isentropic efficiency
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Energies ◽  
2022 ◽  
Vol 15 (1) ◽  
pp. 309
Author(s):  
Jung-Bo Sim ◽  
Se-Jin Yook ◽  
Young Won Kim

The organic Rankine cycle (ORC) is a thermodynamic cycle in which electrical power is generated using an organic refrigerant as a working fluid at low temperatures with low-grade enthalpy. We propose a turbine embedded in a generator (TEG), wherein the turbine rotor is embedded inside the generator rotor, thus simplifying turbine generator structure using only one bearing. The absence of tip clearance between the turbine rotor blade and casing wall in the TEG eliminates tip clearance loss, enhancing turbine efficiency. A single-stage axial-flow turbine was designed using mean-line analysis based on physical properties, and we conducted a parametric study of turbine performance, and predicted turbine efficiency and power using the tip clearance loss coefficient. When the tip clearance loss coefficient was applied, turbine isentropic efficiency and power were 0.89 and 20.42 kW, respectively, and ORC thermal efficiency was 4.81%. Conversely, the isentropic efficiency and power of the turbine without the tip clearance loss coefficient were 0.94 and 22.03 kW, respectively, and the thermal efficiency of the ORC was 5.08%. Therefore, applying the proposed TEG to the ORC system simplifies the turbine generator, while improving ORC thermal efficiency. A 3D turbine generator assembly with proposed TEG structure was also proposed.


2021 ◽  
pp. 1-41
Author(s):  
Syamak Pazireh ◽  
Jeff Defoe

Abstract Despite advances in computational power, the cost of time-accurate flows in axial compressor and fan stages with spatially non-uniform inflow is still too high for design-stage use in industry. Body force modeling reduces the computation time to practical levels, mainly by reducing the problem to a steady one. These computations are important to determine efficiency penalties associated with non-uniform inflows. Previous studies of body force methods have, in most cases, relied on computations with the presence of the blades to calibrate loss models. In some recent studies, uncalibrated models have been used, but such models can drop off in accuracy at conditions where separation would occur on the blade surfaces. In this paper, a neural network-based loss model introduced in a recent paper by the authors is implemented for NASA rotor 67 for both uniform and non-uniform inflow conditions. For uniform inflow, the spanwise trend of entropy variation is generally captured with the new body force model. Although there are discrepancies at some span fractions, the present model generally predicts the compressor's isentropic efficiency to within 3% compared to bladed RANS simulations. For non-uniform inflow, we consider a stagnation pressure profile representative of boundary layer ingestion. The results show that the region of maximum entropy generation is captured by the present model and the prediction of isentropic efficiency penalty due to the non-uniform inflow is only 0.2 points less than that determined from bladed computations.


2021 ◽  
Vol 1207 (1) ◽  
pp. 012013
Author(s):  
Jiachi Yao ◽  
Chao Liu ◽  
Yunfeng Jin ◽  
Gaofeng Deng ◽  
Yunlong Guan ◽  
...  

Abstract It is extremely important to monitor the status of gas turbine to ensure its safe and reliable operation. In this work, the variation trend of isentropic efficiency of compressor is analysed based on the measured data of F-class heavy-duty gas turbine in practical industrial application. The actual measured data of F-class heavy-duty gas turbine includes the data under start-stop and unstable working conditions, which cannot be directly used for calculation and analysis. To solve this problem, the data selection rules are designed and determined according to the operating conditions of gas turbine to select the data under effective working state. The isentropic efficiency of compressor is calculated based on the selected data. Then the forecasting effects of four forecasting methods on the variation trend of isentropic efficiency of compressor are studied. Four indexes, namely, symmetric mean absolute percentage error (SMAPE), mean absolute percentage error (MAPE), root mean square error (RMSE), and similarity (SIM) values are utilized to evaluate the forecasting accuracy. The research results indicate that the Adaptive Neuro-Fuzzy Inference System (ANFIS) method has better forecasting effect than Autoregressive Integrated Moving Average (ARIMA), Vector Autoregression (VAR) and Nonlinear Autoregression Neural Network (NARNN) for this F-class heavy-duty gas turbine. Through the ANFIS method, the SIM up to 96.77%, the SMAPE and MAPE are less than 0.1, and the RMSE is only 0.1157. Therefore, the ANFIS method is suitable for forecasting the isentropic efficiency of this F-class heavy-duty gas turbine compressor.


2021 ◽  
Vol 1207 (1) ◽  
pp. 012014
Author(s):  
Yansong Hao ◽  
Yunfeng Jin ◽  
Chao Liu ◽  
Jiangang Hao ◽  
Haizhou Huang ◽  
...  

Abstract In order to ensure safety and reliability of energy transportation, it is necessary to understand and predict the performance of the gas turbine components. A prediction frame of the gas turbine compressor isentropic efficiency is established using the neural time series theory based on the Dynamic Neural Network. In order to obtain appropriate parameters for the network, a validation set is introduced to generalize the model. The compressor isentropic efficiency can be predicted based on the suggested model which provides an effective technical mean for the early warning of gas turbine performance. The experiment verified that the performance calculation model and the isentropic entropy efficiency prediction model based on the neural time series are effective.


