Nozzle Loads Research Articles

A generative adversarial network for enhancing over-expansion flow field perception of nozzles with large expansion ratio

Over-expansion flow and separation phenomena exist inside the nozzle during the startup and shutdown of the rocket engine, and the transition between the separation modes is prone to cause significant side loads and jeopardize the safety of the engine. Accurate, comprehensive and prompt nozzle flow field state perception is of great significance to the stable operation of the engine. Here, a generative adversarial network is proposed to reconstruct the internal Mach number and temperature fields for different nozzle pressure ratios and flow separation modes based on the discrete pressure at the nozzle wall. The proposed generative adversarial network employs Wasserstein distance and gradient penalty to improve the problems of gradient vanishing and pattern collapse during discriminator network training. The large expansion ratio nozzle selected was the VOLVO S1 nozzle and numerical simulations were carried out under different nozzle pressure ratio conditions to obtain data for the training of data-driven model. The results indicate that generative adversarial networks can accurately reconstruct restricted shock separation and free shock separation modes under different nozzle pressure ratios based on discrete pressure and temperature measurement points on the nozzle wall, with a relative error of less than 1.2%, and accurately identify important flow field characteristics such as Mach disk, supersonic jet flow, and multiple recirculation regions. The advantages of the generative model in recognizing the strong normal shock Mach disk are compared with those of the supervised learning model. This study lays the foundation for the subsequent study of nozzle side load and structural fatigue life based on three-dimensional flow field.

Theoretical and Finite Element Analysis of Pressure Vessel

Objectives: This study tests the vessel strength and performance of pressure vessel under Internal pressure, Nozzle loads, and Hydro-test using Ansys APDL, validating design alignment with ASME Section VIII following the Design by rule (Analytical) and Design by Analysis (FEA) accurate elastic analysis approach. Methods: This study employs ASME methods to validate vessel integrity under various loads. Strength is confirmed through analytical formulas and Finite Element Analysis (FEA) using ANSYS APDL, aligned with widely used ASME BPVC codes in the oil and gas industry. The FE model, utilizing hex elements, ensures result accuracy with a minimum of three elements across thickness. Boundary conditions are validated by comparing hoop stress in FEA with analytically calculated values. ASME's computationally efficient elastic analysis, employing a linear approach, includes stress linearization at discontinuity and non-discontinuity locations, verifying vessel design through analysis. Findings: Initial thicknesses for the shell and cone exceeded analytically calculated minimums, affirming vessel structural integrity through ASME's design by rule approach. Finite Element Analysis (FEA) stress analysis at critical points, such as nozzle junctions and other discontinuity areas, validates accuracy through hoop stress checks. Analysis of design and test load cases reveals stress categories well within ASME Sec VIII limits, confirming the vessel's safety and compliance with elastic stress analysis standards. Novelty: This method emerges as a reliable tool for vessel design, ensuring safety and ASME compliance, particularly beneficial for industries like oil and gas. It provides precise guidelines utilizing hex mesh, validates boundary conditions through hoop stress comparison, and comprehensively assesses stress in critical and non-critical zones through elastic stress analysis. Addressing common challenges identified in the literature review, this approach enhances the accuracy and reliability of pressure vessel designs in compliance with ASME standards for design and test loadings. Keywords: Pressure Vessels, Process Industries, Stress, Loads, Pressure, Thermal, Design Validation, ASME, FE analysis

Horizontal tank strength analysis considering nozzle loads and horizontal deviations

When assessing the reliable and safe operation of technological equipment, and in particular, capacitive-type equipment, a fairly diverse number of methods are used. However, all current procedures do not sufficiently take into account the impact of certain factors on the forming stressed-deformed state of the object. Usually, when assessing the actual technical condition of an object, the level of defect of the object is determined, and appropriate calculations are carried out according to the criterion of the dominant damage mechanism. A significant impact on the stressed-deformed state of the shell structure can be exerted by the level of loads on process nozzles from the connection of process pipelines, as well as possible deviations during installation work. One of these deviations may be a deviation from the horizontal of the housing when installing supports on the foundation. Moreover, the combination of the action of the above factors can have a determining negative effect on the strength, and, accordingly, the operational reliability of the technical device. In the modern world, technological progress does not stand still and the consequence of this is the development of a fairly extensive number of software products that allow you to simulate possible individual scenarios for the development of unfavorable processes and predict the behavior of the object under the conditions under consideration. In this work, studies are carried out on the strength analysis of the horizontal tank, taking into account various values of loads on the nozzle of the body diameter, as well as taking into account the deviation of the tank body from horizontal.

