bluuebunny/crossref_metadata_2025 huggingface dataset:
Under-Expanded Gaseous Flow at a Straight Micro-Tube Exit
Authors: Yoshimaru Takahiro , Asako Yutaka , Yamada Toru
Published: February 2014

This paper focuses on under-expanded gaseous flow at a straight micro-tube exit. The pitot total pressure of gas flow (jet) in the downstream region from a straight micro-tube exit was measured by a total pressure pitot tube to accumulate data for validation of numerical results. A micro-tube of 495μm in diameter and 56.3 mm in length and a total pressure pitot tube of 100 μm in outer diameter were used. The pitot total pressure was measured at intervals of 0.1 mm in both the flow and radial directions. The measurement was done for the mass flow rates of 9.71 × 10−5 kg/s and 1.46 × 10−4 kg/s. The data were accumulated for validation of the numerical results to reveal the characteristics of the under-expanded gas flow at the exit of a micro-tube. Comparisons were conducted for numerical results of corresponding cases and a slight discrepancy can be seen between numerical and experimentally measured pitot total pressures.
The Effect of Annulus Performance Parameters on Rotor-Stator Cavity Sealing Flow
Authors: Mirzamoghadam Alexander V. , Heitland G. , Molla-Hosseini K.
Published: February 2014

The amount of cooling air assigned to seal high pressure (HP) turbine rim cavities is critical for performance as well as component life. Insufficient air leads to excessive hot annulus gas ingestion and its penetration deep into the cavity compromising disk or cover plate life. Excessive purge air, on the other hand, adversely affects performance. This paper is a continuation of the authors' work on ingestion reported by Mirzamoghadam et al. (2008) (“3D CFD Ingestion Evaluation of a High Pressure Turbine Rim Seal Disk Cavity,” ASME Paper No. GT2008-50531), where the main focus of that investigation was to qualitatively describe ingestion driven by annulus circumferential pressure asymmetry under constant annulus conditions and rotational speed. In this paper, the research team investigated the variation of annulus circumferential pressure fluctuation and rotational speed on the double overlap platform rim seal cavity reported in part-1. The outcome from this study was to map out the resulting nondimensional minimum sealing flow (minimum value of Cw or Cw,min) as it relates to entrained ingestion in the absence of cavity cooling flow (Cw,ent). As was done in part-1, the runs were made with 3D computational fluid dynamics (CFD) in setup/run mode option using Fine/Turbo. At two rotational speeds, annulus conditions were varied by reducing turbine inlet pressure (i.e., mass flow) from the baseline operating condition, and the resulting pressure fluctuation was quantified. In addition, an investigation to assess the selected aft-located mixing plane steady state solution for this study as compared to the forward-located steady run was performed using unsteady (nonlinear Harmonics) CFD as the referee. The results yielded the linear decrease in Cw,ent at fixed rotational Reynolds number as annulus Reynolds number was decreased. Moreover, the rate of change in entrained flow sharply increases with increase in rotational Reynolds number. As annulus mass flow is reduced to a critical value defined by annulus-to-rotational Reynolds number ratio, the CFD prediction for Cw,ent converges to the turbulent boundary layer entrainment solution for the rotor, and Cw,min reverts to the rotational Reynolds number dominating region. The results from this study were compared to what has been observed by a previous study for a single overlap platform geometry. The resulting design curve allows insight in relating cavity purge flow requirements versus turbine cycle parameters which could lead to better efficiency.
Influence of Coolant Density on Turbine Platform Film-Cooling With Stator–Rotor Purge Flow and Compound-Angle Holes
Authors: Liu Kevin , Yang Shang-Feng , Han Je-Chin
Published: February 2014

A detailed parametric study of film-cooling effectiveness was carried out on a turbine blade platform. The platform was cooled by purge flow from a simulated stator–rotor seal combined with discrete hole film-cooling. The cylindrical holes and laidback fan-shaped holes were accessed in terms of film-cooling effectiveness. This paper focuses on the effect of coolant-to-mainstream density ratio on platform film-cooling (DR = 1 to 2). Other fundamental parameters were also examined in this study—a fixed purge flow of 0.5%, three discrete-hole film-cooling blowing ratios between 1.0 and 2.0, and two freestream turbulence intensities of 4.2% and 10.5%. Experiments were done in a five-blade linear cascade with inlet and exit Mach number of 0.27 and 0.44, respectively. Reynolds number of the mainstream flow was 750,000 and was based on the exit velocity and chord length of the blade. The measurement technique adopted was the conduction-free pressure sensitive paint (PSP) technique. Results indicated that with the same density ratio, shaped holes present higher film-cooling effectiveness and wider film coverage than the cylindrical holes, particularly at higher blowing ratios. The optimum blowing ratio of 1.5 exists for the cylindrical holes, whereas the effectiveness for the shaped holes increases with an increase of blowing ratio. Results also indicate that the platform film-cooling effectiveness increases with density ratio but decreases with turbulence intensity.
Design and Evaluation of an Embedded Sensor in a Polymer Sealing Structure “Smart Seal”
Authors: Krutz Gary , Gallien Timu , Newell Brittany , Stewart Frank
Published: February 2014

