scholarly journals Experimental and Numerical Investigations on the Ignition of RBCC Gas-Oxygen/Kerosene Rocket Ejector

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Bingyang Liu ◽  
Ping Jin ◽  
Yixin Ma ◽  
Yaqun Qi ◽  
Guobiao Cai ◽  
...  
Keyword(s):  
Numerical Model ◽  
Peak Pressure ◽  
Ignition Time ◽  
Stable State ◽  
Vital Role ◽  
Combined Cycle ◽  
Normal Operation ◽  
Combustion Mechanism ◽  
Thrust Chamber ◽  
Swirl Injector

The rocket ejector refers to a core component of a rocket-based combined cycle (RBCC) engine. The ignition is of critical significance for rocket ejection. Reliable and stable ignition crucially determines the normal operation of the engine. In this paper, a thrust chamber with coaxial swirl injector for the RBCC rocket ejection was developed and tested. Gas oxygen (GOX) and kerosene acted as propellants. As revealed from the test results, the process of ignition pressurizing comprised four phases. The oxygen prefilling time before ignition slightly impacted the ignition time, whereas it affected the peak pressure of ignition. In a confined range, the peak pressure decreased as the prefilling time was extended. The ignition was simulated by building a numerical model, and the results well complied with the experimentally achieved results. The numerical model is capable of specifically indicating the position of the kernel of fire and the process of flame propagation. The simulation results reveal that the propellant could form a combustible condition within 4 ms. The kernel was 6 mm away from the injector, located at the oxygen and kerosene mixing interface and approaching the upper wall. The above results reflected the vital role of the central recirculation zone formed by the prefilled oxygen. The ignition energy was transported near the injector under the convection effect, which ignited the stoichiometric mixture, and the entire ignition could reach a stable state within 20 ms. The numerical model which was developed in this paper can help clarify the combustion mechanism.

Influence of different curing regimes on properties of new copolymer of chloroprene and acrylonitrile

2021 ◽  
pp. 009524432110386
Author(s):  
Mousumi De Sarkar ◽  
Takashi Sunada ◽  
Atsunori Kondo
Keyword(s):  
Stable State ◽  
Industrial Applications ◽  
Vital Role ◽  
Product Families ◽  
Compression Set ◽  
Rubber Compounds ◽  
Chloroprene Rubber ◽  
Ethylene Thiourea ◽  
Curing Regimes ◽  
Curing Systems

The curing system plays a vital role in designing rubber compounds for various industrial applications. Therefore, it is paramount to establish viable curing strategies for any new elastomer to explore its application potentials and commercial significance. Impacts of different curing regimes on the properties of a recently developed copolymer of chloroprene and acrylonitrile (acrylonitrile-chloroprene rubber, NCR) are reported here. Several primary accelerators (four from thiourea- and one from thiazolene product families) were used for curing the new rubber along with fixed loadings of zinc oxide (5 phr) and magnesium oxide (4 phr). Besides, curatives based on sulfur and peroxide were also evaluated. The influence of different curing systems on the rheological and physical properties of the copolymer was explored. It has been seen that the properties of the copolymer are considerably influenced by the different curing systems used. While ethylene thiourea (ETU) and propylene thiourea (PTU), as primary accelerators, provide the highest state of cure but may cause scorch. The use of trimethyl thiourea (TMU), on the other hand, results in the fastest rate and the most stable state of cure, good scorch safety, bin stability, and an overall good balance of properties. The sulfur-based crosslinking system induces good mechanical properties but causes limited bin stability, poor high-temperature compression set, and impaired heat resistance properties. As a curing agent, peroxide delivers the best bin stability in the rubber stocks but yields higher stiffness and limited aging resistance in the vulcanizates.

scholarly journals Vibration-Isolation Performance of a Pile Barrier in an Area of Soft Soil in Shanghai

2020 ◽  
Vol 2020 ◽  
pp. 1-27
Author(s):  
X. F. Ma ◽  
M. Y. Cao ◽  
X. Q. Gu ◽  
B. M. Zhang ◽  
Z. H. Yang ◽  
...  
Keyword(s):  
Numerical Model ◽  
Vibration Isolation ◽  
Soil Layer ◽  
Isolation Effect ◽  
Normal Operation ◽  
Vibration Source ◽  
Filling Material ◽  
Vibration Measurements ◽  
Pile Diameter ◽  
Environmental Vibration