Operating Experience of Snubbers in Indian Pressurized Heavy Water Reactors

In a Nuclear Power Plant (NPP), the piping layout needs to have flexibility to reduce the operating stresses and nozzle loads due to thermal expansion. At the same time, the piping and equipment need to be supported adequately to sustain the dynamic loads viz., seismic loads, sudden opening/closing of valves etc. In Indian Pressurized Heavy Water Reactors (PHWRs), Snubbers are provided on nuclear equipment & piping to serve both purposes i.e. allow flexibility for thermal movement during operation and at the same provide requisite rigidity to take care of dynamic loads. Snubbers are subjected to harsh environment during operation including high temperature, radiation, vibration and corrosive condition, which may adversely affect its performance. Various degradations viz., high drag force, shift in dynamic characteristics (locking characteristic), jamming etc. have been observed. Periodic testing of Snubbers is required to ensure the proper functioning during normal operating condition as well as during dynamic event. A dedicated In-Service Inspection (ISI) program for snubbers exists in Indian PHWRs to ensure healthiness/functionality of Snubbers. Efforts have been made to reduce numbers of Snubbers progressively in PHWR units. Numbers of snubbers have been significantly reduced in latest 700MWe PHWR Design. This paper covers the various degradations observed in snubbers, ISI program for snubbers, design modifications, Snubber testing, assessment for fitness for service, replacement of Snubbers in older units and optimization of snubbers.

Corrosion Prediction and Case Study of Plate Heat Exchangers Based on Artificial Intelligence

Corrosion can cause downtime, equipment damage, and safety hazards. To address this challenge, researchers are turning to artificial intelligence (AI) to predict corrosion events of heat exchangers Shell and tube heat exchanger is an important equipment in nuclear power, chemical industry and other industries. The working conditions of such equipment are often complex, and many nozzles on the cylinder and head are connected with pipes or various instruments. In this paper, the local stress analysis is carried out for the nozzle of the container by using the finite element analysis method, the distribution of stress intensity at the nozzle is obtained, and the safety of the nozzle area of the container under the specific nozzle load is verified.

Determination of mixed-mode stress intensity factors for axial crotch corner cracks at cylindrical vessel to nozzle intersections under internal pressure and nozzle loads

In this study, Stress Intensity Factors (SIF) of quarter circle and semi elliptic cracks at the crotch corner of the intersection between a cylindrical pressure vessel and a radial nozzle have been computed for combinations of the actions of internal pressure and external forces on the nozzle. Until now, practitioners have used simplified solutions for SIFs available from the literature, such as the Newman-Raju equations for the mode I SIF produced by an internal longitudinal semi-elliptical crack in a cylinder, to approximate the SIF produced at a crotch corner crack. These equations do not take into account the effect of the opening of the cylinder for the nozzle and the resulting stress distribution along the cylinder. As a result, there is uncertainty about the validity of using these simplified solutions in engineering critical assessments and a more exact determination of the SIFs for crotch corner cracks would be beneficial.The mode I, II and III stress intensity factors have been determined for crotch corner cracks for a single size of vessel and are presented as a function of variables such as location on the crack front, crack size and aspect ratio (a/c), crack angle with respect to the axis of the vessel, and the magnitude of internal pressure and external forces. The results are presented in graphical form. The study concludes with the recommendation that the analysis be extended to a wider range of vessel and nozzle parameters.

Considerations Pertaining to Exerted Piping Loads on Pressure Vessel Nozzles

This technical note is intended to make the engineer involved in the design of pressure vessels with connected piping aware of the possible options that yield the most advantageous design from an economic perspective. Pressure vessels are connected to external piping by a nozzle welded to the vessel wall and a flange connection. Due to expansion or contraction of the piping system connected to the pressure vessel, which is caused by the difference in installation and operating temperatures, the piping system exerts forces and moments on the nozzle of the pressure vessel. This means that nozzle loads therefore impose an important constraint in the design of pressure equipment. It is important that such loads do not overstress the vessel-nozzle intersection. This technical note is limited to the interface of the pressure vessel piping system's imposed external loads.

