The Optimal Intercooling of Compressors by a Finite Number of Intercoolers

1992 ◽  
Vol 114 (3) ◽  
pp. 255-260 ◽  
Author(s):  
P. Vadasz ◽  
D. Weiner
Keyword(s):  
Finite Number ◽  
Pressure Ratio ◽  
Optimal Number ◽  
Specific Work ◽  
Relative Pressure ◽  
Correction Factors ◽  
Isothermal Compression ◽  
Compression Process ◽  
Pressure Losses ◽  
The Ideal

Intercooling of compressors is necessary for an efficient process. Among the optimal criteria required, minimizing the compression-specific work is one of the more commonly used. Upon ideal conditions, such a criterion leads to an isothermal compression whose importance is purely theoretical, since it requires an infinite number of intercoolers. In this paper the evaluation of correction factors to the well-known relations of the optimal location of intercoolers in a compression process and its corresponding work of compression was performed for a general compression process which accounts for pressure losses and other irreversibilities as well. As a result of including the pressure losses in the equations, a finite number of intercoolers is evaluated as optimum. The results, although qualitatively expected, show a quantitative nonempirical figure of the optimal number of intercoolers as a function of the terminal pressure ratio and as a function of the relative pressure losses. The ideal conditions are evaluated and verified as a particular case by assuming no pressure losses. In practice, these results can be used as an upper limit for technoeconomical optimization processes.

scholarly journals On the Optimal Location and Number of Intercoolers in a Real Compression Process

1988 ◽  
Author(s):  
Peter Vadasz ◽  
Jossef Pugatsch ◽  
Dan Weiner
Keyword(s):  
Optimal Number ◽  
Optimal Location ◽  
Final Decision ◽  
Specific Work ◽  
Compression Process ◽  
Pressure Losses ◽  
Ideal Process ◽  
Partial Criterion ◽  
Economic Criteria ◽  
The Ideal

In this paper the optimal location and number of intercoolers in a real compression process, including pressure losses, is derived by minimizing the compression specific work. Consequently the series of intermediate pressure values where the system intercoolers should be located is evaluated. As a result a solution different from the classical-isothermal compression process is obtained. The ideal process is evaluated and verified as a particular case by assuming no pressure losses. In reality, minimizing the compression work is only a partial criterion of optimization and the final decision regarding the optimal number of intercoolers should be obtained by using techno-economic criteria.

scholarly journals Analyses of a High Pressure Ratio Intercooled Direct Brayton Helium Gas Turbine Cycle for Generation IV Reactor Power Plants

2016 ◽  
Vol 3 (1) ◽  
Author(s):  
A. Gad-Briggs ◽  
P. Pilidis ◽  
T. Nikolaidis
Keyword(s):  
Power Plants ◽  
Pressure Ratio ◽  
Business Case ◽  
Sensitivity Analyses ◽  
Critical Parameters ◽  
Processing Plant ◽  
Specific Work ◽  
Pressure Losses ◽  
Cycle Efficiency ◽  
Very High

The intercooled cycle (IC) as an alternative to the simple cycle recuperated (SCR) and intercooled cycle recuperated (ICR) is yet to be fully analyzed for the purpose of assessing its viability for utilization within Generation IV nuclear power plants (NPPs). Although the benefits are not explicitly obvious, it offers the advantage of a very high overall pressure ratio (OPR) in the absence of a recuperator. Thus, the main objective of this study is to analyze various pressure ratio configurations, the effects of varying pressure ratio including sensitivity analyses of component efficiencies, ambient temperature, component losses and pressure losses on cycle efficiency, and specific work of the IC, including comparison with the SCR and ICR. Results of comparison between the IC and the SCR and ICR derived that the cycle efficiencies are greater than the IC by ∼4% (SCR) and ∼6% (ICR), respectively. However, the pressure losses for IC are lower when compared with the SCR and ICR. Nonetheless, heat from the turbine exit temperature of the IC can be used in a processing plant including the possibility of higher turbine entry temperatures (TETs) to significantly increase the cycle efficiency in a bid to justify the business case. The analyses intend to bring to attention an alternative to current cycle configurations for the gas-cooled fast reactors (GFRs) and very-high-temperature reactors (VHTRs), where helium is the coolant. The findings are summarized by evaluating the chosen pressure ratio configurations against critical parameters and detailed comparison with the SCR and ICR.

