Investigation of interaction between thermodynamic processes and pressure pulsation based on transient CFD model of a reciprocating compressor

2021 ◽  
pp. 095440892110047
Author(s):  
Bin Zhao ◽  
Shuangmei Zhou ◽  
Xiaohan Jia ◽  
Mingfeng Wang ◽  
Zenghui Ma
Keyword(s):  
Rotational Speed ◽  
Pressure Pulsation ◽  
Time Pressure ◽  
Pressure Ratio ◽  
Flow Channel ◽  
Maximum Deviation ◽  
Reciprocating Compressor ◽  
Cfd Model ◽  
Fast Fourier Transform Analysis ◽  
All Speeds

This paper presents a transient computational fluid dynamics (CFD) model of a reciprocating compressor to study the interaction of the thermodynamic process and pressure pulsation. To realize the interaction between the thermodynamics and the pressure pulsation, the most difficult procedure lies in dealing with the valve motion and flow through the valve channel both precisely and effectively. Therefore, a discretization method for the flow channel of the ring valve to generate structured grids is proposed. Then, the subsequent model is embedded in the flow channel of the compressor model. User-defined functions are employed to calculate the independent velocity of each valve plate based on the real-time pressure differences across the valve plates. After verified, the influences of the discharge pipeline configuration, pressure ratio, and rotational speed were examined. The results of the numerical model agreed well with the experiment. The maximal deviation between predictions and experiments at the pressure ratio of 3 was 6.14% of indicated power. The maximum deviation increased to 7.42% at the rotational speed of 480 rpm. The results for the discharge pipeline configuration verified that the buffer tank directly following the nozzle of the compressor contributed greatly to attenuating the pressure pulsation. A fast Fourier transform analysis of pressure pulsation showed that at all speeds, the amplitudes were almost the same below the eighth harmonic, and then gradually increased for the higher harmonics.

Effect of a cross-flow perforated tube on pressure pulsation and pressure loss in a reciprocating compressor piping system

2016 ◽  
Vol 231 (3) ◽  
pp. 473-484 ◽  
Author(s):  
Zhan Liu ◽  
Junming Cheng ◽  
Quanke Feng ◽  
Xiaoling Yu
Keyword(s):  
Pressure Loss ◽  
Pressure Pulsation ◽  
Cross Flow ◽  
Wave Theory ◽  
Hole Diameter ◽  
Tube Length ◽  
Maximum Deviation ◽  
Piping System ◽  
Reciprocating Compressor ◽  
Perforated Tube

This paper experimentally investigates the effects of a cross-flow perforated tube on the pressure pulsation attenuation and pressure loss in a reciprocating compressor piping network, with particular focus on the structure parameters and installation positions. The results demonstrate that significant pressure fluctuation attenuation and less pressure loss in the whole piping system can be achieved when a well-designed cross-flow perforated tube is installed downstream of the pulsating bottle. The pressure pulsation is reduced as the perforated rate decreases and as the perforated tube length increases, while the hole diameter has little effect upon the pulsation attenuation. In the aspect of reducing pressure loss, the perforated rate should be larger than 0.05 and the hole diameter should be larger than 8 mm. In addition, a pressure pulsation computation model based on the linear acoustic wave theory and transfer matrix method is developed to predict the pulsating pressure in compressor piping systems with an installed cross-flow perforated tube. With favorable agreement between the model prediction and the present experimental results (maximum deviation within 6.8%), the predicted pulsating pressure can be attenuated for the reciprocating compressor piping system with various compressor speeds when a cross-flow perforated tube is reasonably designed and installed.

Altitude Effects on the Performance of Small Radial Turbomachinery: Part I — Compressor Impellers

2016 ◽  
Author(s):  
Dries Verstraete ◽  
Kjersti Lunnan
Keyword(s):  
Reynolds Number ◽  
Performance Analysis ◽  
Rotational Speed ◽  
Pressure Ratio ◽  
Unmanned Aircraft ◽  
Good Match ◽  
One Dimensional ◽  
Design Changes ◽  
Current Article ◽  
The Impact

Small unmanned aircraft are currently limited to flight ceilings below 20,000 ft due to the lack of an appropriate propulsion system. One of the most critical technological hurdles for an increased flight ceiling of small platforms is the impact of reduced Reynolds number conditions at altitude on the performance of small radial turbomachinery. The current article investigates the influence of Reynolds number on the efficiency and pressure ratio of two small centrifugal compressor impellers using a one-dimensional meanline performance analysis code. The results show that the efficiency and pressure ratio of the 60 mm baseline compressor at the design rotational speed drops with 6–9% from sea-level to 70,000 ft. The impact on the smaller 20 mm compressor is slightly more pronounced and amounts to 6–10%. Off-design changes at low rotational speeds are significantly higher and can amount to up to 15%. Whereas existing correlations show a good match for the efficiency drop at the design rotational speed, they fail to predict efficiency changes with rotational speed. A modified version is therefore proposed.

