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Technical Paper

Exhaust Phases in a DI Diesel Engine Based on Instantaneous Cyclic Heat Transfer Experimental Data

2013-04-08
2013-01-1646
In the present paper a new method is proposed for the analysis of the two main phases of the engine exhaust stroke blowdown and displacement. The method is based on the processing of fast-response experimental temperatures obtained from the exhaust manifold wall during the engine cycle. A novel experimental installation has been developed, which separates the engine transient temperature signals into two groups, namely the long- and the short- term response ones. This has been achieved by processing the respective signals acquired from two independent data acquisition systems. Furthermore, a new pre-amplification unit for fast response thermocouples, appropriate heat flux sensors and an innovative, object-oriented, control code for fast data acquisition have been designed and applied. For the experimental procedure a direct injection (DI), air-cooled diesel engine is used.
Technical Paper

Identification and Correction of the Error Induced by the Sampling Method Used to Monitor Cylinder Pressure of Reciprocating Internal Combustion Engines

2012-04-16
2012-01-1155
Cylinder pressure measurements are common practice for internal combustion reciprocating engines during field or lab applications for the purpose of combustion analysis, condition monitoring etc. The most accurate method is to measure cylinder pressure using a crank angle encoder as a trigger source to guarantee cylinder pressure measurement at predefined crank angle events. This solution, even though favorable, presents a number of practical difficulties for field applications and increased cost, for this reason its use is practically restricted to lab applications. Therefore a commonly used approach for ad hoc measurements is to digitize samples at fixed time intervals and then convert time into crank angle assuming a constant rotational speed. But if engine rotational speed is not constant within the engine cycle this may result to incorrect cylinder pressure CA referencing.
Technical Paper

Evaluation of a New Diagnostic Technique to Detect and Account for Load Variation during Cylinder Pressure Measurement of Large-Scale Four-Stroke Diesel Engines

2012-04-16
2012-01-1342
High efficiency, power concentration and reliability are the main requirements from Diesel Engines that are used in most technical applications. This becomes more important with the increase of engine size. For this reason the aforementioned characteristics are of significant priority for both marine and power generation applications. To guarantee efficient engine operation and maximum power output, both research and commercial communities are increasingly interested in methods used for supervision, fault-detection and fault diagnosis of large scale Diesel Engines. Most of these methods make use of the measured cylinder pressure to estimate various critical operating parameters such as, brake power, fuel consumption, compression status, etc. The results obtained from the application of any diagnostic technique, used to assess the current engine operating condition and identify the real cause of the malfunction or fault, depend strongly on the quality of these data.
Technical Paper

Experimental Investigation of Instantaneous Cyclic Heat Transfer in the Combustion Chamber and Exhaust Manifold of a DI Diesel Engine under Transient Operating Conditions

2009-04-20
2009-01-1122
In this paper, the results are presented from the analysis of the second stage of an experimental investigation with the aim to provide insight to the cyclic, instantaneous heat transfer phenomena occurring in both the cylinder head and exhaust manifold wall surfaces of a direct injection (DI), air-cooled diesel engine. Results from the first stage of the investigation concerning steady-state engine operation have already been presented by the authors in this series. In this second stage, the mechanism of cyclic heat transfer was investigated during engine transient events, viz. after a sudden change in engine speed and/or load, both for the combustion chamber and exhaust manifold surfaces. The modified experimental installation allowed both long- and short-term signal types to be recorded on a common time reference base during the transient event.
Journal Article

Possibility to Determine Diesel Engine Condition and Tuning from the Application of a Diagnostic Technique at a Single Operating Point

2009-04-20
2009-01-0681
A difficulty which exists when applying diagnostic techniques on large-scale diesel engines operating on the field, is that usually it is not possible to obtain measurement data at a wide engine operating range due to a number of constraints. In the present work is investigated the possibility to overcome this practical difficulty originating from the test procedure for engines operating on the field (i.e. marine or stationary applications). The main objective is to examine if a diagnosis procedure provides similar results when applied at various engine operating conditions. For this purpose an existing diagnostic technique, developed by the authors, is applied at different operating conditions on a large-scale two-stroke diesel engine used for power generation in a Greek island.
Journal Article

