Browse Topic: Dimethyl ether (DME)

Items (87)

A Study of a Lean Homogeneous Combustion Engine System with a Fuel Reformer Cylinder

2019-01-217712/19/2019

The Dual-Fuel (DF) combustion is a promising technology for efficient, low NOx and low exhaust particulate matter (PM) engine operation. To achieve equivalent performance to a DF engine with only the use of conventional liquid fuel, this study proposes the implementation of an on-board fuel reformation process by piston compression. For concept verification, DF combustion tests with representative reformed gas components were conducted. Based on the results, the controllability of the reformed gas composition by variations in the operating conditions of the reformer cylinder were discussed.

Asai, Go, Tokuoka, Yuki, Bayer, Thomas, Ishiguro, Shuntaro, Shibata, Gen, Ogawa, Hideyuki, Kobashi, Yoshimitsu, Watanabe, Yusuke

Etching of Fluoropolymer Insulations

ARP6167 (Current)6/11/2019

This SAE Aerospace Recommended Practice (ARP) describes the etching of fluoropolymer electrical wire insulations to ensure that all facets of the process from the chemistry to the processing, to the storage and handling are well defined.

AE-8A Elec Wiring and Fiber Optic Interconnect Sys Install

A Computational Study on Laminar Flame Propagation in Mixtures with Non-Zero Reaction Progress

2019-01-09464/2/2019

Flame speed data reported in most literature are acquired in conventional apparatus such as the spherical combustion bomb and counterflow burner, and are limited to atmospheric pressure and ambient or slightly elevated unburnt temperatures. As such, these data bear little relevance to internal combustion engines and gas turbines, which operate under typical pressures of 10-50 bar and unburnt temperature up to 900K or higher. These elevated temperatures and pressures not only modify dominant flame chemistry, but more importantly, they inevitably facilitate pre-ignition reactions and hence can change the upstream thermodynamic and chemical conditions of a regular hot flame leading to modified flame properties. This study focuses on how auto-ignition chemistry affects flame propagation, especially in the negative-temperature coefficient (NTC) regime, where dimethyl ether (DME), n-heptane and iso-octane are chosen for study as typical fuels exhibiting low temperature chemistry (LTC). The computation of laminar flame speed of lean and stoichiometric mixtures of fuel/air was performed at different ignition reaction progress, by selecting the thermal chemical states corresponding to different residence times during auto-ignition as the flame upstream condition. Using scaling and budget analysis, it is shown that a well-defined flame speed for such a partially reactive mixture in the classical diffusion-reaction limit could still be feasible in the appropriate computational domain, especially with a sufficiently reduced induction length. The comparison of flame speed against different types of progress variables indicates a nearly linear relationship between the flame speed and progress variables based on the fuel mass fraction and temperature. Thermal and chemical effect of a cool-flame upstream has been isolated by comparing the flame speed of the initial mixture and that of the instantaneous mixture under the same thermodynamic conditions. It is found that the enhanced propagation is shown to be largely a thermodynamic effect, while chemistry nevertheless plays an overall retarding role. Sensitivity analysis has been performed to identify the key species which most influence flame propagation at different reaction progress. A general scheme of simplified mixture was constructed to describe flame propagation in a partially reactive mixture, for both lean and stoichiometric, as well as high pressures conditions. This study provides useful insights into flame propagation in practical engine conditions.

Lin, Han, Zhao, Peng, Ge, Haiwen

An Optical Study on the Combustion of Gasoline/PODEn Blends in a Constant Volume Vessel

2018-01-17489/10/2018

Polyoxymethylene dimethyl ethers (PODEn) have high cetane number, high oxygen content and high volatility, therefore can be added to gasoline to optimize the performance and soot emission of Gasoline Compression Ignition (GCI) combustion. High speed imaging was used to investigate the spray and combustion process of gasoline/PODEn blends (PODEn volume fraction 0%-30%) under various ambient conditions and injection strategies in a constant volume vessel. Results showed that with an increase of PODEn proportion from 10% to 30%, liquid-phase penetration of the spray increased slightly, ignition delay decreased from 3.8 ms to 2.0 ms and flame lift off length decreased 29.4%, causing a significant increase of the flame luminance. For blends with 20% PODEn, when ambient temperature decreased from 893 K to 823 K, the ignition delay increased 1.3 ms and the flame luminance got lower. When increasing the injection pressure, the liquid phase length and the ignition delay got a little longer and the flame luminance and flame duration decreased. Long spray results showed that soot formed in higher PODEn flames oxidized earlier and quicker. The parameter changes that can extend the ignition delay all gave rise to the decrease of flame luminance because of the increase of the proportion of premixed combustion.

Ma, Yue, Cui, Longxi, Ma, Xiao, Wang, Zhi, Shuai, Shi-Jin

Comparison of Primary Sensitive Reactions on Fuel Reactivity between Detailed and Skeletal Mechanisms of Gasoline Surrogate

2018-01-17379/10/2018

Combustion simulation is of great importance for internal combustion engine development. With the advance of fundamental combustion experiments and theoretical computation, detailed combustion mechanisms of gasoline surrogates have been enhanced with introduction of new reactions and updated reaction rate constants recently. However, detailed combustion mechanisms with tens of thousands of reactions are still not practical for engineering use in view of massive computation cost. As a practical alternative, skeletal mechanisms are usually developed to couple with three dimensional engine combustion simulations. As for skeletal mechanisms, rate constants of some important reactions have to be tuned to reproduce the experimental data due to the omission of intermediate reaction steps, thus are different from those applied in detailed mechanisms. However, whether the skeletal mechanism reproduces the combustion reaction process with similar major reactions as the detailed mechanisms is rarely studied. Therefore, the aim of this study is to investigate the different sensitive reactions between the detailed and skeletal mechanisms that affect the fuel reactivity with brute force sensitivity analysis. Results show that the detailed mechanism predicts more strong negative temperature coefficient behavior than the skeletal mechanism. Similar ignition delays were predicted by both mechanisms around 700 K, while the significant difference occurred around 825 K. For the skeletal mechanism, reactions with rate constants altered by one to three orders could change their role of controlling the fuel reactivity as in the detailed mechanism, and also substantially affect the first stage ignition process. Therefore, procedure for reaction rate constant tuning with optimization directions should be proposed in the future for constructing skeletal mechanisms that could reproduce the combustion characteristics of fuels with similar reactivity controlling reactions as in the detailed mechanisms.

Meng, Xiangzan, Meng, Yi

A Computational Study of Lean Limit Extension of Alcohol HCCI Engines

2018-01-16799/10/2018

The purpose of present numerical study was to extend the operating range of alcohol (methanol and ethanol) fueled Homogeneous Charge Compression Ignition (HCCI) engine under low load conditions. Ignition of pure methanol and ethanol under HCCI mode of operation requires high intake temperatures and misfires at low loads are common in HCCI engines. Three methods have been adapted to optimize the use of methanol and ethanol for HCCI operation without increasing the intake temperature. First, blending methanol and ethanol with ignition improver, namely di-methyl ether (DME) and di-ethyl ether (DEE), was used to increase the cetane number and ignitability of premixed charge. Second, based on the blended fuels, the spark assistance was used to reduce required intake temperature for auto-ignition. Third, DME and DEE were directly injected to methanol and ethanol operated HCCI engine, in the form of Reactivity Controlled Compression Ignition (RCCI) combustion. Negligible improvement in reducing intake temperature was observed in spark-assisted HCCI combustion due to the slow flame propagation speed under the lean premixed condition with blended fuels. In all three methods, it was found that RCCI combustion was more effective at reducing the required intake temperature compared to HCCI and spark assisted combustion, in spite of the fact that they are operated at same lambda (3.3) operating conditions.

Zhou, Qiyan, Mubarak Ali, Mohammed Jaasim, Mohan, Balaji, Lu, Xing-Cai, Im, Hong

Experimental Investigation of Combustion and Emission Characteristics of the Direct Injection Dimethyl Ether Enabled Micro-Flame Ignited (MFI) Hybrid Combustion in a 4-Stroke Gasoline Engine

2018-01-12474/3/2018

Controlled Auto-Ignition (CAI), also known as Homogeneous Charge Compression Ignition (HCCI), has the potential to improve gasoline engines’ efficiency and simultaneously achieve ultra-low NOx emissions. Two of the primary obstacles for applying CAI combustion are the control of combustion phasing and the maximum heat release rate. To solve these problems, dimethyl ether (DME) was directly injected into the cylinder to generate multi-point micro-flame through compression in order to manage the entire heat release of gasoline in the cylinder through port fuel injection, which is known as micro-flame ignited (MFI) hybrid combustion. The combustion and emissions characteristics of MFI mode were investigated in a single-cylinder 4-stroke gasoline engine by the use of negative valve overlap (NVO) strategy at part loads when direct injection timing of DME was altered from -60 °CA to -40 °CA after top dead center, and the replacement ratio of DME for gasoline was no more than 20% at a fixed total energy per cycle. The results show that earlier start of the main combustion process with increased DME ratio occurs, while its trend becomes weak at late DME direct injection timing. Combustion duration shortens with increased DME ratio, but it is elongated with delayed DME injection timing. Increased DME ratio reduces HC and CO emissions, but increases NOx emissions. The influence of DME ratio on emissions characteristics becomes minimal at late DME direct injection timing.

