Mass Flow Ratio Research Articles

Performance evaluation and multi-objective optimization of an innovative solar-assisted multigeneration energy storage system for freshwater/O2/H2 generation

A novel multigeneration energy system encompassing a two-stage water purification unit, high-temperature solid oxide electrolysis cell (SOEC), heliostat solar field, and power generation cycles including organic and two-stage steam Rankine cycles is introduced in this study. The two-stage desalination system comprises humidification, dehumidification, and reverse osmosis units. A thermoelectric generator is also utilized to convert dissipated heat into electricity. The proposed system is comprehensively analyzed from energy, exergy, economic, and sustainability standpoints. The effect of design parameters such as heliostat concentration ratio, view factor, desalination mass flow ratio, SOEC operating temperature, and current density on the hydrogen, oxygen and freshwater generation rate, sustainability index, total cost rate, and overall performance of the energy system are discussed. Further, multi-objective optimization based on non-dominated sorting genetic algorithm (NSGA-II) is implemented to identify the optimal operating state of the system. Comparative assessment of the system in the actual condition in the Middle East region showed that the plant has higher performance in June compared to December. Also, optimization revealed that by choosing C = 988, P7 = 1500 kPa, P8 = 300 kPa, MFD = 2.5 and Tcell = 1250 K, the highest obtainable exergy efficiency and minimum total cost rate in the optimal operating state would be 11.32 % and 78.18 $/h, respectively.

MAINTAINING DECLARED PERFORMANCE IN GAS TURBINES DURING INCREASED AMBIENT TEMPERATURES

The classical gas turbine process is characterised by air compression from its surroundings, heating fuel in the combustion chambers, hence causing the created flue gases to expand in the turbine and thus induce mechanical action. The performance of gas turbine depends on anything that affects the airflow density and/or mass at the compressor inlet. The most obvious changes in gas turbine performance is a reduction in power and an increase in specific fuel consumption following an increase in the ambient temperature, resulting in significant deviations of the guaranteed (and achieved) values at ISO conditions. In cooling air at the compressor inlet at increased ambient temperatures, an increase in the mass flow and compression ratio is achieved, thus preventing a reduction in power and an increase in specific fuel consumption. When using gas turbines in combined cycle cogeneration power plants for the production of electrical and thermal power, increasing mass flow through gas turbines leads to an increase in power transferred by the flue gases to the turbine exhaust, and which in the waste heat recovery boiler at the combined cycle plant transfers to the steam turbine cycle. Consequently, the effect at the combined cycle plant is a more significant reduction in specific fuel consumption. The work has used the example of the GE-PG610FA turbine to show the dependency on surrounding climatic conditions, and the manner in which this dependency can be reduced or removed.

Effect of bubble cutting on spray characteristics and dust control performance in the effervescent atomization

Effervescent atomization performance depends on the bubble size inside the mixing chamber, consequently influencing the spray dust control performance. This paper proposes an optimization of atomization quality and dust control performance by incorporating a bubble cutter in the atomizer mixing chamber. The effects of the bubble cutter aperture on spray characteristics and flow characteristics were experimentally investigated under different operating conditions. Experimental results showed that Sauter means diameter (SMD) decreases with increasing injection pressure and gas-liquid mass flow ratio (GLR). Furthermore, SMD initially increased and then decreased by reducing the aperture of the bubble cutter from 500 µm to 80 µm. In particular, high injection pressure (Pi =0.6 MPa) and low gas-liquid mass flow ratio (GLR=0.09) strengthened the effects of the bubble cutter aperture on SMD. Moreover, bubble cutter causes a contiguous concentrated droplet size distribution, but it has little effect on droplet velocity. Ultimately, the optimal bubble cutter aperture on the efficiency of respirable dust control efficiencies was theoretically calculated. The dust control efficiency is a maximum at the bubble cutter with an aperture of 230 µm for the effervescent atomizer in this paper. Spray dust control efficiency reaches 93.15 %, which effectively solves the problem of high dust concentration pollution in the mechanized working environment.

