Liquid Impingement Research Articles

Effects of radial fin arrangements on the thermal performance of turbulent liquid jet impingement heat sinks: Experimental and numerical approach

The combination of fins and jet impingement is a highly effective method for enhancing thermal performance in electronic cooling. The arrangement of fins significantly influences the thermohydraulic characteristics of heat sinks. A comprehensive analysis comparing the impact of different radial fin arrangements in confined jet impingement is crucial for a deeper insight into their thermohydraulic performance. This study presents experimental analyses of heat sinks with smooth surfaces and radial straight fins in the Reynolds number ranged from 4300 to 15,500 and the heat flux ranged from 45 to 105 W/cm2. Then a numerical study is conducted on the radial straight and curved fin arrangement to investigate the effects of different radial fin arrangements on the performance of jet impingement heat sinks. The results demonstrate that the use of fins improves heat sink performance by up to 27 % compared to smooth surfaces. The numerical model, employing the SST k-ω turbulent model, shows strong agreement with experimental findings, with a maximum deviation of 9.1 % for the heat transfer coefficient, well within the uncertainty range. Comparing radial straight and curved fin arrangements numerically, the straight fin arrangement exhibits superior thermal performance by up to 9 %. Additionally, the pressure drop for both configurations remains nearly identical. The findings of this research suggest the use of radial straight fin arrangements in annular jet impingement heat sinks over radial curved fin arrangements.

Unveiling the underlying physics of two-phase boiling heat transfer enhancement through shearing of coalescing bubbles

The upcoming energy scarcity problem has driven research toward developing energy-efficient two-phase heat exchangers essential for various cooling applications. This research is rooted in the principles of pool boiling, essential for effective heat transfer in various heat exchangers. A well-known reported problem in heat exchangers is the dry-out phenomena of heated surfaces due to bubble coalescence. To tackle this undesirable problem, an innovative technique has been introduced in this study, which involves the shearing of bubbles through liquid jet impingement over the heated surface. The study has been carried out in a two-dimensional domain numerically, in the wall superheat range of 9–16 K. To study the underlying physics involved in this pool boiling phenomenon, the bubble dynamics parameters such as departure frequency, bubble diameter, cold spot (bubble base) temperature, and vapor volume fraction have been analyzed. The results show that with the jet shearing effect, a maximum enhancement of 25% in heat transfer rate is observed at higher wall superheat. The investigation also highlights that the liquid jet enhances vapor volume fraction, indicating enhanced steam generation, particularly an enhancement of 27% observed at elevated wall superheat. An early onset necking effect is also observed with the shearing effect, which leads to the formation of smaller bubbles with higher departure frequencies. This study is a benchmark to the fundamental physics of enhancing two-phase heat transfer through bubble shearing, offering promising insights for energy conservation in two-phase heat exchanger design, particularly within the context of pool boiling.

Review on spray characteristics of liquid–liquid injectors in liquid rocket engines

Impinging-jet injectors, liquid–liquid coaxial swirl injectors, and liquid–liquid pintle injectors are representative liquid–liquid injectors in liquid rocket engines (LRE). For these liquid–liquid injectors, the atomization processes all involve the liquid impingement, including jet–jet, sheet–sheet, and jets/sheet–sheet impingement, respectively. After impingement, a liquid sheet forms and fragments. Based on these similarities, reviewing published literature on the spray characteristics of these three liquid–liquid injectors in LRE is necessary and will facilitate the investigation of spray characteristics of liquid–liquid pintle injectors to meet the progress of variable-thrust LRE. This review covers the following aspects of these injectors: basic spray morphology, liquid sheet characteristics and disintegration mechanisms, and atomization characteristics. For impinging-jet injectors, rim instability and impact wave play crucial roles in spray morphology and disintegration. Jet Weber number is of great importance for liquid sheet breakup length and mean droplet diameter. In the case of liquid–liquid coaxial swirl injectors, the overall spray morphology is similar to that of pressure swirl injectors, but it may feature two separate liquid sheets. The recess length strongly influences spray morphology, spray angle, breakup length, and Sauter mean diameter. Liquid–liquid pintle injectors can be simplified to injection element, in which the spray morphology resembles a cloak-like shape. In a complete pintle injector, the spray forms a conical liquid sheet. Momentum ratio proves to be the most significant parameter for predicting spray angle. Although the review indicates substantial progress has been made in understanding spray characteristics of liquid–liquid injectors, there remain several shortcomings that require further research, particularly for pintle injectors, which can be learned from the other two injectors.

