Ethanol Fueled Engine Research Articles

Study of the effect of ignition crank angle and mixture composition on the performance of a spark-ignition engine fueled with ethanol

The publication presents the results of the measurements of the operating parameters of a spark-ignition engine fueled with 95-octane unleaded gasoline (ES95) and ethyl alcohol, approx. 92%. The measurements were carried out at a constant load: an engine speed of 1,500 rpm and a constant pressure in the intake system - MAP=0.45 bar. For each type of fuel, the measurements were carried out in two series for two variables. The ignition crank anglewas varied in the range of 0˚÷40˚ and the mixture composition λ in the range of 0.85÷1.25. The recorded engine performance parameters included torque, intake manifold pressure, intake air temperature, exhaust gas temperature and temporal fuel consumption; and exhaust gas composition was examined in terms of carbon monoxide, hydrocarbons and nitrogen oxides. The study showed that an ethanol-fueled engine has lower average efficiency compared to a gasoline one. The highest efficiency for ethanol was obtained for rich mixtures in the range λ=0.85÷1.0 and at high ignition advance angles. The use of alcohol fuel showed a very favorable effect on the composition of exhaust gas and a significantly lower content of harmful exhaust components was demonstrated. For the same operating points, carbon monoxide content was reduced by an average of 15%, and hydrocarbons and nitrogen oxides by an average of 80%.

Hydrogen addition to ethanol-fuelled engine in lean operation to improve fuel conversion efficiency and emissions

This work applies computer simulation to investigate the combined approach of hydrogen (H2) addition with lean operation to enhance the potential of ethanol as a clean engine fuel for low-carbon transportation. To this end, this research evaluates how this operation regime impacts brake power, fuel conversion efficiency, and exhaust emissions. A dedicated software was used to perform a parametric study with varying amount of hydrogen addition and excess air ratio. The software combustion and performance parameters were calibrated against available experimental data and optimised for engine operation at the tested conditions. The results show that hydrogen addition does not produce noticeable effects on brake power and fuel conversion efficiency for lean operation with up to 20% air excess. However, for operation with 40% air excess, 6% H2 addition is necessary to keep the power at the same level of the engine baseline condition while simultaneously improving fuel conversion efficiency. Operation in the range of air excess between 10% and 30% together with hydrogen addition up to 2% can simultaneously produce noticeable improvements of fuel conversion efficiency, carbon monoxide (CO) and hydrocarbon (HC) emissions, without compromising brake power and oxides of nitrogen (NOX) emissions.

Design Optimization of an Ethanol Heavy-Duty Engine Using Design of Experiments and Bayesian Optimization

Abstract Diesel-fueled engines still hold a large market share in the medium and heavy-duty transportation sector. However, the increase in fossil fuel prices and the strict emission regulations are leading engine manufacturers to seek cleaner alternatives without a compromise in performance. Alcohol-based fuels, such as ethanol, offer a promising alternative to diesel fuel in meeting regulatory demands. Ethanol provides cleaner combustion and lower levels of soot due to its chemical properties, in particular its lower level of carbon content. In addition, the stoichiometric operating conditions of alcohol fueled engines enable the mitigation of NOx emissions in aftertreatment stage. With the promise of retrofitting diesel engines to run on ethanol to reduce emissions, the thermal efficiency of these engines remains the primary optimization target. In order to find the optimal ethanol-fueled engine design that maximizes the thermal efficiency, a large design space needs to be investigated using engineering tools. In this study, previous research by the authors on optimizing the design of a single-cylinder ethanol-fueled engine was extended to explore the design space for a heavy-duty multicylinder engine configuration. A heavy-duty engine setup with multiple operating conditions at different engine speeds and loads was considered. A design optimization analysis was performed to identify the potential designs that maximize the indicated thermal efficiency in an ethanol-fueled compression ignition engine. First, a computational fluid dynamics (CFD) model of the engine was validated using experimental data for four drive cycle points. Using a design of experiments (DoE) approach and a parameterized piston bowl geometry, the model was then exercised to explore the relationship among geometric features of the piston bowl and spray targeting angle and indicated thermal efficiency across all tested operating conditions. After evaluating 165 candidate designs, a piston bowl geometry was identified that yielded an increase between 1.3% and 2.2% points in indicated thermal efficiency for all tested conditions, while satisfying the operational design constraints for peak pressure and maximum pressure rise rate. The increased performance was attributed to enhance mixing that led to the formation of a more homogeneous distribution of in-cylinder temperature and equivalence ratio, higher combustion temperatures, and shorter combustion duration. Finally, a Bayesian optimization (BOpt) analysis was employed to find the optimal piston bowl geometry with a fixed spray injector angle for one of the operating conditions. Using BOpt, a piston candidate was identified that resulted in a 1.9% point increase in thermal efficiency from the baseline design, yet only required 65% of the design samples investigated using the DoE approach.

