Inlet Orifice Research Articles

Numerical simulation and experimental study of the influence of disk groove structure optimization on the air film flow field signature of an air-cushion sandwich belt conveyor

A new type of disk groove mechanism was developed and manufactured. The effects of the structural and operating factors of the disk groove on the air film loading performance were examined using single factor and orthogonal experimental methods. The results of numerical simulation and experimental studies showed that the air film loading performance correlated positively with the orifice diameter and inlet pressure, with the orifice spacing and diameter having the most significant effects, and that the belt speed boosted the air film uniformity. Meanwhile, a comparative analysis of the corresponding level values showed that an air film thickness of 0.8 mm, orifice diameter of 5 mm, orifice spacing of 30 mm, inlet pressure of 8000 Pa, and conveyor speed of 5 m/s were the optimal parameter combinations for the maximum loading capacity. To verify the accuracy of the model, a field experiment was conducted at Jiangmen Southern Conveying Machinery Engineering Co., Ltd. The air film pressure at the experimental position matched the numerical simulation results. In addition, when the number of rows was one and the air volume was 10 m3/h, the smallest value of traction resistance was obtained under minimum power consumption.

Sensitivity Analysis of Injection Mass Flow to the Inlet Orifice Radius of a GDI Injector Nozzle

It is more difficult to accurately control the cycle fuel mass of a gasoline engine as the injection pressure increases, and the difference in the injection mass flow will become intense due to the machining error of GDI injector structural parameters. In order to guarantee the uniform cycle fuel mass of the GDI injector, this paper investigates the effect of the inlet orifice on the injection mass flow and the sensitivity of inner-flow characteristics in the GDI injector nozzle to the inlet orifice radius by the single factor analysis method. The results show that the local resistance of the injector nozzle will decrease and the discharge coefficient will rise due to the increase in the inlet orifice radius; the sensitivity of cycle fuel mass to the inlet orifice radius is most strong at r = 0.02 mm, and its accuracy should be improved when grinding the chamfer of the nozzle inlet; the sensitivity coefficient of the inlet orifice radius will rise up, and the machining accuracy of the inlet orifice radius should be improved as there is an increase in injection pressure.

A constant pressure differential valve and its controlling characteristics for aero engine

No matter in traditional hydraulic mechanical or newly numerical controlling system, pressure differential valve (PDV) always plays an important role in main fuel oil system and thrust augmentation fuel system. A throughout study on PDV is required to gain a more precise control and effective design for aero engine. Therefore, this paper presents a PDV and establishes the mathematical model to analyze its working characteristics, which shows that PDV performance is greatly affected by return oil inlet orifice and spring stiffness. The simulation and experiment are carried out to analyze the effect of PDV performance on system outlet volume flow rate and their results agree well with a maximum error of approximately 5 %. According to the study, it is found that there is a maximum increase of 9.99 % in system volume flow rate with pump rotating velocity from 300 to 900 rpm, but a maximum decrease of 3.4 % with outlet load pressure from 0.5 to 1.6 MPa. In addition, calculated curve slope reduces with return oil inlet orifice number increase and spring stiffness decrease, which means that PDV shows a faster response to working condition change and a better dynamic characteristic in controlling process. It is excepted that the research can be helpful in a further understanding of aero engine controlling system and a meaningful instruction on system optimization as well as fuel efficiency improvement.

Heat transfer and pressure drops during high heat flux flow boiling of low-GWP refrigerants in 200 μm-wide multi-microchannels

