High-pressure Injection System Research Articles

Development of correlation model for cavitating spray using Eulerian simulations

Modern high-pressure injection systems for heavy-duty applications are prone to cavitation, which may have a detrimental effect on the system integrity. The present study aims to develop reliable correlations for Lagrangian engineering simulations to predict the onset of cavitation. Using the extensive data generated from the high-fidelity Eulerian volume-of-fluid (VOF) simulations of a single-hole injector for a wide range of operating conditions, a proper set of discharge ( Cd) and contraction ( Ca) coefficients are determined. In particular, four significant factors characterizing nozzle geometry are considered: the K factor, inlet curvature radius, nozzle exit radius, and channel length, as well as ambient and injection pressures. The results showed that a larger K factor and inlet curvature radius yielded higher Cd and Ca values, while the exit radius and channel length had a less significant impact on the cavitation dynamics. The smaller pressure difference between the nozzle inlet and exit mitigated the cavitation formation. These trends were well described using the mathematical regression model. Furthermore, two other correlation models based on the regression learner and artificial neural network methods were also developed. Of these three models, the mathematical regression model yielded the best agreement with an external validation dataset.

Study of the Optimization of Rail Pressure Characteristics in the High-Pressure Common Rail Injection System for Diesel Engines Based on the Response Surface Methodology

This paper establishes a mathematical model of the high-pressure common rail injection system used in diesel engines according to the parameters of its key components, and AMESim 2020 software was used to establish a simulation model of the common rail injection system used in diesel engines. The simulation model mainly includes a high-pressure oil pump model, a common rail pipe model, and a model of four injectors. This paper also describes an experimental analysis of the accuracy of the established simulation model. Through a simulation analysis of the system rail’s pressure fluctuation and pressure characteristics, it was concluded that the length of the common rail pipe, the diameter of the common rail pipe, and the inner diameter of the high-pressure fuel pipes are important influencing parameters for the rail pressure characteristics of the system. In this study, according to the original common rail pipe and high-pressure fuel pipe model, a response surface methodology was used to optimize and analyze the parameters of the common rail pipe and high-pressure fuel pipes, and the optimal size parameters for the common rail pipe and high-pressure fuel pipes were obtained with the minimum rail pressure fluctuations and the average rail pressure setpoint. After the optimization, the pressure for the common rail pipe of the high-pressure common rail system was increased by 0.82%, the pressure fluctuation was reduced by 21.66%, the injection pressure was increased by 1.15%, the single injection volume was increased by 0.86%, and its fuel injection characteristics were significantly improved.

A Pragmatic Approach to Update Support Studies and Human Reliability Analyses for a PSA Model

A probabilistic safety assessment (PSA) is used to estimate potential risks associated with a nuclear power plant. Event trees (ETs) and fault trees (FTs) describe accident scenarios following initiating events. They allow for identifying and quantifying the consequence frequencies. Based on success criteria, support studies are used to determine each scenario’s consequence. They are also used to define the time available for the operators to carry out the actions involved in the scenario, and consequently, the corresponding human failure probability. In this paper, we use a dynamic PSA toolbox to optimize support studies for a classical (ET/FT) PSA model. We analyze medium-break loss-of-coolant accident (LOCA) initiating events with the possible failure of the high-pressure safety injection (HPSI) system for an internal event Level 1 PSA for a pressurized water reactor plant. In order to prevent core uncovery and subsequent core damage, operators must depressurize the primary circuit to reach the low-pressure safety injection set point. This scenario represents a significant contribution to the core damage frequency. The dominant cut sets corresponding to this scenario involve HPSI failure to run over 24 h, while the thermal-hydraulic analysis supporting the human reliability assessment (HRA) analysis for this sequence assumes the unavailability of HPSI pumps at the beginning of the accident. We update the thermal-hydraulic assumptions in the support study by performing simulations for different values of the HPSI failure time. We find that even a short HPSI operation time buys significant (from the HRA point of view) available time for operators and drives significant improvement in estimating the human error probability (HEP). We postprocessed the minimal cut-set probability by integrating the obtained HEP. This result allows for more realistic quantification of the contribution of the medium-break LOCA in the core damage frequency.