Large Eddy Simulation of a Reacting Kerosene Spray in Hot Vitiated Cross-Flow

The evaporation and combustion characteristics of a kerosene spray injected perpendicularly into a cross-flow of high-temperature vitiated air is investigated. This fundamental flow configuration has wider implications for the future development of ultra-low emission aeronautical combustors, particularly with respect to technologies involving MILD combustion. Large eddy simulations with a Eulerian–Lagrangian framework are performed to investigate the spray evolution and the characteristics of the reaction zone for a range of conditions. For the closure of turbulence-chemistry interactions at the sub-grid scales, a transported probability density function approach solved by the Eulerian stochastic fields method is applied. A configuration based on the use of airblast atomisation is assessed first and compared with experimental observations. The effect of the atomiser air-to-liquid mass flow ratio is studied in greater detail, both in terms of the resulting gas-phase properties and the droplet evaporation process. Then, the effect of ambient pressure on the global spray flame behaviour is examined. For this part of the study, no atomising air is included in the simulation to separate the effects of ambient pressure on the spray from the interaction with the air jet. Analysis of the flame and spray properties at cross-flow operating pressures of 1 atm, 2 bar and 4 bar highlights the strong coupling between the reacting flow and droplet evaporation characteristics, which are highly affected by the penetration of the spray into a flow field characterised by relatively large gradients of temperature. The results reported in this work provide fundamental understanding for the development of novel low-emission combustion technologies and demonstrate the feasibility of applying large eddy simulation with detailed chemistry for the investigation of reacting aviation fuel sprays in hot vitiated cross-flow.

Critical evaluation of the thermal performance analysis of a new cooling tower prototype

This paper presents a critical evaluation of the thermal performance analysis of the inverted cooling tower, which was conceived as a new cooling tower prototype that prevents the dispersion of pollutants to the atmosphere during its operation. The device can be classified as a mechanical forced draft, counterflow-parallel flow cooling tower. The combination of the Merkel and Poppe methods of analysis and the counterflow, parallel and counterflow/parallel flow arrangements has been discussed, for a total of 5 different approaches. The Poppe method for thermal performance prediction reports higher Merkel numbers than the Merkel method: from 3.84% to 6.64%. A higher Merkel number is obtained for the parallel arrangement compared to counterflow to achieve the same cooling. Differences from 1.12% to 12.19% are observed for the range of tested water-to-air mass flow ratios. The rigorous method that uses the Poppe theory and combines counterflow and parallel flow arrangements (main novelty of this paper) is recommended to evaluate the thermal performance. Not only it provides the best predictions for the outlet water and air temperatures (0.44 °C difference for the water prediction and 0.74 °C difference for the air) but it is a good approximation of the complex underlying physics of the problem and the state of the outlet air is accurately determined. • A critical evaluation of the performance of a novel cooling tower was conducted. • The Poppe theory combining parallel/countercurrent flow arrangements is suggested. • The method predictions are confident: less than 2% for water and air temperatures. • The Poppe theory reports results 3.76% and 6.67% higher than the Merkel theory. • Parallel configuration provides up to 12.26% higher Merkel number than counterflow.

