bluuebunny/crossref_metadata_2025 huggingface dataset:
A Robust Design Optimization Framework for Systematic Model-Based Calibration of Engine Control System
Authors: Borhan Hoseinali , Hodzen Edmund
Published: December 2014

In this paper, a systematic model-based calibration framework basing on robust design optimization technique is developed for engine control system. In this framework, the control system is calibrated in an optimization fashion where both performance and robustness of the closed-loop system to uncertainties are optimized. The proposed calibration process has three steps; in the first step, the optimal performance of the system at the nominal conditions where the effects of uncertainties are ignored is computed by formulation of the controller calibration as an optimization problem. The capabilities of the controller are fully explored at nominal conditions. In the second step, the robustness and sensitivity of a selected control design to the system uncertainties is analyzed using Monte Carlo simulation. In the third step, robust design optimization is applied to optimize both performance and robustness of the closed-loop system to the uncertainties. The robustness capabilities of the controller are fully explored and the one that satisfies both performance and robustness requirements is selected. This process is implemented for the calibration of an advanced Diesel air path control system with a Variable Geometry Turbocharge (VGT) and dual loop EGR architecture.
Investigating Fuel Condensation Processes in Low Temperature Combustion Engines
Authors: Qiu Lu , Reitz Rolf D.
Published: December 2014

Condensation of gaseous fuel is investigated in a low temperature combustion engine fueled with double direct-injected diesel and premixed gasoline at two load conditions. Possible condensation is examined by considering real gas effects with the Peng-Robinson equation of state and assuming thermodynamic equilibrium of the two fuels. The simulations show that three representative condensation events are observed. The first two condensations are found in the spray some time after the two direct injections, when the evaporative cooling reduces the local temperature until phase separation occurs. The third condensation event occurs during the late stages of the expansion stroke, during which the continuous expansion sends the local fluid into the two-phase region again. Condensation was not found to greatly affect global parameters, such as the average cylinder pressure and temperature mainly because, before the main combustion event, the condensed phase was converted back to the vapor phase due to compression and/or first stage heat release. However, condensed fuel is shown to affect the emission predictions, including engine-out particulate matter and unburned hydrocarbons.
Study of New Exhaust Ejector for Marine Gas Turbine
Authors: Sun Tao , Yuan Minghui , Xu Yuehan , Wang Guohui , Ye Nan
Published: December 2014

With the development at infrared guidance weapon, the survival of the ship, especially in high risk areas, is facing serious challenges. In order to improve its survival ability, infrared suppression system emerges. Marine gas turbine exhaust ejector system is its core component, which is responsible for reducing or even eliminating the infrared radiation signal of marine gas turbine exhaust system. Based on collecting data on many sorts of ejectors, we sort out literature related to gas turbine exhaust ejector. From the view of ejector structure, the paper briefly describes the development of gas turbine exhaust ejector used on ships in domestic and foreign. Put forward two major structural innovations: the structure of nozzle changes from circular to rectangular and diffuser adopts multilevel structure. A new type of marine gas turbine exhaust ejector was designed. Ejector model is simplified. Use numerical simulation method to predict the single stage ejector and multi-stage ejectors. Further structural optimization plan and design can be made based on this essay.
Application of Model Reduction Techniques Within Cummins Inc.
Authors: Tahilramani Dhaneesh R. , Hitchins Juliet
Published: December 2014

For the past decade Cummins Inc. have increased the use of standard Finite Element Analysis (FEA) techniques to drive the design of its products. However, as FEA models are not scalable to the limits of hardware, running traditional FEA, especially on large High Horse Power (HHP) engine structures’ assemblies, both reliably and within a reasonable time frame was found to be not possible. This led to carrying out numerous analyses with fewer parts and assumed boundary conditions. This strategy ignores effects due to system vibration of the assembly. To reduce the risk of failures on complex assemblies, high speed engines required a more accurate analytical prediction of modal stresses on a system level. To increase the capacity of running system level analyses, a structured approach was followed and the Model Reduction Techniques Functional Excellence mini team was set up to develop methods and train analysts.

The team have been using Six Sigma tools [1] to carry out voice of the customer interviews in order to define the analytical requirements for running models for large complex structures (>20 million degree of freedom). This consists of brainstorming concepts to select solutions based on advanced analytical Substructuring techniques to best fit requirements. The benefits of the new process include a significant reduction in solve time, the ability to carry out system analysis, to follow an efficient working practice using a modular approach, to allow parallel processing globally and secure intellectual property rights when working with suppliers and customers of the Cummins Inc. products.