Current Knowledge on Friction, Lubrication, and Wear of Ethanol-Fuelled Engines—A Review

The urgent need for drastic reduction in emissions due to global warming demands a radical energy transition in transportation. The role of biofuels is fundamental to bridging the current situation towards a clean and sustainable future. In passenger cars, the use of ethanol fuel reduces gas emissions (CO2 and other harmful gases), but can bring tribological challenges to the engine. This review addresses the current state-of-the-art on the effects of ethanol fuel on friction, lubrication, and wear in car engines, and identifies knowledge gaps and trends in lubricants for ethanol-fuelled engines. This review shows that ethanol affects friction and wear in many ways, for example, by reducing lubricant viscosity, which on the one hand can reduce shear losses under full film lubrication, but on the other can increase asperity contact under mixed lubrication. Therefore, ethanol can either reduce or increase engine friction depending on the driving conditions, engine temperature, amount of diluted ethanol in the lubricant, lubricant type, etc. Ethanol increases corrosion and affects tribocorrosion, with significant effects on engine wear. Moreover, ethanol strongly interacts with the lubricant’s additives, affecting friction and wear under boundary lubrication conditions. Regarding the anti-wear additive ZDDP, ethanol leads to thinner tribofilms with modified chemical structure, in particular shorter phosphates and increased amount of iron sulphides and oxides, thereby reducing their anti-wear protection. Tribofilms formed from Mo-DTC friction modifier are affected as well, compromising the formation of low-friction MoS2 tribofilms; however, ethanol is beneficial for the tribological behaviour of organic friction modifiers. Although the oil industry has implemented small changes in oil formulation to ensure the proper operation of ethanol-fuelled engines, there is a lack of research aiming to optimize lubricant formulation to maximize ethanol-fuelled engine performance. The findings of this review should shed light towards improved oil formulation as well as on the selection of materials and surface engineering techniques to mitigate the most pressing problems.

Determination of optimum operating parameters of MWCNT-doped ethanol fueled HCCI engine for emission reduction

Carbon based metallic additives were widely researched to improve combustion charecteristics of spark ignition and compression ignition engines. It was proven that carbon nanotube additive shortens ignition delay period and improves combustion characteristics especially in diesel engines. HCCI is a lean burn combustion mode which provides high thermal efficiency and simultaneously low NOx and soot emission. However it has drawbacks such as misfire at leaner mixtures and knocking at high loads. Carbon nanotube could be used to improve combustion for HCCI engines as well. The aim of this study is to investigate the effects of multi-walled carbon nanotube addition to ethanol and n-heptane blends on HCCI engine performance, combustion and emission by experimentally and statistically. During the experiments, the mixed fuels formed with %25 ethanol, %75 n-heptane and 100, 150 and 200 ppm MWCNT additives were used. The experiment of these mixed fuels was carried out at different lambda and engine speed values. Response Surface Method was implemented to determine optimal additive amount and operation parameters of the engine. The variable parameter values to be used in the experiments were created with the central composite design, and a total of 20 experiments were performed. According to the obtained results, IMEP, ITE, BSFC, MPRR, COVimep, SOC, CA50, CO and HC response parameter values were obtained. Response parameter values were entered into the RSM environment and optimization studies were carried out depending on the response parameters targets. Among the optimum variable parameter values, the MWCNT ratio was determined as 102.16 ppm, lambda 2.7 and engine speed 1124.439 rpm. Response parameter values after optimization were determined as IMEP 4.988 bar, ITE 45.988 %, BSFC 227.846 g/kWh, MPRR 2.544 bar/CA, COVimep 1.722 %, SOC 4.445 CA, CA50 7 CA, CO 0.073 % and HC 476.452 ppm.

