Inlet Area Ratio Research Articles

Study on the influence of the blade inlet area-to-impeller inlet area ratio on hydraulic performance under various specific speed conditions

Abstract To investigate the unknown effects of the relationship between the impeller inlet area and blade design on the hydraulic performance of centrifugal pumps at various specific speeds within typical rotating fluid equipment, this paper aims to conduct experiments on three types of pumps with different specific speeds (ns =155, ns =125, and ns =88). The study analyzes how the S1/S0 ratio, which represents the blade inlet area to impeller inlet area ratio, affects the hydraulic performance of different centrifugal impellers. Furthermore, it explores the changing patterns of how the S1/S0 ratio influences the pump’s head and efficiency. The results indicate a recommended range of S1/S0 ratios for centrifugal pumps optimized for efficiency at different speeds. When considering the impact on cavitation performance, it is suggested that the S1/S0 ratio should not exceed the upper limit of this recommended range.

Blade retrofit design to reduce the noise of an axial flow fan by mitigating the tip leakage vortex

In the context of controlling axial fan aerodynamic noise, one effective approach involves the redesign of the blade. In the present study, a novel blade design was formulated for a specific model of axial flow fan, targeting the mitigation of the tip leakage vortex (TLV) and subsequent reduction of noise levels. The assessed noise-reduction blades have perforations drilled from the leading edge (LE) to the pressure surface (PS) of the blades. By impeding the tip leakage flow (TLF), these perforations effectively weaken the TLV. The three-dimensional non-constant flow field within the channel is computed employing the shear stress transport (SST) turbulence model. The aerodynamic noise prediction, which is based on the Lighthill’s acoustic analogy theory, shows that the designed blades can effectively reduce the aerodynamic noise of the axial fan. Specifically, enhancing the ratio of inlet area to outlet area of the ventilation holes leads to an improved noise reduction effect. Notably, for ratios of 0.44 and 1.06, the designed blades exhibit noise reductions of up to 3.3 dB(A) and 3.9 dB(A), respectively. Meanwhile, the static efficiency of these two fans is reduced by 0.50% and 0.26%, respectively. The study thus provides good theoretical support for the design of axial flow fans in the context of noise reduction.

Influence of Inlet and Outlet Area Ratio on Intake Port Flow Capacity

The flow capacity of the intake port has a great influence on the charging efficiency of the internal combustion engine, affecting the engine’s performance, so it is critical to improve the intake port flow capacity. In this paper, the intake port numerical model was established, and the influence of the inlet and outlet area ratio on intake port flow capacity was studied. The results show that, under the same condition of relative pressure difference, the intake port discharge coefficient increases sharply and then slowly with an increase in area ratio. Under the same condition of area ratio, the discharge coefficient is only determined by relative pressure difference and decreases with an increase of relative pressure difference when the inlet and outlet area ratio>1. The optimal area ratio decreases and then converges with an increase in relative pressure difference. When the intake port is designed, the optimal area ratio under the working condition of a smaller relative pressure difference should be applied in order to ensure the discharge coefficient is optimal under all working conditions.

Numerical study on rotating detonation combustion with the discrete distribution of partially pre-vaporized n-heptane sprays

The rotating detonation engine (RDE) is a novel aerospace propulsion device, with liquid fuel playing a pivotal role in enabling the practical implementation of the RDE. The Eulerian-Lagrangian simulation is used to analyze a two-dimensional rotating detonation combustion with partially pre-vaporized n-heptane sprays. The investigation aims to examine the influence of various inlet area ratios (ψ) on both the droplet evaporation and rotating detonation combustion within the combustion chamber. The findings indicate that a smaller ψ is advantageous for droplet evaporation within the fuel filling area, and the droplet traverses sequentially through the acceleration layer, the deceleration layer, and the re-acceleration layer within this region. With a relatively large ψ, a burned gas bump becomes evident on the deflagration surface, augmenting the evaporation rate of droplets within its proximity. The droplet continues to accelerate within the fuel filling area, while its velocity remains low at the burned gas bump. Furthermore, spot-like diffused flames emerge subsequent to the RDW, with their area expanding to the increase in ψ. Meanwhile, the average heat release rate (HRR) and thrust within the combustor of the rotating detonation engine (RDE) demonstrates diverse oscillation patterns in response to changes in ψ. In this study, when the inlet area ratio is around 0.6, the RDE obtains the most stable average HRR and thrust.

