Increase In Pressure Ratio Research Articles

Experimental and numerical study of a fluidic oscillator frequency domain characteristics

Fluidic oscillators are fluid devices that provide steady flow at the inlet while generating unsteady flow at the outlet. This paper aims to investigate the frequency domain characteristics of internal pressure fluctuations in a specific type of fluidic oscillator to gain a deeper understanding of its dynamic behavior. The following conclusions were drawn: (1) Within a certain range, as the inlet-to-outlet pressure ratio increases, the oscillation frequency of the fluidic oscillator continuously rises, and the oscillation amplitude strengthens. (2) As the jet nozzle velocity increases within a certain range, the jet oscillation frequency exhibits a linear upward trend. These research findings provide essential academic and engineering guidance for designing and applying fluidic oscillators, assisting engineers in better understanding and controlling the device’s performance to meet the requirements of various application domains.

Investigation of static and rotordynamic characteristics of the segmented annular seals based on the differential quadrature method

Theoretically, a solution model for the static and rotordynamic characteristics of a segmented annular seal based on the local differential quadrature (LDQ) method was established. The impacts of node density and the number of local support domain nodes on the accuracy of the algorithm were analyzed. A test rig for the leakage of segmented annular seals was designed and built. The leakage results measured on the test rig were compared with the theoretical analysis results to demonstrate the accuracy of the local differential quadrature method. The influence of structural and operating parameters on the seal static and rotordynamic characteristics was analyzed Based on the work carried out above. The research results indicate that when the number of local support domain nodes is equal to 3, the static and rotordynamic characteristics of the segmented annular seal can be obtained accurately based on the solution model. As the rotational speed increases, the segmented annular seal’s lift force, leakage, stiffness coefficient, and damping coefficient increase. As the pressure ratio increases, the lift force and leakage of the segmented annular seal significantly increase while the stiffness and damping coefficients decrease. As the depth and width of the pocket increase, the lift force, stiffness coefficient, and damping coefficient of the segmented annular seal first increase and then decrease. As the length of the pocket increases, the lift force, stiffness coefficient, and damping coefficient of the segmented annular seal increase. The influence of the pocket depth, width, and length on the leakage is minimal.

Refrigeration experiments of gas wave rotor based on calibration-free WMS-TDLAS method

The refrigeration efficiency is mainly dependent on the low temperature generated by gas wave dynamics in oscillation channel. In this paper, a temperature rapid monitoring method for short light path based on the calibration-free wavelength modulation spectroscopy-tunable diode laser absorption spectroscopy (WMS-TDLAS) method is proposed. The selection of absorption wavelength, measurement procedure and data processing are specifically introduced. The wave dynamics and medium temperature under different pressure ratios and rotary speeds are studied, and the energy transfer efficiency of the gas wave refrigerator is evaluated. As the pressure ratio increases, the temperature in the cold zone behind the expansion wave gradually decreases to 257.6 K and the relative humidity of the cold zone inside the channel increases, which is caused by local condensation. At the same time, the expansion refrigeration efficiency is increasing from 27.3 % to 64.9 %. The increasing rotary speed of rotor also benefit to refrigeration efficiency from 45.8 % to 75.6 % as low temperature decreases to 252.1 K, which illustrates that rotary speed has more improvement effect on refrigeration efficiency than just higher-pressure ratio.

Analyzing the Impact of Pressure Ratio Variation on Gas Power Plant Performance at Takoradi Thermal Power Station

This study investigates the influence of pressure ratio variation on the performance of a gas turbine plant located at Aboadze, Ghana. The operational data including daily hourly measurements of pressure ratio, power output, ambient temperature, and gas fuel flow rate were collected during field visits conducted in February and March 2021. The thermal efficiency was computed using a validated equation, and data were analyzed using MAT LAB. The study reveals significant temporal fluctuations in the pressure ratio, power output, and thermal efficiency, highlighting the dynamic nature of the gas turbine plant's performance during daily operation. It was also observed that as the pressure ratio increases, the power output and thermal efficiency also increases and vice versa. The average highest and lowest pressure ratio recorded between February and March 2021 were 10.40 and 9.84 respectively, with corresponding average highest and lowest power output of 109 MW and 102 MW respectively. The result also showed an average daily variation in pressure ratio of 0.35 with corresponding power output difference of 5.25 MW. The finding showed that averagely, the lowest thermal efficiency and the highest thermal efficiency were 27.00 % and 28.00 % respectively.
 This study is of crucial importance for optimizing power generation efficiency and ensuring sustainable energy production. By studying a specific gas turbine plant located in Aboadze, Ghana, this research contributes valuable insights into the operational characteristics of such plants in the region.