Performance and emission of a converted bio-fuel motorcycle engine in cold condition: A case study

ABSTRACT This paper presents a study on the performance and emission characteristics of a currently used motorcycle fueled with either gasoline or ethanol at cold starting and idling condition. The engine’s fuel system was modified by extending the injection pulse width to allow it to operate with pure ethanol or gasoline. The ethanol-fueled engine required three to four cranking times to achieve success starting at an ambient temperature between 15°C and 20°C. In cold idling conditions, the ethanol-fueled engine operated at a high coefficient of variation of speed (COVspeed) of 1.20% to 2.49% at an ambient temperature of 17°C, while a COV speed of 0.92% of the gasoline-fueled engine was observed. However, with the aid of the electric-based heating system (EHS), the ethanol-fueled engine performance was enhanced significantly as the COV speed was 0.95% at 15°C, 0.85% at 17°C, and 0.73% at 20°C in idling condition and achieved successful starting at the first time of cranking after 30 s of pre-heating. During the warm-up stage, a significant fluctuation of emission was observed with different test cases. However, with the heating system, the engine enhanced completed combustion quicker as incomplete combustion products of HC and CO were reduced rapidly in idling compared to gasoline and ethanol-fueled engine. NOx emissions increased with the aid of the heating system but were still lower compared to the gasoline-fueled engine during idling condition.

Energy and exergy characteristics of an ethanol-fueled heavy-duty SI engine at high-load operation using lean-burn combustion

Ethanol, as the most produced renewable biofuel, is considered a promising low-carbon alternative to petroleum-based fuels in the transport sector due to its high energy density and auto-ignition resistance. The lean-burn combustion in spark-ignition (SI) engines has the potential to further improve thermal efficiency in regard to knock mitigation and the reduction of combustion temperature. However, the characteristics of lean-burn combustion in an ethanol-fueled engine in relation to the combustion losses and the gas-exchange process remain unclear, especially for high-load operation. This study contributes with a deeper understanding of the high-load performance of an ethanol-fueled heavy-duty SI engine using lean-burn combustion. Based on the experimental results from a single-cylinder engine test, a 6-cylinder engine model is built by integrating a validated predictive combustion model to characterize the lean-burn combustion process. The engine’s thermal efficiency and combustion phasing are evaluated for knock limited operation and then compared to the theoretical optimum which is regardless of knock. The energy and exergy balances are applied to evaluate the effect of dilution with excess air ratios up to 1.8. Losses through heat transfer, exhaust flow, and incomplete combustion are quantified. In addition, entropy generated through combustion is discussed to identify the relationship between exergy destruction and different operating conditions. In the context of lean-burn combustion, the thermal efficiency at high-load operation incrementally increases from 40.4% at stoichiometric condition to 47.3% at an excess air ratio of 1.8. At the same time, the exergy destruction through combustion increases by 3.3 percentage points across the selected dilution range. Furthermore, the challenging requirements to realize lean-burn combustion with lower exhaust gas temperatures and higher intake boost pressures is assessed through an exergy analysis of the turbocharging system.

Effects of water injection strategies on performance and exhaust emissions in an ethanol fueled gasoline engine

• Ethanol and gasoline mixtures are used as an alternative fuel in spark ignition engines. • The most effective method among emission reduction methods is water injection. • Improvements are observed in engine performance parameters with the water spray method. • NOx and HC emissions have been reduced by 28% and 15%, respectively with water injection. The increase in the world population and the rapid development of technology cause energy consumption. Alternative fuels to petroleum should be used to meet the increasing energy consumption. In addition, the increase in the use of fossil fuels causes an increase in environmental pollution. Researchers have investigated many methods to reduce pollutant emissions using alternative fuels for internal combustion engines. In this study, alternative fuel and exhaust emission reduction methods were used simultaneously. Firstly, alternative fuel E15 (85% gasoline + 15% ethanol) was used in the engine and emission values were slightly reduced. Secondly, different mass rates (10%, 20% and 30%) of water were injected into the intake manifold to reduce the released emissions further. Using these two methods, reductions in exhaust emissions were determined without any deterioration in engine performance parameters. As a result of the experimental study, the best results in effective power and engine torque were obtained in 20% water injection. The rate of increase compared to the standard engine in the effective powe is 2.5% at 3400 rpm. The maximum amount of reduction in HC emissions was obtained in 20% water injection, and the amount of reduction was 15.3% at 2200 rpm. According to the standard engine data, the maximum reduction in NO x emissions is 28.9% at 3000 rpm. In the study result, it has been found that using alternative fuel and water injection management together improves engine performance and significantly lowers exhaust emissions.