Experimental study on tesla valve and bypass manifold to suppress feedback of rotating detonation engine fuel by kerosene

In this paper, the effects of the Tesla valve intake structure with or without bypass manifold on suppressing pressure feedback and combustion product backflow in rotating detonation engine fueled by kerosene and enriched air with 29% oxygen content are investigated, with the configuration of convergent–divergent intake without bypass manifold being used for comparison. The working range, detonation wave propagation characteristics, and propulsion performance for the three configurations are evaluated. It is found that the Tesla valve intake structure can effectively improve the suppression of pressure feedback and combustion product backflow through the diversion function of the Tesla valve bypass channel and that the addition of the bypass manifold further improves the suppression of pressure feedback. The Tesla valve intake with bypass manifold configuration has the best ability to suppress pressure feedback, with a minimum value of pressure feedback percentage of about 6.5% and a minimum value of air plenum pressure fluctuation percentage of about 6.7%. By comparison, the minimum value of pressure feedback percentage of the convergent–divergent intake without bypass manifold configuration is about 29.8%, and its minimum value of pressure feedback percentage is about 7.8%. The Tesla valve intake without bypass manifold configuration is most effective in suppressing combustion product backflow, with the effective inlet area ratio of about 95.7%. Under the same conditions, the minimum effective inlet area ratio of the convergent–divergent intake without bypass manifold configuration is about 90.2%. Ultimately, optimizing the engine structure leads to a broader working range and higher propulsion performance. The Tesla valve intake structure broadens the working range by suppressing the generation of the longitudinal pulsed detonation mode. When the bypass manifold is incorporated, some combustible reactants directly enter the rear of the combustion chamber from the head of the chamber, and the working range is reduced. Compared with the convergent–divergent intake without bypass manifold configuration, the working range of the Tesla valve intake with bypass manifold configuration is widened by 383.3%, and that of the without bypass manifold configuration by 700%. Both the Tesla valve intake and bypass manifold increase the strength of detonation waves and improve propulsion performance. The Tesla valve intake with bypass manifold configuration has the highest specific thrust, at about 90.1 N s3/(kg·m). This is increased by an average of 10% compared with the Tesla valve intake without bypass manifold configuration, and by an average of 30.1% compared with the convergent–divergent intake configuration.

Experimental study on suppressing pressure feedback and combustion product backflow of the rotating detonation engine

To further improve the feedback suppression effect of rotating detonation engines (RDEs), an optimized Tesla valve inlet structure (TVI-II) was designed on the basis of the previous research of our research group. Taking kerosene and 29% oxygen-enriched air as the reactants, the operation characteristics, the feedback suppression effect, and the feedback suppression mechanism were obtained through a series of experiments. It is found that due to the existence of bypass channel, TVI-RDE can effectively suppress the occurrence of longitudinal pulsed detonation and broaden the working boundary of the engine. The working range of the TVI-I-RDE was broadened by 183.3%, and that of the TVI-II-RDE was broadened by 700%. The TVI-II-RDE is more effective in suppressing pressure feedback and combustion product backflow. When the pressure feedback phenomenon occurs, the rotating detonation wave mainly decoupled and attenuated in the converging section of bypass channel. The minimum pressure feedback percentage (PFdw) of TVI-II-RDE was 11.4%, as compared to about 40% for the TVI-I-RDE. The change law of the air plenum pressure fluctuation percentage (PFap) was similar to that of PFdw, and the minimum PFap of the TVI-II-RDE was about 7.7%. Narrower bypass channel width would lead to longer residence time of combustion products. The effective inlet area ratio (EA) of the TVI-II-RDE was at least 95.7%, which is at least 6.1% higher than that of the CDI structure. The results show that the TVI-II-RDE has great potential in suppressing feedback, which promotes the engineering application of RDE.