Study of fuel spray characteristics using a high-pressure common rail diesel injection system by the method of Schlieren

The supercritical atmosphere created by the increase in temperature and pressure in the diesel engine cylinder is the key factor that causes changes in the fuel atomization process. In this study, the differences in spray morphology of n-heptane under different ambient temperature and pressure conditions were investigated using a constant volume combustion bomb combined with the Schlieren method. Based on the Peng-Robinson equation of state (PR equation), several transport characteristics models are constructed to predict the transport characteristics of n-heptane under different operating conditions. During the experiment, the injection pressure and fuel temperature were kept constant (80 MPa, 300 K), the ambient pressure was varied from 2 to 5 MPa, and the fuel temperature was changed from 400 to 800 K, spanning from subcritical to supercritical state. Three different spray regions have been identified based on the fuel temperature and spray geometry: liquid phase region, gas-liquid interface mixing layer, gas phase region. The results show that in a subcritical environment (400 K, 2 MPa), the fuel injection and atomization process is dominated by evaporation. The degree of heat exchange between the fuel and the medium gas is very low, while a small amount of phase change occurs. When the fuel is in low (600 K, 3 MPa) and medium supercritical (600 K, 4 MPa) ambient atmosphere, turbulence becomes the dominant factor in the fuel atomization process. The mixing layer at the gas-liquid interface at the edge of the liquid jet increases significantly. When the fuel is in a high supercritical (700 K, 4 MPa; 800 K, 5 MPa) atmosphere, the jet takes on a shape similar to that of a gas jet, and the mixing layer at the gas-liquid interface becomes the main part of the spray projection area.

Effect of Intake Conditions and Nozzle Geometry on Spray Characteristics of Group-Hole Nozzle

The group-hole nozzle concept is proposed to meet the requirement of nozzle hole minimization and reduce the negative impact of poor spatial spray distributions. However, there are limited researches on the effects of intake conditions and nozzle geometry on spray characteristics of the group-hole nozzle. Therefore, in this study, an accurate spray model coupled with the internal cavitating flow was established and computational fluid dynamics (CFD) simulations were done to study the effects of intake conditions and nozzle geometry on spray characteristics of the group-hole nozzle. Experimental data obtained using high-speed digital camera on the high-pressure common rail injection system was used to validate the numerical model. Effects of intake conditions (injection pressure and temperature) and nozzle geometry (orifice entrance curvature radius and nozzle length) on the flow and spray characteristics of the group-hole nozzle were studied numerically. The differences in Sauter mean diameter (SMD), penetration length and fuel evaporation mass between single-hole nozzle and group-hole nozzle under different nozzle geometry were also discussed. It was found that the atomization performance of the group-hole nozzle was better than that of the single-hole nozzle under same intake conditions, and the atomization effect of the short nozzle was better than that of the long nozzle. With increase in the orifice entrance curvature radius, the average velocity and turbulent kinetic energy of the fuel increased, which was conducive to improving the injection rate and flow coefficient of the nozzle. Meanwhile, the penetration length and SMD value rose, while evaporation mass dropped. When the ratio of the orifice entrance curvature radius (R) to the diameter of injection hole (D) was 0.12, the spray characteristics reached a constant state due to elimination of cavitation. Conclusions were made based on these. This study is expected to be a guide for the design of the group-hole nozzle.

Durability Study of a High-Pressure Common Rail Fuel Injection System Using Lubricity Additive-Dosed Gasoline-Like Fuel—Improved Endurance with Upgraded Hardware

Durability Study of a High-Pressure Common Rail Fuel Injection System Using Lubricity Additive-Dosed Gasoline-Like Fuel—Improved Endurance with Upgraded Hardware

The scaling effect analysis of counterpart test between LSTF and ATLAS IET facilities on 1% top head break LOCA

ATLAS B5.1 test is a 1% small break loss of coolant accident (SBLOCA) at the top of the reactor pressure vessel with a total failure of a high-pressure injection (HPI) system. It was conducted as a counterpart test of LSTF SB-PV-07. The LSTF is scaled from a three-loop pressurized water reactor (PWR) Westinghouse design, while the ATLAS facility is scaled from APR1400. Thus, to determine B5.1 test conditions, a scaling analysis has been conducted between the two test facilities of LSTF and ATLAS. We reviewed the scaling method used for the ATLAS facility and found the initial and boundary condition for the counterpart test. Then, we compared the experimental data of the ATLAS B5.1 test against that of LSTF SB-PV-07. To reduce the scaling distortion between two IET facilities, we modified the RELAP5 input of the ATLAS facility toward the LSTF facility considering the elevation difference and design difference. The internal design difference between the ALTAS and LSTF facilities generated a significant difference in the plant transient beyond the scaling distortion.