Modified Brayton Cycles Utilizing Alcohol Fuels

1982 ◽  
Vol 104 (2) ◽  
pp. 341-348 ◽  
Author(s):  
M. F. Bardon
Keyword(s):  
Thermal Efficiency ◽  
Gas Turbines ◽  
Pressure Ratio ◽  
Inlet Temperature ◽  
Specific Work ◽  
Brayton Cycle ◽  
Compression Process ◽  
Turbine Inlet Temperature ◽  
Optimum Pressure ◽  
Alcohol Fuels

It is already well known that alcohols can be burned in open-cycle gas turbines by direct firing in the combustor. This paper demonstrates however, that there are significant improvements in thermal efficiency possible by modifying the manner in which alcohols are used in Brayton cycle engines. It is shown that injection of the alcohol during the compression process can materially improve both thermal efficiency and specific work because of the intercooling effect of evaporation. Calculations are given which demonstrate the improvement theoretically possible at representative values of peak turbine inlet temperature. It is also shown that the optimum pressure ratio for both regenerated and unregenerated cycles is different when such compressor evaporative intercooling is used rather than simply injecting the fuel into the combustor.

Supersonic Flow With Variable Specific Heat

1952 ◽  
Vol 19 (1) ◽  
pp. 57-62
Author(s):  
F. P. Durham
Keyword(s):  
Shock Wave ◽  
Specific Heat ◽  
Total Pressure ◽  
Pressure Ratio ◽  
Correction Factors ◽  
One Dimensional ◽  
Specific Heats ◽  
Flow Through ◽  
Total Pressure Ratio ◽  
The Ideal

Abstract Formulas are developed for stagnation conditions and one-dimensional flow through shock waves, including Rankine-Hugoniot values, taking into account the variation of the specific heat of air with temperature by means of the concept of mean specific heats. These formulas are reduced to correction factors that may be applied to the widely used constant specific-heat formulas up to a Mach number of 7. The corrections involved are appreciable in the case of the density change through a shock wave and for the total pressure ratio across a shock wave, as well as for stagnation pressures and temperatures. The limitations imposed by the deviation of a gas at high pressure from the ideal equation of state, relaxation time, and dissociation are discussed.

A Parametric Analysis Microcomputer Model for Evaluating the Thermodynamic Performance of a Reciprocating Brayton Cycle Engine

1989 ◽  
Vol 111 (4) ◽  
pp. 587-594 ◽  
Author(s):  
G. A. Tsongas ◽  
T. J. White
Keyword(s):  
Pressure Ratio ◽  
Piston Compressor ◽  
Significant Loss ◽  
Maximum Temperature ◽  
Specific Work ◽  
Operating Characteristics ◽  
Turbine Engine ◽  
Pressure Losses ◽  
Thermodynamic Performance ◽  
Input Parameters

A novel Brayton open-cycle engine is under development. It operates similarly to a gas turbine engine, but uses reciprocating piston compressor and expander components. The design appears to have a number of advantages, including multifuel capability, the potential for lower cost, and the ability to be scaled to small sizes without significant loss in efficiency. An interactive microcomputer model has been developed that analyzes the thermodynamic performance of the engine. The model incorporates all the important irreversibilities found in piston devices, including heat transfer, mechanical friction, pressure losses, and mass loss and recirculation. There are 38 input parameters to the model. Key independent operating parameters are maximum temperature, compressor rpm, and pressure ratio. While the development of the model and its assumptions are outlined in this paper, the emphasis is on model applications. The model has demonstrated itself to be a powerful tool for evaluating engine thermal efficiency, net specific work, and power. It can be used to analyze the performance of individual engine designs, to generate performance “maps” that graphically represent engine operating characteristics, and to perform sensitivity analysis to compare the relative effects of various input parameters. Examples of each of these model applications are discussed. Recommendations for model improvements and for further engine development work are made. The need for better experimental data to verify some critical model assumptions is stressed.