Analysis of Combustion and Cycle to Cycle Variations of an Ethanol (E100) Fueled Spark-Ignition Engine

Ethanol, produced from biomass, is a renewable fuel that can be an attractive alternative fuel to gasoline for the increasing concerns of energy security and the environment. In the present work, combustion characteristics of ethanol (E100) fueled spark-ignition engine are compared with base gasoline fuel, and consecutively evaluated the cycle-to-cycle variations (CCV) of the engine parameters using statistical analysis. These investigations were performed on a 250cc air-cooled four-stroke single-cylinder port-fuel injection spark-ignition fueled with ethanol and gasoline fuels. The engine was operated at 3500 rpm and 4000 rpm of engine speed while maintaining the same loads for ethanol and gasoline. It was found from the results that the peak in-cylinder pressure (Ppeak) is lower with ethanol than gasoline at a given load. The Ppeak decreased from 27.5 to 25.5 bar when ethanol was used in the engine at 9.8:1 compression ratio, 3500 rpm, and 5 Nm load. Moreover, the mass fraction burned of the air-fuel mixture was faster for ethanol as compared to gasoline. The CCV with Ppeak, location of Ppeak, engine speed, and indicated mean effective pressure (IMEP) were evaluated. The result showed that CCV of Ppeak and its location were lowered for ethanol related to gasoline. A decrement in the coefficient of variation (COV) of Ppeak and its location from 11.6% to 8.3% and 12.6% to 11.7%, respectively, were observed when ethanol was utilized in the engine instead of gasoline at 3500 rpm and 5 Nm load. This resulted in a decrease in the COV of IMEP and engine speed by 2.8% and 0.25%, respectively, for ethanol as compared to gasoline at 3500 rpm and 5 Nm. This study results indicate the combustion stability of spark ignition engine with ethanol (E100) is better than gasoline fuel.

Thermodynamic and Comparative Analysis of Ejector Refrigeration Cycle and Absorption Refrigeration Cycle Integrated Wet Ethanol-Fueled HCCI Engine for Cogeneration of Power and Cooling

Abstract This study attempted for the proposal and analysis of a combined cycle that consists of a wet ethanol-fueled and turbocharged homogeneous charge compression ignition (HCCI) engine coupled to ejector refrigeration cycle (ERC) and absorption refrigeration cycle (ARC) for the simultaneous generation of two distinct outputs, namely, power and refrigeration. Both first and second laws of thermodynamics were employed to develop a thermodynamic model, which has been applied to investigate the performance of combined cycle. Furthermore, performance of the combined cycle for ERC versus ARC was compared and assessed after altering operating parameters (turbocharger pressure ratio, turbocharger compressor efficiency, ambient temperature, and the entrainment ratio of ERC and generator temperature of ARC) to study their effect on engine power output, refrigeration load, exergy of refrigeration, and energy and exergy efficiencies of the cooling-power cogeneration cycle. Results show that the elevated pressure of turbocharger results in the enhancement of HCCI engine power and increase of the refrigeration of thermal load, simultaneously. However, the increasing ambient temperature shows the decline of HCCI engine efficiencies and energy efficiency of cogeneration, while the cogeneration cycle exergy efficiency is found increasing. Furthermore, the results are reported for the refrigeration performed by lithium bromide–water (LiBr–H2O)-operated ARC, and R134a- and R290-operated ERC, respectively. Mapping of exergy destruction for the presented cogeneration cycle discovered HCCI engine, boiler of ERC, generator of ARC, and catalytic convertor as the components of significant exergy destruction. Entrainment ratio and type of refrigerant employed in ERC and the generator temperature of ARC show a marginal impact on the COPs of these cycles.

