bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effects of Foam Density and Metal Velocity on the Heat and Mass Transfer in the Lost Foam Casting Process
Authors: Liu X. J. , Bhavnani S. H. , Overfelt R. A.
Published: December 2008

As an innovative technique, the lost foam casting (LFC) process has drawn great attention from both academia and industry in recent years. The key feature of LFC process is that a desired shape pattern made of expandable polystyrene (EPS) foam is buried in unbonded sand and replaced by advancing molten metal. The heat and mass transfer between the molten metal front and the EPS foam pattern plays an important role in the soundness of the product in the LFC process. The present study focuses on determining the characterization of heat and mass transfer during the EPS pattern degradation process. A unique experimental system using a cylindrical quartz window and heated steel block simulating the hot molten metal front has been constructed to make measurements and visualize the process. The foam pattern is 88 mm in diameter and 254 mm long. It is coated twice with DCH Ashland refractory material and the average coating thickness is 1.2 mm. The heat flux and pressure between the moving steel block and the EPS pattern are measured. The process variables studied during this experiment include foam density and steel block speed. It was found that unlike the fluidity of the molten metal which is highly dependent on the density of the foam patterns, foam density has marginal effect on the heat flux from the steel block to the foam pattern. The heat flux increases about 37% during a one-minute process under steel block velocity of 4.4 mm/s using different EPS foam density of 24 kg/m3 and 27 kg/m3. Flow visualization shows a gaseous gap formed between the steel block and the foam pattern. The phase change and degradation of EPS foam pattern and the heat and mass transfer in the gap are crucial to characterize the mold filling process which decides the quality of casting products. The maximum pressures measured in the gap using steel block velocity of 4.4 mm/s are 1.1 kPa and 1.4 kPa for EPS foam density of 24 kg/m3 and 27 kg/m3, respectively. Under a slower steel block velocity of 3.6 mm/s the gap peak pressure using 24 kg/m3 density EPS foam pattern is 0.43 kPa. It is concluded that higher foam density and faster steel block speed give rise to larger gas pressure between the steel block and foam pattern. The measured pressure values confirm data reported in literature.
A Numerical Study of Microwave Thermotherapy for Benign Prostatic Hyperplasia
Authors: Thamire Chandrasekhar , Bellary Sharath
Published: December 2008

Transurethral resection of the prostate is the conventional therapy used for relieving bladder-outflow obstruction that typically occurs in older men due to benign prostatic hyperplasia (BPH). Due to the complications and side effects involved, other therapies that are less invasive have been in use over the last few years. The current study examines one such therapy, namely, the transurethral thermal therapy, and its effectiveness as a treatment modality for BPH. The system considered here is capable of delivering microwave energy preferentially into the prostatic tissue. The heat generated inductively increases the temperature of the tissue to well above 40°C and causes necrosis when applied for adequate times. As both heating times and temperatures dictate the process, a transient analysis of the Pennes bio-heat transfer equation was performed for applicable parameter values. Based on the calculated temperature distributions, necrosis zones are estimated using the existing cell-death data and possible heating protocols are suggested.
The Discrete Wavelets Solution for a Steady Two-Dimensional Radiation With Heat Generation
Authors: Guven Oguzhan , Bayazitoglu Yildiz
Published: December 2008

The wavelet expansion is used in order to evaluate the angular dependence of the intensity in the solution of the radiation transfer equation (RTE). The radiation intensity is expanded in terms of orthogonal Daubechies’ wavelet basis in the angular domain. This method is applied to a steady two-dimensional rectangular enclosure containing a homogenous, absorbing, emitting and non-scattering medium with uniform heat generation cold black walls. The nondimensionalized emissive power and the nondimensional heat flux results for various optical depths are given and compared with the DOIM and zonal method solutions.
Theoretical Analysis of Flame Propagation in Meso and Microscale Channels
Authors: Ju Yiguang
Published: December 2008

Extinction and flame propagation in a meso and microscale channels are investigated analytically. Emphasis was paid to the coupling of wall heat loss, wall preheating, external heat loss and chemical reaction. The results showed that, wall thermal properties, channel width and flow velocity have dramatic effects on the flame propagation and lead to multiple flame regimes and extinction limits. With the decrease of channel width, flame reaches its first quenching limit, the so called critical quenching distance. However, with a further decrease of channel width, the results show that there exists a slow burning flame. With the increase of wall heat loss the speed of the slow burning flame slightly decreases and eventually reaches its second burning limit. With the change of the flow velocity, the results show that sub-limit flame can only exist at flow velocity larger than a critical value. At moderate flow velocity, flame speed increases with the increase of flow speed. At very large flow velocity, flame will be blown off. The above results are confirmed from the recent experimental data.
Diode-Laser-Based Sensor Measurements of Nitric Oxide and Carbon Monoxide in Combustion Exhaust Streams
Authors: Anderson Thomas N. , Barron-Jimenez Rodolfo , Caton Jerald A. , Lucht Robert P. , Roy Sukesh , Brown Michael S. , Gord James R. , Walther Thomas , Critchley Ian , Flamand Luis
Published: December 2008