A thermodynamic approach to analyze energy, exergy, emission, and sustainability (3E-S) performance by utilizing low temperature waste heat in SOFC–CHP-TEG system

Waste heat is one of the major problems associated with the energy system. This paper discusses an energy, exergy, and emissions approach for the hybrid system by utilizing waste heat to the maximum extent. A thermoelectric generator (TEG) is incorporated to utilize the low-temperature waste heat from a hybrid model of a solid oxide fuel cell (SOFC) and a combined heat and power (CHP) system. SOFC is an electrochemical cell that generates power at high temperatures through an electrochemical reaction. The high-temperature, unutilized fuel leaves the SOFC, which is burned in the afterburner. The afterburner temperature controls the operating temperature of SOFC. Here, three recuperators are used to utilize this high-temperature waste heat to improve the performance of SOFC and simultaneously generate heat power from the water or gas recuperator. TEG is an auxiliary power production technology that converts waste heat into energy. A novel integration of TEG with SOFC–CHP hybrid system to utilize the low temperature waste heat, is employed. The main goal of this study is to analyze a novel SOFC–CHP-TEG hybrid system in terms of its thermodynamics and emissions. A Two stage TEG is integrated with the SOFC–CHP hybrid system. The simulation model of high temperature fuel cell (SOFC) is developed on MATLAB and validated with published results. This study analyses the impact of pressure ratio and afterburner temperature on the performance of SOFC–CHP-TEG. To do this, perform energy and exergy assessments using the principles of the first and second laws of thermodynamics. A novel exergy-based sustainability index with emissions analysis for the proposed SOFC–CHP is presented. The achieved overall energy efficiency is 62.54% at a pressure ratio of 12 and an afterburner temperature of 1000 K. With an increase in pressure ratio and temperature, the level of CO emissions reduces significantly.

Study on the characteristics of a novel wrap-around cooled diaphragm compressor for hydrogen refueling station

This study introduces a novel wrap-around cooled diaphragm compressor, designed for employment in hydrogen refilling station. The performance of this innovative compressor is evaluated using a specially developed experimental platform. The analysis focused on the impact of pressure ratio and suction gas temperature on the compressor's performance, and the cooling effect is assessed under varying temperatures of the cooling medium. The findings indicate that both the isentropic and volumetric efficiencies of the diaphragm compressor decrease with an increase in pressure ratio, with maximum values reaching 70% and 65% respectively. Under constant pressure ratio conditions, the exhaust temperature is found to increase with the rise in suction temperature. For a given suction temperature, a higher-pressure ratio resulted in a higher exhaust temperature. Furthermore, the cooling effect of the wrap-around cooling pipeline is found to be more pronounced under high pressure ratio conditions, with a maximum temperature reduction of 189.5 °C.

Assessment of a combined heating and power system based on compressed air energy storage and reversible solid oxide cell: Energy, exergy, and exergoeconomic evaluation

The electricity grid with high-penetration renewable energy sources has urged us to seek means to solve the mismatching between electricity supply and demand. Energy storage technology could accomplish the energy conversion process between different periods to achieve the efficient and stable utilization of renewable energy sources. In this paper, a hybrid energy storage system based on compressed air energy storage and reversible solid oxidation fuel cell (rSOC) is proposed. During the charging process, the rSOC operates in electrolysis cell (EC) mode to achieve the energy storage by converting the compression heat to chemical fuels. During the discharging process, the cell operates in fuel cell mode for electricity production and the gas turbine is conducted to recover the waste heat from cell. To evaluate the comprehensive performance of the proposed system, the energy, exergy, and exergoeconomic studies are conducted in this paper. Under the design condition, the results indicated that the proposed system is capable of generating 300.36 kW of electricity and 106.28 kW of heating; in the meantime, the energy efficiency, exergy efficiency, and total cost per unit exergy of product are 73.80%, 55.70%, and 216.78 $/MWh, respectively. The parametric analysis indicates that the increase in pressure ratio of air compressor, steam utilization factor of rSOC stack under EC mode and current density of the rSOC stack under EC mode reduce exergy efficiency and total cost per unit exergy of product simultaneously, while the increment of operating pressure of rSOC stack under FC mode enhances the exergy efficiency and decreases total cost per unit exergy of product. The multi-objective optimization is carried out to improve the comprehensive performance of the proposed system, and the results expressed that the best optimal solution has the exergy efficiency and total cost per unit exergy of product of 65.85% and 187.05 $/MWh, respectively. Compared to the basic operating condition, the improvement of the proposed system has led to the maximum enhancement of 20.32% in exergy efficiency and 18.60% in total cost per unit exergy of product.