Fuel saving and lower pollutants emissions using an ethanol-fueled engine in a hydraulic hybrid passengers vehicle

This paper aims to compare the behavior of ethanol-fueled vehicles when operating exclusively with an internal combustion engine (ICE) and when using a small series hydraulic drivetrain in simulated standardized and real-world driving cycles. The computational models use fuel consumption and emissions maps acquired experimentally in stationary conditions from a multi-cylinder engine in previous work. The hydraulic hybrid powertrain uses the power generated by a pump driven by the ICE or stored in a hydro-pneumatic accumulator to accelerate the vehicle through a hydraulic motor connected to the differential box. Furthermore, a multi-objective optimization tool was used to size the hydraulic components and to calculate the values of the control variables for activating the motor-pump system, in order to achieve the compromise solution of minimum fuel consumption and emissions. The series hydraulic hybrid architecture implemented showed the possibility of reducing fuel consumption mainly in urban routes. The hybrid model optimized for reducing engine-out emissions pointed out the potential of reducing up to 47.2% and 20.7% the CO2 and NOx emissions levels in the real-world driving cycles, respectively. Furthermore, the optimized solution of lower engine-out emissions also showed potential between 30.17% and 44.14% of fuel-saving in urban routes with frequent stop-and-go events.

Experimental Investigations of Performance, Combustion and Emission Characteristics of Ethanol Fueled HCCI Engine

Bu çalışmada dört zamanlı, tek silindirli, port enjeksiyonlu bir benzinli motordan (SI) homojen dolgulu sıkıştırma ile ateşlemeli motora (HCCI) dönüşümü yapılmış Ricardo Hydra test motoru kullanılmıştır. Referans heptan ve heptan/etil alkol karışımlarının (E15 ve E25) yanma, motor performansı ve egzoz emisyonlarına etkisi deneysel olarak incelenmiştir. Emme havası giriş sıcaklığı 60℃’de sabitlenmiş ve motor hızı 800 rpm olarak belirlenmiştir. Farklı hava fazlalık katsayısı (HFK) değerlerinde silindir içi basınç, ısı dağılımı, yanma başlangıcı, CA50, yanma süresi, indike termik verim, indike ortalama efektif basınç (IMEP) ve egzoz emisyon sonuçları incelenmiştir. Heptan yakıtına etil alkol ilavesi yanmanın gecikmeye alınarak uzamasına neden olmuştur. Ayrıca yanmanın yavaşlatılması sağlanmıştır. Buna bağlı olarak basınç artış oranı azalarak HCCI yanma kontrol altına alınmıştır. En yüksek indike termik verim E15 yakıtı kullanımında HFK’nın 2 olduğu şartlarda %49 olarak belirlenmiştir. En yüksek IMEP E25 yakıtı kullanımında HFK’nın 1,3 olduğu şartlarda 6,1 bar olarak tespit edilmiştir. CO ve HC emisyonları ise heptan yakıtına etil alkol ilave edilmesi ile eş zamanlı olarak artış göstermiştir. Karışım yakıtları kullanımında silindir içi gaz sıcaklıklarının heptana göre düşük olması, yüksek emisyon değerlerinin temel nedeni olduğu ifade edilebilir. E15 yakıtının uygun çalışma şartlardında ideal yakıt olduğu bu çalışma ile ifade edilebilir.

A Study of the Influence of the Intercooled Turbocharger and Cooled EGR on the Performance Parameters of an Ethanol-fueled Engine

The hydrous ethanol combined with the turbocharged engine with exhaust gas recirculation (EGR) has been investigated with a phenomenological simulation model. This paper analyzes the influence of the low pressure and high pressure cooled EGR, the intercooler and the amount of recirculated gases, as they affect the performance parameters in a spark-ignited ethanol-fueled engine. Using a phenomenological model developed in Matlab®, the behavior of the pressure and temperature curves is analyzed considering the variation of the crank angle, the formation of NOx, and the tendency for knocking. The fuel analyzed is hydrous ethanol (E95h - 5%water by volume), which is widely used in Brazil. The proposed technique showed an increased power using the intercooler (IC) while avoiding knocking. This study showed that the use of a cooled EGR and turbocharged SI results in increased power, while also reducing NOx formation, and preventing or reducing engine knocking. In some engines, the low pressure cooled EGR is better than high pressure, but this can be different for another engine. The model helps to find the best or more adequately equipped for each model of engine.

