Power and efficiency optimization for combined Brayton and two parallel inverse Brayton cycles. Part 2: Performance optimization

2008 ◽  
Vol 222 (3) ◽  
pp. 405-413 ◽  
Author(s):  
W Zhang ◽  
L Chen ◽  
F Sun
Keyword(s):  
Conversion Efficiency ◽  
Power Output ◽  
Performance Optimization ◽  
Pressure Ratio ◽  
Thermal Conversion ◽  
Design Parameters ◽  
Flow Area ◽  
Compressor Inlet ◽  
Mass Flowrate ◽  
Top Cycle

The power and efficiency of the open combined Brayton and two parallel inverse Brayton cycles are analysed and optimized based on the model established using finite-time thermodynamics in Part 1 of the current paper by adjusting the compressor inlet pressure of the two parallel inverse Brayton cycles, the mass flowrate and the distribution of pressure losses along the flow path. It is shown that the power output has a maximum with respect to the compressor inlet pressures of the two parallel inverse Brayton cycles, the air mass flowrate or any of the overall pressure drops, and the maximized power output has an additional maximum with respect to the compressor pressure ratio of the top cycle. The power output and the thermal conversion efficiency have the maximum values when the mass flowrates of the first and the second inverse Brayton cycles are the same. When the optimization is performed with the constraints of a fixed fuel flowrate and the power plant size, the power output and thermal conversion efficiency can be maximized again by properly allocating the fixed overall flow area among the compressor inlet of the top cycle and the turbine outlets of the two parallel inverse Brayton cycles. The numerical examples show the effects of design parameters on the power output and heat conversion efficiency.

Performance optimization for an open-cycle gas turbine power plant with a refrigeration cycle for compressor inlet air cooling. Part 2: Power and efficiency optimization

2009 ◽  
Vol 223 (5) ◽  
pp. 515-522 ◽  
Author(s):  
W Zhang ◽  
L Chen ◽  
F Sun
Keyword(s):  
Conversion Efficiency ◽  
Power Output ◽  
Thermal Conversion ◽  
Air Cooling ◽  
Refrigeration Cycle ◽  
Pressure Losses ◽  
Compressor Inlet ◽  
Open Cycle ◽  
Net Power Output ◽  
Gas Turbine Power Plant

The power and efficiency of the open cycle gas turbine power plant with a refrigeration cycle for compressor inlet air cooling with pressure drop irreversibilities are optimized based on the model established using finite time thermodynamics in Part 1 of this article by adjusting the mass flowrate (or the distribution of pressure losses along the flow path). It is shown that there are optimal air mass flowrates (or the distribution of pressure losses along the flow path) that maximize the net power output, and the maximum has additional maximum with respect to the compressor overall pressure ratio. When optimization is performed with the constraints of the fixed fuel flow and the plant size, the net power output and the thermal conversion efficiency of the cycle can be maximized again by properly allocating the fixed flow area among the compressor inlet and the power turbine outlet. The numerical examples show the effects of design parameters on the power output and heat conversion efficiency. The net power output and the thermal conversion efficiency are improved by using the refrigeration cycle for compressor air inlet cooling.

Power and efficiency optimization for combined Brayton and two parallel inverse Brayton cycles. Part 1: Description and modelling

2008 ◽  
Vol 222 (3) ◽  
pp. 393-403 ◽  
Author(s):  
L Chen ◽  
W Zhang ◽  
F Sun
Keyword(s):  
Pressure Drop ◽  
Power Output ◽  
Pressure Ratio ◽  
Current Paper ◽  
Working Fluid ◽  
Relative Pressure ◽  
Pressure Drops ◽  
Compressor Inlet ◽  
Flow Resistances ◽  
Top Cycle

A thermodynamic model for open combined Brayton and two parallel inverse Brayton cycles is established using finite-time thermodynamics in part A of the current paper. The flow processes of the working fluid with the pressure drops of the working fluid and the size constraints of the real power plant are modelled. There are 17 flow resistances encountered by the gas stream for the combined Brayton and two parallel inverse Brayton cycles. Six of these, the friction through the blades and vanes of the compressors and the turbines, are related to the isentropic efficiencies. The remaining flow resistances are always present because of the changes in flow cross-section at the compressor inlet of the top cycle, combustion inlet and outlet, turbine outlet of the top cycle, turbine outlets of the bottom cycle, heat exchanger inlets, and compressor inlets of the bottom cycle. These resistances control the air flowrate and the net power output. The relative pressure drops associated with the flow through various cross-sectional areas are derived as functions of the compressor inlet relative pressure drop of the top cycle. The analytical formulae about the relations between power output, thermal conversion efficiency, and the compressor pressure ratio of the top cycle are derived with the 17 pressure drop losses in the intake, compression, combustion, expansion, and flow process in the piping, the heat transfer loss to ambient, the irreversible compression and expansion losses in the compressors and the turbines, and the irreversible combustion loss in the combustion chamber. The performance of the model cycle is optimized by adjusting the compressor inlet pressure of the bottom cycles, the mass flowrate and the distribution of pressure losses along the flow path in part B of the current paper.