Surge Prevention Techniques for a Turbocharged Solid Oxide Fuel Cell Hybrid System

2021 ◽  
Author(s):  
L. Mantelli ◽  
M. L. Ferrari ◽  
A. Traverso
Keyword(s):  
Fuel Cell ◽  
Solid Oxide Fuel Cell ◽  
Rotational Speed ◽  
Pressure Ratio ◽  
High Energy ◽  
Cell System ◽  
Solid Oxide ◽  
Pollutant Emissions ◽  
Inlet Temperature ◽  
Oxide Fuel

Abstract Pressurized solid oxide fuel cell (SOFC) systems are one of the most promising technologies to achieve high energy conversion efficiencies and reduce pollutant emissions. The most common solution for pressurization is the integration with a micro gas turbine, a device capable of exploiting the residual energy of the exhaust gas to compress the fuel cell air intake and, at the same time, generating additional electrical power. The focus of this study is on an alternative layout, based on an automotive turbocharger, which has been more recently considered by the research community to improve cost effectiveness at small size (< 100 kW), despite reducing slightly the top achievable performance. Such turbocharged SOFC system poses two main challenges. On one side, the absence of an electrical generator does not allow the direct control of the rotational speed, which is determined by the power balance between turbine and compressor. On the other side, the presence of a large volume between compressor and turbine, due to the fuel cell stack, alters the dynamic behavior of the turbocharger during transients, increasing the risk of compressor surge. The pressure oscillations associated with such event are particularly detrimental for the system, because they could easily damage the materials of the fuel cells. The aim of this paper is to investigate different techniques to drive the operative point of the compressor far from the surge condition when needed, reducing the risks related to transients and increasing its reliability. By means of a system dynamic model, developed using the TRANSEO simulation tool by TPG, the effect of different anti-surge solutions is simulated: (i) intake air conditioning, (ii) water spray at compressor inlet, (iii) air bleed and recirculation, and (iv) installation of an ejector at the compressor intake. The pressurized fuel cell system is simulated with two different control strategies, i.e. constant fuel mass flow and constant turbine inlet temperature. Different solutions are evaluated based on surge margin behavior, both in the short and long terms, but also monitoring other relevant physical quantities of the system, such as compressor pressure ratio and turbocharger rotational speed.

Aeroelastic Properties of Closely Spaced Modes for a Highly Loaded Transonic Fan

2008 ◽  
Author(s):  
Hans Ma˚rtensson ◽  
Ste´fan Sturla Gunnsteinsson ◽  
Damian M. Vogt
Keyword(s):  
Rotational Speed ◽  
Pressure Ratio ◽  
Stability Margin ◽  
Frequency Separation ◽  
Mode Shapes ◽  
Compressor Blades ◽  
Aeroelastic System ◽  
High Pressure Ratio ◽  
Mode Separation ◽  
Centrifugal Stiffening

In the design of modern compressor blades of wide chord (low aspect ratio) type it is often hard to avoid having modes that are close to each other in frequency. Modes which are closely spaced can interact dynamically. Mistuning and localization of stresses are known problems with this. A potential problem with this is also the possibility of coalescence flutter of the modes. Even if the modes are frequency separated at zero rotational speed, the centrifugal stiffening may cause the modes to attract and even cross (or veer) at some rotational speed. In design, mode separation criteria are sometimes applied in order to minimize the risk of encountering unknown dynamic phenomena. This study is performed to better understand the dynamics of closely spaced modes with respect to risk for coalescence flutter. A reduced order aeroelastic system is then constructed that describes the interaction between the different modes. The aeroelastic couplings are then calculated for the 2 mode system. The method is general in terms of mode shapes and number of interacting modes. A parametrical study is performed in order to study how strongly the modes interact when the frequency separation is decreased and if there is a risk of destructive coalescence flutter. The investigation is performed on a high pressure ratio front stage fan blade. The tendency of the modes to interact depends on the strength of the coupling compared to the strength of the pure structural modes. The tendency towards instability was increased in cases where the stability margin was smaller of the single modes. The results can be considered to support a separation criterion of 2% for the lower. A re-evaluation should be considered if lighter blade material and increased loads are to be used.

