Increase Of Inlet Pressure Research Articles

Numerical simulation of condensation of supercritical water gasification products in a supersonic nozzle

The clean and efficient separation of supercritical water gasification products (SCWGP) has emerged as a significant challenge in supercritical water gasification technology. This paper proposes the use of a supersonic nozzle for the condensation and separation of H2 and CO2 from SCWGP, leveraging the high-pressure characteristics of these products. By establishing a flow model and a condensation model for the supersonic nozzle, the effects of inlet pressure and inlet temperature on the condensation process are analyzed. The analysis reveals that the latent heat released during condensation causes an abnormal distribution of pressure and temperature within the nozzle. When the inlet pressure of the nozzle is increased from 7.0 to 9.0 MPa, the liquid phase mass fraction at the outlet rises from 5.3 × 10−3 to 0.056. Similarly, when the inlet temperature is lowered from 300.0 to 290.0 K, the liquid phase mass fraction at the outlet also rises from 5.3 × 10−3 to 0.058. The increase in inlet pressure leads to the condensation location shifting toward the throat by ∼8.5 × 10−3 m⋅MPa−1, while the impact of inlet temperature is approximately −2.3 × 10−3 m⋅K−1. The nucleation rate in the nozzle is always concentrated in a small region.

Self-excited oscillation characteristics and mechanisms of supercritical CO2 flowing in a Helmholtz oscillator for enhancing heat transfer

The drastic variations in thermal properties of supercritical CO2 near its pseudo-critical point induce the formation of complex boundary layer structures within pipelines, rendering it susceptible to heat transfer deterioration under the influence of buoyancy forces. The Helmholtz self-excited cavity can generate self-excited pulsating jets, enhancing the intermixing between fluids inside the heat exchanger tubes, disrupting the thermal boundary layer, and suppressing heat transfer deterioration. In this study, the characteristics and mechanisms of self-excited oscillations of supercritical CO2 flowing vertically upward in the Helmholtz self-excited cavity were investigated using the large eddy simulation (LES) method. A detailed analysis of cavitation and vortex evolution within the cavity was conducted, along with an exploration of the influence of inlet pressure and structural parameters on the frequency characteristics of pulsations. The results indicate a close relationship between cavitation and vortex interactions and the pulsation frequency. An increase in inlet pressure leads to a significant cavitation phenomenon near the jet shear layer and an increase in vortex frequency. Dimensionless cavity length (Lc/d1) enlargement results in an increase in outlet pulsation frequency but a decrease in pulsation amplitude. The critical dimensionless ratio of cavity diameter (Dc/d1) plays a crucial role in maintaining the desired pulsation frequency and amplitude. Within the working range outlined in this paper, practical insights for system design and operation are provided by the optimal parameters of Lc/d1 = 3 and Dc/d1 = 10.

Evolution law of flow characteristics for straight pipeline after leaking

Aiming at the leakage problem of the fluid loop system for the thermal control system of spacecraft caused by the impact of micro-meteoroid and orbital debris, we investigate the dependence of the leak rate, pressure drop and flow characteristics before and after leaking on leak position, inlet pressure, and leaking aperture, calculated in a straight pipeline with single leakage, using stationary and transient three-dimensional computational fluid dynamics simulations with commercial software (FLUENT). The working fluid adopts single-phase water without gravity. It is found that the pressure increases obviously near the leak point, which is caused by the local peak of pressure. As the length between the leak point and the inlet becomes larger, the local peak of pressure and the dimensionless leak rate are smaller. When the inlet pressure increases, the leaked mass flow rate increases; however, the ratio of the leaked flow rate to inlet flow rate decreases. Furthermore, it is observed that the dependence of dimensionless leaking rate on dimensionless leaking aperture has a scaling relation with the scaling exponent approximating to 2, which may be related to the proportion of the vortex formed by the backward flow at the leak hole, the amplitude, and the affected length along the pipe of the local peak of pressure. This study is instructive and meaningful to the leak detection and plugging of fluid loop in space.