Thermal management of electronics is continuously challenged by increasing heat fluxes to be dissipated at minimum power consumption. This study investigated the pressure drops and the heat transfer coefficient of two low-GWP refrigerants, R1234yf and R1234ze(E), during flow boiling at high heat fluxes. The test geometry comprised 25 parallel microchannels, 200 μm wide, 1200 μm deep and 1 cm long, nominally. Inlet orifices were used to stabilize the flow. A parametric analysis involving the mass flux and heat flux was conducted for nominal saturation temperatures of 30.5C∘ and 40.5C∘, resulting in a maximum confinement number NConf of 2.16 for R1234yf and 2.52 for R1234ze(E). As the applied heat flux was increased from low to near-critical values, the two-phase heat transfer transitioned from a heat-flux-dominated mode to a convection-dominated one. The flow finally approached dryout, which led to the critical heat flux upon further heating. The experimental results were analysed through a regression with relevant non-dimensional groups, in particular the confinement number, NConf, the equivalent wall Biot number, Bi, the boiling number, Bo, the convection number, Co, and the Weber number, We. It was shown that Bo and Bi had a major influence in the heat-flux-dominated region, while Co and NConf determined the performance in the convective region, mainly due to the establishment of an intermittent annular flow. The total channel pressure drops were evaluated through the experimental measurement of the pressure drops in the inlet-outlet manifold, and the orifices. Due to the short channel length and the high heat fluxes, the pressure drops were dominated by the momentum change contribution, which accounted for at least 60% of the total pressure drops in the lowest case. The flow-wise heat transfer coefficients and the channel pressure drops were compared with the predictions of existing correlations, showing generally a fair agreement.

Experimental investigation of two-phase heat transfer in saw-tooth copper microchannels

Due to the confinement effect, vapor backflow is ubiquitous in flow boiling process in microscale confined domains. This, in turn, severely deteriorate the flow boiling performances. To solve this dilemma, many microchannel configurations have been exploited to regulate two-phase flows such as inlet orifices and auxiliary channels. However, the inlet orifices would lead to significant increase of flow resistance, scarifying the pumping power. In this study, periodic symmetric saw-tooth structure is designed and fabricated along sidewalls of parallel copper microchannels to effectively suppress the vapor backflow without the cost of pressure drop. The effects of this periodic symmetric saw-tooth structure on suppression of vapor backflow and two-phase flow mixing are studied in both forward and reverse directions. The flow boiling performances of this saw-tooth microchannel configuration was experimentally investigated for total inlet flow rates ranging from 30 to 70 ml/min (mass flux ranging from 183.3 kg/m2·s to 427.7 kg/m2·s). The experimental results and visualization study demonstrate that the successful suppression of vapor backflow in the forward direction and enhancement of two-phase flow mixing in the backward direction can dramatically enhance flow boiling performance. Significant boost on both HTC and CHF is demonstrated. A CHF of 217 W/cm2 is demonstrated at 70 ml/min in the forward direction. Also, significant difference in CHF is observed between the two flow directions as the further increase of flow rates. Compared to conventional plain wall microchannels, the CHF and HTC of this study can be significantly enhanced by ∼77.4 % and ∼250 %, respectively. Note that this improved boiling performance is achieved without sacrificing pressure drops.

Optimization of Vibrating Mesh Nebulizer Air Inlet Structure for Pulmonary Drug Delivery

The vibrating mesh nebulizer (VMN) has gained popularity for its compactness and noiselessness. This study investigates the impact of different air inlet structures on the deposition fraction (DF) of droplets generated by VMNs in an idealized mouth–throat (MT) airway model. Three homemade VMNs with semi-circular inlet, symmetrical four-inlet, and multiple-orifice inlet structures were evaluated through simulations and experiments. The changes in droplet DF of 0.9% w/v concentration of nebulized sodium chloride (NaCl) droplets as a function of inertial parameters were acquired under different inhalation flow conditions. Additionally, flow field distributions in models with different inlet structures were analyzed at a steady inspiratory flow rate of 15 L/min. The results indicate that optimizing the VMN’s air inlet structure significantly enhances droplet delivery efficiency. The multiple–orifice inlet structure outperformed the other designs, directing the airflow from the inlet position to the center of the mouthpiece and then into the oral cavity, achieving a DF of up to 20% at an inhalation flow rate of 15 L/min. The region of high airflow velocity between the mouthpiece and oral cavity proved to be a favorable VMN inlet optimization, reducing direct droplet–wall collisions and improving delivery efficiency. These findings offer insights for VMN design and optimization to enhance pulmonary drug delivery effectiveness and therapeutic outcomes.