This paper shares experience on applying model reduction techniques following a structured approach and highlights computing and training resources for an analysis team.
Combustion System Strategy to Meet Tier4 Final Emission Regulations in a Locomotive Application for a Large Bore High Speed Diesel Engine
Authors: Mahato Chandan , Mahadevan Boopathi Singalandapuram , Hoehne John L. , Ravindran Arun C.
Published: December 2014

The combustion system of a large bore four stroke diesel engine was developed using the Analysis Led Design (ALD) process. A combustion strategy of particulate matter (PM) control in-cylinder and oxides of nitrogen (NOx) controlled through urea based selective catalytic reduction (SCR) of the engine exhaust, was adopted. Combustion analysis tools and single cylinder engine (SCE) tests were used to determine key combustion parameters like in-cylinder swirl, fuel injector configuration and, combustion chamber design to meet the EPA Tier4 final emission regulations at the different notch settings of the locomotive test cycle. Experimental validation of the ALD recommended hardware was accomplished on the SCE and the best combination was selected. Engine out PM and NOx target compliance was demonstrated on the multi cylinder diesel engine (MCE) over the composite locomotive notch cycle. Selective fuel Injector strategy was applied to control excessive unburned hydrocarbons (UHC) at low load engine operating conditions within the locomotive notch cycle.
Intake Air Humidity Consideration for DEF Tank Sizing for Tier 4 Emission Compliance Engines
Authors: Norris Colin , Hoehne John L. , Mahadevan Boopathi Singalandapuram
Published: December 2014

The Environment Protection Agency (EPA) Tier 4 emission standard requires locomotive engines to meet emission compliance at any ambient humidity for an ambient temperature of 60 to 105 F and an altitude level of up to 7000 ft. The engine tests were run at a range of intake air humidity and temperature to determine oxides of Nitrogen (NOx) emissions sensitivity to humidity, intake air temp for large bore diesel engines and compared with humidity correction factor recommended by EPA. Further, the change in NOx concentration altered conversion efficiency of the Selective Catalytic Reduction (SCR) catalyst. Hence, the change in Ammonia to NOx ratio and amount of DEF fluid required to achieve target NOx emissions reduction were studied. Considering this effect, the doser and DEF tank sizing strategy was defined based on in-use ambient humidity, temperature and altitude test conditions in order to mitigate risk of running out of DEF fluid during in-use operation of locomotives.
Advanced Numerical Approach to Simulate GDI Sprays Under Engine-Like Conditions
Authors: Ishii Eiji , Abe Motoyuki , Ehara Hideharu , Yasukawa Yoshihito
Published: December 2014

Gasoline direct-injection (GDI) engines provide both higher engine power and better fuel efficiency than port-injection gasoline engines. However, they emit more particulate matter (PM) than the latter engines. Fuel stuck on walls of pistons and combustion chambers forms a high-density region of fuel in the air/fuel mixture, which becomes a source of PM. To decrease the amount of PM, fuel injectors with short length of spray-penetration are required. A fuel-spray simulation was previously developed; that is, the air/fuel-mixture simulation was integrated with the liquid-column-breakup simulation. The developed fuel-spray simulation was used to optimize the nozzle shapes of fuel injectors for gasoline direct-injection engines.

In the present study, the factors that influence spray-penetration length were identified by the numerical simulation. The simulation results were validated by comparing the simulated spray-penetration length with the measured ones and revealing good agreement between them. Angle α was defined as that formed between the direction of flow entering the nozzle inlet and the direction of flow leaving the nozzle outlet; in other words, a indicates a change of flow direction. It was found that α and spray-penetration length was closely related. Velocity that are accelerated with a were studied, and it was found that the velocity within a plane perpendicular to the center axis of the nozzle increases with increasing α.
Fast Measurement of Soot by In-Situ LII on a Production Engine
Authors: Zhang Zhen , Stadlbauer Stephan , Viskup Richard , Fuerhapter Richard , del Re Luigi , Bergmann Alexander , Reinisch Tristan
Published: December 2014

The contribution of transient emissions to total emissions is becoming more important in view of the improvement of steady state emissions and after-treatment systems. For a critical pollutant, namely soot, there is no commercially available measurement system able to measure sufficiently fast on production engines. This paper presents a measurement setup based on in-situ Laser Induced Incandescence (LII) allowing high speed, frequent soot measurements in a production engine. The setup consists of a pulsed laser system, a fast optical detector and a special, compact designed in-situ optical LII probe which makes it possible to change the measurement location easily. System speed is assessed among other approaches, by using eleven well defined soot steps obtained by injection pulses under controlled conditions on a highly dynamic test bench. The effect of these pulses for a production four-cylinder 2 lt. Euro 5 Diesel engine is measured at three different positions (at tailpipe, downstream of the turbine and in exhaust manifold). The features of LII intensity are extracted by principle component analyses (PCA) and compared with a fast and commercially available device (AVL Opacimeter) at last. The results show that the measurements with the proposed setup are able to detect all peaks in contrast to the commercially available device.
Sensitivity Analysis of Cylinder Head Fatigue Life Prediction Using Statistical Models
Authors: Szasz Christoph , Lauer Sven
Published: December 2014

For the efficient virtual development of combustion engine cylinder heads in terms of high cycle fatigue (HCF) it is highly important to have a reliable development process that represents reality in the best possible way. Most of today’s standard HCF procedures are capable of delivering high quality results for a specific load combination. However, loads are usually subject to variation. This is also valid for loads the cylinder head is subjected to. Assembly loads and operating loads considered during the virtual development process are widely determined by the production process which again is subject to variation due to certain tolerances, wear of the tooling equipment etc. As it is highly important to ensure the fatigue design of a cylinder head, there is the need for new analysis models capable of capturing every possible load variation.