Wetting Dynamics Behavior of In Situ Generated Droplet on Micropore Surfaces

The pinning dynamic of oil droplet on micropore surface has a significant impact on the stability of the oil film. Herein, the numerical model of the oil droplet generated in situ at the orifices is established. The influence of pore parameters and the inlet pressure on the movement of the three‐phase contact line are explored. The transformation mechanism between pinning and spreading of the droplet is revealed. The result shows that due to the competition between the surface tension and the driving force, the flow field parameters at the pinning point become unstable. Until the three‐phase contact line is unpinned, the droplet spreads on the micropore surface. With the reduce of the contact angle or the increase of the diameter of the pore, the pinning time of the droplet is shortened, and the droplets spread faster on the micropore surface. As the inlet pressure increases, the droplets grow faster at the orifice and spread from the orifice until the apparent contact angle reaches its maximum forward angle. The spread promotes the regeneration of the lubricating film, which is conducive to improving the stability of the oil film on micropore surface.

Experimental Study on the Performance and Internal Flow Characteristics of Liquid–Gas Jet Pump with Square Nozzle

In order to ascertain the impact of working water flow rate and inlet pressure on the performance of the liquid–gas jet pump with square nozzle, the pumping volume ratio and efficiency of the liquid–gas jet pump with square nozzle were experimentally investigated at different inlet pressures and working water flow rates. Furthermore, the internal flow characteristics of the liquid–gas jet pump with square nozzle were explored through the utilization of visualization technology in the self-designed square-nozzle liquid–gas jet pump experimental setup. The findings indicate that the pumping ratio of the liquid–gas jet pump increases in conjunction with an elevation in the inlet pressure. Liquid–gas jet pump efficiency is higher at lower inlet pressures, up to 42.48%, and drops rapidly as inlet pressure increases. The pumping volume ratio of the liquid–gas jet pump increases significantly as the working water flow rate increases, and the working water flow rate exerts a minimal effect on the working efficiency of the liquid–gas jet pump. In the context of extreme vacuum conditions, a considerable number of droplets undergo substantial reflux in the posterior section of the throat, with a notable absence of bubbles in the diffusion tube. The size and number of bubbles diminish gradually along the axial direction. The objective of this paper is to provide a reference point for determining the optimal operational parameters for a square-nozzle liquid–gas jet pump in a practical context.

Hydrogen energy storage system integrated with the surplus energy from Hydropower plant in the context of Nepal: A parametric study

Abstract With the search for emission-free energy sources, hydrogen is considered a reliable alternative to store energy from renewable sources like wind, solar, thermal, and hydropower. Hydrogen has minimal environmental implications and can be stored and transported whenever there is an energy demand that other intermittent sources cannot suffice. This project aims to study the integration of hydropower with a hydrogen production and storage plant in Nepal to utilize excess energy supply that will exceed the country’s demand shortly. The excess power from the hydropower will be used to produce hydrogen from the water coming out from the tailrace. This water will also be a coolant for cooling the hydrogen before passing to the storage unit. This parametric analysis shows the effect of variation in the hydrogen inlet pressure before it enters the compressor unit and the impact of variation in storage tank pressure on the energy and exergy efficiency of the overall hydrogen production and storage system. In the first case, the inlet pressure varies from 0 to 20 MPa at three different constant storage pressures 40 MPa, 60 MPa, and 90 MPa. An increase in inlet pressure gradually increases energy and exergy efficiencies, but an increase in storage pressure lowers this efficiency. The reduction is more significant at a high value of inlet pressure. In the second case, the storage pressure varies between 20-80 MPa with constant inlet pressure at 0.1 MPa, 1 MPa, and 5 MPa. The increase in storage pressure gradually reduces efficiency, whereas the higher inlet pressure has higher efficiency. Hydrogen fills the gap between supply and demand of energy, so considering hydrogen production with multiple-stage compression and integration of three sources of energy: wind, solar, and hydropower has an excellent prospect for consistent and low carbon emission solutions.