Evaluation of mist/air film cooling of C3X vane with serrate-type trenched holes

• Film cooling of C3X vane with serrate-type trenched holes using mist/air mixture under practical conditions is evaluated. • Both serrated transverse trench structure and addition of mist to air can significantly improve film cooling performance. • Replacing the trench edge by a double-curvature lip structure can further improve the film cooling effectiveness. • Film cooling effectiveness of the vane is reduced when the angle of the serrated trench is too large. • Vortex for the six trenched holes intensifies with the increase in the mass flow rate . Serrate-type trenched cooling holes have shown good film cooling performance for the cooling of turbine vanes using coolant air. Mist-assisted film cooling has also exhibited great potential for efficient cooling of a turbine vane. The combination of them may create a substantial improvement of cooling performance, which is explored in this simulation. This work studies the influence of serrate structure on the cooling performance of trenched holes for the C3X turbine vane under practical conditions by examining the flow and heat transfer characteristics of the mist/air mixture. The results prove the concept proposed for significantly improving the cooling performance. At the mass flow ratio R c = 0.25% ( M = 0.5) and R c = 0.50% ( M = 1.0), replacing the trench edge by a double-curvature lip structure can further improve the film cooling effectiveness. The film cooling effectiveness of the vane is reduced when the angle of the serrated trench is too large and the vortex for the six trenched holes intensifies with increasing mass flow ratio. The comparison of streamlines distribution and vortex structures at different blowing ratios by the Q criterion for the trenched holes in the flat plate reveals why the serrated trench structure can improve the cooling effectiveness: it can generate anti-counter-rotating vortices, making it difficult for the coolant film to separate from the wall. Although it is worth of further study on this novel design of serrated trench with mist/air film cooling under engine-representative conditions, this work provide heuristic guidance for the cooling of turbine vanes.

A Novel Control Algorithm of the Air Supply Subsystem: Based on Dynamic Modeling of Proton Exchange Membrane Fuel Cell

In this paper, a novel second-order active disturbance rejection control (2-ADRC) algorithm is proposed to optimize the control of the air supply subsystem for Proton Exchange Membrane Fuel Cell (PEMFC). To improve the optimal control effect of the air supply subsystem for PEMFC, the modeling theory of the air supply subsystem considering dynamic characteristics of the PEMFC system is first studied, and the dynamic Simulink model of the PEMFC system is established and verified. Then, the optimal oxygen excess ratio (OER) parameters under different load currents are obtained, and the optimal OER parameters are also used as the OER control reference for the designed algorithms. In addition, a 2-ADRC algorithm is designed and proposed to make the actual OER parameters close to the optimal OER in real time. Furthermore, compared with PID and MPC algorithms, the 2-ADRC algorithm can comprehensively consider the two parameters of mass flow and pressure ratio to make the compressor work in the high-efficiency zone and improve the net power and efficiency of the PEMFC system.

(Digital Presentation) Fabrication and Characterization for Vanadium Oxynitride Thin Films By Magnetron Sputtering

Vanadium oxynitride (VNxOy, x+y=1) is a metallic compound between vanadium oxides (VO, V2O3, V2O5) and vanadium nitride (VN) which would have interesting properties and functions that potentially can be supplied for different applications. In this study, vanadium nitride and oxynitride thin films were obtained by reactive magnetron sputtering using vanadium targets, Ar as plasma carrier, and a mix of N2 and O2 as reactive gas. The ratio of mass flow between the two gases is maintained around O2:N2=1:20 during the process. To obtain crystalline phases of oxynitrides a post rapid thermal annealing (RTP) in Ar atmosphere at 600ºC and 700ºC for 5 minutes was done. The purpose of the study is to define the effect of the magnetron sputtering parameters, such as reactive gas flow rates, and annealing temperature on the composition, microstructure, and optical properties of the obtained vanadium oxynitride thin films. The characterization of obtained films includes the examination of thickness and morphology by the surface profiler and SEM; identifying crystal structures and further microstructural vibration modes of molecular polarizability by X-ray diffraction and Raman spectroscopy, respectively; evaluation of the chemical composition of films by XPS analysis; assessing of optical transmittance, reflectance, and absorbance by the UV-visible- NIR spectrometer. Experimental data reveal that the annealed films can be oxynitrides when the oxygen flow rate is below 0.25 sccm and the ratio of oxygen/nitrogen ≤1/20. The annealed vanadium oxynitride films in terms of their properties are closer to vanadium nitrides than to oxides: more metallic than semi-conductive with dark appurtenance and high optical absorbance across the spectrum between 200 and 900 nm. The optical absorbance reaches almost 90% around 300 nm and then slowly reduces to 70% at 900 nm. Thus, these films could be good optical shields. For practical usage, the deposition of O2:N2=1/20, O2<0.25 sccm, and 600ºC annealing are recommended because of the truly low transmittance (<10%) through films.

