scholarly journals X-Ray Measurements in a Cavitating Centrifugal Pump During Fast Start-Ups

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
S. Duplaa ◽  
O. Coutier-Delgosha ◽  
A. Dazin ◽  
G. Bois
Keyword(s):  
Centrifugal Pump ◽  
Rocket Engine ◽  
Transient Behavior ◽  
Operating Conditions ◽  
Centrifugal Impeller ◽  
X Ray ◽  
Speed Increase ◽  
Start Up ◽  
Fast Start ◽  
Start Ups

The start-up of rocket engine turbopumps is generally performed in a few seconds or even less. It implies that these pumps reach their nominal operating conditions after a few rotations only. During the start-up, the flow evolution within the pump is governed by transient phenomena, based mainly on the flow rate and rotation speed increase. Significant pressure fluctuations, which may result in the development of cavitation, are observed. A centrifugal impeller whose transient behavior during start-ups has been detailed in a previous publication is considered. Three different cases of fast start-ups have been identified according the final operating point (Duplaa et al., 2010, “Experimental Study of a Cavitating Centrifugal Pump During Fast Start-Ups,” ASME J. Fluids Eng., 132(2), p. 021301). The aim of this paper is to analyze the evolution during the start-ups of the local amount of vapor in the blade to blade channels of the pump by fast X-ray imaging. This technique has enabled to calculate the time-evolution of the fluid density within the pump, which appears to be correlated with pressure time-evolutions. For each investigated start-up, X-ray measurements have been performed at three different sections of the impeller height. For each investigated start-up and section tested, measurements have been performed for several initial positions of the impeller, to estimate the measurement uncertainty, and to obtain records from different beam angles, like in tomography.

scholarly journals Experimental Study of a Cavitating Centrifugal Pump During Fast Startups

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
S. Duplaa ◽  
O. Coutier-Delgosha ◽  
A. Dazin ◽  
O. Roussette ◽  
G. Bois ◽  
...  
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Transient Flow ◽  
Flow Behavior ◽  
Rocket Engine ◽  
Rotation Velocity ◽  
Transient Behavior ◽  
Operating Conditions ◽  
Physical Analysis ◽  
Different Types

The startup of rocket engine turbopumps is generally performed only in a few seconds. It implies that these pumps reach their nominal operating conditions after only a few rotations. During these first rotations of the blades, the flow evolution in the pump is governed by transient phenomena, based mainly on the flow rate and rotation speed evolution. These phenomena progressively become negligible when the steady behavior is reached. The pump transient behavior induces significant pressure fluctuations, which may result in partial flow vaporization, i.e., cavitation. An existing experimental test rig has been updated in the LML Laboratory (Lille, France) for the startups of a centrifugal pump. The study focuses on the cavitation induced during the pump startup. Instantaneous measurement of torque, flow rate, inlet and outlet unsteady pressures, and pump rotation velocity enable to characterize the pump behavior during rapid starting periods. Three different types of fast startup behaviors have been identified. According to the final operating point, the startup is characterized either by a single drop of the delivery static pressure, by several low-frequency drops, or by a water hammer phenomenon that can be observed in both the inlet and outlet of the pump. A physical analysis is proposed to explain these three different types of transient flow behavior.

Experimental Study of the Flow in the Suction Pipe of a Centrifugal Pump at Partial Flow Rates in Unsteady Conditions

1999 ◽  
Vol 121 (3) ◽  
pp. 291-295 ◽  
Author(s):  
S. Bolpaire ◽  
J. P. Barrand
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Static Pressure ◽  
Pressure Measurements ◽  
Flow Rates ◽  
Suction Pipe ◽  
Start Up ◽  
Test Loop ◽  
Fast Start ◽  
Operational Range

The operational range and the performances of pumps are limited by the occurrence of backflow and prerotation in the suction pipe as the flow rate is reduced. This paper presents the study of static pressure measurements and visualizations in the suction pipe, near the inlet of a centrifugal pump, at partial flow rates, in steady conditions, and during a fast start-up of the pump. The tests were carried out in water on the DERAP© test loop of the ENSAM Lille laboratory. Standard methods allowed to determine the recirculation critical flow rate. A visualization method showed that the axial extent of the recirculation and the prerotation with the flow rate is considerably reduced during a fast start-up compared to steady conditions.

