Influence of Tip Jet Mass Flow and Blowing Rate on the Performance of an Axial Diffuser at Different Inlet Total Pressure Profiles

2015 ◽  
Author(s):  
Rojas Thomas ◽  
Markus Schatz ◽  
Benjamin Kuschel ◽  
Silke Brouwer ◽  
A. M. Pradeep ◽  
...  
Keyword(s):  
Mass Flow ◽  
Total Pressure ◽  
Pressure Recovery ◽  
Jet Flows ◽  
Cfd Simulations ◽  
Blowing Ratio ◽  
Pressure Profiles ◽  
Mass Flow Rates ◽  
Computational Fluid Dynamics Cfd ◽  
The Impact

The present paper evaluates the impact of casing energized jet flow on the performance of an annular-conical exhaust diffuser. Two different inflow profiles, namely a uniform total pressure and a hub-strong total pressure inlet profile were studied. For both profiles, the flow is observed to separate at the casing. Experiments were performed at different tip jet mass flow rates and two different tip gap heights to understand their effect on the diffuser performance. Apart from wall pressure readings, probe measurements have been done at various locations within the diffuser to study the flow behaviour in more detail. The results show that at the diffuser inlet already small tip jet flows help to prevent casing separation and hence improve pressure recovery noticeably, especially in the front section of the diffuser. On the other hand, higher tip jet flows tend to weaken the core flow at the diffuser exit, thus generating an inhomogeneous outflow velocity profile. To enhance the interpretation of the experimental data, results from Computational Fluid Dynamics (CFD) simulations are used. Interestingly, the experimental results indicate that while the blowing ratio seems to be the major parameter for the improvement of pressure recovery for a hub-strong inlet profile, the pressure recovery for a uniform profile appears to be more sensitive to the tip jet mass flow rate. However, the numerical results do not show this trend.

The Influence of the Total Pressure Profile on the Performance of Axial Gas Turbine Diffusers

2011 ◽  
Vol 134 (2) ◽  
Author(s):  
A. Hirschmann ◽  
S. Volkmer ◽  
M. Schatz ◽  
C. Finzel ◽  
M. Casey ◽  
...  
Keyword(s):  
Flow Separation ◽  
Gas Turbines ◽  
Total Pressure ◽  
Pressure Profile ◽  
Cfd Simulations ◽  
Pressure Profiles ◽  
Industrial Gas Turbines ◽  
Sst Turbulence Model ◽  
Computational Fluid Dynamics Cfd ◽  
Highly Loaded

Large industrial gas turbines for combined heat and power generation normally have axial diffusers leading to the heat recovery steam generator. The diffusers operate with high inlet axial Mach number (0.6) and with a nonuniform inlet total pressure profile from the turbine. Tests have been carried out on a generic highly loaded axial diffuser in a scaled axial diffuser test rig, with different inlet total pressure profiles including those that might be met in practice. The results show that the inlet total pressure profile has a strong effect on the position of flow separation, whereby a hub-strong profile tends to separate at the casing and the tip-strong profile on the hub. Steady computational fluid dynamics (CFD) simulations using the shear stress transport (SST) turbulence model have been carried out based on extensive studies of the best way to model the inlet boundary conditions. These simulations provide good agreement with the prediction of separation in the diffuser but the separated regions often persist too long so that, in this highly loaded case with flow separation, the calculated diffuser pressure recovery can be in error by up to 30%.

Numerical Investigation of Local Cooling Enhancement Using Pin-Finned Channel With Incremental Impingement

2017 ◽  
Author(s):  
Susheel Singh ◽  
Sumanta Acharya ◽  
Forrest Ames
Keyword(s):  
Aspect Ratio ◽  
Mass Flow ◽  
Cross Flow ◽  
Surface Cooling ◽  
Local Cooling ◽  
Stagnation Region ◽  
Flow Rates ◽  
Pin Fins ◽  
Mass Flow Rates ◽  
The Impact

Flow and heat transfer in a low aspect ratio pin-finned channel, representative of an internally cooled turbine airfoil, is investigated using Large Eddy Simulations (LES). To achieve greater control of surface cooling distribution, a novel approach has been recently proposed in which coolant is injected incrementally through a series of holes located immediately behind a specially designed cutout region downstream of the pin-fins. Sheltering the coolant injection behind the pin-fins avoids the impact of the cross-flow buildup that deflects the impingement jet and isolates the surface from cooling. The longitudinal and transverse spacing of the pin-fins, arranged in a staggered fashion, is X/D = 1.046 and S/D = 1.625, respectively. The aspect ratio (H/D) of pin-fin channel is 0.5. Due to the presence of the sequential jets in the configuration, the local cooling rates can be controlled by controlling the jet-hole diameter which impacts the jet mass flow rate. Hence, four different hole diameters, denoted as Large (L), Medium (M) , Small (S), Petite (P) are tested for impingement holes, and their effects are studied. Several patterns of the hole-size distributions are studied. It is shown that the peak Nusselt number in the stagnation region below the jet correlates directly with the jet-velocity, while downstream the Nusselt numbers correlate with the total mass flow rates or the average channel velocity. The local cooling parameter defined as (Nu/Nu0)(1-ε) correlates with the jet/channel mass flow rates.