Thermodynamic Analysis of SI Engine Operation on Variable Composition Biogas-Hydrogen Blends Using a Quasi-Dimensional, Multi-Zone Combustion Model

2009-04-20
2009-01-0931
In this work, a quasi-dimensional, multi-zone combustion model is analytically presented, for the prediction of performance and nitric oxide (NO) emissions of a homogeneous charge spark ignition (SI) engine, fueled with biogas-H2 blends of variable composition. The combustion model is incorporated into a closed cycle simulation code, which is also fully described. Combustion is modeled on the basis of turbulent entrainment theory and flame stretch concepts. In this context, the entrainment speed, by which unburned gas enters the flame region, is simulated by the turbulent burning velocity of a flamelet model. A flame stretch submodel is also included, in order to assess the flame response on the combined effects of curvature, turbulent strain and nonunity Lewis number mixture. As far as the burned gas is concerned, this is treated using a multi-zone thermodynamic formulation, to account for the spatial distribution of temperature and NO concentration inside the burned volume.
Journal Article

Experimental Assessment of Instantaneous Heat Transfer in the Combustion Chamber and Exhaust Manifold Walls of Air-Cooled Direct Injection Diesel Engine

2008-04-14
2008-01-1326
An experimental analysis is carried out to investigate several heat transfer characteristics during the engine cycle, in the combustion chamber and exhaust manifold walls of a direct injection (DI), air-cooled, diesel engine. For this purpose, a novel experimental installation has been developed, which separates the engine transient temperature signals into two groups, namely the long-and the short- term response ones, processing the respective signals in two independent data acquisition systems. Furthermore, a new pre-amplification unit for fast response thermocouples, appropriate heat flux sensors and an innovative, object-oriented, control code for fast data acquisition have been designed and applied. Experimentally obtained cylinder pressure diagrams together with semi-empirical equations for instantaneous heat transfer were used as basis for the calculation of overall heat transfer coefficient.
Technical Paper

Evaluation of Various Dynamic Issues During Transient Operation of Turbocharged Diesel Engine with Special Reference to Friction Development

2007-04-16
2007-01-0136
The modeling of transient turbocharged diesel engine operation appeared in the early seventies and continues to be in the focal point of research, due to the importance of transient response in the everyday operating conditions of engines. The majority of research has focused so far on issues concerning thermodynamic modeling, as these directly affect heat release predictions and consequently performance and pollutants emissions. On the other hand, issues concerning the dynamics of transient operation are often disregarded or over-simplified, possibly for the sake of speeding up program execution time. In the present work, an experimentally validated transient diesel engine simulation code is used to study and evaluate the importance of such dynamic issues. First of all, the development of various forces (piston, connecting rod, crank and main crankshaft bearings) is computed and illustrated in order to evaluate the importance of abrupt load increases on the bearings durability.
Technical Paper

Comparative Evaluation of EGR, Intake Water Injection and Fuel/Water Emulsion as NOx Reduction Techniques for Heavy Duty Diesel Engines

2007-04-16
2007-01-0120
Despite the improvement in HD Diesel engine out emissions future emission legislation requires significant reduction of both NOx and particulate matter. To accomplish this task various solutions exist involving both internal and external measures. As widely recognized, it will be possibly required to employ both types of measures to meet future emission limits. Towards this direction, it is necessary to reduce NOx further using internal measures. Several solutions exist in that area, but the most feasible ones according to the present status of technical knowledge are EGR, water injection or fuel/water emulsions. These technologies aim to the reduction of both the gas temperature and oxygen concentration inside the combustion chamber that strongly affect NOx formation. However, there remain open points mainly concerning the effectiveness of water addition techniques and penalties related to bsfc and soot emissions.
Technical Paper

Description of in-Cylinder Combustion Processes in HCCI Engines Using a Multi-Zone Model