Variable Area Jet Impingement for Enhanced Junction Temperature Control of High-Power Electronics

Abstract Convective heat transfer by jet impingement cooling offers a suitable solution for high heat flux applications. Compared to techniques that rely on bulk conduction in series with convection, direct liquid impingement reduces the thermal resistance between power device hot spots and the coolant. Although capable of highly efficient cooling, static impingement devices must be designed for the worst-case cooling requirements for a transient power profile. This can result in wasted hydraulic performance. Aircraft, highway vehicles, and heavy machinery fall into this category where a substantial factor of safety is required. This work proposes a method for improving power electronics reliability by limiting temperature fluctuations at reduced coolant pressure requirements during transient power cycling using a variable area jet. Single phase jet impingement cooling is implemented in an active control scheme using a variable diameter iris mechanism as the primary nozzle architecture. In addition to pressure drop and temperature control, the active nozzle structure introduces the ability to create pulsating jet flows to further enhance the heat transfer compared to fixed-geometry nozzles. The key underlying fluid mechanics characteristic of pulsating flows is the effect of disrupting the thermal boundary layer on the electrical device surface. By introducing a variable diameter jet, eddy formation can be fine-tuned for optimal boundary layer disruption. Using the definition of the Strouhal number, vortex shedding created by the non-steady jet flows is directly correlated with the resulting Nusselt number as a function of the iris kinematics. An experimental apparatus for jet impingement thermal-fluid testing is used to evaluate the Nusselt number versus Strouhal number for a parametric study of variable diameter iris configurations. The apparatus utilizes a voice coil actuator to achieve sine and square waveforms, to vary the amplitude of actuation, and to vary the mean of actuation. Finally, power cycling with a single emulated hot spot is performed to estimate the reliability increase as a result of maintaining constant junction temperatures with the active jet impingement scheme.

Numerical research on the flow and heat transfer characteristics in the immersion jet cooling for servers

Immersion cooling and jet impingement liquid cooling, as two of the significant emerging direct contact liquid cooling methods, have promising prospects for development and application. The two cooling methods are combined and numerical simulation is applied to study the heat transfer performance of the immersion jet-cooled server. The orthogonal method is employed to determine the optimal structural parameters of the immersion jet, and the flow and heat transfer characteristics under different inlet and outlet layouts are investigated. The study shows that the optimal heat dissipation effect and moderate pressure are achieved when the ratio of jet distance (L) to jet pipe diameter (D) is 1.2, and the ratio of jet hole spacing to jet orifice diameter is 11.1. When the inlet and outlet of the cabinet are arranged in a Z-shaped layout, the pressure on the server surface is reduced by 17.1 %–31.6 % compared to a U-shaped layout. When the inlet and outlet of the cabinet are arranged in a Z-shaped manner with the inlet at the bottom and the outlet at the top, the highest heat transfer coefficient is over 24000 W/(m2· K), which is approximately 1.5 times higher than that of other layouts. Through dimensional analysis, a quadratic function was selected to fit the relationship between heat transfer coefficient h, server pressure P and jet ratio (D/L), opening area A; In addition, the criterion relationship of Nu = f (Re, Eu) is fitted according to the simulation data, which provides a theoretical basis for energy saving and consumption reduction in data centers.