A Qualitative Strategy for Fusion of Physics into Empirical Models for Process Anomaly Detection

To facilitate the automated online monitoring of power plants, a systematic and qualitative strategy for anomaly detection is presented. This strategy is essential to provide credible reasoning on why and when an empirical versus hybrid (i.e., physics-supported) approach should be used and to determine the ideal mix of these two approaches for a defined anomaly detection scope. Empirical methods are usually based on pattern, statistical, and causal inference. Hybrid methods include the use of physics models to train and test data methods, reduce data dimensionality, reduce data-model complexity, augment data, and reduce empirical uncertainty; hybrid methods also include the use of data to tune physics models. The presented strategy is driven by key decision points related to data relevance, simple modeling feasibility, data inference, physics-modeling value, data dimensionality, physics knowledge, method of validation, performance, data availability, and suitability for training and testing, cause-effect, entropy inference, and model fitting. The strategy is demonstrated through a pilot use case for the application of anomaly detection to capture a valve packing leak at the high-pressure coolant injection system of a nuclear power plant.

Comparing Analysis of Loss of Coolant Accident on Bethsy Facility with Apros 6.05 and 6.06.

In this paper, the comparison of analysis of international standardized problem ISP 27 using two versions of APROS process simulation software 6.05 and 6.06 is presented. Numerical simulation of experiment Bethsy 9.1b, also known as ISP 27 was performed on a scaled down model of a three loop, 900 MWe Framatome PWR. In the test a small LOCA, with 2-inch cold leg break, combined with High pressure Injection System (HPIS) failure is simulated. State oriented approach, which requires operators to start an Ultimate Procedure were used. Model was first built in APROS 6.05 using standard modules in order to describe the volumes, heat structures and regulation of the test facility and was then exported to APROS 6.06. The results from both versions showed all the processes such as loop seal clearing, core uncover and rise of cladding temperature and other processes taking place in the experiment were in a good agreement with experimental data. However even though results were similar some differences were noticeable. The differences in core cladding temperature, time integrated break mass flow, core liquid level and pressurized pressure were analysed in more detail in this paper.

Effect of injector nozzle parameters on fuel consumption and soot emission of two-cylinder diesel engine for vehicle

In this paper, a bench test of a two-cylinder diesel engine with high-pressure common rail direct injection (CRDI) system for the external characteristics was carried out. The shape of combustion chamber was determined by comparing the fuel economy and soot emission of diesel engines. Based on this result, the effects of different nozzle parameters attempted at reducing brake specific fuel consumption (BSFC) and smoke were investigated. The experimental results show that the improved combustion chamber with a high central convex platform can significantly reduce BSFC and it has little impact on smoke. The appropriate decrease of the nozzle tip penetration (NTP) as well as increase of nozzle-hole diameter contribute to reducing fuel consumption and soot emission. The BSFC at the spray angle of 156° is reduced by 16% at the engine speed of 4000 r/min compared with that at the spray angle of 150°. Comparative results on fuel consumption and smoke emission at all engine speeds reveal that the injector with 153° spray angle, 1.8 mm NTP, 6 injection holes and 0.12 mm nozzle-hole diameter is a better choice of the two-cylinder diesel engine.

Understanding the collapse of flash-boiling sprays formed by multi-hole injectors operating at low injection pressures

Sprays consisting of initially separated plumes, which are generated by multi-hole injectors in strong flash-boiling conditions, may collapse and form a single spray cloud. It has been shown that for high-pressure injection systems (≥5 MPa), such behaviour is dependent on both the superheat and the geometrical configuration of the injector; while the spray collapse in low-pressure systems (≤1 MPa) is not yet understood. To the best of the author's knowledge, this is the first study aimed at filling this information gap. The principal novelty of this work is related to understanding the collapse in low-pressure systems, in terms of the different numbers of nozzles and the difference in the effects from flash boiling between low- and high-pressure sprays.The results showed that the flash-boiling sprays formed by the two- and six-hole injectors were substantially different, which is similar behaviour as for high-pressure sprays. The major difference from the sprays formed at high pressure is that the flash boiling does not result in an increased penetration (in relation to the subcooled conditions). This distinct behaviour was linked with a different jet break-up regime, and different droplet size reduction due to flash boiling, both depending on the injection pressure. This work discusses that the importance of the aerodynamic drag force due to a stronger droplet size reduction in the case of low-pressure sprays can be increased more than twofold compared to the high-pressure sprays.The lack of increased penetration leads to an important finding in terms of practical applications. In contrast to high-pressure systems, flash boiling will not lead to enhanced wall wetting regardless of the number of nozzles.This study has revealed that the interaction of the spray plumes is not sufficient to cause a strong spray collapse and the formation of the single jet-like spray structure. The necessary additional factor is the flow acceleration in the axis of the injector. The results highlighted the crucial role of the circular pattern, which already in subcooled cases led to the creation of flow conditions promoting axial propagation of a gaseous medium; while in the event of flash boiling, it prevented the surrounding air from entering the centre region of the spray cloud.