All-solid-state continuous-wave (cw) laser systems for ultraviolet (UV) absorption measurements of the nitric oxide (NO) molecule and mid-infrared (IR) absorption measurements of carbon monoxide (CO) were developed and demonstrated. For the NO sensor, 250 nW of tunable cw UV radiation at 226.8 nm is produced by sum-frequency-mixing in a beta-barium borate crystal. For the CO sensor, 2μW of tunable cw IR radiation at 4.5 μm is produced by difference-frequency mixing in a periodically-poled lithium niobate crystal. A tunable external-cavity diode laser (ECDL) provides one of the fundamental beams for both processes so that the wavelength of the generated UV/IR can be tuned over NO/CO absorption lines to produce a fully resolved absorption spectrum. The sensors were used for measurements in the exhaust stream of an operating auxiliary power unit (APU) gas turbine engine and a well-stirred reactor (WSR). During these tests, NO was measured in the exhaust at levels below 10 ppm. For measurements at levels above 20 ppm, the NO emission levels obtained using the new sensor agreed with the results of probe sampling chemiluminescent analyzer results to within 10%. A detection limit of 0.8 ppm of per meter path length at 1000 K is estimated for the NO sensor. Measurements with the CO sensor demonstrated an agreement with extractive probe sampling to within 15%. The estimated detection limit of the CO sensor is a few ppm per meter path length at 1000 K.
The Effects of Wind on Liquid Fuelled Pool Fires
Authors: Weckman Elizabeth J. , Lam Cecilia S. , Weisinger Jennifer E. , Gill Walter , Brown Alexander L.
Published: December 2008

Macroscopic fire parameters such as fuel regression rate, flame height and flame tilt are critical to the development of detailed fire models and empirical tools for hazard analysis [1–3]. As a result, these characteristics have been investigated by many researchers using various measurement methods in studies of liquid fuelled pool fires of different diameters and fuel types, under a range of crosswind conditions. In investigations related to transportation accidents, fire scenarios have been complicated further through interactions between the fire and upwind or downwind objects [1,2]. Of particular interest is the determination of fuel regression rate, an important parameter but one that is generally difficult to characterize accurately. Many techniques have been reported for measurement of fuel regression rate. These include load cells [2,4,5], differential pressure systems [2,5–7], sight glass and float-type level meters [6–8] and thermocouple rakes [1]. In general, load cells have been employed most successfully for measurements in smaller scale fires [2,4], while researchers have turned to differential pressure and thermocouple type systems for measurements in fires above 5 m diameter [2,6,7]. All the techniques have been used with varying levels of success to measure fuel regression rate under quiescent conditions. Under crosswind conditions and in cases with an object present, however, inherent wandering of the fire plume and dynamic wind loading on the pool can be of additional concern as they affect the accuracy and repeatability of the measurements [1,2,6,7]. In several excellent reviews, available results have been summarized and used to derive empirical correlations relating overall fire characteristics to fire diameter, fuel type and/or wind velocity [3,9–11].
Transient Heat Transfer Processes in Batch Furnaces
Authors: Senarega Maurizio , Tagliafico Luca A.
Published: December 2008

The present paper describes a numerical model, based on a finite-difference technique, to simulate 2D thermal transients of solid and hollow cylinders in convective and radiant rectangular cavities, with participating media and time-dependent temperature-of-internal-gases. The model takes into account all the thermo-physical property variations with temperature of both gases and materials under treatment. These last are subject to strong non-linear convective-radiative thermal boundary conditions and undergo the needed solid-solid thermodynamic transitions. The study of the whole system includes the problem of conduction inside the multilayer furnace walls, solved by a 1D transient numerical model. The proposed model has been validated with respect to a numerical solution as well as to available full-scale experimental data. In particular a simplified radiation case is carried out comparing the solution obtained by the model to that given by a finite element commercial code (ANSYS®). The calculated temperature curves have been compared with experimental measurements too, with reference to few particular points in a cylinder inside a batch furnace, during an actual heat treatment. The 2D finite difference model results to be an efficient tool for predicting the system thermal performance, well suitable for design and operating conditions optimization.
Analysis of Flow and Heat Transfer at a Finned Tube in Crossflow
Authors: Rangan Bharat K. , Krishnamurthy Adarsh , Raghavan Vijay R.
Published: December 2008