Characterization of loss, temperature, and stress on partial admission axial impulse turbines with liquid jet impingement cooling

The turbines for underwater applications can use abundant water as the cooling medium. However, the use of liquid water is associated with the multi-phase and multi-physics problems and presents additional losses. This paper proposes a numerical coupling method and corresponding loss breakdown approach to analyze the performance of this particular turbine cooling problem at different water mass flow rates. The results show that the cooling water induces additional loss, while the influence of the resulted structural deformation on turbine efficiency is comparatively small. Through numerical loss breakdown, it is found that the exit kinetic energy loss is significantly decreased, but other losses are increased correspondingly due to the cooling water. By examining the turbine stress and temperature distribution, the small water mass flow rate of 0.02 kg/s is sufficient to avoid damage to the disc, however, additional cooling is necessary to minimize the plastic region at the turbine blades. The suitable loss model for the turbine with cooling water is established and a relative difference less than 3 % is attained by comparing mean-line and numerical results. This work provides new insight into the analysis method and characteristics of the partial admission axial turbine with cooling water.

Real-Time Particle Emission Monitoring for the Non-Invasive Prediction of Lung Deposition via a Dry Powder Inhaler

Although inhalation therapy represents a promising drug delivery route for the treatment of respiratory diseases, the real-time evaluation of lung drug deposition remains an area yet to be fully explored. To evaluate the utility of the photo reflection method (PRM) as a real-time non-invasive monitoring of pulmonary drug delivery, the relationship between particle emission signals measured by the PRM and in vitro inhalation performance was evaluated in this study. Symbicort® Turbuhaler® was used as a model dry powder inhaler. In vitro aerodynamic particle deposition was evaluated using a twin-stage liquid impinger (TSLI). Four different inhalation patterns were defined based on the slope of increased flow rate (4.9–9.8 L/s2) and peak flow rate (30 L/min and 60 L/min). The inhalation flow rate and particle emission profile were measured using an inhalation flow meter and a PRM drug release detector, respectively. The inhalation performance was characterized by output efficiency (OE, %) and stage 2 deposition of TSLI (an index of the deagglomerating efficiency, St2, %). The OE × St2 is defined as the amount delivered to the lungs. The particle emissions generated by four different inhalation patterns were completed within 0.4 s after the start of inhalation, and were observed as a sharper and larger peak under conditions of a higher flow increase rate. These were significantly correlated between the OE or OE × St2 and the photo reflection signal (p < 0.001). The particle emission signal by PRM could be a useful non-invasive real-time monitoring tool for dry powder inhalers.Graphical

Optimising liquid impingement jet arrays for concentrated heat sources

This work seeks to investigate jet array impingement liquid cooling of CPU processors that utilise Integrated Heat Spreaders. In this study, single and centralised heat sources of various sizes (10 mm to 20 mm) were investigated, and a series of single and multi-objective optimisation studies were carried out to determine the optimum arrangement of microjets for different heat source sizes based on variable geometric inputs of the jet orifice plate. The results indicated that the design of the optimum jet orifice strongly depends on the size of the heat source as well as whether the target optimisation strategy is to achieve minimum thermal resistance, or both minimum thermal resistance and minimum pumping power simultaneously. A clustering of quite different orifice designs in optimal zones is observed, where approximately the same hydraulic and/or thermal performance is observed.

Optimization Design of a Recovery System for an Automatic Spray Robot and the Simulation of VOC Recovery