Effect of rotor blade loading distribution on flow stability of transonic compressor

The stall inception prediction method based on eigenvalue theory is established to analyze the effect of rotor blade loading distribution on the flow stability of transonic compressors. The parameterization is implemented to describe the blade geometry with a number of control parameters. Four designs with different blade loading distributions are achieved by modifying the maximum thickness position of each element profile. The steady simulations show that the variation of rotor blade loading distribution leads to significant change of the steady performance incorporating pressure ratio and efficiency at all mass flow conditions. When the blade loading is located further downstream, the pressure rise curve moves towards smaller mass flow and higher pressure ratio, while there exists an optimal blade loading distribution that maximizes the rotor peak efficiency. According to the theoretical prediction, moving the blade loading downstream leads to a smaller stall inception mass flow rate. The rotor work, entropy generation and diffusion factor of the four rotors are analyzed to explain the performance difference. And the relative positions of passage shock and unsteady tip clearance flow at design and near-stall operating conditions are compared in detail to explain the stall onset distinction.

Investigations of bubble size distribution on swirl effervescent atomizer flotation

Atomizer flotation has the advantages of low cost, low energy consumption, adjustable, and long cycle life in industrial applications. The bubble diameter is an important parameter for floatation. The smaller the bubble diameter, the better the flotation effect. However, the bubble diameter produced by the atomizer during flotation separation is large at present. In this paper, a swirl effervescent atomizer is designed and experimental diagnosis through a spray measurement system and submerged spray visualization system. The diameter and size distribution of bubbles in 5 mm from the atomizer outlet to the jet cross-section spray were discussed. The results showed that the swirl effervescent atomizer obtained a fine Sauter mean diameter (SMD is 13–25 μm) compared with the traditional atomizer. Three flow patterns were observed at the submerged spray system: large bubbly flow, discrete bubbly flow, and slug flow. A statistical method of bubbles under high injection pressure was proposed. The effects of the operating conditions of the effervescent atomizer on the bubble diameter were investigated. The average bubble diameter decreased with the increase in injection pressure and gas–liquid mass flow ratios (GLR). However, with the GLR being increased to 0.15, the influence of injection pressure on bubble diameter was reduced. The backpressures (Liquid level heights) have less effect on bubbles compared with injection pressure and GLR. This paper has great significance for the sustainable development of the atomizer in the flotation separation application.

Numerical studies on the combustion of ultra-low calorific gas in a divergent porous burner with heat recovery

This study presents the idea of heat recovery through recirculating walls to enhance the combustion stability for ultra-low calorific gas in a porous burner. Numerical studies on the combustion of ultra-low calorific gas of CO/H2 with CO2 and N2 in a developed divergent porous burner with annular channel is conducted using two-dimensional axis symmetrical model with detailed kinetics. The heat recovery efficiency is defined as the ratio of heat recovery by the fresh mixture in the annular channel to burner power. It is shown that the heat recovery has significant effect on the minimal inlet gas temperature (MIGT) for stable combustion. It is confirmed that the heat recovery enhances the combustion and the stability limits are enlarged by preheating the fresh mixture, but it also leads to an extra pressure loss across the burner compared to that without heat recovery. Results show that heat recovery efficiency reaches up to 0.18 for all the investigated parameters and it reduces linearly from 0.32 to 0.18 as the mass flow ratio increases from 0.8 to 1.5. The MIGT for the burner with heat recirculating channel is always smaller than that without heat recovery. As a result, the combustion is greatly improved by the heat recovery in the divergent burner. Meanwhile, it is shown that pressure loss is increased significantly when the heat recirculating annular channel is added.