Thermodynamic study on throttling process of Joule-Thomson cooler to improve helium liquefaction performance between 2 K and 4 K

The Joule-Thomson cooler (JTC) is a key component of the hybrid cryocooler dedicated to achieving and maintaining the operating temperature of around 2–4 K extensively used in quantum computing and communications. To clarify the energy conversion mechanism during the throttling process of the JTC and to improve throttling performance at 2–4 K, a numerical model is developed in which the effect of the complex real physical properties of liquid helium is considered, and the modified Lee phase change model is proposed to meet the operating conditions from supercritical to saturation. The results show that the phase change causes the cooling effect during the throttling process. The larger total energy loss in orifice leads to a higher liquefaction ratio. The liquefaction ratio increases with the increasing orifice thickness and the decreasing orifice diameter and inlet pressure. Given a constant inlet and refrigeration temperature difference, the liquefaction ratio increases with the increase of inlet temperatures. The maximum liquefaction ratio of 93.80% is achieved with orifice thickness of 0.8 mm, orifice diameter of 30 μm, and inlet pressure of 0.32 MPa, assuming an inlet temperature of 4 K and a refrigeration temperature of 3.43 K.

Injection-Coupling Instabilities in the BKD Combustor: Acoustic Analysis of the Isolated Injectors

Injection coupling is a well-known cause of high-frequency combustion instability in hydrogen/liquid oxygen () rocket engines. This type of instability is commonly explained by the two-way coupling between the dynamics of the combustion chamber and the injection system. Recent experimental studies of the BKD combustor, however, suggest that the LOX injector could be self-excited and driving the acoustic mode of the combustion chamber. To assess the feasibility of this mechanism, here, we study both experimentally and theoretically the acoustic stability of the LOX injector isolated from the combustion chamber. The experimental study was performed in a water facility mimicking the conditions of a single LOX injector. The water injector was then modeled using an acoustic network analysis, where the transfer matrix of the LOX injector inlet orifice was computed numerically using a linear approach. The analysis successfully predicts the experimental peak in unsteady pressure, revealing that the LOX injector can be self-excited. The instability was found to be driven by the whistling of the orifice at the inlet of the injector coupled with the second longitudinal acoustic mode of the LOX post tube.

Numerical analysis of a novel miniature Joule-Thomson cryocooler

In this paper, a novel miniature Joule-Thomson (J-T) cryocooler was proposed and its steady-state cooling characteristics were analyzed via CFD numerical simulation. The performance characteristics were assessed for nitrogen under different inlet pressure and temperature, as well as different orifice widths. The results have outlined the structural advantages of the cooler – its excellent cooling performance, small axial height and simple fabrication. Owing to the structural characteristics of the spiral channel and the centrifugal force and gas viscous force actions, the fluid formed vortexes and secondary flow on the axial shear plane. This improved the heat transfer between the incoming flow and backflow fluid. Therefore, the heat transfer increase will further reduce the cooler stable operating temperature, and the minimum temperature can reach 138.3 K when the inlet pressure is 10 MPa. Meanwhile, there is an optimal throttle orifice width δ value between 0.1 mm and 0.2 mm, the cryocooler can get maximum cooling capacity under minimum temperature. In addition, the inlet pressure increases with the decrease in the throttle orifice width and inlet temperature. The minimum cooler temperature is gradually reduced, extending the cooling duration time. On the other hand, should the minimum temperature and cooling duration time decrease, the mass flow rate will also increase.

Experimental and CFD Analysis on the Effect of Various Cold Orifice Diameters and Inlet Pressure of a Vortex Tube

An experimental investigation was conducted to investigate the effects of different cold orifice diameters and operating pressures of the vortex tube. A vortex tube test rig was employed to conduct the experiments for various cold orifice diameters and operating pressures. Cold orifice diameters range from 1 mm to 6 mm, whereas the pressure condition ranges from 2 to 5 bar. The vortex generators were made up of brass material having six inlet nozzles. It was found that the temperature separation of the vortex tube significantly depends on the cold orifice diameter of the vortex tube and operating pressure. The study demonstrates the deviation of cold temperature separation with respect to the cold orifice diameters and inlet pressure for different cold mass fractions. In addition, present experimental results are used to determine the optimum cold orifice diameter, which is 5 mm at 5 bar inlet pressure. The percentage improvement in average cold temperature separation for 5 mm cold orifice diameter is 66.18% compared to rest of the cold orifice diameters at an inlet pressure of 5 bar. The maximum cooling power separation is 0.08 kW at 0.3 cold mass fraction and inlet pressure of 5 bar. The CFD technique was approached to discuss the complex fluid flow inside the tube at various radial distances. A three-dimensional numerical study was done and validated with the present experimental work. It was found that the numerical results are in good agreement with the present experimental data.