Research developed an embedded sensor system within an o-ring capable of monitoring seal life and health. An electronic system interfacing signal generation and processing was used to determine if the embedded sensor system was capable of capturing and responding to physical changes within an o-ring. Signals were conditioned in the pico-farad (pF) range with example failures exhibiting signal changes on the order of 30% to over 100%. Physical prototype results show that the embedded sensor system responds to load conditions (i.e., preload), cuts, puncture and chemical incompatibility.
Model-Based Development of Health Monitoring Functions for Aircraft Hydraulic Systems
Authors: Poole Kevin , Thielecke Frank , Maediger Cornelia
Published: February 2014

Unforeseen failures of hydraulic power generation systems can cause costly operation interruptions of aircraft. To overcome this, a health monitoring of the system components is desirable but not yet available. In this paper, a method is presented that allows a model-based development of such a capability.

This method uses physics-based models of system components in order to derive their behavior at considered fault modes with several extents. The gained knowledge is transferred into a model of the entire hydraulic system. This model is used to determine the fault effects on the system states in order to find candidate positions for sensors. The method allows finding an optimal set of sensors that enables the detection and isolation of system component faults. The system model is used further for the creation of a simplified steady-state nominal model, which is required for feature generation. On the basis of these features, support vector machines are trained for fault detection and isolation as well as the diagnosis of the actual fault extent. The developed health monitoring functions are validated on a test rig.
A Simulation Model of a Hydraulic Buck Converter Based on a Mixed Time Frequency Domain Iteration
Authors: Kogler Helmut , Scheidl Rudolf , Ehrentraut Michael
Published: February 2014

Digital hydraulics is an opportunity to realize simple, robust, cheap and energy efficient hydraulic drives. In such systems digital on/off valves are used instead of proportional valves. Moreover, in hydraulic switching converters the valves are actuated within a few milliseconds, which create sharp pressure changes and, in turn, significant wave propagation effects in the pipe system. For a proper design of digital hydraulic systems a sound understanding of these effects is required to achieve the desired behavior of the switching drive system. In such converters, like the buck-, boost or boost-buck-converter, the inductance is one crucial component. It is realized by a simple pipe mainly for cost reasons. Furthermore, switching converters contain some components with nonlinear characteristics, like valves or accumulators, which prevent a comprehensive analysis in frequency domain. For a convenient analysis a qualified model of a hydraulic buck converter based on a mixed time frequency domain iteration is presented. Main parameters of this model are identified and wave propagation effects in the inductance pipe of the converter are investigated by simulation.
Design of Bidirectional Check Valve for Discrete Fluid Power Force System for Wave Energy Converters
Authors: Hansen Anders Hedegaard , Pedersen Henrik C. , Andersen Torben O.
Published: February 2014

Discrete fluid power force systems consisting of a multi-chamber cylinder, a switching manifold and common pressure lines have been proposed as a technology for increasing the efficiency of the power take off system in ocean wave energy converters. However the force shifting of these discrete systems introduces large switching losses, especially when large pressure difference is present across the valves in the manifold. The current paper therefore focus on designing a bidirectional check valve for use in the switching manifold of the discrete force systems. The use of the bidirectional check valve enables passive force switching under minimal pressure difference, hence minimal energy loss. The bidirectional check valve is designed with a rated flow in the range of 1000L/min@5bar. The flow direction of the bidirectional check valve is set by the setting the pilot pressure. This paper presents a functionality test of a 125 L/min@5bar bidirectional check, leading to the design and modelling of a bidirectional check valve for ocean wave energy. It shows that a feasible bidirectional check valve may be configured by employing a multi-poppet topology for the main stage and utilising a 3/2 switching valve as pilot stage. The bidirectional check valve may operate both passive an active switching.
Stable and High Performance Energy-Efficient Motion Control of Electric Load Sensing Controlled Hydraulic Manipulators
Authors: Koivumäki Janne , Mattila Jouni
Published: February 2014

In order to achieve higher energy efficiency for hydraulic systems the Load Sensing (LS) systems, i.e. a Variable Displacement Pump (VDP) with hydro-mechanical control system, can be considered as a state-of-the-art solution. However, as is well known, these traditional hydraulic LS-systems are usually characterized by difficulties in tuning, which can lead to system stability problems. In our previous studies, we have developed a high precision motion control for hydraulic manipulators with separate meter-in meter-out controlled hydraulic actuators. Our control approach was based on the Virtual Decomposition Control (VDC) approach that ensured high motion tracking performance while rigorously guaranteeing the system stability. In this paper, we propose both energy-efficient and high performance nonlinear model based motion control scheme that utilizes the developed servocontrolled Electric Load Sensing (ELS) system for hydraulic robotic manipulators. Experimental results are presented with the proposed ELS-controlled VDP and hydraulic manipulator lifting servoactuator that utilized a separate meter-in meter-out flow control scheme.
Position Tracking of a Pneumatic Actuator Using Backstepping-Sliding Mode Control With Adaptive Friction Observer
Authors: Abd. Rahman Ramhuzaini , Sepehri Nariman
Published: February 2014

