Flow Field In Diffuser Research Articles

Fast flow field prediction of pollutant leakage diffusion based on deep learning.

Predicting pollutant leakage and diffusion processes is crucial for ensuring people's safety. While the deep learning method offers high simulation efficiency and superior generalization, there is currently a lack of research on predicting pollutant leakage and diffusion flow field using deep learning. Therefore, it is necessary to conduct further studies in this area. This paper introduces a two-level network method to model the flow characteristics of pollutant diffusion. The proposed method in this study demonstrates a significant enhancement in flow field prediction accuracy compared to traditional deep learning methods. Moreover, it improves computational efficiency by over 800 times compared to traditional computational fluid dynamics (CFD) methods. Unlike conventional CFD methods that require grid expansion to calculate all operation conditions, the deep learning method is not confined by grid limitations. While deep learning methods may not entirely replace CFD methods, they can serve as a valuable supplementary tool, expanding the versatility of CFD methods. The findings of this research establish a robust foundation for incorporating deep learning methods in addressing pollutant leakage and diffusion challenges.

Performance uniformity analysis in polymer electrolyte fuel cell using long-term dynamic simulation

The temporal stability and spatial homogeneity of current density are key factors in Polymer Electrolyte Fuel Cell (PEFC) performance and durability. Temporal and spatial variations of relative humidity, fuel concentration, and water droplets in the channels are the principal causes of non-homogeneous current density. A dynamic pseudo-3D model was previously proposed by the authors and has been extended and improved to perform the long-term and intensive simulations of PEFC with low computational cost, which allows to study of the performances homogeneity with different experimental configurations and flow field topologies. The model considers important phenomena in the homogeneity analysis, such as gases and liquid water movement in diffusion layers and flow field, electrochemical reactions, and others. Model validation has been performed using experimental data obtained from a 25 cm2 cell with a single serpentine, which has allowed studying the model transient response and spatial representation. The simulations have been used to study the homogeneity and stability of 36 setups of PEFC, varying the rib/channel width ratio, the stoichiometric ratio, and the number of parallel serpentine channels. The results show the importance of a properly flow field design to control gas flow, remove the channels’ liquid water, and keep a homogeneous feeding. The study evaluated a set of channel configurations that show the improved temporal voltage stability and current density spatial homogeneity. The results show the impact of channel gas speed and ratio channel/rib width in liquid droplets removal and the proper fuel spatial distribution; and how configurations with a lesser number of channels in serpentine design require a lower stoichiometric ratio to perform better temporal and spatial uniformity. In the case of the cell configurations simulated, the optimum design was achieved using between 5 and 7 parallel serpentine channels and a channel/rib ratio 3/5.

Study on the diffusion and deposition law of pore slurry in gangue filling zone based on CFD-DEM coupling.

In this study, the slurry diffusion in a cavity filled with coal gangue was studied by combining experimental and numerical simulation methods. By calibrating slurry and particle materials, the grouting process in coal gangue filling area is simulated successfully, and the change of slurry diffusion flow field and particle movement and settling process in different dimensions are deeply analyzed. Both experimental and numerical simulation results show that the particle settlement presents a bell-shaped curve, which is of great significance for understanding the particle movement and settlement behavior in the filling cavity. In addition, it is found that the grouting speed has a significant effect on the particle settlement during the slurry diffusion process. When the grouting speed increases from 0.1m /s to 0.2m /s, the particle settlement and diffusion range increases about twice. In the plane flow field, it is observed that the outward diffusion trend and speed of grouting are more obvious. It is worth noting that in the whole process of grouting, it is observed that with the increase of grouting distance and depth, both the velocity of slurry and particles show a trend of rapid initial decline and gradually slow down, and the flow velocity of slurry near the grouting outlet at a flow rate of 0.2m/s is 2-4 times that of 0.1m/s. This provides important enlightenment for the porous seepage effect at different grouting speeds.