High reliability model of mechanical response in drilling of CFRP/Al stacks

CFRP/Al laminate material is widely used in aerospace due to its advantages of light weight and high machinability. For assembling, crowded assembly holes need to be drilled for CFRP/Al laminate products. However, the damages of burr, delamination, and tearing appear frequently in drilling without precise guidance by mechanical response model. In order to reduce the machining damages, in this paper, a high-reliability mechanical response model is established for each stage in laminate materials drilling to ascertain the matching method between materials, tools, and cutting parameters. The theoretical expression of drilling thrust based on the thin plate theory is established considering the influence of cutting parameters, and further corrected with the cutting parameter correction terms to predict drilling thrust force, and further guiding the optimization of drilling parameters. According to the experimental results, the proposed model has a reliability greater than 97.3% and a prediction deviation lower than 13.2% in CFRP/Al laminate material drilling thrust force prediction. In the cutting with optimized parameters from the proposed model, the inlet orifice of the laminated material has no flanging burr, and the CFRP layer exit orifice has no defects as burr, delamination, or tearing.

A Gain Scheduling Design Method of the Aero-Engine Fuel Servo Constant Pressure Valve with High Accuracy and Fast Response Ability

Constant pressure valve, which has an axially symmetric structure, is an essential component to supply the servo reference pressure for aero-engine hydraulic mechanical control systems, and its performance directly impacts the performance of the control system. This paper constructs a closed-loop disturbance rejection system of the constant pressure valve based on the linear incremental description method, in which the controlled object is the controlled pressure, and the stabilization controller is constructed by the closed-loop feedback motion valve. Meanwhile, the linear models of the closed-loop system are calculated. Subsequently, based on the bode frequency domain characteristic analysis, the accurate influences of the stabilization control gain on the dynamic performance and stability of the system are given. On this basis, a gain scheduling design method of the system is proposed, and the geometry design and implementation method of the inlet orifice is proposed to complete the design work. The simulation results show that under bad conditions, which include the 1 MPa strong step disturbance of the inlet pressure and the step disturbance of the variable outlet flow area, the steady-state working range of the controlled pressure is 1.5 ± 0.01 MPa, the steady-state error is not more than 0.7%, and the regulation time is not more than 0.006 s.

Effect of asymmetrical orifice inlet geometry on spray kinematics and development

In diesel engines, fuel injection has a commanding effect on combustion. Thus studying diesel spray characteristics is beneficial for controlling and improving diesel combustion. However, information on diesel spray characteristics, especially those governed by injector needle lift, is lacking. This study investigates the near-nozzle spray kinematics for particular nozzle geometries over a range of injection pressures. The nozzles used in this research include a single-hole off-axis nozzle and a two-hole nozzle with deviated orifices. This study aims to observe the effect of asymmetrical orifice inlet on the spray kinematics and describe how sensitive they are to the injection pressure. First, we applied double-pulses time-gated ballistic imaging to obtain well-defined spray/gas interfaces. Then, by tracking these interface structures, we obtained spray kinematics. The results show that the two-hole nozzle generates slower sprays than the single-hole nozzle at the beginning of injection. However, the velocity differences between these sprays become less significant as the sprays develop to a quasi-steady state. In addition, the velocity diagrams show that the instabilities cause the flow to experience significant velocity alterations at the beginning of the injection. Moreover, we observed that the nominal spray axis shifts towards the sharper orifice inlet edge, which will affect the spray targeting. Finally, the injection pressure seems to have minimal effect on the spray profile, but it certainly changes spray evolution timing and shortens the transient phase.

Surgical Treatment of a Giant Popliteal Venous Aneurysm and Arteriovenous Fistula on the Adjacent Femoral Vein and Its Postoperative Findings.

A case of a giant popliteal venous aneurysm that caused massive pulmonary thromboembolism with an arteriovenous fistula draining into the adjacent proximal femoral vein is reported herein. Deep veins in the lower leg were occluded by thrombi. The inlet and outlet orifice inside the aneurysm was closed and aneurysmorraphy was performed. The fistula was retained on the estimation that it would maintain the blood flow and prevent thrombus formation inside the femoral vein. The aneurysm was shrunk, the femoral vein was patent, and the fistula was not observed 1 year later, although it still existed 1 week after the operation.

