bluuebunny/crossref_metadata_2025 huggingface dataset:
Improved Embeddability for Polymeric Bearing Overlays
Authors: Latham David , Laing Ian , Brock Ronald
Published: January 2016

Recent engine developments towards higher loads (downsizing) and thinner oil films have increased the severity of plain bearing operating conditions 1. These factors, combined with lower viscosity oils, have resulted in a greater sensitivity of bearings to damage by foreign debris particles. Traditional highly embeddable materials, such as lead, are being progressively phased out. This lead-free trend observed in the passenger car market is likely to spread to the truck market in the future. As a result, it is becoming increasingly challenging to balance the conflicting hard and soft requirements of bearing materials. Although new generations of bearing materials, particularly polymeric overlays, have shown excellent fatigue and wear capabilities 2, they would benefit from enhanced embeddability properties. This demand has led MAHLE to take a new approach with the development of a polymeric overlay material that has both hard and soft characteristics. This newly developed soft-phase co-polymer resin has been synthesized from monomers selected to give the desired properties. Conventional Polyamide-imide (PAI) monomers have been combined with Polydimethylsiloxane (PDMS) macromonomers. PDMS was selected to improve embeddability as it is softer and offers more flexibility than PAI. Via a polymerization reaction, chains of hard, fatigue resistant PAI are alternately combined with short chains of PDMS. This produces a polymer matrix which has a very fine distribution of soft phase due to the micro-phase segregation created as the soft and hard segments of neighboring polymer chains preferentially align with each other 3, 4. The relative lengths of the hard and soft sections can be ‘tuned’ to produce domains of differing size and therefore adjust the balance of properties. Experiments have been carried out varying the overall percentage of PDMS and also with the molecular weight of the PDMS segments. Initial embeddability testing has shown an improvement in embedment over current polymer products and further work is ongoing to optimize this new resin system.
Extending Lean and EGR-Dilute Operating Limits of a Modern GDI Engine Using a Low-Energy Transient Plasma Ignition System
Authors: Sevik James , Wallner Thomas , Pamminger Michael , Scarcelli Riccardo , Singleton Dan , Sanders Jason
Published: January 2016

The efficiency improvement and emissions reduction potential of lean and EGR dilute operation of spark-ignition gasoline engines is well understood and documented. However, dilute operation is generally limited by deteriorating combustion stability with increasing inert gas levels. The combustion stability decreases due to reduced mixture flame speeds resulting in significantly increased combustion initiation periods and burn durations.

A study was designed and executed to evaluate the potential to extend lean and EGR-dilute limits using a low-energy transient plasma ignition system. The low-energy transient plasma was generated by nano-second pulses and its performance compared to a conventional transistorized coil ignition system operated on an automotive, gasoline direct injection (GDI) single-cylinder research engine. The experimental assessment was focused on steady-state experiments at the part load condition of 1500 rpm 5.6 bar IMEP, where dilution tolerance is particularly critical to improving efficiency and emissions performance.

Experimental results suggest that the energy delivery process of the low-energy transient plasma ignition system significantly improves part load dilution tolerance by reducing the early flame development period. Statistical analysis of relevant combustion metrics was performed in order to further investigate the effects of the advanced ignition system on combustion stability. Results confirm that at select operating conditions EGR tolerance and lean limit could be improved by as much as 20% (from 22.7 to 27.1% EGR) and nearly 10% (from λ=1.55 to 1.7) with the low-energy transient plasma ignition system.
An Experimental and Theoretical Study of Fuel Composition on Noxious Emissions in a Natural Gas Engine Operating on Wellhead Gas
Authors: Christensen Stephen , Ajayi Kayode , Abata Duane , Carlin Kevin
Published: January 2016

The use of natural gas in spark-ignited internal combustion engines optimized for minimum emissions has repeatedly shown a significant reduction in exhaust emissions over that of gasoline. Pronounced variations in unprocessed natural gas composition can however present an emissions problem for engines used in natural gas recovery where unrefined wellhead gas is used as the fuel. This study is twofold involving both experimental analysis and theoretical development with a computer model that simulates wellhead gas combustion. On the experimental side, Fourier transform infrared spectroscopy (FTIR) was used to analyze emissions of a 2.4L four-cylinder spark-ignited natural gas engine operating on fuels of varying composition. A comparative assessment is made between CO, NO, THC, CH4, and CH2O emissions of the engine operating on refined pipeline natural gas and those of the engine operating on the same gas with added CO2, N2, and C3H8 diluents. Diluents were added to the fuel individually to isolate the effect of each and to approximate wellhead gas. Additionally, a burn rate analysis was conducted which shows changes in the rate of fuel energy liberation with changes in diluent concentration. On the theoretical side, a two zone computer model of engine operation was developed that would simulate operation of the engine under varying fuel composition as found in various natural gas recovery wells throughout the United States. Results show that exhaust concentrations of NO and THC were strongly affected by addition of both inert and reactive diluent due to their strong dependence on in-cylinder temperature. Emissions of CO, CH4, and CH2O were also found to depend on diluent concentration; however, to a much lesser extent with emissions of CO being seemingly unaffected by addition of N2 for the compositions tested. Burn rate analysis shows that the introduction of inert constituents to the fuel decreases the fuel burn rate while addition of propane increases the burn rate. The whole of the analysis indicates a strong dependence of emissions on fuel composition and that significant potential exists for emissions reduction of engines operating on unprocessed natural gas.
Spray Development and Wall Impingement of Ethanol and Gasoline in an Optical Direct Injection Spark Ignition Engine
Authors: Fatouraie Mohammad , Wooldridge Margaret S. , Petersen Benjamin R. , Wooldridge Steven T.
Published: January 2016