Thermal and mechanical investigation of proton exchange membrane fuel cells under combined loading conditions

Mechanical performance of PEM fuel cells under combined loadings is one of critical issues in improving cell performance and reliability. In this study, thermal and mechanical performance of the PEM fuel cell under clamping force and temperature load are investigated by experiments and three-dimensional dynamic simulations. In experiments, pressure distributions between gas diffusion layer and flow field are measured by pressure sensitive films. The experimental results show that the local pressure increases with clamping load, and pressure distribution is much uneven in the midstream. Meanwhile, a three-dimensional model of the cell combined transient heat transfer and mechanical response of components is developed, which is validated by experimental data. The modeling results show that under combined loadings, the porosity of gas diffusion layer under the rib decreases, attributed to compressive deformation caused by thermal gradient and clamping pressure, leading to higher effective thermal conductivity and electrical conductivity. When at a higher temperature, the overall stresses of gas diffusion layer decrease and the minimum stress is located under the center rib, forming a concave stress distribution pattern. Distribution and variation patterns of local deformations and stresses for the membrane are similar to those of gas diffusion layer, but the maximum stress and deformation are much lower. A dimensional stress coefficient is proposed to determine the stress distribution uniformity under the rib. With the increase of clamping torque, dimensionless stress coefficients under lower ambient temperature change slightly. As temperature increases, dimensionless stress coefficients increase significantly and decrease with the clamping torque, indicating the decreasing role of temperature load on mechanical response of the cell.

Effect of Inlet Vane Angle of a Partial Vane Diffuser on the Performance and Flow Filed of a Centrifugal Compressor

The paper presents experimental results on the effect of inlet vane angle on the performance and flow field of Partial Vane Diffuser (PVD) of a low speed centrifugal compressor. Performance tests are conducted for eight configurations of PVDs. From these tests, an optimum configuration with 5° increase in inlet angle of partial diffuser vanes on shroud (PVDHS5) is selected for further measurements i.e. static pressure on the diffuser hub and shroud and diffuser passage flow field at four flow coefficients. From passage flow measurements flow parameters are obtained within the diffuser flow passage. Flow parameters are axially averaged and their contours are presented. Radial variation of these flow parameters is also presented. PVDHS5 gives 2.3% increase in peak energy coefficient and 4.9% increase in efficiency compared to that of vane less diffuser. The flow at the exit of PVDHS5 is more uniform.

Numerical simulation on the direct contact condensation in a steam-water two-phase ejector with non-condensable gas

The steam-water condensing ejector is widely used in many industrial fields and production processes. In the practical operation of ejectors in many systems such as nuclear reactors and underwater gas-ejection devices, the steam pressure is much higher than those in common direct heating systems or refrigeration systems. In addition, some non-condensable gas is inevitably mixed into steam jet. With the presence of non-condensable gas, the flow field and performance of ejector are significantly influenced by the changes in heat transfer characteristics. This paper presents a three-dimensional numerical simulation of the high-pressure steam-water condensing ejector with non-condensable gas based on inhomogeneous multiphase model. The steam inlet pressure, mass flow rate and non-condensable gas fraction are in the range of 0.70–2.40 MPa, 1019–3310 kg/(m2s) MPa and 0–0.05, respectively. The changes in steam plume shapes, distributions of thermal hydraulic parameters and pressure ratio are investigated under different boundary conditions. Numerical results show that the steam plume inside ejector transforms from ellipsoidal shape to divergent shape with the increase of steam inlet mass flow rate and the decrease of back pressure. The choking phenomenon in throat is found at divergent steam plume and the changes of flow field in diffuser do not spread upstream to the mixing chamber, so the thermal hydraulic parameters in mixing chamber and pressure ratio of ejector keep unchanged. In addition, the pressure ratio first increases from 1.08 to 2.34, then decreases to 1.99 with the increase of steam mass flux. As back pressure rises, the pressure ratio drops from 2.00 to 1.30 at low steam inlet mass flux; while first increasing linearly from 1.98 to 2.41 and then decreasing to 1.78 at high steam inlet mass flux. With the increase of non-condensable gas mass fraction, the pressure ratio slowly decreases from 1.48 to 1.39 at low steam mass flux while rapidly decreasing from 4.00 to 1.65 at high steam mass flux.

