Start-up Sequence Research Articles

B3 ロケットノズルに生じる横推力に関する3次元非定常CFD

Recently, a large side load is observed during start-up and shutdown sequences of Japanese LE-7A rocket engine nozzle. The objective of the present paper is to clarify the mechanism producing the large side loads during start-up process. The unsteady 3-D Navier-Stokes equations are solved for start-up process of three types of nozzle contours. That is, truncated perfect (TP) nozzle, 86% compressed truncated perfect (CTP) nozzle and CTP50-R5-L nozzle. The contour of TP nozzle and the contour of 86% CTP nozzle are LE-7 nozzle and the original LE-7A nozzle respectively. Asymmetric flow fields and large side loads are observed for LE-7A and CTP50-R5-L nozzles. There are two flow patterns which cause the large side loads. The first is the simultaneous occurrence of the Free Shock Separation (FSS) and the Restricted Shock Separation (RSS). The second is the oscillation of Mach disk under the RSS condition.

A Multiagent System for Monitoring Industrial Gas Turbine Startup Sequences

This paper introduces a novel technique for condition monitoring of gas turbine start-up sequences. The vast amount of data and the complex processes behind on-line fault detection indicate the need for an automated solution. A multi-agent system that views the problem as the interaction of simple independent software entities for effective use of the available data is presented. The overall solution is derived from the combination of partial solutions provided by the components of the multiagent system. As a consequence, data interpretation is achieved by converting the data into appropriate information and combining individual agents' information, resulting in an automatic fault diagnosis for the engineers. This multiagent system can employ various intelligent system techniques and has been implemented using the ZEUS agent building toolkit.

Reasoning with modal logic for power plant condition monitoring

This letter demonstrates the use of modal logic for knowledge representation for condition monitoring of gas turbine start-up sequences. The potentially large amounts of data and the complex real-time processes behind on-line fault detection indicate the need for software entities that can reason and react to changing environmental conditions. These are known as intelligent software agents. As a consequence, data interpretation is achieved by converting the data into appropriate information and combining individual agents' knowledge, resulting in an automatic fault diagnosis.

Startup Thermal Considerations for Supercritical-Pressure Light Water-Cooled Reactors

Supercritical-pressure light water-cooled reactors (SCRs) are innovative systems aimed at high efficiency and cost reduction. The once-through direct-cycle plant system is the leading system of fossil-fired power plants (FPPs). Estimates of the coolability and necessary sizes of the SCR startup systems, sequences, and required equipment for startup are investigated with reference to supercritical FPPs. There are two types of supercritical boilers. One is a constant pressure boiler, and the other is a variable pressure boiler.First, startup of the constant pressure boiler is examined. The reactor starts at a supercritical pressure. A startup bypass system consisting of a flash tank and pressure-reducing valves is required. Second, startup of the variable pressure boiler is investigated. The reactor starts at a subcritical pressure, and the pressure increases with the load. A steam-water separator and a drain tank are required for startup.The results of computer calculations show that with both constant pressure and variable pressure startup, the peak cladding temperature does not exceed the operating limit through startup, and both startup sequences are feasible. The sizes of the components required for the startup systems are assessed. To simplify the plant system and to reduce the component size, variable pressure startup with steam separators in the bypass line appears desirable.

A multi agent system for monitoring industrial gas turbine start-up sequences

A multi agent system for monitoring industrial gas turbine start-up sequences

Reasoning with Modal Logic for Power Plant Condition Monitoring

This letter demonstrates the use of modal logic for knowledge representation for condition monitoring of gas turbine start-up sequences. The potentially large amounts of data and the complex real-time processes behind on-line fault detection indicate the need for software entities that can reason and react to changing environmental conditions. These are known as intelligent software agents. As a consequence, data interpretation is achieved by converting the data into appropriate information and combining individual agents' knowledge, resulting in an automatic fault diagnosis.

Dynamics and control during startup of heat integrated distillation column

To advocate the usage of process integration in industrial practice, it is important to be able to guarantee not only robust control during near steady state operation, but also to provide procedures for generating fast and reliable startup sequences. This contribution concentrates on describing a systematic procedure for development of plant startup sequences. The basis for the startup procedure development is available qualitative process knowledge. Application of the startup sequence generation procedure is demonstrated upon a heat integrated distillation plant. This plant illustrates some of the inherent effects of process integration upon a startup procedure. In particular, the effect of energy recycle upon the possible startup sequences and the effect of using an actuator for control purposes, i.e. the heat pump, which in itself requires significant startup time. The experimental application of two generated startup sequences illustrates that safe and reliable startups are ensured.