Environmental vibration caused by traffic can affect the normal operation of precision instruments, and vibration-isolation measures should be taken to reduce such negative effects. The engineering background of this paper is a hard-X-ray tunnel under construction in Shanghai, China. First, field vibration measurements are used to study the characteristics of the ground traffic, maglev, subway, and other vibration sources near the tunnel, as well as the laws governing the propagation of vibration waves in the surface and soil layer. The finite-element modelling is then used to establish a two-dimensional numerical model for the field conditions, and the numerical results are compared with the field vibration measurements to validate the applicability of the numerical model for assessing the effects of environmental vibration. Finally, how the parameters of a pile-barrier vibration-isolation system, a vibration-isolation measure used widely for tunnels, influence its performance is studied. The results show the following: with increasing distance from the vibration source, the amplitude of the vibration acceleration decreases gradually, and the high-frequency part of the vibration wave is attenuated rapidly, whereas the low-frequency part is attenuated very little. The vibration-isolation effect of the pile barrier is directly proportional to the elastic modulus of the pile body, the pile length, and the hollow ratio of the pile, and inversely proportional to the stiffness of the filling material. The pile diameter, pile row number, and row spacing have little influence on the vibration-isolation effect. Increasing the pile diameter attenuates the acceleration amplitude somewhat around 10 Hz but has no effect on it around 5 Hz. Overall, the present numerical method is well suited to evaluating environmental vibration problems.

Chaos Characteristics and Control of Permanent Magnet Synchronous Motors

2011 ◽  
Vol 48-49 ◽  
pp. 292-299 ◽  
Author(s):  
Wei Xue ◽  
Yan Ling Guo ◽  
Yong Li Li
Keyword(s):  
Permanent Magnet ◽  
Permanent Magnet Synchronous Motor ◽  
Stable State ◽  
Nonlinear Dynamic System ◽  
Synchronous Motor ◽  
Normal Operation ◽  
Permanent Magnet Synchronous Motors ◽  
Synchronous Motors ◽  
System Parameters ◽  
And Control

The permanent magnet synchronous motor (PMSM), a nonlinear dynamic system, can exhibit prominent chaotic characteristics under some choices of system parameters and external inputs. Based on a mathematical model of the permanent magnet synchronous motor, the existence of chaotic attractor is verified by the phase trajectory, Lyapunov exponent map and the bifurcation diagram. Chaotic phenomenon, such as a strong oscillation of speed and torque, unstable operating performance, affects the normal operation of motor. It makes the PMSM in a stable state to control chaos of the PMSM with a control strategy of infinitesimal geometry, which can eliminate chaos well.

scholarly journals Experimental Research on the Influence of Working Conditions on Vibration and Temperature Rise of Si3N4 Full-Ceramic Bearing Motors

2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Zhongxian Xia ◽  
Yuhou Wu ◽  
Hua Wei ◽  
Kexuan Ren ◽  
Longfei Gao ◽  
...  
Keyword(s):  
Working Conditions ◽  
Temperature Rise ◽  
Rotational Speed ◽  
Stable State ◽  
Vibration Signal ◽  
Spindle Motor ◽  
Normal Operation ◽  
Vibration Velocity ◽  
Ceramic Bearing ◽  
Lubrication Conditions

Working conditions such as lubrication, preload, and rotational speed have important influence on vibration and temperature rise of the spindle motor. In this study, controlled variable experiments are carried out on the silicon nitride (Si3N4) full-ceramic ball bearing and steel bearing of the same type, and the vibration signal characteristics and temperature rise of the spindle motor are tested and analysed, by changing the lubrication conditions, preloads, and rotational speeds of the spindle motor. Through the research, it is found that as the rotational speed increases, the vibration velocity of the Si3N4 full-ceramic bearing spindle motor under different preloads and lubrication conditions shows an overall increasing trend; kurtosis generally presents a downward trend and gradually flattens, indicating that although the vibration velocity increases at high speeds, the vibration signal shows a relatively stable state. As the rotational speed increases, the difference of vibration velocity under the condition of applying preload and no preload decreases, indicating that the influence of preload on the vibration of full-ceramic bearing spindle motor decreases with the increase in rotational speeds. At the same time, it is found that fr and 5fr have greater impact on the vibration of full-ceramic bearing spindle motor, where fr is the frequency of the bearing in normal operation, and 5fr is 5 times of the normal operating frequency. Lubrication conditions have little effect on the temperature rise of full-ceramic bearing spindle motor, and the temperature rise under nonlubricated conditions is even slightly lower than that under grease lubrication conditions. The research results show that the vibration velocity and temperature rise of Si3N4 full-ceramic bearing spindle motor are less than those of steel bearing with the same type, indicating that full-ceramic bearing has better performance than steel bearing under the same working conditions.

scholarly journals Cyberattack Detection for Cyber Physical Systems Security – A Preliminary Study