Criteria and Methods for Reliable Three-Dimensional Image Reconstruction

1974 ◽  
Vol 32 ◽  
pp. 330-331
Author(s):  
R. A. Crowther
Keyword(s):  
Image Reconstruction ◽  
Finite Number ◽  
Density Distribution ◽  
Electron Micrographs ◽  
Mathematical Problem ◽  
Three Dimensional ◽  
Ideal Case ◽  
Dimensional Image ◽  
General Object ◽  
The Ideal

The reconstruction of a three-dimensional image of a specimen from a set of electron micrographs reduces, under certain assumptions about the imaging process in the microscope, to the mathematical problem of reconstructing a density distribution from a set of its plane projections.In the absence of noise we can formulate a purely geometrical criterion, which, for a general object, fixes the resolution attainable from a given finite number of views in terms of the size of the object. For simplicity we take the ideal case of projections collected by a series of m equally spaced tilts about a single axis.

Numerical Modeling of Heat Transfer and Pressure Losses for Uncooled Gas Turbine Blade Tip: Effect of Tip Clearance and Tip Geometry

2007 ◽  
Author(s):  
Lamyaa A. El-Gabry
Keyword(s):  
Heat Transfer ◽  
Mach Number ◽  
Gas Turbine ◽  
Computational Study ◽  
Numerical Models ◽  
Pressure Ratio ◽  
Tip Clearance ◽  
Pressure Losses ◽  
Blade Tip ◽  
Exit Mach Number

A computational study has been performed to predict the heat transfer distribution on the blade tip surface for a representative gas turbine first stage blade. CFD predictions of blade tip heat transfer are compared to test measurements taken in a linear cascade, when available. The blade geometry has an inlet Mach number of 0.3 and an exit Mach number of 0.75, pressure ratio of 1.5, exit Reynolds number based on axial chord of 2.57×106, and total turning of 110 deg. Three blade tip configurations were considered; they are flat tip, a full perimeter squealer, and an offset squealer where the rim is offset to the interior of the tip perimeter. These three tip geometries were modeled at three tip clearances of 1.25, 2.0, and 2.75% of blade span. The tip heat transfer results of the numerical models agree fairly well with the data and are comparable to other CFD predictions in the open literature.

The Effects of Ambient Conditions on Gas Turbine Emissions—Generalized Correction Factors

1978 ◽  
Vol 100 (4) ◽  
pp. 640-646 ◽  
Author(s):  
P. Donovan ◽  
T. Cackette
Keyword(s):  
Gas Turbine ◽  
Pressure Ratio ◽  
Turbine Engines ◽  
Inlet Temperature ◽  
Gas Turbine Engines ◽  
Correction Factors ◽  
Oxides Of Nitrogen ◽  
Ambient Conditions ◽  
Nitrogen Emission ◽  
Wide Range

A set of factors which reduces the variability due to ambient conditions of the hydrocarbon, carbon monoxide, and oxides of nitrogen emission indices has been developed. These factors can be used to correct an emission index to reference day ambient conditions. The correction factors, which vary with engine rated pressure ratio for NOx and idle pressure ratio for HC and CO, can be applied to a wide range of current technology gas turbine engines. The factors are a function of only the combustor inlet temperature and ambient humidity.