The effects of ethanol on spray development and wall impingement of a direct injection spark ignition (DISI) engine was investigated using high-speed imaging of the fuel spray in an optically-accessible engine. Neat anhydrous ethanol (E100), reference grade gasoline (E0) and a 50% blend (by volume) of gasoline and ethanol (E50) were used in the study. The experiments were conducted using continuous firing conditions for an intake manifold absolute pressure of 57 kPA, and engine speed of 1500 RPM. Retarded fuel injection timing was used (with start of injection at 250 °bTDC) to isolate the effects of cylinder wall impingement, and lean fuel-to-air ratios (ϕ=0.8–0.9) were used to minimize sooting and coating of the transparent cylinder liner. The effects of three engine coolant temperatures (25, 60 and 90 °C) and two fuel rail pressures (100 and 150 bar) on the features of the spray and the spray interaction with the wall were studied for the different fuels. Quantitative metrics were defined to analyze the spatial features of the spray related to wall impingement. Gasoline (E0) sprays exhibited higher sensitivity to coolant temperature compared to ethanol (E100) in terms of the shape of the spray and wall impingement. Higher fuel injection pressure increased the spray tip penetration rate and fuel impingement with the wall for E0 and E100, despite creating wider plume angles of the fuel sprays.
Application of Dynamic Φ-T Map: Analysis on a Natural Gas/Diesel Fueled RCCI Engine
Authors: Li Jing , Yang Wenming , An Hui , Zhou Dezhi , Kraft Markus
Published: January 2016

In this study, dynamic ϕ-T map analysis was applied to an RCCI (reactivity controlled compression ignition) engine fueled with NG (natural gas) and diesel. The combustion process of the engine was simulated by coupled KIVA4-CHEMKIN with a DOS (diesel oil surrogate) chemical mechanism. The ϕ-T maps were constructed by the mole fractions of soot and NO obtained from SENKIN and ϕ-T conditions from engine simulations. Five parameters, namely NG fraction, 1st SOI (start of injection) timing, 2nd SOI timing, 2nd injection duration and EGR (exhaust gas recirculation) rate were varied in certain ranges individually, and the ϕ-T maps were compared and analyzed under various conditions. The results revealed how the five parameters would shift the ϕ-T conditions and influence the soot-NO contour. Among the factors, EGR rate could limit the highest temperature due to its dilute effect, hence maintaining RCCI combustion within LTC (low temperature combustion) region. The second significant parameter is the premixed NG fraction. It could set the lowest temperature; moreover, the tendency of soot formation can be mitigated due to the lessened fuel impingement and the absence of C-C bond. Finally, the region of RCCI combustion was added to the commonly known ϕ-T map diagram.
Fuel Injection Quantity Fluctuation Prediction of Common Rail System Based on Bond Graph Model
Authors: Bai Yun , Fan Liyun , Dong Xiaolu , Ma Xiuzhen , Song Enzhe
Published: January 2016

Common rail injection system (CRIS) is an advanced technology which meets the stringent emission standards of diesel engines and satisfies consumer demand for better fuel efficiency and increased power. The coherence of fuel injection quantity is the key injection characteristic for CRIS to match diesel engines successfully. As a critical component for CRIS, the variation of injector characteristic parameters has significant influence on the coherence of fuel injection quantity of the system. In this paper, combining numerical modeling and design of experiments, the response predicted relation between fuel injection quantity fluctuation of CRIS and its influence factors had been investigated. A numerical model of common rail injector was presented for the purpose of creating a tool for simulation experiments. The model is developed using power bond graph method, which is a modeling method that has shown its superiority in modeling systems consisting of sub-models from several energy domains in a unified approach. Experiments were conducted at the same model conditions to validate the model. The results are quite encouraging and in agreement with model predictions, which imply that the model can accurately predict the fuel injection quantity of CRIS and it can be used to simulation and design experiments. Experiments were designed using D-optimal method in which the characteristic parameters of common rail injector were chosen as design factors and the fuel injection quantity fluctuation was selected as the response. The fuel injection quantity fluctuation responses at different design factor levels were obtained using the developed numerical model which had been validated. A regressive prediction model of fuel injection quantity fluctuation was suggested according to the simulation experiments by means of partial least-squares regression (PLR) analysis. Analysis of variance, normal distribution of standardized residuals and relation between observed and predicted fuel injection quantity fluctuation for the regressive prediction model were analyzed which demonstrate the favorable goodness of fit and significance of the regressive model to predict fuel injection quantity fluctuation of the system. By changing design factor levels, the comparisons between numerical results of the bond graph model and the predicted fuel injection quantity fluctuation of the regressive prediction model were conducted. Results show that the regressive prediction model can reliably predict the fuel injection quantity fluctuation caused by the variation of characteristic parameters of common rail injector. Research results of this paper can provide novel ideas to predict fuel injection quantity fluctuation and a theoretical guidance for design and parameters optimization of CRIS.
Friction Reduction Opportunities in Combustion Engine Crank Train Bearings
Authors: Aufischer Rainer , Walker Rick , Offenbecher Martin , Feng Oliver , Hager Gunther
Published: January 2016