Analysis of the market structure of long-distance transport vehicles in the context of retrofitting diesel engines with modern dual-fuel systems.

The demands placed on vehicles are constantly increasing. European legislation has forced commercial vehicle manufacturers to develop ever more powerful and dynamic engines with low fuel consumption. With the appearance of exhaust gas standards, truck manufacturers realized that it was necessary to improve the fuel supply system so that the combustion process was more efficient. To achieve this the fuel injected into the cylinders had to be finer in order to mix more easily with air. High-pressure unit injection systems have proved to be a good and reliable solution. They are also relatively cheap to produce and less prone to fuel contamination. Many years and millions of failure-free kilometers traveled on unit injectors effectively distracted some users and producers from the Common Rail system. Exhaust gas standards and increasing consumer expectations forced manufacturers to take another step in their development, i.e. the need for more precise fuel injection control. The injectors had to run faster in order to carry out the initiation dose, the actual injection and the extra injection. All these modifications make diesel engines in commercial vehicles such as tractor units much more powerful. They also allow for cooperation with aftermarket dual-fuel CNG-ON and LPG-ON installations. Dual-fuel solutions are perhaps another step towards reducing emissions, and thanks to reduced tolls, they are becoming a real alternative to conventional fuel-powered tractor units. This work focuses on the structure of the truck tractor market in terms of selecting cars used for the use of a non-factory dual-fuel CNG-ON installation.

Sensitivity analysis of the IAEA SPE-2 small-break LOCA experiment with RELAP5, TRACE and APROS system codes

The Hungarian PMK-2 test facility is a scaled-down model of the VVER-440/213 type pressurized water reactors of Paks NPP, on which several measurement series have been carried out since the 80s. One of these series include four Standard Problem Exercises (SPE), primarily small-break loss-of coolant accident (SBLOCA) transients, performed in cooperation with IAEA. New RELAP5, TRACE and APROS models have already been developed and a comparative analysis of the results has been published recently for the PMK SPE-4 experiment. In that SBLOCA scenario, no high-pressure injection system (HPIS) was available, but a secondary side bleed and feed operation has been performed during the transient. This paper is a continuation of the previous one and presents the required model modifications and the analysis of the second SPE. The initiating event, similarly to the SPE-4 experiment, is a 7.4% break located at the top of the downcomer, while the main differences are that one line of the HPIS is available and no secondary side feed and bleed operation is performed in this case. One of the main objectives of the experiment was to verify that these safety measures are enough to prevent core dry-out. In addition to the investigation of this question, a sensitivity study was also carried out with respect to selected parameters that might have a significant impact on the characteristic of the simulated processes. The assessment of the results has also been performed with two quantitative methods, namely the Fast Fourier Transform Based Method with Signal Mirroring (FFTBM-SM) and Stochastic Approximation Ratio Based Method (SARBM).

Investigation of a method for online measurement of injection rate for a high-pressure common rail diesel engine injector under multiple-injection strategies

As a state-of-the-art injection technology, the high-pressure common rail injection system (HPCRIS) has advantages that include high injection pressure, adjustable injection timing and a flexible injection rate. Nevertheless, the fluctuation of cyclic fuel injection mass (CFIM) in the HPCRIS using a multiple-injection strategy (MIS) reduces the economy of the diesel engine and the stability of vibration and noise control. To realize the precise control of CFIM, the online perception of the injection process is the premise. This paper presents an innovative method for online measurement of injection rate under MIS conditions. According to the evolution characteristics of water hammer pressure oscillation in the fuel system, the rule is that the oscillation form of the water hammer is dependent on the structure of the HPCRIS rather than the injection conditions, and the general applicability of this rule is proved by the hydraulic–electric analog method. Based on this, the method for real-time simulation of the pilot water hammer oscillation wave in the same field is proposed to realize the extraction of the expansion pressure signal components of the main injection. Then, the direct mathematical relationship between the pressure signal and fuel injection rate is established, and the online measurement of fuel injection characteristics under MIS is realized. To improve the robustness of the algorithm a method for real-time calibration of fuel sound velocity is proposed. Finally, when compared with the offline experiment, this method for online measurement of injection rate has relatively high accuracy, the CFIM error is less than 2%, and the goodness of fit of the injection rate curve exceeded 0.91. This measurement method can provide direct feedback to the electronic control unit on the fuel injection system without changing the HPCRIS structure.