Within the framework of this paper the influence of different variable loading parameters on the cylinder head HCF margin of a heavy duty diesel engine will be discussed. A design of experiments (DoE) analysis is used together with the 3-d finite element method (FEM) for the investigations. Furthermore a methodology for the probabilistic assessment of the cylinder head HCF margin based on stochastic loading data is introduced. At the same time an effective methodology for the identification of the worst case boundary conditions for HCF analysis will be presented.

With the presented probabilistic method it is possible to achieve a highly accurate prediction of the HCF design margin. Due to the probabilistic approach a better understanding of the entire system is possible, as the interaction between input and output parameters can be illustrated. Therefore HCF optimization problems can be encountered more effectively. Furthermore the presented methodology can be used for error estimation of analysis results and assessment of the result sensitivity. Thus, a borderline layout of the cylinder head can be achieved. Also the minimum input information quality, which is required for a profound HCF analysis, can be assessed by using the sensitivity analysis presented. Therefore the proposed methods enable a fast and reliable development of cylinder heads and other combustion engine components.
Nano Napier Steel Second Ring for SI Applications
Authors: Sytsma Steve , Rabassa Erich
Published: December 2014

Piston top compression rings utilized in North American Spark Ignition (SI) passenger car and light truck engines have undergone a significant migration driven by desire to reduce axial height, mass, radial thickness, wear, incidence of risk of foundry defects and to enable utilization of a consistent, global material independent of manufacturing location.

Second rings utilized in similar applications are now in the earlier stages of a similar migration.

This paper will present product development of an innovative steel second ring including engine testing (blowby, and lube oil consumption via radiometric tracer method), supplemented by simulation modeling utilizing MIT code, including several more conventional ring cross sectional alternatives.
Estimation Methodology for Automotive Turbochargers Speed Fluctuations due to Pulsating Flows
Authors: Ponti F. , Ravaglioli V. , De Cesare M.
Published: December 2014

Turbocharging technique, together with engine downsizing, will play a fundamental role in the near future as a way to reach the required maximum performance while reducing engine displacement and, consequently, CO2 emissions.

However, performing an optimal control of the turbocharging system is very difficult, especially for small engines fitted with a low number of cylinders. This is mainly due to the high turbocharger operating range and to the fact that the flow through compressor and turbine is highly unsteady, while only steady flow maps are usually provided by the manufacturer. In addition, in passenger cars applications, it is usually difficult to optimize turbocharger operating conditions because of the lack of information about pressure/temperature in turbine upstream/downstream circuits and turbocharger rotational speed.

This work presents a methodology suitable for instantaneous turbocharger rotational speed determination through a proper processing of the signal coming from an accelerometer mounted on the compressor diffuser or a microphone faced to the compressor. The presented approach can be used to evaluate turbocharger speed mean value and turbocharger speed fluctuation (due to unsteady flow in turbine upstream and downstream circuits), that can be correlated to the power delivered by the turbine.

The whole estimation algorithm has been developed and validated for a light duty turbocharged Common-Rail Diesel engine mounted in a test cell. Nevertheless, the developed methodology is general and can be applied to different turbochargers, both for Spark Ignited and Diesel applications.
Filtration Characteristics of Fuel Neutral Particulates Using a Heterogeneous Multi-Scale Filtration Model
Authors: Gong Jian , Rutland Christopher J.
Published: December 2014

Filtration characteristics of fuel neutral soot particulate were studied using a recently developed heterogeneous multi-scale filtration (HMF) model. In the HMF model, a PDF based pore size distribution and a porosity distribution across the filter wall are introduced to represent the heterogeneous multi-scale porous structure. The HMF model was validated by an exhaust filtration analysis (EFA) system, which was designed for fundamental experimental filtration studies.