Leakage Analysis and Hazardous Boundary Determination of Buried Gas Pipeline Considering Underground Adjacent Confined Space

Urban underground construction projects are intertwined vertically and horizontally, and adjacent confined spaces such as water supply and drainage pipelines, side ditches and underground canals may exist near buried gas pipelines. Once the buried gas pipeline leaks, the gas will diffuse into the confined space through the soil and even enter the residential room by the confined space, which brings serious potential safety hazards. In this paper, the underground adjacent confined space hazardous boundary (HB) of underground gas pipeline leakage was defined, the distribution properties of gas leakage diffusion flow field were analyzed by numerical simulation and the distribution law of gas entering the confined space was studied. Using the least-squares method and multiple regression theory, the gas concentration prediction model in the adjacent confined space of buried gas pipeline leakage was established, the HB calculation model was further deduced, and the HB drawing board was drawn. The results showed that in the initial stages, the internal and external pressure and velocity distribution of the pipeline near the leakage hole were unstable, reaching a stable state after 60 s, and then the reverse flow occurred in the pipeline downstream of the leak hole. Reducing the minimum construction distance between the buried gas pipeline and the confined space improved the gas distribution concentration in the confined space. When the minimum construction distance increased from 3 m to 9 m, the gas concentration distribution decreased from 90.21% to 0.88%. Meanwhile, increasing the pipeline pressure and leakage diameter enhanced the gas concentration distribution in the confined space. The HB calculation model and HB drawing board realize the rapid determination of the HB between buried gas pipeline and confined space and offer a more reasonable basis for the design of gas pipeline safe distance in urban underground engineering construction.

Structural Response of a Single-Stage Centrifugal Compressor to Fluid-Induced Excitations at Low-Flow Operating Condition: Experimental and Numerical Study

The article describes an assessment of possible changes in constant fatigue life of a medium flow-coefficient centrifugal compressor impeller subject to operation at close-to-surge point. Some aspects of duct acoustics are additionally analyzed. The experimental measurements at partial load are presented and are primarily used for validation of unidirectionally coupled fluid-structural numerical model. The model is based on unsteady finite-volume fluid-flow simulations and on finite-element transient structural analysis. The validation is followed by the model implementation to replicate the industry-scale loads with reasonably higher rotational speed and suction pressure. The approach demonstrates satisfactory accuracy in prediction of stage performance and unsteady flow field in vaneless diffuser. The latter is deduced from signal analysis relying on continuous wavelet transformations. On the other hand, it is found that the aerodynamic incidence losses at close-to-surge point are underpredicted. The structural simulation generates considerable amounts of numerical noise, which has to be separated prior to evaluation of fluid-induced dynamic strain. The main source of disturbance is defined as a stationary region of static pressure drop caused by flow contraction at volute tongue and leading to first engine-order excitation in rotating frame of reference. Eventually, it is concluded that the amplitude of excitation is too low to lead to any additional fatigue.

Experimental influence of a splitter vane on the flow fields in a wide-angled diffuser

Based on PIV and high-speed photography technology, the lengths and area ratios of flow separation zone under different Reynolds numbers Re in a diffuser with a fixed angle (28º), with and without a splitter vane were obtained. The flow field, vorticity and the flow distribution (hydrogen bubble tracing) at the downstream vicinity of the outlet of the diffuser under three representative conditions (Re = 1000, 6000 and 12000) were given. The experimental results show that with increasing Re, the area proportion of the separation zone decreases, but the length proportion of the separation zone increases, because the thickness of the separation zone along the vertical flow direction is reduced. Due to the existence of vane, the area of the corresponding separation zone is always smaller than that without the vane.

Numerical simulation of gas dispersion from rooftop stacks on buildings in urban environments under changes in atmospheric thermal stability.