Structural performance of detachable precast concrete column-column joint

A novel type of detachable precast concrete column-column joint (DPC) is proposed in this study to solve the problems in current column-column dry connections including complex load path, uncertainty of structural stiffness of beam-column joints and inconvenience for disassembly. The dry connection technology is applied by composing of steel plate and concrete. Finite element models of DPC were created to study its structural performance including hysteresis curve, skeleton curve, ductility, and energy dissipation capacity. The benchmark models are firstly established and validated against the test data and after that a small-scale parametric study is prepared. The effect of axial pressure ratio and eccentricity distance size on the seismic performance of DPC was studied. Results indict that the optimal value of axial pressure ratio ranges from 0.5 to 0.7. With increase of the axial pressure ratio, the ductility coefficient shows a decreasing trend in general. The eccentricity has little effect on the energy dissipation capacity of the joint.

Experimental study on discharge coefficient of a cylindrical hole with gas jets in liquid crossflow

This study investigates the discharge coefficient of a cylindrical hole with gas jets in liquid crossflow in a cavitation tunnel. Utilizing the Π theorem, the research examines the dimensionless parameters influencing the discharge coefficient. The results indicate that an increase in the Froude number notably diminishes the discharge coefficient at low-pressure ratios, primarily due to intensified crossflow shear effects, which constrain the effective flow area of the gas jet. However, as the pressure ratio increases, the gas jet velocity rises, attenuating the shear effect of the liquid crossflow and augmenting the discharge coefficient. Examining the correlation between total pressure ratio and discharge coefficient reveals that below a total pressure ratio of 1, the inhibiting effect of crossflow static pressure on the discharge coefficient is more pronounced than that of dynamic pressure. Conversely, beyond a ratio of 1, dynamic pressure imposes a more substantial inhibiting effect compared to static pressure. Additionally, the study assesses the impact of the jet Reynolds number on the discharge coefficient, demonstrating that the viscosity of gas jet has a negligible effect compared to the shear effect of the liquid crossflow. Furthermore, it is found that with an increase in the Euler number, the discharge coefficient increases at the same pressure or velocity ratio, decreases at the same momentum ratio, and remains unchanged at the same momentum flux ratio. Comparing the effects of those above non-dimensional parameters on the discharge coefficient indicates that the momentum flux ratio is the most significant dimensionless parameter that affects the discharge coefficient.

Leakage performance of hybrid brush seals under high differential pressure conditions

A three-dimensional axial fluid-porous medium-flow field model was designed for the sealing properties of the hybrid brush seal (HBS) seal structure under complex operating conditions. Using a computational fluid dynamics model in view of non-Darcy porous media, the pressure and velocity distributions of the sealing medium in the flow path were simulated, and the flow characteristics of the hybrid brush seal were analysed to obtain the leakage of the hybrid seal structure. The results show the implication of pressure ratio (Rp) on the labyrinth brush seal leakage rate and pressure distribution. Compared with typical brush seal test results, as the inlet and outlet pressure ratio (Rp) increases, the more obvious the hybrid brush seal sealing effect is, when the pressure ratio is 3 bar, the spillage of the hybrid brush seal is reduced by about 39%.