In the present study, a numerical investigation has been carried out into the fundamental problem of airflow past and heat transfer from a circular finned cylindrical tube, placed in a duct. The simulation is carried out using a finite volume method, based on laminar calculation of the transport quantities and employs an unsteady, 3-D, second order upwind scheme. As the work has importance in applications of air-cooled heat exchangers, practical values have been chosen for air velocity, air temperature, fin spacing and clearance between fin outer diameter and duct wall. In experimental determination of the performance of a finned-tube bundle, only overall average values such as drag coefficient and overall Nusselt number are possible. Local measurements are well nigh impossible, as any measurement instrument introduced into the narrow fin space will immediately change the flow field. This work gives an insight into variations of shear and heat transfer that will help the designer to optimize the fin spacing. The validity of the results for instantaneous velocity profiles and Nusselt number distribution comes from their physical plausibility. The agreement of the logical behavior of the studied variables when the fin space or fin clearance is modeled confirms the adequacy of the numerical simulation. The strong viscous effects caused by decreasing the fin space result in an increase in Cd and change in its frequency. Vortices generated on the rear section of the tube are damped, but the flow still shows small oscillations downstream of the tube, which indicates that vortex generation still exists, but has changed its location. Vortices augment the Nusselt number locally with increasing fin distance. Simultaneously, the opposite effect of converging boundary layers and therefore accelerated core flow in the fin space yields a maximum in the average Nusselt number as a function of fin space. The impact of decrease in the clearance between the tube and the duct wall is not as important as the effects of fin space.
De Novo VOC From Regenerative Thermal Oxidizers
Authors: Martin Richard J. , Colwell Jeff D.
Published: December 2008

Regenerative thermal oxidizers are used extensively for the abatement of volatile organic compound (VOC) emissions from process vent streams. Due to the unique heat storage and convection properties of the ceramic packing utilized, they are especially well suited for applications with high flows and dilute concentrations of organic vapors. However, packed-bed devices such as these are known to be vulnerable to interstitial plugging when processing vent streams that contain particulate matter in addition to the VOC. In this paper, the authors postulate a new failure mode that involves relatively small concentrations of organic solids in the vent stream, and that may lead to serious performance deficiencies long before interstitial plugging becomes problematic. Specifically, we assert that “De Novo VOC” can be generated from organic particulate matter that adheres temporarily to the bed and is revaporized when the flow is reversed, causing a significant decrease in the apparent destruction efficiency of the abatement device. In this theoretical treatment, the spatial and temporal response of a hypothetical thermal bed is compared against the phase-change and combustion characteristics of a common organic solid, in order to estimate particle loading levels that may pose immediate compliance problems for users of these systems. Although experimental data are not available to corroborate the conclusions reached herein, the authors contend that routine carryover of small amounts of organic particles from a collection device (e.g., baghouse) to the thermal destruction system can create high exhaust VOC levels, and may eventually lead to hostile fires in the beds. As a means of mitigating against such failures, the authors recommend that an inlet particulate loading limit be implemented for all regenerative thermal oxidizer installations.
Effect of Moving Capillary Red Blood Cells on Alveolar Respiration
Authors: Merrikh A. A. , Lage J. L.
Published: December 2008

Researchers in the open literature have focused on developing methods to estimate the lung diffusing capacity (DL) both theoretically and experimentally because of the continuous interest in understanding the gas transfer phenomenon of respiration.
Cluster Dynamics for Multiscale Interactions
Authors: Tzou D. Y. , Chen J. K. , Roybal R. , Beraun J. E.
Published: December 2008

A cluster approach has been proposed to describe the process of heat transport in microscale. Molecular clustering is described by integrating the Lennard-Jones potential over specific physical domains, forming cluster potentials that possess repulsive and attractive forces sensitively varying with the geometrical shapes of the molecular clusters. The cluster potentials thus developed provides a consistent approach for describing multi-scale heat transport, in that different shapes/dimensions of the clusters take different exponents in the repulsive and attractive forces. A one-dimensional example is given to illustrate the essence of the cluster dynamics simulation, emphasizing devious behavior from molecular motion and replacement of physical boundaries by cluster potentials of a larger scale.
Thermal System Design and Dislocation Reduction for Growth of Wide Bandgap Crystals
Authors: Ma R.-H. , Zhang H. , Dudley M. , Prasad V.
Published: December 2008

In SiC vapor growth, micropipes and dislocations that originate at the seed/boule interface can continuously propagate into the newly grown crystal. They adversely affect the quality of the crystals. The defect density can be reduced by the method of growing a large diameter crystal from a small seed through lateral growth under controlled thermal environment. In this paper, SiC growth processes with varying thermal conditions have been simulated. The effects of operational parameters such as axial and radial temperature gradients, and the presence of polycrystal are also investigated. The current finding can also help in the design of AlN/GaN growth system.
Thermo-Fluid-Dynamic Diagnostics in Multiple-Intersection Flow Network Using IR Thermometry and DPIV
Authors: Ay Herchang , Chou Chih-Hao , Chen Bing-Yi
Published: December 2008