Parametric investigation of an injection-jet self-powered Fontan circulation

Approximately 1/2500 babies are born with only one functioning ventricle and the Fontan is the third and, ideally final staged palliative operation for these patients. This altered circulation is prone to failure with survival rates below 50% into adulthood. Chronically elevated inferior vena cava (IVC) pressure is implicated as one cause of the mortality and morbidity in this population. An injection jet shunt (IJS) drawing blood-flow directly from the aortic arch to significantly lower IVC pressure is proposed. A computer-generated 3D model of a 2–4 year old patient with a fenestrated Fontan and a cardiac output of 2.3 L/min was generated. The detailed 3D pulsatile hemodynamics are resolved in a zero-dimensional lumped parameter network tightly-coupled to a 3D computational fluid dynamics model accounting for non-Newtonian blood rheology and resolving turbulence using large eddy simulation. IVC pressure and systemic oxygen saturation were tracked for various IJS-assisted Fontan configurations, altering design parameters such as shunt and fenestration diameters and locations. A baseline “failing” Fontan with a 4 mm fenestration was tuned to have an elevated IVC pressure (+ 17.8 mmHg). Enlargement of the fenestration to 8 mm resulted in a 3 mmHg IVC pressure drop but an unacceptable reduction in systemic oxygen saturation below 80%. Addition of an IJS with a 2 mm nozzle and minor volume load to the ventricle improved the IVC pressure drop to 3.2 mmHg while increasing systemic oxygen saturation above 80%. The salutary effects of the IJS to effectively lower IVC pressure while retaining acceptable levels of oxygen saturation are successfully demonstrated.

Assessment of Coupled Effect of Steam Pipes on Seismic Analysis of Reactor Coolant System

Reactor coolant system is connected with auxiliary pipes, surge pipes and steam pipes. In order to facilitate the dynamic analysis of reactor coolant system, it is necessary to decouple the pipes connected with the reactor coolant system. Although some international standards stipulating requirements for the decoupling of subsystems from the main system, in order to further explore the influence of decoupling steam pipes, the seismic response of reactor coolant system with or without steam pipes is simulated by using ANSYS program. Firstly, the modal analysis of reactor coolant system is carried out to analysis the influence of steam pipes on the resonant frequency of reactor system. Then, the standardized seismic dynamic analysis of reactor system with or without steam pipes is carried out. The nozzle load (inlet and outlet nozzle load of main device, such as reactor pressure vessel, steam generator, pump) and support load (of main device such as reactor pressure vessel, steam generator, pump) are output and compared. According to nozzle load and support load, it can be seen that the steam pipes have little influence on the seismic analysis of reactor coolant system, i.e. steam pipes can be decoupled in the seismic analysis of reactor coolant system.

Pipe Stress and Turbine Nozzle Load Analysis for HP Steam Inlet and MP Steam Extraction on Turbine Generator 51G201T Capacity 10MW

Thermal pipe expansion on the turbine greatly affects the performance of the turbine, mainly produces misalignment in turbines. The stress analysis on the pipe and the load on the nozzle is very important to ensure that the stress that occurs is still safe and the load that occurs on the nozzle is still below the allowable load. Field information is known, Steam type of 51-G-201-T, capacity 10 MW, total weighs 58 tons, weight casing 37 tons, which has been operating since July 1989, has been occur misalignment on turbines. Stress pipe and load analysis of turbine nozzles on the turbine using software (Autopipe V8i Select Series 3 Edition by Bentley). In this perspective, calculation methodologies were developed in order to do quick analysis of the most common configurations, according to the codes ASME B31.1 (Piping Power). The results of the pipe stress analysis showed that the maximum sustained stress ratio occurred at point A39 (0.32), maximum displacement stress ratio at point A39 (0.97) and maximum hoop stress ratio at point A09 (0.44), all values below 1. This shows that the stress is still safe. The result of load analysis on the turbine casing is the direction x = -880 kg, y = 6246.4kg, z = -3697.7kg, smaller than the weight of the 37 tones turbine casing, so misalignment is not caused by shifting the turbine casing.

Three-Dimensional Numerical Study of the Conical Nozzle Side Loads during Staging

AbstractThe objective of this paper is to numerically investigate the three-dimensional side loads and associated flow physics of a conical nozzle during the fire-in-the-hole staging event of the multistage rocket. The transient flow in nozzle is examined by a three-dimensional time-accurate numerical method with the start-up process of the upper-stage motor and the prescribed nominal separating motion of the lower stage. The impacts of asymmetric lateral motion due to non-nominal staging movement on the nozzle side loads are also numerically analyzed. These motion deviations include the relative angle between axes of two stages, relative lateral displacement between two stages, superposition of relative angle with relative lateral displacement, and angle of thrust vector control. As presented in the simulation results, the flow separation in nozzle is significantly prolonged and intensified by the obstruction of the lower stage. With the location of shockwave reflection approaching the dome of lower stag...

