The Impact of RELAP5 Pipe Break Flow Rates Associated With Reverse Flow Limiter Removal for Steam Generator Replacement

2006 ◽  
Author(s):  
Dong Zheng ◽  
Julie M. Jarvis ◽  
Allen T. Vieira
Keyword(s):  
Steam Generator ◽  
Reverse Flow ◽  
The United States ◽  
Operating Conditions ◽  
Hazard Evaluation ◽  
Flow Rates ◽  
Choked Flow ◽  
Pipe Break ◽  
The Impact ◽  
Generator Replacement

Pipe break flow rates are calculated for a main feedwater line break (FWLB) in the main steam valve vault (MSVV) for a PWR Steam Generator Replacement (SGR). A reverse flow limiter is installed in the original steam generator (OSG) feedwater nozzle to limit the blowdown flowrate in the event of a postulated FWLB. This feature is not incorporated in the replacement steam generator (RSG) design. The change in RSG nozzle design in conjunction with new operating conditions results in increased FWLB mass and energy releases which can impact environmental temperatures and pressures and flooding levels. In the United States, benchmarking for safety related analyses is necessary in consideration of 10CFR50.59 requirements. RELAP5/MOD3 is used to model the pipe break flowrates for a FWLB at different break locations. The benchmark FWLB blowdown releases are larger than the OSG design basis blowdown releases due to differences in RELAP5/MOD3 versions which are found to have different algorithms for subcooled choked flow. The SGR FWLB blowdown release rates are determined to have minimal impact on the compartment temperature and pressure response. However, the flooding levels and associated equipment qualification are potentially impacted. Modeling techniques used to minimize the impact of the SGR blowdown releases on MSVV flooding levels include modeling flashing effects, more realistic RSG temperature distribution, inventory depletion and Auxiliary Feedwater (AFW) flow initiation time, and considering loss of offsite power scenarios. A detailed flooding hazard evaluation is needed, which considers the actual main feedwater isolation times to ensure that environmentally qualified safety related components, required to mitigate the effects of a FWLB inside the MSVV, can perform their safety function prior to being submerged.

An Impact of Various Shroud Bleed Slot Configurations and Cavity Vanes on Compressor Map Width and the Inducer Flow Field

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Subenuka Sivagnanasundaram ◽  
Stephen Spence ◽  
Juliana Early ◽  
Bahram Nikpour
Keyword(s):  
Flow Field ◽  
Incidence Angle ◽  
Pressure Ratio ◽  
Leading Edge ◽  
Operating Conditions ◽  
Choked Flow ◽  
Recirculating Flow ◽  
Heavy Duty Diesel ◽  
Compressor Map ◽  
The Impact

This paper describes an investigation of map width enhancement and a detailed analysis of the inducer flow field due to various bleed slot configurations and vanes in the annular cavity of a turbocharger centrifugal compressor. The compressor under investigation is used in a turbocharger application for a heavy duty diesel engine of approximately 400 hp. This investigation has been undertaken using a computational fluid dynamics (CFD) model of the full compressor stage, which includes a manual multiblock-structured grid generation method. The influence of the bleed slot flow on the inducer flow field at a range of operating conditions has been analyzed, highlighting the improvement in surge and choked flow capability. The impact of the bleed slot geometry variations and the inclusion of cavity vanes on the inlet incidence angle have been studied in detail by considering the swirl component introduced at the leading edge by the recirculating flow through the slot. Further, the overall stage efficiency and the nonuniform flow field at the inducer inlet have been also analyzed. The analysis revealed that increasing the slot width has increased the map width by about 17%. However, it has a small impact on the efficiency, due to the frictional and mixing losses. Moreover, adding vanes in the cavity improved the pressure ratio and compressor performance noticeably. A detail analysis of the compressor with cavity vanes has also been presented.

An Impact of Various Shroud Bleed Slot Configurations and Cavity Vanes on Compressor Map Width and the Inducer Flow Field

2011 ◽  
Author(s):  
Subenuka Sivagnanasundaram ◽  
Stephen Spence ◽  
Juliana Early ◽  
Bahram Nikpour
Keyword(s):  
Flow Field ◽  
Incidence Angle ◽  
Pressure Ratio ◽  
Leading Edge ◽  
Operating Conditions ◽  
Choked Flow ◽  
Recirculating Flow ◽  
Heavy Duty Diesel ◽  
Compressor Map ◽  
The Impact