A multiple-intersecting flow network is common in biological and industrial systems such as the human vascular system, the internal coolant passage of turbine blade inside gas turbine engine, the liquid cooling channel inside electronic modules. An infrared thermovision system is used to map the detail local convective heat transfer coefficients for the multiple-intersection flow network consisting of a 30° intersection angle. In addition, a digital particle image velocimetry (DPIV) system had been developed to measure instantaneous and ensemble-averaged flow fields in the multiple-intersection flow networks. The flow at each intersection is characterizes by a collision of two flow streams, resulting in vortices on the two sides of the diamond-shaped pin in the post-intersecting region of the network. It is noticed that the vortex at one side increases, at the same time the vortex at the other side decreases with the flip-flop flow at the exit end of the flow network. The study also found the vortex ring places on interlacing surface of the downstream-half of the diamond-shaped pin between the two longitudinal rows. The complex flow patterns are found to play an important part in the local heat transfer performance. The main effort of the present study is attempt to interpret the DPIV measurement results to understand the detailed flow patterns inside the multiple-intersection flow networks and the heat transfer data using an infrared thermovision system.
Experimental Study of Leidenfrost Phenomena at Hot Sprayed Surface
Authors: Raudensky´ M. , Horsky´ J. , Dumek V. , Kotrba´cˇek P.
Published: December 2008

An experimental study was prepared to find the relationship between Leidenfrost temperature and droplet size and velocity of impinging jets. The study is done for the case of steel surface cooling with two-phase nozzles. The sprayed surface moves under the spray at a velocity of 1 m/min. Cooling experiments were done for initial temperature of 1250°C. Thermal experiments are transient: internal temperature is measured and surface temperature and heat transfer coefficient distribution is computed by the inverse task. Droplet size and velocity of the impinging jet was modified by setting water and air pressures at the input of the nozzle. Spray parameters for each pressure combination was measured using a laser-doppler anemometer. The paper shows the results of the thermal and fluid flow experiment and the correlation between Leidenfrost temperature and flow parameters.The application of obtained results is expected for high temperature cooling especially in continuous casting.
A Computational Fluid Dynamics (CFD) Analsysis of the Vacuum De-Zincing Process
Authors: Jalili V. , Bailey C. , Patel M. K.
Published: December 2008

This is a novel application of Computational Fluid Dynamics (CFD), in the vacuum De-zincing process. The complete modeling process would involve the solution of the following equations: a) Navier-Stokes Equations; b) The Energy Equation; c) The Solution of the Species Concentration. The aim of this research as a novel approach in vacuum Dezincing process has been to gain an understanding in terms of the actual complicated physics involved de-zincing process such, as phase change and solidification. The results in this paper have contributed to a better understanding of the vacuum De-zincing process, hence identifying parameters, which would aid the efficient recovery of the zinc from the molten metal bath.
Monte Carlo Simulation of In-Plane Phonon Transport in Porous Silicon Membranes
Authors: Song David , Chen Gang
Published: December 2008

The in-plane thermal conductivity of periodic microporous single-crystal silicon membranes is simulated using a Monte Carlo method in the temperature range from 50K to 300K. The study focuses on the effect of pore boundary scattering. A gray body phonon transport is simulated, using a set of average phonon properties derived from the published experimental phonon dispersion curves. The simulation was first performed for bulk Si and the result is compared to the published experimental values. Porous Si membranes corresponding to our previous experimental configurations were then examined.
A Numerical and Experimental Study of Heat and Moisture Transfer With Phase Change and Mobile Condensates in Fibrous Insulation
Authors: Fan Jintu , Cheng Xiaoyin
Published: December 2008

This paper reports on an improved model of coupled heat and moisture transfer with phase change and mobile condensates in fibrous insulation. The new model considered the moisture movement induced by the partial water vapor pressure, a super saturation state in condensing region as well as the dynamic moisture absorption of fibrous materials and the movement of liquid condensates. The results of the new model were compared and found in good agreement with the experimental ones. Numerical simulation was carried using the model to investigate the effect of various material parameters on the transport phenomena.
Exhaust Gas Driven Generator With Altitude Compensation for Battery Dominant Hybrid Electric Vehicles
Authors: Darlington Thomas E. , Frank Andrew A.
Published: December 2008

HEVs historically have had reduced performance at elevations higher than sea level. The effects of this loss of performance can be mediated with the use of a standard turbocharger; however, approximately 80–90% of the vehicle’s operation is at altitudes where full boost from the turbocharger is not needed to maintain performance characteristics comparable to conventional vehicles of the same size. If the turbocharger is used to drive an electric generator, the power produced by the turbine section that is not needed to maintain the intake pressure at the set point, determined as the pressure at which the best ICE efficiency occurs, can be used to charge the traction battery of HEVs. The Exhaust Gas Driven Generator converts the thermal energy, normally wasted through the exhaust of the ICE, to electrical energy stored in the traction battery of the HEV. By recovering a portion of the heat energy of the exhausted combustion gases, the Exhaust Gas Driven Generator can improve the volumetric efficiency and effective thermal efficiency of the propulsion system of the HEV, thus reducing the fuel consumption of the typical HEV even further.
Analysis for Strain on Torsional Damper Rubber and Torsional Vibration on Crankshaft for a Diesel Engine
Authors: Kimura Jouji , Takayama Katsukimi
Published: December 2008

