scholarly journals Optimization Modeling of Irreversible Carnot Engine from the Perspective of Combining Finite Speed and Finite Time Analysis

Entropy ◽  
2021 ◽  
Vol 23 (5) ◽  
pp. 504
Author(s):  
Monica Costea ◽  
Stoian Petrescu ◽  
Michel Feidt ◽  
Catalina Dobre ◽  
Bogdan Borcila
Keyword(s):  
Direct Method ◽  
Engine Performance ◽  
Carnot Cycle ◽  
Time Analysis ◽  
Time Duration ◽  
Pressure Losses ◽  
First Law Of Thermodynamics ◽  
Finite Speed ◽  
Piston Speed ◽  
Internal Irreversibility

An irreversible Carnot cycle engine operating as a closed system is modeled using the Direct Method and the First Law of Thermodynamics for processes with Finite Speed. Several models considering the effect on the engine performance of external and internal irreversibilities expressed as a function of the piston speed are presented. External irreversibilities are due to heat transfer at temperature gradient between the cycle and heat reservoirs, while internal ones are represented by pressure losses due to the finite speed of the piston and friction. Moreover, a method for optimizing the temperature of the cycle fluid with respect to the temperature of source and sink and the piston speed is provided. The optimization results predict distinct maximums for the thermal efficiency and power output, as well as different behavior of the entropy generation per cycle and per time. The results obtained in this optimization, which is based on piston speed, and the Curzon–Ahlborn optimization, which is based on time duration, are compared and are found to differ significantly. Correction have been proposed in order to include internal irreversibility in the externally irreversible Carnot cycle from Curzon–Ahlborn optimization, which would be equivalent to a unification attempt of the two optimization analyses.

Performances Evaluation for a Reversed Quasi-Carnot Cycle (Refrigeration Machine) by Using the Direct Method from Finite Speed Thermodynamics

2012 ◽  
Vol 463-464 ◽  
pp. 1658-1662 ◽  
Author(s):  
Stoian Petrecu ◽  
Catalina Dobre ◽  
Georgiana Tirca-Dragomirescu ◽  
Monica Costea ◽  
Camelia Stanciu ◽  
...  
Keyword(s):  
Direct Method ◽  
Internal Heat ◽  
Carnot Cycle ◽  
Finite Speed ◽  
Performances Evaluation ◽  
Internal Irreversibility ◽  
Refrigeration Machine

The Direct Method from Finite Speed Thermodynamics is used in order to Determine in a complete analytical format of the COP and consumed Power of a Reversed Cvasi-Carnot Cycle (Refrigeration Machine with vapor) taking into account internal irreversibility generate by: Finite Speed, Friction, Throttling and Internal Heat Loses.

Gas Turbine Performance: New Application and Test Correction Curves

1995 ◽  
Author(s):  
Scott T. Cloyd ◽  
Arthur J. Harris
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Engine Performance ◽  
Exhaust System ◽  
Operating Parameter ◽  
Operating Conditions ◽  
Engine Operation ◽  
Pressure Losses ◽  
System Pressure ◽  
Oil Fuel

The gas turbine industry has adopted the practice of rating engine performance at ISO standard conditions; 15 degrees C, 1.033 ata, 100% methane fuel, and no inlet or exhaust system pressure losses with power output referenced to the generator terminals. (ISO, 1989) While these standards are useful in putting original equipment manufacturers’ (OEM’s) ratings on an equivalent basis it is not likely that an engine would be installed or tested under these types of conditions. To account for variations in engine operating conditions equipment manufacturers’ have utilized performance correction curves to show the influence of changing one operating parameter while holding all others constant. The purpose of this paper is to review the correction curves that are used for initial project application studies, and the variations to the curves that occur when a unit is put into service as a result of the methods used to control engine operation. Sample corrections curves and a brief explanation of the correction curves are presented to illustrate the variations in the curves. The paper also presents a new method for illustrating the influence of fuel heating value and composition on engine performance for natural gas and oil fuel. All data presented is for a single shaft, constant speed gas turbine. Two shaft or three shaft gas turbines will not have these correction curves.

Direct Method to Maximize Net Power Output of Rankine Cycle in Low-Grade Thermal Energy Conversion

2010 ◽  
Vol 2 (2) ◽  
Author(s):  
Faming Sun ◽  
Yasuyuki Ikegami
Keyword(s):  
Energy Conversion ◽  
Thermal Energy ◽  
Power Output ◽  
Direct Method ◽  
Rankine Cycle ◽  
Working Fluid ◽  
Carnot Cycle ◽  
Low Grade ◽  
Thermal Energy Conversion ◽  
Net Power Output

Using ammonia as working fluid, enthalpy equations corresponding to every point in Rankine cycle for low-grade thermal energy conversion (LTEC) are presented by employing curve-fitting method. Analytical equations of Rankine cycle analysis are thus set up. In terms of temperatures of the evaporator and condenser, the equation related to Rankine cycle net power output is then achieved. Furthermore, by using theoretical optimization method, the results of the maximum net power output of a Rankine cycle in LTEC are also reported. This study extends the recent flurry of publications about Rankine cycle power optimization in LTEC, which modified the ideal Rankine cycle to a Carnot cycle by using an average entropic temperature to achieve the theoretical formulas. The proposed method can better reflect the performance of Rankine cycle in LTEC since the current work is mainly based on the direct simulations of every enthalpy points in Rankine cycle. Moreover, the proposed method in this paper is equally applicable for other working mediums, such as water and R134a.