Procena modela turbulencije za nestišljiv tok u venturijevoj cevi

Turbulence models are semi-empirical transport equations that model flow behavior. They are compared on a recurring basis to know which of them presents the best fit with experimental data for different laboratory equipment. In the present work, the incompressible flow field (water) is simulated with the computational fluid dynamics (CFD) tool and RANS model for the geometry of a Venturi tube in 2D computational domains, with the objective of evaluating six turbulence models: standard k-e, RNG k-e, standard k-o, SST k-o, RSM and SA. The numerical results of the trajectories of the pressure pattern curves at the walls and axial symmetry are close to each other. Pressure drops occur at the throat. The percentage errors of the turbulence models increase as the magnitude of the pressure ratio increases, for r p =1.0932, r p =1.1118, r p =1.1377, and r p =1.1531. It is concluded that the SA turbulence model of Spalart-Allmaras (1992) best fits the experimental pressure data, with percentage errors of less than 10%.

Проектирование электрических авиационных двигателей с капотированным вентилятором

All-electric power plant with ducted fan and electric motor driving the fan are reviewed in the article. This power plant is considered to be used on regional aircraft with a take-off thrust level of 73.5 kN on each power plant. To identify the most efficient fan total pressure ratio πВ* calculation studies were carried. Based on design calculations, according to a previously developed methodology, mathematical models of engines with πВ* equal to 1.4, 1.5 and 1.6 were formed. It has been determined that the optimal fan total pressure ratio increase are in the range 1,3…1.4, but the optimum is quite flat. It is shown that when πВ* decreases from 1.6 to 1.4 the required range of possible regulation of nozzle area in take-off conditions increases to maintain gas-dynamic stability margins due to stratification of lines in operating modes on the pressure characteristic of the fan. The main engineering contradiction has been identified – πВ* is needed to be reduced to achieve greater engine efficiency. However, this decision leads to an increase in mass of engine and the installation of a complex system of nozzle regulation. For the final choice of the most optimal value of πВ*, it is necessary to evaluate the flight-technical characteristics of an aircraft with engines having πВ* in the range of 1,4…1,6. In addition to the best efficiency of an engine, πВ* = 1.4 allows to achieve the highest available thrust. Such advantage can solve the problem of increase of the take-off weight of the aircraft due to added «heavy» hybrid or electric components (electric motors, electrical communications, batteries, etc.).

Thermoeconomic simulation of a complex energy system for performance analysis and prediction in deep peak shaving

The establishment of a cost model for complex energy systems based on thermoeconomics can provide technical and economic evaluation indicators for complex energy systems. At the same time, to integrate more renewable energy into the grid, complex energy systems must participate in deep peak shaving. To evaluate the technical-economic performance of complex energy systems involved in deep peak shaving, a novel thermoeconomic cost construction method is proposed based on the production structure diagram, using the gas-steam combined cycle system as an example. these can effectively avoid the derivation error of high-dimensional models, improve the modeling and calculation speed, and obtain the variation trend of system thermoeconomics cost under load changes and operating parameter changes. The results show that the external and internal factor can change the power generator thermoeconomic cost. the power generation cost of the system increases with increasing natural gas price and environmental temperature When the compressor pressure ratio increases, the power generation cost of the system also increases. At 100% load, the power generation cost reaches its lowest value when the exhaust temperature is equal to 615?C.

Experimental study of breakup and atomization characteristics of liquid carbon dioxide jet under high-pressure environment

Considering the working conditions of a Mg/CO2 rocket engine for Mars exploration, an experimental investigation was carried out to study the breakup and atomization properties of a liquid CO2 jet in a high-pressure environment. It is shown that the pressure ratio has a significant effect on the location and process of jet evaporation, resulting in significant difference in jet morphology and breakup characteristic. Two dividing points were identified, one near the CO2 triple point and the other near the saturation point. As the pressure ratio increases, the thermodynamic driving force for jet breakup weakens, leading to larger droplet sizes. The breakup length of the free round jet and Sauter mean diameter are functions of the Weber number and Jacob number, which are influenced by vapor content, injection velocity, and gas-liquid density ratio, in the mass flowrate range of 5.9–9.1 g/(mm2·s). A thermodynamic mechanism dominates when the ambient pressure in the atomize room is low enough, resulting in an unimodal distribution of droplet sizes. When the ambient pressure is in the range of 1–2.5 MPa, both thermodynamic and mechanical breakup mechanisms are active, resulting in a bimodal distribution of droplet sizes.

