Centrifugal Compressors During Fast Transients

2011 ◽  
Vol 133 (7) ◽  
Author(s):  
Matthew Blieske ◽  
Rainer Kurz ◽  
Augusto Garcia-Hernandez ◽  
Klaus Brun
Keyword(s):  
Steady State ◽  
Flow Speed ◽  
Operating Conditions ◽  
Nonstationary Heat Transfer ◽  
Fast Transients ◽  
Rapid Transients ◽  
Relationship Of ◽  
The Impact ◽  
Flow Head

Transient studies for compressor systems allow the prediction of the compressor system behavior during fast transients such as they occur during emergency shutdowns. For the system simulations, the compressor behavior is assumed to be quasi-steady-state. This means in particular that the steady-state compressor flow-head-efficiency-speed map remains valid. During well instrumented emergency shutdown tests conducted on a centrifugal compressor system under realistic operating conditions, data showing the head-flow-speed relationship of the rapidly decelerating compressor were taken. These data are compared with steady-state head-flow relationships taken at a number of speeds. This allows the determination of the relative deviation between the transient and steady-state head-flow-relationships and thus answers the question of the validity of steady-state assumptions during rapid transients. The impact of the fast transients on efficiency and consumed power, which can be derived from the speed decay of the system, as well as the impact of nonstationary heat transfer are also evaluated and reported.

Centrifugal Compressors During Fast Transients

2010 ◽  
Author(s):  
Matthew Blieske ◽  
Augusto Garcia Hernandez ◽  
Rainer Kurz ◽  
Klaus Brun
Keyword(s):  
Steady State ◽  
Flow Speed ◽  
Operating Conditions ◽  
Fast Transients ◽  
Rapid Transients ◽  
Relationship Of ◽  
The Impact ◽  
Flow Head ◽  
Stationary Heat Transfer ◽  
Transient And Steady State

Transient studies for compressor systems allow the prediction of the compressor system behavior during fast transients such as they occur during emergency shutdowns. For the system simulations, the compressor behavior is assumed to be quasi steady state. This means in particular that the steady state compressor flow-head-efficiency-speed map remains valid. During well instrumented emergency shutdown tests conducted on a centrifugal compressor system under realistic operating conditions, data showing the head-flow-speed relationship of the rapidly decelerating compressor was taken. This data is compared to steady state head-flow relationships taken at a number of speeds. This allows to determine the relative deviation between the transient and steady state head-flow-relationships, and thus answers the question of the validity of steady state assumptions during rapid transients. The impact of the fast transients on efficiency and consumed power, which can be derived from the speed decay of the system, as well as the impact of non-stationary heat transfer are also evaluated and reported.

The impact of the ESA 2010 on statistics of the general government sector

2015 ◽  
Vol 60 (11) ◽  
pp. 1-15
Author(s):  
Olga Leszczyńska-Luberek
Keyword(s):  
The European Union ◽  
Government Sector ◽  
General Government ◽  
European System ◽  
Relationship Of ◽  
The Impact ◽  
Methodological Guidelines ◽  
The Relationship ◽  
Excessive Deficit Procedure

The author presents the importance of the new European System of National and Regional Accounts (ESA 2010) for statistics of the general government sector. She pays particular attention to the development of data for the excessive deficit procedure. The article explains the methodological changes made to the studies in this field parallel to the ESA 2010. It discusses, among others, issues related to defining the deficit and debt of the general government, as well as the determination of a new way registering transfer of liabilities of pension schemes. It also presents the impact of new methodological guidelines for the relationship of deficit and debt to GDP in the Member States of the European Union.

Dynamic Analysis of Mechanical Systems With Clearances—Part 1: Formation of Dynamic Model

1971 ◽  
Vol 93 (1) ◽  
pp. 305-309 ◽  
Author(s):  
S. Dubowsky ◽  
F. Freudenstein
Keyword(s):  
Equations Of Motion ◽  
Operating Conditions ◽  
Coupled Systems ◽  
Dynamical Response ◽  
Dynamic Force ◽  
Dynamical Equations ◽  
Mechanical Joint ◽  
The Impact ◽  
Insight Into

A mathematical model of an elastic mechanical joint with clearances has been formulated and the dynamical equations of motion derived (Part I). The model, which we have called an Impact Pair, is basic to the determination of the dynamical response of mechanical and electromechanical systems with clearances, including determination of dynamic force amplification, frequency response, time-displacement characteristics, and other dynamic characteristics. Whenever possible, the results for the impact pair under various operating conditions are illustrated by graphs, which may also offer some insight into the behavior of clearance-coupled systems.

scholarly journals Modeling of Three-Way Catalyst Dynamics for a Compressed Natural Gas Engine during Lean–Rich Transitions