scholarly journals Modeling and Performance Optimization of an Irreversible Two-Stage Combined Thermal Brownian Heat Engine

Entropy ◽  
2021 ◽  
Vol 23 (4) ◽  
pp. 419
Author(s):  
Congzheng Qi ◽  
Zemin Ding ◽  
Lingen Chen ◽  
Yanlin Ge ◽  
Huijun Feng
Keyword(s):  
Power Output ◽  
Performance Optimization ◽  
External Load ◽  
Thermal Contact ◽  
Heat Engine ◽  
Design Parameters ◽  
Load Effect ◽  
Heat Engines ◽  
Heat Leakage ◽  
Steady Current

Based on finite time thermodynamics, an irreversible combined thermal Brownian heat engine model is established in this paper. The model consists of two thermal Brownian heat engines which are operating in tandem with thermal contact with three heat reservoirs. The rates of heat transfer are finite between the heat engine and the reservoir. Considering the heat leakage and the losses caused by kinetic energy change of particles, the formulas of steady current, power output and efficiency are derived. The power output and efficiency of combined heat engine are smaller than that of single heat engine operating between reservoirs with same temperatures. When the potential filed is free from external load, the effects of asymmetry of the potential, barrier height and heat leakage on the performance of the combined heat engine are analyzed. When the potential field is free from external load, the effects of basic design parameters on the performance of the combined heat engine are analyzed. The optimal power and efficiency are obtained by optimizing the barrier heights of two heat engines. The optimal working regions are obtained. There is optimal temperature ratio which maximize the overall power output or efficiency. When the potential filed is subjected to external load, effect of external load is analyzed. The steady current decreases versus external load; the power output and efficiency are monotonically increasing versus external load.

scholarly journals Thermodynamics performance optimization of a hybrid solar gas turbine power plant in Colombia

2022 ◽  
Vol 2163 (1) ◽  
pp. 012004
Author(s):  
F Moreno-Gamboa ◽  
J C Acevedo-Paez ◽  
D Sanin-Villa
Keyword(s):  
Power Plant ◽  
Solar Radiation ◽  
Gas Turbine ◽  
Power Output ◽  
Performance Optimization ◽  
Pressure Ratio ◽  
Direct Solar Radiation ◽  
Performance Point ◽  
Overall Efficiency ◽  
Gas Turbine Power Plant

Abstract A thermodynamic model is presented for evaluation of a solar hybrid gas-turbine power plant. The model uses variable ambient temperature and estimates direct solar radiation at different day times. The plant is evaluated in Barranquilla, Colombia, with a solar concentration system and a combustion chamber that burns natural gas. The hybrid system enables to maintain almost constant the power output throughout day. The model allows optimizing the different plant parameters and evaluating maximum performance point. This work presents pressure ratio ranges where the maximum values of overall efficiency, power output, thermal engine efficiency and fuel conversion rate are found. The study is based on the environmental conditions of Barranquilla, Colombia. The results obtained shows that optimum pressure ratio range for power output and overall efficiency is between 6.4 and 8.3, when direct solar radiation its maximum at noon. This thermodynamic analysis is necessary to design new generations of solar thermal power plants.

Investigation of variable geometry orifice design for improving centrifugal compressor low-end performance and stable operating range

2021 ◽  
pp. 095441002110476
Author(s):  
Ben Zhao ◽  
Qingjun Zhao ◽  
Xiaorong Xiang ◽  
Wei Zhao ◽  
Jianzhong Xu
Keyword(s):  
Numerical Simulations ◽  
Centrifugal Compressor ◽  
Control Device ◽  
Design Parameters ◽  
Variable Geometry ◽  
Flow Area ◽  
Stall Margin ◽  
Setting Angle ◽  
Compressor Inlet ◽  
Two Parameters

Active control of the inlet flow area in a centrifugal compressor is a method to improve compressor aerodynamic performance and stall margin. As a core part of the area control device, the variable geometry orifice is investigated and its two key design parameters are analyzed in detail, the setting angle of the orifice with respect to the shroud casing and the radial height of the orifice to the shroud casing from the orifice inner rim. This paper proposes a physics-based equation that describes the relationship of the two parameters with compressor mass flow rate and then validates the equation using numerical simulations. As far as the setting angle, the physics-based equation suggests not to be larger than 90°. The numerical results not only validate the physics-based equation but also show the most optimal angle of 78°. In terms of the orifice height, both the physics-based equation and the numerical simulations suggest an active height control of orifice in the compressor inlet duct.