Pipe stress analysis on HCCR-TBS ancillary systems in conceptual design

Korean Helium Cooled Ceramic Reflector (HCCR) Test Blanket System (TBS) will be tested in ITER to demonstrate feasibility of the breeding blanket concept. The HCCR-TBS comprises Test Blanket Module (TBM) with associated shield, and ancillary systems located in various positions of ITER building. Currently, conceptual design for the HCCR-TBS is in progress. This paper presents pipe stress analysis results for the HCCR-TBS ancillary systems. The pipe stress analysis was performed in accordance with ASME B31.3 for major pipes of the Helium Cooling System (HCS) and the Coolant Purification System (CPS), which are operated in high pressure and temperature. The pipe stress for various load cases and load combinations were calculated. Operational pressure and temperature during plasma operation are applied as pressure load and thermal load, respectively. In addition seismic events were combined to investigate the code compliance for sustained load case and occasional load case. It was confirmed that the resultant stress meets the requirements of ASME B31.3 except one position in which it needs modification. These results give useful information for the next design phase, for example, nozzle loads for the component selection, the support design parameters, etc.

Effect of Nozzle Junction and Equipment Stiffness on Absorption of Pipe Thermal Loads

As an industry norm, the nozzle local loads are considered to be local and are not considered in foundation design. Presently, this norm is under debate. One opinion is some percent of these loads are to be considered to be transferred to the foundation. The horizontal forces on the foundation are more critical than vertical forces. Attempt has been made to understand the system and create a model which will represent the system to a good approximation. A mathematical model is developed to demonstrate the actual system. It is a stiffness system consisting of equipment, nozzle junction, and connected piping. The connected pipes are heated sequentially to generate nozzle loads in axial and out plane directions. Steady-state thermal loads are calculated for the given system stiffness. Governing parameters are identified and altered to note the effect. The governing parameters identified are equipment diameter (D), nozzle location on equipment (x), and nozzle diameter (d). The effect is studied for pressure range (20–120 bar) and temperature (100–400 °C). The results of percentage loads transferred with respect to the governing parameters are plotted. It is observed that nozzle loads in axial directions are transferred to the foundation almost 100%, whereas out plane loads are absorbed by the system to a greater extent. Further study is required to investigate combined effects of all such nozzle loads for single equipment. The results may be refined for different materials and effect of nozzle reinforcement.

Numerical analysis of flow separation and side loads of a conical nozzle during staging

The objective of this effort is to numerically investigate the effect of the fire-in-the-hole staging event on the start-up flow separation and side loads of a conical nozzle during flight. The axisymmetric transient flow structure in nozzle was examined by time-accurate numerical method with time-varying chamber pressure and separation gap width. Three-dimensional time-accurate computations to examine the side loads due to non-nominal staging movement were conducted for two particular cases: misalignment between two stages and the angle of the nozzle thrust vector direction. Each asymmetry case comprised several specific staging state points which determined the corresponding chamber pressure and staging gap width. As presented by the simulation results, the flow separation in nozzle is significantly prolonged and intensified by the obstruction of the lower stage dome. When the flow separation location moves close to the nozzle exit, a strenuously axial oscillation of the separation shock appears and lasts for a period of time. In the three-dimensional asymmetric computations, in spite of strenuous oscillation, the time-average of nozzle side loads indicate that the asymmetric staging situation could lead to large sustained lateral disturbance forces. An essential ingredient driving the flow unsteadiness and asymmetry is related to the deflected and reversed supersonic flow by the dome and interstage wall corner of lower stage.

Research on the Angle of Swirl Chamber Diesel Engine with Dual Channel

Swirl chamber diesel engine’s insert piece of channel performance has a great influence on the swirl chamber indoor airflow movement condition. So based on the 175F series bell flat bottom type swirl chamber’s single connection channel improvement, the influence law of swirl chamber indoor air movement during the injection time by the double connection channel angle at the engine rated speed 2600r/min was studied. Simplified boundary conditions to establish its mathematical solution model for the swirl chamber, then the fluid simulation software was used to research the original scheme and double channel with angle of 50 ° and 30 °, 40 °, 60 ° schemes’ swirl chamber indoor air movement. Results show that the angle of 40 ° dual channel form, the loss of the throttle was reduced, and the swirl chamber air velocity increases obviously, the swirl chamber air velocity in injection time up to 125 m/s,which not only increased indoor vortexes energy but also contribute to oil and gas preferably blended, and near the nozzle the temperature lower 20 °C than the original machine, effectively reducing the nozzle heat load.