Investigation on intensified degradation of Rhodamine B and heat generation using a novel thermally assisted hydrodynamic cavitation device

In this study, a thermally assisted hydrodynamic cavitation (HC) system was established by adding a water pre-heater in front of the cavitation device (orifice plate), which realizes the local heating of the flowing liquid, intensifies the HC effect and enhances Rhodamine B (RhB) degradation ratio and heat generation efficiency. The effects of preheating temperature, RhB initial concentration, orifice hole number, inlet pressure and solution volume on RhB HC degradation and heat generation were investigated. Free radical trapping experiments were performed to explore the active substances produced by the HC effect. Based on LC-MS and TOC data, the possible RhB degradation pathway and mechanism were proposed. When the preheating temperature rose from 10 °C to 50 °C, the RhB degradation ratio increased from 23.42% to 34.49% within 90 min cycle time, and the treatment cost decreased from 130.699 USD/m3 to 91.701 USD/m3. At 30 min cycle time, the solution temperature rose from 45.6 °C to 56.4 °C, the heat production increased from 149.46 KJ/L to 194.81 KJ/L and the corresponding thermal efficiency increased from 47.45% to 61.84%. Further, at 60 min cycle time, under the conditions of 30 °C preheating temperature, 30 mg/L RhB initial concentration, 3-hole orifice plate, 3 bar inlet pressure and 5.0 L RhB solution volume, the RhB degradation ratio was the highest (40.38%). After Fenton reagent was used, the RhB degradation ratio and heat production both were further enhanced. At 60 min cycle time, the RhB degradation ratio was 65.52%, solution temperature rose to 72.8 °C, the heat production reached 131.83 KJ/L and the treatment cost was only 45.447 USD/m3 at 30 °C preheating temperature. TOC test results show that the RhB mineralization ratio can reach 61.53% after 90 min cycle. All in all, this work proves that thermally assisted HC is an effective method to degrade organic dyes and generate heat, which can be used for large-scale treatment of organic dye wastewater.

Thermal destratification of cryogenic liquid storage tanks by continuous bubbling of gases

This paper focuses on thermal destratification and pressurisation inside thermally stratified storage tanks by continuous gas bubbling. The primary purpose of doing these studies is to better understand the effect of bubble dynamics on thermal destratification and quantify the extent of destratification. The volume of fluid and interface compression method of OpenFOAM CFD code is utilised for the present analysis. Different values of inlet gas velocities (Vg), orifice diameters (do), and arrangement of the orifices in triangular and square fashion with different pitches (p/do) are considered. In addition, the effect of gravitational forces (g/ge) on thermal destratification is also reported. For all these cases, the effectiveness of thermal destratification is quantified in terms of a newly defined parameter, the destratification index (Id). For Vg = 1 m/s, the Id value is maximum compared to lower Vg values. It is seen that when the gas velocity increased from 0.3 m/s to 1.0 m/s, the average effectiveness in thermal destratification (Idavg) and pressure at the ullage increased by 44.38% and by 64.81%, respectively. The Idavg and pressure at ullage increased by 96.29% and 14.91%, respectively, when the g/ge ratio changed from 0.3 to 3. Compared to the triangular arrangement with p/do = 10, the calculated Idavg increased by 30.67% when gas inlets were arranged with a square pitch of 10. For p/do = 4, 6 and 8, the increments in Idavg are of the order of 12.86%, 19.43% and 21.92%, respectively, for gas inlets arranged in a square fashion as compared to the triangular arrangement. It is found that continuous bubbling with gas inlets arranged in square pitch p/do = 10 gives higher effectiveness in thermal destratification. Thus, by these studies, one can develop a thermal destratification mechanism with continuous bubbling for optimum performance. Also, these studies give an overall idea of sparger design for getting the correct gas flow rate for thermal destratification within the cryogenic liquid storage tanks.