Effect of Inlet Pressure on the Polyurethane Spray Nozzle for Soil Cracking Improvement: Simulations using CFD Method

Rigid spray polyurethane (RSPU) was commercially used as an injection in crack walls or soil surfaces to enhance material performance, increase lifetime, and save operating costs. The limitation of the RSPU nozzle was reported as easily clogging when sprayed out to the insulation and crack surface area and the finished product was less aesthetically pleasing. In this study, the RSPU nozzle of flat fan nozzle, 180° angle (Design A), Hollow cone nozzle, 60° angle (Design B), and Full cone nozzle, 90° angle (Design C) were prepared by using the SOLIDWORKS software. The effect of different pressures for RSPU nozzle design at the ranges of 4Mpa, 5MPa, and 6MPa was examined by ANSYS FLUENT software. The velocity of the outer spray nozzle shows a significant increase with increasing inlet pressure of the RSPU nozzle. The results reveal that the highest velocity of RSPU was obtained at the Hollow cone nozzle (Design B) as compared to (Flat fan nozzle) Design A and (Full cone nozzle) Design C at 394.249 m/s at 4MPa, 442.327 m/s at 5MPa and 485.37 m/s at 6MPa, respectively. The distribution droplet area shows the Design B spray formation had wider area coverage at 60° and exhibited that the injection nozzle spray was scatted and uniform at 6MPa. RSPU shows the velocity increased, distribution droplet increased, and output volume spray was decreased at the increasing of injection pressure. Hence, in this study was suggested that the size of RSPU nozzle design must be made at the ranges of 60° to 90° of outlet nozzle to obtain a good RSPU area. In conclusion, design B is the most effective for RSPU nozzle and is useful in injection cracking and insulation materials applications.

A new empirical mass flow correlation and mass flow rate characteristics of R600a through novel rotary-baffle curved-channel electronic expansion valve

The novel rotary-baffle curved-channel electronic expansion valve (RBCC-EEV) has appeared in industry to replace a capillary tube as the variable expansion device in household refrigerators. However, due to the structure differences between the RBCC-EEV and the traditional orifice-type EEV, the previous empirical mass flow correlation inapplicable. In this paper, a new empirical correlation is proposed based on the structure and regulation principle of the novel RBCC-EEV, and the effects of different operating conditions on the mass flow rate of R600a flowing through two different RBCC-EEVs are experimentally investigated. The new empirical correlation introduces a centrifugal force coefficient and a variable length coefficient to represent the effect of asymmetric cavitation phenomenon and super-linear mass flow rate characteristics. The experimental results show a rise in the mass flow rate with increasing inlet pressure, inlet subcooling and opening ratio. Under the test range, the flow pattern of R600a flowing through the RBCC-EEV is chocked flow. Moreover, the proposed new empirical mass flow correlation agrees well with the experimental data. For 95.7 % of the prediction value, the relative deviation is below 15 %, while 89.0 % exhibit a relative deviation less than 10 %. The average deviation and standard deviation stand at 6.52 % and 4.56 %, respectively.

An event-triggered background-oriented schlieren technique combined with dynamic projection using dynamic mirror device

Abstract This paper reports a high-frequency event-triggered background-oriented schlieren (BOS) technique using a combination of an event-triggered camera and dynamic projection. To combine the advantages of continuous and pulsed illumination for the event-triggered camera, a novel background pattern is first developed to incorporate static and dynamic textures generated through projection utilizing a dynamic mirror device (DMD). Then, a specific post-processing algorithm is proposed to reconstruct frames with high time accuracy from event data. This technique allows for the continuous observation and capturing of flows at 4000 frames per second (FPS) with a very low cost, breaking through the short operating times of current high-frame-rate BOS. Moreover, the proposed BOS technique can visualize the flow in real-time with high temporal accuracy, a capability that is challenging to achieve with traditional BOS. To examine the proposed technique, BOS experiments were conducted on a sweeping jet actuator with various inlet pressure. The sweeping dynamics and the start-up process of the sweeping jet at various inlet pressure were visualized and investigated. It is found that the proposed event-triggered BOS can continuously visualize and record the jet flow at a resolution of 1280 × 720 pixels with an equivalent frame rate of up to 4000 FPS. The oscillation frequency of the sweeping jet was found to increase linearly with increasing inlet pressure. It reaches 117.2 Hz at an inlet pressure of 0.5 Mpa. Within the first ten milliseconds or so of start-up, the shape of the sweep was found to be symmetrical. Within the next hundred milliseconds, the jet commences to sweep and saturates. The start-up time of the sweeping jet was quantitatively measured and was observed to decrease with increased inlet pressures.