Recycling of electrical motors by automatic disassembly

This paper presents a robotized workstation for end-of-life treatment of electrical motors with an electrical effect of about 1 kW. These motors can, for example, be found in washing machines and in industry. There are two main steps in the work. The first step is an inspection whereby the functionality of the motor is checked and classification either for re-use or for disassembly is done. In the second step the motors classified for disassembly are disassembled in a robotized automatic station. In the initial step measurements are performed during a start-up sequence of about 1 s. By measuring the rotation speed and the current and voltage of the three phases of the motor classification for either reuse or disassembly can be done. During the disassembly work, vision data are fused in order to classify the motors according to their type. The vision system also feeds the control system of the robot with various object co-ordinates, to facilitate correct operation of the robot. Finally, tests with a vision system and eddy-current equipment are performed to decide whether all copper has been removed from the stator.

Towards ?plug and control?: self-tuning temperature controller for PLC

Software PID controllers have become a standard component of automation with PLCs (programmable logic controllers) and work together with classical sequential function charts in the same processing units. However, traditional methods for the computer-aided design of control systems often involve high mathematical effort and are usually implemented on additional PCs that are only connected for commissioning purposes. Therefore a new, very simple concept for self-tuning PID controllers will be presented, which is implemented together with the controller on the PLC and which enables automatic tuning without prior knowledge of the process. The concept is designed specifically for temperature control, but can also be used for other control loops in the process industry which show stable time-lag dynamics and allow sufficient setpoint steps. For users, the most important advantage is the drastic reduction of commissioning time and effort. If, for example, there are 10 temperature loops in one machine, the successive tuning of all 10 controllers used to require several days. With the new concept, there is no longer any need for dedicated tuning. The self-tuning of all control loops is performed automatically and simultaneously on machine startup. Control performance is better than it is with the traditionally designed PID controllers, particularly for slow temperature processes. The concept is based on a systematic startup sequence to explore process dynamics, a modified inflection point method for process identification and a separation of setpoint and disturbance control. Copyright © 2000 John Wiley & Sons, Ltd.

Self-sustained steady state tokamak plasmas

Self-sustained steady-state tokamak equilibria for National Spherical Torus Experiment (NSTX) and Spherical Torus-Volume Neutron Source (ST-VNS) are presented. It is demonstrated that the amount of the pressure gradient driven current which includes the bootstrap current and the diamagnetic current is comparable to the designed current specification in these devices. A possible startup sequence by increasing plasma pressure is also illustrated.

Analysis of dynamical behaviour of a rotor with deflection limiters

The dynamical behaviour of a rotor running into contact with a non-annular stator is studied by numerical simulations. The rotor is represented by a 2-dof model moving in one plane. The stator models an arbitrary number of discrete stops by superimposing annular stators with large clearances and high offsets. Friction forces are included in the contact description. The strongly nonlinear differential equations are integrated using a fourth-order Runge-Kutta procedure. Time histories for start-up and run-down sequences are simulated in two numerical examples. Different stop configurations have been evaluated. For a configuration with four symmetrically distributed stops an interesting bouncing phenomenon was discovered. This was not found for a non-symmetrical configuration. When the bouncing phenomenon occurred, the radial displacement of the rotor was larger for the stators with stops than for an annular stator.

A high-speed, low-power clock generator for a microprocessor application

This paper discusses the design of the clock generator for the Alpha 21264. As the speed performances are of primary concern in the whole design, the clock-generator jitter and phase misalignment must be as low as possible in a very noisy environment. A dedicated on-chip voltage regulator based on a bandgap reference has been designed to reduce the effect of supply noise on the clock generator. To avoid a large voltage drop across the power-supply bond wires during the startup sequence, the core frequency can be increased by steps in one period of the core clock, with a limited frequency overshoot and no missing pulses. The circuit has been implemented in a CMOS 0.35 /spl mu/m process. The voltage-controlled-oscillator frequency range is between 350 MHz and 2.8 GHz, with a peak-to-peak cycle-to-cycle jitter lower than 16 ps. While booting Unix on a system, the maximum phase misalignment is lower than /spl plusmn/100 ps.

The Stages Model of High-Tech Venture Founding: Tried but True?

Recent large sample studies of start-up event sequences reported more stochasticity at a population level of analysis than the stages model would have predicted. This study examined a random sample of 18 technology-intensive start-ups in manufacturing and business service industries and found examples of both the stages model and an alternative. Stages model start-ups significantly outperformed the others.