Various sources of particulates from combustion engines were used in the filtration studies. Some particulates were sampled from a spark ignited direct injection (SIDI) engine fueled with gasoline and ethanol blends. Particulates from a compression ignition engine fueled with diesel for conventional and advanced combustion regimes were investigated as well. The micro-structure of the porous wall was found to be more critical and necessary to simulate filtration of particulates from gasoline and advanced diesel combustion engines than those from conventional diesel combustion engines. The interactions between the porous wall and trapped particulates were investigated. The dynamic filtration characteristics including filtration efficiency, pressure drop and particulate distribution inside the wall are strongly dependent on total particulate volume rather than total particulate number concentration. The change of the filter structure as well as the shape of the particulate size distribution play important roles on particulate penetration.
CFD Simulation of Gasoline Compression Ignition
Authors: Kodavasal Janardhan , Kolodziej Christopher , Ciatti Stephen , Som Sibendu
Published: December 2014

Gasoline compression ignition (GCI) is a low temperature combustion (LTC) concept that has been gaining increasing interest over the recent years owing to its potential to achieve diesel-like thermal efficiencies with significantly reduced engine-out nitrogen oxides (NOx) and soot emissions compared to diesel engines. In this work, closed-cycle computational fluid dynamics (CFD) simulations are performed of this combustion mode using a sector mesh in an effort to understand effects of model settings on simulation results. One goal of this work is to provide recommendations for grid resolution, combustion model, chemical kinetic mechanism, and turbulence model to accurately capture experimental combustion characteristics. Grid resolutions ranging from 0.7 mm to 0.1 mm minimum cell sizes were evaluated in conjunction with both Reynolds averaged Navier-Stokes (RANS) and Large Eddy Simulation (LES) based turbulence models. Solution of chemical kinetics using the multi-zone approach is evaluated against the detailed approach of solving chemistry in every cell. The relatively small primary reference fuel (PRF) mechanism (48 species) used in this study is also evaluated against a larger 312-species gasoline mechanism.

Based on these studies the following model settings are chosen keeping in mind both accuracy and computation costs — 0.175 mm minimum cell size grid, RANS turbulence model, 48-species PRF mechanism, and multi-zone chemistry solution with bin limits of 5 K in temperature and 0.05 in equivalence ratio. With these settings, the performance of the CFD model is evaluated against experimental results corresponding to a low load start of injection (SOI) timing sweep. The model is then exercised to investigate the effect of SOI on combustion phasing with constant intake valve closing (IVC) conditions and fueling over a range of SOI timings to isolate the impact of SOI on charge preparation and ignition. Simulation results indicate that there is an optimum SOI timing, in this case −30°aTDC (after top dead center), which results in the most stable combustion. Advancing injection with respect to this point leads to significant fuel mass burning in the colder squish region, leading to retarded phasing and ultimately misfire for SOI timings earlier than −42°aTDC. On the other hand, retarding injection beyond this optimum timing results in reduced residence time available for gasoline ignition kinetics, and also leads to retarded phasing, with misfire at SOI timings later than −15°aTDC.
A Multi-Component Blend as a Diesel Fuel Surrogate for Compression Ignition Engine Applications
Authors: Pei Yuanjiang , Mehl Marco , Liu Wei , Lu Tianfeng , Pitz William J. , Som Sibendu
Published: December 2014

A mixture of n-dodecane and m-xylene is investigated as a diesel fuel surrogate for compression ignition engine applications. Compared to neat n-dodecane, this binary mixture is more representative of diesel fuel because it contains an alkyl-benzene which represents an important chemical class present in diesel fuels. A detailed multi-component mechanism for n-dodecane and m-xylene was developed by combining a previously developed n-dodecane mechanism with a recently developed mechanism for xylenes. The xylene mechanism is shown to reproduce experimental ignition data from a rapid compression machine and shock tube, speciation data from the jet stirred reactor and flame speed data. This combined mechanism was validated by comparing predictions from the model with experimental data for ignition in shock tubes and for reactivity in a flow reactor. The combined mechanism, consisting of 2885 species and 11754 reactions, was reduced to a skeletal mechanism consisting 163 species and 887 reactions for 3D diesel engine simulations. The mechanism reduction was performed using directed relation graph (DRG) with expert knowledge (DRG-X) and DRG-aided sensitivity analysis (DRGASA) at a fixed fuel composition of 77% of n-dodecane and 23% m-xylene by volume. The sample space for the reduction covered pressure of 1–80 bar, equivalence ratio of 0.5–2.0, and initial temperature of 700–1600 K for ignition. The skeletal mechanism was compared with the detailed mechanism for ignition and flow reactor predictions. Finally, the skeletal mechanism was validated against a spray flame dataset under diesel engine conditions documented on the Engine Combustion Network (ECN) website. These multi-dimensional simulations were performed using a Representative Interactive Flame (RIF) turbulent combustion model. Encouraging results were obtained compared to the experiments with regards to the predictions of ignition delay and lift-off length at different ambient temperatures.
Onboard Hydrogen Generation for IC Engine Emissions Reduction
Authors: Mastanduno Richard , Roychoudhury Subir , Etemad Shahrokh
Published: December 2014

Improvement of internal combustion engine emissions and performance by the introduction of a reducing gas such as hydrogen has been the subject of research in recent years. The approach reduces engine exhaust emissions and improves fuel consumption. The gas may be introduced into the engine intake or upstream of the exhaust catalyst for different effects. To date, the technique has not been implemented due to the need for onboard storage or generation of hydrogen that complies with suitability for automotive applications.