Detached Eddy Simulation of the Unsteady Flow and Film Cooling Characteristics of an Endwall With an Interrupted Slot

Abstract The flows close to a high-pressure turbine endwall are highly three-dimensional and unsteady. These flows increase the aerodynamic loss and augment the heat transfer. In this paper, the unsteady flows and film cooling characteristics of an endwall were studied by using the Detached eddy simulation (DES). First, the unsteady flows and film cooling characteristics of a slot on a flat plate were studied at three different coolant mass flow ratios. A comparison of the experimental and numerical results showed that the DES offered an improved ability to capture the distribution of film cooling effectiveness. The aerothermal characteristics of the interrupted slot on a vane endwall were then studied. By analyzing the unsteady flow as well as the mixing process, it was found that the shedding vortices produced by the step lip played a dominant role in the film cooling distribution and the formation of the horseshoe vortex. The coupling of the shedding vortices with the horseshoe vortex had an important influence on the film effectiveness on the endwall. Finally, the effect of the axial distance between the interrupted slot and the vane leading edge on the formation of the horseshoe vortex was further studied. The instantaneous vorticity contours showed that varying the axial position of the interrupted slot affected the development of the horseshoe vortex. As the axial distance increased, the horseshoe vortex disappeared periodically and then reappeared. As the axial distance decreased, the horseshoe vortex retained a steady pattern upstream of the vane leading edge.

Active Flow Control of Supersonic Jet Using Streamwise Pulsed Blowing

The present study investigates a novel control strategy to create a sweeping oscillatory jet using fluidic actuation principle. A supersonic underexpanded primary jet issued into a suddenly expanding duct is oscillated by giving cyclic pulsed secondary jet blowing in the top and bottom step regions of the suddenly expanding duct. The current study employs the bistable nature of jet expansion seen in a suddenly expanding duct for the jet oscillation. The cyclic perturbations (pulsed secondary jet blowing) given in the streamwise direction switch the direction of the asymmetric jet expansion of the underexpanded primary supersonic jet to the top and bottom wall alternatively, thereby creating an oscillatory supersonic jet. It is found that the switching of the direction of the primary jet to any one wall is caused by the Coanda effect produced by the secondary jet issued in the corresponding wall side. The results show that the primary jet quickly responds to the secondary jet perturbations and that the supersonic primary jet oscillation frequency nearly matches secondary jet perturbation frequency. A parametric study to investigate the jet oscillation characteristics with various secondary jet oscillation frequencies and mass flow rate ratios are also being carried out in the present study. It is found that the jet oscillation frequency increases with increase in the secondary jet pulsation frequency. The jet deflection is found to increase with increase in the secondary jet to primary jet mass flow ratio (blowing ratio) up to a critical limit, after which the increment in jet deflection ceases due to the restrictions imposed by the duct geometry.

Numerical study of kerosene spray and combustion characteristics using an air-blast atomizer

In this study, a computational model for a cylindrical combustor with an air-blast atomizer was created to investigate the effect of changing air to liquid mass ratio (ALR) on spray characteristics without combustion and the effect of changing ALR on combustion characteristics under different swirl numbers with constant kerosene fuel mass flow rate using computational fluid dynamics (CFD) code. The study aim is to define the ALR at which the pollutants concentrations at combustion exhaust will be the least. Eight values of ALR were considered and these include 0.3, 0.5, 0.7, 0.9, 1.0, 1.2, 1.4 and 1.5. The cold spray characteristics including the number of droplets, Sauter Mean Diameter, droplets penetration length and droplets contours were obtained in addition to combustion characteristics that were studied by describing the reverse flow zone (RFZ) boundary, flow pathlines, temperatures maps, outlet temperatures at combustor exit and species concentrations. The results indicate that increasing ALR and consequently spray droplet diameter decrease does not always translate into superior emissions performance and it depends on several parameters including swirling intensity where the modernistic capabilities of CFD code including flow visualization and calculated recirculated mass flow ratio are used to justify the reasons behind this exceptional behavior. In addition, the results show that the spray Sauter Mean Diameter decreases by increasing ALR but the droplet diameter reduction effect was steeper at lower ALR than higher ones. The length of the RFZ is decreasing with the increase of ALR and shifts upstream closer to the combustor swirler. The recirculated flow mass ratio and the outlet average temperature are decreasing with the increase of ALR.