The prediction of dispersion of gases emitted from rooftop stacks in a built environment is important for preventing or minimizing their harmful effects on human health. In this study, the wind flow and dispersion of exhaust gas emitted from rooftop stacks on buildings in an urban environment under different atmospheric thermal stabilities were investigated using numerical simulations. The wind flow field and dispersion contaminants were simulated using a computational fluid dynamics model with the k-ε turbulent schemes being resolved by the Reynolds-averaged Navier-Stokes approach. An isolated building was modeled under conditions of varying thermal stratification of the boundary layers (neutral, unstable, and stable conditions). The diffusion flow field within the building wake zone was investigated for various stack sites (center, right side, and left side). Experiments were conducted in a wind tunnel to validate the numerical simulation results, by using the data qualitatively and quantitatively. The numerical simulation results were consistent with the experimental observations. The results indicated that the pollutant concentration of the plume spread was high near the stack and decreased with increasing distance from the stack. Under stable conditions, the flow motion and separation increased in the wake zone, and the pollutant concentration of the lateral spread at the average human height decreased. Under unstable conditions, the flow of the vortex circulation was fast and strong, and the pollutant concentration of the vertical spread was high.

Rotor-Alone Tones in the Outflow Noise of a Centrifugal Compressor

Abstract This article investigates the generation of rotor-alone tones and their contribution to the outflow noise of a transonic centrifugal compressor stage with vaneless diffuser and volute by means of unsteady full-annulus computational fluid dynamics (CFD) simulations. The aerodynamic field and the generation and propagation of sound were simulated simultaneously using the unsteady Reynolds-averaged Navier–Stokes (URANS) approach of the solver trace and a numerical grid consisting of 170 M cells. To assess the accuracy of the predicted fluctuations, the investigation compares the simulated diffuser flow field to measured flow angles and pressure fluctuations obtained from experiments conducted on a large-scale test rig. The analysis explains the different sound generation mechanisms responsible for tonal components in the acoustic spectrum at the compressor outlet based on the Fourier decomposition of the pressure fluctuations in diffuser and volute. Furthermore, this article analyzes the modal structure of the simulated sound field at the volute outlet by means of a radial mode analysis and discusses the influence of changing operating conditions on the sound power emitted. The analyses reveal that supersonic flow phenomena occurring at choked operating conditions cause a significant increase in noise emissions. Furthermore, the investigation shows that the sound field at the volute outlet is dominated by few low-order modes, a fact that justifies the analysis using methods based on the compressed sensing in future experimental investigations.

Multi-phase simulation of proton exchange membrane fuel cell with 3D fine mesh flow field

A three-dimensional (3D) multi-phase numerical model of proton exchange membrane fuel cell (PEMFC) is built. The catalyst layer (CL) spherical agglomerate model is used to replace traditional homogenous model, which can predict the concentration loss in PEMFC more accurately. Utilizing this multi-phase model, the PEMFC with 3D fine mesh flow field is investigated at length, and the liquid water distribution in 3D flow field is qualitatively compared with the experimental image in previous literature. It is found that the 3D fine mesh flow field can improve the reactant gas supply from flow field to porous electrodes significantly and facilitate liquid water removal in PEMFC simultaneously. Therefore, it reduces the concentration loss of PEMFC effectively without increasing the pumping power loss thanks to the greatly increased mass transfer area between gas diffusion layer (GDL) and flow field and vertical flow design of hydrogen and air, which also make the reaction rate distribution in CL more uniform. However, the decreased contact area between GDL and bipolar plate in 3D flow field may decrease PEMFC performance at the current densities where ohmic loss is dominated, but its effect is insignificant.

PIV validation of different turbulence models used for numerical simulation of a centrifugal pump diffuser

PurposeThe purpose of this study is to validate the different turbulence models using in the numerical simulation of centrifugal pump diffuser. Computational fluid dynamics (CFD) has become the main method to study the pump inner flow patterns. It is important to understand the differences and features of the different turbulence models used in turbomachinery.Design/methodology/approachThe velocity flow fields in a compact return diffuser under different flow conditions are studied and compared between CFD and particle image velocimetry (PIV) measurements. Three turbulence models are used to solve the steady flow field using high-quality fine structured grids, including shear stress transport (SST) k-w model, detached-eddy simulation (DES) model and SST k-w model with low-Re corrections.FindingsSST k-w model with low-Re correction gives better results compared to DES and SST k-w model, and gives a good predication about the vortex core position under strong part-loading conditions.Originality/valueA special test rig is designed to carry out the 2D PIV measurements under high rotating speed of 2850 r/min, and the PIV results are used to validate the CFD results.