Design and optimization of the radial inflow turbogenerator for organic Rankine cycle system based on the Genetic Algorithm

The backdrop of energy-saving and emission-reduction sets a higher demand for low-grade energy utilization which can be realized by Organic Rankine Cycle systems. A 50-kW radial inflow turbogenerator, the crucial heat conversion equipment, with aerostatic bearings for Organic Rankine Cycle system, is designed. It is optimized focusing on the performance of the turbogenerator which uses R245fa as the working fluid. The study employs a one-dimensional thermodynamic model, developed in MATLAB and bolstered by real-time data from Refprop, ensuring the model’s precision and dependability. On this basis, Genetic Algorithm is applied to optimize design parameters and significantly elevate the system’s efficiency, achieving circumferential efficiency of 85.29%. The turbogenerator demonstrates a rated bearing load capacity of 2.43 kN. The research delves into the influence of inlet temperature, inlet pressure, and rotational speed of turbogenerator on its performance. It reveals that an increase in both inlet temperature and inlet pressure lead to a decrease in isentropic efficiency and an increase in output power. The research also shows that an increase in the rotational speed contributes to increases in isentropic efficiency and output power.

Numerical investigation of jet impingement on flat/concave cooling of CO2 with different phase states under high heat flux

The thermal load and high temperature brought by the increase in power of electronic devices or the increase in speed of supersonic aircraft limit the respective development. In this paper, a numerical model of CO2 jet impingement cooling of a constant heat flux plate/concave surface in different phase states was established. Secondly, the non-equilibrium phase transition and the real-thermophysical properties of CO2 was considered. The effects of different wall heat flux (0.7 MW/m2 ∼ 6.5 MW/m2) and initial phase states on the impact cooling performance of CO2 jet were studied.It is found that for SCO2 jet impingement, when the inlet temperature is lower than the pseudo-critical temperature, the heat transfer coefficient increases with the increase of inlet pressure, and the maximum increase is 24.7 %. For near-critical liquid CO2 (LCO2) jet impingement, low latent heat prevents temperature overshoot in the heat flux range studied. With the increase of the proportion of dry ice in the inlet, the heat transfer coefficient also increases. When q > 3 MW/m2, the heat transfer coefficient of dry ice jet impact is 2.5 ∼ 3 times and 1 ∼ 1.4 times of that of SCO2 and near-critical LCO2 jet impingement for the flat plate model, respectively. For concave surface with high heat flux, near-critical LCO2 jet impingement cooling effect is relatively good. In addition, concave surface will aggravate the uneven cooling surface temperature.The results can provide more references for the CO2 jet impingement technology in the design of stagnation cooling system of supersonic aircraft and thermal management of high-power electronic devices.

Thermodynamic analysis of power generation thermal management system for heat and cold exergy utilization from liquid hydrogen-fueled turbojet engine