In industrial processes and stationary applications, reforming reactors are well known, highly efficient, and durable means to convert liquid fuels such as diesel into hydrogen or other reducing gas mixtures (synthesis gas). Efficiency and durability for thousands of hours is required for these applications for economic viability. For an automotive application, however, in addition to the above features, fast transient response (e.g. during start up and turndown), compactness, and low cost are also required — while maintaining sufficient durability for the application. Also, the need for liquid water common to reactions such as steam reforming or auto-thermal reforming are impractical for automotive applications. A waterless catalytic partial oxidation approach avoids this shortcoming but is not without its own set of problems. Material durability, fuel/air mixing, coke avoidance and reliable ignition means are among the challenges for a practical automotive hydrogen production solution. The catalyst for reacting the fuel must be tolerant to sulfur content common to fuels in use today, and must have resistance to fouling by carbon formation.

To overcome these challenges, Precision Combustion, Inc. (PCI) has developed a diesel-fueled waterless catalytic partial oxidation reformer with efficiency and size suitable for onboard synthesis gas production at low cost. The goal of the development effort was to produce a novel mechanical design with the high efficiency of stationary reformers in a small package which could be operated with low parasitic loss from balance of plant components to maintain high engine efficiency. The reactor design (size, form factor) is discussed, along with performance data showing transient and steady state response of the prototype reactor. Catalytic partial oxidation (CPOX) of heavy fuels such as diesel poses unique challenges, relating to coking and fuel conversion efficiency, which have been addressed and presented in this paper.
The Effects of Spray Angles on Spray Combustion of Diesel and Biodiesel in Diesel Engines
Authors: Shen Cai , Cheng Way Lee , Lee Chia-fon F.
Published: December 2014

The effects of injection angle on the spray dynamics, combustion process and soot emission were studied. Two different fuels, diesel and biodiesel, were tested on a DIATA optical engine by performing numerical simulation using the modified KIVA III V2. Simulations under three different injection angles and two different injection pressures were performed. The model was verified by comparing the spray penetrations and pressure traces with the experimental measurements. The simulation results show that lower injection pressure strengthens spray operation, and longer ignition delay and lower peak combustion pressure and peak heat release rate are observed. Injection angle of 110° produces the highest peak combustion pressure and heat release rate for diesel fuel. Unlike diesel combustion, the peak combustion pressure and heat releases rate for biodiesel increases as the spray angle narrows. Soot located in the squish or the regions above the piston bowl are readily oxidized due to abundance of oxygen. Portions of fuel are burnt in the region about the piston bowl or squish for both spray angle of 150° and 70°. Soot located within the piston bowl is oxidized at a much slower rate due to deficient oxygen after combustion. Soot emission mainly due to soot within in the piston bowl at the end of combustion. Any strategy that pushes soot out of piston can improve the oxidization process, thus, reducing soot emission. Extra oxygen in biodiesel also helps in reducing the emission. Biodiesel has longer ignition delay over diesel for initial injection. Ignition delay for main injection is negligible in all the cases studied due to the cylinder condition upon main injection. Soot emissions are reduced from biodiesel blends and this is consistent with the general observation.
Efficient Computation Methods for Combustion Reaction Kinetics
Authors: Wang Mianzhi , Lee Chia-fon F.
Published: December 2014

This research presents multiple strategies to improve the computation efficiency of solving combustion reaction kinetics. All strategies in this work are error-free compared to other methods based on result tabulation, dynamic mechanism reduction, and stiffness removal with quasi-equilibrium assumption and lower-dimensional manifold attraction. In the presented methods, the Jacobian matrix are solved by either direct linear solver or preconditioned Krylov subspace method. Different Jacobian matrix construction methods are designed with exploiting the characteristics of reaction network. The methods are systematically tested using reaction mechanisms of different size, and with different initial conditions. The performance of the presented methods are also compared with existing codes. The results shows that each specific method has higher performance for certain mechanisms. The reason for the performance differences are analyzed and a guideline for selecting method is provided. The presented methods are implemented into CFD code to efficiently simulate the reaction flow without dealing with the heterogeneity caused by dynamic mechanism reduction, quasi-equilibrium assumption, etc. It is also possible to combine the presented methods with problem-reducing methods to further optimize the reaction kinetics computation.
Numerical Investigation of the Unstable Wave on a Planar Liquid Sheet Produced by an Air-Blast Atomizer
Authors: Zhou Hua , Lee Chia-fon F. , Lee Timothy H.
Published: December 2014