scholarly journals Ultrashort Nacelles for Low Fan Pressure Ratio Propulsors

2014 ◽  
Vol 137 (2) ◽  
Author(s):  
Andreas Peters ◽  
Zoltán S. Spakovszky ◽  
Wesley K. Lord ◽  
Becky Rose
Keyword(s):  
Mach Number ◽  
Pressure Ratio ◽  
Design Tool ◽  
Operating Conditions ◽  
Design Parameters ◽  
Flow Distortion ◽  
Flow Area ◽  
Propulsive Efficiency ◽  
Flow Acceleration ◽  
Fuel Burn

As the propulsor fan pressure ratio (FPR) is decreased for improved fuel burn, reduced emissions and noise, the fan diameter grows and innovative nacelle concepts with short inlets are required to reduce their weight and drag. This paper addresses the uncharted inlet and nacelle design space for low-FPR propulsors where fan and nacelle are more closely coupled than in current turbofan engines. The paper presents an integrated fan–nacelle design framework, combining a spline-based inlet design tool with a fast and reliable body-force-based approach for the fan rotor and stator blade rows to capture the inlet–fan and fan–exhaust interactions and flow distortion at the fan face. The new capability enables parametric studies of characteristic inlet and nacelle design parameters with a short turn-around time. The interaction of the rotor with a region of high streamwise Mach number at the fan face is identified as the key mechanism limiting the design of short inlets. The local increase in Mach number is due to flow acceleration along the inlet internal surface coupled with a reduction in effective flow area. For a candidate short-inlet design with length over diameter ratio L/D = 0.19, the streamwise Mach number at the fan face near the shroud increases by up to 0.16 at cruise and by up to 0.36 at off-design conditions relative to a long-inlet propulsor with L/D = 0.5. As a consequence, the rotor locally operates close to choke resulting in fan efficiency penalties of up to 1.6% at cruise and 3.9% at off-design. For inlets with L/D < 0.25, the benefit from reduced nacelle drag is offset by the reduction in fan efficiency, resulting in propulsive efficiency penalties. Based on a parametric inlet study, the recommended inlet L/D is suggested to be between 0.25 and 0.4. The performance of a candidate short inlet with L/D = 0.25 was assessed using full-annulus unsteady Reynolds-averaged Navier–Stokes (RANS) simulations at critical design and off-design operating conditions. The candidate design maintains the propulsive efficiency of the baseline case and fuel burn benefits are conjectured due to reductions in nacelle weight and drag compared to an aircraft powered by the baseline propulsor.

Analysis of Lithium-Ion Battery Cap Structure and Characterization of Venting Parameters

2020 ◽  
Author(s):  
Weisi Li ◽  
K. R. Crompton ◽  
Christopher Hacker ◽  
Jason Ostanek
Keyword(s):  
Lithium Ion Battery ◽  
Discharge Coefficient ◽  
Pressure Ratio ◽  
Lithium Ion ◽  
Storage Device ◽  
Flow Area ◽  
Open Flow ◽  
Wide Range ◽  
Experimental Apparatus ◽  
Mass Flowrate

Abstract Lithium-ion batteries are a proven energy storage device which continue to gain market share across a wide range of applications. However, the safety of these devices is still a major factor in many applications. In failures which result in thermal runaway, a series of chemical reactions are initiated which produce a large quantity of gas and heat. The pressure and temperature inside the battery rise sharply and may cause fire or explosion. The lithium-ion battery vent cap is a key safety device used in 18650 format cells to prevent an energetic failure of the metal casing. In this paper, the cap structure and venting parameters of three cap designs are analyzed. The venting parameters investigated were the open flow area and discharge coefficient. Open flow area through different components of the cap assembly were measured using 3D x-ray scans. A new experimental apparatus was used to measure mass flowrate and pressure ratio across the battery cap, which allowed calculation of discharge coefficient. Results indicate that discharge coefficients follow the same trend as a sharp-edged orifice, albeit at a reduced magnitude due to the more tortuous flow path. A semi-empirical model is proposed to simulate mass flow through the battery cap.