scholarly journals Numerical and experimental analyses for the improvement of surface instant decontamination technology through biocidal agent dispersion: Potential of application during pandemic

PLoS ONE ◽  
2021 ◽  
Vol 16 (5) ◽  
pp. e0251817
Author(s):  
Paulo Roberto Freitas Neves ◽  
Turan Dias Oliveira ◽  
Tarcísio Faustino Magalhães ◽  
Paulo Roberto Santana dos Reis ◽  
Luzia Aparecida Tofaneli ◽  
...  
Keyword(s):  
Experimental Tests ◽  
Cfd Simulations ◽  
New Device ◽  
Qualitative And Quantitative ◽  
Droplet Concentration ◽  
Computational Fluid Dynamics Cfd ◽  
Suspended Droplet ◽  
The Impact ◽  
Disinfection Chamber ◽  
Important Form

The transmission of SARS-CoV-2 through contact with contaminated surfaces or objects is an important form of transmissibility. Thus, in this study, we evaluated the performance of a disinfection chamber designed for instantaneous dispersion of the biocidal agent solution, in order to characterize a new device that can be used to protect individuals by reducing the transmissibility of the disease through contaminated surfaces. We proposed the necessary adjustments in the configuration to improve the dispersion on surfaces and the effectiveness of the developed equipment. Computational Fluid Dynamics (CFD) simulations of the present technology with a chamber having six nebulizer nozzles were performed and validated through qualitative and quantitative comparisons, and experimental tests were conducted using the method Water-Sensitive Paper (WSP), with an exposure to the biocidal agent for 10 and 30 s. After evaluation, a new passage procedure for the chamber with six nozzles and a new configuration of the disinfection chamber were proposed. In the chamber with six nozzles, a deficiency was identified in its central region, where the suspended droplet concentration was close to zero. However, with the new passage procedure, there was a significant increase in wettability of the surface. With the proposition of the chamber with 12 nozzles, the suspended droplet concentration in different regions increased, with an average increase of 266%. The experimental results of the new configuration proved that there was an increase in wettability at all times of exposure, and it was more significant for an exposure of 30 s. Additionally, even in different passage procedures, there were no significant differences in the results for an exposure of 10 s, thereby showing the effectiveness of the new configuration or improved spraying and wettability by the biocidal agent, as well as in minimizing the impact caused by human factor in the performance of the disinfection technology.

Aerodynamic Performance Evaluation of Axial Flow Fan Using Numerical Techniques

2021 ◽  
Author(s):  
Raghuvaran D. ◽  
Satvik Shenoy ◽  
Srinivas G
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Rotational Speed ◽  
Total Pressure ◽  
Axial Flow ◽  
High Mass ◽  
Ansys Fluent ◽  
Industrial Sectors ◽  
Mass Flow Rates

Abstract Axial flow fans (AFF) are extensively used in various industrial sectors, usually with flows of low resistance and high mass flow rates. The blades, the hub and the shroud are the three major parts of an AFF. Various kinds of optimisation can be implemented to improve the performance of an AFF. The most common type is found to be geometric optimisation including variation in number of blades, modification in hub and shroud radius, change in angle of attack and blade twist, etc. After validation of simulation model and carrying out a grid independence test, parametric analysis was done on an 11-bladed AFF with a shroud of uniform radius using ANSYS Fluent. The rotational speed of the fan and the velocity at fan inlet were the primary variables of the study. The variation in outlet mass flow rate and total pressure was studied for both compressible and incompressible ambient flows. Relation of mass flow rate and total pressure with inlet velocity is observed to be linear and exponential respectively. On the other hand, mass flow rate and total pressure have nearly linear relationship with rotational speed. A comparison of several different axial flow tracks with the baseline case fills one of the research gaps.