In this paper, an enhanced sliding mode control (SMC)-based controller known as backstepping-sliding mode control (B-SMC) with an adaptive friction observer is proposed for position tracking control of pneumatic actuators. The adverse effect of friction encountered in the pneumatic actuators which play a major role in pneumatic servo system is highlighted and a solution to rectify this is proposed using an adaptive LuGre-based friction observer for friction compensation. The B-SMC is experimentally applied, for the first time, on a double-acting single-rod industrial pneumatic cylinder. Comprehensive derivation as well as stability proof of the controller is presented. The performance of B-SMC with and without the friction observer is experimentally investigated. From the results, it is clearly observed that the B-SMC with the adaptive friction observer performs better (i.e. reduces the tracking as well steady-state errors of up to 30%) than the one without friction observer. Thus, the adaptive friction observer of B-SMC is identified as the key element that improved the control performance by compensating the adverse effect of friction during the position tracking tasks.
Measurements of Air Absorption and Air Release Characteristics in Hydraulic Oils at Low Pressure
Authors: Schrank Katharina , Murrenhoff Hubertus , Stammen Christian
Published: February 2014

The improvement in accuracy of one dimensional fluid power system simulations is the objective of many research projects. On one hand the accuracy depends on the underlying physical models describing the system behavior. On the other hand the equations to calculate pressure and temperature, depending on fluid properties like bulk modulus and viscosity, play an important role. Especially the consideration of impurities like air bubbles in system simulation raises a challenge in terms of fluid properties and system behavior description. The content of entrained and dissolved air in hydraulic pressure fluids are determined by the equilibrium conditions, which depend on the fluid and on the static pressure. Considering the effects of entrained air in fluid power systems and air release phenomena, like gas cavitation, the time dependency of the diffusion process and the available time to reach the saturation state has to be taken into account.

In this paper the release and the absorption of entrained air in oil is investigated. The basic objective hereby is to characterize the air release and absorption speeds. Mass conservative measurements are presented on a volume variable test-rig permitting the accurate examination of air release and absorption in pressure regions above and below atmospheric pressure. A standard mineral oil commonly used in fluid power industry as well as an ester based oil are taken for the investigations. The effect of different driving pressure gradients is analyzed by varying the velocity of the volume change of the test chamber.
Wireless Control of a Teleoperated Hydraulic Manipulator With Application Towards Live-Line Maintenance
Authors: Maddahi Yaser , Sepehri Nariman , Liao Stephen , Fung Wai-keung , Hossain Ekram
Published: February 2014

This paper presents the procedure of establishing performance charts for effective utilization of a teleoperated hydraulic manipulator working under wireless communication channels. A teleoperated system, comprising a master haptic device and an industrial hydraulic manipulator, is constructed. The master and slave communicate through a communication channel emulated using the NS2 simulator. Two sets of experiments are designed to construct performance charts that guide us to select appropriate parameters of wireless network setup by which a particular value of position error appears at the slave hydraulic manipulator end-effector. The network parameters are: configuration of environment obstruction, transmission power of the router, and distance between the master and slave sites. The first set of experiments is conducted to define three regions of tracking quality, and to construct the performance charts. The second set of experiments confirms satisfactory performance, when the teleoperated system is located within the recommended regions in the established charts. One application of this study is live-line maintenance using remotely-operated hydraulic manipulators.
Multibody Dynamics of a Fluid Power Radial Piston Motor Including Transient Hydrodynamic Pressure Models in Lubricating Gaps
Authors: Johansen Per , Roemer Daniel B. , Andersen Torben O. , Pedersen Henrik C.
Published: February 2014

The increasing interest in hydraulic transmissions in wind and wave energy applications has created an incentive for the development of high efficiency fluid power machinery. Modeling and analysis of fluid power machinery loss mechanisms are necessary in order to accommodate this demand. At present fully coupled thermo-elastic models has been used to simulate and study loss mechanisms in various tribological interfaces. Consequently, a reasonable focus of further development is to couple the interface models and the rigid body mechanics of fluid power machinery. The focus of the current paper is a multibody dynamics model of a radial piston fluid power motor, which connects the rigid bodies through models of the transient hydrodynamic lubrication pressure in the joint clearance. A finite volume approach is used to model the pressure dynamics of the fluid film lubrication. The model structure and model equations are explained in this paper and simulation results are shown in terms macroscopic and microscopic dynamics.
Passive Pneumatic Teleoperation System
Authors: Elmasry Aly , Liermann Matthias
Published: February 2014