Fu, Xue-Qing, He, Bang-Quan, Xu, Sipeng, Li, Hongtao, Chen, Tao, Zhao, Hua

The Direct Transition of Fuel Sprays to theDense-Fluid Mixing Regime in the Contextof Modern Compression Ignition Engines

2018-01-02984/3/2018

Fuel supercriticality has recently received significant attention due to the elevated pressures and temperatures that directly-injected (DI) fuel sprays encounter in modern internal combustion (IC) engines. This paper presents a theoretical examination of conventional and alternative DI fuels at conditions relevant to the operation of compression ignition (CI) engines. The focus is to identify the conditions under which the injected liquid fuel can bypass the atomization process and directly transition to a diffusional mixing regime with the chamber gas. Evaluating the microscopic length-scales of the phase boundary associated with the injection of liquid nitrogen into its own vapor, it is found that the conventional threshold based on the interfacial Knudsen number (i.e. Kn = 0.1) does not adequately quantify the direct transition between sub- and supercriticality. Instead, a threshold that is an order of magnitude smaller is more appropriate for this purpose. Extending the analysis to a range of diesel fuel surrogates (e.g. n-heptane and n-dodecane), and alternative engine fuels that can be blended for use in CI engines (e.g. dimethyl ether and propane), it is then found that the local Knudsen numbers associated with the injection of conventional liquid fuels are significantly higher than those previously calculated in the literature, suggesting that those fuels will not directly transition to a dense-fluid mixing regime for all engine relevant conditions. However, the results show that the immediate transition to a single-phase regime may be relevant to lighter alternative fuels like DME and propane, which is attributed to the significantly lower critical temperature of these fuels, as well as their higher miscibility with the gas in the chamber.

Poursadegh, Farzad, Lacey, Joshua, Brear, Michael, Gordon, Robert

Intermediate Combustion Modes between Conventional Diesel and RCCI

2018-01-02494/3/2018

In recent years, several unconventional fueling modes have been developed for dual-fuel compression ignition (CI) engines. One such mode is reactivity controlled compression ignition (RCCI), which utilizes both a low-reactivity fuel (LRF) and a high-reactivity fuel (HRF) via separate injection systems. RCCI has been tested with many fuels, but there have been relatively few tests on the intermediate modes that exist in between RCCI and conventional diesel combustion (CDC). For this purpose, a quantitative classification system of fueling modes was created and used to test incremental changes in the fueling mode of a 1.9L General Motors (GM) turbodiesel engine, shifting between CDC and RCCI at a single speed/load point. This engine used a 5:2 mass ratio blend of propane and dimethyl ether (DME) as its LRF and ultra-low-sulfur diesel (ULSD) as its HRF. The results confirm previous findings that RCCI can achieve improvements in thermal efficiency, nitrogen oxide (NOx) emissions, and soot emissions simultaneously, at the expense of degradations in peak pressure, max pressure rise rate (PRR), and hydrocarbon emissions. The new developments made were the evaluation and analysis of the intermediate fueling modes between CDC and RCCI, which are herein termed partially premixed compression ignition (PPCI), conventional dual-fuel (CDF), and premixed dual-fuel combustion (PDFC). PDFC in particular appears promising as an intermediate “bridge” between CDC and RCCI, and under the correct conditions, PDFC can produce improvements in thermal efficiency, NOx, and soot emissions similar to RCCI, but without the high peak pressures and PRRs associated with RCCI.

Martin, Jonathan, Boehman, Andre, Topkar, Rutvik, Chopra, Sumit, Subramaniam, Uday, Chen, Heng

Numerical Optimization of the Combustion System of a HD Compression Ignition Engine Fueled with DME Considering Current and Future Emission Standards

2018-01-02474/3/2018

A genetic algorithm (GA) optimization methodology is applied to the design of the combustion system of a heavy-duty (HD) Diesel engine fueled with dimethyl ether (DME). The study has two objectives, the optimization of a conventional diffusion-controlled combustion system aiming to achieve US2010 targets and the optimization of a stoichiometric combustion system coupled with a three way catalyst (TWC) to further control NOx emissions and achieve US2030 emission standards. These optimizations include the key combustion system related hardware, bowl geometry and injection nozzle design as input factors, together with the most relevant air management and injection settings. The GA was linked to the KIVA CFD code and an automated grid generation tool to perform a single-objective optimization. The target of the optimizations is to improve net indicated efficiency (NIE) while keeping NOx emissions, peak pressure and pressure rise rate under their corresponding target levels. Compared to the baseline engine fueled with DME, the results of the study provide an optimum conventional diesel combustion system with 3.3% NIE improvement and an optimum stoichiometric combustion system that offers a 0.6% NIE improvement keeping tailpipe NOx values below 1% of the original levels. Due to the methodology, not only the optimum combustion system configuration is described, but also the cause-effect relations between the most relevant inputs and the optimization outputs are identified and analyzed. The new geometry shapes reduce heat transfer (HT) losses by controlling the surface area while EGR is still critical to control NOx emissions for both combustion systems. This study confirms the potential of DME as a promising fuel for the future generation of compression ignition engines, and demonstrates the benefits of co-optimizing the fuel properties, combustion chamber hardware and air management plus injection settings.

Benajes, Jesus, Novella, Ricardo, Hernández-López, Alberto, Kokjohn, Sage

Development of Surrogate Model for Oxygenated Wide-Distillation Fuel with Polyoxymethylene Dimethyl Ether

2017-01-233610/8/2017

Polyoxymethylene Dimethyl Ether (PODEn) is a promising green additive to diesel fuel, owing to the unique chemical structure (CH3O[CH2O]nCH3, n≥2) and high cetane number. Together with the general wide-distillation fuel (WDF), which has an attractive potential to reduce the cost of production of vehicle fuel, the oxygenated WDF with PODEn can help achieve a high efficiency and low emissions of soot, NOx, HC, and CO simultaneously. In this paper, the first detailed reaction mechanism (225 species, 1082 reactions) which can describe the ignition characteristics of PODE1 and PODE3 at low temperature was developed. To validate this mechanism, rapid compression machine (RCM) was used to conduct the quasi-homogeneous experiments to measure the ignition delay time at various effective temperatures (600 K - 1000 K) for four different PODE1/O2/N2/Ar mixture (ϕ=0.25, O2:Ar=1:5; ϕ=0.5, O2:Ar:N2 = 1:2.5:2.5; ϕ=1.0, O2:Ar:N2 = 1:2.5:2.5; ϕ=1.0, O2:Ar:N2 = 1:5:5) and two different effective pressures (10 bar, 19 bar). Homogeneous Charge Compression Ignition (HCCI) experiments fueled with PODEn (n=1-4) mixture, in which the mass fraction of PODE3 is about 88.9% were also conducted in a naturally aspirated single-cylinder HCCI research engine at 1600 r/min, 0.4 charge-mass equivalence ratio, and 42% exhaust gas recirculation (EGR) to take the real engine working condition into consideration. Good agreement was achieved in the comparison of the experimental data and the simulation results utilizing our newly developed mechanism for PODE1 and PODE3. Considering the fact that PODEn is more frequently used as a blending component in diesel engine, a reduced multi-component mechanism (354 species, 943 reactions) for oxygenated WDF with PODEn (covering surrogates like PODE3, n-heptane, iso-octane, etc.) was developed and then validated with Direct-Injection Compression Ignition (DICI) engine experiments fueled with oxygenated WDF (gasoline/diesel/PODEn mixture) at 1600 r/min, 0.8 MPa indicated mean effective pressure (IMEP), and 25% EGR. This surrogate model will contribute to the design of oxygenated WDF by blending PODEn, and to the prediction of the combustion and emission characteristics of engines using oxygenated WDF.

He, Tanjin, Liu, Hao-ye, Wang, Yingdi, Wang, Boyuan, Liu, Hui, Wang, Zhi

Development of a Reduced Chemical Mechanism for Dimethyl Ether (DME) Using a Decoupling Methodology

2017-01-219110/8/2017

Dimethyl ether (DME) attracts increasing attentions in recent years, because it can reduce the carbon monoxide (CO), unburned hydrocarbon (HC), and soot emissions for engines as the transportation fuel or the fuel additive. In this paper, a reduced DME oxidation mechanism is developed using the decoupling methodology. The rate constants of the fuel-related reactions are optimized using the non-dominated sorting genetic algorithm II (NSGA-II) to reproduce the ignition delay times in shock tubes and major species concentrations in jet-stirred reactors (JSR) over low-to-high temperatures. In NSGA-II, the range of the rate constants was considered to ensure the reliability of the optimized mechanism. Moreover, an improved objective function was proposed to maintain the faithfulness of the optimized mechanism to the original reaction mechanism, and a new method was presented to determine the optimal solution from the Pareto front. The final reduced mechanism includes 42 species and 171 reactions. The comparisons between the measured and predicted results demonstrate that the present mechanism is capable of reproducing the ignition delay time in shock tubes and rapid compression machines, major species concentration in JSRs, flow reactors, and laminar premixed flames, as well as the laminar flame speed over the temperature range of 500-1500 K, the pressure range of 0.05-40 atm, and the equivalence ratio range of 0.25-2.0. Due to its compact size, the final mechanism is also coupled with the multi-dimensional computational fluid dynamic (CFD) to simulate the combustion and autoignition characteristics of DME in practical engines.