Modeling and optimization of two-stage compression heat pump system for cold climate applications

When an air source heat pump runs at very low ambient temperatures, several issues could arise and thus limit its applications. These issues include lower coefficient of performance (COP), deteriorated heat output and higher compressor discharge temperature resulting from an increased pressure ratio. Therefore, there is a need to develop more efficient heat pump systems for low ambient temperature (∼-30 °C) applications. Under this circumstance, it becomes advantageous to use devices in which the compression of refrigerant vapor occurs in two or more stages. Two-stage vapor compression heat pumps can operate more efficiently at a greater difference in temperatures between evaporator and condenser and improve their performance under cold climate conditions. In this study, a model for a two-stage compression heat pump system is developed with the system configuration containing a closed economizer cycle and inter-stage refrigerant injection. In the two-stage heat pump, the intermediate temperature and injection pressure (or displacement ratio) between low-pressure compressor and high-pressure compressor are important parameters that influence the operating performance. In this paper, the optimal intermediate parameters corresponding to the maximum possible COP have been determined. The performance of the two-stage heat pump using R410A and R290 are modeled and compared. It is shown that the two-stage heat pump achieves a COP of 2.85 and a COP of 2.7 at an ambient temperature of −30 °C using R290 and R410A, respectively. In addition, the optimized total fin surface areas of the evaporator and the condenser heat exchangers are calculated from the developed model.

Impact of spacer on membrane gas separation performance

Mixing in gas separation membranes has received much less attention than in membrane liquid separation because gas molecules have much smaller viscosity, allowing them to diffuse easily through membranes without requiring significant flow mixing. However, due to advancements in membrane fabrication technologies aimed at improving material properties, concentration polarization (CP) might become an issue in gas separation due to enhanced membrane efficiency and permeability. Consequently, a 2D CFD analysis is conducted to evaluate the impact of spacer-induced mixing on membrane gas concentration polarization for typical CO2/CH4 gas separation. Results show that spacers generally enhance flux performance while reducing CP in the membrane channel when compared to the case without spacers. Furthermore, the effectiveness of spacer-flux-to-pressure-loss-ratio (SPFP) reaches a peak for a Reynolds number in the range of 5 <Reh< 200 because of the trade-off between flux and pressure drop. This mixing-induced flux enhancement is most effective under high CP conditions (less mixing) within the membrane channel. Similarly, flux enhancement due to spacers can be observed as membrane selectivity, pressure ratio and feed gas concentration increase due to enhanced CP.

Thermodynamic feasibility and multiobjective optimization of a closed Brayton cycle-based clean cogeneration system

The present research has analyzed the energy and exergy of a combined system of simultaneous power generation and cooling. To provide a comprehensive data sheet of this system, the system has been investigated in the temperature range of 300–800 °C, and 6 working fluids, including air, carbon dioxide, nitrogen, argon, xenon, and helium, have been investigated. The parameters affecting the performance of the system, namely the compressor inlet pressure, the compressor pressure ratio, and the intermediation pressure ratio were investigated. The power produced by the Brayton cycle at a pressure ratio of 5.2 is the highest due to the increase in compressor power consumption and turbine power generation. The results of the parametric study showed that the exergy efficiency of the system has the maximum value at the pressure ratio of 4.73. The results of the parametric study showed that increasing the pressure of the compressor does not have a significant effect on the electricity consumption and the temperature of the working fluid due to the constant pressure ratio. The input energy to the heat exchanger of the absorption chiller decreases with the increase in the Brayton cycle pressure ratio, and as a result, the cooling created by the chiller also decreases. In this method, three objective functions of exergy efficiency, energy efficiency, and total production power are considered as objective functions. The most optimal value of intermediation pressure ratio was obtained after the optimization process of 1.389. Also, the most optimal value of the pressure ratio of high-pressure and low-pressure turbines was reported as 2.563 and 1.845, respectively.