Experimental investigations into the effects of string cavitation on diesel nozzle internal flow and near field spray dynamics under different injection control strategies

On the test bench of the high-pressure common rail injection system with a high-speed camera, the visualization experiments of real-size tapered hole nozzle of the diesel engine were performed to obtain needle valve lift, string cavitation in the sac chamber and nozzle hole, residual bubbles and near-field spray characteristic. And a high-pressure sensor was utilized to measure the real pressure fluctuation for the nozzle inlet. On the basis, under different control strategies, the comprehensive effects of needle valve throttling and pressure fluctuation for nozzle inlet on the internal flow and near-field spray characteristic under the multiple injections were studied. Research indicated that the spray cone angle and the spray area ratio in the main injection stage shows a boot-shaped increasing trend of slowness and then abruptness. In the development stage, the spray cone angle fluctuates in a little range (20°-30°); In the saturation phase, the spray cone angle fully develops and the fluctuation is relatively stable (40°-50°). As the throttling position shifts, there is an obvious string cavitation process, and the spray cone angle increases suddenly. In the process of pre-injection and post-injection, needle valve and valve seat throttling and lift instability cause fuel pressure fluctuation in the control chamber and sac, which is the main immediate cause of the fluctuation of low fuel injection quantity. Besides, the interval time between multiple injections, on the one hand, affects the state of residual bubbles in the nozzle before the next injection beginning, on the other hand, it also affects the stability of the inlet pressure at this time. The flow transition in the low-lift zone and the cavitation changing in the high-lift stable zone also cause transformation in the form of pressure fluctuation.

Comparison in the effects of alumina, ceria and silica nanoparticle additives on the combustion and emission characteristics of a modern methanol-diesel dual-fuel CI engine

Methanol is widely used as a potential alternative source for diesel fuel and can reduce the CO, THC and smoke emissions of the CI engines. However, the lower cetane number and energy content of methanol hinder the high substitution of methanol over diesel fuel. Introducing nanoparticles as fuel-additive is an effective approach to cope with this issue. In the present work, the alumina, ceria and silica nanoparticles were separately mixed into methanol in mass proportions of 25, 50 and 100 ppm with the composite surfactant of sodium dodecyl benzene sulfonate and cetyl trimethyl ammonium bromide (1:1 mass fraction) to create the nanofluid. The nanofluid was then injected into the intake port to combust synergistically with the mineral diesel fuel injected by the other high-pressure injection system, generating the nanoparticle-assisted methanol-diesel fuel mode (NMF). The characteristics of combustion and pollutant emission of NMFs were investigated with 10%, 30% and 50% methanol substituted level (M10, M30 and M50, respectively), at 10–90% engine loads of a constant engine speed. The results showed that the substitution of methanol led to an extension in the ignition delay but a shortening of combustion duration than diesel fuel. The additional introduction of alumina and ceria nanoparticles in each dosage, and silica nanoparticles in 100 ppm dosage, into M10 slightly shortened the ignition delay at 10% load conditions. When dosed into M50 fuel, all the three nanoparticles in various dosages led to shortened ignition delay at 10–50% engine loads. Over the test conditions, the addition of nanoparticles all caused a distinct increase in the peak in-cylinder pressure for the methanol-diesel dual-fuel mode. However, the addition of nanoparticles exerted marginal influences on further reduction of CO, HC and smoke emissions, and even further elevated the NOx emissions for MDF mode by up to 40%. Moreover, the deterioration degrees of NOx emissions for alumina and ceria nanoparticle addition were higher than the silica nanoparticles, and elevated towards the higher nanoparticle dosage and lower engine load.