A torsional damper is attached to a crankshaft pulley to control torsional vibration. Torsional strain is produced on the rubber when it is placed between the damper plate and the damper ring. The authors know from our experience that, in some engines, especially in turbo-charged engines, such a significant degree of strain is produced on the damper rubber at a resonant engine speed that the rubber is torn off in two pieces. This paper presents a method of estimating strain caused by torsional vibrations and discusses the relationship between the crankshaft torsional vibration and the strain.
An Improved Model for SI Engines
Authors: Shamekhi Amir H. , Gaffari Ali
Published: December 2008

In this paper an improved mathematical model of spark ignition engines is presented. The model is derived based on a combination of thermodynamically relations and dynamical characteristics of engines. The geometrical parameters of the engine, valves and spark timing, air to fuel ratio, specific fuel consumption and engine operational conditions are considered during all four strokes of the engines. The engine is divided into some related subsystems namely; throttle body, intake manifold, fuel delivery system, intake and exhaust valves, E.G.R., torque production system, rotational dynamics and emission system. Each subsystem is modeled and the inter-relation between them has been considered. A new computer code is developed in Visual C++6 based on derived relations. This code may be considered as an appropriate means to investigate the performance of a given SI engine and to derive the emission results. The computer code is able to evaluate twelve combustion production species in a full thermodynamic equilibrium. Other engine performance quantities such as power, torque, thermal efficiency, work done by piston, pressure and temperature time histories are also evaluated in this simulation.
Ionic Current Simulation During the Post Flame Period in SI Engines
Authors: Shamekhi Amir H. , Gaffari Ali
Published: December 2008

The application of ion current signals is one of the most recent approaches in engine management systems. By applying a small constant DC voltage across the electrodes of the spark plug and measuring the current through the electrode gap, the state of gas may be measured and investigated. In this paper a computer code is developed in order to analyze the state of gas during the combustion period. It is shown that there is a strong correlation between the peak pressure position and the maximum current position. It is also shown that among all combustion products, the NO has the most contribution in generating electrical current. The two zones model is used for calculating the cylinder pressure and temperature.
Simulation of Extended Expansion Lean Burn Spark Ignition Engine
Authors: Manivannan A. , Ramprabhu R. , Tamilporai P. , Chandrasekaran S.
Published: December 2008

This paper deals with Numerical Study of 4-stoke, Single cylinder, Spark Ignition, Extended Expansion Lean Burn Engine. Engine processes are simulated using thermodynamic and global modeling techniques. In the simulation study following process are considered compression, combustion, and expansion. Sub-models are used to include effect due to gas exchange process, heat transfer and friction. Wiebe heat release formula was used to predict the cylinder pressure, which was used to find out the indicated work done. The heat transfer from the cylinder, friction and pumping losses also were taken into account to predict the brake mean effective pressure, brake thermal efficiency and brake specific fuel consumption. Extended Expansion Engine operates on Otto-Atkinson cycle. Late Intake Valve Closure (LIVC) technique is used to control the load. The Atkinson cycle has lager expansion ratio than compression ratio. This is achieved by increasing the geometric compression ratio and employing LIVC. Simulation result shows that there is an increase in thermal efficiency up to a certain limit of intake valve closure timing. Optimum performance is attained at 90 deg intake valve closure (IVC) timing further delaying the intake valve closure reduces the engine performance.
PIV Measurements of In-Cylinder Flow in a Four-Stroke Utility Engine and Correlation With Combustion Measurements
Authors: Bevan Karen E. , Ghandhi Jaal B.
Published: December 2008