Chang, Yachao, Jia, Ming, Zhang, Yanzhi, Li, Yaopeng, Fan, Weiwei, Xie, MaoZhao

Experimental Study on High-Load Extension of Gasoline/PODE Dual-Fuel RCCI Operation Using Late Intake Valve Closing

2017-01-07543/28/2017

The dual-fuel Reactivity Controlled Compression Ignition (RCCI) combustion could achieve high efficiency and low emissions over a wide range of operating conditions. However, further high load extension is limited by the excessive pressure rise rate and soot emission. Polyoxymethylene dimethyl ethers (PODE), a novel diesel alternative fuel, has the capability to achieve stoichiometric smoke-free RCCI combustion due to its high oxygen content and unique molecule structure. In this study, experimental investigations on high load extension of gasoline/PODE RCCI operation were conducted using late intake valve closing (LIVC) strategy and intake boosting in a single-cylinder, heavy-duty diesel engine. The experimental results show that the upper load can be effectively extended through boosting and LIVC with gasoline/PODE stoichiometric operation. With the retarding of LIVC timing and increase of cyclic fuel quantity, higher boosting pressure and lower Exhaust Gas Recirculation (EGR) ratio were required to maintain sufficient available oxygen. The upper load of gasoline/PODE RCCI operation could be extended up to 23 bar indicated mean effective pressure (IMEP), while still maintaining ultra-low smoke/NOx emissions and acceptable peak in-cylinder pressure and pressure rise rate (PRR). In addition, stoichiometric combustion also enables the application of a low-cost three-way catalyst to further reduce HC and CO emissions. However, LIVC results in slight reduction of indicated thermal efficiency (ITE) due to the lower effective compression ratio and more incomplete combustion with stoichiometric operation, thus further combustion optimization is necessary for ITE improvement. The study reveals that gasoline/PODE RCCI offers a very competitive pathway to achieve clean and highly efficient combustion over the full load conditions.

Wang, Hu, Tong, Laihui, Zheng, Zunqing, Yao, Mingfa

Influence of Supercharging and EGR on Multi-stage Heat Release in an HCCI Engine

2016-32-000911/8/2016

Homogeneous Charge Compression Ignition (HCCI) combustion has attracted widespread interest as a combustion system that offers the advantages of high efficiency and low exhaust emissions. However, it is difficult to control the ignition timing in an HCCI combustion system owing to the lack of a physical means of initiating ignition like the spark plug in a gasoline engine or fuel injection in a diesel engine. Moreover, because the mixture ignites simultaneously at multiple locations in the cylinder, it produces an enormous amount of heat in a short period of time, which causes greater engine noise, abnormal combustion and other problems in the high load region. The purpose of this study was to expand the region of stable HCCI engine operation by finding a solution to these issues of HCCI combustion. The results of previous studies have shown that the application of supercharging when using a fuel blend of dimethyl ether and methane moderates the rapid rate of combustion, resulting in two-stage heat release during the main combustion period under certain specific operating conditions. The mechanism producing two-stage heat release has been made clear by spectroscopic measurements and exhaust gas analysis using a Fourier transform infrared spectrometer. In this study, the possibility of expanding the high-load operating region of an HCCI engine was investigated by applying supercharging and exhaust gas recirculation, which are known to be effective for operating an HCCI engine at high loads.

Takamura, Yuki, Shima, Takahiro, Suzuki, Hirotaka, Agui, Keito, Iijima, Akira, Shoji, Hideo

A Study of HCCI Operating Range Expansion by Applying Reaction Characteristics of Low-Carbon Alternative Fuels

2016-32-001111/8/2016

Issues that must be addressed to make Homogeneous Charge Compression Ignition (HCCI) engines a practical reality include the difficulty of controlling the ignition timing and suppression of rapid combustion under high load conditions. Overcoming these issues to make HCCI engines viable for practical application is indispensable to the further advancement of internal combustion engines. Previous studies have reported that the operating region of HCCI combustion can be expanded by using DME and Methane blended fuels.(1), (2), (3), (4), (5) The reason is that the reaction characteristics of these two low-carbon fuels, which have different ignition properties, have the effect of inducing heat release in two stages during main combustion, thus avoiding excessively rapid combustion. However, further moderation of rapid combustion in high-load region is needed to expand the operation region. This study focused on supercharging and use of blended fuels. For the purpose of promoting the practical implementation of HCCI engines, experiments were conducted in the present study with the aim of expanding the HCCI operating range over a wide region of combustion loads by using the reaction characteristics of a fuel blend of DME/methane. The results revealed that the pressure rise rate was substantially reduced while maintaining the indicated mean effective pressure level. It was also observed that HCCI operation over a wide range of engine loads was possible by making use of two-stage heat release during main combustion.

Agui, Keito, Suzuki, Hirotaka, Takamura, Yuki, Iijima, Akira, Shoji, Hideo

Reforming Controlled Homogenous Charge Compression Ignition -Simulation Results

2016-32-001411/8/2016

A computer model was built and a theoretical analysis was performed to predict the behavior of a system containing Homogenous charge compression ignition (HCCI) engine and a methanol reformer. The reformer utilizes the waste heat of the exhaust gases to sustain the two subsequent processes: dehydration of methanol to dimethyl ether (DME) and water, and methanol steam reforming (SRM) where methanol and water react to mainly hydrogen, CO and CO2. Eventually, a gaseous mixture of DME, H2, CO, CO2, water (reused) and some other species is created in these processes. This mixture is used for the engine feeding. By adding water to the methanol and fixing the vaporized fuel's temperature, it is possible to manage the kinetics of chemical processes, and thus to control the products’ composition. This allows controlling the HCCI combustion. By a magnification of H2/DME ratio the ignition delay is increased and so it is possible to synchronize the ignition timing and also to control combustion duration. The simulation results prove feasibility of the suggested approach and a possibility of achieving substantially higher energy efficiency together with zero-impact NOx emissions in a wide range of engine operating modes.

Eyal, Amnon, Tartakovsky, Leonid

Well-to-Wheels Emissions of Greenhouse Gases and Air Pollutants of Dimethyl Ether from Natural Gas and Renewable Feedstocks in Comparison with Petroleum Gasoline and Diesel in the United States and Europe

2016-01-220910/17/2016

Dimethyl ether (DME) is an alternative to diesel fuel for use in compression-ignition engines with modified fuel systems and offers potential advantages of efficiency improvements and emission reductions. DME can be produced from natural gas (NG) or from renewable feedstocks such as landfill gas (LFG) or renewable natural gas from manure waste streams (MANR) or any other biomass. This study investigates the well-to-wheels (WTW) energy use and emissions of five DME production pathways as compared with those of petroleum gasoline and diesel using the Greenhouse gases, Regulated Emissions, and Energy use in Transportation (GREET®) model developed at Argonne National Laboratory (ANL). The five DME pathways include 1) fossil NG with large-scale DME plants, 2) methanol from fossil NG with large-scale plants for both methanol and DME (separately), 3) LFG with small-scale DME plants, 4) manure-based biogas with small-scale DME plants, and 5) methanol from black liquor gasification with small-scale DME plants. This study analyzes DME production and use in the U.S. and Europe, and in two vehicle classes (light and heavy duty vehicles [LDVs and HDVs]). The WTW results show significant reductions in fossil fuel consumption and greenhouse gas (GHG) emissions by DME compared to gasoline and diesel if DME is produced from LFG and manure-based biogas. When methanol from black liquor is used for DME production, there are reductions in GHG emissions, though smaller than DME produced from LFG and MANR. Meanwhile, fossil NG-based DME produced in large-scale DME plants or from NG-based methanol shows GHG emissions at the similar level as petroleum diesel does.

Lee, Uisung, Han, Jeongwoo, Wang, Michael, Ward, Jacob, Hicks, Elliot, Goodwin, Dan, Boudreaux, Rebecca, Hanarp, Per, Salsing, Henrik, Desai, Parthav, Varenne, Emmanuel, Klintbom, Patrik, Willems, Werner, Winkler, Sandra L., Maas, Heiko, De Kleine, Robert, Hansen, John, Shim, Tine, Furusjö, Erik

Measurement of Sound Speed in DME in a Wide Range of Pressure and Temperature Including the Critical Point

2016-01-225810/17/2016

Dimethyl ether (DME) is a promising alternative fuel for compression ignition (CI) engines. DME features good auto ignition characteristics and soot-free combustion. In order to develop an injection system suitable for DME, it is necessary to understand its fuel properties. Sound speed is an important fuel property that affects the injection characteristics. However, the measurement data under high-pressures corresponding to those in fuel injection systems are lacking. The critical temperature of DME is lower than that of diesel fuel, and is close to the injection condition. It is important to understand the behavior of the sound speed around the critical point, since the sound speed at critical point is extremely low. In this study, sound speed in DME in a wide pressure and temperature range of 1 MPa to 80 MPa, 298.15 K to 413.15 K, including the vicinity of the critical point, was measured. The sound speed in DME decreases as either the pressure falls or the temperature rises. It is approximately 400 m/s slower than that found in diesel fuel. Around the critical point, the sound speed drastically decreases due to a lowering of bulk modulus. At a low-pressure region below 20 MPa including the vicinity of the critical point, the experimental results were consistent with the calculated results based on Helmholtz equation of state, proposed by Wu et al. [1]. The calculated value in the high-pressure range has a tendency to register a slightly higher than the experimental one as the pressure rises.