An Investigation of the Stability Enhancement of a Centrifugal Compressor Stage Using a Porous Throat Diffuser

The stable operating range of a centrifugal compressor stage of an engine turbocharger is limited at low mass flow rates by aerodynamic instabilities which can lead to the onset of rotating stall or surge. There have been many techniques employed to increase the stable operating range of centrifugal compressor stages. The literature demonstrates that there are various possibilities for adding special treatments to the nominal diffuser vane geometry, or including injection or bleed flows to modify the diffuser flow field in order to influence diffuser stability. One such treatment is the porous throat diffuser (PTD). Although the benefits of this technique have been proven in the existing literature, a comprehensive understanding of how this technique operates is not yet available. This paper uses experimental measurements from a high pressure ratio (PR) compressor stage to acquire a sound understanding of the flow features within the vaned diffuser which affect the stability of the overall compression system and investigate the stabilizing mechanism of the porous throat diffuser. The nonuniform circumferential pressure imposed by the asymmetric volute is experimentally and numerically examined to understand if this provides a preferential location for stall inception in the diffuser. The following hypothesis is confirmed: linking of the diffuser throats via the side cavity equalizes the diffuser throat pressure, thus creating a more homogeneous circumferential pressure distribution, which delays stall inception to lower flow rates. The results of the porous throat diffuser configuration are compared to a standard vaned diffuser compressor stage in terms of overall compressor performance parameters, circumferential pressure nonuniformity at various locations through the compressor stage and diffuser subcomponent analysis. The diffuser inlet region was found to be the element most influenced by the porous throat diffuser, and the stability limit is mainly governed by this element.

Computation of Developing Turbulent Flow through a Straight Asymmetric Diffuser with Moderate Adverse Pressure Gradient

In this paper, numerical investigation of three-dimensional, developing turbulent flow, subjected to a moderate adverse pressure gradient, has been investigated using various turbulence models, namely: the low-Re , the SST , the and a variant of Reynolds stress model. The results are compared with the detailed velocity and pressure measurements. Since the inlet condition is uncertain, a study was first performed to investigate the sensitivity of the results to the inlet boundary condition. The results showed the importance of including the contraction effects. It is seen that the developing flow inside the straight duct, is highly sensitive to the inlet boundary condition. The comparisons indicate that all turbulence models are able to predict a correct trend for the centerline velocity and pressure recovery inside the straight duct and diffuser but the low-Re and RSM turbulence models yield more realistic results. The SST model largely overpredicts the centerline velocity and boundary layer thickness in the straight duct. The comparisons of the numerical results also revealed that the RSM model, due to its anisotropic formulation, is able to reproduce the secondary flows. As expected, the RSM model demonstrates the best performance in prediction of the flow field and pressure recovery in the asymmetric diffuser.

Experimental and numerical study of flow characteristics of flat-walled diffuser/nozzles for valveless piezoelectric micropumps

The flat-walled diffuser/nozzles are classified into two types, i.e. Tube I and Tube II, based on their different flow resistance characteristics. Tube I has less pressure loss coefficients in the diffuser direction than the nozzle direction, and Tube II has larger pressure loss coefficients in the diffuser direction than the nozzle direction. This work focuses on the characterization of the diffuser efficiency, and flow rectification of these two types of diffuser/nozzles. The characterization is performed with diverging angles in the range of 5°–60° and length–width ratios in the range of 1–20, and the pressure drop ranging from 1 to 10 kPa. The results show that with the increase in pressure drop and the decrease in length–width ratio, Tube I type of diffuser/nozzles can change to Tube II. For Tube I type of diffuser/nozzles, the smaller the diverging angle and the longer the length, the better the performance. For Tube II type of diffuser/nozzles, the larger the diverging angle and shorter the length, the better the flow rectification performance. Simulation results match well with the experiment data. Of particular interest, simulation of the diffuser flow fields suggests that the flow separation has a significant impact on pressure loss coefficients in the diffuser direction.