Large-scale flows in internal combustion engines directly affect combustion duration and emissions production. The effect of intake port geometry on combustion performance was studied in a four-stroke spark-ignition utility engine. Three intake port geometries were investigated at three port orientations. In-cylinder flows in orthogonal planes were measured using particle image velocimetry (PIV). Combustion performance data were acquired at two load conditions and three equivalence ratios. The PIV data were processed to calculate the large-scale mean vorticity and mean high-pass filtered velocity. These flow parameters were used to characterize the in-cylinder flow in a measurement plane in a physically meaningful way and correlate the flow with combustion performance. The cumulative distribution functions of the flow parameters did not show significant port-to-port differences in either measurement plane. The mean vorticity and high-pass filtered velocity did exhibit differences due to port orientation in the horizontal plane, but not in the vertical plane. The 0-degree ports consistently produced the highest values of large-scale mean vorticity and mean high-pass filtered velocity in the horizontal plane. The kinetic energy present at ignition was also calculated to characterize the flow. The ensemble average values of the mean large-scale vorticity, high-pass filtered velocity and kinetic energy were compared to the combustion duration. The vertical plane vorticity and high-pass filtered velocity did not correlate with combustion performance. The horizontal plane vorticity and high-pass filtered velocity were found to exhibit modest correlation at the fixed torque condition, and somewhat lower correlation at the WOT condition. The correlation between kinetic energy and combustion duration was poor. The best correlation of flow field structure with engine performance was achieved for ports at the 0-degree port orientation. Ports at this orientation generated coherent, large-scale swirl.
A Method to Predict Fretting in Diesel Engine Connecting Rod Bearing Bores
Authors: Badding Bruce , Bhalerao Manoj , Dowell John P. , Gambheera Ramesh , Sundaram Sairam
Published: December 2008

The highly dynamic nature of the loads imposed by the rotating and reciprocating components of diesel engines makes this machine highly susceptible to fretting fatigue problems. The authors have developed a method to predict the potential for fretting damage between the connecting rod and its big-end bearing shells. This method uses the ABAQUS finite element software package to conduct detailed contact analysis at the interface between the bearing shells and the connecting rod under the applied loads of the engine operating cycle. This analysis can be performed at the design stage, given the geometry of the connecting rod assembly and the data necessary to calculate the loads. Experimental measurements of the coefficient of friction between the bearing shell and the connecting road are presented, since this is an important factor in the contact analysis. Correlations of the predicted fretting damage to observed fretting locations from engine operation are presented for two variants of connecting rod design. As with any design analysis method, caution must be exercised in the application of the technique to new cases and in the interpretation of the results.
Laser Ignition, Optics and Contamination of Optics in an I.C. Engine
Authors: Graf Josef , Weinrotter Martin , Kopecek Herbert , Wintner Ernst
Published: December 2008

Due to the progresses in exhaust emission after-treatment systems and in the development of new combustion processes, the S.I. engine has been booming in the past few years. But the efficiency will have to be improved in the future. Because of its thermodynamic benefits, the S.I. direct injection engine of the second generation — so called air guided system — shows the highest potential for gasoline engines to reduce fuel consumption. However, there are restrictions when using conventional spark ignition system. They concern the optimum position of ignition initialization and spark-plug wear, the latter being caused by inhomogeneous mixture distribution. The laser-induced ignition enables a flexible choice of the ignition location and a wear resistant initialization of the combustion process. The most crucial component here is the optics (the combustion-chamber window), through which the laser beam passes into the combustion chamber. In this paper, laser-induced ignition is discussed and its potential compared to a conventional ignition system is presented. In addition, several optic configurations are presented as well as tests regarding the minimum required laser energy and the optic contamination and self-cleaning effect of the optics. At the Institute of Internal Combustion Engines at the Vienna University of Technology the optic contamination and self-cleaning effect, which is crucial for a long-term operation, was tested on a two-cylinder research engine.
CFD Modeling of Pilot Injection and EGR in DI Diesel Engines
Authors: de Risi Arturo , Donateo Teresa , Laforgia Domenico
Published: December 2008

The simulation of direct injection diesel engines requires accurate models to predict spray evolution and combustion processes. Several models have been proposed and widely tested for traditional injection strategies characterized by single injection pulse close to top dead center. Unfortunately, these models show some limits when applied to different injection strategies so that a correct simulation of engine performances and emission cannot be achieved without changing variables included in spray and combustion models. The aim of the present investigation is to improve the prediction capability of the KIVA3V code in case of pilot injection in order to use numerical simulations to define optimized pilot injection strategies. This goal was achieved by eliminating the hypotheses of constant fuel density and constant spray angle in the KIVA3V code and by using a modified version of the Shell model. The proposed modifications to the Shell model allow a better description of low temperature kinetics by the addition of two more radicals and three new kinetics reactions. The improvements in the code were verified by comparing experimental data and numerical results over a wide range of operating conditions including single injections, pilot injections and EGR.
Improvement of Poppet Valve Injection Performance in Large-Bore Natural Gas Engines
Authors: Kim Gi-Heon , Kirkpatrick Allan , Mitchell Charles
Published: December 2008