Hydrogen propulsion is generally treated as the ultimate net zero-emission option for aviation, therein liquid hydrogen storage appears to provide the only feasible solution for aircraft with the constraints imposed by aircraft weight and volume. Hydrogen liquefaction consumes a great amount of energy, which significantly boosts the cost of hydrogen as an aviation fuel. Besides the H2 chemical exergy for combustion to provide thrust, the H2 physical exergy in the form of cold energy is also a kind of high-quality clean energy to produce power output, which offers great opportunities to achieve cost-effective use of hydrogen fuel. Thus, this paper presents a Rankine cycle and H2 direct expansion cycle (RC-DEC) combined power generation thermal management system for the simultaneous utilization of exhaust gas heat exergy and hydrogen fuel cold exergy from the liquid hydrogen-fueled turbojet engine. In the Rankine cycle, the transcritical mode is applied on the hot side while the liquid separation condensation concept is adopted on the cold side to achieve better thermal matchings with heat and cold sources. The hydrocarbon/inert gas binary mixture is proposed as the working fluid of the Rankine cycle. The effects of key thermodynamic parameters and the influence of Para-Ortho hydrogen conversion on system performance are discussed, then a comparison of the mixture working fluid is conducted. Results show that there exists an optimal separation temperature ratio and condensation pressure of RC to obtain maximum total net power output. As the DEC expander inlet pressure increases, the total net power output first increases and then levels off. The introduction of the Para-Ortho hydrogen conversion has a negligible impact on net power output but leads to a significant reduction in the exergy efficiency, which is attributed to the cold energy release nature of Para-Ortho hydrogen conversion. The results of the working fluid comparison indicate that the optimal inert gas retardant for CH4 is Kr, while those for C2H6 and C3H8 are Xe to achieve the maximum net power output and exergy efficiency of the proposed power generation system. Among them, C2H6/Xe(0.6/0.4) obtains the maximum net power output of 2717.9 kW and maximum exergy efficiency of 33.1%, which suggests an opportunity to provide megawatts of electrical power for the aircraft in place of the APU.

Numerical simulation of condensation flows of humid air in the high-pressure pneumatic pressure-reducing valve

The phenomenon of condensation and ice formation exists in the high-pressure air pressure-reducing valve (HPAPRV), severely impacting the pressure-reducing valve's aerodynamic performance and operational safety. The problem is that the phase change of humid air in a high-pressure supersonic flow is not fully understood. This study aims to elucidate the condensation effect in high-pressure supersonic flows and the influence of the inlet conditions on the behavior of the condensate flow. A computational humid air phase model has been developed to investigate the formation of massive droplets due to phase-change processes. The numerical approach is validated by comparing it with experimental data, demonstrating a strong correlation between the two. The condensation properties of humid air in HPAPRV are described in detail. The effects of the condensation properties of humid air at different inlet conditions are discussed in detail. The results show that an increase in the inlet pressure increases the level of supersaturation, which increases the nucleation rate and the droplet growth rate and promotes droplet production. Increasing the inlet temperature has little effect on the HPAPRV pressure-reducing performance and predicts the temperature range of water vapor condensation before and after the valve port. The liquid mass fraction can be reduced by 50.9% by increasing the inlet temperature by 30 K, from 283 K to 313 K. When the inlet temperature is below 283 K, water vapor condenses in front of the valve port. Decreasing the inlet humidity reduces the degree and extent of supersaturation, which decreases the nucleation rate and the liquid mass fraction. When low inlet humidity (under 10%), the condensation phenomenon did not almost occur inside the pressure-reducing valve.

Experimental study on removal of hydrogen sulfide gas by spray and bubble blowing: A comparative study

H2S (hydrogen sulfide) is widely concerned because of its strong odor and toxicity, which seriously affects the physical and mental health of surrounding residents. In this paper, bubble blowing and spray deodorization experimental systems for H2S gas generation were constructed, with plant-derived deodorant were employed as a deodorizing liquid. The influence factors of spray and bubble blowing deodorization experimental system for deodorization performance were explored. And the effects of spray deodorization method and bubble blowing deodorization method on H2S removal rate were compared. The results show a positive correlation between the removal rate of H2S and the inlet pressure in the spray deodorization system. As the inlet pressure increases, the removal efficiency of H2S exhibits a gain ranging from 22.36% to 23.56%. Within the bubble blowing deodorization system, H2S concentration decreases as the deodorization solution dosage increases. As the deodorizing solution dosage increases from 920 mL to 1800 mL, H2S concentration decreases from 0.46 mg·m−3 to 0 mg·m−3. Furthermore, the bubble blowing deodorization method outperforms the spray, resulting in a 14.60–29.09% increase in H2S removal rate. The bubble blowing deodorization method proposed in this study exhibits promising potential for application in the field of malodorous gas treatment.