Optimum design of S-shaped diffuser by studying the effect of inlet velocity, turning angle and area ratio

Optimum design of S-shaped diffuser by studying the effect of inlet velocity, turning angle and area ratio

Preliminary Criterion for Positive Total Pressure Gain in Kerosene/Air Rotating Detonation Combustor

The rotating detonation combustor is promising to be a total pressure gain combustor and receives considerable attention in the past decade. Many studies have pointed out that the pressure gain performance is significantly related to the inlet area ratio, whereas no criterion for obtaining positive total pressure gain has been established until now. This study performed a series of numerical simulations to investigate the idealized total pressure gain performance of vapor kerosene/air rotating detonation combustor by varying the inlet area ratios and injection total pressures. A preliminary criterion for obtaining positive total pressure gain in vapor kerosene/air rotating detonation combustor is established and then validated with simulation cases and existing research. The results indicate that the total pressure gain increases with the increase of the inlet area ratio and chamber diameter, whereas it decreases with the increase of the injection total pressure. The established criterion can serve as a reference value for the design of the vapor kerosene/air rotating detonation combustor, above which a positive total pressure gain can be obtained.

On the mechanisms of the multiplicity and bifurcation of detonation waves in 3D rotating detonation engines

The mechanisms of the multiplicity and bifurcation of detonation waves in 3D rotating detonation engines (RDEs) with cavity combustor and array-holes injection are numerically investigated. Array-holes injection is adopted to mimic the discontinuous distribution of reactants in real RDE experiments. Four kinds of injection patterns with different inlet-area ratios and four RDE models C1 - C4 of different cavity depths are employed. The result shows that as the inlet-area ratio increases the detonation waves number decreases generally. A more underlying mechanism of the multiplicity is assumed that the multiplicity of detonation waves is closely related to the inhomogeneous distribution of the detonable reactants, and the decrease of homogeneity of the detonable reactants (HDR) level causes the increase of wave number. The relative frequency's variance of the detonable mixture, as a metric of the HDR level, is calculated and the results show that the wave count decreases as the variance of the relative frequency decreases, which testifies to the rationality of our hypothesis. Model C2 shows a mode-locked state and exhibits a likelihood that the detonation mode may be more stable in these RDEs of specific configuration. Additionally, the process of bifurcation in cavity RDEs is tortuous, which is because the frequent disordered collision and quenching in the cavity delay the stable detonation waves' formation. And the mechanism of the periodic bifurcation in annular RDEs is related to the periodic distribution of the detonable reactant, which is verified by comparing the HDR level at different instants. The mode stability and propulsive performance are also mentioned and the cavity RDEs show a promising prospect in some cases.

Effect of Opening Size on the Development of Ventilation-limited Fire

There are many factors, that affect the development of indoor fire, such as the size of the fire source, the opening or space of the room, and the nature of the combustible materials. Among them, the space of the room, has a significant impact on the development of a ventilation-limited fire. In this paper, the Fire Dynamics Simulator (FDS) software is used to analyze, the risk of fire initiation in the restricted ventilated compartment, when the size of vertical ventilation space is different. Through, a combination of experimental design, numerical simulation, and theoretical analysis, the changes in the level of carbon monoxide, visibility, temperature, Heat Release Rate (HRR) and, the smoke exhaust efficiency of natural smoke at different opening sizes are observed. It is observed that, when the ratio of inlet and outlet area reaches 2:1, the natural smoke exhaust effect is the best, however, the increasing in the opening size has little significance on the smoke exhaust effect. The research on the influence of smoke outlet size, will helps in the development of the law regarding fire prevention, smoke exhaust design, and fire rescue work of a building.

