scholarly journals Analysis of Pressure Pulsation Influence on Compressed Natural Gas (CNG) Compressor Performance for Ideal and Real Gas Models

2019 ◽  
Vol 9 (5) ◽  
pp. 946 ◽  
Author(s):  
Zhan Liu ◽  
Wenguang Jia ◽  
Longhui Liang ◽  
Zhenya Duan
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Ideal Gas ◽  
Specific Work ◽  
Real Gas ◽  
The Real ◽  
Compressor Performance ◽  
Ideal Gas Model ◽  
The Ideal

This work investigates the effects of pressure pulsations on reciprocating natural gas compressor performance thermodynamically. A nonlinear hybrid numerical model is thus developed to consider the interaction between the compressor and the pipeline system. The suction chamber, compressor cylinder and discharge chamber are modelled integrally based on the first law of thermodynamics and mass balance, and the pipeline flow is described by using the gas dynamic model. Methane is considered as the working fluid and its properties are computed based on ideal and real gas assumptions. For the real gas model, the methane properties are obtained by means of calling the NIST REFPROP database. The validity of numerical results is confirmed by previous experimental values. Results from the examinations of pressure pulsation influence demonstrate that discharge resonance requires more specific work than suction resonance in the same harmonic; in the suction system, the first harmonic response reduces the mass flow rate but significantly increases specific work, and the second harmonic response has a strong supercharging effect but the specific work is increased slightly; in the discharge system, the mass flow rate is changed little by pressure pulsations, but the indicated power and specific work are increased significantly; for the real gas model, the in-cylinder temperature during the compression and discharge phases, mass flow rate and indicated power are higher than those for the ideal gas model, whereas the specific work is less for the real gas model than for the ideal gas model.

CFD-Simulation of Centrifugal Fan Performance Characteristics Using Ideal and Real Gas Models for Air and Organic Fluids

2019 ◽  
Author(s):  
Manuel Fritsche ◽  
Philipp Epple ◽  
Karsten Hasselmann ◽  
Felix Reinker ◽  
Robert Wagner ◽  
...  
Keyword(s):  
Cfd Simulation ◽  
Ideal Gas ◽  
High Tech ◽  
Test Case ◽  
Centrifugal Fan ◽  
Real Gas ◽  
The Real ◽  
Organic Fluids ◽  
Ideal Gas Model ◽  
The Ideal

Abstract Efficient processes with organic fluids are becoming increasingly important. The high tech fluid Novec™ is such an organic fluid and is used, for example, as a coolant for highperformance electronics, low-temperature heat transfer applications, cooling of automotive batteries, just to mention a few. Thus, efficient designed fans for the transport of organic fluids are becoming more and more important in the process engineering. CFD-simulations are nowadays integral part of the design and optimization process of fans. For air at the most usual application conditions, i.e. no extreme temperatures or pressures, the ideal gas model is in good agreement with the real gas approach. In the present study, this real gas approach for organic fluids have been investigated with CFD methods and, the deviation from the ideal gas model has been analyzed. For this purpose, a simulation model of a centrifugal fan with volute has been designed as a test case. First, the ideal gas model approach has been compared with the real gas approach model of Peng-Robinson for air using the commercial solver ANSYS CFX. Thereafter, the same comparison has been performed using the organic fluid Novec™. After a detailed grid study, the entire fan characteristics, i.e. the design point and the off-design points, have been simulated and evaluated for each fluid (air and Novec™) and gas model (ideal gas and Peng-Robinson real gas). The steady state simulations of the centrifugal fan have been performed using the Frozen Rotor model. The simulation results have been compared, discussed and presented in detail.