Flow field and performance analysis of an integrated diverterless supersonic inlet

2011 ◽  
Vol 115 (1170) ◽  
pp. 471-480 ◽  
Author(s):  
J. Masud
Keyword(s):  
Mass Flow ◽  
Total Pressure ◽  
Critical Mass ◽  
Wind Tunnel Test ◽  
Flow Behaviour ◽  
Pressure Recovery ◽  
Duct Flow ◽  
Supersonic Inlet ◽  
Total Pressure Recovery ◽  
And Performance

Abstract In this paper the computed flow and performance characteristics at low angle-of-attack (AOA) of an integrated diverterless supersonic inlet (DSI) are presented. The subsonic characteristics are evaluated at M∞ = 0·8 while the supersonic characteristics are evaluated at M∞= 1·7, which is near the design Mach number for the intake. In addition to the external flow features, the internal intake duct flow behaviour is also evaluated. The results of this study indicate effective boundary layer diversion due to the ‘bump’ compression surface in both subsonic and supersonic regimes. At M∞ = 1·7, the shockwave structure (oblique/normal shockwave) on the ‘bump’ compression surface and intake inlet is satisfactory at design (critical) mass flow rate. The intake duct flow behaviour at subsonic and supersonic conditions is generally consistent with ‘Y’ shaped intake duct of the present configuration. The secondary flow structure inside the duct has been effectively captured by present computations. The computed intake total pressure recovery at M∞ = 1·7 exhibits higher-than-conventional behaviour at low mass flow ratios, which is attributed to unique inlet design. Overall computed subsonic and supersonic total pressure recovery characteristics are satisfactory under the evaluated conditions and are also in agreement with wind tunnel test data.

scholarly journals On-Sun Performance Evaluation of Alternative High-Temperature Falling Particle Receiver Designs

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Clifford K. Ho ◽  
Joshua M. Christian ◽  
Julius E. Yellowhair ◽  
Kenneth Armijo ◽  
William J. Kolb ◽  
...  
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Thermal Efficiency ◽  
Particle Temperature ◽  
Free Fall ◽  
Mass Flow Rates ◽  
Mesh Structures ◽  
Free Falling ◽  
The Impact

This paper evaluates the on-sun performance of a 1 MW falling particle receiver. Two particle receiver designs were investigated: obstructed flow particle receiver versus free-falling particle receiver. The intent of the tests was to investigate the impact of particle mass flow rate, irradiance, and particle temperature on the particle temperature rise and thermal efficiency of the receiver for each design. Results indicate that the obstructed flow design increased the residence time of the particles in the concentrated flux, thereby increasing the particle temperature and thermal efficiency for a given mass flow rate. The obstructions, a staggered array of chevron-shaped mesh structures, also provided more stability to the falling particles, which were prone to instabilities caused by convective currents in the free-fall design. Challenges encountered during the tests included nonuniform mass flow rates, wind impacts, and oxidation/deterioration of the mesh structures. Alternative materials, designs, and methods are presented to overcome these challenges.

Design of a Thermal Mass Flow Meter for Measurements Within the Rotor Rim Ducts of a Hydroelectric Generator

2018 ◽  
Author(s):  
Kevin Venne ◽  
Laurent Mydlarski ◽  
Federico Torriano ◽  
Mathieu Kirouac ◽  
Jean-Philippe Charest-Fournier ◽  
...  
Keyword(s):  
Mass Flow ◽  
Cost Effective ◽  
Thermal Mass ◽  
Complex Flows ◽  
Cfd Simulations ◽  
Flow Meter ◽  
Hydroelectric Generator ◽  
Computational Fluid Dynamics Cfd ◽  
Critical Components ◽  
Proper Operation

To ensure the proper operation of hydroelectric generators, their cooling must be well understood. However, the airflow within such machines is difficult to characterize, and although Computational Fluid Dynamics (CFD) can be a reliable engineering tool, its application to the field of hydroelectric generators is quite recent and has certain limitations which are, in part, due to geometrical and flow complexities, including the coexistence of moving (rotor) and stationary (stator) components. For this reason, experimental measurements are required to validate CFD simulations of such complex flows. Of particular interest is the quantification of the flow within the rotor rim ducts, since it is directly responsible for cooling the poles (one of the most critical components of a hydroelectric generator). Thus, to measure the flow therein, an anemometer was designed. The anemometer had to be accurate, durable, cost-effective, easy to install, and able to withstand the extreme conditions found in hydroelectric generators (temperatures of 45°C, centrifugal forces of 300 g, etc.). In this paper, a thermal mass flow meter and a method for validating its performance, using hot-wire anemometry and a static model of a rotor rim, are described. Preliminary tests demonstrate that the thermal mass flow meter is capable of i) measuring the mass flow rate in the rotor rim ducts with an accuracy of approximately 10%, ii) fitting inside small rectangular ducts (12.2 mm by 51 mm), and iii) resisting forces up to 300 g.