A recovery system for an automatic spraying robot to conduct the spraying operation outdoors for ships is designed in this paper, which addresses the pollution problem of volatile organic compounds (VOCs) by employing the vacuum recovery method. The recovery system consists of the recovery hood, nozzle, and vacuum tubes. The recovery hood is the critical part of the recovery system and is designed with internal and external cavities, as well as four vacuum tubes for recycling VOCs. Based on the computational fluid dynamics (CFD) method, simulation in the time domain of the gas–liquid interaction, droplet evaporation, and wall impingement is conducted. To identify the better recovery performance, three vacuum recovery-hood schemes are designed, and their performance is compared. The numerical results show that the distance between the vacuum tubes and the intake gap has a significant impact on the VOCs’ recovery effect. One of the main reasons for the escape of VOCs is that the swirling airflows in the baffle plane act as vortices which may capture VOCs, causing the accumulation of VOCs beyond the capacity of the external cavity. Dividing the external cavity into four chambers with deflectors (with each chamber equipped with one vacuum tube only) can significantly reduce the leakage rate of the recovery system. The recovery system provides a theoretical solution for implementing the prevention and control of VOCs in shipyards as soon as possible.

Droplet collision of hypergolic propellants

AbstractIn the present mini‐review, droplet impacting on a liquid pool, jet impingement, and binary droplet collision of nonreacting liquids are first summarized in terms of basic phenomena and the corresponding nondimensional parameters. Then, two representative hypergolic bipropellant systems, a hypergolic fuel of N,N,N′,N′‐tetramethylethylenediamine (TMEDA) and an oxidizer of white fuming nitric acid (WFNA) and a monoethanolamine‐based fuel (MEA‐NaBH4) and a high‐density hydrogen peroxide (H2O2), are discussed in detail to unveil the rich underlying physics such as liquid‐phase reaction, heat transfer, phase change, and gas‐phase reaction. This review focuses on quantifying and interpreting the parametric dependence of the gas‐phase ignition induced by droplet collision of liquid hypergolic propellants. The advances in droplet collision of hypergolic propellants are important for modeling the real hypergolic impinging‐jet (spray) combustion and for the design optimization of orbit‐maneuver rocket engines.

Effects of Nozzle Pitch Adaptation in Micro-Scale Liquid Jet Impingement

With ever increasing integration density of electronic components, the demand for cooling solutions capable of removing the heat generated by such systems grows along with it. It has been shown that a viable answer to this demand is the use of direct liquid jet impingement. While this method can generally be scaled to the cooling of large areas, this is restricted by the necessity of coolant flow rate scaling. In this study, the benefits and restrictions of using increased nozzle pitch to remedy the increasing demand for overall flow rate are investigated. To this end, a model is validated against experimental findings and then used for computational fluid dynamics simulations, exploring effects of the pitch change for micro-scale nozzle diameters and nozzle-to-target spacings. It is found that while this method is efficient in adjusting the tradeoff between total coolant flow rate and pressure drop up to a certain pint, the occurrence of a hydraulic jump in the cavity causes a deterioration of its effect for large nozzle pitches.

Experimental investigation of liquid jet impingement heat transfer at superhydrophobic surfaces

This paper presents an experimental exploration of thermal transport due to a water jet impinging on post patterned superhydrophobic surfaces and provides the first experimental data for this problem. The surface is heated to temperatures much lower than the saturation value. Results are obtained for a smooth hydrophobic surface and superhydrophobic surfaces with varying microfeature pitch (w = 8, 16, and 24 µm) and cavity fraction (Fc = 0.56 and 0.85) and are compared to results derived from a previously published analytical model. The jet Reynolds number varied from 1.1 × 104 to 1.7 × 104 and the nominal surface heat flux varied from 2.5 × 104 to 4.9 × 104 W/m2. Results obtained for all superhydrophobic surfaces show a significant decrease in the local and average Nusselt numbers (up to 30 % reduction) compared to impingement on a smooth surface. Further, the reduction is a strong function of the surface post and cavity geometric parameters. The effective temperature jump length is determined for all scenarios considered, representing the first experimental measurements of temperature jump length for heat transfer at superhydrophobic surfaces. Functional relationships showing how the average Nusselt number and the non-dimensional temperature jump length depend on the superhydrophobic surface parameters are also presented.