Poppet valves have been used as fuel delivery mechanisms in internal combustion engines due to their excellent sealing characteristics. For example, in large-bore stationary natural gas engines, gas is directly injected by a poppet valve into the engine cylinder. The objectives of this paper are to show that a significant amount of stagnation pressure is lost during the gas flow through a conventional poppet valve and to suggest design improvements to obtain more efficient poppet valves with reduced stagnation pressure loss. In this paper, simple converging-diverging nozzles are incorporated into the poppet valve configuration to reduce the stagnation pressure loss originating from compressible flow structures. Numerical simulations of the gas flow through various poppet valve geometries were performed. Both push and pull poppet valve geometries with nozzle were studied. The stagnation pressure losses, momentum delivery downstream and downstream flow characteristics of the jets from conventional poppet valves and the modified valves were compared. A pressure-based valve injection efficiency was defined and used to compare the valve injection performance. A mixing fraction parameter was also defined to compare valve performance in a moving piston simulation. The results indicate that a conventional poppet valve is an inefficient mechanism to deliver momentum to the fuel-air mixture. Comparison of the results indicates that it is possible to make significant improvements of injection performance in momentum delivery by incorporating well-designed nozzles into the poppet valve geometry.
The Role of Simulation in the Development of a Fast-Actuation Solenoid C.R. Injection System
Authors: Bianchi Gian Marco , Pelloni Piero , Osbat Giovanni , Parotto Marco , Di Gioia Rita , Falfari Stefania , Brusiani Federico
Published: December 2008

Upcoming Euro 4 and Euro 5 emission standards are increasing efforts on injection system developments in order to improve mixture quality and combustion efficiency. The target features of advanced injection system are related to their capability of operating multiple injection with a precise control of amount of fuel injected, low cycle-by-cycle variability and life drift, within flexible strategies. In order to accomplish this task, performance must be optimised since injection system concept development by acting on. The extensive use of numerical approach has been identified as a necessary integration to experiments in order to put on the market high quality injection system accomplishing strict engine control strategies. The modelling approach allows focusing the experimental campaign only on critical issues saving time and costs, furthermore it is possible to deeply understand inner phenomena that cannot be measured. The lump/ID model of the whole system built into the AMESim® code was presented in previous works: particular attention was devoted in the simulation of the electromagnetic circuits, actual fluid-dynamic forces acting on needle surfaces and discharge coefficients, evaluated by means 3D-CFD simulations. In order to assess new injection system dynamic response under multiple injection strategies reproducing actual engine operating conditions it is necessary to find to proper model settings. In this work the integration between the injector and the system model, which comprehends the pump, the pressure regulator, the rail and the connecting-pipes, will be presented. For reproducing the dynamic response of he whole system will be followed a step-by-step approach in order to prevent modelling inaccuracies. Firstly will be presented the linear analysis results performed in order to find injection system own natural frequencies. Secondly based on linear analysis results will be found proper injection system model settings for predicting dynamic response to external excitations, such as pump perturbations, pressure regulator dynamics and injection pulses. Thirdly experimental results in terms of instantaneous flow rate and integrated injected volume for different operating conditions will be presented in order to highlight the capability of the modelling methodology in addressing the new injection system design.
A 2D Simulation Method for Computing Droplet Size Spectrum During the Atomization of High-Speed Liquid Jets
Authors: Bianchi Gian Marco , Pelloni Piero , Toninel Stefano , Paganelli Davide , Suzzi Daniele
Published: December 2008

Based on both experimental observations and available numerical methods, an innovative 2D approach for determining droplet size during the atomization process has been developed. Based on experimental evidences (see [1] and [2]) atomization of turbulent high speed jets is assumed to occur in a two stage process: ligaments detachment and droplets formation. The simulation method here proposed wants to take the advantages typical of the two most effective methods in spray investigation. It joins LES (i.e Large Eddy Simulations) approach and Linear Stability Analysis: the first one is used to solve the liquid-air fluid dynamics interaction and in particular the instabilities leading to ligament formation. The second one is finally adopted to compute the droplet size spectrum from ligament break-up. Therefore dynamics of ligament formation is directly computed while droplet formation is modelled by using a Linear Stability Analysis. The numerical simulation adopts a VOF (i.e. Volume of Fluid) method to track liquid-gas interface. Turbulence effects on liquid surface are accounted for by adding a turbulent flow field at the nozzle exit which represents a part of the boundary condition of the computational domain. A physical criterion is then applied to detach ligaments from liquid jet surface which will reduce in diameter during simulation. The droplet formation is then computed by applying the linear stability analysis to the ligaments, assumed being circular and subject to circulation. An extensive validation and sensitivity analysis has been carried out in order to assess method advantages and limits. The experimental results of Wu et al. [3] and Horoyasu et al. [4] were used as test cases. A sensitivity analysis has been performed under typical HSDI Diesel engine injection conditions. The method proved to exhibit promising attitude in the reconstruction of the droplet size spectrum depending on injection parameter or conditions.
Common Rail Fuel Injection: L’Orange’s Solution to Reduced Fuel Consumption and Exhaust Emissions
Authors: Jorach Rainer W. , Schneider Hartmut , Bucher Torsten , Schauer Thomas C.
Published: December 2008