2021 ◽  
Author(s):  
Christian Schänzle ◽  
Peter F. Pelz

Abstract ISO 4391:1984 gives the common efficiency definition for positive displacement machines. ISO 4409:2019 uses this efficiency definition to specify the procedure for efficiency measurements. If the machine conditions do not correspond with an incompressible flow due to operation at high pressure levels, the compressibility of the fluid and the dead volume of a pump must be taken into account. On this point, ISO 4391:1984 is physically inconsistent. Achten et. al. address this issue in their paper at FPMC 2019 presenting a critical review of ISO 4409:2007. They introduce new definitions of the overall efficiency as well as the mechanical-hydraulic efficiency. At the same time, they question the validity of the volumetric efficiency definition. Li and Barkei continue on this issue in their paper at FPMC 2020 and give a new efficiency definition based on the introduction of a new quantity Φ which describes the volume specific enthalpy of the conveyed fluid. The motivation of this paper is to contribute to the ongoing and fruitful discussion. Our approach starts with the most general efficiency definition, namely the isentropic efficiency. Subsequently, we make assumptions concerning the fluid properties with respect to the compressibility of the conveyed fluid. On the basis of the ideal cycle of a positive displacement pump and the p-v diagram, we derive physically consistent and more meaningful representations of the overall, the mechanical-hydraulic and the volumetric efficiency that address the inconsistency of ISO 4391:1984. Furthermore, we compare our findings with the existing results of Achten et. al. and Li and Barkei.


Author(s):  
Georges Salameh ◽  
Guillaume Goumy ◽  
Pascal Chesse

Abstract A turbocharger efficiency performance map given by the supplier is calculated using adiabatic flow equations and non-adiabatic experimental data. The experimental data used for this calculation is measured in hot gas stand conditions which are not adiabatic and the efficiency calculation needs correction. This paper presents a method to correct the isentropic efficiency of a compressor using the supplier maps and a heat transfer model applied on the compressor. Water is circulating in the central housing to cool the turbocharger and this water flow could be considered as insulation for heat transfer between the compressor and the turbine. The thermal effect of the turbine on the compressor is then neglected and the compressor heat flux is calculated and used to correct the isentropic efficiency calculation. The heat transfer is considered between the compressor and the surrounding environment and between the compressor and the central housing. Experimental adiabatic measurements are used to validate the model. Experimental tests are carried with different oil and water temperatures combinations to test the accuracy of the heat transfer model with these different combinations.


Author(s):  
Linfen Xing ◽  
Jianmei Feng ◽  
Zhilong He ◽  
Xueyuan Peng

The air compressor is a key component in the polymer electrolyte membrane (PEM) fuel cell system and its performance has great impact on the electric power output from the system. Here, analysis was conducted firstly on the Roots-type compressor with fixed internal compression based on the volume reduction created by helical rotors. The built-in volume ratio variations with the wrap angle and the lobe numbers were calculated and discussed. Then a prototype of the Roots-type air compressor with 6 lobes was developed according to the outcomes of the research. The volumetric and isentropic efficiency of the prototype were measured under the discharge pressures from 0.11 MPa to 0.25 MPa while the rotation speeds from 10000 to 14000 rpm. Under the design conditions, the volumetric efficiency and isentropic efficiency of the Roots-type air compressor were 75.8% and 53.9% respectively. It was concluded that this kind of Roots-type air compressor is especially suitable for the fuel cell systems applied in the range extended electric vehicles.


2021 ◽  
Vol 13 (7) ◽  
pp. 168781402110304
Author(s):  
Hai-Ou Sun ◽  
Li-Song Wang ◽  
Zhong-Yi Wang ◽  
Meng Wang ◽  
Yan-Hua Wang ◽  
...  

This paper focuses on the numerical simulation of the flow status in the compressor with the condition of fouling. NASA stage 35 was considered as the object, and the commercial code ANSYS CFX was used. The deposition rate of contaminants on the surface was considered to be different along the height of the blade. A data from related study shows that the deposition rate of the contaminant on the side close to the hub is higher than the side near the shroud part. Based on the deposition law, this paper simulated the fouling of the compressor blades by changing the thickness on the blade surface. This subject only changed the thickness of the stator blade surface because of a data showing that the fouling on the stator blade surface is almost double that on the rotor blade surface. In the condition that the roughness value of the blade surface is constant, only the stable working range of the compressor is effected by the change of the surface thickness of the stator blade. There is a positive relationship between the value of compressor minimum flow rate and the value of thickness increment. After fouling the total pressure ratio and isentropic efficiency degenerated 1.59% and 3.76%, respectively.


2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Hakan Aygün

Purpose Usage of gas turbine engines has increased by day due to rising demand for military and civil applications. This case results in investigating diverse topics related to energy efficiency and irreversibility of these systems. The purpose of this paper is to perform a detailed entropy assessment of turbojet engines for different flight conditions. Design/methodology/approach In this study, for small turbojet engines used in unmanned aerial vehicles, parametric cycle analysis is carried out at (sea level-zero Mach (hereinafter phase-I)) and (altitude of 9,000 m- Mach of 0.7 (hereinafter phase-II)). Based on this analysis, variation of performance and thermodynamic parameters with respect to change in isentropic efficiency of the compressor (CIE) and turbine (TIE) is examined at both phases. In this context, the examined ranges for CIE is between 0.78 and 0.88 whereas TIE is between 0.85 and 0.95. Findings Increasing isentropic efficiency decreases entropy production of the small turbojet engine. Moreover, the highest entropy production occurs in the combustor in the comparison of other components. Namely, it decreases from 2.81 to 2.69 kW/K at phase-I and decreases from 1.44 to 1.39 kW/K at phase-II owing to rising CIE. Practical implications It is thought that this study helps in understanding the relationship between entropy production and the efficiency of components. Namely, the approach used in the current analysis could help decision-makers or designers to determine the optimum value of design variables. Originality/value Due to rising isentropic efficiencies of both components, it is observed that specific fuel consumption (SFC) decreases whereas specific thrust (ST) increases. Also, the isentropic efficiency of a compressor affects relatively SFC and ST higher than that of the turbine.


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