CFD Modeling and Simulation of a Catalytic Micro-Monolith

2011 ◽  
Vol 9 (1) ◽  
Author(s):  
Almerinda Di Benedetto ◽  
Valeria Di Sarli
Keyword(s):  
Mass Flow ◽  
Single Channel ◽  
Cfd Modeling ◽  
Cfd Model ◽  
Gas Velocity ◽  
Fuel Conversion ◽  
Flow Rates ◽  
Cpu Time ◽  
Mass Flow Rates ◽  
Computational Fluid Dynamics Cfd

In this work, a first step in modeling and simulating the thermal behavior of an entire catalytic micro-monolith was performed. In particular, a Computational Fluid Dynamics (CFD) model was developed for simulating three-channel and five-channel micro-combustors. For both configurations, the operating maps were built as functions of the inlet gas velocity and compared to the operating map of a single-channel configuration.Results show that, due to the relevance of heat losses in micro-devices, it is not possible to extrapolate the behavior of the multi-channel configurations from that of the single channel. Therefore, simulation of the entire catalytic micro-monolith is needed. However, this is computationally demanding: it has been found that the CPU time almost linearly increases with the number of channels simulated.Finally, for a fixed total mass flow rate, it has been demonstrated the opportunity to maximize the overall fuel conversion by means of a non-uniform distribution of mass flow rates among the channels.

scholarly journals De-risking flight trials using airwake simulations

2018 ◽  
Author(s):  
C M Ward
Keyword(s):  
Royal Navy ◽  
Exposure Limits ◽  
Cfd Simulations ◽  
Real Time System ◽  
Flow Features ◽  
Operating Limits ◽  
Turbulent Airflow ◽  
Computational Fluid Dynamics Cfd ◽  
The Impact ◽  
Rotary Wing

Air operations around naval vessels are inherently challenging and a major contributor to this is the turbulent airflow around the vessels, colloquially known as the airwake. To manage the risks associated with these unsteady airflows and to help define safe operating limits for the ship and the aircraft, the Royal Navy undertakes First of Class Flight Trials (FOCFTs). However, these trials inherently carry their own risks as well as being costly and time consuming. This paper discusses how Computational Fluid Dynamics (CFD) simulations have been used to de-risk flight trials and operations on the Queen Elizabeth Class (QEC) carriers. The simulations are shown to be in excellent agreement with full-scale LiDAR and anemometer measurements, which provides the requisite confidence to use them as a basis for de-risking. To de-risk the rotary wing FOCFTs, the turbulence approach parameter was defined as a proxy for pilot workload. It is shown that this parameter can be used to identify the wind conditions that are likely to be the most difficult for pilots, and to advise on changes to the approach paths that would reduce pilot workload. Test pilots were briefed with this airwake information prior to the FOCFTs, and the flow features identified in the CFD were found to be consistent with the pilots’ experiences. In the future this analysis could be used to reduce the time and cost associated with flight trials, manage through-life risks, and assess the impact of design decisions on the airwake during ship design. The work has also been used to de-risk F-35 trials and operations. In particular, the findings show that it may be possible to extend the operating envelope of the aircraft using a novel real-time system to predict airwake turbulence. In addition, CFD simulations were used to de-risk ondeck operations by ensuring that aircraft are within their exposure limits when tied-down. This information was used by the FOCFTs teams during rotary wing trials.

scholarly journals Computational study of a radial flow turbine operates under various pulsating flow shapes and amplitudes

2021 ◽  
pp. 1-24
Author(s):  
Ahmed Rezk ◽  
Sidharath Sharma ◽  
S.M. Barrans ◽  
Abul Kalam Hossain ◽  
P. Samuel Lee ◽  
...  
Keyword(s):  
Mass Flow ◽  
Radial Flow ◽  
Pulsating Flow ◽  
Gradual Change ◽  
Maximum Mass ◽  
Flow Rates ◽  
Flow Accumulation ◽  
Wide Range ◽  
Mass Flow Rates ◽  
The Impact

Abstract Radial flow turbines are extensively used in turbocharging technology due to their unique capability of handling a wide range of exhaust gas flow. The pulsating flow nature of the internal combustion engine exhaust gases causes unsteady operation of the turbine stage. This paper presents the impact of the pulsating flow of various characteristics on the performance of a radial flow turbine. A three-dimensional computational fluid dynamic model was coupled with a one-dimensional engine model to study the realistic pulsating flow. Applying square wave pulsating flow showed the highest degree of unsteadiness corresponding to 92.6% maximum mass flow accumulation due to the consecutive sudden changes of the mass flow rates over the entire pulse. Although saw-tooth showed a maximum mass flow accumulation value of 88.9%, the mass flow rates entailed gradual change resulted in the least overall mass flow accumulation over the entire pulse. These two extremes constrained the anticipated performance of the radial flow turbine operates under realistic pulsating flow. Such constraints could develop an operating envelop to predict the performance and optimize radial flow turbines' power extraction under pulsating flow conditions.

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