The development of combustion engines is heavily influenced by environmental regulations and efficiency. Since the environmental regulation have influenced engine design already with special combustion system and exhaust gas treatments, efficiency and the greenhouse gas CO2 has become a major issue for further development.

CO2 emissions and fuel efficiency are linked and are directly influenced by the internal friction of the combustion engine. One major part of this internal friction is coming from the crank train bearings. Since we have to consider different operating conditions for the crank train bearings like hydrodynamic and mixed friction (hydrodynamic in combination with boundary contact), working principles as well as different engine operating conditions like full load, idle, start stop etc. different measures need to be employed for a friction reduced crank train.

The optimal dimensioning of the bearings in combination with oil viscosity reduction are already known to a certain extent. Nevertheless they result in changes of bearing loads and may in consequence increase the share of boundary friction. Therefore, only looking on these two optimization steps is not enough. In addition the friction coefficient between bearing and shaft as well as the interaction between bearing surface and lubricant need to be addressed to reduce friction loss.

In order to gain a complete picture, influences and the interaction of

• geometric properties and bearing dimensions,

• friction coefficient of bearings in combination with crankshaft materials,

• oil formulation, viscosity and their interaction with engine application and duty cycle as well as

• losses caused by the lubrication system design and components

are investigated and analyzed based on simulation and testing. At first the different steps are investigated individually and secondly combinations and interactions are derived on basis of parameters derived on tribological tests and material data. Oil viscosity as major driver during hydrodynamic operation but also the influence of additive packages during mixed friction is roughly estimated on basis of tribological investigations.

Since the overall friction system and its optimization are very complex, an example for a truck engine in different applications shows advantages and disadvantages of the different approaches. Also border lines given by operational risk and improvement limits are explained. The improvement options given by bearing materials and special coatings are explained in combination with different engines and engine applications.

Further development activities, ways of collaboration between engine manufacturer and bearing supplier and an outlook on up-coming bearing system are completing the picture for a holistic approach on friction reduction in crank train bearings.
Dilution Sensitivity of Particulate Matter Emissions From Reactivity Controlled Compression Ignition Combustion
Authors: Fang Wei , Kittelson David B. , Northrop William F.
Published: January 2016

Dual-fuel reactivity-controlled compression ignition (RCCI) combustion can yield high thermal efficiency and simultaneously low NOx and soot emissions. Although soot emissions from RCCI is very low, hydrocarbon emissions are high, potentially resulting in higher than desired total particulate matter (PM) mass and number caused by semi-volatile species converting the particle phase upon primary dilution in the exhaust plume. Such high organic fraction PM is known to be highly sensitive to the dilution conditions used when collecting samples on a filter or when measuring particle number using particle sizing instruments. In this study, PM emissions from a modified single-cylinder diesel engine operating in RCCI and conventional diesel combustion modes were investigated under different dilution conditions. To investigate the effect of the fumigated fuel on the PM emissions, 150 proof hydrous ethanol and gasoline were used as low reactivity fuels to study the relative contribution of fumigant versus directly injected fuel on the PM emissions. Our study found that PM from RCCI combustion is more sensitive to the variation of dilution conditions than PM from single fuel conventional diesel combustion. RCCI PM primarily consisted of semi-volatile organic compounds and a smaller amount of solid carbonaceous particles. The fumigated fuel had a significant effect on the PM emissions characteristics for RCCI combustion. Hydrous ethanol fueled RCCI PM contained a larger fraction of volatile materials and were more sensitive to the variation of dilution conditions compared to the gasoline fueled RCCI mode.
Computational Studies of Glow Plug Ignition of Injected High Pressure Gas Jets
Authors: Pan Kang , Wallace James S.
Published: January 2016

