Influence Of Cycle Parameters Research Articles

Influence of Cycle Parameters on the Overall Efficiency and Fuel Consumption of Aircraft Engines

Influence of Cycle Parameters on the Overall Efficiency and Fuel Consumption of Aircraft Engines

Experimental study on adsorption cooling performance of copper foams curing MIL-101/isobutane double bed system

In this paper, copper foams cured MIL-101(CFCM)/isobutane double-bed adsorption cooling system (ACS) were designed and constructed by using the CFCM unit tube adsorbers. Adsorption cooling characteristic curves of CFCM/isobutane double-bed ACS were studied. Influence of cycle parameters and mass recovery process on the cooling capacity, specific cooling power (SCP) and coefficient of performance (COP) of the CFCM/isobutane double-bed ACS was investigated. Results show that under the conditions of cycle time of 600 s, pre-cooling/pre-heating time of 120 s, condensation temperature of 15°C and hot water temperature of 85°C with the flow rate of 20 L h −1 , and cooling water temperature of 14-16°C with the flow rate of 50 L h −1 , the cooling capacity, SCP and COP of CFCM/isobutane double-bed ACS is 65.20 kJ kg −1 , 108.67 W kg −1 and 0.2260, respectively. Compared with basic cycle, the cooling capacity, SCP and COP of CFCM/isobutane double-bed ACS increases by about 26%, 24% and 22% under mass recovery time of 10 s. The cooling performance of CFCM/isobutane double-bed ACS remains stable after 100 sets consecutive basic cycles and 20 sets mass recovery cycles.

Performance Analysis of SOFC / GT Combined Cycle System with Preheater in Front of Turbine

Based on the SOFC zero-dimensional model, a SOFC turbine combined cycle simulation platform is established. For the SOFC/GT combined cycle system configuration scheme with the preheater placed in front of the turbine, the influence of cycle parameters on system performance is analyzed. The current density-power characteristic curves at different outlet pressures, the fuel flow-efficiency characteristic curve and the turbine inlet temperature curve at different fuel utilization rates were calculated and analyzed separately when different low-temperature and intermediate-temperature combined cycle system configurations were used. The results show that the low-temperature SOFC/GT cycle maintains high-efficiency design conditions with a fuel utilization rate of 0.8-0.85, and the highest efficiency is about 52%. The design working pressure of the medium temperature SOFC/GT cycle is suggested to be 0.4MPa-0.5MPa, and the system efficiency will be higher than 50% when the compression ratio is at 0.8-0.85, and the maximum efficiency is about 64%.

Investigation of temperature effects from LCO2 with different cycle parameters on the coal pore variation based on infrared thermal imagery and low-field nuclear magnetic resonance

Enhanced coalbed methane (ECBM) achieved by injecting liquid carbon dioxide (LCO2) has been proposed and applied in industrial production for decades and has been demonstrated to be an applicable method to boost CBM production. Most of the studies have concentrated on the gas bursting and flooding effect and have rarely focused on the accompanying “freeze–thaw” phenomenon, and the temperature effect of cyclic LCO2 injection on the pore variation of different coals has been partly investigated. In this paper, the influence of cycle parameters, such as cycle number and cycle time, on the pore variation was studied. Infrared thermal imagery (ITI) and low-field nuclear magnetic resonance (NMR) were used to measure the temperature and pore size distribution (PSD) change, respectively. The results show the following: (1) The gas pressure displayed square cyclicity with different cycle time, the temperature of gasified CO2 was almost 248.15 K, and the end and lateral surface temperatures of a core were in the range from 259.35 to 261.85 K, which could cause the water within the pores to freeze with a 9% volume increase, and the fracturing formula was deduced; (2) The relaxation time spectra obtained by different cycle parameters expressed changeable PSD of cores with increasing cycle parameters, and the magnified proportion of bulk water and capillary water, as well the diminished proportion of adsorbed water, all indicated that the increased number of macropores and mesopores formed a larger free volume; (3) The increased total porosity φt and the decreased T2cutoff of six cores with the increasing cycle parameters meant that the larger cycle number could enhance the porosity due to amount of damage accumulation, and the larger cycle time might make the water freeze completely with larger ice swelling stress; (4) There is a polynomial fitting between relative increase ratio Rφ and cycle time, and the fitting coefficients were all higher than 0.99, and the larger the cycle time was, the greater the Rφ(e/t) increment and Rφ(r/t) decrement were. The interval increase ratio Iφe was positively correlated to cycle time without obvious increase behavior; however, the Iφr variation expressed that the greater the cycle number was, the lesser the Iφr with the increasing cycle time was, which indicates that the increasing cycle parameters might help the proportion of connected pores to increase and provide more pathways for permeable fluid; (5) The NMR permeability kSDR of a core increased as the cycle number increased, and the longer cycle time was superior in terms of permeability enhancement.