Okoshi, Yoshihiro, Kikuchi, Shinsuke, Mitsugi, Yuta, Tanaka, Kotaro, Kato, Masaaki, Tsuji, Tomoya, Konno, Mitsuru

Evaluation of Hydrous Ethanol Fuel Lubricity by HFRR

2016-01-226010/17/2016

Improvement of thermal efficiency is an important problem for internal combustion engines. Fuel reforming with dehydrogenation reaction by exhaust heat is one of the measures to increase thermal efficiency using hydrogen mixed SI combustion. For this kind engine system, hydrous ethanol has a good potential. Furthermore, when the hydrous ethanol inject to combustion chamber directory, high compression combustion can be achieved by its large amount of latent heat. Therefore, fuel lubricity is an important check point for the hydrous ethanol reforming engine systems. In this study, effect of water concentrations within ethanol on the hydrous ethanol fuel lubricity has been evaluated using HFRR (High-Frequency Reciprocating Rig) test method. Wear scar diameter on 100 % of ethanol was around 700 μm which was a little better than gasoline lubricity. When the water concentration within ethanol was increased, the wear scar diameters were decreasing around 330 μm. Considering this phenomenon by the fuel viscosity, the viscosity of hydrous ethanol is growing with increasing water concentration up to 50-60 %. It seems that lubricity of hydrous ethanol can be kept by fluid film lubrication mode up to 50-60 % of water concentration.

Oguma, Mitsuharu, Matsuno, Mayumi, Kaitsuka, Masayoshi, Higurashi, Kazuaki

Investigation of the Combustion Front Structure during Homogeneous Charge Compression Ignition Combustion via Laser Rayleigh Scattering Thermometry

2016-01-07464/5/2016

The combustion propagation mechanism of homogeneous charge compression ignition combustion was investigated using planar laser Rayleigh scattering thermometry, and was compared to that of spark-ignition combustion. Ethylene and dimethyl ether were chosen as the fuels for SI and HCCI experiments and have nearly constant Rayleigh scattering cross-sections through the combustion process. Beam steering at the entrance window limited the load range for HCCI conditions and confined the quantitative interpretation of the results to local regions over which an effective beam steering correction could be applied. The SI conditions showed a clear bimodal temperature behavior with a well-defined interface between reactants and products. The HCCI results showed large regions that were partially combusted, i.e., at a temperature above the reactants but below the adiabatic flame temperature. Dual-imaging experiments confirm that the burned region was progressing towards the fully burned state. This suggests that combustion is a distributed (spatially) ignition process. There were, however, a significant number of regions of the HCCI temperature field that had relatively steep temperature gradients, which could signify the presence of a local laminar flame structure. Thus, it appears that both combustion modes are contributing to the combustion propagation mechanism for HCCI combustion.

Blessinger, Matthew, Ghandhi, Jaal

Investigation of Fuel Effects on In-Cylinder Reforming Chemistry Using Gas Chromatography

2016-01-07534/5/2016

Negative Valve Overlap (NVO) is a potential control strategy for enabling Low-Temperature Gasoline Combustion (LTGC) at low loads. While the thermal effects of NVO fueling on main combustion are well-understood, the chemical effects of NVO in-cylinder fuel reforming have not been extensively studied. The objective of this work is to examine the effects of fuel molecular structure on NVO fuel reforming using gas sampling and detailed speciation by gas chromatography. Engine gas samples were collected from a single-cylinder research engine at the end of the NVO period using a custom dump-valve apparatus. Six fuel components were studied at two injection timings: (1) iso-octane, (2) n-heptane, (3) ethanol, (4) 1-hexene, (5) cyclohexane, and (6) toluene. All fuel components were studied neat except for toluene - toluene was blended with 18.9% nheptane by liquid volume to increase the fuel reactivity. Additionally, a gasoline surrogate matching the broad molecular composition of RD587 gasoline was formulated using the chosen fuel palette and tested. The energy content of the injected fuel mass was kept constant for the sampled NVO cycle and the excess oxygen was relatively low (2.4%) compared to previous studies by the authors. The later injection timing studied resulted in useable recovered fuel energy near 70% and improved reformate yield of hydrogen and C1-C4 hydrocarbons compared to the earlier injection timing for all fuels except toluene/n-heptane. Analysis of the RD587 surrogate reformate compared to the individual component reformates suggests that fuel component interactions depend on injection timing, potentially through the in-cylinder equivalence ratio distribution.

Wolk, Benjamin, Ekoto, Isaac, Northrop, William

HEUI Injector Modeling and ROI Experiments for High Injection Pressure of Diesel and Dimethyl Ether (DME)

2016-01-08554/5/2016

Dimethyl Ether (DME) is considered a clean alternative fuel to diesel due to its soot-free combustion characteristics and its capability to be produced from renewable energy sources rather than fossil fuels such as coal or petroleum. To mitigate the effect of strong wave dynamics on fuel supply lines caused due to the high compressibility of DME and to overcome its low lubricity, a hydraulically actuated electronic unit injector (HEUI) with pressure intensification was used. The study focuses on high pressure operation, up to 2000 bar, significantly higher than pressure ranges reported previously with DME. A one-dimensional HEUI injector model is built in MATLAB/SIMULINK graphical software environment, to predict the rate of injection (ROI) profile critical to spray and combustion characterization. The outputs of model are compared with experimental ROI and injection duration data of both diesel and DME at injection pressures ranging from 750 to 2000 bar for single-hole and multi-hole nozzles. DME was found to have, with respect to diesel, longer injection delays leading to shorter injection durations for same injector command. The DME ROI profiles show that the volumetric flowrates are higher than those of Diesel. ROI profiles from the model are used as an input in CFD simulation to predict spray penetration, which are compared with spray images of both fuels captured in a combustion vessel thus providing a useful validation process for the CFD model.

Zhu, Xiucheng, Limbu, Sanjeet, Cung, Khanh, De Ojeda, William, Lee, Seong-Young

Characteristics of Formaldehyde (CH ₂ O) Formation in Dimethyl Ether (DME) Spray Combustion Using PLIF Imaging

2016-01-08644/5/2016

Recognition of Dimethyl Ether (DME) as an alternative fuel has been growing recently due to its fast evaporation and ignition in application of compression-ignition engine. Most importantly, combustion of DME produces almost no particulate matter (PM). The current study provides a further understanding of the combustion process in DME reacting spray via experiment done in a constant volume combustion chamber. Formaldehyde (CH2O), an important intermediate species in hydrocarbon combustion, has received much attention in research due to its unique contribution in chemical pathway that leads to the combustion and emission of fuels. Studies in other literature considered CH2O as a marker for UHC species since it is formed prior to diffusion flame. In this study, the formation of CH2O was highlighted both temporally and spatially through planar laser induced fluorescence (PLIF) imaging at wavelength of 355-nm of an Nd:YAG laser at various time after start of injection (ASOI). The injection pressure was kept at 750 bar using a single-hole injector with diameter of 180 μm. The formation of CH2O is also correlated with time of ignition and flame region using other optical diagnostics including photodiode and natural flame luminosity, respectively. Additionally, kinetic modeling and CFD were used in order to explain further and confirm the combustion process and species formation (particularly, CH2O) in the DME flame. Both experimental and numerical results showed that CH2O is formed mostly prior to flame ignition at upstream region before liftoff length.

Cung, Khanh, Zhu, Xiucheng, Moiz, Ahmed Abdul, Lee, Seong-Young, De Ojeda, William

Compatibility of Dimethyl Ether (DME) and Diesel Blends with Fuel System Polymers: A Hansen Solubility Analysis Approach

2016-01-08354/5/2016

The compatibility of notable infrastructure elastomers and plastics with DME and its blends with diesel fuel were examined using solubility analysis. The elastomer materials were fluorocarbon, acrylonitrile butadiene rubber (NBR), styrene butadiene (SBR), neoprene, polyurethane and silicone. Plastic materials included polyphenylene sulfide (PPS), polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyoxymethylene (POM), polybutylene terephthalate (PBT), polypropylene (PP), high density polyethylene (HDPE), along with several nylon grades and thermosetting resins. These materials have been rigorously studied with other fuel types, and their volume change results were found to correspond well with their predicted solubility levels. A Hansen solubility analysis was performed for each material with DME, diesel, and blends of both fuel components. The results for the elastomers indicate that DME and its blends with diesel fuel will offer improved compatibility with NBR and SBR materials. Silicone, neoprene and polyurethane show similar solubility potential for any combination of DME and diesel, so no degradation is expected with DME. In contrast, fluorocarbon can be expected to become increasingly incompatible with increased DME concentration. In general, the solubility analysis also indicated that many of the plastic materials can be expected to have good to excellent compatibility with DME and its blends with diesel fuel. The analysis also indicated that polyester resins should exhibit high solubility (and therefore high swelling) in both diesel and DME. However, previous empirical results showed that this result was not an accurate reflection of polyester resin performance in diesel fuel.

Kass, Michael D., Daw, Charles

Modelling Ignition Processes of Palm Oil Biodiesel and Diesel Fuels Using a Two Stage Lagrangian Approach

2015-01-18619/1/2015

Designing advanced combustion engines requires a better understanding of the physical and chemical processes occurring during spray combustion. In this study, the ignition characteristics of conventional diesel and palm biodiesel fuels were simulated using the two-stage Lagrangian (TSL) simulation, a zero dimensional (0-D) modeling technique. For the diesel fuel surrogate, a detailed chemical kinetic model for n-heptane from LLNL (Lawrence Livermore National Laboratory), with 550 chemical species and 2450 elementary reactions was utilized. For the palm biodiesel, detailed mechanism (4800 species and 2450 elementary reactions) for the 5 basic biodiesel components; methyl palmitate, methyl stearate, methyl oleate, methyl linoleate and methyl linolenate was used. Also, simulations were performed using a reduced mechanism (115 species and 460 reactions) for surrogates of palm oil biodiesel comprising mixtures of methyl decanoate, methyl decenoate and n-heptane. The simulated data were validated against published experimental results in a constant volume combustion chamber. Validations were performed at an ambient density of 15kg/m3 and injections pressure condition of 100, 200, and 300 MPa. For both the diesel and biodiesel, the predicted ignition delay agrees with the trend obtained in the experiment at all injection pressures. The TSL model was further employed to investigate the chemical processes responsible for controlling the overall ignition under various conditions. Furthermore, the effects of exothermicity, ambient pressure, and ambient oxygen concentration on first stage ignition were studied.

