)wasdesignedandmanufacturedtodecreaseHHOflowratebydecreasingvoltageandcurrentautomaticallybyprogrammingthedataloggertocompensatedisadvantagesofHHOgas on SFC, engine torque and exhaust emissions under engine speed of 1750 rpm. The flowrate of HHO gas was measured by using various amounts of KOH, NaOH, NaCl (catalysts).These catalysts were added into the water to diminish hydrogen and oxygen bonds andNaOH was specified as the most appropriate catalyst. It was observed that if the molality of NaOH in solution exceeded 1% by mass, electrical current supplied from the batteryincreased dramatically due to the too much reduction of electrical resistance. HHO systemaddition tothe enginewithout any modification resultedinincreasing enginetorqueoutputby an average of 19.1%, reducing CO emissions by an average of 13.5%, HC emissions by anaverage of 5% and SFC by an average of 14%. ª  2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved. 1. Introduction Faced with the ever increasing cost of conventional fossilfuels, researches worldwide are working overtime to cost-effectively improve internal combustion engine (ICE) fueleconomy and emission characteristics. In recent years, manyresearchers have focused on the study of alternative fuelswhich benefit enhancing the engine economic and emissions *  Corresponding author . Tel.:  þ 90 5335107585; fax:  þ 90 3223386126.E-mail address: kdraydin@cu.cdu.tr (K. Aydin). Available at www.sciencedirect.comjournal homepage: www.elsevier.com/locate/he international journal of hydrogen energy xxx (2010) 1 e 7 Please cite this article in press as: Ali Can Yilmaz, et al., Effect of hydroxy (HHO) gas addition on performance and exhaustemissions in compression ignition engines, International Journal of Hydrogen Energy (2010), doi:10.1016/j.ijhydene.2010.07.040 0360-3199/$  e  see front matter  ª  2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.doi:10.1016/j.ijhydene.2010.07.040  characteristics. The main pollutants from the conventionalhydrocarbon fuels are unburned/partially burned hydro-carbon (UBHC), CO, oxides of nitrogen (NO x ), smoke andparticulate matter. It is very important to reduce exhaustemissions and to improve thermal efficiency. The higherthermal efficiency of diesel engines certainly has advantagesfor conserving energy and also solving the greenhouseproblem. Among all fuels, hydrogen is a long term renewable,recyclable and non-polluting fuel. Hydrogen has some pecu-liar features compared to hydrocarbon fuels, the most signif-icant being the absence of carbon. Very high burning velocityyields very rapid combustion and the wide flammability limitof hydrogen varies from an equivalence ratio ( f ) of 0.1 e 7.1,hencethe enginecan beoperated witha wide rangeofair/fuelratio. The properties of hydrogen are given in Table 1 [1]. Due to the low ignition energy and wide flammable range of hydrogen, hydrogen engines are quite suitable to run at leanconditions which are helpful for the enhanced engineeconomic and emissions performance [2,3]. All regulated pollutant emissions, except nitrogen oxides, can be simplyreduced by using a carbon-free fuel. This is true whatever thealternative fuel source if the production of this carbon-freefuel in large plants is more efficient and therefore producesless CO 2  than the direct conversion of the fuel source intomechanical power in the internal combustion engine. Thecombination of its molecular composition and some of itspeculiar properties (high laminar flame speed, wide flamma-bility range, etc.) reveals hydrogen as an attractive fuel forICEs [4]. Besides, compared with traditional fossil fuels,hydrogen is a carbonless fuel whose combustion doesn’tgenerate emissions such as HC, CO and CO 2  [5].The concept of using hydrogen as an alternative fuel fordiesel engines is recent. The self ignition temperature of hydrogen is 858 K, so hydrogen cannot be used directly in a CIengine without a spark plug or glow plug. This makeshydrogen unsuitable as a sole fuel for diesel engines [1]. Thereare several reasons for applying hydrogen as an additionalfuel to accompany diesel fuel in CI engine. Firstly, it increasesthe H/C ratio of the entire fuel. Secondly, injecting smallamounts of hydrogen to a diesel engine could decreaseheterogeneity of a diesel fuel spray due to the high diffusivityof hydrogen which makes the combustible mixture betterpremixed with air and more uniform. It could also reduce thecombustion duration due to hydrogen’s high speed of flamepropagation in relation to other fuels [6].Throughout history, there have been many studiesregarding hydrogen as a fuel in ICEs. First, Reverend Cecil inEngland planned to use hydrogenas fuel in 1820. Bursanti andMatteucci in Italy improved the hydrogen engine with a freepiston in 1854. Rudolf Erren conducted studies with thehydrogen engine in Germany in 1920. Ricardo achieved highefficiency when working with hydrogen in an engine in 1924[7]. In 1992, as a result of the Second World Renewable EnergyCongress held in