This paper describes an investigation of map width enhancement and a detailed analysis of the inducer flow field due to various bleed slot configurations and vanes in the annular cavity of a turbocharger centrifugal compressor. The compressor under investigation is used in a turbocharger application for a heavy duty diesel engine of approximately 400hp. This investigation has been undertaken using a CFD model of the full compressor stage which includes a manual multi-block structured grid generation method. The influence of the bleed slot flow on the inducer flow field at a range of operating conditions has been analysed, highlighting the improvement in surge and choked flow capability. The impact of the bleed slot geometry variations and the inclusion of cavity vanes on the inlet incidence angle have been studied in detail by considering the swirl component introduced at the leading edge by the recirculating flow through the slot. Further, the overall stage efficiency and the non-uniform flow field at the inducer inlet have been also analysed. The analysis revealed that increasing the slot width has increased the map width by about 17%. However, it has a small impact on the efficiency due to the frictional and mixing losses. Moreover, adding vanes in the cavity improved the pressure ratio and compressor performance noticeably. A detail analysis of the compressor with cavity vanes has also been presented.

Wear Scar Progression of Impact-Fretting at Elevated Temperature for Steam Generator Tubes in Nuclear Power Plants

2006 ◽  
Vol 326-328 ◽  
pp. 1251-1254 ◽  
Author(s):  
Chi Yong Park ◽  
Jeong Keun Lee
Keyword(s):  
Steam Generator ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Operating Conditions ◽  
Wear Scar ◽  
Fretting Wear ◽  
Test Material ◽  
The Impact ◽  
Steam Generator Tubes

Fretting wear generated by flow induced vibration is one of the important degradation mechanisms of steam generator tubes in the nuclear power plants. Understanding of tube wear characteristics is very important to keep the integrity of the steam generator tubes to secure the safety of the nuclear power plants. Experimental examination has been performed for the purpose of investigating the impact fretting. Test material is alloy 690 tube and 409 stainless steel tube supports. From the results of experiments, wear scar progression is investigated in the case of impact-fretting wear test of steam generator tubes under plant operating conditions such as pressure of 15MPa, high temperature of 290C and low dissolved oxygen. Hammer imprint that is actual damaged wear pattern, has been observed on the worn surface. From investigation of wear scar pattern, wear mechanism was initially the delamination wear due to cracking the hard oxide film and finally transferred to the stable impact-fretting pattern.

Crack Initiation Factor by Impact Fretting Wear at INCONEL Alloy for Steam Generator Tube in Nuclear Power Plants

2007 ◽  
Vol 26-28 ◽  
pp. 1269-1272
Author(s):  
Chi Yong Park ◽  
Jeong Kun Kim ◽  
Tae Ryong Kim ◽  
Sun Young Cho ◽  
Hyun Ik Jeon
Keyword(s):  
Steam Generator ◽  
Wear Mechanism ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Operating Conditions ◽  
Fretting Wear ◽  
Steam Generator Tube ◽  
Inconel Alloy ◽  
The Impact

Inconel alloy such as alloy 600 and alloy 690 is widely used as the steam generator tube materials in the nuclear power plants. The impact fretting wear tests were performed to investigate wear mechanism between tube alloy and 409 stainless steel tube support plates in the simulated steam generator operating conditions, pressure of 15MPa, high temperature water of 290°C and low dissolved oxygen(<10 ppb). From investigation of wear test specimens by the SEM and EDS analysis, hammer imprint, which is known to be an actual damaged wear pattern, has been observed on the worn surface, and fretting wear mechanism was investigated. Wear progression of impact-fretting wear also has been examined. It was observed that titanium rich phase contributes to the formation of voids and cracks in sub-layer of fretting wear damage by impact fretting wear.

Aerodynamic Performance of Turbine Center Frames With Purge Flows—Part II: The Influence of Individual Hub and Tip Purge Flows

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Stefan Zerobin ◽  
Christian Aldrian ◽  
Andreas Peters ◽  
Franz Heitmeir ◽  
Emil Göttlich
Keyword(s):  
High Pressure ◽  
Operating Conditions ◽  
High Pressure Turbine ◽  
Flow Rates ◽  
Purge Flow ◽  
Flow Evolution ◽  
Generation Mechanisms ◽  
The Impact ◽  
First Time ◽  
Time Assessment