A numerical study of ignition and combustion in a glow plug (GP) assisted direct-injection natural gas (DING) engine is presented in this paper. The glow plug is shielded and the shield design is an important part of the combustion system development. The results simulated by KIVA-3V indicated that the ignition delay (ID) predicted by an in-cylinder pressure rise was different from that based on a temperature rise, attributed to the additional time required to burn more fuel to obtain a detectable pressure rise in the combustion chamber. This time difference for the ignition delay estimation can be 0.5 ms, which is significant relative to an ignition delay value of less than 2 ms. To further evaluate the time difference between the two different methods of ignition delay determination, sensitivity studies were conducted by changing the glow plug temperature, and rotating the glow plug shield opening angle towards the fuel jets. The results indicated that the ID method time difference varied from 0.3 to 0.8 ms for different combustion chamber configurations. In addition, this study also investigated the influences of different glow plug shield parameters on the natural gas ignition and combustion characteristics, by modifying the air gap between the glow plug and its shield, and by changing the shield opening size. The computational results indicated that a bigger air gap inside the shield can delay gas ignition, and a smaller shield opening can block the flame propagation for some specific fuel injection angles.
Development of a Methodology for Engine Performance Investigation Through Double Crankshaft Speed Measurement
Authors: Ponti F. , Ravaglioli V. , De Cesare M.
Published: January 2016

Optimal combustion control has become a key factor in modern automotive applications to guarantee low engine out emissions and good driveability. In order to meet these goals, the engine management system has to guarantee an accurate control of torque delivered by the engine and optimal combustion phasing.

Both quantities can be calculated through a proper processing of in-cylinder pressure signal. However, in-cylinder pressure on-board installation is still uncommon, mainly due to problems related to pressure sensors’ reliability and cost. Consequently, over the last years, the increasing request for combustion control optimization spawned a great amount of research in the development of remote combustion sensing methodologies, i.e. algorithms that allow extracting useful information about combustion effectiveness via low cost sensors, such as crankshaft speed, accelerometers or microphones.

Based on the simultaneous acquisition of two crankshaft speed signals, this paper analyses the information that can be extracted about crankshaft’s torsional behavior through a proper processing of the acquired signals. In particular, the correlations existing between such information and indicated quantities (torque delivered by the engine and combustion phasing) have been analysed. In order to maximize the signal-to-noise ratio, each speed measurement has been performed at an end of the crankshaft, i.e. in correspondence of the flywheel and the distribution wheel. The presented approach has been applied to a light-duty L4 Diesel engine mounted in a test cell. Nevertheless, the methodology is general, and it can be applied to engines with a different number of cylinders, both CI and SI.
A Numerical Simulation of Analysis of Backfiring Phenomena in a Hydrogen Fuelled Spark Ignition Engine
Authors: Subramanian K. A. , Salvi B. L.
Published: January 2016

Hydrogen utilization in spark ignition engines could reduce urban pollution including particulate matter as well as greenhouse gas (carbon dioxide) emission. However, backfiring, which is an undesirable combustion process of intake charge in hydrogen fuelled spark ignition (SI) engine with manifold based injection, is one of the major technical issues in view of safety as well as continuous engine operation as ignition process could proceed instantaneously due to less ignition energy requirement of hydrogen. Backfiring occurs generally during suction stroke as the hydrogen-air charge interacts with residual gas resulting in flame growth and propagation towards upstream of engine’s intake manifold resulting in stalling of engine operation and high risk of safety. This work is aimed at analysis of backfiring in a hydrogen fuelled SI engine. The results indicate that backfiring is mainly function of residual gas temperature, start of hydrogen injection timing and equivalence ratio. Any hot-spot present in the cylinder would act as ignition source resulting in more chances of backfiring. In addition to this, CFD analysis was carried out in order to assess flow characteristics of hydrogen and air during suction stroke in intake manifold. Furthermore, numerical analysis of intake charge velocity, flame speed (deflagration), and flame propagation (backfiring) towards upstream of intake manifold was also carried out. Some notable points of backfiring control strategy including exhaust gas recirculation (EGR) and retarded (late) hydrogen injection timing are emerged from this study for minimizing chance of backfiring. This study results are useful for development of dedicated spark ignition engine for hydrogen fuel in the aspects of elimination of backfiring.
Exhaust Conditioning Technology to Prevent Sulfur Poisoning on Methane Oxidation Catalyst
Authors: Goenawan Isna Y. , Hu Linjie (Robin) , Williams Shazam
Published: January 2016

In some regions of the world, emissions of total organic carbon (TOC), including methane and non-methane hydrocarbons (NMHCs), from the tail pipe of natural gas or biogas fuelled combustion equipments are strictly regulated (e.g. 150 mg/Nm3 of exhaust gas in Italy). Post combustor has been widely chosen in response to the TOC emission targets. TOC typically consists of >90% methane — a strong greenhouse gas and the most challenging compound to remove due to its highly stable form. Thus, more gas is being consumed to burn the TOC present in the exhaust, resulting in higher operating (or power production) costs.