This paper describes the modeling and control of a pneumatic tele-operation scheme, where the connection of master and slave cylinder is realized signal based but also physically via long transmission lines. The system is called passive because of the passive physical connection, which can also serve as a safety fallback solution. The advantage of this scheme is that a limited force feedback is realized with a minimum of extra effort in comparison to a teleportation system without force feedback. The stiffness of the physical connection is enhanced through a cascaded position and pressure control scheme with two proportional valves as actuators for each pneumatic line. The paper presents the mathematical model of the setup, which is used to determine the relative stability of the dynamic system as a function of control parameters. An experimental setup is presented which was set up to validate the system model. For a distance of 5 m between master and slave cylinder a stiffness of 2.4 N/mm could be established.
Dynamic Simulation and Experimental Validation of a Single Stage Thermocompressor for a Pneumatic Ankle-Foot Orthosis
Authors: Hofacker Mark E. , Kumar Nithin S. , Barth Eric J.
Published: February 2014

The mechanical design, modeling, and partial experimental validation of a prototype Stirling thermocompressor is presented in this paper. The thermocompressor is intended to serve as a compact and quiet, untethered 50 W, pneumatic power supply for an ankle foot orthosis. The goal of high efficiency at the target power density is pursued through the use of novel heat exchangers and high operating temperature and frequency. The motion of the displacer piston is controlled utilizing a brushless DC motor driving a continuous linear reciprocating screw. This paper presents the experimental validation of the heat transfer and pressure dynamics portions of the thermocompressor, leaving the modeling and validation of mass transfer to future work.
Use Natrium-Alkali Method to Remove SO2 From Shipping Exhaust Gas
Authors: Liu Diantao , Zhou Song , Zhu Yuanqing
Published: February 2014

In recent years, the purification of sulfur oxides in shipping exhaust is becoming the focus of attention. It is especially important about how to accurately determine and control the various factors affecting desulfurization efficiency. This paper built a mathematical model, mainly focusing on action and mass transfer characteristic of gas-liquid absorption progress of natrium-alkali desulphurization system. It is based on gas-liquid complicated reactions of packed absorption tower, obtaining the influence of concentration distribution of various components in liquid phase, as well as partial pressure, pH value, mass transfer rate, absorption enhancement factor, liquid gas ratio and other key parameters on SO2 absorption rate. As shown in the models, the removal efficiency of 97.8% is equivalent to use a sulfur content of 3.5% fuel oil under the restrictions in emission control area. According to the calculation of 4.0 MW diesel engines, the minimum supply rate of absorption liquid is 75.8 L/h. These data have the reference significance for the development and evaluation of shipping flue gas desulfurization systems.
A Research on Engine Phase and Speed Estimation Method Based on Cylinder Pressure Sensor
Authors: Wang Jinli , Yang Fuyuan , Ouyang Minggao , Huang Ying
Published: February 2014

Cylinder pressure based combustion state control is a direction that has drawn much attention in the field of internal combustion engine control, especially in the field of diesel HCCI (Homogeneous Charge Compression Ignition) research. In-cylinder pressure sensors have the potential to diagnose or even replace many traditional sensors, including camshaft and crankshaft sensors. This paper did research on engine synchronization method based on in-cylinder pressure signal. The research was based on a 4-cylinder high pressure common rail diesel engine equipped with 4 PSG (Pressure Sensor Glow Plug) type piezo-resistance cylinder pressure sensors, intended for HCCI research. Through theoretical analysis and experimental proof, methods and models for cylinder identification, engine phase estimation and engine speed estimation are given and further verified by experiments. Results show that cylinder pressure sensor could be used to identify cylinder instead of cam shaft sensor. The models for engine phase and speed estimation have been proved to have precision of 3° crank angle and 4.6rpm, respectively. The precision of engine phase and speed estimation provides a possibility for the engine to run if the crankshaft sensor fails, but more researches have to be carried out with respect to crankshaft sensor replacement.
Calculation of Laminar Flame Speed and Autoignition Delay at High Temperature and Pressures
Authors: Xu Hui , LaPointe Leon A.
Published: February 2014

Recent developments in emissions regulations, costs of conventional fuels, and new gas extraction drilling technologies have resulted in an increased emphasis in gaseous fueled spark ignited engine development. However the composition of gaseous fuels can vary greatly. Homogenous Charge Spark Ignited (HCSI) engine performance is heavily dependent upon fuel properties, and robust engine design to utilize gaseous fuels must accommodate these fuel property variances. Accurate prediction of fuel energy release characteristics and knock tendency is critical in the process of HCSI engine development.

Combustion characteristics, such as Laminar Flame Speed (LFS) and Autoignition Interval (AI), are used to characterize performance of various gaseous fuels in HCSI engine applications. Combustion duration is related to the LFS. The likelihood of Knock is related to the AI. Overall engine performance is estimated by appropriately incorporating these parameters into cycle simulation software.

Experimental data of LFS is often at low temperature and low pressure and thus does not represent the high temperature and pressure conditions typically prevalent in HCSI engine combustion chambers at the time of ignition. Lack of reliable LFS data at high temperature and pressures represents a major opportunity of development for better engine performance simulations [1].

In this paper, the commercially available chemical kinetics solver Chemkin Pro using an appropriate mechanism was employed to compute LFS and AI at typical HCSI engine in-cylinder conditions.

It is challenging to compute LFS at such extreme conditions mainly because of autoignition as a competing process.