2019 ◽  
Vol 9 (21) ◽  
pp. 4610 ◽  
Author(s):  
Dario Di Maio ◽  
Carlo Beatrice ◽  
Valentina Fraioli ◽  
Pierpaolo Napolitano ◽  
Stefano Golini ◽  
...  
Keyword(s):  
Steady State ◽  
Natural Gas ◽  
Catalytic Converter ◽  
Operating Conditions ◽  
Oxygen Storage ◽  
Continuous Control ◽  
Engine Exhaust ◽  
Compressed Natural Gas ◽  
The Impact ◽  
Three Way Catalyst

The main objective of the present research activity was to investigate the effect of very fast composition transitions of the engine exhaust typical in real-world driving operating conditions, as fuel cutoff phases or engine misfire, on the aftertreatment devices, which are generally very sensitive to these changes. This phenomenon is particularly evident when dealing with engines powered by natural gas, which requires the use of a three-way catalyst (TWC). Indeed, some deviations from the stoichiometric lambda value can interfere with the catalytic converter efficiency. In this work, a numerical “quasi-steady” model was developed to simulate the chemical and transport phenomena of a specific TWC for a compressed natural gas (CNG) heavy-duty engine. A dedicated experimental campaign was performed in order to evaluate the catalyst response to a defined λ variation pattern of the engine exhaust stream, thus providing the data necessary for the numerical model validation. Tests were carried out to reproduce oxygen storage phenomena that make catalyst behavior different from the classic steady-state operating conditions. A surface reaction kinetic mechanism concerning CH4, CO, H2, oxidation and NO reduction has been appropriately calibrated at different λ values with a step-by-step procedure, both in steady-state conditions of the engine work plan and during transient conditions, through cyclical and consecutive transitions of variable frequency between rich and lean phases. The activity also includes a proper calibration of the reactions involving cerium inside the catalyst in order to reproduce oxygen storage and release dynamics. Sensitivity analysis and continuous control of the reaction rate allowed evaluating the impact of each of them on the exhaust composition in several operating conditions. The proposed model predicts tailpipe conversion/formation of the main chemical species, starting from experimental engine-out data, and provides a useful tool to evaluate the catalyst’s performance.

Formaldehyde Formation in Large Bore Engines Part 2: Factors Affecting Measured CH2O

1999 ◽  
Vol 122 (4) ◽  
pp. 611-616 ◽  
Author(s):  
Daniel B. Olsen ◽  
Charles E. Mitchell
Keyword(s):  
Natural Gas ◽  
Air Pollutant ◽  
Operating Conditions ◽  
Factors Affecting ◽  
Natural Gas Engines ◽  
Spark Timing ◽  
Wide Range ◽  
Hazardous Air Pollutant ◽  
Relationship Of ◽  
The Impact

Current research shows that the only hazardous air pollutant of significance emitted from large bore natural gas engines is formaldehyde CH2O. A literature review on formaldehyde formation is presented focusing on the interpretation of published test data and its applicability to large bore natural gas engines. The relationship of formaldehyde emissions to that of other pollutants is described. Formaldehyde is seen to have a strong correlation to total hydrocarbon (THC) level in the exhaust. It is observed that the ratio of formaldehyde to THC concentration is roughly 1.0–2.5 percent for a very wide range of large bore engines and operating conditions. The impact of engine operating parameters, load, rpm, spark timing, and equivalence ratio, on formaldehyde emissions is also evaluated. [S0742-4795(00)01004-8]

scholarly journals Synthesis of polar copolymers by the process of emulsion via free radicals (FRP)

2019 ◽  
pp. 1-5
Author(s):  
Luis Mario Magaña-Maldonado ◽  
David Contreras-López
Keyword(s):  
Free Radicals ◽  
Batch Reactor ◽  
Operating Conditions ◽  
Polymerization Process ◽  
Optimal Operating ◽  
Molecular Weights ◽  
Polymer Industry ◽  
The Impact ◽  
Vinyl Propionate

At present, the polymer industry has gained increasing importance due to the versatility of its properties, as well as the impact they have on the environment. The present investigation provides the determination of optimal operating conditions for the polymerization of styrene and vinyl propionate in a Batch reactor, as well as the copolymerization of styrene with propionate monomers by the process of emulsion via free radicals, allowing to observe the variations with respect to Reaction yields and molecular weights. Another important factor is the activation of the initiator so that the polymerization process begins within each of the micelles. Likewise, it was found that, in the copolymerizations, there are considerable variations with respect to reaction yields and molecular weights as the concentrations are modified. In addition, it was found that there are higher yields in styrene polymerizations per solution than emulsion.

scholarly journals Maximizing The Impact Of Improvement Efforts On Customer Satisfaction