Design and analysis of centrifugal compressor in carbon dioxide heat pump system

Based on the advantages of energy saving, environmental protection and high efficiency, carbon dioxide heat pump system has great application prospects. However, there are still many technical problems to be solved, especially the design and optimization of carbon dioxide centrifugal compressor. In this paper, a centrifugal compressor in carbon dioxide heat pump system is designed. The compressor is directly driven by a high-speed permanent magnet synchronous motor. Two-stage impellers are installed on both sides of the motor, and the bearings are active magnetic bearings. The influences of inlet pressure and temperature on compressor performance are analyzed. In the range of inlet temperature from 35 to 55 °C, with the decrease of inlet temperature, the compressor pressure ratio increases by 12–29.8%, the power increases by 2.7–8.6%. In the range of inlet pressure from 4 to 6 MPa, with the increase of inlet pressure, the compressor pressure ratio increases by 12.3–38.6%, and the power increases by 8.7–17.8%. In addition, the calculation method of compressor axial force is introduced, the axial force is calculated, analyzed and optimized. Furthermore, the rotor dynamics of compressor rotor and the influences of bearing stiffness and diameter of motor rotor on rotor dynamics are studied. With the increase of bearing stiffness, the first-order critical speed and maximum displacement of the rotor increase. The research provides a theoretical reference for the design and optimization of centrifugal compressor in carbon dioxide heat pump system.

Energy, economic, and environmental analysis: A study of operational strategies for combined heat and power system based on PEM fuel cell in the East China region

This study introduces a combined heat and power (CHP) system primarily based on proton exchange membrane (PEM) fuel cells, which can provide electricity and heat for residential buildings in the East China region under two operating strategies. The analysis and discussion focus on the impact of parameters such as current density and gas inlet pressure on the system's output power and efficiency. The results indicate that excessively high current density decreases the system's electricity generation efficiency, while a moderate increase in hydrogen inlet pressure contributes to greater heat generation. Considering energy, economic, and environmental factors, the system operates with the thermal-led strategy in parallel with the grid, resulting in a substantial 73.3 % reduction in fuel costs. The annual greenhouse gas (GHG) emissions and the amount of emission reduction are lowered to 6.96 × 107 g and 3.39 × 107 g, respectively.

Effect of gas crossover on the cold start process of proton exchange membrane fuel cells

This study develops a transient three-dimensional model to investigate the effect of reactant gas crossover through the membrane on the cold start process of PEM fuel cells. Key operating and structure parameters such as current density, anode/cathode inlet pressure, and membrane thickness are explored. The results reveal that gas crossover enhances ice formation rate and cell temperature rise due to additional hydrogen–oxygen side reactions, increasing both heat and water generations. The dominance of the ice formation rate over the temperature rise rate by gas crossover adds complexity to successful cold starts. Notably, the influence of gas crossover is more pronounced at a lower current density. As the operating current density increases from 0.04 A cm−2 to 0.12 A cm−2, the contribution of gas crossover to the temperature rise rate and ice formation rate decrease from 31.6 % to 11.3 % and from 54.5 % to 16.8 %, respectively. The increase of anode inlet pressure accelerates ice formation and temperature rise, whereas cathode inlet pressure has minimal effect. A thicker membrane mitigates gas crossover and is beneficial to cold start success, especially under a wet initial condition. This study emphasizes the significant role of gas crossover in the PEM fuel cell cold start process, highlighting the imperative consideration of gas crossover in both cold start models and strategy developments.