The Port Width and Position Determination for Pressure-Exchange Ejector

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
Wenjing Zhao ◽  
Dapeng Hu ◽  
Peiqi Liu ◽  
Yuqiang Dai ◽  
Jiupeng Zou ◽  
...  
Keyword(s):  
High Pressure ◽  
Performance Optimization ◽  
Pressure Ratio ◽  
Low Pressure ◽  
Operating Conditions ◽  
Maximum Deviation ◽  
Dimensionless Time ◽  
Pressure Flow ◽  
Outlet Pressure ◽  
Pressure Exchange

A pressure-exchange ejector transferring energy by compression and expansion waves has the potential for higher efficiency. The width and position of each port are essential in pressure-exchange ejector design. A dimensionless time τ expressing both port widths and the positions of port ends was introduced. A prototype was designed and the experimental system was set up. Many sets of experiment with different geometrical arrangements were conducted. The results suggest that the efficiency greatly changes with the geometrical arrangements. The efficiency is about 60% at proper port widths and positions, while at improper geometrical arrangements, the efficiency is much lower and the maximum deviation may reach about 20%. The proper dimensionless port widths and positions at different operating conditions are obtained. For a fixed overall pressure ratio, the widths of the high pressure flow inlet and middle pressure flow outlet increase as the outlet pressure increases and the low pressure flow inlet width is reduced with a larger outlet pressure. The middle pressure flow outlet (MO) opening end remains constant at different outlet pressures. The positions of the high pressure flow inlet (HI) closed end and the low pressure flow inlet (LI) open end increase with the elevation of outlet pressure, however, the distance between the HI closing end and the LI opening end is constant. The port widths and positions have a significant influence on the performance of the pressure-exchange ejector. The dimensionless data obtained are very valuable for pressure-exchange ejector design and performance optimization.

Cavitation in a high-speed aviation axial piston pump over a wide range of fluid temperatures

2021 ◽  
pp. 095765092110469
Author(s):  
Qun Chao ◽  
Zi Xu ◽  
Jianfeng Tao ◽  
Chengliang Liu ◽  
Jiang Zhai
Keyword(s):  
Temperature Effects ◽  
Pressure Pulsation ◽  
Piston Pump ◽  
Limiting Factors ◽  
Fluid Temperature ◽  
Cfd Model ◽  
Axial Piston Pump ◽  
Wide Range ◽  
Fluid Properties ◽  
Axial Piston

The axial piston pump in aerospace applications needs to operate over a wide range of fluid temperatures from −54°C to 135 °C. The fluid properties at such extreme temperatures will significantly affect the cavitation that is one of the major limiting factors for the efficiency and reliability of aviation axial piston pumps. However, it appears that very little of the existing literature studies the effects of extreme fluid temperatures on the pump cavitation. This paper aims to examine the temperature effects on the cavitation in an aviation axial piston pump. First, we develop a three-dimensional (3D) transient computational fluid dynamics (CFD) model to investigate the pump cavitation and validate it experimentally. Second, we use the validated CFD model to investigate the temperature effects on the pump cavitation by changing the fluid properties including viscosity, density, and bulk modulus. The numerical results show that low fluid temperature makes the aviation axial piston pump suffer serious cavitation due to high viscosity, leading to delivery flow breakdown, unacceptable pressure pulsation, and delayed pressure built up. In contrast, high fluid temperatures have minor effects on the cavitation although they increase the pressure pulsation and built-up time slightly.

Novel Approach for Optical Characterization of Thrust Collar Lubricated Area: Experimental and Numerical Results

2021 ◽  
Vol 143 (1) ◽  
Author(s):  
Thomas Kerr ◽  
Adolfo Delgado
Keyword(s):  
High Speed ◽  
Pressure Field ◽  
Load Capacity ◽  
Fe Model ◽  
Cfd Model ◽  
Axial Loads ◽  
Test Rig ◽  
Efficient Operation ◽  
Oil Film ◽  
All Speeds