Alfazazi, Adamu, Sarathy, Mani, Kuti, Olawole Abiola

An Experimental Study of Injection and Combustion with Dimethyl Ether

2015-01-09324/14/2015

DiMethyl Ether (DME) has been known to be an outstanding fuel for combustion in diesel cycle engines for nearly twenty years. DME has a vapour pressure of approximately 0.5MPa at ambient temperature (293K), thus it requires pressurized fuel systems to keep it in liquid state which are similar to those for Liquefied Petroleum Gas (mixtures of propane and butane). The high vapour pressure of DME permits the possibility to optimize the fuel injection characteristic of direct injection diesel engines in order to achieve a fast evaporation and mixing with the charged gas in the combustion chamber, even at moderate fuel injection pressures. To understand the interrelation between the fuel flow inside the nozzle spray holes tests were carried out using 2D optically accessed nozzles coupled with modelling approaches for the fuel flow, cavitation, evaporation and the gas dynamics of 2-phase (liquid and gas) flows. And to understand the spray characteristics tests were carried out using constant volume vessel. For a spray observation, two methods were used a shadowgraph and a diffuse forward scatter method to obtain both gaseous phase and liquid phase of DME. Tests were then run on a single cylinder engine to determine the differences in combustion with the differing hole shapes as well as extra high injection pressure. Results showed that the different nozzle hole shapes changed the flow and the cavitation tendency. And these characteristics be utilized for an optimaization of the spray and combustion

Sasaki, Satoru, Kato, Masaaki, Yokota, Takamasa, Konno, Mitsuru, Gill, Denis

Experimental and Kinetic Study on Ignition Delay Times of Diethyl Ether

2015-01-08974/14/2015

Ignition delay times of Diethyl Ether (DEE) were measured behind reflected shock waves for the temperatures from 1050 to 1600 K, pressures of 1.2, 4 and 16 atm and equivalence ratios of 0.5 and 1.0. Result shows that the ignition delay times increase with the increase of the equivalence ratio and the decrease of the pressure. The only literature DEE mechanism (Yasunaga et al. model) was employed to simulate the experimental data and result shows that the model gives reasonable prediction on lean mixtures, while the prediction on stoichiometric mixtures is slightly higher. Sensitivity analysis was conducted to pick out the key reactions in the process of DEE ignition at high and low pressures, respectively. Reaction pathway analysis shows that the consumption of DEE is dominated by the H-abstraction reactions. Through linear analysis, a correlation for the DEE ignition data was obtained. Using this correlation, the measured DEE data were compared to the literature correlations of DME and n-butane, for they have the similar molecular structure. Result shows that DEE has the strongest overall reactivity among the three fuels, while that of DME and n-butane are comparable. Sensitivity analysis and radical pool analysis were conducted to gain a further understanding of the ignition process of the three fuels.

Zhang, Zihang, Hu, Erjiang, Peng, Cheng, Huang, Zuohua

A Study of Supercharged HCCI Combustion Using Blended Fuels of Propane and DME

2014-32-000511/11/2014

Homogeneous Charge Compression Ignition (HCCI) has attracted a great deal of interest as a combustion system for internal combustion engines because it achieves high efficiency and clean exhaust emissions. However, HCCI combustion has several issues that remain to be solved. For example, it is difficult to control engine operation because there is no physical means of inducing ignition. Another issue is the rapid rate of heat release because ignition of the mixture occurs simultaneously at multiple places in the cylinder. The results of previous investigations have shown that the use of a blended fuel of DME and propane was observed that the overall combustion process was delayed, with that combustion became steep when injected propane much. This study focused on expanding the region of stable engine operation and improving thermal efficiency by using supercharging and blended fuels. The purpose of using supercharging were in order to moderated combustion. In addition, the purpose of using blended gaseous fuels were find out effective use of gaseous fuels. Low-carbon gaseous fuels with clean emissions were used as the test fuels. The specific fuels used were dimethyl ether (DME, cetane number of 55 or higher) that exhibits pronounced low-temperature oxidation reactions. Propane (cetane number of 5) that does not exhibits low-temperature reaction readily and that is a principal component of liquefied petroleum gas. A spectroscopic measurement technique was used to investigate the combustion in detail by obtain the light emission spectra of the combustion flame. The characteristics of the reaction products were investigated by analyzing the exhaust gas components using Fourier transform infrared spectroscopy. The results shows that the quantity of DME and propane ratio injected determines the ignition timing, the engine load level can be adjusted by means of the quantity of propane injected to achieve ignition near top dead center. In addition, combustion became moderate by supercharging.

Mochizuki, Keisuke, Shima, Takahiro, Suzuki, Hirotaka, Ishikawa, Yoshihiro, Iijima, Akira, Yoshida, Koji, Shoji, Hideo

Composition Effects on Thermo-Physical Properties and Evaporation of Suspended Droplets of Biodiesel Fuels

2014-01-276010/13/2014

From the energy security and environment standpoint, the biodiesel fuels derived from vegetable oils or animal fats appear to be promising alternative to fossil diesel. Although the engine experiments prove their viability, the scientific data base for characterizing biodiesel combustion is limited. Detailed studies on the characterization of biodiesel fuels and their effects on fundamental engine processes like droplet evaporation and combustion are essential. The present study evaluates the useful thermo-physical properties and droplet evaporation characteristics of biodiesel fuels. The droplet evaporation measurements are carried out using suspended droplet experiments on five biodiesel fuels of Indian origin viz. jatropha, pongamia (karanja), neem, mahua and palm. The droplet evaporation rates of these fuels are related to properties such as binary diffusivity and molecular weight, which in turn depend on their fatty acid composition. It is observed that palm methyl ester has the highest evaporation constant value of 0.1634 mm2/s and thus the lowest life time among the biodiesel fuels investigated. This value is attributed to its lowest molecular weight and highest molecular mass diffusivity. On the other hand, a reverse trend is observed for karanja biodiesel resulting in the highest lifetime among the fuel tested.

Manjunath, More, Prakash, Pratheesh, Raghavan, Vasudevan, Mehta, Pramod S.

Effects of a Blend of Eethanol and Ethylene Glycol Dimethyl Ether on Fuel Properties and Engine Performances When Used as Clean Diesel Fuel Additive

2014-01-277110/13/2014

In the present study, ethanol and EGDE were mixed in 1:1 proportion by volume to make a new oxygenate blend as a clean diesel fuel additive. Results showed that the oxygenate blend is miscible with diesel fuel within a wide proportion range above 0°C. With the increase in the content level of the oxygenate blend in diesel fuel, viscosity decreases near linearly, smoke point increases, closed flash point decreases rapidly below 5% of the oxygenate blend by volume in diesel fuel and then maintains unchanged with the oxygenate blend content increasing, and solidifying point of 0# diesel fuel decreases. When a engine was fueled with a diesel fuel added with 20% (v) of the oxygenate blend operating under partial load at 1800rpm and 2300rpm respectively, smoke emissions can be lessened by about 50% to 80%, and CO can be reduced by up to about 70%. NOx emissions generally increase slightly. Power output drops by 0.5%-1.5%, fuel consumption increases, while energy economy is enhanced by 1.8%-9.8%.

Guo, Hejun, Zheng, Li

An Investigation into the Effect of Fuel Injection System Improvements on the Injection and Combustion of DiMethyl Ether in a Diesel Cycle Engine

2014-01-265810/13/2014

For nearly twenty years, DiMethyl Ether has been known to be an outstanding fuel for combustion in diesel cycle engines. Not only does it have a high Cetane number, it burns absolutely soot free and produces lower NOx exhaust emissions than the equivalent diesel. However, the physical properties of DME such as its low viscosity, lubricity and bulk modulus have negative effects for the fuel injection system, which have both limited the achievable injection pressures to about 500 bar and DME's introduction into the market. To overcome some of these effects, a common rail fuel injection system was adapted to operate with DME and produce injection pressures of up to 1000 bar. To understand the effect of the high injection pressure, tests were carried out using 2D optically accessed nozzles. This allowed the impact of the high vapour pressure of DME on the onset of cavitation in the nozzle hole to be assessed and improve the flow characteristics. CFD simulation was also used to assist in the interpretation of the 2D test results. Tests were then run on a single cylinder engine to determine the differences in combustion with the differing hole shapes as well as extra high injection pressure. Initial screening of the injection nozzles using DoE methods was carried out at various injection timings, pressures, air flows and EGR rates. The tests were carried out using a simplified WHSC and JE05 cycle to investigate the effects of these changes on fuel consumption and emissions at engine out NOx levels between 0.4g/kW.h and 9.0g/kW.h and to judge how the resulting emissions would affect aftertreatment system choices. Results showed that the higher injection pressure combined with high EGR rates could bring an improvement in DME combustion, while the different nozzle hole shapes changed the flow characteristics and the cavitation tendency of the sprays which also can be utilized for an optimization of the mixture preparation and combustion.