Optimization of an Oxyfuel Combined Cycle Regarding Performance and Complexity Level

2013 ◽  
Author(s):  
Adrian Dahlquist ◽  
Magnus Genrup ◽  
Mats Sjoedin ◽  
Klas Jonshagen
Keyword(s):  
Gas Turbine ◽  
Flue Gas ◽  
State Of The Art ◽  
Pressure Ratio ◽  
Combined Cycle ◽  
Design Parameters ◽  
Inlet Temperature ◽  
Optimum Pressure ◽  
Compressor Inlet ◽  
Cooling Model

The aim of this paper is to establish and motivate the design parameters of a 125 MW Oxyfuel Combined Cycle (OCC) also referred to as the Semi-Closed Oxyfuel-Combusted Combined Cycle (SCOC-CC). This paper proposes a compatible OCC that does not include any unconventional features, beyond what is state-of-the-art in gas turbine technology today. Such features could challenge the feasibility to bring the concept to the market in a reasonable time. The OCC requires a higher pressure ratio compared to a conventional combined cycle in order to achieve exhaust conditions that fit the design of the bottoming cycle. However, a high gas turbine pressure ratio increases the complexity of the machine and must be weighted against the gain in efficiency. The OCC gas turbine is modeled using a cooling model which keeps the metal temperature of all cooled turbine stages constant while seeking the optimum pressure ratio. As the cycle is semi-closed the compressor inlet temperature is a design parameter: it is shown that there is an efficiency optimum clearly in the range of what is normally achievable. As the gas properties of the OCC flue gas differ from the conventional plant, the effects of this on the HRSG design are explored.

Thermodynamic Optimization of a Gas Turbine Power Plant With Pressure Drop Irreversibilities

1998 ◽  
Vol 120 (3) ◽  
pp. 233-240 ◽  
Author(s):  
V. Radcenco ◽  
J. V. C. Vargas ◽  
A. Bejan
Keyword(s):  
Power Plant ◽  
Gas Turbine ◽  
Flow Rate ◽  
Power Output ◽  
Pressure Ratio ◽  
Plant Size ◽  
Fuel Flow Rate ◽  
Flow Area ◽  
Fuel Flow ◽  
Gas Turbine Power Plant

In this paper we show that the thermodynamic performance of a gas turbine power plant can be optimized by adjusting the flow rate and the distribution of pressure losses along the flow path. Specifically, we show that the power output has a maximum with respect to the fuel flow rate or any of the pressure drops. The maximized power output has additional maxima with respect to the overall pressure ratio and overall temperature ratio. When the optimization is performed subject to a fixed fuel flow rate, and the power plant size is constrained, the power output and efficiency can be maximized again by properly allocating the fixed total flow area among the compressor inlet and the turbine outlet.

A Study of Existing Multistage Transonic Axial Compressor Design for Surge Margin Improvement

2013 ◽  
Author(s):  
Baljeet Kaur ◽  
Nitin B. Balsaraf ◽  
Ajay Pratap
Keyword(s):  
Pressure Ratio ◽  
Axial Flow ◽  
Design Procedure ◽  
Rotating Stall ◽  
Design Parameters ◽  
Stable Operation ◽  
Flow Area ◽  
Transonic Compressor ◽  
Surge Margin ◽  
Design Techniques

The design of multistage axial flow compressors has been revolutionised in recent years by the development of three dimensional multistage viscous calculations (CFD) and the availability of the computational power to allow these methods to be used extensively in design process. Such a multistage turbomachinery was used to redesign the existing three stage transonic compressor for improved aerodynamic performance in terms of SM limit. The redesign activity of compressor configuration was carried out as surge margin obtained with hardware testing of existing machinery was not sufficient to meet the desired design goals. The higher limit of surge margin in accordance with design specification is required to maintain the successful and stable operation of aircraft engine. As at stall point of compressor, aerodynamic instabilities would be initiated resulting surge or rotating stall which potentially leading to a complete mechanical failure of the compression system as well as of the whole engine. Maximizing the SM of multistage compressors is particularly a complex process especially alongwith achieving higher efficiency. Outlined in this paper are the details of how advanced design techniques were incorporated using traditional 2D and CFD methods into redesign activities for compressor performance improvement. The approach used in this work was to modify compressor annulus flowpath and rotor and stator blade geometries based on output of 2D calculations and 3D N-S analysis for SM enhancement of existing design. While carrying out redesign activities for compressor, the constraints of retaining existing inlet and outlet flow area, axial length as well as design parameters i.e. inlet mass flow, rotational speed and operating point pressure ratio were taken care. The advanced design techniques like 3D blading, wide chord blade performance and many others were studied in detailed manner for incorporating them into compressor redesign procedure. Simultaneous resigned compressor configuration based on in-house design procedure showed improvement of SM by 17% at design speed with maintaining mentioned design constraints. Subsequently, the detailed analysis was also performed at off design speeds to have satisfactory performance.

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