A passive catalytic approach is an alternative to post combustor. Palladium based oxidation catalyst is known to actively remove TOC, providing no sulfur compounds present. Sulfur poisons and deactivates the catalyst in a short time. This paper presents a concept to extend the life of the oxidation catalyst by using an exhaust post conditioning system. The system is designed to eliminate and withstand contaminants, yielding a protection to the catalyst. Consequently, the catalyst life is prolonged by about 50 times.
Modeling Auto-Ignition Transients in Reacting Diesel Jets
Authors: Hakim Layal , Lacaze Guilhem , Khalil Mohammad , Najm Habib N. , Oefelein Joseph C.
Published: January 2016

The objective of the present work is to establish a framework to design simple Arrhenius mechanisms for simulation of Diesel engine combustion. The goal is to predict auto-ignition and flame propagation over a selected range of temperature and equivalence ratio, at a significantly reduced computational cost, and to quantify the accuracy of the optimized mechanisms for a selected set of characteristics. The methodology is demonstrated for n-dodecane oxidation by fitting the auto-ignition delay time predicted by a detailed reference mechanism to a two-step model mechanism. The pre-exponential factor and activation energy of the first reaction are modeled as functions of equivalence ratio and temperature and calibrated using Bayesian inference. This provides both the optimal parameter values and the related uncertainties over a defined envelope of temperatures, pressures, and equivalence ratios. Non-intrusive spectral projection is then used to propagate the uncertainty through homogeneous auto-ignitions. A benefit of the method is that parametric uncertainties can be propagated in the same way through coupled reacting flow calculations using techniques such as Large Eddy Simulation to quantify the impact of the chemical parameter uncertainty on simulation results.
Simulation of Mechanical Hydraulic System Dynamics Using Coupled Specialized Fluid Models and Multibody Dynamics
Authors: Lynch Bradford
Published: January 2016

Durability is a prime concern in the design of hydraulic systems and fuel injectors [1–3] thus an accurate prediction of impact velocities between components and the flow through them is essential to assessing concepts. Simulation of these systems is difficult because the geometries are complex, some volumes go to zero as the components move, and the flow at a single operating condition generally spans Reynolds numbers less than 1 to more than 104[4–8]. As a result of these challenges, experimental testing of prototypes is the dominant method for comparing concepts. This approach can be effective but is far more costly, time consuming, and less flexible than the ability to run simulations of concepts early in the design cycle.

A validated model of a fuel injector built from publicly available data [1] is used to present a new approach to modelling hydraulic systems which overcomes many of these obstacles. This is accomplished by integrating several commercially available tools to solve the physics specific to each area within the fuel injector. First, the fuel injector is simulated using a 3D CFD simulation integrated with a 1D CFD system model. The flow in various regions of the injector is then analyzed to determine if the fluid models in these areas can be simplified based on the flow regime. Based on this analysis, a combination of models is assembled to improve the quality of the simulation while decreasing the time required to run the model.

The fuel injector is simulated using a multibody dynamics model coupled to a reluctance network model of the solenoid and several fluid models. The first is a 3D CFD simulation which uses novel mesh refinement techniques during runtime to ensure high mesh quality throughout the motion of components, to resolve the velocity profile of laminar flows, and to satisfy the requirements of the RNG k-ε turbulence model and wall functions. This approach frees the analyst from defining the mesh before runtime and instead allows the mesh to adapt based on the flow conditions in the simulation. Due to the highly efficient meshing algorithm employed, it is possible to re-mesh at each timestep thus ensuring a high quality structured mesh throughout the simulation duration. Then a 3D FEM solution to the Reynolds Equation and a statistical contact model is employed to solve for the squeeze films between components and to allow separation and contact between bodies in the control valve. These detailed simulations are integrated with a 1D flow model of the fuel injection system.

The results from the detailed coupled simulations are compared to the results from simpler 1D models and measured data to illustrate under which operating conditions a more advanced technique incorporating 3D CFD is worth the additional computational expense versus a traditional 1D model.
Comparison of Diesel Pilot Ignition (DPI) and Reactivity Controlled Compression Ignition (RCCI) in a Heavy-Duty Engine
Authors: Walker N. Ryan , Chuahy Flavio D. F. , Reitz Rolf D.
Published: January 2016

Due to growing interest in utilizing natural gas as an alternative fuel in internal combustion engines, a study on the use of natural gas for dual-fuel combustion strategies in a heavy-duty engine was performed to examine the diesel pilot ignition (DPI) and reactivity controlled compression ignition (RCCI) combustion strategies. In Part 1 of this work, the transition between the DPI and RCCI combustion regimes was studied via the direct control of the SOI timing. At the relatively rich condition of ϕ = 0.72, the performance of both combustion strategies was comparable. In Part 2 of this work, the effect of the equivalence ratio on each combustion regime was examined. It was observed that at richer conditions the performance of each combustion regime was similar. However as the conditions became leaner, the performance improved for RCCI combustion and was degraded for DPI combustion. In Part 3 of this work, the effect of fueling rate was explored at a relatively lean operating condition (ϕ = 0.52). It was seen that the fueling rate has little effect on the combustion performance as the engine load was increased. The strong influence of the equivalence ratio on the combustion performance of the RCCI and DPI combustion strategies indicates the both combustion regimes are recommended to engine applications with air handling systems which generate relatively rich in-cylinder conditions; for engine applications with air handling systems which allow for relatively lean in-cylinder conditions, the RCCI combustion regime is recommended.
A Biogas-Tolerant Engine-Generator for Advanced Agricultural Waste Management
Authors: Yelvington Paul E. , Gattoni John M. , Merical Kyle I. , Carpenter Andrew L.
Published: January 2016

Anaerobic digesters are capable of producing methane-rich biogas from animal manure and also offer the advantages of controlling odors, reducing pathogens, and minimizing the environmental impact of the waste. Unfortunately, biogas is contaminated with hydrogen sulfide (H2S), a highly corrosive gas that is not compatible with many stock engine component materials. As a result, conventional engines can fail after several months of exposure to raw biogas. No small or medium piston engine-generators (<100 kWe) are currently available that can use this fuel without pretreatment to remove the H2S — a process that adds complexity, cost, consumables, and maintenance. As a result, many smaller digester installations simply flare the biogas rather than extracting any useful work from the fuel.