To meet the exhaust emission requirements implemented by U. S. EPA, UIC, IMO and others, it is not only necessary to develop new engines and combustion systems that meet these requirements, but also to update existing engines with low emission technologies. The electronic common rail fuel system has positive advantages over conventional methods, including increased fuel efficiency and limited exhaust emissions and smoke. Since only one compact high pressure common rail pump is needed, instead of one jerk pump per cylinder, to adapt to the existing engine designs, the only challenge is to fit the injectors into the existing cylinder heads. This publication evaluates the potential impacts of this new technology on emissions and fuel consumption. It outlines component design in detail and illustrates some specific production issues. One unique retrofit proposal, focused towards existing engines, will be a low emissions kit supplied by L’Orange and Fluid Mechanics for application on EMD 645 and 710 engines. These two-stroke engines have been built since 1965 and more than 50,000 exist today, mostly on large locomotives in the NAFTA region. The retrofit kit is backed by L’Orange’s knowledge and experience in the design and production of over 150,000 common rail fuel injectors supplied to MTU and Detroit Diesel series 4000 engines.
Combustion Characteristics and Engine Performance of a New Radio Frequency Electrostatic Ignition System Igniting Lean Air-Fuel Mixtures
Authors: Freen Paul D. , Gingrich Jess , Chiu James
Published: December 2008

Recently, industry and government have joined together to develop high efficiency, low emissions, natural gas fueled, industrial, reciprocating engines for power generation. The California Energy Commission targets fuel-to-electricity efficiency at over 50% and NOx less than 0.01 gm/BHP-hr by the year 2010 [1]. The Department of Energy’s ARES program has targeted 50% efficiency and 0.1 gm/BHP-hr NOx by 2010 [2]. The engine manufacturers have determined that these goals cannot be met with current ignition system technology. They have jointly developed a specification for the next generation ignition system [3], which will support meeting the engine cost, efficiency and emissions goals. The Electrically Controlled Combustion Optimization System (ECCOS) is a new technology (patent pending) which is designed to meet or exceed this specification. This ignition system generates a high voltage, low current, radio frequency electrostatic field inside the combustion chamber to efficiently ionize the air and fuel mixture and initiate multiple flame fronts. The system is able to reliably introduce much higher ionization energy to the combustion chamber than conventional ignition systems because the ionization is done with a high voltage electric field, not high temperature. Conventional ignition systems generate up to 30,000 deg F of temperature in the spark plug gap. This temperature is created in the plug gap by a high current, low voltage plasma arc. The reliance of the conventional ignition system on temperature to initiate combustion limits the maximum energy that can be delivered because the high temperatures erode the electrodes. Since the ECCOS does not generate these high temperatures, electrode erosion should not be a problem. This paper presents a comparison of combustion characteristics between a conventional ignition system and the ECCOS igniting various mixture rations of propane and air in a constant volume combustion test chamber. Pressure rise rates as well as combustion photographs of the ignition and flame propagation processes are presented. In addition, experimental data obtained from the natural gas, single-cylinder engine operating with a conventional ignition system and the ECCOS are presented. Combustion rates, ignition delay, fuel consumption and emissions are presented at various air-fuel ratios.
High-T NOx Sensing Elements Using Conductive Oxides and Pt
Authors: West David L. , Montgomery Fred C. , Armstrong Timothy R.
Published: December 2008

Development of NOx sensing elements intended for operation at T ∼600 °C are described. The elements were fabricated by depositing co-planar La1-x Srx BO3 (B = Cr, Fe) and Pt electrodes on yttria-stabilized zirconia substrates. Characterization of the elements included response to NO2 and NO as well as the [O2] dependence of the NO2 response. Much stronger (∼ 40 mV for 450 ppm NO2 in 7 vol% O2 at 600 °C) sensing responses were observed for NO2 than NO, indicating these elements are best suited for detection of NO2. Pronounced asymmetries were observed between the NO2 step response and recovery times for the elements, with temperature being the primary variable governing the recovery times in the temperature range 500–700 °C.
A Numerical Study on Uncontrolled Regeneration Processes in Diesel Particulate Filters
Authors: Wang Dong , Wang Meiping , Reader Graham T. , Zheng Ming
Published: December 2008

An effective regeneration is needed to remove the accumulated soot in a Diesel Particulate Filter (DPF). However, the sudden heat release by soot oxidation during an uncontrolled thermal regeneration process may cause the substrate of a DPF to overheat. The consequent thermal stress could even result in structural failure. In this paper, a cone-dimensional transient model was employed to describe the exhaust flow, heat transfer, and chemical reaction processes within the DPF substrate during regeneration. The model was validated preliminarily against the experimental data of previous researchers. By using this mode, a variety of uncontrolled regeneration processes were simulated to analyze the different mechanisms of DPF overheating. The results show that the exhaust temperature, oxygen concentration, and PM loading are three major factors that effect DPF overheating. Furthermore, the tendency of uncontrolled thermal runaway could be reduced by changing either the thermal runaway could be reduced by changing either the thermal properties or the structure of the DPF substrate.