The Experts below are selected from a list of 210 Experts worldwide ranked by ideXlab platform
Evangelos G. Giakoumis - One of the best experts on this subject based on the ideXlab platform.
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cylinder wall insulation effects on the first and second law balances of a turbocharged diesel engine operating under Transient Load conditions
Energy Conversion and Management, 2007Co-Authors: Evangelos G. GiakoumisAbstract:During the last decades there has been an increasing interest in the low heat rejection (LHR) diesel engine. In an LHR engine, an increased level of temperatures inside the cylinder is achieved, resulting from the insulation applied to the walls. The steady-state, LHR engine operation has been studied so far by applying either first- or second-law balances. Only a few works, however, have treated this subject during the very important Transient operation with the results limited to the engine speed response. To this aim an experimentally validated Transient diesel engine simulation code has been expanded so as to include the second-law balance. Two common insulators for the engine in hand, i.e. silicon nitride and plasma spray zirconia are studied and their effect is compared to the nominal non-insulated operation from the first- and second-law perspective. It is revealed that after a step increase in Load, the second-law values unlike the first-law ones are heavily impacted by the insulation scheme applied. Combustion and total engine irreversibilities decrease significantly (up to 23% for the cases examined) with increasing insulation. Unfortunately, this decrease is not transformed into an increase in the mechanical work but rather increases the potential for extra work recovery owing to the higher availability content of the exhaust gas.
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Availability analysis of a turbocharged diesel engine operating under Transient Load conditions
Energy, 2004Co-Authors: Constantine D. Rakopoulos, Evangelos G. GiakoumisAbstract:A computer analysis is developed for studying the energy and availability performance of a turbocharged diesel engine, operating under Transient Load conditions. The model incorporates many novel features for the simulation of Transient operation, such as detailed analysis of mechanical friction, separate consideration for the processes of each cylinder during a cycle (“multi-cylinder” model) and mathematical modeling of the fuel pump. This model has been validated against experimental data taken from a turbocharged diesel engine, located at the authors’ laboratory and operated under Transient conditions. The availability terms for the diesel engine and its subsystems are analyzed, i.e. cylinder for both the open and closed parts of the cycle, inlet and exhaust manifolds, turbocharger and aftercooler. The present analysis reveals, via multiple diagrams, how the availability properties of the diesel engine and its subsystems develop during the evolution of the engine cycles, assessing the importance of each property. In particular the irreversibilities term, which is absent from any analysis based solely on the first-law of thermodynamics, is given in detail as regards Transient response as well as the rate and cumulative terms during a cycle, revealing the magnitude of contribution of all the subsystems to the total availability destruction.
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The Effect of Various Dynamic, Thermodynamic and Design Parameters on the Performance of a Turbocharged Diesel Engine Operating under Transient Load Conditions
SAE Technical Paper Series, 2004Co-Authors: Constantine D. Rakopoulos, Evangelos G. Giakoumis, Dimitrios T. Hountalas, Dimitrios C. RakopoulosAbstract: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. The model is validated against experimental data for various Load changes. The effect of several dynamic, thermodynamic and design parameters is studied, i.e. Load schedule (type, and duration of Load applied), turbocharger mass moment of inertia, exhaust manifold volume and configuration, cylinder wall temperature, aftercooler effectiveness as well as an interesting case of a malfunctioning fuel pump. Explicit diagrams are given to show how, after an increase in Load, each parameter examined affects the engine speed response, as well as other properties of the engine and turbocharger such as fuel pump rack position, boost pressure and turbocharger speed. It is shown that certain parameters, such as the type of connected Loading, the turbocharger inertia, a damaged fuel pump and the exhaust manifold volume, can have a significant effect on the engine and turbocharger Transient performance. However others, such as the cylinder wall temperature, the aftercooler effectiveness and the exhaust manifold configuration have a less important effect as regards Transient response and final equilibrium conditions.
A. Maji - One of the best experts on this subject based on the ideXlab platform.
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Foundation on geogrid-reinforced sand – effect of Transient Loading
Geotextiles and Geomembranes, 1998Co-Authors: Braja M. Das, A. Maji, E.c. ShinAbstract:Abstract Laboratory model test results for the settlement of a square surface foundation supported by geogrid-reinforced sand and subjected to Transient Load are presented. The tests were conducted with one model foundation at one relative density of compaction using only one type of geogrid. Based on the model test results, it appears that geogrid reinforcement does reduce the settlement of the foundation. The settlement reduction factor is a function of the depth of reinforcement.