Chemical kinetics analysis of NO and CO formation based on thermodynamic data from an ethanol-fueled engine computational model

Chemical kinetics analysis of NO and CO formation based on thermodynamic data from an ethanol-fueled engine computational model

Exploring the potential of reformed-exhaust gas recirculation (R-EGR) for increased efficiency of methanol fueled SI engines

Methanol is a promising fuel for spark ignition engines because of its high octane number, high octane sensitivity, high heat of vaporization and high laminar flame speed. To further boost the efficiency of methanol engines, the use of waste heat for driving fuel reforming was considered. This study explores the possibility of the reformed-exhaust gas recirculation (R-EGR) concept for increased efficiency of methanol engines. A simple Otto cycle calculation and a more detailed gas dynamic engine simulation are used to evaluate that potential. Both methodologies point to an enhancement in engine efficiency with fuel reforming compared to conventional EGR but not as much as the increase in lower heating value of the reforming product would suggest. A gas dynamic engine simulation shows a shortening of the flame development period and the combustion duration in line with the expected behavior with the hydrogen-rich reformer product gas. However, the heat loss increases with the presence of hydrogen in the reactants. The improvement of brake thermal efficiency is mainly attributed to the reduction of pumping work. The R-EGR concept is also evaluated for ethanol and iso-octane. As the reforming fraction increases, the efficiency of ethanol and iso-octane fueled engines rises faster than for the methanol engines due to a higher enhancement of exergy in their reforming products. At high reforming fractions, the efficiency of the ethanol engine becomes higher than with methanol. However, if the impact of optimal compression ratio for different fuels are considered, the methanol engine is able to produce a higher efficiency than the ethanol engine.

Characterization of an ethanol fueled heavy-duty engine powering a generator set

The increase in electricity demand in Brazil and the frequent interruptions in its supply forced the industry and commerce use stationary generator sets, mainly in large urban centers like São Paulo. This city established a decree in order that these devices use cleaner fuels than diesel oil, or adopt post-gas treatment systems, since there are no national regulations for generator sets emissions. To meet this decree, ethanol appears as a good option because it is an environmentally friendly fuel, does not affect the ozone layer, since it is obtained from sugarcane, which helps to reduce the carbon dioxide emissions to the atmosphere through photosynthesis in sugarcane field. Within recommended specifications ethanol can be blended with diesel and gasoline, but can also be used without additives, without damaging the engine. The ethanol availability in Brazil and its consolidation in the automotive market make it an alternative for use in generator sets. The aim of this work was to characterize the performance of a heavy duty Otto cycle engine, developed based on 12l diesel longblock, prepared to run on ethanol without additives, as a prototype generator set. The performance tests of the generator set were conducted at three different altitudes. A load bank was used to simulate the real electrical load in five different power settings. The performance characteristics obtained experimentally were compared with results obtained with a one-dimensional model using the commercial software GT-Power®. The results obtained during the development phase showed that the engine achieve up to 39.6% of the brake efficiency and a peak power of the 326kW. The maximum electrical power achieved by the generator set was 302kW at sea level and 278kW at 1640m, according to the employed methodology. The results showed that is feasible to use ethanol without additives for the energy generation, replacing diesel oil in heavy-duty engines, operating in the evaluated steady state condition.

Missions of ethanol fueled engine and carcinogenic gases

Ethanol is used widely as a bio-fuel. It is produced from bio-mass (such as corn, sugarcane and sugar beet. Research has proved that ethanol improves performance of theinternal combustion engine and it considered as an environmental friendly fuel. Use ofEthanol reduces the emission (CO2, CO, NOx, HC, PM) compared to diesel and gasolinefuel, but this depends on the strategy of operation. However, using Ethanol increasesthe emissions of aldehydes dramatically, especially acetaldehyde and formaldehyde,which are carcinogenic.The purpose of this paper is to study the parameters that affect aldehydes emitted fromEthanol fueled engines by using CHEMKIN-PRO advanced simulation program.