This paper describes development of a robust methodology to compute LFS over a wide range of Temperature (up to 1300 K), Pressure (up to 250 bar), Relative Humidity, and Lambda for Methane. A regression for LFS with Pressure, Temperature, Lambda, and Relative Humidity as independent variables was generated for Methane. Methodology robustness was suggested with similar LFS calculations using other fuels. The form of the regression is similar for all of the fuels investigated.
Research on TITO Coupling Control Strategy for Parallel Hybrid Excavator
Authors: Du Lei , Yang Fuyuan , Xu Liangfei , Ouyang Minggao
Published: February 2014

The hybridization and electrification of powertrains gain increasing popularity in recent years, especially in the field of construction machine. In this paper, a TITO (Two-input Two-Output) coupling control strategy for parallel hybrid excavator is studied. First, the structure and configuration of the parallel hybrid powertrain are introduced. Then, a TITO coupling control strategy is presented. Engine speed and SOC (State of Charge) of super capacitor are controlled by engine torque and ISG torque together. Whereafter, the model of powertrain and control strategy is built in Matlab/Simulink. Then, networked control system for parallel hybrid excavator is introduced. Finally, the control strategy is optimized and validated by field tests. The results show that the operating region is close to the high efficiency working point and SOC of super capacitor maintains within 50% and 70%. Compared with conventional hydraulic excavator, a 15% reduction in fuel consumption is achieved.
Fully Nitrided Valves for Medium and Heavy Duty Engines
Authors: Lerman Pedro , Ruch Roland , Almeida Rómulo
Published: February 2014

For certain applications in the world of internal combustion engines (ICE), it has been found that nitrided valves have a better performance against wear than those which are seat hard faced and chrome plated. This alternative has not been significantly explored in the Medium Duty (MD) and Heavy Duty (HD) markets.

Fully nitrided MD/HD valves, mostly hard faceless, would be less expensive than chromed ones. They may become a cost effective product with better tribological performance, higher fatigue strength and improved resistance to thermal shock. In addition to this, a proper selection of the counterpart materials, those of the valve seat insert (VSI) and the valve guide (VG) will have a synergetic effect on the valve set performance, also leading to its cost improvement.

Not less important is the replacement of the well-known salt bath nitriding by the gas nitriding technique, an environmentally friendly process that maintains valve performance with the advantage of employing a lower nitriding temperature providing a higher tip end and seat hardness combined with a lower distortion level in the final product.

The aim of this work is to present the development and introduction of fully nitrided valves as a reliable solution for nowadays MD/HD applications. It is based on a deep process and product validation including the development of the gas nitriding process, wear, fatigue and engine tests.
A Linear Least-Squares Algorithm for Double-Wiebe Functions Applied to Spark-Assisted Compression Ignition
Authors: Hellström Erik , Stefanopoulou Anna , Jiang Li
Published: February 2014

An algorithm for determining the four tuning parameters in a double-Wiebe description of the combustion process in spark-assisted compression ignition engines is presented where the novelty is that the tuning problem is posed as a weighted linear least-squares problem. The approach is applied and shown to describe well an extensive data set from a light-duty gasoline engine for various engine speeds and loads. Correlations are suggested for the four parameters based on the results, which illustrates how the double-Wiebe approach can also be utilized in predictive simulation. The effectiveness of the methodology is quantified by the accuracy for describing and predicting the heat release rate as well as predicting the cylinder pressure. The root-mean square errors between the measured and predicted cylinder pressures are 1 bar or less, which corresponds to 2% or less of the peak cylinder pressure.
An Experimental Study of the Vaporization Characteristics of Diesel-Benzyl Azides Blend Droplets
Authors: Han Kai , Fu Geng , Zhao Changlu , Liu Bolan , Ma Shibo
Published: February 2014

An experimental study of diesel-benzyl azides blend droplets vaporization characteristics was carried out to study the reasons of diesel-benzyl azides blend shortened combustion duration using suspended droplet device and a high-speed video camera. Experiments were performed at atmospheric pressure, ambient temperature range 480–933 K, and initial droplet diameter of 0.98, 1.42, 1.88 mm. The results show a shorten in diesel-benzyl azides blend droplet lifetime by 10% compared to diesel droplet at 1.42 mm initial droplet diameter and 933 K ambient temperature companion to puffing. The above results support the original idea of designing diesel-benzyl azides blend where the energy released by the decomposition of azides improves the vaporization and the release of nitrogen leads to the breakup of the droplet. In addition, it is observed that the blend lifetime decrease with increasing ambient temperature compared to diesel droplet lifetime. More nitrogen is released and the expansion of bubbles is more violent with increasing initial droplet diameter.
High-Performance Lead-Free Electroplated Composite Bearing Overlay for Heavy Duty Applications
Authors: Gorges Roger , Brock Ronald
Published: February 2014