Effects of Divergence Inlet on Kerosene/Air Rotating Detonation Engines

In this paper, an improved three-dimensional conservation element and solution element method with chemical source terms is developed and applied to investigate the effects of different divergence inlet patterns on vapor kerosene/air rotating detonation engines. A two-step kerosene/air chemistry model is adopted and solved by a third-order Runge–Kutta method. A series of cases with varying the slot inlet width, in other words, 6, 4, and 2 mm, and divergence section length, in other words, 4, 6, and 10 mm, are simulated. The simulation results indicate the supersonic injection generated by the divergence section is helpful to decrease the disturbance from the downstream flow. Affected by the divergence section, the detonation front is divided into two sections, in other words, the main detonation front and the banded detonation front. For the main detonation front, the detonation strength on the outer wall is significantly stronger than that on the inner wall, while it is not for the banded detonation front. The total pressure loss caused by the inlet normal shock significantly increases with the decrease of slot inlet width. A declining deflagration surface will appear when a small slot inlet width of 2 mm is used. The rotating detonation engine (RDE) performance analysis shows that the slot inlet width has a significant impact on the thrust, specific impulse, total pressure gain, and outlet Mach number. A bigger slot inlet area ratio contributes to a higher total pressure gain. The simulation results can get insight into rotating detonation behaviors and guide the development of the kerosene/air RDE.

Research on performance optimization of gas–liquid ejector in multiphase mixed transportation device

ABSTRACT In the process of oil and gas extraction, a system that uses a pump and reversing mechanism to achieve high-efficiency export of gas–liquid mixture is devised. A gas–liquid ejector is fitted in the front of the device to boost pressure inside the tank in order to store more gas in the tank under a given volume. To meet the working conditions of gas–liquid high-efficiency transport device and obtain a larger outlet pressure and better ejection performance, this paper investigates the effect of outlet pressure, ratio of throat inlet area to nozzle outlet area and nozzle contraction angle on the ejection performance of gas–liquid ejector, and simulations using the computational fluid dynamics approach. At the same time, an experiment platform is built for testing. The research findings show that the ejection gas flow rate and ejection ratio of gas–liquid ejector decrease with the increase of the outlet pressure; as the ratio of throat inlet area to nozzle outlet area increases, the ejection gas flow rate and the ejection ratio of gas–liquid ejector increase first and then decrease. Different nozzle diameters correspond to different optimal area ratios; under the specified working parameters, with the increase of the nozzle contraction angle, the ejection gas flow rate and injection ratio of the gas–liquid ejector increase first and then decrease, and there is an optimal nozzle contraction angle.

Numerical Study on Effects of Geometric Parameters on the Release Characteristics of Straight Sudden Expansion Gas Extinguishing Nozzles

In order to guide the optimization design of the nozzle of the aircraft-fixed gas fire extinguishing system, we studied the influence of nozzle geometric parameters including outlet–inlet area ratio, length–diameter aspect ratio, and wall roughness on the distribution of pressure and velocity in the nozzle on the basis of CFD simulations. Although the structure of the nozzle is axisymmetric, the spatial distribution of the pressure and velocity during the flow and release of gas extinguishing agent is not completely symmetric. It was found that both of the outlet–inlet area ratio (δ) and the length–diameter aspect ratio (ξ) had a significant impact on the distribution characteristics of the pressure and axial velocity in the nozzle. With the increase of δ, the average pressure at the outlet cross-section of the nozzle decreased monotonically, while the average axial velocity at the outlet increased approximately linearly. When ξ≥2, the uniformity of the pressure and velocity distribution at the nozzle outlet was significantly improved. Moreover, with the increase of ξ, the average pressure and the average axial velocity of the outlet both showed a non-monotonic change trend, and the optimal value of ξ should be about 3.0. Compared with δ and ξ, the influence of the nozzle wall roughness (εN) on the flow and release characteristics of the extinguishing agent was weak. With the increase of εN, the average pressure of the nozzle outlet increased slightly, while the average axial velocity at the nozzle outlet decreased slightly.