Performance prediction of HCCI engines with oxygenated fuels using artificial neural networks

Butanol and ethanol are promising conventional fuel alternatives particularly when utilized in advanced combustion mode like homogeneous charge compression ignition (HCCI). This study investigates the performance and emission characteristics of HCCI engines fueled with oxygenated fuels (i.e. butanol and ethanol). The investigation is done through a combination of experimental data analysis and artificial neural network (ANN) modeling.This study uses HCCI experimental data to characterize variations in seven engine performance metrics including indicated mean effective pressure (IMEP), thermal efficiency, in-cylinder pressure, net total heat released, nitrogen oxides (NOx), carbon monoxide (CO), and total hydrocarbon (THC) concentrations. Two types of ANNs including radial basis function (RBF) and feedforward (FF) are developed to predict the seven engine performance metrics. The experimental data at 123 HCCI operating points from two different engines are collected to validate the ANN models. The validation results indicate both RBF and FF models can predict HCCI engine performance metrics with less than 4% error for butanol and ethanol fueled engines. The results show that the FF neural network models are advantageous in terms of network simplicity with fewer required neurons but need twice as much training time compared to the RBF models.

Study on the phase relation between ion current signal and combustion phase in an HCCI combustion engine

Ion sensing is a promising approach for cycle resolved combustion phasing in HCCI engines. This paper investigates the fundamental processes affecting the phase difference (Pdelta) between ion current signal phase Ion50 and combustion phase CA50 based on 2 numerical models. One model is used to explore fluid dynamic effects on an HCCI engine. The other model, a 10-zone model, is used to primarily explore the affecting mechanism on Pdelta. Both numerical analysis and experimental results of the ionization process indicate that Pdelta is affected by both flame ionization and fuel heat release process. For fuels with similar octane number (ON), such as gasoline (ON=97) and ethanol (ON=107), both the combustion phase CA50 and the ion current signal phase Ion50 retard when the equivalence ratio Φ decreases. However, the CA50 for ethanol fuel retards moderately compared with the gasoline case since the CA50 for ethanol fuel is more sensitive to intake temperature Tin rather than Φ. Then larger Pdelta values can be seen in ethanol fueled HCCI engine under lower Φ conditions. For the fuels with different widely octane number, such as gasoline and diesel (ON=0), their combustion boundary conditions are different in HCCI engines, they produce ions at a different ratio. For diesel fuel, the ion production rate is much lower due to the lower intake temperature and higher compression ratio. Under low Φ conditions, the ion current signal cannot be observed at the beginning of ion concentration increase in diesel fueled HCCI engines, and the Ion50 appears much later compared with the gasoline fueled HCCI engine. As a result, the values of Pdelta increase significantly in the diesel fueled HCCI engine.

Experimental Investigations of Particulate Size and Number Distribution in an Ethanol and Methanol Fueled HCCI Engine

Alcohols (ethanol and methanol) are being widely considered as alternative fuels for automotive applications. At the same time, homogeneous charge compression ignition (HCCI) engine has attracted global attention due to its potential of providing high engine efficiency and ultralow exhaust emissions. Environmental legislation is becoming increasingly stringent, sharply focusing on particulate matter (PM) emissions. Recent emission norms consider limiting PM number concentrations in addition to PM mass. Therefore, present study is conducted to experimentally investigate the effects of engine operating parameters on the PM size–number distribution in a HCCI engine fueled with gasoline, ethanol, and methanol. The experiments were conducted on a modified four-cylinder diesel engine, with one cylinder modified to operate in HCCI mode. Port fuel injection was used for preparing homogeneous charge in the HCCI cylinder. Intake air preheating was used to enable auto-ignition of fuel–air mixture. Engine exhaust particle sizer (EEPS) was used for measuring size–number distribution of soot particles emitted by the HCCI engine cylinder under varying engine operating conditions. Experiments were conducted at 1200 and 2400 rpm by varying intake air temperature and air–fuel ratio for gasoline, ethanol, and methanol. In this paper, the effect of engine operating parameters on PM size–number distribution, count mean diameter (CMD), and total PM numbers is investigated. The experimental data show that the PM number emissions from gasoline, ethanol, and methanol in HCCI cannot be neglected and particle numbers increase for relatively richer mixtures and higher intake air temperatures.