Monte Carlo Optimization of Two-Stage Cascade R134A Refrigeration System With Flash Chamber

2008 ◽  
Author(s):  
Yousef M. Abdel-Rahim
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Method ◽  
Pressure Ratio ◽  
Volume Ratio ◽  
Heat Rate ◽  
Cycle Performance ◽  
Specific Work ◽  
Refrigeration System ◽  
Two Stage ◽  
Monte Carlo Optimization

Present paper studies the optimal characteristics of the two-stage cascade R134A refrigeration system with flash and mixing chambers over its operating ranges of all cycle controlling parameters. The COP, total heat rate in Qin, total work rate in Win and second law efficiency ηII are used as cycle performance parameters. Compared to the practically-limited other rate-based optimization methods and to other experimentally-optimized specific cases of cycle parameters, the application of Monte Carlo method has proved to be very effective for optimizing the cycle performance in its global sense over all cycle controlling parameters. Correlations relating performance and cycle controlling parameters are presented and discussed. Study shows that COP of the cycle can reach a value of 8 at intermediate pressure P2 of about 200 kPa, and a maximum value of 9.92 at about 370 kPa and 720 kPa, beyond which COP goes as low as 4.2. P2 alone has no significant effect on Qin, Win and ηII unless values of other controlling parameters are specified. Values of Qin, Win and ηII can reach as high as 94 kW, 23 kW and 0.85 and as low as 6.8 kW, 1.1 kW and 0.57 respectively depending on other cycle parameters. Neither pressure ratio nor volume ratio of the HP compressor has any effect on Qin, Win or ηII. However, the ratio of inlet to exit temperatures of the condenser has the greatest effect on both ηII and the volumetric specific work of the HP compressor, which is about double the value of the volumetric specific work of the LP compressor. Study shows an almost linear relationship between the two mass flow rates in the upper and lower loops of the cycle, where its value in the lower LP loop is about 75% that in the upper HP loop. Findings of the present work as well as the elaborate application of Monte Carlo method to real cycles can greatly open the way for reducing the trade-off design methods currently used in developing such systems as well as direct the useful experimentations and assessment of such designed systems.

Paper 3: Steady Flow Tests on Twin Poppet Valves

1967 ◽  
Vol 182 (4) ◽  
pp. 126-133 ◽  
Author(s):  
W. A. Woods
Keyword(s):  
Steady Flow ◽  
Pressure Loss ◽  
Pressure Ratio ◽  
Effective Area ◽  
Valve Lift ◽  
Cylinder Wall ◽  
Large Area ◽  
Pressure Losses ◽  
Flow Through ◽  
Poppet Valves

This paper presents the results of an experimental investigation of steady flow through a pair of exhaust poppet valves. An account is given of the gas exchange process on engines which use poppet valves and the reason why pressure losses should be kept to a minimum is explained. Tests carried out on the cylinder head of a uniflow two-stroke cycle engine are described following a brief description of the apparatus used. The results of a simple analysis of incompressible flow are also given. It is shown that the two previous models of flow through a valve, namely the sudden enlargement and constant static pressure, both give unrealistic pressure losses for large area ratios, i.e. at high valve lifts. A new model is introduced which leads to realistic pressure losses at small and large area ratios, i.e. at low and high valve lifts. Effective areas for the present tests are calculated on the basis of the constant pressure model, and details of calculation of pressure losses are outlined. The blockage effect caused by placing the exhaust valves near the cylinder wall is given in the discussion of the test results. This is zero for 0 < l/d < 0·08, but reaches a maximum blockage of 10 per cent at l/d = 0·28. With unrestricted twin valves the effective area is about twice that of a single valve up to l/d = 0·18 with a progressively larger effective area at lifts up to 13 per cent higher at l/d = 0·4. A comparison is also made with other data readily available. The pressure losses determined from the tests were analysed using a parameter derived in the simple theory. The parameter used is found to be almost independent of pressure ratio and the results are presented by means of this pressure loss parameter as a function of valve lift. The representation provides a quantitative method of comparing the performance of a given configuration of valve and port. On this basis the twin poppet valves are shown to give a slightly higher pressure loss than a single valve.

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