Quasi-Steady Analysis of Impulse Turbine Under Reciprocating Flow

2021 ◽  
Author(s):  
Yang Yu ◽  
Mingren Zhao ◽  
Zhenmian Li ◽  
Jianxing Yu ◽  
Yang Gao ◽  
...  
Keyword(s):  
Steady Flow ◽  
Analysis Method ◽  
Impulse Turbine ◽  
Velocity Change ◽  
Pressure Drops ◽  
Turbine Performance ◽  
Performance Curves ◽  
Acceleration And Deceleration ◽  
Short Time ◽  
Reciprocating Flow

Abstract The impulse turbine, which is a part of an oscillating wave column, plays an indispensable role in wave energy conversion. In this paper, a self-rectifying impulse turbine has been investigated numerically under reciprocating flow and the quasi-steady analysis method of the turbine has been studied. Firstly, the numerical model was validated by corresponding experiment results. Then, the reciprocating flow condition was accurately simulated with the method of setting double velocity inlets. The results showed that there existed hysteretic loops in turbine performance curves. And different pressure drops in acceleration and deceleration led to this hysteretic characteristic. Finally, in order to investigate quasi-steady analysis method, the frequency and amplitude of the reciprocating flow were changed respectively and the results were compared with those of steady flow. It has been found that hysteretic loops are distributed around the curves of steady flow. When the frequency is lower or amplitude is smaller, the results of reciprocating flow are closer to those of steady flow. In conclusion, the performance of steady flow can be used to predict the performance of reciprocating flow with little velocity change in a short time, which reveals the feasibility of quasi-steady analysis method.

Influence of Blade Deterioration on Compressor and Turbine Performance

2008 ◽  
Author(s):  
M. Morini ◽  
M. Pinelli ◽  
P. R. Spina ◽  
M. Venturini
Keyword(s):  
Gas Turbine ◽  
Mechanical Damage ◽  
Turbine Stage ◽  
Geometric Data ◽  
Turbine Performance ◽  
State Determination ◽  
Performance Curves ◽  
Common Causes ◽  
Simple Scaling ◽  
Main Effects

Gas turbine operating state determination consists of the assessment of the modification, due to deterioration and fault, of performance and geometric data characterizing machine components. One of the main effects of deterioration and fault is the modification of compressor and turbine performance maps. Since detailed information about actual modification of component maps is usually unavailable, many authors simulate the effects of deterioration and fault by a simple scaling of the map itself. In this paper, stage-by-stage models of the compressor and the turbine are used in order to assess the actual modification of compressor and turbine performance maps due to blade deterioration. The compressor is modeled by using generalized performance curves of each stage matched by means of a stage-stacking procedure. Each turbine stage is instead modeled as a couple of nozzles, a fixed one (stator) and a moving one (rotor). The results obtained by simulating some of the most common causes of blade deterioration (i.e., compressor fouling, compressor mechanical damage, turbine fouling and turbine erosion, occurring in one or more stages simultaneously) are reported in this paper. Moreover, compressor and turbine maps obtained through a stage-by-stage procedure are compared to the ones obtained by means of map scaling.

scholarly journals Experimental study on water level and absorption capacity in a radial well flow in a loess area

2018 ◽  
Vol 19 (5) ◽  
pp. 1313-1321
Author(s):  
Xuezhen Zhang ◽  
Aidi Huo ◽  
Jucui Wang
Keyword(s):  
Unsteady Flow ◽  
Water Absorption ◽  
Water Level ◽  
Steady Flow ◽  
Flow Injection ◽  
Absorption Capacity ◽  
Water Absorption Capacity ◽  
Analysis Method ◽  
Semi Empirical ◽  
Radial Well

Abstract In this paper, the theoretical basis for flow calculation in an injection well was discussed. It proposed that the flow rate of an injection well could be calculated referring to pumping theory and method. A mathematical model of the rising curve of water level around a radial well was established and the equation for calculating the rising curve was given. The calculation equations selected for the water absorption capacity of injection wells were explained and examples were verified and compared. The results indicated that, under the same injection conditions, the water level value calculated by the analysis method was slightly larger, but the error between the analysis method and the semi-theoretical and semi-empirical methods was small. In the processes of steady flow injection and unsteady flow injection, there was a small difference of water absorption capacity, and the former was slightly larger. The measured values of water absorption capacity were only about one-third of the calculated values based on pumping theory. Overall, the analytical solution method for predicting the rising curve of water level has priority in well injection. The semi-theoretical and semi-empirical equation for calculating water absorption capacity sifted first has priority in steady flow injection, the equation sifted second has priority in unsteady flow injection.

scholarly journals Active and Reactive Power Joint Balancing for Analyzing Short-Term Voltage Instability Caused by Induction Motor

Energies ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3617
Author(s):  
Ding Wang ◽  
Yangwu Shen ◽  
Zhen Hu ◽  
Ting Cui ◽  
Xiaoming Yuan
Keyword(s):  
Induction Motor ◽  
Reactive Power ◽  
Movement Direction ◽  
Analysis Method ◽  
Short Term ◽  
Voltage Instability ◽  
Operation Conditions ◽  
Active And Reactive Power ◽  
Acceleration And Deceleration ◽  
Power Balancing