Abstract Thrust collars (TCs) are bearing elements used in geared machinery that transmit axial loads from one shaft to another. TCs are primarily used in integrally geared compressors (IGCs) but are also found in gearboxes and marine propulsion applications. TCs are hydrodynamic elements featuring a converging-diverging wedge to generate a pressure field that reacts axial loads. Accurate modeling requires knowledge of the film characteristics such as cavitation, turbulence, and air ingestion, all of which reduce load capacity. Current models in the literature do not include mass-conserving cavitation algorithms or turbulence flow. The following paper introduces a new test rig that optically characterizes the thin film region of a TC. The test rig geometries, speeds, and loads match those typically seen in IGC applications. The test rig utilizes a transparent acrylic window in conjunction with a high-speed camera (HSC) to obtain high-speed images of the oil film. Images are filtered and averaged to obtain areas of interest in the oil film. Cavitation and turbulence areas are measured for pinion speeds of 2.5, 5, and 7.5 krpm and axial loads of 0.5, 1, and 1.5 kN. Cavitation occurs in the diverging (upper) region of the TC and appears at pinion speeds over 5000 rpm but does not change in shape after that speed. The cavitation is independent of applied load. Turbulence at the inlet region (bottom) occurs at all speeds but increases to almost 35% of the total area at the highest speed. This paper also presents a finite element (FE) model that includes predictions for the static characteristics of the TC, specifically the cavitation area. The cavitation modeling uses an iterative Elord's method, which conserves mass. The model predicts a similar cavitation area for all speeds and loads. A computational fluid dynamics (CFD) study predicts a similar cavitation area and pressure field to the FE model. The CFD model predicts turbulence in the lower region that increases for increasing spin speed, which matches the experimental results. The CFD model tends to under-predict the turbulence area compared to the experiments. As IGCs move into new application areas to satisfy new needs, the increase in efficiency and capacity comes at a cost of more load and higher speed requirements on the TCs. This work will help original equipment manufacturers model TCs more accurately to ensure safe and efficient operation.

Numerical Investigations on the Power Generation of Turbo-Expander During the Propane De-Hydrogenation Process

2019 ◽  
Author(s):  
Hwabhin Kwon ◽  
Heesung Park
Keyword(s):  
Power Generation ◽  
Rotational Speed ◽  
Mechanical Energy ◽  
Pressure Ratio ◽  
Electrical Power ◽  
Operating Conditions ◽  
Hydrogenation Process ◽  
Operation Conditions ◽  
Turbo Expander ◽  
Discharge Pressure

Abstract A turboexpander for the propane de-hydrogenation process with blade and splitter has been numerically investigated. Since the turboexpander expands fluid from higher inlet pressure to lower discharge pressure, the kinetic energy of fluid is converted into useful mechanical energy. The efficiency and power generation with the designed turboexpander have been simulated with different operating conditions. The pressure ratio between inlet and outlet and rotational speed are varied to characterize the performance of the turboexpander as an electrical power generator. The numerical simulations have shown the vortex at the trailing edges of blade and splitter which decreases the efficiency. The rotational speed and the pressure ratio are parameterized to obtain operation conditions which achieve high power generation and efficiency. Consequently, the generated power from 614.12 kW to 693.45kW is obtained at the normal rotational speed and the pressure ratio between 1.75 to 2.22.

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.

Experimental Investigation of Oil Flowrate in a Hermetic Reciprocating Compressor

2014 ◽  
Author(s):  
Sibel Tas ◽  
Sertac Cadirci ◽  
Hasan Gunes ◽  
Kemal Sarioglu ◽  
Husnu Kerpicci
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Rotational Speed ◽  
High Speed ◽  
Operating Conditions ◽  
Lubricating Oil ◽  
Reciprocating Compressor ◽  
Oil Flow ◽  
Oil Flow Visualization

The aim of this experimental study is to investigate the mass flow rate of the lubricating oil in a hermetic reciprocating compressor. Essential parameters affecting the performance of the lubrication are the rotational speed of the crankshaft, the viscosity of the oil, the operating temperature and the submersion depth of the crankshaft. An experimental setup was built as to measure the oil mass flow rate with respect to the oil temperature variation during different operating conditions. The influence of the governing parameters such as the rotational speed, temperature (viscosity) and the submersion depth on the mass flow rate from crankshaft outlet are studied in detail. In addition, the oil flow visualization from the upper hole of the crankshaft is performed using a high-speed camera in order to observe the effectiveness of the lubrication of the various parts of the compressor. This study reveals that with increasing rotational speed, the submersion depth of the crankshaft and with decreasing viscosity of the lubricant, the mass flow rate from the crankshaft increases.

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