The Effect of Gas Models on Compressor Efficiency Including Uncertainty

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Fangyuan Lou ◽  
John Fabian ◽  
Nicole L. Key
Keyword(s):  
Pressure Ratio ◽  
Ideal Gas ◽  
Experimental Measurements ◽  
Perfect Gas ◽  
Real Gas ◽  
The Real ◽  
Compressor Efficiency ◽  
Ideal Gas Model ◽  
Isentropic Efficiency ◽  
The Ideal

Since isentropic efficiency is widely used in evaluating the performance of compressors, it is essential to accurately calculate this parameter from experimental measurements. Quantifying realistic bounds of uncertainty in experimental measurements are necessary to make meaningful comparisons to computational fluid dynamics simulations. This paper explores how the gas model utilized for air can impact not only the efficiency calculated in an experiment, but also the uncertainty associated with that calculation. In this paper, three different gas models are utilized: the perfect gas model, the ideal gas model, and the real gas model. A commonly employed assumption in calculating compressor efficiency is the perfect gas assumption, in which the specific heat, is treated as a constant and is independent of temperature and pressure. Results show significant differences in both calculated efficiency and the resulting uncertainty in efficiency between the perfect gas model and the real gas model. The calculated compressor efficiency from the perfect gas model is overestimated, while the resulting uncertainties from the perfect gas model are underestimated. The ideal gas model agrees well with the real gas model, however. Including the effect of uncertainty in gas properties results in very large uncertainties in isentropic efficiency, on the order of ten points, for low pressure ratio machines.

scholarly journals High-intensity air-explosion-induced shock loading of structures: consideration of a real gas in modelling a nonlinear compressible medium

2015 ◽  
Vol 471 (2176) ◽  
pp. 20140825 ◽  
Author(s):  
R. Ghoshal ◽  
N. Mitra
Keyword(s):  
High Intensity ◽  
Intermolecular Forces ◽  
Ideal Gas ◽  
Compressible Medium ◽  
Light Weight ◽  
Air Blast ◽  
Real Gas ◽  
The Real ◽  
Ideal Gas Model ◽  
The Ideal

The existing practice of designing air-blast-resistant structures relies on the ideal gas model. But this model predicts the maximum value of the reflection coefficient (ratio of the reflected to the incident pressure) to be 8, whereas it can go up to 20 or more as reported in the literature. To address this discrepancy, air medium is modelled as a real gas instead of an ideal gas, where the effect of intermolecular forces, vibration, dissociation, electronic excitation and ionization are included. Ranges of peak over-pressure are identified where the ideal gas assumption cannot be used. Differences in impulse transmitted to the free-standing plates of different mass owing to relaxing of the ideal gas assumption and consideration of the real gas model are evaluated. Impulse transmitted to the structures for constant and variable back pressure (VBP) is also compared considering the real gas model. The result shows that for high-intensity shock, the ideal gas model under-predicts impulse transmitted to heavy plates but over-predicts the same for light-weight plates. Impulse transmitted to light-weight plates is also overestimated if VBP is neglected. The implications of this research are substantial for designing high-intensity air-blast mitigating structures, which if not considered properly, may lead to compromise in structural performance.

The Parameter Variation in Pressure Vessel during Loading Operation by Considering Heat Transfer Impact Based on Real Gas Model

2012 ◽  
Vol 516-517 ◽  
pp. 467-470
Author(s):  
Wei Qing Wang ◽  
Li Yang ◽  
Shi Gui Lv
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Pressure Vessel ◽  
Simulation Method ◽  
Ideal Gas ◽  
Molecular Volume ◽  
Real Gas ◽  
The Real ◽  
Ideal Gas Model ◽  
The Ideal

Since the molecular force and the molecular volume were ignored in the ideal gas model, and it was less accurate when the ideal gas model was used to depict characteristics of real gas under high pressure, so the real gas model was adopted and the heat transfer was considered, the dynamic variation model was set up for internal gas in the pressure vessel during loading operation. The model was solved by using the numerical simulation method of Runge-Kutta. Comparison was made between the ideal gas model and the real gas model under adiabatic and non-adiabatic conditions, it showed that under low pressure the results obtained by the two models were in good agreement, but under high pressure the deviation was enlarged, the real gas model with considering the heat transfer influenced would be more coincident with the reality.