Analysis and Performance Optimization of Supercritical CO2 Recompression Brayton Cycle Coupled Organic Rankine Cycle Based on Solar Tower

Abstract Supercritical carbon dioxide (SCO2) Brayton cycle has been proved to be an efficient power cycle to replace the traditional steam Rankine cycle. The thermal efficiency of SCO2 cycle can be further improved by coupling another type of cycle (the bottom cycle) at the waste heat end. A supercritical carbon dioxide recompression Brayton cycle (SCRBC) coupled organic Rankine cycle (ORC) based on solar tower is designed and established. According to the requirements of the waste heat temperature range of the top cycle, R600 is selected as the working medium of ORC. Under the design conditions, the effects of split ratio on the net power, the thermal efficiency, and the exergy loss of the combined cycle are studied. The variation of thermal efficiency of each part of the system with split ratio under different turbine inlet pressures and temperatures is further analyzed, and the influence of turbine inlet pressure and working fluid mass flow ratio ε (mass flow ratio of CO2 to R600) on the system performance is analyzed. Genetic algorithm-based multiobjective optimization is used to obtain the Pareto solution set for the thermal performance and unit investment cost of the system. The results show that the thermal efficiency of the combined cycle can be increased by more than 2% compared with that of a single top cycle. There is an optimal split ratio to maximize the thermal efficiency of the combined cycle, and the positions of the optimal split ratio are different for different turbine inlet pressures. Finally, through the multiobjective optimization method, several groups of Pareto solutions can be found, which can provide some reference for engineering design.

Investigation of cooling performance degradation of impingement/effusion structure on pressure side of nozzle guide vane

The cooling performance of the impingent/effusion structure on the pressure side of nozzle guide vanes tested in an engine operating for the various duration of 100 h, 300 h, and 500 h was evaluated in this study via infrared thermal imaging. The original vane was also examined as a comparison. The examined impingement/effusion structure consisted of 4 rows of impinging hole and 5 rows of film hole. The tested coolant-to-mainstream mass flow ratios was 0.0392–0.0784. Reynolds number was 624000 based on the vane chord and cascade inlet velocity. Cooling performance degradation in the impingent/effusion structure was investigated as it relates to oxidation and dust deposition after various durations of engine operation. The two-dimensional temperature distributions in the vane wall became nonuniform over time. The cooling performance quickly degraded after the vane was tested for 100 h in the engine; this degradation grew less intense as operation duration continually increased. The surface-averaged values of the overall cooling effectiveness of the impingent/effusion structure decreased by 9%–11% dependent on the mass flow ratio after the vane was tested for 500 h of engine operation. The coolant flow resistance increased with engine operation time as well.

Experimental study on the overall cooling effectiveness of nozzle guide vane under high temperature and high pressure

This study presents the overall cooling effectiveness of a nozzle guide vane with impingement-effusion in the conditions of the high temperature and high pressure at the mass flow ratios from KG = 0.09 to KG = 0.14. The temperature ratios change from KT = 1.9 to KT = 2.3 and the proportion of the mass flow rate through the first cavity and the second cavity is from KR = 0.9 to KR = 1.3. The examined gas temperature is raised to guarantee the actual temperature ratio and the matched Biot number with the engine. The local and averaged values of the overall cooling effectiveness on the mid-section profile of the vane are achieved more clearly. The experimental results reveal that the overall cooling effectiveness presents a weak performance on the trailing edge of the vane. The proportion of mass flow rate through two cavities has an obvious influence on the averaged overall cooling effectiveness at relatively low mass flow ratio of KG = 0.09. With the increasing of proportion of mass flow rate at the low mass flow ratio, an enhancement of overall cooling effectiveness in the region of the first cavity is observed. The averaged overall cooling effectiveness is remarkably influenced by the temperature ratio at relatively high mass flow ratio of KG = 0.14. With the increase of the temperature ratio from of KT = 1.9 to KT = 2.3, the averaged overall cooling effectiveness is improved by 7.5% and 6.7% respectively under two conditions of proportion of mass flow rate.