Gill, Denis W., Ofner, Herwig, Stoewe, Carsten, Wieser, Karl, Winklhofer, Ernst, Kato, Masaaki, Yokota, Takamasa, Weber, Jost

Experimental Investigation on the Performance and Exhaust Emission of Biogas-Diesel Dual-Fuel Combustion in a CI Engine

2014-01-268910/13/2014

The crude oil depletion, as well as aspects related to environmental pollution and global warming has caused researchers to seek alternative fuels. Biogas is one of the most attractive available fuels. It is of great interest both economically and ecologically. However, it faces problems that may compromise its industrial use. The dual-fuel engines have been investigated as a technique for the recovery of these gases and finding solutions to these problems. In the present work, performance and emissions of a direct injection diesel engine were first evaluated in conventional mode and dual fuel mode. The effect of biogas composition, based on methane content, is then examined. Also, dual fuel operation with regard to knock is investigated. The results show that, up to 95% of engine full load, the brake thermal efficiency (BTE) is lower in dual fuel mode. In terms of the specific consumption, although at high load the gap is much less, it is more significant in case of dual fuel mode. This is justified by the low energy content of biogas in comparison with diesel fuel. In addition, the particulate emissions are drastically reduced compared to conventional diesel operating mode. Thus, the biogas can be used in the dual fuel engines with very attractive performance. Regarding the effect of the biogas composition, the results showed that a biogas with 70% of methane offers the best performance compared to biogas fuels with 50, 60 and 80% of methane content. On the other hand, biogas fuels showed good resistance to knocking since measured torque at the occurrence of knock onset is higher than the maximum torque recorded for conventional diesel. This resistance is even higher when the percentage of carbon dioxide is higher.

Lounici, Mohand Said, Loubar, Khaled, Tazerout, Mohand, Balistrou, Mourad, Tarabet, Lyes

The Analysis of Energy Conversion Efficiency in SI Engines for Selected Gaseous Fuels

2014-01-269210/13/2014

The analysis of the overall performance of the engine powered by selected gaseous fuels has been presented in this paper. Primary objective of the research was to determine the influence of fuel type on efficiency of energy conversion in the tested engine. The scope of the research featured: application low-carbon fuels, use of DME as a renewable fuel in blends with LPG. The use of low-carbon gaseous fuels gives the opportunity to reduce exhaust gases emissions. The basic assumption in the presented research was the use of gaseous fuels, for which the main component is methane. The main problem taken into consideration was excessive duration of the combustion process, which is one of the causes of the engine overall efficiency reduction when running on gaseous fuels. This issue becomes even more important due to the lower heating value of natural gas (methane) when compared to conventional fuels. One of possible solutions is the use of fuel blends, e.g. methane-enriched hydrogen as an activator of the combustion process [18]. Authors have chosen in this case eight methane/hydrogen blends, with various hydrogen shares (by volume): 0% (pure methane), 5%, 10%, 15%, 20%, 30%, 40% and 50%. Another interesting alternative considered by authors was dimethyl ether (DME). Due to its properties, it is recently becoming a more popular fuel. The high cetane number (about 55) allows its easy application for diesel engines propulsion additionally featuring low sooting propensity. Considering that other DME properties are very similar to those of petroleum based hydrocarbon gases, it is possible to effectively use it in the SI engines. One of DME applications presented by authors is a fuel blend based on LPG. The research program provided the use of fuel blends featuring DME mass fraction varying from 0 to 26%. The research project allowed the verification of simulation studies carried on the basis of mathematical model, with the real data from a 4 cylinders 1600cm3 SI engine. This made it possible to conduct a precise analysis of combustion process for all the tested fuels. The relationships between various components of energy balance in the tested engine have also been interpreted.

Flekiewicz, Marek, Kubica, Grzegorz, Flekiewicz, Bartosz

Numerical characterization of two alternative-to-diesel fuels using a moments spray model

2014-01-14224/1/2014

The need to evaluate other fuel types for use in internal combustion engines has increased with the concerns related to the limited availability of fossil fuels and the need to reduce emissions. In this assessment, two alternative-to-diesel fuels, dimethyl ether and biodiesel, are characterized by their spray tip penetration at different axial distances from the nozzle tip and at different ambient pressure values. The sauter mean diameter values at various axial distances from the injector tip are also evaluated. A novel diesel spray model that presents the hydrodynamics features of sprays from the moments derived from a Gamma size distribution and the droplet-size distribution function, rather than from droplet-size classes, is used for the numerical predictions. The results indicate that the spray tip penetration for both fuels increases rapidly initially but the rate of increase slows at the later stages of the fuel injection. However, with increases in the ambient pressure values the predicted tip penetration decreases for both fuel sprays. Larger spray tip penetration and droplet size values are also predicted for the biodiesel fuel compared to the dimethyl ether fuel. These suggest better atomization at the given conditions for the dimethyl ether fuel spray. The predictions correctly capture the trends from the experimental data. However, there are differences between the predicted and experimental values at the early spray injection times. Thus, specific analytical models for the initial droplet size distribution and droplet break-up regime for the alternative fuel sprays might be required to improve the numerical model.

Emekwuru, Nwabueze

Life Cycle Land Requirement, Energy Consumption and GHG Emissions of Biodiesel Derived from Microalgae and Jatropha curcas Seeds in China

2014-01-19644/1/2014

The aim of this study is to evaluate the land requirement, energy consumption and GHG (greenhouse gases) emissions of microalgal biodiesel (M-BD) and Jatropha curcas seeds (J-BD) based biodiesel from the perspective of life cycle assessment (LCA). Mass and energy balance was used through the whole LCA calculation for each process. Two types of biodiesel (100% biodiesel: BD100, and 20% blends of biodiesel: BD20) were assumed to be combusted in the suitable diesel engine. Displacement method was adopted to measure the co-products credits. The results showed that the land requirement of producing 1 kg biodiesel from microalgae was about 1/31 of that from Jatropha curcas seeds. The well to pump (WTP) stage for microalgal biodiesel had higher fossil energy requirement but lower petroleum energy consumption and GHG emissions compared to Jatropha curcas and conventional diesel (CD). The WTP energy efficiency for J-BD100 and M-BD 100 were 26% and 17.4%, respectively. The feedstock growing stage of microalgae and Jatropha curcas was found to be the most fossil energy-intensive stage. The WTW results showed good performance for MBD100 on petroleum consumption and GHG emissions. The high fossil energy use for microalgae BD100 was attributed to the large inputs for microalgae growth, including fertilizer and process fuels. Among feedstock, fuel and vehicle operation, the vehicle operation stage had no contribution to BD100, but had great contribution to BD20 blends. At the current technology situation, microalgae based biodiesel should break through many obstacles to make algal based biodiesel more feasible in the future.

Zhang, Tingting, Xie, Xiaomin, Huang, Zhen

Experimental and Modeling Study on Auto-Ignition of DME/n-Butane Blends under Engine Relevant Pressure

2014-01-14704/1/2014

In this study, the ignition delay times of DME/n-C4H10 fuel blends (neat DME, 50/50 and neat n-C4H10) diluted with argon were measured behind reflected shock waves. The experiments were performed in the temperature range of 1250 - 1600 K, at pressure of 2.0 MPa and equivalence ratios from 0.5 to 2.0. A latest kinetic mechanism NUIG Aramco Mech 1.3 was validated against the present ignition data and used to conducted chemical kinetic analysis. Different equivalence-ratio-dependent was exhibited at different temperature regimes for DME, n-C4H10, and their blend. Fuel flux analysis, sensitive analysis and mole fraction analysis were carried out for understanding the interaction between the ignition chemistries of DME and n-C4H10.

Jiang, Xue, Zhang, YingJia, Pan, Lun, Man, XingJia, Huang, Zuohua

A Computational Study of the Effects of EGR and Intake-Pressure Boost on DME Autoignition Characteristics over Wide Ranges of Engine Speed

2014-01-14614/1/2014

This study has been computationally investigated how the DME autoignition reactivity is affected by EGR and intake-pressure boost over various engine speed. CHEMKIN-PRO was used as a solver and chemical-kinetics mechanism for DME was utilized from Curran's model. We examined first the influence of EGR addition on autoignition reactivity using contribution matrix. Investigations concentrate on the HCCI combustion of DME at wide ranges of engine speeds and intake-pressure boost with EGR rates and their effects on variations of autoignition timings, combustion durations in two-stage combustion process in-detail including reaction rates of dominant reactions involved in autoignition process. The results show that EGR addition increases the combustion duration by lowering reaction rates. It was also found that autoignition timings were very sensitive to boost pressure due to boost pressure enhances the reactivity of intermediate species but combustion durations dominantly depend on the EGR addition. Also, high engine speed under EGR addition increases the burn duration greatly. Finally, the combined effects of EGR and boost pressure over wide ranges of engine speed are showed that it is the beneficial method to operate HCCI engine without knock at high load due to substantial reduction of peak of heat-release rate by controlling low temperature heat release.