Short-term voltage instability has a sensational effect once it occurs with massive loss of load, possibly area instability, and voltage collapse. This paper analyzes the short-term voltage instability caused by induction motor from the viewpoint of active and reactive power joint balancing. The analysis method is based on (1) the reactive power balancing between system supply and induction motor demand, and (2) the active power balancing between air-gap power and mechanical power, which is expressed by the region of rotor acceleration and deceleration in the Q-V plane. With the region of rotor acceleration and deceleration in the Q-V plane and the reactive power balancing, the movement direction of the operating point can be visually observed in the Q-V plane, thereby achieving a clear comprehension of physical properties behind the short-term voltage instability phenomenon. Furthermore, the instability mechanisms of two kinds of grid-connected induction motor operation conditions after a large disturbance are discussed to explain the basic theory of the analysis method and to provide examples of its application. Time-domain simulations are presented for a single-load infinite-bus system to validate the analyses.

Feasibility of an Isolated Reverse Turbine Concept for Marine Propulsion

1979 ◽  
Author(s):  
T. L. Bowen
Keyword(s):  
Gas Turbines ◽  
Axial Flow ◽  
Transient Behavior ◽  
Reduction Gear ◽  
Impulse Turbine ◽  
Stopping Distance ◽  
Turbine Performance ◽  
Marine Propulsion ◽  
Power Turbine ◽  
Performance Penalty

The feasibility of an isolated reverse turbine concept for marine propulsion was examined with emphasis on (1) the reverse turbine size needed to meet the stopping distance requirement of a particular ship during a crashback maneuver, and (2) the ahead turbine performance penalty due to reverse turbine windage losses. This particular reverse turbine system was made adaptable to the exhaust elbow and output shaft of an existing free-power-turbine gas turbine. The analysis was based on the application of this reverse turbine concept to a notational single-shaft frigate. The study-ship’s propulsion system includes two General Electric LM2500 gas turbines with reversing capability, a reduction gear, and a fixed-pitch propeller. A ship propulsion simulation was developed for the purpose of calculating steady-state ahead and backing performance data, as well as transient behavior of the ship during crashback maneuvers. The reverse turbine’s speed and torque required to stop the ship in five ship-lengths and 3.5 ship-lengths were determined from these calculations. Four reverse turbine designs were generated using a computer program for preliminary design of axial-flow turbines. The designs included a single-stage and a two-stage impulse turbine for both stopping distances. The penalty on ahead performance due to reverse turbine windage was estimated for each design, using existing experimental data found in the literature. The results obtained thus far tend to support the feasibility of this reverse turbine concept.

Truck Performance on Argentinean Highways

1996 ◽  
Vol 1555 (1) ◽  
pp. 114-123 ◽  
Author(s):  
Adrián Ricardo Archilla ◽  
Arístides Osvaldo Fernández de Cieza
Keyword(s):  
Field Data ◽  
The United States ◽  
Force Balance ◽  
Power Ratio ◽  
Ratio Distribution ◽  
Performance Curves ◽  
National Highway ◽  
Acceleration And Deceleration ◽  
Speed Prediction ◽  
Force Balance Equation

Truck performance observed on grades on National Highway 7 in Argentina is described. The observed weight-to-power ratio distribution in Argentina is shown to be considerably higher than that in North America. Also, a speed prediction model based on the simple force balance equation is fitted to the field data. The model explains about 80 percent of the observed variation, and for steep upgrades the predictions are similar to values observed in the United States. Acceleration and deceleration performance curves are also given. Finally, a validation of the model is presented by comparing the predicted and the observed speed profiles along two upgrades for trucks of known weight-to-power ratios. The shapes of the speed profiles predicted by the model closely replicate the observed speed profiles.

Unsteady Performance of a Double Entry Turbocharger Turbine With a Comparison to Steady Flow Conditions

2011 ◽  
Vol 134 (2) ◽  
Author(s):  
Colin D. Copeland ◽  
Ricardo Martinez-Botas ◽  
Martin Seiler
Keyword(s):  
Steady Flow ◽  
Flow Behavior ◽  
Turbine Rotor ◽  
Flow Conditions ◽  
Turbine Performance ◽  
Pulsed Flow ◽  
Performance Map ◽  
Engine Operating Condition ◽  
Double Entry ◽  
The Impact

Circumferentially divided, double entry turbocharger turbines are designed with a dividing wall parallel to the machine axis such that each entry feeds a separate 180 deg section of the nozzle circumference prior to entry into the rotor. This allows the exhaust pulses originating from the internal combustion exhaust to be preserved. Since the turbine is fed by two separate unsteady flows, the phase difference between the exhaust pulses entering the turbine rotor will produce a momentary imbalance in the flow conditions around the periphery of the turbine rotor. This research seeks to provide new insight into the impact of unsteadiness on turbine performance. The discrepancy between the pulsed flow behavior and that predicted by a typical steady flow performance map is a central issue considered in this work. In order to assess the performance deficit attributable to unequal admission, the steady flow conditions introduced in one inlet were varied with respect to the other. The results from these tests were then compared with unsteady, in-phase and out-of-phase pulsed flows most representative of the actual engine operating condition.