scholarly journals Preheating procedure for fast start-up of a steam turbine from a cold state

2019 ◽  
Vol 137 ◽  
pp. 01024
Author(s):  
Wojciech Kosman ◽  
Andrzej Rusin
Keyword(s):  
Steam Turbine ◽  
Thermal State ◽  
Initial Period ◽  
Electric Heater ◽  
Cold State ◽  
Hot Air ◽  
Start Up ◽  
Maximal Stress ◽  
Fast Start ◽  
Start Ups

The paper describes a procedure that allows to start up a steam turbine in a significantly shorter period. The procedure is developed for start-ups that begin from a cold state, when the temperature of the parts of the turbine is close to the ambient temperature. The pre-heating rises the parts temperature before the actual start-up begins. It changes the thermal state of the turbine and causes smaller maximal stress during the initial period of the start-up. The procedure involves a pre-heating of the turbine with a hot air generated in an electric heater. The paper describes the requirements of the process. It presents the possible configurations of the flow in the turbine and the analysis of the thermal and the strength state of the turbine during the pre-heating.

Transient Behavior of the Gallium Nitride Chemical Vapor Deposition Process

2013 ◽  
Author(s):  
Jiandong Meng ◽  
Yogesh Jaluria
Keyword(s):  
Gallium Nitride ◽  
Operating Time ◽  
Chemical Vapor ◽  
Transient Behavior ◽  
Deposition Process ◽  
Input Power ◽  
Operating Conditions ◽  
Start Up ◽  
Flow Heat ◽  
Dependent Transport

The transient behavior of the Gallium Nitride deposition process in a CVD reactor is numerically investigated. A two-dimensional impinging reactor is considered to examine the time-dependent transport in the MOCVD process, including the steady-state deposition process, and the system start-up and shut-down. The study involves the consideration of complicated transport phenomena, including fluid flow, heat and mass transfer, and chemical reactions between the reactants and the intermediate species. The temperature field and the deposition rate are studied as functions of time, as well as the precursor mass fraction at certain times. The results obtained provide an in-depth understanding about the entire MOCVD process, and the possibility to control the system operating time and the consumption of input power and precursors, which are generally quite expensive. It also provided inputs on the effects of changing operating conditions and the duration of starting and shut down effects.

Transient Loading Improvements for Large Steam-Electric Generating Units

1962 ◽  
Vol 84 (1) ◽  
pp. 9-20
Author(s):  
Charles Strohmeyer
Keyword(s):  
Operating Conditions ◽  
Steam Temperature ◽  
Turbine Generator ◽  
Supervisory System ◽  
Low Pressure Turbine ◽  
Start Up ◽  
Temperature And Pressure ◽  
Start Ups ◽  
Full Pressure ◽  
Turbine Exhaust

The intent of this paper is to discuss the ultimate in operating flexibility during transient conditions that can be built into new designs having steam conditions of 2400 psig, 1050/1000 F reheat or above. The following discussion proposes an over-all operating philosophy in the hope of developing better understanding among the engineers, operators, and equipment manufacturers. Emphasis is placed upon steam temperature control to suit various turbine operating conditions. New methods proposed include a means of raising throttle steam enthalpy during hot turbine starts, a control and/or supervisory system for regulating unit start-ups and shutdowns, and a new means of cooling the low pressure turbine exhaust during start-up. As a result, for short duration turbine generator shutdowns as 8 hours, units may be unloaded rapidly at full pressure and in some cases may be restarted from turning gear to one third load restoring design primary steam temperature and pressure in as little as 35 minutes without sacrifice of safety.