2015 ◽  
Vol 31 (3) ◽  
pp. 1005
Author(s):  
Dooyoung Shin ◽  
Jon Kalinowski ◽  
Sung Kim ◽  
In-Jae Kim
Keyword(s):  
Customer Satisfaction ◽  
Piecewise Linear ◽  
Piecewise Linear Approximation ◽  
Customer Group ◽  
Piecewise Function ◽  
Critical Attribute ◽  
Customer Satisfaction Survey ◽  
Relationship Of ◽  
The Impact

When a customer satisfaction survey consists of a large number of attributes (questionnaire items), determination of critical attributes that would make the biggest impact on customers overall satisfaction could be important, but very tedious and time-consuming process. Even though the critical attributes are identified, the improvement efforts toward these attributes are often misdirected and wasted because of the mismatch between the improvement efforts and the critical needs of the affected customer group. This paper introduces a method with which improvement efforts can be tailored to the needs of the customer group who could bring the most impactful influence on improving customer satisfaction. For the critical attribute considered, the percentage of customers who assigned a specific satisfaction rating is obtained, and the cumulative percentages of customers are examined and the target group of customers to whom the improvement efforts would be tailored is identified. The piecewise linear approximation method is also discussed to estimate the non-linear relationship of the attribute, which also may help determine the target customer group. The overall shape of the piecewise function and the slopes at the line segments may be used in determining which attributes are satisfaction-maintaining or satisfaction-enhancing, and where and how the improvement efforts should be focused in order to maximize the effectiveness of the improvement efforts.

Thermal Assessment of Cooling System Incorporating Heat Sink and Embedded Heat Pipes for Testing High Power Microelectronics

2005 ◽  
Author(s):  
Victor Adrian Chiriac ◽  
Tien-Yu Tom Lee
Keyword(s):  
Steady State ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Heat Sink ◽  
Heat Pipes ◽  
Optimal Operation ◽  
Operating Conditions ◽  
Peak Temperature ◽  
Testing System ◽  
The Impact

A numerical study was conducted to model the transient thermal behavior of a complex testing system including multiple fans, a mixing enclosure, copper inserts and a leaded package dissipating large amounts of power over short time durations. The system is optimized by choosing appropriate heat sink/fan structure for the efficient operation of the device under constant powering. The intent of the study is to provide a better understanding and prediction of a transient powering scenario at high powering levels, while evaluating the impact of alternative cooling fan/heat pipe designs on the thermal performance of the testing system. One design is chosen due to its effective thermal performance and assembly simplicity, with the package embedded in heat sink base with multiple (5) heat pipes. The peak temperature reached by the modified design with 4 cooling fans is ~95°C, with the corresponding Rja thermal resistance ~0.58°C/W. For the transient study (with embedded heat pipes and 4 fans), after one cycle, both peak temperature (at 45 s) and the end temperature (at 49 s) decrease as compared to the previous no heat pipe/single fan case (the end temperature reduces by ~16%). The temperature drop between peak and end for each cycle is ~80.2°C, while the average power per transient cycle is ~31.27W. With this power, the design with 5 perpendicular heat pipes, 4 fans and insert reaches a steady state peak temperature of ~98°C. Applying the superposition principle to the steady state value and 40.1°C fluctuation, the maximum transient temperature after a large number of cycles will not exceed ~138.1°C, satisfying the thermal budget under the current operating conditions. The benefit of the study is related to the possibility to extract the maximum and minimum temperatures for a real test involving a large number of heating-cooling cycles, yet maintaining the initial and peak temperatures within a certain range for the optimal operation of the device. The flow and heat transfer fields are investigated; using a combination of numerical and analytical methods, the thermal performance of the device undergoing large number of periodic thermal cycles is predicted. The comparison between measurement and simulation shows good agreement.

Effect of Errors in Temperature Measurement on the Accuracy of Composition of the Liquid-Vapour Phases and Their Impact on the Calculated Number of Theoretical Stages of Rectification Columns

1992 ◽  
Vol 57 (9) ◽  
pp. 1867-1878
Author(s):  
Ján Dojčanský ◽  
Soňa Bafrncová ◽  
Július Surový
Keyword(s):  
Phase Composition ◽  
Binary Systems ◽  
Equilibrium Temperature ◽  
Systematic Errors ◽  
Operating Conditions ◽  
Rectification Column ◽  
Relative Volatility ◽  
The Impact ◽  
Calculated Number

The effect of random and systematic errors in the determination of the equilibrium temperature on the phase composition in isobaric L-G equilibria was simulated on five binary systems with different size and relative volatility. The impact of the inaccuracies on the calculated number of theoretical stages of a continuously operating rectification column is discussed with respect to the different operating conditions of the separatory process.

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