Leading edge impingement cooling analysis with separators of a real gas turbine blade

• Experiments of impingement cooling at real temperature conditions are conducted. • A new cooling design containing separators is suggested to prevent cross flow. • Deviation by using low temperature conditions of impingement cooling is presented. • Heat transfer data of impingement cooling are compared with published studies. This paper reports an analysis on leading edge impingement cooling of a turbine blade under real operation conditions of gas turbine. In the experiments, both mainstream and cooling air are heated to real high temperatures, and overall cooling effectiveness on the external blade mid-span surface is measured. Numerical strategy including RNG k-ε turbulence model is validated by the experimental data. Impingement cooling models with and without separators (Model A and Model B) are used as specimens, and the effects of high temperature conditions, separators and temperature ratios are discussed. The results indicate that: 1) When jet Reynolds number, mass flow ratio and temperature ratio are matched to the real conditions, the Nusselt numbers predicted by low temperature conditions can be generally matched, exclude the forepart of the internal surface at the blade leading edge. But the error of overall cooling effectiveness on the blade external surface is not neglected. 2) The application of separators can prevent the heat transfer deterioration caused by cross flow with extending the heat exchange area, thus the leading edge with separators can be further cooled over 30 K compared to the traditional design. 3) Under the real operating conditions of gas turbine, two new correlations between the surface averaged Nusselt number with jet Reynolds number and temperature ratio are suggested.

Flow Characteristics of a Mixed Compression Hypersonic Intake

The flow field in a two-dimensional hypersonic mixed-compression inlet in a freestream Mach numbers of M∞ =2.0, 3.0, and 5.0 are numerically solved to understand the effect of throat area variation. The exit area ratio variation is simulated by placing a plug insert at different axial locations at the exit of the model. The flow field is achieved computationally by solving the Reynolds Averaged Navier-Stokes equations in a finite volume framework. For each flow condition, the variation in shock structure is analyzed and the variation of the oblique shock wave angle with the mass flow rate is calculated theoretically and compared with the present CFD analysis. The variation in oblique shock angle is calculated in terms of the mass flow rate by considering the capture area and spillage flow through the inlet. The theoretical results suggest that the method can predict the inlet operating conditions at different freestream Mach numbers and area ratios. This method can quantify the reduction in mass flow rate due to the throttling effect by analyzing the flow field shock pattern. The effects of various important performance parameters such as free stream Mach number, total pressure recovery, and mass flow ratio were then numerically investigated. As the Mach number is increased, the total pressure recovery is reduced, but the maximum value of the mass flow rate is increased. The analysis is also focused on the effect of throat area variation on performance parameters at each Mach number. The characteristic curve of the inlet is then obtained for each free stream Mach number.

Film cooling performance on pressure side of turbine blade with different number of hole rows under rotating state

Film cooling is a major cooling method for turbine blades. Due to short film trajectories on the pressure side, the film coverage could be improved by increasing the number of hole rows. To study the effect of different hole rows on the film cooling performance of pressure side, this paper experimentally measures the film cooling effectiveness (η) of the pressure side with different number of hole rows (3, 4, and 5 rows) by employing pressure-sensitive paint (PSP) technology at a speed of 600 rpm. The effects of mass flow ratio (MFR), blowing ratio (BR), and hole arrangement (in-line and staggered) are analyzed. Numerical simulations are also performed for further analysis of the flow field. Under the mainstream parameters and blade structure in this study, the results show that: the three-row film hole cases have better film cooling performance at lower MFRs because of a larger film coverage; for four-row and five-row film hole cases, a belt region with poor film coverage appears at higher BRs, and the film cooling is influenced by the hole arrangement as well as behaves differently at lower and higher BRs.