Quantitative Analysis of Gas Flow in a Planar SOFC

2012 ◽  
Vol 472-475 ◽  
pp. 2084-2087 ◽  
Author(s):  
Kai Wang ◽  
Yi Sheng Zhang ◽  
Jian Li
Keyword(s):  
Quantitative Analysis ◽  
Gas Flow ◽  
Three Dimensional ◽  
Analysis Method ◽  
Three Dimensional Model ◽  
Velocity Change ◽  
Gas Channel ◽  
Negative Effect ◽  
Quantitative Analysis Method ◽  
Cfd Method

Computational Fluid Dynamics (CFD) method was adopted to establish the three dimensional model for cathode gas channel of planar SOFC and simulate the gas flow in the channel of a single cell. A quantitative analysis method was presented to research the status of gas flow. The characteristics and diagram of velocity change were obtained by using the quantitative analysis method. Furthermore, it was found that gas leak has a negative effect on the uniformity of gas flow, which is more obvious in the region near the leak side.

Dynamic and Compliant Characteristics of a Cartesian-Guided Tripod Machine

2004 ◽  
Vol 128 (2) ◽  
pp. 494-502 ◽  
Author(s):  
Jeng-Shyong Chen ◽  
Wei-Yao Hsu
Keyword(s):  
High Speed ◽  
Degrees Of Freedom ◽  
Mechanical Vibration ◽  
Maximum Amplitude ◽  
High Gain ◽  
Velocity Change ◽  
Flexible Mode ◽  
Look Ahead ◽  
High Acceleration ◽  
Acceleration And Deceleration

This paper is focused on the dynamic and compliant characteristics of a three-axis parallel kinematic machine called a Cartesian-guided tripod (CGT), which has a passive leg locking the platform three rotational degrees of freedom. Because no constraint mechanism is perfect with infinite rigidity, a compliance model has been developed to determine the maximum amplitude of the passive-leg parasitic motions using given loads. System compliance, dynamic characteristics, vibration modes, and servo-contouring errors of the CGT driving system have also been evaluated under high-speed machining conditions. The nonlinear dynamic effects, such as inertia and gravity, can be controlled within acceptable accuracy using the high-gain servo-feedback control techniques. The CGT dominant flexible mode occurs on the horizontal platform-leg vibration. The platform-leg flexible mode can produce significant jerk-induced mechanical vibration on the platform when a sudden velocity change is commanded. Look-ahead Cartesian-based path acceleration and deceleration control was found to be an efficient tool to reduce the jerk-induced mechanical vibration, although the CGT was drive controlled at the joint level. It was found that at high acceleration application, such as high-speed mold and die machining, the elastic elongation of the driving leg caused by the high acceleration force became the dominant contouring error sources.

Unsteady Performance of a Double Entry Turbocharger Turbine With a Comparison to Steady Flow Conditions

2008 ◽  
Author(s):  
Colin D. Copeland ◽  
Ricardo Martinez-Botas ◽  
Martin Seiler
Keyword(s):  
Steady Flow ◽  
Turbine Rotor ◽  
Flow Conditions ◽  
Turbine Performance ◽  
Pulsed Flow ◽  
Performance Map ◽  
Unsteady Performance ◽  
Engine Operating Condition ◽  
Double Entry ◽  
The Impact

Circumferentially divided, double-entry turbocharger turbines are designed with a dividing wall parallel to the machine axis such that each entry feeds a separate 180° section of the nozzle circumference prior to entry into the rotor. This allows the exhaust pulses originating from the internal combustion exhaust to be preserved. Since the turbine is fed by two separate unsteady flows, the phase difference between the exhaust pulses entering the turbine rotor will produce a momentary imbalance in the flow conditions around the periphery of the turbine rotor. This research seeks to provide new insight into the impact of unsteadiness on turbine performance. The discrepancy between the pulsed flow behaviour and that predicted by a typical steady flow performance map is a central issue considered in this work. In order to assess the performance deficit attributable to unequal admission, the steady flow conditions introduced in one inlet were varied with respect to the other. The results from these tests were then compared to unsteady, in-phase and out-of-phase pulsed flow most representative of the actual engine operating condition.

3633 A study of a short time analysis method for mental stress by heart rate variability

2008 ◽  
Vol 2008.7 (0) ◽  
pp. 205-206
Author(s):  
Nobuaki MORI ◽  
Osamu SADA ◽  
Yoshiaki MATSUMOTO ◽  
Zhongwei JIANG
Keyword(s):  
Heart Rate ◽  
Heart Rate Variability ◽  
Mental Stress ◽  
Analysis Method ◽  
Time Analysis ◽  
Short Time
Sign in / Sign up

Export Citation Format

Share Document