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Transient Loading-related settlement of a square foundation on geogrid-reinforced sand
Geotechnical & Geological Engineering, 1994Co-Authors: Braja M. Das, A. MajiAbstract:Laboratory model test results are presented that determine the effectiveness of using layers of geogrids as reinforcement in sand to reduce the settlement of square surface foundations subjected to Transient Loading. The model tests were conducted with only one type of geogrid at one relative density of compaction of sand. The maximum intensity of the Transient Load applied always exceeded the static ultimate bearing capacity of the foundation when supported by unreinforced sand. The settlement reduction factors for various depths of reinforcement have been determined.
Braja M. Das - One of the best experts on this subject based on the ideXlab platform.
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Foundation on geogrid-reinforced sand – effect of Transient Loading
Geotextiles and Geomembranes, 1998Co-Authors: Braja M. Das, A. Maji, E.c. ShinAbstract:Abstract Laboratory model test results for the settlement of a square surface foundation supported by geogrid-reinforced sand and subjected to Transient Load are presented. The tests were conducted with one model foundation at one relative density of compaction using only one type of geogrid. Based on the model test results, it appears that geogrid reinforcement does reduce the settlement of the foundation. The settlement reduction factor is a function of the depth of reinforcement.
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Transient Loading-related settlement of a square foundation on geogrid-reinforced sand
Geotechnical & Geological Engineering, 1994Co-Authors: Braja M. Das, A. MajiAbstract:Laboratory model test results are presented that determine the effectiveness of using layers of geogrids as reinforcement in sand to reduce the settlement of square surface foundations subjected to Transient Loading. The model tests were conducted with only one type of geogrid at one relative density of compaction of sand. The maximum intensity of the Transient Load applied always exceeded the static ultimate bearing capacity of the foundation when supported by unreinforced sand. The settlement reduction factors for various depths of reinforcement have been determined.
E.c. Shin - One of the best experts on this subject based on the ideXlab platform.
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Foundation on geogrid-reinforced sand – effect of Transient Loading
Geotextiles and Geomembranes, 1998Co-Authors: Braja M. Das, A. Maji, E.c. ShinAbstract:Abstract Laboratory model test results for the settlement of a square surface foundation supported by geogrid-reinforced sand and subjected to Transient Load are presented. The tests were conducted with one model foundation at one relative density of compaction using only one type of geogrid. Based on the model test results, it appears that geogrid reinforcement does reduce the settlement of the foundation. The settlement reduction factor is a function of the depth of reinforcement.
Deepak Divan - One of the best experts on this subject based on the ideXlab platform.
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Sharing Transient Loads : Causes of Unequal Transient Load Sharing in Islanded Microgrid Operation
IEEE Industry Applications Magazine, 2014Co-Authors: Andrew D. Paquette, Matthew J. Reno, Ronald G. Harley, Deepak DivanAbstract:When inverters in voltage control mode are paired with synchronous generators (SGs), they exhibit poor Transient Load sharing in islanded operation. It is well known that power electronics respond more quickly where the inverter initially picks up the majority of every Load step, and the generator's output slowly increases until they reach their steady-state Load sharing given by droop settings. This excessive Transient power output from the inverter constrains its rating relative to the largest Load step and could negatively impact the battery life in battery energy-storage inverters. This article provides a detailed examination of the differences between the frequency-regulation characteristics of inverters and generators to explain, in a novel way, the cause of the poor Transient power sharing. The tradeoff between an improved Transient Load sharing and increased voltage and frequency Transients is highlighted, and it is demonstrated that equal Transient Load sharing can be achieved by emulating an SG using a power hardware-in-the-loop (HIL) approach. Validation is provided by simulation and experimental results.
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Transient Load sharing between inverters and synchronous generators in islanded microgrids
2012 IEEE Energy Conversion Congress and Exposition (ECCE), 2012Co-Authors: Andrew D. Paquette, Matthew J. Reno, Ronald G. Harley, Deepak DivanAbstract:When inverters in voltage control mode are paired with synchronous generators they exhibit poor Transient Load sharing in islanded operation. The inverter initially picks up the majority of every Load step, and the generator's output slowly increases until they reach their steady state Load sharing given by droop settings. This excessive Transient power output from the inverter constrains its rating compared to the largest anticipated Load step, and could negatively impact battery life in battery energy storage inverters. This paper examines the Transient Load sharing characteristics between synchronous generators and inverters in voltage control, i.e. grid-supporting-grid-forming control, and investigates methods to improve it. An equivalent circuit is proposed to describe the initial power sharing ratio, and the effects of increased inverter droop slope and increased governor integral gain are investigated. An inverter control strategy of emulating a synchronous generator is shown to provide good Transient Load sharing. Validation is provided by simulation and experimental results for real and reactive Loads.