Slurry and liquid impingement erosion behavior of low-temperature plasma carburized AISI 420 martensitic stainless steel

The impact of plasma carburizing treatment on the erosion wear resistance of AISI 420 martensitic stainless steel (MSS) was studied. Experiments were carried out varying a broad spectrum of erosion parameters, including impact velocity, impact angle, and exposure duration. Both slurry and liquid impingement erosion were employed in the experiments, with testing conducted using both distilled water and saline solutions to assess the combined effects of corrosion and erosion wear. Compared to untreated samples, a significant improvement in the erosion wear resistance of AISI 420 MSS due to low-temperature plasma carburizing treatment was observed for all tested conditions. The observed performance enhancement can be attributed to the formation of the carburized layer, constituted of the α'C and Fe3C phases. Results also highlighted that the severity of the tribosystem was significantly influenced by the test solution characteristics. A marginal increase in severity was observed upon introducing the saline solution, while a more substantial severity increase occurred with the addition of solid particles in the test fluid. The specimens' mass loss was increased by increasing impact velocity, following a simple potential relationship, and with impact angle, following a first-degree linear equation. In the case of the exposure time, the mass loss curves depended on the test environment. For solutions containing quartz particles, an additional final stabilization stage was observed in addition to the acceleration stage observed in the absence of abrasive component. This phenomenon was attributed to surface work hardening induced by the impact of solid particles. Regarding wear mechanisms, samples tested only with distilled water displayed erosion flow marks. Those containing distilled water and NaCl exhibited not only flow marks but also pits. Lastly, solutions containing solid particles additionally presented features of plastic deformation, lip formation, craters, indentations, and extruded material.

Air monitoring by nanopore sequencing.

While the air microbiome and its diversity are essential for human health and ecosystem resilience, comprehensive air microbial diversity monitoring has remained rare, so that little is known about the air microbiome's composition, distribution, or functionality. Here we show that nanopore sequencing-based metagenomics can robustly assess the air microbiome in combination with active air sampling through liquid impingement and tailored computational analysis. We provide fast and portable laboratory and computational approaches for air microbiome profiling, which we leverage to robustly assess the taxonomic composition of the core air microbiome of a controlled greenhouse environment and of a natural outdoor environment. We show that long-read sequencing can resolve species-level annotations and specific ecosystem functions through de novo metagenomic assemblies despite the low amount of fragmented DNA used as an input for nanopore sequencing. We then apply our pipeline to assess the diversity and variability of an urban air microbiome, using Barcelona, Spain, as an example; this randomized experiment gives first insights into the presence of highly stable location-specific air microbiomes within the city's boundaries, and showcases the robust microbial assessments that can be achieved through automatable, fast, and portable nanopore sequencing technology.

Tribocorrosion behavior of low-temperature plasma-carburized AISI 420 martensitic stainless steel: Investigating the synergy between corrosion and erosion in slurry and liquid impingement environments

Erosion-corrosion is a significant concern across industries, impacting equipment lifespan and efficiency. When erosion-corrosion occurs, the resulting damage becomes complex, often leading to greater mass loss than that observed with erosion or corrosion alone. Martensitic stainless steels (MSSs) are commonly used in such environments due to their favorable combination of mechanical and corrosion resistance. However, under severe tribocorrosive conditions, it is necessary to apply surface treatments to prevent rapid steel degradation. Carburizing treatment is known to independently enhance the corrosion and erosion resistance of MSS. Nonetheless, there is a limited understanding of the impact of carburizing on the synergy between corrosion and erosion in such steels. In this study, we examined two different tribocorrosion conditions, assessing the resistance to slurry erosion and liquid impingement erosion for both carburized and non-carburized AISI420 MSS specimens exposed to a corrosive agent (from an electrochemical test using a 3.5 %-NaCl solution). To provide a basis for comparison, a static corrosion test was also performed to evaluate the environmental impact, with the electrolyte at rest, without flow or particles. Our findings revealed that the carburized layer is responsible for reducing the corrosion current density and increasing corrosion potential of AISI420 MSS. In contrast, slurry and liquid impingement erosion result in an increased corrosion current density and a decreased corrosion potential. The parameters Ω and Ω' (role of carburizing on the relationships between ‘slurry erosion and corrosion’ and ‘liquid impingement erosion and corrosion’ mechanisms interaction, respectively) demonstrated that carburizing application mitigates the impact of slurry and liquid impingement erosion, respectively. Additionally, the carburizing treatment reduces the corrosion rate, total mass loss, and erosion-induced mass loss of the studied samples, minimizing the synergy between erosion and corrosion. Finally, the interactions between the degradation modes reveal that erosion predominantly governs the AISI420 MSS deterioration process.