Electronic Trend Monitoring and Exceedance Recording Systems: A Means to Improved Turbine Engine Reliability

1987 ◽  
Author(s):  
Michael G. Moore
Keyword(s):  
Engine Performance ◽  
Current Sensor ◽  
Time Duration ◽  
Turbine Engine ◽  
Power Cycle ◽  
Current Technology ◽  
Real Time Analysis ◽  
Performance Deterioration ◽  
Computer Keyboard ◽  
Engine Reliability

Current technology has yielded engine mountable, compact microprocessor-based recording systems that can record information that will aid in maintenance planning and, thus, yield improved reliability. Among data available are: 1) Trend Recording - revealing deviations from non indicating engine performance deterioration 2) Exceedance Recording - documenting time, date, duration, and severity of exceedances for parameters such as temperature, torque, N1, N2, etc. 3) Power Ratings - power (“hit”) checks are available instantaneously and through the through the exercise of power cycle, go or no-go determination made through real time analysis of current sensor outputs against defined tolerances adjusted to density altitude. 4) Run Data - total time duration within each scale of the operating range for each engine and airframe parameter 5) Cycle Counts - start, power, life fatigue, creep life, and improper cool down cycles are tracked based upon engine manufacturer formulae These engine recorders primarily utilize the existing engine sensors with no effect on signals to established instrument. Current technology allows these engine recorders to be universal to many different engines, with limit thresholds entered at the factory through a computer keyboard.

Influence of Working Fluid Properties on Internal Irreversibility of Power Systems

2010 ◽  
Author(s):  
Gheorghe Dumitrascu ◽  
Aristotel Popescu
Keyword(s):  
Heat Transfer ◽  
Power Systems ◽  
Direct Method ◽  
External Heat ◽  
Working Fluid ◽  
Second Law ◽  
Fluid Properties ◽  
Set Up ◽  
Internal Irreversibility ◽  
Heat Exchanges

Thermodynamic techniques used to analyze and optimize irreversible cycles involve mainly both the exergy model, i.e. second law efficiency, and the entropy generation minimization [1]. This paper presents an appraising comprehensive direct method based on two overall numbers of irreversibility, external and internal ones. These two numbers link the first and second laws of Thermodynamics inside the first law efficiency, called in this paper the irreversible first law efficiency. The number of external irreversibility is the ratio of second law effectiveness of the cycle external heat exchanges, which were set up by relating the real heat exchange of the working fluid with external heat reservoirs, to the ideal completely reversible one, assuming both a heat transfer area tending to infinity and a heat transfer temperature difference tending to zero. The number of internal irreversibility manages the irreversible entropy production along the cycle. This paper includes selected numerical results regarding the internal irreversibility connected to the nature of the working fluid in a Joule-Brayton engine cycle.

Application of the Direct Method to irreversible Stirling cycles with finite speed

2002 ◽  
Vol 26 (7) ◽  
pp. 589-609 ◽  
Author(s):  
S. Petrescu ◽  
M. Costea ◽  
C. Harman ◽  
T. Florea
Keyword(s):  
Direct Method ◽  
Finite Speed

scholarly journals Optimization of Design and Technology of Injector Nozzles in Terms of Minimizing Energy Losses on Friction in Compression Ignition Engines

2021 ◽  
Vol 11 (16) ◽  
pp. 7341
Author(s):  
Jan Monieta ◽  
Lech Kasyk
Keyword(s):  
Surface Condition ◽  
Engine Performance ◽  
Optimization Methods ◽  
Operating Conditions ◽  
Technical State ◽  
Design And Technology ◽  
Design Parameters ◽  
Pressure Losses ◽  
Injection Apparatus

The operation of injection apparatus in self-ignition engines results from the design, manufacturing technology and wear and tear during operation. The technical state of the injector apparatus significantly affects the engine performance, fuel consumption, toxicity and smoke opacity of outlet gases. The most unreliable element of the injection apparatus is the injector nozzle, the quality of which depends on the quality of construction and production, operating conditions and the of the fuels used, etc. One of the design parameters of the injector nozzles, determining the technical state is the geometry of the nozzle holes. An attempt was made to optimize the selection of the dimensions and surface condition of the spray holes to significantly affect the flow properties of the injector nozzles and, consequently, to decide on the size and form of fuel dosed streams to individual cylinders of a self-ignition engine and the quality of fuel atomization. In work, a simulation model was developed, and the pressure losses and the mass fluid of the injected fuel were minimized for selected significant geometric features, taking into account the influence of operating conditions. With the use of Mathematica software, simulation optimization methods and methods based on evolutionary algorithms were elaborated.

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