Prediction of lean blowout performance on variation of combustor inlet area ratio for micro gas turbine combustor

PurposeThis paper aims to predict the effect of combustor inlet area ratio (CIAR) on the lean blowout limit (LBO) of a swirl stabilized can-type micro gas turbine combustor having a thermal capacity of 3 kW.Design/methodology/approachThe blowout limits of the combustor were predicted predominantly from numerical simulations by using the average exit gas temperature (AEGT) method. In this method, the blowout limit is determined from characteristics of the average exit gas temperature of the combustion products for varying equivalence. The CIAR value considered in this study ranges from 0.2 to 0.4 and combustor inlet velocities range from 1.70 to 6.80 m/s.FindingsThe LBO equivalence ratio decreases gradually with an increase in inlet velocity. On the other hand, the LBO equivalence ratio decreases significantly especially at low inlet velocities with a decrease in CIAR. These results were backed by experimental results for a case of CIAR equal to 0.2.Practical implicationsGas turbine combustors are vulnerable to operate on lean equivalence ratios at cruise flight to avoid high thermal stresses. A flame blowout is the main issue faced in lean operations. Based on literature and studies, the combustor lean blowout performance significantly depends on the primary zone mass flow rate. By incorporating variable area snout in the combustor will alter the primary zone mass flow rates by which the combustor will experience extended lean blowout limit characteristics.Originality/valueThis is a first effort to predict the lean blowout performance on the variation of combustor inlet area ratio on gas turbine combustor. This would help to extend the flame stability region for the gas turbine combustor.

Effects of Feeding Mode and Inlet Area Ratio on Heating Characteristics in Dual-Inlet Swirl Tubes

A preheating exchanger is developed for improving acidic water degassing. Reasonable optimization of dual-inlet swirl heating tubes is analyzed by computations of the flow and heat transfer. The comparisons of the swirl number and circumferential average Nusselt number between isobaric injection and isokinetic injection are performed. Inlet area ratios ranging from 0.1 to 0.9 exhibit an important influence on the flow phenomena and the heating performance. A lower value of inlet area ratio leads to the tendency for the fluid passing through inlet 2 to move upstream of inlet 2 and results in more vortex pairs between inlets 1 and 2. An inlet area ratio value of 0.5 exhibits the largest global average Nusselt number, normalized Nusselt number, and thermal performance factor. The optimized inlet area ratio is suitable for improving the degassing efficiency.

Study of double-chamber air arc plasma torch and the application in solid-waste disposal

Arc plasma can be applied in hazardous solid waste disposal for higher temperature than common heating methods, but some practical issues exist in practical engineering application. In this study, an air arc plasma torch with double chambers and magnetic controlling is designed to realize wide variable power and long electrode life. The detailed characteristics and laws of the air arc are studied. The condition parameters of arc current (I), air flow rate (G) and the structure parameters of inlet area ratios and electrode diameters influence both the arc voltage and arc root positions. The arc rotating driven by magnetic field effectively lengthens the electrode life. The gasification process and product of organic wastes by air plasma are influenced largely by the waste compositions and the air flow rate. A furnace structure with more even atmosphere and longer residence time should be considered for better gasification. Oxygen-deficient environment is important to suppress NO x formation during the application of air plasma. Inorganic solid wastes can be melt by the air plasma and cooled down to form compact vitreous structures in which heavy metals can be locked and the leaching rates significantly decrease down.

Propagation behavior of rotating detonation waves with premixed kerosene/air mixtures

The propagation of multiple detonation waves in the two-dimensional modeled rotating detonation combustor fueled by premixed kerosene/air mixtures is numerically investigated with a reduced two-step global chemical mechanism. Discrete fuel injection model is adopted to simulate the discontinuous distribution of reactants in Rotating Detonation Engine (RDE) experiments. A parameter inlet-area ratio (ψ) is proposed to obtain the reactants with different dispersion degree. This work focuses on the effect of discontinuous reactants on detonation cells and overall flow-field structure of rotating detonation waves. The results show that with full-area injection model (ψ=1.0), the reactants distribute continuously in triangular gas layers. Rotating detonation waves propagate stably with regular detonation cellular structure. When ψ is less than 1.0, the injection reactants are distributed in strips. At the position far away from the head-end wall of combustor, the fresh reactants and combustion products are mixing with each other which causes the deflagration zones in triangle gas layers. The reactants remaining after deflagration process in deflagration zones cannot support the propagation of detonation leading to the partially decouple of detonation front. The large area of deflagration zones distorts the flow-field structure and reduces the propulsion performance of combustor.