Mainstream Engineering is developing a biogas-tolerant engine-generator (BTEG) that can use raw biogas without pretreatment to remove H2S. The development program involved a combination of approaches — materials replacement, coatings, engine control strategy changes, lubrication system changes, and additional sensors. A prototype 25 kW BTEG has been developed using a Ford DSG 2.3 L natural gas engine as the demonstration platform. In this paper, we report on performance testing of the baseline unmodified engine-generator and the BTEG. Measurements of fuel consumption, exhaust temperature, in-cylinder pressure, and exhaust gaseous emissions were made using several synthetic biogas mixtures (60–80% CH4/balance CO2) and pure methane. Because the methane fraction in biogas can change with digester conditions and weather — a method of estimating the biogas composition on the fly and adjusting the spark timing to compensate for the variability has been demonstrated. We also report on limited (100 hr) durability testing of the modified engine using fuel containing 3,000 ppmv of H2S. During this test, the oil was analyzed to track acidification of the engine oil and monitor the accumulation of sulfur or any wear metals.
Diesel Particulate Filter-Related Fuel Efficiency Improvements Using Biodiesel Blends in Conjunction With Advanced Aftertreatment Sensing and Controls
Authors: Sappok Alexander , Ragaller Paul , Bromberg Leslie , Prikhodko Vitaly , Storey John , Parks James
Published: January 2016

It is well known that biodiesel may reduce engine-out particulate matter (PM) emissions and result in PM which has more favorable oxidation characteristics relative to PM derived solely from petroleum diesel. This study investigated the use of neat biodiesel, as well as blends, with a light-duty diesel engine equipped with a catalyzed diesel particulate filter (DPF) and radio frequency particulate filter sensor. The results show a reduction in engine-out PM emissions with increasing biodiesel blend levels and a corresponding increase in the duration between DPF regenerations. In situ measurements of the PM oxidation rates on the DPF using the radio frequency sensor further indicated more rapid oxidation of the biodiesel-derived PM with lower light-off temperatures relative to the petroleum-derived PM. The conclusions indicate considerable potential to extend DPF regeneration intervals and decrease regeneration duration when biodiesel blends are used in conjunction with advanced DPF sensing and control systems, thereby reducing the DPF-related fuel consumption.
Diesel-Like Efficiency Using CNG/Diesel Dual-Fuel Combustion
Authors: Nithyanandan Karthik , Zhang Jiaxiang , Li Yuqiang , Meng Xiangyu , Donahue Robert , Lee Chia-Fon F. , Dou Huili
Published: January 2016

The use of natural gas in compression ignition engines as a supplement to diesel under dual-fuel combustion mode is a promising technique to increase efficiency and reduce emissions. In this study, the effect of dual-fuel operating mode on combustion characteristics, engine performance and pollutant emissions of a diesel engine using natural gas as primary fuel and neat diesel as pilot fuel, has been examined. Natural Gas (99% Methane) was port injected into an AVL 5402 single cylinder diesel research engine under various engine operating conditions and up to 90% substitution was achieved. In addition, neat diesel was also tested as a baseline for comparison. The experiments were conducted at three different speeds — 1200, 1500 and 2000 RPM, and at different diesel-equivalent loads (injection quantity) — 15, 20, and 25 mg/cycle. Both performance and emissions data are presented and discussed. The performance was evaluated through measurements of in-cylinder pressure, power output and various exhaust emissions including unburned hydrocarbons (UHC), carbon monoxide (CO), nitrogen oxides (NOx) and soot. The goal of these experiments was to maximize the efficiency. This was done as follows — the CNG substitution rate (based on energy) was increased from 30% to 90% at fixed engine conditions, to identify the optimum CNG substitution rate. Then using that rate, a main injection timing sweep was performed. Under these optimized conditions, combustion behavior was also compared between single, double and triple injections. Finally, a load and speed sweep at the optimum CNG rate and timings were performed. It was found that a 70 % CNG substitution provided the highest indicated thermal efficiency. It appears that dual-fuel combustion has a Maximum Brake Torque (MBT) diesel injection timing for different conditions which provides the highest torque. Based on multiple diesel injection tests, it was found that the conditions that favor pure diesel combustion, also favor dual-fuel combustion because better diesel combustion provides better ignition and combustion for the CNG-air mixture. For 70% CNG dual-fuel combustion, multiple diesel injection showed an increase in the efficiency. Based on the experiments conducted, diesel-CNG dual-fuel combustion is able to achieve similar efficiency and reduced emissions relative to pure diesel combustion. As such, CNG can be effectively used to substitute for diesel fuel in CI engines.
Effect of Ambient Temperature and Humidity on Combustion and Emissions of a Spark Assisted Compression Ignition Engine
Authors: Chang Yan , Mendrea Brandon , Sterniak Jeff , Bohac Stanislav V.
Published: January 2016