Investigation on aeroelastic characteristics of mistuned low-speed axial compressor rotor: Numerical methodology and optimization

In this paper, the aerodynamic and aeroelastic characteristics of a low-speed axial compressor were explored by using a multidisciplinary optimization approach. The numerical methodology utilized the parametric benefits of the free-form deformation and Gaussian process-based Kriging in predicting and optimizing the aerodynamic performance (total pressure ratio and isentropic efficiency) and statistical results of forced response (mean μ and standard deviation σ of amplitude magnification) with frequency mistuning. Based on this point, an optimization framework was proposed, coupled with in-house codes for calculating the aerodynamic damping associated with flutter and vibration amplitude of the forced response. Since only the rotor blade was optimized, the exit flow angle at the rotor outlet combined with blade equivalent von Mises stress and aerodynamic damping were chosen as constraints. The results indicated that the total pressure ratio and isentropic efficiency experienced increases by 0.4% and 1.7%, respectively at the point near peak efficiency, while simultaneously achieving a statistical reduction in amplitude magnification. Specifically, aerodynamic analysis revealed that blade twist, backward sweep and forward lean can contribute to the improvement of aerodynamic performance. However, it should be noted that the forward lean of the blade tip led to an increase of equivalent von Mises stress on the blade pressure surface. From aeroelastic analysis, data mining results implied a negative correlation between blade twist and aerodynamic damping, indicating that, an increase in the blade twist angle led to a reduction in aerodynamic damping. These findings highlighted one of the significant conflicts between aerodynamic and aeroelastic performance. Additionally, a strong linear correlation was observed between the mean and standard deviation of forced response, which indicated that a larger blade amplitude magnification increased its sensitivity to frequency mistuning.

Computational study of lateral jet interaction in hypersonic thermochemical non-equilibrium flows using nonlinear coupled constitutive relations

The present study reports the numerical analyses of lateral jet interaction around a Terminal High Altitude Area Defense-type (THAAD-type) model in hypersonic rarefied flows, with the real gas effect incorporated. The computation approach employed is the recently developed thermochemical non-equilibrium nonlinear coupled constitutive relations (NCCR) model. Regarding the simulation conditions, the flight velocity and height are set to 20 Ma and 80 km, respectively. To disclose the flow mechanism of lateral jet interaction, the complex flowfield characteristics and surface pressure distributions are discussed at length. Additionally, the research explores the impact of two key factors, namely, the jet pressure ratio and the jet Mach number, on the control performance of an in-flight vehicle's reaction control system (RCS). The results demonstrate that the complicated flowfield structures in lateral jet interaction are successfully reproduced by the NCCR model. With an increase in either the jet pressure ratio or the jet Mach number, the force and moment amplification factors decrease, while the absolute value of the normal force coefficient increases. Notably, it is found that the rarefied gas effect captured by the NCCR model against the Navier–Stokes–Fourier solution affects the lateral jet interaction flowfield, e.g., weakening the compressibility of the barrel shock and the expansibility of the Prandtl–Meyer expansion fan, as well as strengthening the jet wraparound effect. Importantly, the rarefied gas effect also exerts a prominent influence on the performance of RCS, with the degree of influence diminishing as the jet Mach number or the jet pressure ratio increases.

Performance analysis of an organic Rankine cycle with an internal heat exchanger considering turbine pressure ratio and efficiency

This study investigated an organic Rankine cycle (ORC) that utilizes waste heat from ships. Steam at 170 °C generated by an economizer and either surface or deep seawater were used as the heat source and heat sink, respectively. Environment-friendly working fluids (hydrofluorocarbons, HFO) and conventional R-245fa were used for comparison. Energy and exergy analyses of the basic ORC and ORC with an internal heat exchanger (IHX) were conducted. In the basic ORC, R-1233zd(E) exhibited the highest efficiency. Comparatively, R-1336mzz-Z showed significantly improved efficiency upon IHX application. The IHX application allowed the working fluids to achieve efficiency improvement and decreased irreversibility of components, thereby increasing exergy efficiency. Although the higher pressure ratio at turbine produced a better output, a clear limitation in increasing pressure ratio more than 3.0 was observed due to the choking phenomenon. A distinguishing characteristic of the IHX cycle is its ability to compensate for efficiency decrease that occurs when lowering the pressure ratio to avoid choking by increasing the superheating degree. At a constant turbine inlet temperature (the sum of evaporation temperature and superheating degree the system efficiency at a pressure ratio of 2.99 was relatively 1.39 % higher than that at 3.58 owing to IHX application.