The effect of impeller–diffuser interactions on diffuser performance in a centrifugal compressor

ABSTRACTThe unsteady phenomenon abounds in centrifugal compressors and significantly affects the compressor performance. In this paper, unsteady simulations are carried out to investigate the aerodynamic performance of a process-unshrouded centrifugal compressor and the unsteady mechanism in the vaned diffuser. The predicted stage performance and pressure fluctuations at some locations are in good agreement with experimental data. The predicted main pressure fluctuation frequency spectrums at the diffuser inlet and outlet are consistent with the measured results. The results indicate that at the inlet of the diffuser there are two pressure peaks in a passage cycle. The higher pressure peak relates to the impeller wake and the lower peak is connected with the vortex generated at the diffuser’s leading edge. With a decrease in the mass flow coefficient, the vortex core region becomes larger and the lower pressure peak becomes more pronounced. The change in circumferential flow angle at the diffuser inlet is mainly responsible for the unsteadiness in the diffuser flow field, which in turn affects the inlet incidence of the diffuser vane and the vane loading distributions.

Design of Flow Adjusting Device in Diffuser of Open-Circuit Wind Tunnel with Low Speed Based on CFX

The diffuser in wind tunnel plays a vital role to improve flow field quality. Many flow adjusting devices in diffuser were studied by lots of researchers in the world to inhibit flow separation. However, most of them were applied on closed-circuit wind tunnel with high speed. It is necessary to design appropriate flow adjusting device for diffuser in open-circuit wind tunnel with low speed which was increasingly used in aerodynamic experiment. The structure of a new open-circuit wind tunnel with low speed was firstly introduced in this paper. The flow adjusting device was designed, which was composed of three parts, namely contracting cone, air guide plate and screen. On the basis of analysis model for diffuser, the influences of contracting cone, air guide plate and screen on flow field quality were respectively given by CFX simulation that was using multiple reference frames and RNG k-ε turbulence model. Case study showed that the role of single part was limited, combined effect of three parts in flow adjusting device could greatly improve quality of flow field in diffuser. The study results mentioned above are useful for designing flow adjusting device in diffuser of practical open-circuit wind tunnel with low speed.

Imaging Phosphoric Acid Migration in High Temperature Polymer Electrolyte Fuel Cells by X-Ray Tomographic Microscopy

High temperature polymer electrolyte fuel cells (HT-PEFC) use phosphoric acid (PA) as the proton conducting electrolyte, which is imbibed in a polybenzimidazole (PBI) membrane. The low vapour pressure of PA allows for increased operating temperatures of up to 200°C. At the higher operating temperatures, the tolerance to fuel gas impurities increases significantly and operation with CO levels up to 3% and H2S up to 10 ppm can be achieved.1 Phosphoric acid doped PBI membranes are therefore ideal candidates for cost-efficient combined heat and power (CHP) as well as hydrogen separation, purification and pumping applications. Unlike low temperature sulfonic acid based PEFC, the electrolyte is not covalently bound to the polymer backbone of the membrane and migration of anions in the electric field can occur similar to what has been observed in phosphoric acid fuel cells (PAFC).2,3 We have recently demonstrated how X-ray tomographic microscopy (XTM) can be applied for imaging electrolyte migration in HT-PEFC under dynamic operation.4 It was shown, for the first time, that PBI based membrane systems exhibit extensive PA migration from cathode to anode under high current operation. PA flooding of the anode gas diffusion layer (GLD) and flow field channel was observed. In this contribution, the application of synchrotron based XTM for in-operando imaging and quantification of migrated phosphoric acid in HT-PEFC will be presented. The influence of current density, temperature, membrane material (conventional m-PBI film casted5 and sol-gel based6 membranes) and phosphoric acid loading will be discussed. [1] T. J. Schmidt and J. Baurmeister, ECS Trans., 3, 861–869 (2006). [2] H. R. Kunz, ECS Trans., 11, 1447–1460 (2007). [3] H. R. Kunz, Electrochem. Soc. Proc., 99-14, 191–207 (1999). [4] S. H. Eberhardt, M. Toulec, F. Marone, M. Stampanoni, F. N. Büchi, and T. J. Schmidt, J. Electrochem. Soc., 162, F310–F316 (2015). [5] R. Savinell, E. Yeager, D. Tryk, U. Landau, J. Wainright, D. Weng, K. Lux, M. Litt, and C. Rogers, J. Elelectrochemical Soc., 141, L46–L48 (1994). [6] L. Xiao, H. Zhang, T. Jana, E. Scanlon, R. Chen, E.-W. Choe, L. S. Ramanathan, S. Yu, and B. C. Benicewicz, Fuel Cells, 5, 287–295 (2005).