Spark Assisted Compression Ignition (SACI) offers more practical combustion phasing control and a softer pressure rise rate than Homogeneous Charge Compression Ignition (HCCI) combustion, and improved thermal efficiency and lower NOx emissions than Spark Ignition (SI) combustion. Any practical engine, including one that uses SACI in part of its operating range, must be robust to changes in ambient conditions.

This study investigates the effects of ambient temperature and humidity on stoichiometric SACI engine performance, combustion and emissions. It is shown that at the medium speed and load SACI test point selected for this study, increasing ambient air temperature from 20°C to 41°C advances combustion phasing, increases maximum pressure rise rate, causes a larger fraction of the charge to be consumed by auto-ignition (and a smaller fraction by flame propagation), increases NOx, and increases Brake Specific Fuel Consumption (BSFC). Increasing ambient humidity from 32% to 60% retards combustion phasing, reduces maximum pressure rise rate, causes a larger fraction of the charge to be consumed by auto-ignition and a smaller fraction by flame propagation, increases Coefficient of Variation of IMEP (COV) of IMEP, reduces NOx, and increases BSFC. These results show that successful implementation of SACI combustion in real-world driving requires a control strategy that compensates for changes in ambient temperature and humidity.
Different Diesel Engine Ignition Regimes With a Single Injection
Authors: Wang Mianzhi , Xu Zhengxin , Zhang Saifei , Lee Chia-fon F.
Published: January 2016

A simple single injection scheme is used to understand the fundamental processes of diesel engine ignition. Two different combustion regimes, partially premixed combustion (PPC), and conventional direct injection compression ignition (DICI), are computationally achieved with the single injection scheme in a 3-D CFD program. An ignition phase curve covering the two combustion regimes is proposed and verified by numerical simulation. The ignition phase curve is used to reveal the underlying physics of each regime. It is found that the interaction among piston motion, chemical kinetics, fuel-air mixing, and injection event differs the two combustion regimes. The conventional DICI mode ignition is dominated by injection timing and affected by the mixture pressure and temperature during the flame induction period. In the PPC mode, the over-mixing effect of the fuel affects largely the ignition process. The variations of the moment of cool flame onset and high temperature ignition are discussed in detail. The differences between the proposed and calculated ignition phase curve are due to the specific piston and injector design of the test engine for which calculations are done. Finally, the effects of intake temperature on the ignition phase curve are explained based on numerical results.
NVH of RCCI With DI ULSD and PFI With 50% N-Butanol
Authors: Soloiu Valentin , Simons Emerald , Muinos Martin , Harp Spencer
Published: January 2016

The noise of diesel engines is dependent upon numerous factors such as: load, speed, fuel injection strategies and fuel type, design of the piston, piston-pin and cylinder and their tolerances, bearings, valves and rocker arm clearances, and designs of the manifolds.

In this study, engine sound and vibrations analysis have been conducted using two types of fueling and combustion strategies: classical ULSD combustion and the new RCCI with n-butanol injected in the intake manifold. The analyses add to the understanding of the influence of combustion characteristics’ effect on mechanical noise and vibrations throughout the engine’s operating cycle.

The sound and vibration signals were both analyzed in the frequency and angle domain spectrum. Overall NVH spectrum from ULSD combustion was compared to that of RCCI with 50% by mass PFI of n-butanol (the 50% remaining ULSD fuel was directly injected).

Frequency analyses were performed using the FFT and CPB methods with Bruel & Kjaer’s Pulse sound and vibrations analysis software. Angle domain analyses were performed, referencing 0 CAD as TDC in combustion.

The engine tests were conducted at 1500 rpm and 4 bar IMEP. The COV of IMEP for DI ULSD and RCCI were 2.4 and 2.2, respectively. The correlations between sound, three dimensional vibration levels, and timings were found for: pressure gradients from combustion process, intake and exhaust valve actuations and gas exchange, and piston slap on the cylinder liner.