Reading, the world renewable energynetwork (WREN) has been formed. The first author of thispaper is the founder member of WREN. This network isdedicated to promoting renewable energy throughout theworld [8]. Also, there have been many investigations onhydrogen-enriched fuel operation in ICEs. Saravanan andNagarajan [9] experimentally investigated the hydrogen-enriched air induction in a diesel engine system. The testresults showed that an efficiency of 27.9% was achievedwithout knocking over the entire load range with 30%hydrogen enrichment. Also, they observed that specific fuelconsumptiondecreasedwithincreaseinhydrogenpercentageover the entire range of operation. Saravanan et al. [10] did anexperimental investigation on hydrogen as a dual fuel fordiesel engine system with exhaust gas recirculation (EGR)technique. The test results demonstrated that the SFCdecreased without EGR with 20 L/min of hydrogen flow andthey concluded that the reason for reduction in SFC is due tothe operation of hydrogen fueled engine under lean burnconditions. Masood et al. [11] studied on experimental verifi-cation of computational combustion and emission analysis of hydrogen e diesel blends and the test results showed that thehydrogen e diesel co-fueling solved the drawback of leanoperation of hydrocarbon fuels such as diesel, which werehard to ignite and resulted in reduced power output, byreducingmisfires,improvingemissions,performanceandfueleconomy. Saravanan and Nagarajan [12] studied on anexperimental investigation on optimized manifold injectionin a direct-injection diesel engine with various hydrogenflowrates. The test results showed that in the manifoldinjection technique, the optimized condition was the start of injection at gas exchange top dead center (TDC) with injectionduration of 30  crank angle (CA) with a hydrogen flow rate of  Table 1  e The properties of hydrogen. Properties Diesel Unleaded gasoline Hydrogen Autoignition temperature (K) 530 533 e 733 858Minimum ignition energy (mJ)  e  0.24 0.02Flammability limits (volume % in air) 0.7 e 5 1.4 e 7.6 4 e 75Stoichiometric air-fuel ratio on mass basis 14.5 14.6 34.3Limits of flammability (equivalence ratio)  e  0.7 e 3.8 0.1 e 7.1Density at 16   C and 1.01 bar (kg/m 3 ) 833 e 881 721 e 785 0.0838Net heating value (MJ/kg) 42.5 43.9 119.93Flame velocity (cm/s) 30 37 e 43 265 e 325Quenching gap in NTP air (cm)  e  0.2 0.064Diffusivity in air (cm 2  /s)  e  0.08 0.63Research octane number 30 92 e 98 130Motor octane number  e  80 e 90  e international journal of hydrogen energy xxx (2010) 1 e 7 2 Please cite this article in press as: Ali Can Yilmaz, et al., Effect of hydroxy (HHO) gas addition on performance and exhaustemissions in compression ignition engines, International Journal of Hydrogen Energy (2010), doi:10.1016/j.ijhydene.2010.07.040  7.5 L/min. The brake thermal efficiency was increased by 9%compared to pure diesel fuel operation. CO emissions variedfrom 0.03 to 0.12 vol% compared to 0.08 e 0.14 vol% in a dieselfuel investigation. Naber and Siebers [13] successfully inves-tigated the hydrogen autoignition process under dieselconditions. The autoignition of hydrogen was investigated ina constant-volume combustion vessel. The varied parameterswere as follows: the injection pressure and temperature, theorifice diameter, and the ambient gas pressure, temperatureand composition. They obtained a strong Arrhenius correla-tionbetweenignitiondelayandtemperature.Senthiletal.[14]conducted research on applying hydrogen to improvecombustion of vegetable oil in a diesel engine. In their work,experiments were conducted to evaluate the engine perfor-mance while using small quantities of hydrogen ina compression ignition engine primarily fueled with a vege-table oil, namely Jatropha oil. Results indicated an increase inthe brake thermal efficiency from 27.3% to a maximum of 29.3% at 7% of hydrogen mass share at the maximum poweroutput. They also noticed significant smoke reduction by 20%.There was also a reduction in HC and CO emissions from 130to 100 ppm and 0.26 e 0.17% (by volume), respectively, atmaximum power output.TheabilityforH 2 ICEstoburncleanlyandoperateefficientlyis owed to the unique combustion characteristics of hydrogenthat allow ultra-lean combustion with dramatically reducedNO x  production and efficient low-engine load operation. Incontrast, the same combustion characteristics impose tech-nical challenges at high engine-loads due to an increasedpropensity to preignite the hydrogen e air mixture [15]. At lowloads, the load can be controlled by the equivalence ratio(qualitative approach), as combustion temperatures then staybelow the NO x  formation temperature. The engine is then rununderwideopenthrottleconditions,sothatpumpinglossesarenegligible which benefits the brake thermal efficiency.However, hydrogen may cause some problems at high engine-loads [16]. Hydrogen has high autoignition temperaturecompared to diesel and this causes some challenges on oper-ating a diesel engine just by increasing