Impact of Cationic Impurities on Low-Pt Loading PEFC Cathodes

Many demanding issues still need to be addressed before full commercialization of PEFC can take place, and cationic contamination is one of the major obstacles. Foreign cations diminish proton conductivity and affect water content of the polymer electrolyte membrane, increasing the cell performance losses. Foreign cations may originate from the soil, road salts, corrosion of the cell, stack, components, as well as coolant fluids, and balance of plant (BoP) components. Among the cations, Ca2+ receives special attention because it is one of the most prevalent elements within our planet. In this work, sulfate (SO4 2−) is selected as the anion due to its compatibility with the PEFC, considering sulfuric acid is a common catalyst and electrode characterization solution. The cation solution injection at cathode was employed to better control on dosage and to emulate cationic contamination of fuel cells under actual conditions [1]. To test the real world condition and obtain the consistent data, the commercially available the low loading catalyst (Pt: 0.1 mg /cm2) coated membrane (GORE Inc.) was used. During the contaminant test, cell was maintained at 80◦C with anode H2 and cathode air flow rates of 1.75 slpm and 1.66 slpm, respectively. The CaSO4 solution of 5 ppm of total concentration was injected (130 µl/min) at the cathode inlet using nebulizer [1]. Overall, the anode/cathode RH was maintained at 25%/125%, and the anode/cathode outlet back pressure was maintained at 10 kPa/100 kPa gauge pressure (∼1.5 psig/15 psig, ambient pressure 1 atm), respectively. Figure 1 shows the cell voltage decay during the constant-current hold tests (1 A cm-2) with and without Ca 2+ solution injection. It is observed that during the initial injection of water there is no significant performance loss, whereas while injecting the CaSO4 solution (5 ppm) steep fall in cell voltage is observed. In order to get a clear understanding on factors that contribute to the severe voltage loss during the CaSO4 injection, pressure of the cathode inlet and outlet are monitored (Figure 1 (b)). These data reveal that the increased pressure over the time is due to salt precipitation in the cathode gas diffusion layer and the flow field, and the pressure gain trend is correlated with the voltage degradation. The cell test was stopped after 350 h of CaSO4injection due to blocking of the cathode outlet. The polarization curves were obtained before and after the injection of CaSO4(Figure 2), a sharp fall in voltage was observed in the case of end of test (EOT ) curve, which indicates a very severe mass transport loss due to blocking of the cathode outlet [1-3]. These studies confirm that apart from the contaminant effect in polymer electrolyte membranes and catalyst layer’s ionomer, there is a severe impact that comes from the salt precipitation at gas diffusion layer and flow field plates. In addition, the effect of contaminant on catalyst support corrosion, membrane conductivity loss over the time also performed. Acknowledgement Financial support from the Department of Energy (DOE)-EERE, DE-EE0000467 (University of Hawaii, prime contractor, Jean St-Pierre, PI) is greatly acknowledged. Reference X. Wang, J. Qi, O. Ozdemir, A. Uddin, U. Pasaogullari, L. Bonville, and T. Molter, J. Electrochem. Soc., 161, F1006 (2014).M. A. Uddin, X. Wang, J. Qi, M. O. Ozdemir, L. Bonville, U. Pasaogullari, and T. Molter, ECS Trans., 61(12), 49 (2014).M. A. Uddin, J. Qi, M. O. Ozdemir, L. Bonville, U. Pasaogullari, and T. Molter, ECS Trans., 61(12), 37 (2014). Figure 1