Jamsran, Narankhuu, Lim, Ocktaeck, Iida, Norimasa

Economics of Transportation Hydrocarbon Fuels and Environmental Regulations with Conceptual Solutions - Carbon-Neutral and Carbon-Negative Synfuels

2014-01-19434/1/2014

Of all current proposals for sustainable transportation, the assumption is energy scarcity when there are economically favorable alternatives using existing technology. This paper explores the economics of a sustainable transportation energy pathway that provides carbon-neutral and carbon-negative synthetic fuel derived from seawater as the feedstock and power via Ocean Thermal Energy Cycle (OTEC). Seawater-based synthetic fuel is naturally carbon-neutral - different synthesis processes can yield hydrogen, methane, methanol and ethanol as well as gasoline, diesel or jet fuel - and is carbon-negative when combined with aquaculture. Methanol is favored as a fuel as it requires relatively lower capital investment; can be easily transported and stored; can be used as a feedstock to many chemical processes that currently rely on petrochemicals; and can be coproduced with or converted to dimethyl ether. This paper proposes a new process that for the first time marries OTEC-power and seawater-based-methanol synthetic fuel generation. The proposed process is optimized for highest product yield for a given capital investment, in that operating costs and therefore product costs are dominated by capital cost amortization. The methanol fuel produced by this process within the amortization period has a cost per unit of energy potentially comparable to petroleum-derived gasoline or diesel fuel and post-amortization to natural gas. The economics of this new process is compared to prior synthetic methanol processes proposed by Meyer Steinberg and William Avery.

Bucknell, John R.

Effect of POMDME Blend on PAH Emissions and Particulate Size Distribution from an In-Use Light-Duty Diesel Engine

2014-01-19514/1/2014

Polyoxymethylene dimethyl ether (POMDME) is a synthetic fuel from alternative energy sources, which can be blended in any ratio with petroleum diesel fuel. The regulated and non-regulated emissions, especially polyaromatic hydrocarbons (PAH) and particle number size distribution (PNSD), from an old Euro-3 diesel engine fueled with a 7,5% blend of POMDME in commercial diesel fuel were measured and compared to the base diesel fuel, after adjusting exhaust gas ratio (EGR) in order to match the level of NOx emission. The experimental results show a significant reduction in soot and particulate matter (PM) emissions. The number of particles smaller than 30 nm is slightly increased at low speed and low load operating conditions, while at high speed the number concentration of particles larger than 30 nm is reduced. The PAH emissions were found higher for the oxygenated fuel blend than for the base fuel. This result is consistent with the exhaust gas temperature profiles during the PAH sampling which suggest that the oxidation catalyst might have a slightly lower catalytic activity when using this oxygenated fuel.

Pellegrini, Leonardo, Patrini, Renata, Marchionna, Mario

Investigation on the Effects of Dimethyl Ether Blending to Bunker Oil for Marine Diesel Engine Use

2013-01-265910/14/2013

Fossil fuels are the dominant source of energy today with the problem of their supply depletion becoming a global issue. Since stable energy supplies are necessary in order to sustain the activities of mankind, conservation of petroleum fuel and finding an appropriate substitute are critical. Additionally, solutions to global environmental pollution problems are simultaneously needed, such as the Kyoto protocol for global warming. The aim of this study is to investigate whether the combustion state of bunker oil can be improved by the mixing of DME (dimethyl ether), which is considered as a possible alternative fuel. The kinematic viscosity of DME blended fuel, as well as the engine performance characteristics of single cylinder direct injection diesel engine, was measured experimentally. In the kinematic viscosity measurement, a pressure cell type viscosity measurement system was established in order to apply the volatile DME blended fuel. The nozzle opening pressure was changed in order to obtain different injection characteristics in the diesel engine. For diesel engine applications, DME has a problem of poor lubricity due to its lower viscosity and Bunker oil has the problems of exhaust emissions and high viscosity. Of special note, Bunker oil needs to be heated up over 100 degrees centigrade to reduce its viscosity applicable for marine diesel engine use. In the present study, Bunker oil can be used without heating in diesel engines by mixing with DME.

Ryu, Younghyun, Dan, Tomohisa

De-NOx Performance of Combined System of Reforming Catalyst and LNT for a DME Engine

2013-01-259210/14/2013

Dimethyl ether(DME) is easily reformed into H2, since the chemical structure of DME does not feature direct C-C bonds, in contrast to diesel fuel. We have researched reforming catalysts for effectively generating H2 from the exhaust gases of a DME engine. The objective of this study is to evaluate the de-NOx performance of a combined system of RC(Reforming Catalyst) and LNT(Lean NOx Trap) for a DME engine according to reforming catalysts. The H2 generation of the reforming catalyst was observed under various conditions. CAT-A, CAT-B and CAT-C were prepared as reforming catalysts, and OC(Oxidation Catalyst) and LNT (Lean NOx Trap) were examined as commercial catalysts. The CAT-A catalyst has a higher amount of acid sites compared to the CAT-B and CAT-C catalysts. The CAT-A which is a mixing of mordenite and γ-Al2O3, has the highest H2 yield. However, the H2 yield decreased in the reforming reaction when CO2, NO and O2 coexisted. The NOx conversions of the combined system of fresh and hydrothermally aged CAT-A+LNT are higher by about 8% and 6% than those of the LNT. The NOx conversion over the combined system of CAT-A+LNT applied to the DME engine has been improved at high rpm-load conditions compared to the LNT.

Choi, Byung-Chul, Park, Syungyong, Lee, Young-Jae

Numerical Study on Emission Characteristics of High-Pressure Dimethyl Ether (DME) under Different Engine Ambient Conditions

2013-01-03194/8/2013

Particular matter (PM) has been greatly concerned over the recent decades due to the constantly increasing restriction on its effect on environmental aspect. Oxygenated fuel such as dimethyl ether (DME) has been known to have beneficial impact on diesel engine emissions in terms of zero soot formation. In current study, under several ambient conditions including surrounding gas temperature and oxygen percentages, soot and emission formation of DME spray is investigated to provide a comparison with other diesel surrogate (n-heptane) and JP-8 surrogate fuels. One important work is to develop a number of chemical kinetic mechanisms with soot chemistry including the growth of polycyclic aromatic hydrocarbon (PAH) and nitro oxides (NOx) formation. Using the developing detailed mechanisms, several numerical approaches were introduced to provide an integrated picture of emission formations. First, the Two-Stage Lagrangian (TSL) capable of implementing mixing effect of air/fuel mixture was used with analytical/experimental input of flame lift-off lengths. Secondly, the CFD simulation was performed to provide the information of the spray such as temperature, user-defined specie concentrations, and flame structure. From this study, DME have the lowest soot and NOx comparing to n-heptane and JP-8 surrogate fuels. The effects of injection pressure and oxygen level were confirmed to be critical in the formation of soot and NOx under engine conditions.

Cung, Khanh, Bhagat, Meghraj, Zhang, Anqi, Lee, Seong-Young

Emission Performance of Neat and Blended Polyoxymethylene Dimethyl Ethers in an Old Light-Duty Diesel Car

2013-01-10354/8/2013

Polyoxymethylene dimethyl ether (POMDME) is a new alternative fuel that can be produced from waste biomasses and tailored through the distribution of oligomers to fit into the distillation range of diesel fuel. Since one potential advantage of alternative fuels is that they could reduce emissions also from old in-use vehicles without waiting for their replacement, we have measured and evaluated the emission performance of neat POMDME and a blend of 10% POMDME and 90% commercial diesel fuel in an old Euro-2 diesel car over the NEDC driving cycle. As compared to the reference diesel fuel, the experimental results show a significant reduction in PM emissions already with the 10% blend, i.e., −18%, and even more pronounced with the neat POMDME, i.e., −77%. With this latter the PM emission reached below the Euro 4 limit. The composition of PM was quite different for the two extreme fuels; being mostly VOF from lube oil for the neat POMDME, while mostly soot in the case of diesel fuel. Possibly due to high frequency of C-O bonds in its molecular structure, the use of the neat POMDME resulted in higher emission of CO and formaldehyde that could not be compensated by the catalytic performance of the aged oxidation catalyst (DOC) of the vehicle. The neat POMDME showed also increased NOx emissions likely due to its higher combustion temperature as found in previous experiments. The emission of HC was not significantly affected by the fuel type. In conclusion, this investigation demonstrated that the use of neat POMDME is an effective way to reduce the PM from in-use old vehicles without diesel particulate filter (DPF). However, care must be taken to ensure the maintenance of an effective DOC system to reduce the emissions of CO and aldehydes.

Pellegrini, Leonardo, Marchionna, Mario, Patrini, Renata, Florio, Salvatore

Design of DME-Diesel Fuel Supply System for Non-Gasification

2013-01-11524/8/2013

As efficient and low-pollution alternative fuel, dimethyl ether (DME) has shown its excellent performance of combustion and emissions. There is a phenomenon of DME gasification in the in-line fuel pump of DME-diesel engine. DME gasification can result in “vapor lock” and serious inequality of the fuel supply in DME-diesel fuel system. This paper presents a simple solution to improve DME gasification in DME-diesel fuel system. The key feature of the solution is just a bypass check valve, which is assembled between the intake fuel supply and the plunger chamber of the in-line pump. DME gasification in the in-line pump can be effectively eliminated by means of the bypass valve design. The feasibility of the solution design is validated against AVL-HYDSIM simulations of both fuel systems, including the baseline of DME-diesel duel fuel system and the fuel system with the bypass check valve, on factors such as intake fuel pressure, DME content ratio, engine speed, DME vapor pressure and so on. The research shows that (1) the design of the bypass check valve is one solution to eliminate DME gasification in the in-line pump fuel-injection system, and (2) DME gasification is inevitable in the plunger chamber of the in-line pump due to the powerful vacuum suction of the plunger, and (3) there is less effect of intake fuel pressure and DME fuel content ratio on the elimination of the gasification in the in-line pump, because the cause of DME gasification is the structure of the plunger and barrel assembly in the in-line pump fuel-injection system.