The Effect of Gas Models on Compressor Efficiency Including Uncertainty

2013 ◽  
Author(s):  
Fangyuan Lou ◽  
John Fabian ◽  
Nicole L. Key
Keyword(s):  
Pressure Ratio ◽  
Ideal Gas ◽  
Experimental Measurements ◽  
Perfect Gas ◽  
Real Gas ◽  
The Real ◽  
Compressor Efficiency ◽  
Ideal Gas Model ◽  
Isentropic Efficiency ◽  
The Ideal

Since isentropic efficiency is widely used in evaluating the performance of compressors, it is essential to accurately calculate this parameter from experimental measurements. Quantifying realistic bounds of uncertainty in experimental measurements are necessary to make meaningful comparisons to CFD simulations. This paper explores how the gas model utilized for air can impact not only the efficiency calculated in an experiment but also the uncertainty associated with that calculation. In this paper, three different gas models are utilized: the perfect gas model, the ideal gas model, and the real gas model. A commonly employed assumption in calculating compressor efficiency is the perfect gas assumption, in which the specific heat, is treated as a constant and is independent of temperature and pressure. Results show significant differences in both calculated efficiency and the resulting uncertainty in efficiency between the perfect gas model and the real gas model. The calculated compressor efficiency from the perfect gas model is overestimated, while the resulting uncertainties from the perfect gas model are underestimated. The ideal gas model agrees well with the real gas model, however. Including the effect of uncertainty in gas properties results in very large uncertainties in isentropic efficiency, on the order of 10 points, for low pressure ratio machines.

CFD Simulation of the Supersonic Steam Ejector

2010 ◽  
Author(s):  
Zhiming Li ◽  
Jinli Wang ◽  
Hongtao Zheng ◽  
Cailin ◽  
Yajun Li
Keyword(s):  
Mass Flow Rate ◽  
Flow Rate ◽  
Critical Pressure ◽  
Ideal Gas ◽  
Back Pressure ◽  
State Equations ◽  
Entrainment Ratio ◽  
Real Gas ◽  
Steam Ejector ◽  
Ideal Gas Model

The supersonic steam ejector is widely used in many industries which are steam powered such as oil, thermoelectric, refrigeration and so on. Many scholars analyzed the steam ejector by using ideal gas model and they ignored phase change, this may bring some errors for the flowing field of the ejector. In this study, the supersonic steam ejector was simulated using CFD (Computational Fluid Dynamics). Flowing field of the ejector was analyzed by using different state equations. The results shows that performance of the ejector was underestimated under the ideal gas model, and the entrainment ratio is 20%–40% lower than using real gas model. When phase changing was considered under real gas state equations, influences of working fluid pressure and back pressure were investigated. The results illustrates that working critical pressure and back flow critical pressure exist in the flow, and the entrainment ratio reaches its peak at working critical pressure. The performance of the ejector was almost the same when the outlet pressure was lower than critical back pressure. Effects of ejector geometries were also investigated in this paper. It shows that there are optimums of the relative position of the steam nozzle and the taper of the mixing section, length of mixing chamber and diameter of throat according to mass flow rate of second fluid. There are also critical length of diffuser and throat. Mass flow rate stayed the same when the length of diffuser or throat grows. This paper will provide a theoretical basis for ejector’s energy-saving and geometry optimization.

scholarly journals ANALYSIS OF EVAPORATOR EFFECTIVENESS ON 1/2 CYCLE REFRIGERATION SYSTEMS: A CASE STUDY ON LPG FUELED VEHICLES

2020 ◽  
Vol 82 (3) ◽  
Author(s):  
Muji Setiyo ◽  
Budi Waluyo ◽  
Nurkholis Hamidi
Keyword(s):  
Heat Transfer ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Exchange Process ◽  
Cooling Curve ◽  
Heat Exchange Process ◽  
Heat Transfer Capacity ◽  
The Ideal

The ½ cycle refrigeration system on LPG fueled vehicles has a significant cooling effect. However, the cooling is very dependent on the heat exchange process in the evaporator. Therefore, this paper analyses the deviation of the actual cooling curve from the ideal scenario carried out on a laboratory scale. The analytical method used is the calculation of the effectiveness of the evaporator, which compares the actual to the potential heat transfer capacity. The LPG flow rate was varied from 1-6 g/s, while the evaporation pressure ranged between 0.05, 0.10, and 0.15 MPa, which applied to compact type evaporators with dimensions of 262 ´ 200 mm, with a thickness of 65 mm. The research results confirm that the higher the LPG mass flow rate, the lower the heat transfer effectiveness. At the higher LPG mass flow rate, heat transfer occurs less optimally,  due to incomplete evaporation of LPG in the evaporator.