The unstable surface wave on a liquid sheet produced by an air-blast atomizer during primary breakup process was investigated by numerical simulation. The results of simulation were verified by comparison of primary breakup time and breakup length with accessible experimental data reported in technical papers. The frequency characteristics of stream-wise unstable wave at different axial locations were investigated by applying Discrete Fourier Transform (DFT). It was found that when there is no disturbance induced by internal flow, there is no specific frequency which is favored by shear instability near the nozzle exit, and the characteristic frequency of the dominant wave decreases along stream-wise direction due to the decrease of relative velocity. By applying Discrete Particle Method (DPM), the motion of fluid particles inside the liquid sheet was able to be tracked, and the Lagrangian characteristics of fluid particles can be partially revealed. The growth of stream-wise unstable wave was found to possess strong spatial characteristics by investigating the pathlines and streaklines of fluid particles. A rough evaluation for the stream-wise speed of fluid particles and the propagation velocity of unstable wave showed that fluid particles move faster than unstable wave in stream-wise direction, thus, relative motion exists between fluid particles and stream-wise wave. This relative motion could lead to huge acceleration of fluid particles, which could trigger Rayleigh-Taylor (RT) instability to induce transverse disintegration. Some complex behaviors of fluid particles inside the liquid sheet were observed, e.g. eddy-like structures formed by fluid particles.
A Study of Combustion Inefficiency in Diesel LTC and Gasoline-Diesel RCCI via Detailed Emission Measurement
Authors: Dev Shouvik , Divekar Prasad , Xie Kelvin , Han Xiaoye , Chen Xiang , Zheng Ming
Published: December 2014

Reduction of engine-out NOx emissions to ultra-low levels is facilitated by enabling low temperature combustion (LTC) strategies. However, there is a significant energy penalty in terms of combustion efficiency as evidenced by the accompanying high levels of hydrocarbon (HC), carbon monoxide (CO), and hydrogen emissions. In this work, the net fuel energy lost as a result of incomplete combustion in two different LTC regimes is studied. The first LTC strategy, partially premixed compression ignition (PPCI), is investigated using a single, high pressure, in-cylinder injection of diesel fuel along with the application of exhaust gas recirculation (EGR). The second strategy includes dual-fuel application – reactivity controlled compression ignition (RCCI) of port injected gasoline and direct injected diesel. Moderate to high levels of EGR are necessary during engine operation in either of the two LTC pathways. A detailed analysis of the incomplete combustion products was conducted while the engine was operated in the aforementioned LTC modes. Speciation analysis of hydrocarbons was performed by sampling the exhaust gas in an FTIR. The total HC and the CO emissions were simultaneously measured using an FID and an NDIR, respectively. The production of hydrogen during the combustion process was also evaluated using a mass spectrometer. Engine tests were conducted at a baseline load level of 10 bar IMEP in the PPCI and RCCI modes. Load extension tests, up to 17 bar IMEP, were then conducted in the RCCI mode by increasing the gasoline-to-diesel fuel ratio. Test results indicated that CO, H2, and light HC made up for most of the combustion in-efficiency in the PPCI mode while heavier HC and aromatics were significantly higher in the RCCI mode.
Predictions of Flow Separation at the Valve-Seat for Steady-State Port-Flow Simulation
Authors: Fang Tao , Singh Satbir
Published: December 2014

Steady-state port-flow simulations with static valve lift are often utilized to optimize the performance of intake system of an internal combustion engine. Generally, increase in valve lift results in higher mass flow rate through the valve. But in certain cases, mass flow rate can actually decrease with increased valve lift, caused by separation of turbulent flow at the valve-seat. Prediction of this phenomenon using computational fluid dynamics (CFD) models is not trivial. It is found that the computational mesh significantly influences the simulation results. A series of steady-state port flow simulation are carried out using a commercial CFD code. Several mesh topologies are applied for the simulations. The predicted results are compared with available experimental data from flow bench measurements. It is found that the flow separation and reduction in mass flow rate with increased valve lift can be predicted when high mesh density is used in the proximity of the valve seat and the walls of the intake port. Higher mesh density also gives better predictions of mass flow rate compared to the experiments, but only for high valve lifts. For low valve lifts, the error in predicted flow rate is close to 13%.
The Dynamics of Second Ring Flutter and Collapse in Modern Diesel Engines
Authors: Cheng Chao , Schock Harold , Richardson Dan
Published: December 2014

Second ring fluttering and radial ring collapse are recognized as having significant influences on engine blowby and oil consumption. As the gas flow is coupled with the piston ring motion, understanding the ring dynamics is important for understanding not only the engine blowby mechanism, but also oil consumption mechanisms and how to control them. Only second ring flutter and collapse that occurs around the top dead center firing conditions is examined in this paper based on a modern heavy-duty diesel engine. However, the principles described are equally applicable to all engines.

First, the authors describe the fundamental mechanisms of how second ring fluttering and radial ring collapse occurs. This is described by examining the forces that are acting on the second ring. Then, two cases are shown. One case shows second ring flutter and the other case shows stable second ring motion. The reasons for these two different cases are explained, including the effect of static twist and the end gaps of the rings.