Dong, Jian, Pan, Qingchuan, Pan, Zhixiang, Yang, Dong

Study on Ignition Delay Times of DME and n-Butane Blends

2013-01-11464/8/2013

Ignition delay times of stoichiometric dimethyl ether (DME) and n-butane blends were measured in a shock tube at varied DME blending ratios, temperatures and pressures. Simulation work extended the pressure to 20 atm by using Chemkin and NUI C4_47 mechanism. The experimental ignition delay times of DME/n-butane were obtained at different DME blending ratios. Measured ignition delay times were compared to simulations based on NUI C4_47 mechanisms by Curran et al. The mechanism predicts the magnitude of ignition delay times well and a slightly higher activation energy. The ignition delay times increase linearly with the increase of 1000/T and the overall activation energy keeps almost the same value at the conditions in this study. Increasing pressure decreases exponentially the ignition delay time. Ignition delay time decreases linearly with the increase of DME blending ratio. The peak mole fractions of H radicals increase, and the timing at peak value of H radicals advances as DME increases. Sensitivity analysis shows that the dominant reactions affecting ignition delay time are mainly the small molecule elementary reactions.

Hu, Erjiang, Huang, Zuohua, Jiang, Xue, Zhang, Jiaxiang

Effects of Fuel Compositions on Diesel Engine Performance Using Ammonia-DME Mixtures

2013-01-11334/8/2013

Various mixtures of ammonia (NH₃) and dimethyl ether (DME) were tested in a diesel engine to explore the feasibility of using ammonia as an alternative, non-carbon fuel to mitigate greenhouse gas emissions. The original diesel fuel injection system was replaced with a new system for injecting ammonia-DME mixtures into the cylinder directly. The injection pressure was maintained at approximately 206 bar for various fuel mixtures including 100% DME, 60%DME-40%NH₃, and 40%DME-60%NH₃ (by weight). As ammonia content was increased in the fuel mixture, the injection timing needed to be advanced to ensure successful engine operation. It was found that cycle-to-cycle variation increased significantly when 40%DME-60%NH₃ was used. In the meantime, combustion of 40%DME-60%NH₃ exhibited HCCI characteristics as the injection timing ranged from 90 to 340 before top-dead-center (BTDC). Emissions data show that soot emissions remained extremely low for the fuel mixtures tested. On the other hand, as ammonia concentration increased, CO and HC emissions increased due to the low combustion temperature of ammonia, and NOx emissions also increased due to the formation of fuel NOx. Exhaust ammonia emissions also increased as ammonia content increased in the fuel mixture.

Ryu, Kyung Hyun, Zacharakis-Jutz, George, Kong, Song-Charng

DPF's Regeneration Procedures and Emissions with RME Blend Fuels

2012-01-08444/16/2012

The fatty acid methyl esters (FAME's) - in Europe mostly RME (Rapeseed methyl ester) - are used in several countries as alternative biogene diesel fuels in various blending ratios with fossil fuels (Bxx). Questions often arise about the influences of these biocomponents on the modern exhaust aftertreatment systems and especially on the regeneration of diesel particle filters (DPF). In the present work different regeneration procedures of DPF systems were investigated with biofuels B0, B20 & B100. The tested regeneration procedures were: - passive regenerations: DOC + CSF; CSF alone, and - active regenerations: standstill burner; fuel injections & DOC. During each regeneration on-line measurements of regulated and unregulated emission components (nanoparticles & FTIR) were conducted. It can be stated that the increased portion of RME in fuel provokes longer time periods to charge the filter with soot. This is due to the lower PM emissions of the engine, as well as to the higher reactivity and higher SOF portion of the particle mass from RME. With the passive regeneration system with stronger catalytic activity (DOC + CSF) there is a stronger NO₂ production with B100 and due to the NO₂-supported oxidation of PM the balance point temperature is approx. 20°C lower, than with B0. For the active regenerations the time histories of emissions and temperatures are closely connected with the chosen regeneration strategy - switching, timing and intensity (of burner, or fuel aerosol generator). A higher portion of biocomponent usually causes a stronger breakdown of the instantaneous DPF filtration efficiency during the regeneration procedure - this is an effect of stronger artifact of spontaneous condensation after DPF. In summary there is no negative short-term effect of bio-blend fuels on the investigated regeneration procedures. Some recommendations for a successful long-term operation, basing on other works and literature are given at the end of the paper.

Czerwinski, Jan, Bürki, Samuel, Bonsack, Peter, Mayer, Andreas, Dimopoulos Eggenschwiler, Panayotis, Heeb, Adm Norbert, D'Urbano, Giovanni, Hermle, Sandra, Renz, Stephan

Combustion Behaviour and Emission Performance of Neat and Blended Polyoxymethylene Dimethyl Ethers in a Light-Duty Diesel Engine

2012-01-10534/16/2012

The combustion behaviour, the mechanisms of soot formation, and the emission performance of a mixture of polyoxymethylene dimethyl ethers (POMDME) oligomers with a number of oxymethylene units ranging from 3 to 5, both neat and blended at 12.5% and 50% levels with commercial diesel fuel have been investigated. The goals were a first evaluation of the POMDME impact on the diesel injector behaviour, on the combustion process as well as on the emission performance of a light duty engine. Then a brief screening on the capability to improve the NOx-PM trade-off using POMDME by means of the exhaust gas recirculation (EGR) rate increment was also assessed. Therefore, the experiments were carried out first using an injector test rig to control injection parameters, then in a transparent single-cylinder research engine with optical access for combustion visualization with spatially-resolved measurements of flame temperature and soot concentration, and finally in a light-duty multi-cylinder engine. Two operating conditions were chosen for the tests as representative of the most critical point for emission and noise optimization: engine speed of 1500 rpm and brake mean effective pressure (BMEP) of 5 bar, and 2500 rpm and 8 bar BMEP. Results from the single-cylinder engine indicate that the presence of the POMDME affects essentially the process of soot oxidation and results in a significant increase of the oxidation rate. This effect is attributed to the presence of intramolecular oxygen in the fuel which is readily available in situ and to the higher flame temperatures. The tests with the multi-cylinder engine have demonstrated that with the neat POMDME and to a lesser extent also with the 50% blend it is possible a simultaneous optimization of NOx and PM emissions and also of the noise level to a limit that could not be reached with conventional diesel fuels. For the 10-12% blend that could be used in non-dedicated engines, the reduction of PM emission was about 40%, while with higher blends and EGR recalibration in dedicated vehicle fleets very low NOx exhaust emission can be reached.

Pellegrini, Leonardo, Marchionna, Mario, Patrini, Renata, Beatrice, Carlo, Del Giacomo, Nicola, Guido, Chiara

Numerical Analysis of Combustion and Emissions Formation in a Heavy Duty DME Engine

2012-01-01564/16/2012

When using dimethyl ether (DME) to fuel diesel engines at high load and speed, applying high amounts of exhaust gas recirculation (EGR) to limit NOX emissions, carbon monoxide (CO) emissions are generally high. To address this issue, the combustion and emission processes in such engines were analyzed with the three-dimensional CFD KIVA3V code. The combustion sub-mechanism (76 species and 375 reactions) was validated by comparing simulated ignition delays and flame velocities to reference data under diesel-like and atmospheric conditions, respectively. In addition, simulated and experimentally determined rate of heat release (RoHR) curves and emission data were compared for a heavy-duty single-cylinder DME engine (displaced volume, 2.02 liters) with DME-adapted piston and nozzle geometries. The simulated RoHR curves captured the main features of the experimentally measured curves, but deviated in the premixed (higher peak) and late combustion phases (too high). The simulated NOX and CO emissions under EGR conditions were predicted well. However, CO emissions were too high under non-EGR conditions, probably because the CFD code does not capture the latest part of the combustion process accurately. Parametric equivalence ratio-temperature distributions (plotted on emission maps of CO, formaldehyde, methane, NO and soot), crank-angle-resolved emissions and RoHR curves indicate that as load and speed increase larger fractions of in-cylinder masses are located in relatively rich regions during the diffusion combustion phase, thus promoting the formation of CO, formaldehyde and methane. Consequently, to reduce these emissions the combustion system must be able to limit the formation of excessively rich conditions during later parts of the diffusion combustion phase, which can be achieved by entraining larger amounts of air in the sprays and adapting the piston bowl geometry to increase flame/air interfaces.

Salsing, Henrik, Golovitchev, Valeri, Denbratt, Ingemar

Determination Of Mixture Of Methanol And Ethanol Blends In Gasoline Fuels Using A Miniaturized NIR Flex Fuel Sensor

2011-01-19888/30/2011

Based on their 25 world-wide years experience in refining and fuel formulation using Near Infrared technology, the SP3H team has developed an innovative and miniaturized optical fuel quality sensor. The sensor output is based on an HCP matrix (HydroCarbon Profilers) and provides information on the fine chemistry of fuels such as aromatics, olefins, isoparaffins and oxygenates content and information related to the lengths of the Carbon-Carbon Chain. The goal of this study is to answer the need for new flex-fuel sensors able to provide the rate and the type of oxygenates used in different mixtures of binary and ternary blends of methanol, ethanol and gasoline for the emerging markets. This paper presents the results of the models and the accuracy of the optical sensor for the determination and prediction of Methanol-Ethanol-gasoline mixtures based on the HCP approach.

Lunati, Alain, Galtier, Oswin

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