Validation of a three-phase Eulerian CFD model to account for cavitation and spray atomization phenomena

Cavitation phase change phenomenon appears in many engineering applications, often eroding and damaging surfaces, so deteriorating the performance of devices. Therefore, it is a phenomenon of great interest for the research and industry communities. In this work, three different cavitation models, the Homogeneous Relaxation Model (HRM), the Schnerr and Sauer, and the Kunz, are implemented in a Eulerian multiphase homogeneous flow Computational Fluid Dynamics (CFD) solver previously developed for simulating fully atomized sprays. The improved solver can be used then to study not only cases with cavitation, such a hydrofoil, but also situations where cavitation occurs together with liquid atomization, such as high pressure injection systems. Validation of this solver is carried out for three different cases under diverse operating conditions: a two-dimmensional throttle, a hydrofoil and a single-hole fuel injector. The Reynolds-Averaged Navier-Stokes (RANS) approach is employed for taking into account the turbulence effects. Simulation results are compared to experimental data available in the literature. Among the tested cavitation models, the HRM is the one that provides the best accuracy in the three validation cases. Nevertheless, the onset of cavitation and the area occupied by the vapor cavities are always underpredicted, by all cavitation models in all validation cases. This can be associated to the unsteady and turbulent nature of the cavitation phenomenon. Even so, the computational prediction of several parameters, such as mass flow rate through the nozzles or spray spreading angle, has an error below 5-10%, which proves the capabilities of the solver.

Effect of ultrasonic nanocrystal surface modification on wear mechanisms of thermally-sprayed WC-Co coating

High-pressure common rail injection systems lubricated with low-lubricity fuel may be made more resistant to wear and scuffing with robust coatings. In this study, a WC-Co coating was deposited onto heat-treated SAE 52100 steel substrates using a thermal spray method. The coated substrates were then treated using an ultrasonic nanocrystal surface modification (UNSM). Wear performance of the coating was evaluated by ball-on-disk tribometer lubricated with three different fuels against three different materials. Besides, the changes in surface roughness, hardness, microstructural evolution and critical load resulting from UNSM were systematically investigated. The UNSM controlled the surface roughness and hardness due to the grain size refinement, surface integrity and pore reduction. The application of UNSM exhibited higher wear resistance than the as-sprayed coating. Wear mechanisms were investigated based on the results of surface characterizations, where the abrasion and oxidative wear modes took place.

Stability Analysis upon High-Pressure Common Rail Fuel Injection System under Multiple Injection Modes

Fuel injection stability of high-pressure common rail fuel injection system (HPCRFIS) under multiple injection modes is a recognized technical problem. To explain it essentially, a numerical model based on bond graph method, which provides a standardized series of symbol system to describe various components in different physical fields as well as interactive effect analysis tool for different energy categories, was used to investigate the problem. As HPCRFIS is a typical nonlinear system with multi-physical coupling, it is very difficult to analyze system stability directly. Therefore, the system was linearized at typical moments. The system matrix for each typical moment was obtained thereby. To investigate the influential mechanism of system stability deeply, the variations of rank and eigenvalues distributions of state matrices were analyzed. The results show that the rank of state matrices changes abruptly when the needle or control valve moves. In terms of system stability, the oscillation characteristics are subject to the movement of needle or control valve. The ending of the former injection causes the system to show damping oscillation characteristics before the latter injection starts. The motion of control valve makes more contribution to system stability than that of needle, which could be concluded by Lyapunov stability criterion.

Major Outcomes through Recent ROSA/LSTF Experiments and Future Plans

Many experiments have been conducted on accidents and transients of pressurized water reactor (PWR) employing the rig of safety assessment/large-scale test facility (ROSA/LSTF). Recent research activities concerned with the OECD/NEA international joint projects included experimental investigation via the ROSA and ROSA-2 Projects, and counterpart testing with thermal-hydraulic integral test facilities under collaboration of the PKL-2, PKL-3, ATLAS, and ATLAS-2 Projects. Major results of the related integral effect tests (IETs) with the LSTF were reviewed to experimentally identify thermal-hydraulic phenomena involved, regarding the PWR accident sequences in accordance with the new regulatory requirements for the Japanese light-water nuclear power plants. Future separate effect test using the LSTF is planned to simulate loss of emergency core cooling system (ECCS) recirculation functions in a large-break loss-of-coolant accident (LOCA). Key results of the recent IETs utilizing the LSTF and future plans were presented relevant to multiple steam generator tube rupture accident with recovery operation, small-break LOCA with accident management measure on core exit temperature reliability, and small-break LOCA with thermal stratification under cold water injection from ECCS into cold legs. Also, main outcomes of the LSTF IETs were indicated for wide spectrum LOCA with core uncovery and anticipated transient without scram following small-break LOCA under totally failed high-pressure injection system.