2018 ◽  
Vol 10 (1) ◽  
Author(s):  
Weizhong Yan ◽  
Lalit Mestha ◽  
Justin John ◽  
Daniel Holzhauer ◽  
Masoud Abbaszadeh ◽  
...  
Keyword(s):  
Gas Turbines ◽  
Cyber Physical Systems ◽  
Detection Performance ◽  
Combined Cycle ◽  
Normal Operation ◽  
Sufficient Information ◽  
Detection Scheme ◽  
Physical Systems ◽  
Detection Techniques ◽  
Physical Measurements

Cyber-physical systems (CPS) security has become an increasingly important research topic in recent years. Geared towards more advanced cyberattack detection techniques as part of strategies for enhancing the security of CPS, in this paper we propose a machine learning based cyber-attack detection scheme. The proposed scheme is a physical-domain technique; specifically, it assumes the physical measurements of the system carry sufficient information for capturing the system behavior, thus can be used for differentiating normal operation and attacks. CPS are complex in nature and the number of physical measurements available for CPS is often overwhelmingly high. Thus, accurately modeling CPS’ dynamic behavior, more importantly, distinguishing normal and adversary activities based on the large number of physical measurements, can be challenging. To address the challenge, we have focused our research effort on feature engineering, that is, to intelligently derive a set of salient signatures or features from the noisy measurements. We make sure the derived features are more compact and, more importantly, have more discriminant power than the original physical measurements, thus enabling us to achieve more accurate and robust detection performance. To demonstrate the effectiveness of the proposed scheme, in our experimental study we consider gas turbines of combined cycle power plants as the cyber-physical system. Using the data from the high-fidelity simulation we show that our proposed cyberattack detection scheme is able to achieve high detection performance.

scholarly journals Numerical Investigation of Tool Parameters Influence on the Interlock Forming During Flat Clinching Process

2021 ◽  
Author(s):  
Zhiyong Wang ◽  
Shanling Han ◽  
Zhiyong Li ◽  
Yong Li
Keyword(s):  
Finite Element ◽  
Numerical Model ◽  
Linear Relationship ◽  
Numerical Investigation ◽  
Vital Role ◽  
Blank Holder ◽  
Finite Element Software ◽  
Punch Radius ◽  
Deform 2D ◽  
The Relationship

Abstract Tool parameters play a vital role in the mechanical interlock formation during the flat clinching process, to understand the influence of tool parameters on the interlock formation, the finite element software DEFORM-2D was used to build the numerical model of the flat clinching process, and the numerical model was verified by the experiment. The influences of the punch radius, punch fillet radius, and blank holder radius on the interlock formation of the clinched joint were investigated using the numerical model. Then, the relationship between the punch radius and blank holder radius was studied. The results showed that the interlock gradually increases with the increase of the blank holder radius, after that, the interlock begins to decrease. To maximize the interlock, the punch radius and the blank holder radius should be increased simultaneously. It can be concluded that the blank holder radius and the punch radius should keep in a linear relationship when designing the geometric dimensions of the flat clinch tools, which can promote the application of flat clinching process in car body manufacturing.

Failure Analysis for Evaporator Fin-Tubes of HRSG in CCGT

2020 ◽  
Author(s):  
Hong Xu
Keyword(s):  
Pitting Corrosion ◽  
Power Plants ◽  
Ph Value ◽  
Water Pressure ◽  
Carbon Steels ◽  
Combined Cycle ◽  
Normal Operation ◽  
Hydraulic Test ◽  
Commercial Operation ◽  
The Matrix

Abstract The finned evaporator tube of medium pressure evaporator leakage occurred after the no. 1 unit of a combined-cycle gas turbine (CCGT) power station was put into commercial operation for only 40 days (including 24 days of operation and 19 days of shutdown and standby). Cut off a section of failure pipe for a thorough inspection. Macro inspection found that severe corrosion occurred in some local areas of some pipe sections, which led to the obvious thinning of pipe wall thickness, leading to perforation and leakage. Metallographic test and scanning electron microscopy (SEM) showed that the metal materials around the leakage points was qualified and the microstructure was normal. The corrosion products around the leakage points were mainly iron oxide which were generated before the unit had been put into commercial operation. The root cause was that the pH value of water used in the hydraulic test during the commissioning of the unit was as low as 9.2, and after the completion of the hydraulic test, the filled water remained in the boiler for a month and a half before being drained. Researches indicated that if carbon steels were prolonged immersed in demineralized water with a lower pH value, it would inevitably occur severe local corrosion which was due to pitting induced by the activation of inclusions in the steel. After pitting corrosion induced by active inclusions, no obvious pitting corrosion occurred in the surrounding inclusions. Accompanied with the extending of corrosion spots that had been formed, the activation zone continued to expand. Along with the formation of surface rust spots, corrosion developed along the inclusion boundary to the depth of the matrix, and finally caused the perforating and leaking of the tubes. The inner pitting corrosion of fin-tube of evaporator in HRSG could be avoided as long as the relevant provisions of “Guidelines of chemical supervision for combined cycle power plants” (DL/T 1717-2017) were strictly implemented during normal operation of boiler, standby maintenance and water pressure test after overhaul.