Assessment of Critical Quality Attributes of Budesonide and Formoterol Fumarate Dihydrate in Dry Powder Inhalers Marketed in Pakistan

Dry powder inhalers (DPIs) have been well established and recognized for the delivery to the lungs. It provides better drug stability, less irritable, easy to use with deep penetration of drugs in the lungs. Budesonide (BDS) and formoterol fumarate dihydrate (FFD) indicated in pulmonary diseases. The main aim of the study is to evaluate BDS, FFD and their marketed DPIs product in Pakistan were compare in quality and performance with the reference product. The particle size distribution and aerodynamic characterization were analyzed by laser diffraction and multi stage liquid impinger, respectively. The particle density and delivered dose uniformity were also determined. HPLC was also used for the qualitative and quantitative estimation of BDS and FFD along with its marketed products. Laser diffraction particle size analyzer revealed Dv50 53.27 to 56.34 and#181;m having surface area 1815 to 2304 cm3/g. The percentages of emitted dose (%ED) and fine particle fraction (%FPF) was found 98.19 to 99.23% and 31.57 to 34.87%, respectively. The mass median aerodynamic diameter (MMAD) and geometric standard deviation (GSD) were calculated 2.62 to 2.89 and#181;m and 1.99 to 2.54, correspondingly. The quantitative assay of BDS and FFD in all the commercial DPIs and reference product were well within the pharmacopeial limit i.e. 97.26 to 101.36%. The average of ten units results of delivered dose uniformity for BSD and FFD were also found in the range i.e. 97.97 to 103.19% and 98.48 to 104.41 %, respectively. The results of evaluation of parameters of DPIs like Dv50, %ED, %FPF, MMAD, GSD has shown compliance with the pharmacopeial standards. It is concluded that the all DPIs of BDS/FFD marketed in Pakistan has revealed conformance with the standard of pharmacopoeia and meet the requirements of drug regulatory authority of Pakistan.

Experimental investigation on self-induced jet impingement boiling using R1336mzz(Z)

Pool boiling performance enhancement has attracted considerable interest on high power electronic cooling. In this paper, we introduce a self-induced jet impingement device for practical boiling enhancement, achieved by integrating the guidance tube with an orifice plate. With R1336mzz(Z) as the working fluid, we conduct visualization and parametric investigations on the pool boiling performance, considering the varying characteristics of this device. Visualization snapshots confirm the liquid-vapor separation and indicate that the two-phase flow pattern in the guidance tube eventually stabilizes as a churn-annular flow. Our findings suggest that self-induced liquid jet impingement has a minimal effect on the nucleate boiling heat transfer coefficient (hNB) under a certain heat flux, around 75 % CHF of the standard pool boiling, as the single-phase heat transfer is weakened due to the low thermal conductivity of R1336mzz(Z). As the heat flux intensifies, we observe substantial enhancements in both the Critical Heat Flux (CHF) and the Maximum Nucleate Boiling Heat transfer coefficient (hMNB) resulted from the delayed onset of boiling crisis, owing to the additional liquid supply and the promotion on vapor exhausting. The parametric studies reveal that the flow rate of the liquid jet, amplified by either extending the length or the inner diameter of the guidance tube, or by increasing the number of jet holes, positively impacts the boiling performance. However, these improvements show diminishing returns. Our study shows enhancements in CHF and hMNB of up to 69.5 % and 36.7 %, respectively, compared to the standard pool boiling.