compression ratio.Therefore,aglowplugorasparkplug(externalignitionsources)shouldbeoftenused.Alsohydrogenusageasasolefuelinsparkignitionenginebrings some disadvantagestobeovercomelikebackfire, pre-ignition and knock. Therefore, hydrogen controlin engine should be managed by an electronic system. Sincehydrogen has the smallest molecular size and is the lightestelementinnature,itsstoragebecomesacrucialproblem.Whileelectrochemically reacting hydrogen in fuel cells is consideredto bethecleanest and mostefficientmeans ofusinghydrogen,it is believed by many to be a technology of the distant future.Currently, fuel cell technology is expensive and bulky. In thenear term, the use of hydrogen in an ICE may be feasible asalow-costtechnologytoreduceemissionsofcriteriapollutantsand global warming via carbon dioxide (CO 2 ) [17].The aim of this experimental investigation was, to makea spectacularcombination ofanodesandcathodesin a simplyadaptable ambient within the fuel system and to obtain anenhancement in combustion and reduction in exhaust emis-sions with electrolysis reaction without the need for storagetanks. In this experimental study, instead of pure hydrogenaddition to diesel fuel, produced hydrogen gas along withoxygen (hydroxy gas, HHO, Brown’s gas) was fed to the intakemanifold of a direct-injection CI engine by a hydroxy systemand a hydroxy electronic control unit (HECU) under variousloads, which caused engine speed to decrease from 2800 to1200 rpm. Hydroxy gas is in brown color and the form of unseparated hydrogen and oxygen generated by the electrol-ysis process of water (NaOH, KOH or NaCl additives for moreHHO production and optimum molality to keep electricalresistance-conductivitybalance)byauniqueelectrodedesign.Hydrogen and oxygen did not form into O 2  and H 2  molecules.They were in their monoatomic state (a single atom permolecule). Water was split by electricity to form its variouselements, oxygen and hydrogen. When HHO mixture wasignited, both explosion and implosion occured to form water,releasing the energy that was found in the bonds of the twoelements in the form of heat. In the monoatomic portion,there weren’t any atomic bonds needed to be broken (thebonds of the H 2  and O 2  respectively) before turning back intowater.ThekeydifferenceofHHOgaswasthefactthatsomeof the hydrogen and oxygen never go into a diatomic state.Hence, HHO gas had more energy because these bonds werenever made. In this state, which was an unstable state of H 2 Ovapor, more energy was achieved compared to hydrogenburning with oxygen. Pulverized water clashed the fuel andthey united. Water became the core and the fuel tended to bethe water shell (due to density difference). During compres-sion stroke, pressure and heat increased, the water explodedto steam and consequently, the fuel got atomized. After igni-tion, in-cylinder temperature increased rapidly which resul-ted water to be splitted into hydrogen and oxygen andreigniton occured which yielded increased combustion effi-ciency. Due to the oxgen atoms coming out with hydrogen(monoatomic structure), autoignition temperature of hydroxywas not as high as hydrogen (diatomic structure). Thus,hydroxy gas did not need an external ignition source likespark or glow plug and due to the simultaneous productionand consumption of hydrogen; no storage was necessary,which resulted in safe operation [18]. Hydroxy gas wasgenerated and used as a sole fuel in diesel engine to benefitfrom peculiar features and minimize disadvantages of hydrogen. It was observed that hydroxy system providedadvantages in engine performance, emissions and specificfuel consumption at high engine speeds under lean condi-tions. At mid and low speeds, these specifications turned intodisadvantages, due to minimum ignition energy of hydroxywhich is a strongly decreasing function of equivalence ratio,pre-ignition and knock occured. Also, low lean-flammabilitylimit of hydroxy resulted advantages only under dilute (lean)conditions unless HECU was added to the HHO system.Experiments without HECU demonstrated that, compared topure diesel fuel operation, engine torque was increased by anaverage of 27.1% above the engine speed of 1750 rpm anddecreased by an average of 46.9% under 1750 rpm. An averagereduction of 23.8% ( > 1750 rpm) and increment of 22.7%( < 1750 rpm) in HC emissions were observed. An average of 2.1% ( > 1750 rpm) reduction and 4.6% ( < 1750 rpm) incrementwere observed for CO emissions. The average values for SFCwere 13% reduction above 1750 rpm and 15.8% incrementbelow 1750 rpm. Average values, obtained from experimentswith HECU addition to the hydroxy system, were 19.1% international journal of hydrogen energy xxx (2010) 1 e 7  3 Please cite this article in press as: Ali Can Yilmaz, et al., Effect of hydroxy (HHO) gas addition on performance and exhaustemissions in compression ignition engines, International Journal of Hydrogen Energy (2010), doi:10.1016/j.ijhydene.2010.07.040
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