Experimental analysis of a tri-partite brazed plate gas cooler for CO2 heat pump water heaters

Gas cooler is a crucial component in CO2 systems, and its performance significantly influences the overall efficiency of the CO2-based heat pump system. Brazed plate heat exchangers feature a compact design, reduced refrigerant charge, enhanced heat transfer coefficient, and lower pressure drop, resulting in space savings and improved system performance. This experimental study investigates a water-cooled tri-partite brazed plate gas cooler in a CO2 heat pump. The tri-partite brazed plate gas cooler has a double effect: it allows matching the temperature glide of CO2 with that of water and meeting the requirements for both domestic hot water and space heating simultaneously. The experiments are conducted in only domestic hot water and combined space and domestic hot water operative modes. The effects of different operating parameters on heat duty, supply temperature, temperature approach, and pinch point location are evaluated. The actual conductance of gas coolers is calculated, and a new definition is adopted to determine the ϵ−NTU of gas coolers. Results show that preheating gas cooler (GC3) has a higher heat duty at pressures near the critical pressure. As the inlet pressure increases, the domestic hot water supply temperature increases, the pinch point moves to the cold end of GC3, and the temperature approach decreases. The LMTD method may result in an undersized or oversized CO2 gas cooler by up to ±50% for different pressures. The errors reach their maximum values when the temperature difference is low at the cold end and high at the hot end. The effectiveness ranges from 0.56 to 0.94 and the NTU ranges from 2.64 to 5.41. The gas cooler shows promising performance. The outcomes of this research are anticipated to serve as a valuable reference for enhancing the design and optimization of transcritical CO2 systems.

Dynamic characteristics analysis and valve core optimization for second stage hydrogen pressure reducer of hydrogen decompression valve

As an important component of pressure management system, hydrogen decompression valve (HDV) is used in hydrogen fuel cell vehicles, hydrogen refueling stations, etc. The high-pressure difference causes severe pressure fluctuation. Thus, the HDV is composed of multi-stage pressure reducers. Specially, the outlet pressure from the HDV highly affects the pressure of fuel cell. The service life and operation condition of fuel cell is affected significantly by the HDV. This paper conducted the research of the second stage hydrogen pressure reducer (SHPR) of on-boarding hydrogen decompression valve. The force and dynamic characteristics of the valve core are obtained and the flow characteristic is analyzed through the steady and transient flow model. The results are shown that the fluid force and combined force on the valve core exhibit linear increase with inlet pressure and throttling area. The flow characteristics in the throttling gap exhibit similar distribution law under different throttling lengths and inlet pressures. The pressure-drop at entrance and exit of the throttling gap is drastic. Besides, the spring stiffness has a significant impact on the dynamic characteristics of the valve core. With the increase of spring stiffness, the dynamic characteristics change from unstable-state to stable-state under the sudden increase of inlet pressure. The larger spring stiffness initially causes displacement fluctuation of the valve core and then the valve core maintains a stable opening under the stable state. Finally, the optimized structure of valve core is proposed and the better stability of SHPR has been achieved. Meanwhile, there is no significant difference in flow performance but the dynamic characteristics are improved.

Application of a Ranque–Hilsch Vortex Flow in an Internal Cooling of a Gas Turbine Engine Blade

Abstract The efficiency of a gas turbine engine is directly impacted by the turbine inlet temperature and the corresponding pressure ratio. A major strategy, aside from the use of costly high-temperature blade materials, is increasing the turbine inlet temperature by internally cooling the blades using pressurized air from the engine compressor. Understanding the fluid mechanics and heat transfer of internal blade cooling is, therefore, of paramount importance for increasing the temperature threshold, hence increasing engine efficiency. This article presents modeling and test results of a novel cooling approach, one in which the Ranque–Hilsch vortex flow is adopted for the first-row gas turbine blade cooling. Simulation and test results demonstrate the successful formation of continuous Ranque–Hilsch vortex flow by injecting compressed air into a cylindrical chamber equipped with seven air inlets. At an inlet pressure of 100 kPa, the outlet temperature from the vortex tube dropped 255 °C, which allowed the blade temperature to cool by 47 °C. When a total inlet pressure of 300 kPa was admitted, the drop-in temperature reached 65 °C. The device has the potential to drop the cooling air temperature below the freezing point with increased inlet pressure. The thermal efficiency of the gas turbine blade increased by about 3% when vortex cooling with 10% mass of partially compressed air was extracted at about 910 kPa. For the tested scenario of a 17 MW power output, the partial extraction had a better efficiency increment than extraction at full compression, which was 1200 kPa.