Material selection for engine internal components, e.g. bearings, is becoming increasingly more complex and demanding as the operating environments become more aggressive with the introduction of new technologies for the reduction of CO2 emissions. Historically, engine bearings contained lead, which has excellent fundamental bearing properties such as compatibility (run satisfactorily under conditions of marginal lubrication), conformability (deform and accept small scale geometrical inaccuracies of the crankshaft), and embeddablity (tolerance to dirt and other foreign materials) whilst being readily alloyed to achieve good wear and fatigue resistance. However, facing new challenges, many Original Equipment Manufacturers have started development programs to replace lead-containing with lead-free engine components in order to comply with new end-of-life vehicle directives or anticipated future directives. For more than fifteen years, MAHLE has been successfully supplying the light, medium and heavy duty market, with premium electroplated leaded composite bearings, which are designed to improve wear resistance. Some of this market now demands a switch to lead-free materials, while maintaining or exceeding its aforementioned requirements on bearing material properties. Composites of hard particles in a softer metal matrix are in this context ideally suited bearing materials as they can be tailored to obtain the optimal mix between soft and hard properties for the individual application. Typical hard particles that are commonly used comprise of metal oxides, nitrides or carbides.

In addition to higher load carrying capabilities and longer service life, new engine technology trends demand that bearings also must operate under mixed or boundary lubrication conditions without having any adverse effect on the performance and integrity of the engine system. Boundary lubrication is commonly observed upon starting the engine before the elastohydrodynamic oil film is fully established. In this state, load is carried by surface asperities rather than by the lubricant. So far, the incorporation and even distribution of the hard particles into an electroplated lead-free matrix was not achievable using conventional direct current electroplating techniques. MAHLE, therefore, has developed a patented pulse plating technique in order to incorporate hard particles into the overlay metal matrix. The refined and modified crystal structure of the resulting lead-free overlay, with incorporated hard particles, yields a premium electroplated bearing with superior wear and fatigue resistance. Corresponding rig and engine test results have been completed to support the material development.
NOx Emissions Characterization During Transient Spark Assisted Compression Ignition (SACI) Engine Operation
Authors: Lin Weiyang , Sterniak Jeff , Bohac Stanislav V.
Published: February 2014

In the quest for high efficiency IC engine operation, spark assisted compression ignition (SACI) can fill the gap between homogeneous charge compression ignition (HCCI) operation at low load and spark ignited (SI) operation at high load. SACI combustion utilizes a combination of flame propagation and auto-ignition to achieve ignition when unburned temperatures are too low for reliable auto-ignition and the mixture is too dilute for flame propagation with sufficient speed. Stoichiometric SACI combustion with cooled external exhaust gas recirculation (EGR) offers improved thermal efficiency compared to stoichiometric SI operation. It also reduces combustion temperatures and therefore NOx emissions, while still allowing for the use of a three-way catalyst (TWC).

This study investigates NOx spikes that can occur during transitions between different SACI operating points as a result of system time lags or mixture deviation from stoichiometry. Load transitions at various stoichiometric SACI operating points are investigated and NOx emissions before and after the TWC are reported. Significant engine-out NOx spikes are observed. A 1200 ppm NOx spike occurs during a load increase from 3 to 6 bar BMEP at 1800 rpm in 2 cycles (0.13 seconds), which is representative of a faster load change in the FTP-75 drive cycle. Observed NOx spikes are attributed to a time lag in external EGR during the transitions. NOx emissions after the TWC are reduced to below 50 ppm, indicating that NOx emissions during these transients can be handled effectively by a TWC.
Numerical Study on Radiation Heat Transfer in Diesel Engine With 3D Unstructured Finite Volume Method
Authors: Ming Pingjian , Jiao Yafei , Liu Yongfeng , Fu Lirong , Liu Gongmin , Zhang Xinyu
Published: February 2014

In this paper, a numerical method based on finite volume method for diesel engine is presented. The production of combustion is assumed to be a grey medium and the scatter of particle is neglected. In this paper the unstructured finite-volume method (UFVM) for radiation has been formulated and implemented in an in-house fluid flow solver GTEA. For its comparison and validation of the present FVM on unstructured grids, a test case with 3D complex geometries is chosen, which was used by S. W. Baek et.al.[1]. The results obtained by the presented FVM agree well with the exact solutions. Radiation heat transfer in TBD620 diesel engines is studied with present numerical method. It is shown that the radiation has little effect on average pressure and temperature, but it changes the temperature distribution in cylinder.
Performance and Emissions Characteristics of Diesel-Ignited Gasoline Dual Fuel Combustion in a Single Cylinder Research Engine
Authors: Dwivedi U. , Carpenter C. D. , Guerry E. S. , Polk A. C. , Krishnan S. R. , Srinivasan K. K.
Published: February 2014