The aerodynamic behavior of turbine center frame (TCF) ducts under the presence of high-pressure turbine (HPT) purge flows was experimentally investigated in this two-part paper. While the first part of the paper demonstrated the impact of varying the purge flow rates (PFR) on the loss behavior of two different TCF designs, the second part concentrates on the influence of individual hub and tip purge flows on the main flow evolution and loss generation mechanisms through the TCF ducts. Therefore, measurements were conducted at six different operating conditions in a one and a half stage turbine test setup, featuring four individual purge flows injected through the hub and tip, forward and aft cavities of the HPT rotor. The outcomes of this first-time assessment indicate that a HPT purge flow reduction generally benefits TCF performance. Decreasing one of the rotor case PFRs leads to an improved duct pressure loss. The purge flows from the rotor aft hub and tip cavities are demonstrated to play a particularly important role for improving the duct aerodynamic behavior. In contrast, the forward rotor hub purge flow actually stabilizes the flow in the TCF duct and reducing this purge flow can penalize TCF performance. These particular HPT/TCF interactions should be taken into account whenever high-pressure turbine purge flow reductions are pursued.

scholarly journals Experimental and Numerical Assessment of the Impact of an Integrated Active Pre-Swirl Generator on Turbocharger Compressor Performance and Operating Range

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3537
Author(s):  
Charles Stuart ◽  
Stephen Spence ◽  
Sönke Teichel ◽  
Andre Starke
Keyword(s):  
Mass Flow ◽  
Operating Conditions ◽  
Centrifugal Impeller ◽  
Boost Pressure ◽  
Flow Rates ◽  
Operating Range ◽  
Surge Margin ◽  
Mass Flow Rates ◽  
Low Mass ◽  
The Impact

The implementation of increasingly stringent emissions and efficiency targets has seen engine downsizing and other complementary technologies increase in prevalence throughout the automotive sector. In order to facilitate ongoing improvements associated with the use of these strategies, delivering enhancements to the performance and stability of the turbocharger compressor when operating at low mass flow rates is of paramount importance. In spite of this, a few concepts (either active or passive) targeting such aims have successfully transitioned into use in automotive turbochargers, due primarily to the requirement for a very wide compressor-operating range. In order to overcome the operational limitations associated with existing pre-swirl generation devices such as inlet guide vanes, this study developed a concept comprising of an electrically driven axial fan mounted upstream of a standard automotive turbocharger centrifugal compressor. Rather than targeting a direct contribution to compressor boost pressure, the fan was designed to act as a variable pre-swirl generation device capable of being operated completely independently of the centrifugal impeller. It was envisioned that this architecture would allow efficient generation of the large pre-swirl angles needed for compressor surge margin extension and efficiency enhancement at low mass flow rate-operating points, while also facilitating the delivery of zero pre-swirl at higher mass flow rates to ensure no detrimental impact on performance at the rated power point of the engine. Having progressed through 1-D and 3-D aerodynamic modelling phases to understand the potential of the system, detailed component design and hardware manufacture were completed to enable an extensive experimental test campaign to be conducted. The experimental results were scrutinized to validate the numerical findings and to test the surge margin extension potential of the device. Compressor efficiency improvements of up to 3.0% pts were witnessed at the target-operating conditions.

Effects of Sand Ingestion Through an Axial Fan With Blade Staggering

2008 ◽  
Author(s):  
Adel Ghenaiet
Keyword(s):  
High Speed ◽  
Air Flow ◽  
Operating Conditions ◽  
Sand Particle ◽  
Computational Domain ◽  
Axial Fan ◽  
Complex Flow ◽  
Particle Trajectories ◽  
Flow Rates ◽  
The Impact

This paper presents the numerical results of sand particle trajectories and erosion patterns in a single stage axial fan used in industrial air ventilation, and the subsequent deterioration of the blade geometry. Attention is focused in particular on the effects of rotor blade staggering and the operating flow rates. By adopting the Lagrangian formulation to study the dynamics of particulate air-flow, the flow-field within the blade passage is solved separately. Particle trajectories computation is based on a stochastic tracking algorithm, which includes eddy-lifetime concept for turbulence, and accounts for the complex flow patterns near walls, random particle rebound factors, in addition to particle size, shape and fragmentation. The equations of motion are solved in a stepwise manner, whereas, particle tracking in different cells of the computational domain is based on the finite element method. The computation of the particle trajectories yields the impact locations along the blade surfaces, where the corresponding erosion patterns are calculated by using experimental correlations. The results of the numerical simulations carried out at low and high concentrations of MIL-E5007E sand particles, for different fan blade staggering and mass flow rates, revealed that the main impacted areas are found along the blade leading edge, over a strip of the blade suction side and a large area of the pressure side, in addition to the tip and casing, but with rare impacts on the hub. The rates of erosion in this axial fan are found to depend strongly on the air flow condition and the blade staggering. In all operating conditions of this axial fan, the rates of erosion are lower in comparison to high speed fans and compressors. Erosion analysis could be used in aerodynamic and mechanical design procedures to produce turbomachinery blading that would be less susceptible to erosion.