2005-04-11
2005-01-0171
In the present work, a multi-zone model is presented for the simulation of HCCI engines. This model is an improvement of a previous one developed by the authors. The present model describes the combustion, heat and mass transfer processes for the closed part of the engine cycle, i.e. compression, combustion and expansion. The zones occupy geometrical positions within the engine cylinder and exchange heat and mass throughout the compression and expansion strokes, based on their spatial configuration. Heat exchange is considered between zones and to the cylinder wall. A phenomenological model has been developed to describe mass exchange between zones and the flow of a portion of the in-cylinder mixture in and out of the crevice region. The crevice flow is a new feature and is included in the present model since the crevice regions are considered to contribute to unburned HC emissions. Another new feature is the incorporation of chemical kinetics, based on combustion chemistry reactions.
Technical Paper

Study of the Transient Behavior of Turbocharged Diesel Engines Including Compressor Surging Using a Linearized Quasi-Steady Analysis

2005-04-11
2005-01-0225
The transient operation of turbocharged diesel engines during turbocharger compressor surging is investigated through simulation. This form of compressor dynamic instability can generate large amplitude compressor mass flow and pressure rise oscillations, sometimes leading even to flow reversals, and may also induce severe torsional loading to the turbocharger shaft. A model predicting the dynamic behavior of the engine air-charging system when compressor surging occurs was developed in conjunction with a linearized quasi-steady diesel engine simulation code. This analysis possesses the advantage over the more detailed engine codes of basic simplicity, speed of calculation and no need of many engine and turbocharger components parameters given as input data. Emphasis is given to the correct modeling of the physics of the phenomena concerned. Transient operation runs, including critical cases for surging initiation, were applied for two similar six-cylinder diesel engines.
Technical Paper

Second-Law Analysis of Indirect Injection Turbocharged Diesel Engine Operation under Steady-State and Transient Conditions

2005-04-11
2005-01-1131
A second-law analysis is performed in both chambers of an indirect injection turbocharged diesel engine and the simulation program developed is used to study the second-law performance of the engine at various operating conditions, steady state and transient. The simulation developed is based on the filling and emptying approach and provides detailed analysis of thermodynamic, dynamic and second-law differential equations on a degree crank angle basis. It incorporates a detailed mathematical simulation of the fuel pump and solves each equation separately for each one of the six cylinders of the engine in hand. The model is validated against experimental data at steady state and transient conditions, obtained at the authors' laboratory. The prechamber rate and cumulative availability terms and irreversibilities are computed and depicted against the main chamber ones during the 720 degrees crank angle of an engine cycle.
Technical Paper

Modeling the Effects of EGR on a Heavy Duty DI Diesel Engine Using a new Quasi-Dimensional Combustion Model

2005-04-11
2005-01-1125
The model has already been applied on an old technology, naturally aspirated HSDI Diesel engine and on a heavy-duty turbocharged DI one equipped with a high pressure PLN fuel injection system, and the results were satisfying as far as performance and pollutant emissions (Soot and NO) are concerned. Taking into account that the main scope of engine simulation models is to assist engineers and researchers to understand the complex mechanisms involved in diesel engine combustion and pollutants formation and that through the continues engine development, new techniques are implemented, it is obvious that engine simulation models must always be enhanced with new features in order to be kept up-to-date. In this study the model has been modified to take into account the effect of EGR, since the latter one is a measure that will be used more extensively in the future to control NO emissions from turbocharged HDDI Diesel engines.
Technical Paper

Experimental Heat Release Rate Analysis in Both Chambers of an Indirect Injection Turbocharged Diesel Engine at Various Load and Speed Conditions

2005-04-11
2005-01-0926
A heat release analysis of experimental pressure diagrams, appropriate for indirect injection (divided chamber) diesel engines, is developed and used to obtain heat release rate profiles during the combustion process in each combustion chamber. Attention is paid to the correct processing of the data, due to the inherent complexity of the mass interchange between the two combustion chambers. The analysis concerns a turbocharged, indirect injection diesel engine, having a very small pre-chamber and a very narrow connecting passageway, operated at various load and speed conditions, located at the authors' laboratory. An extended experimental work, at steady-state conditions, is conducted on a specially developed test bed configuration of this engine, which is connected to a high-speed data acquisition and processing system.
Technical Paper