Experimental investigation of impact force variations during high-speed liquid impingement erosion

High-speed liquid impingement erosion occurs in many industrial settings. The erosion transition, which occurs after the incubation period of liquid impingement erosion, significantly changes the erosion behavior, such as the material erosion rate and surface roughness; however, when and how the transition occurs remains elusive. The study focused on the impact force exerted on a material by a liquid jet impact during the transition in high-speed liquid impingement erosion. To this end, the force acting on an aluminum specimen attached to a force sensor during liquid impingement erosion was examined experimentally. The critical condition, which indicates the beginning of the accumulation stage of erosion, was detected through mass-loss measurements and visual observation of the target material. The results demonstrated a distinctive transition in the impact force with respect to the exposed flow volume. Additionally, a dynamic mode decomposition technique was employed to analyze variations in the impact force. Finally, the mechanism underlying the long-term variation in the impact force was discussed, and the correlation between the impact forces and erosion depths during high-speed liquid impingement erosion was presented.

Heat transfer characteristics of oblique jet impingement liquid film cooling in the forced convection mode

Liquid film cooling by oblique jet impingement is widely used in small liquid rocket engine thermal protection. In this work, heat transfer characteristics of oblique jet impingement liquid film cooling in forced convective mode were experimentally investigated to examine the effect of the impingement velocity and the initial wall temperature. The temperature distribution on the rear surface (opposite to the jet) was recorded by a high-frequency infrared camera, and then the heat flux on the front surface was estimated by solving the inverse heat conduction problem. It was found that the lagging effect by thermal diffusion is nonnegligible and can be well described by the penetration time. In addition, thermal diffusion makes the temperature distribution on the rear surface more uniform than the liquid flow path. In contrast, the heat flux distribution has a clear boundary same as the liquid flow path. The length of the wetting front lwf can be fitted as lwf=atn. The constant a and the wetted area A are affected merely by the impingement velocity. The point with the maximum heat flux is located at the impingement point in the forced convective mode rather than the wetting front in the film boiling mode. Inside the liquid film, there is no clear boundary as the film thickness distribution between the thin layer zone and the raised zone, implying the local film velocity determines the heat transfer rather than the film thickness. The cooling power increases with higher impingement velocity and initial temperature difference. The standardization fitting equation shows the effect of the initial temperature difference on the cooling power is more significant than the impingement velocity.

Fluid–Thermal–Structural Analysis of Partial Admission Axial Impulse Turbines With Liquid Jet Impingement Cooling

Abstract Increasing turbine inlet temperature is beneficial to enhance turbine performance. However, this also results in stringent cooling requirements. Unlike turbines in air cycle machines, the partial admission axial impulse turbines for underwater vehicles can utilize the abundant seawater as the cooling medium. In addition, the short blades cannot accommodate the complex cooling channels used in aero-engines, and the alternative way is jet impingement liquid cooling. This paper proposes a fluid–thermal–structural coupling method to investigate the performance of partial admission axial impulse turbines with water-cooling on the rotating wheel front surface. The volume of fluid multiphase model is employed to study the transient gas–liquid interaction, while the Lee model is chosen to model the heat and mass transfer during phase change. Also, a two-way weakly coupling method among fluid, thermal, and structure is utilized to account for fluid–structure interaction. The results show that the temperature distribution at the turbine wheel drops significantly with the jet impingement liquid cooling. The turbine efficiency is also reduced by 3.38% due to the mixing of cooling medium and gas. From stress analysis, the use of water-cooling can minimize turbine damage and ensure stable turbine operation. This study provides insight into the cooling method for partial admission axial impulse turbines for the underwater vehicle.