Performance analysis of the coupled system of heat pump and double stage extraction rankine cycle

This article presented a coupled system cycle (CSC) and the thermodynamic analysis of the CSC was employed, which was combined by the heat pump cycle and double stage extraction Rankine cycle. Taking CO2 and R1234yf as heat pump refrigerants, the influence of cycle parameters on the thermal efficiency of the CSC (ηcsc) was studied by contrast with that of the DSERC, and the performance analysis of the CSC was employed. The results show that increasing the evaporation temperature or decreasing the outlet temperature of gas cooler is beneficial to improve the ηcsc. The optimal compressor discharge pressure of the CSC with CO2 refrigerant is 8.5 MPa, and correspondingly, the maximum COP is about 4.21 and the maximum ηcsc is about 44.56%. Increasing the main steam parameters is beneficial to improve the ηcsc, and the ηcsc is increased and then decreased with the increasing of the steam extraction coefficient. The conclusion is that the CSC has higher thermal efficiency and better performance, which provides a theoretical basis for improving the performance of power plant. © 2017 American Institute of Chemical Engineers Environ Prog, 36: 1856–1863, 2017

Lithium metal stripping/plating mechanisms studies: A metallurgical approach

In the hope of meeting the requirements of long term cyclability for polymer electrolyte metallic lithium battery (LMP) (>600 cycles) and widening the scope of their commercial application (low temperature operation), numerous studies have been devoted to the understanding of the intrinsic limitations of these systems. Dendritic lithium growth is known to result in short circuits upon cycling. Before considering ways to master lithium deposits morphologies, we have embarked on a study aimed at characterizing by mean of Scanning Electron Microscopy (SEM): (1) the texture of metallic lithium (2) the influence of cycling parameters, such as current densities and liquid electrolyte formulation, on lithium stripping mechanisms and (3) the lithium deposits morphologies on various lithium surface states ( in and ex situ prepared through electrochemical means, physical procedures such as polishing and Pulsed Laser Deposition technique). Different lithium stripping processes have been revealed depending on current densities. They lead to various surface defects from which lithium dendrites will preferentially grow upon following Li plating. Furthermore, cycling experiments have highlighted, for the first time, the internal lithium micro-texture. Pursuing this study, we finally shed light on the crucial role of the electrolytic mix formulation and cell pressure on lithium cycling efficiency.

Infrared emissions from turbofans with high aspect ratio nozzles

A mixed flow turbofan is analyzed from the point of view of i.r. emission characteristics. A simple absorption coefficient model of the core flow gas displays the potential effectiveness of high aspect ratio nozzles as a variable in the design of aircraft engine installations for low i.r. signature. The simplicity of the model described and the limited view perspectives used to assess the signature restrict the usefulness of the results to that of guiding preliminary design. In general, more precise solutions are complex and depend on specification of a relatively large number of independent variables to describe the source—seeker geometry, weather, etc. The level of effort to carry out more accurate analysis may be inconsistent with the preliminary design process where simple criteria such as those described here may be sufficient to select the best of several candidate designs. The influence of cycle parameters is assessed using an /zth power dependence of radiation on temperature and a simple mixing model to estimate the core length. The analysis shows that cycle parameters which improve cycle efficiency and thus fuel consumption also reduce i.r. emissions. Bypass ratio near unity gives low i.r. signature for both optically thin and thick spectral regions.

Heat Exchanger Design Considerations for Gas Turbine HTGR Power Plant

The Gas Turbine High Temperature Gas Cooled Reactor (GT-HTGR) power plant combines the existing design HTGR core with a closed-cycle helium gas turbine power conversion system directly in the reactor primary circuit. Unlike open-cycle gas turbines where the recuperative heat exchanger is an optional component, the high cycle efficiency of the nuclear closed-cycle gas turbine is attributable to a high degree to the incorporation of the recuperator (helium-to-helium) and precooler (helium-to-water) exchangers in the power conversion loop. For the integrated plant configuration, a nonintercooled cycle with a high degree of heat recuperation was selected on the basis of performance and economic optimization studies. A recuperator of high effectiveness was chosen because it significantly reduces the optimum pressure ratio (for maximum cycle efficiency), and thus reduces the number of compressor and turbine stages for the low molecular weight, high specific heat, helium working fluid. Heat rejection from the primary system is effected by a helium-to-water precooler, which cools the gas to a low level prior to compression. The fact that the rejection heat is derived from the sensible rather than the latent heat of the cycle working fluid results in dissipation over a wide band of temperature, the high average rejection temperature being advantageous for either direct air cooling or for generation of power in a waste heat cycle. The high heat transfer rates in the recuperator (3100 MWt) and precooler (1895 MWt), combined with the envelope restraints associated with heat exchanger integration in the prestressed concrete reactor vessel, require the use of more compact surface geometries than in contemporary power plant steam generators. Various aspects of surface geometry, flow configuration, mechanical design, fabrication, and integration of the heat exchangers are discussed for a plant in the 1100 MWe class. The influence of cycle parameters on the relative sizes of the recuperator and precooler are also presented. While the preliminary designs included are not meant to represent final solutions, they do embody features that satisfy many of the performance, structural, safety, and economic requirements.