Centrifugal Compressor Performance Prediction Using Gaussian Process Regression and Artificial Neural Networks

2019 ◽  
Author(s):  
Pau Cutrina Vilalta ◽  
Hui Wan ◽  
Soumya S. Patnaik
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Centrifugal Compressor ◽  
Rotational Speed ◽  
Data Augmentation ◽  
Pressure Ratio ◽  
Gaussian Process Regression ◽  
Compressor Performance ◽  
Artificial Neural

Abstract In this paper, we use various regression models and Artificial Neural Network (ANN) to predict the centrifugal compressor performance map. Particularly, we study the accuracy and efficiency of Gaussian Process Regression (GPR) and Artificial Neural Networks in modelling the pressure ratio, given the mass flow rate and rotational speed of a centrifugal compressor. Preliminary results show that both GPR and ANN can predict the compressor performance map well, for both interpolation and extrapolation. We also study the data augmentation and data minimzation effects using the GPR. Due to the inherent pressure ratio data distribution in mass-flow-rate and rotational-speed space, data augmentation in the rotational speed is more effective to improve the ANN performance than the mass flow rate data augmentation.

Evaluation of Axial Compressor Characteristics Under Overspray Condition

2013 ◽  
Author(s):  
Chihiro Myoren ◽  
Yasuo Takahashi ◽  
Manabu Yagi ◽  
Takanori Shibata ◽  
Tadaharu Kishibe
Keyword(s):  
Gas Turbine ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Water Mass ◽  
Pressure Ratio ◽  
Axial Compressor ◽  
Test Facility ◽  
Compressor Performance ◽  
Water Mass Flow Rate

An axial compressor was developed for an industrial gas turbine equipped with a water atomization cooling (WAC) system, which is a kind of inlet fogging technique with overspray. The compressor performance was evaluated using a 40MW-class test facility for the advanced humid air turbine system. A prediction method to estimate the effect of WAC was developed for the design of the compressor. The method was based on a streamline curvature (SLC) method implementing a droplet evaporation model. Four test runs with WAC have been conducted since February 2012. The maximum water mass flow rate was 1.2% of the inlet mass flow rate at the 4th test run, while the design value was 2.0%. The results showed that the WAC decreased the inlet and outlet temperatures compared with the DRY (no fogging) case. These decreases changed the matching point of the gas turbine, and increased the mass flow rate and the pressure ratio by 1.8% and 1.1%, respectively. Since prediction results agreed with the results of the test run qualitatively, the compressor performance improvement by WAC was confirmed both experimentally and analytically. The test run with the design water mass flow rate is going to be conducted in the near future.

Dynamic Response Formulation for Pneumatically Driven Liquid in a Pressure Vessel

1991 ◽  
Author(s):  
Richard B. Loucks
Keyword(s):  
Mass Flow Rate ◽  
Aluminum Powder ◽  
Mass Flow ◽  
Flow Rate ◽  
Pressure Vessel ◽  
Ideal Gas ◽  
Liquid Oxygen ◽  
Mean Flow ◽  
Containment Vessel ◽  
Thermal Output

Abstract The Thermal Radiation Simulator (TRS) at the U.S. Army Ballistic Research Laboratory uses aluminum powder reacting with liquid oxygen to create a large jet like flame. The flame acts as a large thermally radiant wall, exposing targets to a nuclear weapon equivalent. The aluminum powder is driven pneumatically to the combustion chamber from a pressurized containment vessel. Unfortunately the thermal output of the flame oscillates with large amplitude relative to the mean yield. The fluctuating mass flow rate of aluminum powder from the aluminum powder containment vessel seemed the cause of the unstable output. A computer model of the aluminum vessel was constructed to determine the pressure dynamics in the pressure vessel. The aluminum powder was assumed to behave as a Newtonian liquid. The pneumatic fluid was assumed to be an ideal gas. The model concentrated inside the vessel and at the exit. The result was to determine the mass flow rate of aluminum from the exit given the inlet gas pressures. The model did reveal the source of mass flow fluctuations not to be caused directly by the existing pneumatic set-up. The variation was shown to be perturbated by forces outside the pressure vessel. Once the outside influence was eliminated, the model showed a clean mean flow rate of aluminum powder. The results were applied to the TRS and the thermal output was stabilized.

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