Transient Behavior of a Cavitating Centrifugal Pump at Rapid Change in Operating Conditions—Part 1: Transient Phenomena at Opening/Closure of Discharge Valve

1999 ◽  
Vol 121 (4) ◽  
pp. 841-849 ◽  
Author(s):  
T. Tanaka ◽  
H. Tsukamoto
Keyword(s):  
Centrifugal Pump ◽  
High Speed ◽  
Rapid Change ◽  
Transient Behavior ◽  
Video Camera ◽  
Operating Conditions ◽  
Centrifugal Pumps ◽  
Transient Period ◽  
Discharge Valve ◽  
Cavitation Behavior

A series of studies on the dynamic characteristics of noncavitating centrifugal pumps were extended to the cavitating case. An experimental study was carried out on the transient behavior of a cavitating centrifugal pump at the sudden opening/closure of the discharge valve. Cavitation behavior in the centrifugal pump was visualized during the transient period by using high speed video camera, and instantaneous pressure and flowrate were measured at the pump suction and discharge section with rotational speed during the transient period. Unsteady pressure, as well as flowrate, was related to the time-dependent cavitation behavior. As a result of the present study, pressure and flowrate fluctuations were found to occur due to oscillating cavitation or water column separation at rapid transient operations.

Transient Behavior of a Cavitating Centrifugal Pump at Rapid Change in Operating Conditions—Part 3: Classifications of Transient Phenomena

1999 ◽  
Vol 121 (4) ◽  
pp. 857-865 ◽  
Author(s):  
T. Tanaka ◽  
H. Tsukamoto
Keyword(s):  
Water Column ◽  
Centrifugal Pump ◽  
Rapid Change ◽  
Transient Behavior ◽  
Operating Conditions ◽  
Critical Conditions ◽  
Pump System ◽  
Column Separation ◽  
Cavitation Bubbles ◽  
Flow Mechanisms

Analytical studies were developed on the transient behavior of a cavitating centrifugal pump during the transient operations, including the sudden opening/closure of the discharge valve and the pump startup/shutdown. In order to investigate the mechanism of the low cycle oscillations of both the pressure and the flowrate at a rapid change of the pump system conditions, an unsteady flow analysis was made for the cavitating pump-system by assuming the transient pump performance to be quasi-steady. The calculated unsteady pressure and flowrate during the transient period agree with the corresponding measured time histories. It is shown that the fluctuations of delivery pressure and discharge flowrate at pump rapid startup or sudden valve opening are caused by peculiar oscillating cavitation dynamics inside the pump at rapid increase in flowrate, while the fluctuations at pump rapid shutdown or sudden valve closure are related to the collapse of cavitation bubbles or water column separation in the suction pipe at rapid decrease in flowrate. Moreover, the occurrence of transient fluctuations in pressure and flowrate was predicted by examining the critical condition which creates the occurrence of two different flow mechanisms i.e., (A) oscillating cavitation and (B) water column separation including also the collapse of the cavitation bubbles. These flow mechanisms were represented with two flow models i.e., (A) unsteady cavitating flow incorporating effects of cavitation compliance and mass flow gain factor and expressed by a set of ordinary differential equations solved with the Cardano Method and (B) water-hammer type model including Discrete Free Gas Model and solved with method of characteristics. The calculated critical conditions for the occurrence of the oscillating cavitation and water column separation agree qualitatively with measured ones.

scholarly journals Study on inducer and impeller of a centrifugal pump for a rocket engine turbopump

2012 ◽  
Vol 227 (2) ◽  
pp. 311-319 ◽  
Author(s):  
Soon-Sam Hong ◽  
Dae-Jin Kim ◽  
Jin-Sun Kim ◽  
Chang-Ho Choi ◽  
Jinhan Kim
Keyword(s):  
Centrifugal Pump ◽  
Performance Test ◽  
Rocket Engine ◽  
Water Environment ◽  
Centrifugal Impeller ◽  
Liquid Rocket Engine ◽  
Cavitation Performance ◽  
Liquid Rocket ◽  
Critical Cavitation ◽  
Flow Interference

A hydraulic performance test is conducted for a fuel pump of a liquid rocket engine turbopump. The pump driven by an electric motor is tested in a water environment. Experimental results indicate that the inducer has a negligible effect on the head and efficiency of the pump but a significant effect on the cavitation performance. Additionally, an autonomous inducer test is carried out to investigate the effect of the inducer on the pump performance in more detail, and it is found out that the pump reaches a critical cavitation point when the inducer head is dropped by 55%. A reduction of required net positive suction head of the centrifugal pump by attachment of an inducer is also calculated considering the flow interference between the inducer and the centrifugal impeller, and it is found that the calculation shows a reasonable agreement with the test.

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