scholarly journals Energy production assessment in a complex hydropower development

2019 ◽  
Vol 22 (4) ◽  
pp. 725-737 ◽  
Author(s):  
Andrei-Mugur Georgescu ◽  
Sanda-Carmen Georgescu ◽  
Georgiana Dunca ◽  
Diana Maria Bucur ◽  
Alexandru Aldea
Keyword(s):  
Numerical Model ◽  
Energy Production ◽  
Point Of View ◽  
Hydropower Plant ◽  
Normal Operation ◽  
Centrifugal Pumps ◽  
Hydropower Development ◽  
Upstream Reservoir ◽  
Set Up ◽  
Pumped Storage

Abstract A complex multi-reservoir hydropower development (HPD) was studied from the point of view of energy production. The Gâlceag HPD system consists of three reservoirs, a high head hydropower plant (HPP) powered by two Francis turbines of 75 MW each, and a pumping station (PS) equipped with two centrifugal pumps of 10 MW each. The hydraulic system configuration is unusual: the PS discharge pipe conveys the water directly into HPP's penstock. Three operation scenarios were investigated: ① normal operation (with PS shutdown and HPP operational, as a conventional HPP), ② simultaneous operation (with both HPP and PS operational), and ③ pumped storage (with HPP shutdown and PS operational). Primarily, a numerical model was set up in EPANET to investigate the influence that the variation in the initial level of the HPP upstream reservoir has on the production of energy. In the sequel, a numerical model was derived and solved in GNU Octave to investigate the influence on the energy production of HPD due to initial levels of both the HPP upstream and downstream reservoirs. The results can be used in a decision support system to assess the overall operation of Gâlceag HPD based on water availability.

Design Guidelines for the Safe Operation of Steam Surface Condenser Turbine Bypass on Combined Cycle Power Plants

2017 ◽  
Author(s):  
Darren M. Nightingale
Keyword(s):  
Power Plant ◽  
Power Plants ◽  
Design Guidelines ◽  
Combined Cycle ◽  
Normal Operation ◽  
Fundamental Aspect ◽  
Design Parameters ◽  
The Past ◽  
Surface Condenser ◽  
Start Ups

The ability to bypass steam, around the steam turbine and directly into a steam surface condenser, has been a fundamental aspect of the design of base loaded power plants for many years. The increased dependence on natural gas, and the subsequent increase in the number of combined cycle plants, has provided additional challenges for the condenser designer, and also the plant operator, with respect to safely accommodating steam bypass. However, the steam bypass requirements for modern combined cycle power plants differ significantly from those of traditionally base loaded plants, like fossil and nuclear. Higher cycle frequencies for steam bypass, faster start-ups, as well as increases in bypass steam temperatures and pressures, have all impacted the design criteria for the condenser. Indeed, for modern combined cycle plants, the bypass steam conditions are often higher than normal operation, such that the bypass requirements can very well dictate the overall design of the condenser. This, in turn, has resulted in an increase in the reported instances of operational problems, tube failures, condenser damage and plant shutdowns due to steam bypass related issues. Recorded issues and reported failures experienced by combined cycle power plants during steam bypass, have been traced to causes such as transient conditions during commissioning, faster start-ups, the poor design and location of steam bypass headers internal to the condenser, over-heating due to curtain spray deficiencies, excessive tube vibration and tube failures. Many of these issues are based on an inherent lack of understanding of the impact of the rigors of steam bypass on condenser internals. Furthermore, operation of steam bypass outside of the generally accepted design parameters often compounds these problems. This paper consolidates the learning and advances in the design of turbine bypass systems for steam surface condensers from the past 20, or so, years. It includes current design guidelines, as well as safe operational limitations, and general considerations for minimizing potential damage when operating steam bypass on a modern combined cycle power plant. Included is a Case Study of how an existing fossil power plant that was repowered, along with the existing steam surface condenser that was modified to accept the bypass steam, experienced excessive erosion and damage during the past 10+ years of operation. The condenser was recently reviewed once again, and additional modifications were implemented to take advantage of current improvements in steam bypass design. This drastically reduced further erosion and improved the condenser availability, reliability and longevity; thereby improving the plant efficiency.

scholarly journals Numerical Model of a Variable-Combined-Cycle Engine for Dual Subsonic and Supersonic Cruise

Energies ◽  
2013 ◽  
Vol 6 (2) ◽  
pp. 839-870 ◽  
Author(s):  
Victor Fernandez-Villace ◽  
Guillermo Paniagua
Keyword(s):  
Numerical Model ◽  
Combined Cycle
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