Treatment system response to transient AOX (adsorbable organic halogen) loadings

If promulgated as proposed, effluent guidelines for the U.S. pulp and paper industry will impose average monthly and maximum daily numerical limits of discharged AOX (adsorbable organic halogen). At this time, it is unclear whether the maximum-day variability factor used to establish the proposed effluent guidelines will provide sufficient margin for mills to achieve compliance during periods of normal but variable operating conditions within the pulping and bleaching processes. Consequently, additional information is needed to relate transient AOX loadings with final AOX discharges. This paper presents a simplistic dynamic model of AOX decay during treatment. The model consists of hydraulic characterization of an activated sludge process and a first-order decay coefficient for AOX removal. Data for model development were acquired by frequent collection of influent and effluent samples at a bleach kraft mill during a bleach plant shutdown and startup sequence.

Treatment system response to transient AOX (adsorbable organic halogen) loadings

If promulgated as proposed, effluent guidelines for the U.S. pulp and paper industry will impose average monthly and maximum daily numerical limits of discharged AOX (adsorbable organic halogen). At this time, it is unclear whether the maximum-day variability factor used to establish the proposed effluent guidelines will provide sufficient margin for mills to achieve compliance during periods of normal but variable operating conditions within the pulping and bleaching processes. Consequently, additional information is needed to relate transient AOX loadings with final AOX discharges. This paper presents a simplistic dynamic model of AOX decay during treatment. The model consists of hydraulic characterization of an activated sludge process and a first-order decay coefficient for AOX removal. Data for model development were acquired by frequent collection of influent and effluent samples at a bleach kraft mill during a bleach plant shutdown and startup sequence.

Exploring start-up event sequences

Exploring start-up event sequences

Two-phase cooling system with a jet pump for spacecraft

A two-phase cooling system with a jet pump is proposed for the thermal control of spacecraft. The system does not require an external source of energy, the pumping of the working fluid is performed by the work that is produced in a thermodynamic cycle being carried out in the heat transport loop. The cooling system has no moving parts or control devices, with the exception of a mechanical pump and an actuated valve, that are used only for the startup sequence. This article reports on the results of the theoretical and experimental studies of the two-phase thermal control system with a jet pump for spacecraft application. A mathematical model for the steady-state analysis of the proposed system was developed. The model was applied to predict overall performance characteristics and operating range for a specific spacecraft two-phase cooling system. The possible reasons for the fluid loop operation failures were identified. The influence of the accumulator volume on the system characteristics was also investigated. Three jet pumps of various configurations were tested and stable operational regimes of the cooling system were obtained under different heat-load and heat-rejection conditions on a ground experimental facility.

Tie line utilization during power system restoration

This paper identifies some of the critical roles of tie lines during power system restoration. Based on these roles, a systematic approach is developed to evaluate the impact of the availability of tie line assistance on restoration. Using this approach, a tie line expert system module has also been developed to supplement the previously developed EPRI restoration expert system (RES). The enhanced RES can now include available tie line power in recommending a restoration strategy to maximize the system generation capability by modifying the generator startup sequence. Simulation results confirm that outside assistance will improve the overall generation capability and provide an extra dimension to the flexibility of a company's restoration strategy. >

Joint data and channel estimation using blind trellis search techniques

A novel method of maximum likelihood sequence estimation is proposed for data that are transmitted over unknown linear channels. This procedure does not require a startup sequence for estimating the channel impulse response. Rather, the data and the channel are simultaneously estimated. It is implemented without any loss of optimality by a trellis search algorithm which searches for the best data sequence from among a number of hypothesized trellises which are constructed from the observed sequence. The number of states in each trellis and the number of trellises grow exponentially with the channel memory. A suboptimal trellis search algorithm is proposed whose complexity at best is slightly higher than that of the adaptive Viterbi algorithm operating with a known channel response. A simplified channel estimation algorithm when the number of data alphabets is greater than 2 is also proposed. Fast convergence of the algorithm in estimating the channel is demonstrated for binary pulse amplitude modulation over a variety of channels. Convergence over a wide range of SNR occurs within 100 symbols. The channel estimation algorithm for multi-level signals converges within 500-1000 symbols. We finally present an application of this algorithm to the problem of sequence estimation in the presence of rapidly time-varying intersymbol interference. The algorithm provides reliable zero-delay decisions which results in a better channel tracking algorithm when compared to previously proposed schemes.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Effect of start-up procedure on the cyclic stress-strain behaviour of polycrystalline copper

The length of the start-up loading sequence in stress-controlled high-cycle fatigue tests was found to considerably affect the cyclic hardening curves, the corresponding saturated dislocation structures and the fatigue lives of polycrystalline copper specimens. These findings seem of particular importance when fatigue data from different sources or test equipment are compared.