The measurements were extracted and analyzed, and the results determined that virtually all the noise and vibration values pertinent to RCCI were lower than those of ULSD classical combustion.
Zero Dimensional Quasi-Predictive Thermodynamic Simulation for Establishing Initial Cylinder Conditions for CFD Simulation of Diesel Combustion
Authors: Bandura Ryan A. , Jacobs Timothy J.
Published: January 2016

Computational fluid dynamics (CFD) is now a ubiquitous computational tool for engine design and diagnosis. It is often necessary to provide well-known initial cycle conditions to commence the CFD computations. Such initial conditions can be provided by experimental data. To create an opportunity to computationally study engine conditions where experimental data are not available, a zero-dimensional quasi-predictive thermodynamic simulation is developed that uses well-established spray model to predict rate of heat release and calculated burned gas composition and temperature to predict nitric oxide (NO) concentration. This simulation could in turn be used in reverse to solve for initial cylinder conditions for a targeted NO concentration. This paper details the thermodynamic simulation for diesel engine operating conditions. The goal is to produce a code that is capable of predicting NO emissions as well as performance characteristics such as mean effective pressure (MEP) and brake specific fuel consumption (BSFC). The simulation uses general conservation of mass and energy approaches to model intake, compression, and exhaust. Rate of heat release prediction is based on an existing spray model to predict how fuel concentrations within the spray jet change with penetration. Rate of heat release provides predicted cylinder pressure, which is then validated against experimental pressure data under known operating conditions. An equilibrium mechanism is used to determine burned gas composition which, along with burned gas temperature, can be used for prediction of NO in the cylinder. NO is predicted using the extended Zeldovich mechanism. This mechanism is highly sensitive to temperature, and it is therefore important to accurately predict cylinder gas temperature to obtain correct NO values. Additionally, MEP and BSFC are determined. The simulation focuses on single fuel injection events, but insights are provided to expand the simulation to model multiple injection events.
Numerical Comparison of an Electric Turbo Compound Applied to a SI and a CI Engine
Authors: Pasini Gianluca , Frigo Stefano , Marelli Silvia
Published: January 2016

In a medium term scenario Internal Combustion Engine (ICE) downsizing and hybrid powertrain will represent the actual trend in vehicle technology to reduce fuel consumption and CO2 emission. Concerning downsizing concept, to maintain a reasonable power level in small engines, the application of turbocharging is mandatory both for spark ignition (SI) and compression ignition (CI) engines. Following this aspect, the possibility to couple an electric machine to the turbocharger (electric turbo compound, ETC) to recover the residual energy of the exhaust gases is becoming more and more attractive, as demonstrated by several studies around the world and by the current application in the F1 Championship.

The present paper shows the first numerical results of a research program focused on the comparison of the benefits resulting from the application of an ETC to a small twin-cylinder SI engine (900 cm3) and to a four cylinders CI engine (1600 cm3), both of the same maximum power. Starting from the experimental maps of several turbines and compressors, complete model of both turbocharged engines were created using the AVL BOOST one-dimension code.

Concerning the SI engine, first numerical results show that ETC can improve the average overall efficiency at the highest engine speeds and loads. Besides, boost range extension in the lowest engine rotational speed region and a possible reduction of turbo lag represent other benefits related to ETC application.

On the other hand, the adoption of an ETC to a CI engine shows larger benefits in term energy recovery at the highest engine speeds, with consequent reduction of fuel consumption, mainly due to the absence of throttling effects in the intake manifold and related pumping losses.
Modeling of Sintered Metal Fiber Diesel Particulate Filter Wall Permeability Based on 3D Digital Structure From CT-Scan
Authors: Wang Yujun , Folino Paul , Singh Rakesh K. , Kamp Carl J. , Saeid Amin , Ernstmeyer James , Kharraja Bachir
Published: January 2016

Sintered metal fiber (SMF) diesel particulate filters (DPF) systems efficiently remove particulate matter (PM) emission from diesel engine exhaust with low flow resistance. The permeability of DPF filtration media is the key property determining DPF fuel penalty to the engine. To advance the understanding and optimization of SMF filtration media, a general model to compute SMF media permeability based on 3D digital structure from computed tomography scan (CT-Scan) is developed in this study. An open source computational fluid dynamics (CFD) tool, OpenFOAM, is used to calculate the SMF porous media permeability. The media samples computation domain is approximately 0.9mmx0.9mmx1.8mm (depth) and one hour is needed for each simulation with 8–9 million mesh cells. The study reveals variations of permeability among different SMF media samples. The computed permeability from the 3D simulation has a good agreement with experiment data and achieves a much better accuracy than previous analytical models. In addition, through this study, a significant amount of in-depth information of flow field across the porous media is obtained, which is beneficial to improve the understanding of DPF fibrous media and builds the foundation for more advanced filtration model development.
Pipeline Vulnerability to Natural Hazards
Authors: Amórtegui José Vicente
Published: January 2016

The strength and stiffness of the pipelines allow them to tolerate the effects of natural hazards for some period of time. The amount of time depends on the strength and deformability, the stress state, the age, the conditions of installation and operation of the pipeline and their geometric arrangement with regard to the hazardous process.

Accordingly, some of the hazards due to weather conditions and external forces would not be time independent. In consequence the designing of monitoring systems to predict the behavior of the pipelines against natural hazards is required in order to carry out the preventive actions which are necessary to avoid failure of the pipes due to the exposition to those hazards.

In this paper a method for assessing the transport system vulnerability is developed, a function for risk analysis is proposed (which is determined by the probability of the natural hazard, the pipeline’s vulnerability to the hazard and the consequences of the pipe rupture). The elements that are part of that evaluation are presented and illustrated by means of examples.