A sensitivity study was performed to evaluate the effect of changing the top and second ring end gaps on ring lift. It was shown how the gaps could affect the second ring flutter and ring collapse.

It is concluded that the second ring will be more likely to flutter or collapse if it has a negative static twist, if the second ring end gap is large, and/or if the top ring end gap is small. If the second ring does not flutter, it may still be possible to design the ring pack such that there is not any reverse blowby. However, this must be carefully studied and controlled or the second land pressures will be too high, resulting in reverse blowby and/or top ring lifting.
Full Load Performance Optimization Based on Turbocharger Speed Evaluation via Acoustic Sensing
Authors: Cavina Nicolò , De Cesare Matteo , Ravaglioli Vittorio , Ponti Fabrizio , Covassin Federico
Published: December 2014

Turbocharger performance optimization on passenger car engines is particularly challenging, especially in case of severe engine downsizing and downspeeding.

On high performance engines (e.g., heavy duty truck applications) turbocharger speed measurement is usually performed with the aim of maximizing engine power and torque, limiting turbocharger over-speed, which is harmful for its durability and reliability. This solution is too expensive for passenger cars, and the turbocharger speed sensor is typically not available.

In this work, an innovative and low cost sensing chain for the rotational speed evaluation of the turbocharger is applied. With this information, obtained via an acoustic sensor, a new turbocharger control architecture has been developed to optimize turbocharger performance, in order to improve engine output torque under full load conditions.

After a brief description of the new sensing chain and of the electronic components developed to manage this kind of information, the paper shows the new control architecture that takes advantage of the turbocharger speed information.

Moreover, experimental results on a small turbocharged Diesel engine for passenger car applications are presented, demonstrating the achieved benefits.
Numerical Investigation of the Performance of a High Pressure Direct Injection (HPDI) Natural Gas Engine
Authors: Lee Won Geun , Montgomery David
Published: December 2014

High Pressure Direct-Injection (HPDI) is a technology option for engines used in mobile equipment applications where use of LNG as a fuel is desired. Using the combination of a diesel pilot injection and direct gas injection, HPDI has the potential to deliver low emissions, excellent transient performance, high efficiency, and high gas substitution. When the HPDI program was initially undertaken, in order to aid in initial hardware design, 3-dimensional computational fluid dynamic modeling was conducted to understand the mixing and reaction processes in the combustion chamber of an HPDI engine. Gaining insight into qualitative trends of operation parameters and hardware configurations was a first critical step toward delivering a hardware set to demonstrate HPDI natural gas combustion system capabilities.

To model the combustion of multi-component fuel at arbitrary constituent ratios, a combustion model based on a detailed chemical kinetics approach was employed. Several published mechanisms and combinations of established mechanisms were tested by comparing results with existing fumigated dual fuel engine results. The result shows that some of combined mechanisms for n-heptane combustion and methane combustion are capable of adequately predicting combustion behavior in diesel-natural gas dual fuel combustion systems. One of the reduced n-heptane mechanisms (by Patel et al.) also matched dual fuel combustion results reasonably well.

This preliminary simulation study was conducted with typical trapped air conditions and fuel quantities matching the energy delivery for a 100 % load condition in existing DI diesel engines. A full 360-degree mesh at intake valve closing was constructed and a detailed geometry of the gas injector nozzle and sac area was modeled in locally refined grids using a Caterpillar proprietary CFD code that accepts industry standard mechanisms. The diesel pilot injection followed by gas injection and resulting combustion inside an HPDI engine was simulated from IVC through the compression and combustion strokes. The operating parameters — such as diesel pilot injection timing, pilot injection amount, and start of gas injection — were varied, and the effect on IMEP, NOx, CO and cylinder pressure were investigated. It was shown that the start of gas injection is the strongest parameter for control of combustion. Subsequent to the work discussed in this paper, the hardware configuration established as optimal during the modeling work was carried forward to the physical engine testing and was successful in delivering the performance and emissions goals without modification, demonstrating the accuracy and value of modern combustion modeling.
Impact of Very High Injection Pressure on Soot Emissions of Medium Speed Large Diesel Engines
Authors: Engelmayer Michael , Taucher Gert , Wimmer Andreas , Hirschl Gernot , Kammerdiener Thomas
Published: December 2014

Measures exist to adjust tailpipe NOx emissions to assigned values, for example cooled exhaust gas recirculation (EGR) or a SCR catalyst in conjunction with urea. The situation is quite different with soot when use of a trap is not feasible for reasons of cost, space requirements and maintenance. Due to the highly complex soot formation and oxidation process, soot emissions can’t be targeted as easily as NOX. So how can soot be kept within the limits?

In principle, soot can be controlled by allocating sufficient oxygen and establishing good mixing conditions with vaporized fuel. The most effective measures target the injection system, e.g. increasing injection pressure, applying multiple injections, optimizing nozzle geometry.