Tax changes could drive Greek shipowners abroad

2017 ◽  
Keyword(s):  
Economic Crisis ◽  
Capital Controls ◽  
The United States ◽  
Balance Of Payments ◽  
Operating Conditions ◽  
Shipping Industry ◽  
Economic Uncertainty ◽  
Content Type ◽  
Tax Changes ◽  
The Impact

Subject The impact of Greece's economic crisis on its shipping industry. Significance The Greek-flagged and Greek-owned fleet represents approximately half the total EU fleet in terms of tonnage. Despite the domestic economic crisis and challenging global operating conditions, Greek ship owners have succeeded in increasing their fleet capacity throughout this period. However, shipping's contribution to the economy and balance of payments is dwindling because of protracted economic uncertainty, the imposition of capital controls in 2015 and more recently the threat of additional taxation. Impacts A shift towards protectionism in the United States and Europe may undermine global shipping by curtailing the intercontinental goods trade. China's greater emphasis on trade in services will intensify the search for new markets with higher export growth. A culture of small family-held shipping businesses will set a benchmark for the Greek SME sector.

An Investigation of Compressor Map Width Enhancement and the Inducer Flow Field Using Various Configurations of Shroud Bleed Slot

2010 ◽  
Author(s):  
Subenuka Sivagnanasundaram ◽  
Stephen Spence ◽  
Juliana Early ◽  
Bahram Nikpour
Keyword(s):  
Flow Field ◽  
Incidence Angle ◽  
Leading Edge ◽  
Detailed Comparison ◽  
Operating Conditions ◽  
Tip Vortex ◽  
Performance Measurements ◽  
Impeller Blade ◽  
Choked Flow ◽  
The Impact

This paper describes an investigation of various shroud bleed slot configurations of a centrifugal compressor using CFD with a manual multi-block structured grid generation method. The compressor under investigation is used in a turbocharger application for a heavy duty diesel engine of approximately 400hp. The baseline numerical model has been developed and validated against experimental performance measurements. The influence of the bleed slot flow field on a range of operating conditions between surge and choke has been analysed in detail. The impact of the returning bleed flow on the incidence at the impeller blade leading edge due to its mixing with the main through-flow has also been studied. From the baseline geometry, a number of modifications to the bleed slot width have been proposed, and a detailed comparison of the flow characteristics performed. The impact of slot variations on the inlet incidence angle has been investigated, highlighting the improvement in surge and choked flow capability. Along with this, the influence of the bleed slot on stabilizing the blade passage flow by the suction of the tip and over-tip vortex flow by the slot has been considered near surge.

Asymmetry Investigation on Single Phase Flow in Inverted U-Tubes of Steam Generator Under the Condition of Natural Circulation

2010 ◽  
Author(s):  
Chuan Wang ◽  
Lei Yu
Keyword(s):  
Experimental Data ◽  
Pressure Drop ◽  
Steam Generator ◽  
Mass Flux ◽  
Single Phase ◽  
Reverse Flow ◽  
Natural Circulation ◽  
Flow Characteristics ◽  
Operating Conditions ◽  
Outlet Temperature

In order to study the reverse flow characteristics in U-tubes of steam generator in the natural circulation case, the code RELAP5/MOD3.3 is used to model and calculate single-phase water flow for PWR under some typical operating conditions in the natural circulation case. The U-tubes of steam generator are classified according to their length and then are divided into different nodes and flow lines. The calculated results show that reverse flow exists in some inverted U-tubes of the steam generator, the natural circulation capacity of the primary coolant circuit system declines and the calculated net mass flux of the natural circulation accords with the experimental data. The traditional lumped parameter method can not simulate the reverse flow characteristics in inverted U-tubes and its result is much greater than the experimental data. When the steam generator outlet pressure is higher than inlet pressure, and gravitational pressure drop is lower than the total of frictional pressure drop and area change pressure drop, the reverse flow will occur. As to the nuclear power plant described in this paper, the mass flux of the shorter U-tubes drops more quickly and at last reverse flow will occur. The temperature distribution is uniform in inverted U-tubes, and it is almost identical with that of SG in secondary side. The occurrence of reverse flow can be judged by that whether the steam generator inlet temperature is lower than reactor outlet temperature obviously. It is indicated that reverse flow occurred in the U-tubes of the steam generator reduces the mass flux in the natural circulation system.

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