Use of JP-8 Aviation Fuel and Biodiesel on a Diesel Engine

2004-10-25
2004-01-3033
The present paper aims to discuss the quality characteristics of Jet Fuels used in the Greek market in comparison with fuels used in other countries and to evaluate jet fuels along with diesel and biodiesel on a diesel engine. To establish the quality characteristics for Jet Fuels of the Greek market, fuel samples were collected from the local refineries on a regular basis, thus monitoring the fuel quality fluctuation over time. JP8, along with diesel and biodiesel, were used alone and in mixtures on a single cylinder stationary diesel engine. Emissions and volumetric fuel consumption were measured under various loads.
Technical Paper

Development of a New Multi-Zone Model for the Description of Physical Processes in HCCI Engines

2004-03-08
2004-01-0562
Homogeneous Charge Compression Ignition (HCCI) engines have the potential of reducing NOx emissions as compared to conventional Diesel or SI engines. Soot emissions are also very low due to the premixed nature of combustion. However, the unburned hydrocarbon emissions are relatively high and the same holds for CO emissions. The formation of these pollutants, for a given fuel, is strongly affected by the temperature distribution as well as by the charge motion within the engine cylinder. The foregoing physical mechanisms determine the local ignition timing and burning rate of the charge affecting engine efficiency, performance and stability. Obviously the success of any model describing HCCI combustion depends on its ability to describe adequately both the chemistry of combustion and the physical phenomena, i.e. heat and mass transfer within the cylinder charge. In the present study a multi-zone model is developed to describe the heat and mass transfer mechanism within the cylinder.
Technical Paper

The Effect of Various Dynamic, Thermodynamic and Design Parameters on the Performance of a Turbocharged Diesel Engine Operating under Transient Load Conditions

2004-03-08
2004-01-0926
Thermodynamic, dynamic and design parameters have a significant and often conflicting impact on the transient response of a compression ignition engine. Knowing the contribution of each parameter on transient operation could direct the designer to the appropriate measures for better engine performance. To this aim an explicit simulation program developed is used to study the performance of a turbocharged diesel engine operating under transient load conditions. The simulation developed, based on the filling and emptying approach, provides various innovations as follows: Detailed analysis of thermodynamic and dynamic differential equations, on a degree crank angle basis, accounting for the continuously changing nature of transient operation, analysis of transient mechanical friction, and also a detailed mathematical simulation of the fuel pump. Each equation in the model is solved separately for every cylinder of the 6-cylinder diesel engine considered.
Technical Paper

Some Considerations on the Estimation of the Heat Release of DI Diesel Engines Using Modelling Techniques

2004-03-08
2004-01-1405
Simulation models are widely used from research engineers to investigate the combustion mechanism of DI diesel engines. These models can be used, as tools to either comprehend information provided by experimental data or to perform predictions and assist the development process. As widely recognized a valuable source of information for engine performance and emissions studies is the cylinder pressure trace. It can provide after processing information concerning the combustion rate of fuel injected inside the combustion chamber. Often it is also used to calibrate simulation models or even to derive correlations to represent the combustion rate of fuel inside the combustion chamber. The present research team has during the development process of a simulation model for the description of DI diesel engine performance and emissions realized that there exists a serious problem.
Technical Paper

Axial Crushing of Hybrid Square Sandwich Composite Vehicle Hollow Bodyshells

2001-10-01
2001-01-3296
Two different structural configurations of hybrid sandwich composite rail vehicle tubular component, made of foam-cored composite sandwich panels with integral FRP energy absorbing inserts, are examined under axial loading. The mechanical response of these small-scale bodyshells under impact conditions is investigated both at macro- and microscale. Failure modes and the energy absorbing characteristics of the collapsed structural components are analyzed, taking into account the effect of material and design parameters.
Technical Paper

Structure of high-pressure diesel sprays

2001-09-23
2001-24-0009
A comprehensive set of computational and experimental results for high- pressure diesel sprays are presented and discussed. The test cases investigated include injection of diesel into air under both atmospheric and high pressure/temperature chamber conditions, injection against pressurized and cross-flowing CF6 simulating respectively the density and flow conditions of a diesel engine at the time of injection, as well as injection into the piston bowl of both research and production turbocharged high-speed DI diesel engines. A variety of high-pressure injection systems and injector nozzles have been used including mechanical and electronic high-pressure pumps as well as common-rail systems connected to nozzles incorporating a varying number of holes with diameters ranging from conventional to micro-size.
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