To investigate the impact of very high injection pressure on soot, an advanced injection system with rail pressure capability up to 3000 bar and a Bosch injector was installed at the Large Engines Competence Center (LEC) in Graz. Full load and part load operating points at constant speed and in accordance with the propeller law were investigated at the test bed to quantify the impact of high injection pressure on soot emissions. Test runs were conducted with both SCR and EGR while varying injection timing and air-fuel ratios. Use of a statistical method, Design of Experiments (DOE), helped reduce the number of tests.

Optical investigations of the spray and combustion were conducted. The goal was to obtain soot concentration history traces with the two color method in order to better understand how soot originates and to be able to calibrate 3D CFD FIRE spray models for use with injection pressures of up to 3000 bar.

Very low soot emissions can be achieved using high pressure injection, even when EGR is applied. DOE results provide a clear picture of the relationships between the parameters and can be used to optimize set values for the whole speed and load range.

A reliable spray break up model can be used in further 3D CFD simulation to investigate how to reduce soot emissions.
Simulation of Dual-Fuel Diesel Combustion With Multi-Zone Fuel Spray Combustion Model
Authors: Kuleshov Andrey , Mahkamov Khamid , Kozlov Andrey , Fadeev Yury
Published: December 2014

There is increasing interest in application of various alternative fuels in marine diesel engines, including methanol. One of the challenges in the relevant research is the development of computer codes for simulation of the dual-fuel working process and engineering optimization of engines. In this work the mathematical model is described which simulates a mixture formation and combustion in an engine with a dual-fuel system, in which methanol is used as main fuel and a pilot portion of diesel oil is injected to ignite methanol. The developed combustion model was incorporated into the existing engine full cycle thermodynamic simulation tool, namely DIESEL-RK [1]. The developed combustion model includes the self-ignition delay calculation sub-model based on the detail chemistry simulation of methanol pre-combustion reactions, sub-model of evaporation of methanol droplets, submodels of methanol fuel sprays penetration, spray angle and droplets forming, respectively. The developed computer code allows engineers to account for the arbitrary shape of the combustion chamber. Additionally, each fuel system (for methanol and diesel oil) may include several injectors with arbitrary oriented nozzles with different diameters and central, off-central and side location in the combustion chamber. The fuel sprays evolution model consists of equations with dimensionless parameters to account for fuel properties and in-cylinder conditions. Specifics of injection pressure profiles and interaction of sprays with the air swirl and between themselves are also considered. The model allows engineers to carry out rapid parametric analysis. Results of modelling for a medium speed dual-fuel diesel engine are presented which demonstrate a good agreement between calculated and experimental heat release curves and integral engine data.
The History and Evolution of Optically Accessible Research Engines and Their Impact on Our Understanding of Engine Combustion
Authors: Miles Paul C.
Published: December 2014

The development and application of optically accessible engines to further our understanding of in-cylinder combustion processes is reviewed, spanning early efforts in simplified engines to the more recent development of high-pressure, high-speed engines that retain the geometric complexities of modern production engines. Limitations of these engines with respect to the reproduction of realistic metal test engine characteristics and performance are identified, as well as methods that have been used to overcome these limitations. Lastly, the role of the work performed in these engines on clarifying the fundamental physical processes governing the combustion process and on laying the foundation for predictive engine simulation is summarized.
Enforcing Club Seat Contracts in Professional Sports
Authors: Reese James , Dodds Mark , Southall Richard , Heisey Kevin
Published: December 2014

A professional sport team began play in a new stadium. Although the old facility had no such seat inventory, one of the features at the new facility was the addition of 8,800 club seats. According to the marketing materials provided by the team, the new club-seat inventory offers amenities not available at the old stadium, including upscale concessions, a heated and air-conditioned lounge, padded seats, and increased restroom capacity. After the opening of the new stadium, fans complained about their club seat experience, including long concessions and restrooms lines (typically longer than at the old facility) and consistent premium food shortages. In the off-season, the team began the process of sending ticket-renewal invoices for the upcoming season. Approximately 100 club-seat holders declined to renew, claiming the team breached the contract by not providing the services promised. The team attempted to negotiate with the affected customers with limited success.
Cell Competition and Immunity
Authors: Purnell Beverly A.
Published: December 2014

Components of the innate immune system are repurposed to eliminate weak cells during development.
Endocrine Hedgehog
Authors: VanHook Annalisa M.
Published: December 2014

In flies, circulating Hedgehog produced by the gut coordinates growth and development with nutritional status.
About TMIE to Hear
Authors: Berndt Jason D.
Published: December 2014

TMIE is a component of the mechanotransduction channel complex of inner ear hair cells.
Rapidly Reorienting Microtubules
Authors: Gough Nancy R.
Published: December 2014

Auxin mediates a nontranscriptional pathway to inhibit cell expansion by rapidly reorienting microtubules.