DES analysis on effects of variable geometry inlet orifice on a centrifugal compressor

A variable geometry inlet configuration can improve the off-design aerodynamic performance of a turbocharger compressor by actively modulating the internal flow field. As the core part of the configuration, the variable geometry orifice is arranged in front of the compressor inducer. Its novelty is to actively regulate the compressor inlet flow area at an off-design point without causing significant impact at the design point. In this paper, the effects of the orifice on compressor performance and internal flow field are investigated using experiments and numerical simulations. The experimental and the numerical results confirm the variable inlet configuration to be a promising method for extending the compressor operation range. The DES calculations reveal incidence angle reduction at inducer inlet, shock wave migration to a lower radius from blade tip, formation of the aft-loaded impeller, reduced difference between jet and wake flows at impeller exit, and turbulent flow enhancement in the diffuser. Based on understanding the orifice’s effects on the centrifugal compressor, a design suggestion is proposed for the variable geometry compressor of this sort.

Study on the factors influencing air valve protection against water hammer with column separation and rejoinder

Abstract Air valves are used to suppress negative water pressures in water transmission pipelines. They also play a key role during the water filling and drainage stages in pipeline systems. However, systematic guidelines for the selection of air valve parameters are lacking. In practical engineering applications, the selection is mainly based on personal experience. If the selected parameters are not appropriate, negative pressures can occur in a pipeline due to insufficient air inflow or destructive water hammer pressures with column separation and rejoinder, which are caused by rapid air discharge. Given the subjectivity of the selection of air valve parameters in engineering applications, this paper introduces the structure and working principle of two different types of air valves. Combined with engineering examples, the one-dimensional transient flow elastic model and the characteristic method are used to conduct numerical simulations in MATLAB to investigate the influences of the air valve type, the inlet and outlet orifice diameters, and the inflow and outflow discharge coefficients on protection against water hammer with column separation and rejoinder. The inflow and outflow coefficients of the anti-slam air valve have a slight influence on preventing water hammers with column separation and rejoinder. The research results provide a theoretical basis for the rational selection of air valves in practical engineering applications.

Study of the Influencing Factors on the Small-Quantity Fuel Injection of Piezoelectric Injector.

The piezoelectric injection-system provides a reliable approach for precise small-quantity fuel injection due to its fast, dynamic response. Considering the nonlinearity of a piezoelectric actuator, the complete electro-mechanical-hydraulic model of the piezoelectric injector was established and verified experimentally, which showed that it could accurately predict the fuel injection quantity. The small-quantity fuel injection with different driving voltages, pulse widths, and rail pressures was analyzed. The effects of key structural parameters of the injector on the delivery, control-chamber pressure fluctuation, and small-quantity injection characteristics were studied. The results show that the linearity of the curve of the injection volume with the pulse width was relatively poor, and there was a significant inflection point when the piezoelectric injector worked in the small pulse width region (PW < 0.6 ms). The bypass valve significantly accelerated the establishment of the control-chamber pressure, reduced the pressure fluctuation in the chamber, shortened the closing delay and duration of the needle valve, and reduced the rate of the fuel-quantity change so that it provided a greater control margin for the pulse width over the same fuel volume change interval. Under the condition of a small-quantity fuel injection of 20 mm3, decreasing the inlet orifice diameter and increasing the outlet orifice diameter shortened the minimum control pulse width and fuel injection duration required for the injector injection, which is beneficial for multiple and small-quantity fuel injection. However, these behaviors reduce the control margin for the pulse width, especially in small pulse width regions.

Structural basis for long-chain isoprenoid synthesis by cis-prenyltransferases.

Isoprenoids are synthesized by the prenyltransferase superfamily, which is subdivided according to the product stereoisomerism and length. In short- and medium-chain isoprenoids, product length correlates with active site volume. However, enzymes synthesizing long-chain products and rubber synthases fail to conform to this paradigm, because of an unexpectedly small active site. Here, we focused on the human cis-prenyltransferase complex (hcis-PT), residing at the endoplasmic reticulum membrane and playing a crucial role in protein glycosylation. Crystallographic investigation of hcis-PT along the reaction cycle revealed an outlet for the elongating product. Hydrogen-deuterium exchange mass spectrometry analysis showed that the hydrophobic active site core is flanked by dynamic regions consistent with separate inlet and outlet orifices. Last, using a fluorescence substrate analog, we show that product elongation and membrane association are closely correlated. Together, our results support direct membrane insertion of the elongating isoprenoid during catalysis, uncoupling active site volume from product length.