Diesel-ignited gasoline dual fuel combustion experiments were performed in a single-cylinder research engine (SCRE), outfitted with a common-rail diesel injection system and a stand-alone engine controller. Gasoline was injected in the intake port using a port-fuel injector. The engine was operated at a constant speed of 1500 rev/min, a constant load of 5.2 bar IMEP, and a constant gasoline energy substitution of 80%. Parameters such as diesel injection timing (SOI), diesel injection pressure, and boost pressure were varied to quantify their impact on engine performance and engine-out ISNOx, ISHC, ISCO, and smoke emissions. Advancing SOI from 30 DBTDC to 60 DBTDC reduced ISNOx from 14 g/kWhr to less than 0.1 g/kWhr; further advancement of SOI did not yield significant ISNOx reduction. A fundamental change was observed from heterogeneous combustion at 30 DBTDC to “premixed enough” combustion at 50–80 DBTDC and finally to well-mixed diesel-assisted gasoline HCCI-like combustion at 170 DBTDC. Smoke emissions were less than 0.1 FSN at all SOIs, while ISHC and ISCO were in the range of 8–20 g/kWhr, with the earliest SOIs yielding very high values. Indicated fuel conversion efficiencies were ∼ 40–42.5%. An injection pressure sweep from 200 to 1300 bar at 50 DBTDC SOI and 1.5 bar intake boost showed that very low injection pressures lead to more heterogeneous combustion and higher ISNOx and ISCO emissions, while smoke and ISHC emissions remained unaffected. A boost pressure sweep from 1.1 to 1.8 bar at 50 DBTDC SOI and 500 bar rail pressure showed very rapid combustion for the lowest boost conditions, leading to high pressure rise rates, higher ISNOx emissions, and lower ISCO emissions, while smoke and ISHC emissions remained unaffected by boost pressure variations.
Combustion Noise Investigation With Multi-Cylinder RCCI
Authors: Curran Scott J. , Szybist James P. , Wagner Robert M.
Published: February 2014

Advanced combustion techniques have shown promise for achieving high thermal efficiency with simultaneous reductions in oxides of nitrogen (NOx) and particulate matter (PM) emissions. Many advanced combustion studies have used some form of noise-related metric to constrain engine operation, whether it be cylinder pressure rise rate, combustion noise, or ringing intensity. As the development of advanced combustion techniques progresses towards production-viable concepts, combustion noise is anticipated to be of the upmost concern for consumer acceptability. This study compares the noise metrics of cylinder pressure rise rate with combustion noise as measured by an AVL combustion noise meter over a wide range of engine operation conditions with reactivity controlled compression ignition on a light-duty multi-cylinder diesel engine modified to allow for direct injection of diesel fuel and port fuel injection of gasoline. Key parameters affecting noise metrics are engine load, speed, and the amount of boost. The trade-offs between high efficiency, low NOX emissions, and combustion noise were also explored. Additionally, the combustion noise algorithm integrated into the Drivven combustion analysis toolkit is compared to cylinder pressure rise rate and combustion noise as measured with a combustion noise meter. It is shown that the combustion noise of the multi-cylinder reactivity controlled compression ignition map can approach 100 dB while keeping the maximum pressure rise under 100 kPa/CAD.
Diesel Engine Combustion Sensing Methodology Based on Vibration Analysis
Authors: Ponti F. , Ravaglioli V. , Cavina N. , De Cesare M.
Published: February 2014

The increasing request for pollutant emissions reduction spawned a great deal of research in the field of combustion control and monitoring. As a matter of fact, newly developed low temperature combustion strategies for Diesel engines allow obtaining a significant reduction both in particulate matter and NOx emissions, combining the use of high EGR rates with a proper injection strategy. Unfortunately, due to their nature, these innovative combustion strategies are very sensitive to in-cylinder thermal conditions. Therefore, in order to obtain a stable combustion, a closed-loop combustion control methodology is needed.

Many works demonstrate that a closed-loop combustion control strategy can be based on real-time analysis of in-cylinder pressure trace, that provides important information about the combustion process, such as start of combustion, center of combustion and torque delivered by each cylinder. Nevertheless, cylinder pressure sensors on-board installation is still uncommon, due to problems related to unsatisfactory measurement long term reliability and cost.

This paper presents a newly developed approach that allows extracting information about combustion effectiveness through the analysis of engine vibrations. In particular, the developed methodology can be used to obtain an accurate estimation of the indicated quantities of interest combining the information provided by engine speed fluctuations measurement and by the signals coming from acceleration transducers mounted on the engine.

This paper also reports the results obtained applying the whole methodology to a light-duty turbocharged Common Rail Diesel engine.
Reduction of GHGs Emissions in a Biodiesel Fueled Diesel Engine Using Hydrogen
Authors: Subramanian K. A. , Chintala Venkateswarlu
Published: February 2014

The experimental tests were conducted on a 7.4 kW rated diesel engine fueled with biodiesel-diesel blend (B20) for quantitative evaluation of greenhouse gases (GHGs) emissions. The result indicates that carbon dioxide (CO2) emission did not change significantly with B20 whereas methane (CH4) and nitrous oxide (N2O) emissions with B20 decreased marginally as compared to base diesel. In order to reduce further these emissions, the effect of hydrogen (H2: 20% energy share) on GHGs emissions in the biodiesel (B20) fueled diesel engine under dual fuel mode is assessed. CO2 emission decreased drastically with H2 due to higher thermal efficiency and lesser carbon content of the fuels than base diesel and B20 whereas CH4 and N2O emissions decreased significantly due to high temperature combustion. At rated load, CO2, CH4 and N2O emissions of the engine decreased about 46%, 22% and 27% respectively with biodiesel (B20)-H2 (20% energy share) under dual fuel mode as compared to conventional base B20 mode. A conclusion is clearly emerged from this study that the formation of CH4 and N2O emissions are dependent on in-cylinder pressure and temperature. Hydrogen addition to the diesel engine is an effective solution to reduce CO2 along with CH4 and N2O emissions.
Model and Calibration of a Diesel Engine Air Path With an Asymmetric Twin Scroll Turbine
Authors: Hand Mike J. , Hellström Erik , Kim Doohyun , Stefanopoulou Anna , Kollien Justin , Savonen Craig
Published: February 2014