Experimental and numerical investigation of die designs in biomass pelleting and the effect on layer formation in pellets

Design parameters of a pellet mill die for pellet production are essential for running optimal pellet production in terms of energy consumption and quality of the pellets. In this study, the effects of the countersink angle and depth are investigated through experimental tests and Computational Fluid Dynamics (CFD) simulations. Inlet die designs with angles 0°, 60°, and 100° and three different depths, were tested via single pelleting tests with spruce. A new design parameter, AR, is suggested for comparison of the dies performances. The parameter is derived from the die's surface area, and is the ratio of the die's inlet area vs. total surface area and values tested here ranged 0.35 to 1. Specific energy consumption and mechanical pellet durability were measured experimentally, and the feedstock layer profiles in pellets were qualitatively analyzed via image processing. The layer profiles in the pellets were simulated with a CFD model using a simple Bingham viscosity model. The model was validated by comparing the simulated and experimentally obtained layer profiles. The results show that the lowest energy consumption was obtained with a 60° countersink and an AR value of 0.6–0.8. Furthermore, an AR value in this range were found to be optimal with respect to pellet durability. Analysis of the layer profiles shows interesting differences in the layer profiles of the pellets, and evaluation of the kurtosis of the layer profiles suggests that this can be used to predict the pellet durability and, thereby, the quality of the die design.

Performance evaluation of simple radial fin design for single phase liquid flow in microchannel heat sink

This paper numerically investigates heat transfer performance and characteristics in single-phase liquid cooling in microchannels with radial arrangement of fins having inherent symmetry to mitigate the problem of flow maldistribution. The effects of number of fins, channel depth and flow rate on Nusselt number and substrate temperature are obtained. The relative thermal performance and overall efficiency are compared with respect to two different base cases having minimum number of channels and minimum channel depth. For increasing values of flow rate and channel depth, contradicting effects in terms of temperature uniformity are obtained. By varying only number of channels, has no significance until it is coupled with channel depth, which suggests that aspect ratio of inlet cross-sectional area should be considered as a significant factor which is capable of generating secondary flows in single phase liquid flows. The overall efficiency of case with 70 number of channels, 200 µm depth and 15 ml/min is found to be highest.

Flow-field analysis and pressure gain estimation of a rotating detonation engine with banded distribution of reactants

The flow-field structure and pressure gain performance of a rotating detonation engine with banded distribution of reactants have been studied using two-dimensional numerical simulations. The reactants are premixed H2/Air mixture. An unsteady reacting flow solver named rhoHLLCFoam is developed based on the open source software OpenFOAM. Unsteady Reynolds Averaged Navier-Stokes (RANS) equations are solved with second order accuracy in space and time with Harten-Lax-van-Leer-Contact (HLLC) Riemann scheme. The solver resolves the combustion phenomena through finite rate chemistry reaction model with Arrhenius form of reaction rate by using Ó Conaire scheme. After checking the reliability of the solver, two sets of cases with various inlet-area ratios (ψ) and equivalence ratios (ϕ) are conducted. The result shows that with ψ<1.0, the reactants in front of detonation waves present a discretely banded distribution which causes a series of reverse compression waves in flow-field. This paper estimates the specific impulse and specific thrust of combustion chamber. It's shown that these parameters increase with the promotion of ψ. By calculating the area-averaged stagnation pressure along axial direction of combustion chamber, the pressure gain ratio (η) of the rotating detonation engine is estimated. The result suggests that η decreases dramatically with the reduction of ψ. In order to achieve pressure gain, ψ must be greater than 0.60. Moreover, the equivalence ratio should be around unity to obtain higher value of η.