Latest methods and new lessons learned for rotating machine piping

Optimum piping design, new support arrangement and latest layout configuration for rotating machines are addressed. New practical notes and latest achievements on rotating machine piping, nozzle load optimisation, stress analysis and flexibility review are discussed. The piping designers always want higher allowable nozzle loads to simplify piping designs, while the rotating machine manufacturers want smaller allowable nozzle loads to ensure good alignment, higher reliability and fewer operation complaints. From an operator’s point of view, where long-term reliability is a very important factor, the vote should go to the rotating machine manufacturer.

Transient Side-Load Analysis of Out-of-Round Film-Cooled Nozzle Extensions

Understanding the impact of out-of-round nozzle extension on the nozzle side load during engine transient startup operations has garnered special interest from design engineers of late. The out-of-round nozzle extension could be the result of asymmetric internal stresses, deformation induced by previous tests, and asymmetric loads induced by hardware attached to the nozzle. The objective of this study was to computationally investigate the effect of out-of-round nozzle extension on the nozzle side loads during an engine startup transient. The rocket engine studied encompasses a regeneratively cooled chamber and nozzle, along with a film-cooled nozzle extension. The computational methodology is based on an unstructured-grid pressure-based computational fluid dynamics formulation, and on transient inlet boundary flow properties derived from an engine system simulation. Six three-dimensional cases were performed, with the out of roundness achieved by three different degrees of ovalization, elongated on lateral and axes: one slightly ovalized, one more ovalized, and one significantly ovalized. The results show that the separation line jump was the primary peak side-load physics. Compared with the peak side load of the perfectly round nozzle, the peak side loads increased most for the slightly ovalized nozzle extensions. The peak side loads then reduced moderately from the slightly ovalized nozzle extensions to the more ovalized nozzle extensions. For the significantly ovalized nozzle extensions, the peak side loads dropped substantially from those of the slightly ovalized nozzle extensions, due to increased flow directionality.

Clarifying nozzle load and piping

Piping designers always want higher allowable nozzle loads to simplify pump piping designs, while pump manufacturers want smaller such loads to assure good alignment, higher reliability and fewer problems in operation. With long-term reliability a key factor, Amin Almasi recommends that users side with the manufacturer.

Practical notes on power plant machinery nozzle load and piping

The piping designers always want higher allowable machinery nozzle loads to simplify piping designs, while the rotating machine manufacturers want smaller allowable nozzle loads to assure good alignment, higher reliability and fewer operation complaints. From the power plant operator's point of view, where long-term reliability is a very important factor, the vote should go to the manufacturer. Optimum power piping design, support arrangement and layout configuration for rotating machines of a power plant (turbines, pumps, others) are addressed. Modern practical notes, new guidelines, recent lessons learned and latest achievements on power piping, power machinery nozzle load optimization, stress analysis and piping flexibility review are discussed.

Ascending rockets as macroscopic self-propelled Brownian oscillators

High-fidelity numerical experiments and theoretical modelling are used to study the dynamics of a sounding-rocket-scale rocket, subject to altitude-dependent random wind and nozzle side loads and deterministic aerodynamic loading. This paper completes a series of studies that showed that Ornstein–Uhlenbeck (OU) rotational dynamics arise when random nozzle side loads dominate wind and aerodynamic loading. In contrast to the earlier work, this paper elucidates that under conditions where aerodynamic, wind and nozzle side loads are comparable, the rocket behaves as stochastic Brownian oscillator. The Brownian oscillator model allows straightforward interpretation of the complex rotational dynamics observed: three dynamical regimes—each characterized by differing balances between nozzle-side-load-induced torques, spring-like aerodynamic torques and mass flux damping torques—characterize rocket ascent. Further, the paper illuminates that in the limit where wind and aerodynamic loads are small, random mass flux variations exponentially amplify side-load-induced rotational stochasticity. In this practical limit, pitch/yaw dynamics are described by a randomly damped OU process; an exact solution of the associated Fokker–Planck equation can be obtained and used to compute, e.g. time-dependent pitch/yaw rate means and variances.