A control-oriented model and its associated tuning methodology is presented for the air path of a six cylinder 13 L diesel engine equipped with an asymmetric twin-scroll turbine, wastegate (WG), and exhaust gas recirculation (EGR). This model is validated against experimental engine data and shows good agreement. The small scroll of the asymmetric twin scroll turbine is fed by the exhaust of three cylinders via a split manifold that operates at higher pressure than the exhaust manifold feeding the larger turbine scroll. The asymmetric design with the high exhaust back pressure on three of the six cylinders gives the necessary EGR capability, with reduced pumping work, but leads to complex flow characteristics. The mean-value model describes the flows through the engine, the flow through the two turbine scrolls, the EGR flow, and the WG flow as they are defined, and defines the pressure of the manifolds they connect to. Using seven states that capture the dynamics of the pressure and composition in the manifolds and the speed of the turbo shaft, the model can be used for transient control, along with set point optimization for the EGR and WG flows for each speed and load condition. The relatively low order of the model makes it amenable to fast simulations, system analysis, and control design.
Modern Design Methods Applied to the Redesign of a Legacy Large Bore, Two-Stroke Cycle, Spark Ignited Gas Engine
Authors: Etcheverry John , Patterson Mark , Grauer Diana
Published: February 2014

Large bore, spark ignited, reciprocating, gas engines have been the workhorse of the pipeline industry for many years when it comes to transmission of gas. Recently, the US government has released an update to the NSPS and RICE NESHAP regulating emissions from many of these engines to [1]:

• 1gbhp·hgbhp-hrNOX

• 2gbhp·hCO

• 0.7gbhp·hVOCs (Non-methane, non-ethane hydrocarbons)

This new rule leaves many of these legacy engines out of compliance with the standard. Because of this, engine operators are left with the choice of decommissioning these engines as they come due for compliance based retrofit or working with engine OEMs to implement an emissions reduction strategy.

For many years, the traditional methods and tools used for engine design were more than enough to create a successful engine. But with tightening restrictions and higher expectations for customers and the amount of improvement that can be extracted from design changes shrinking with every redesign, these methods by themselves are no longer sufficient. This paper will examine modern design methods and tools available to an engine designer as well as their integration with more traditional testing methods. A comparison of results for the redesigned COOPER BESSEMER® GMVH-6C3 will also be presented for analysis.
Performance and Emission Characteristics of a Medium Capacity Compression Ignition Engine Fuelled With Mahua Biodiesel Employing Cold EGR
Authors: Gupta Sahil , Kumar Naveen , Gupta Dhruv , Vaidyanathan Manish
Published: February 2014

Oil provides energy for 95% of transportation and the demand of transport fuel continues to rise. According to the assessment of IPCC (International Panel on Climate Change) to climate change, global oil demand will rise by 60% from 75 Mb/d in 2000 to 120 Mb/d in 2030. All countries including India are grappling with the problem of meeting the ever increasing demand of transport fuel with the constraints of international commitments, legal requirements, environmental concerns, and limited resources. Hence, search for renewable fuels is becoming more and more prominent for ensuring energy security and environmental protection. This has renewed the interest of scientific community to look for alternative fuels of bio-origin which can provide a feasible environmental friendly solution with improved performance characteristics. Biodiesel is produced by a chemical process known as transesterification, by which the triglycerides are reacted with alcohols, in the presence of a catalyst, to produce fatty acid alkyl esters. For quite some time focus for production of biodiesel has shifted towards non-edible oil feedstock from the edible ones, mostly due to food security issues. One such non-edible oil, locally known as Mahua in Indian subcontinent, may be evaluated as a potential feed stock for biodiesel production. The fuel properties were found to be comparable with that of diesel fuel. In the present study, mineral diesel fuel along with 20% (v/v %) blend of Mahua oil methyl ester (MOME) was prepared for conducting experiments and the performance and emission characteristics was investigated at 5%, 10%, 15% and 20% exhaust gas recirculation (EGR) rates. Major observations drawn from the exhaustive experiments is that the brake thermal efficiency (BTE) for M20 increased in comparison to diesel baseline whereas on employing cold EGR, BTE abridged with the increase in EGR rate. Unburned Hydrocarbon and Carbon monoxide emissions as well as Smoke Opacity upsurge with increase in EGR percentage. However, a considerable decline in NOx was obtained at higher EGR levels.