The Choking Pressure Ratio of a Critical Flow Venturi

1975 ◽  
Vol 97 (4) ◽  
pp. 1251-1256 ◽  
Author(s):  
H. S. Hillbrath ◽  
W. P. Dill ◽  
W. A. Wacker
Keyword(s):  
Total Pressure ◽  
Gas Flow ◽  
Pressure Ratio ◽  
Critical Flow ◽  
Test Results ◽  
Flow Conditions ◽  
Pressure Losses ◽  
And Control ◽  
Measurement And Control ◽  
Effectiveness Parameter

The critical flow venturi has many important applications in the measurement and control of gas flow. In many of these applications, it is desirable to minimize the pressure loss required to maintain critical flow conditions. The performance of the venturi may be characterized by the ratio of outlet static pressure to inlet total pressure just sufficiently small to produce critical flow. This ratio is called choking pressure ratio (CPR). The optimization of diffusers for critical flow Venturis is discussed and suggestions for designs practice are presented. Test results are given for six different diffuser configurations, and a comparison is made with data on 11 configurations from other investigators. This work was done under contract to the National Aeronautics and Space Administration—Marshall Space Flight Center. It is shown that, for the small divergence angles considered, a simply defined diffuser effectiveness parameter is approximately independent of flow conditions and may be used to predict choking pressure ratio. Even very short diffusers greatly improve performance, and, for longer diffusers, critical flow can be maintained at total pressure losses of 5 percent.

Design and Test Results of a Ultra High Loaded Single Stage High Pressure Turbine

2013 ◽  
Author(s):  
Harjit S. Hura ◽  
Scott Carson ◽  
Rob Saeidi ◽  
Hyoun-Woo Shin ◽  
Paul Giel
Keyword(s):  
High Pressure ◽  
Total Pressure ◽  
High Speed ◽  
Pressure Ratio ◽  
Single Stage ◽  
Test Results ◽  
High Pressure Turbine ◽  
Technology Program ◽  
High Pressure Ratio ◽  
Expected Performance

This paper describes the engine and rig design, and test results of an ultra-highly loaded single stage high pressure turbine. In service aviation single stage HPTs typically operate at a total-to-total pressure ratio of less than 4.0. At higher pressure ratios or energy extraction the nozzle and blade both have regions of supersonic flow and shock structures which, if not mitigated, can result in a large loss in efficiency both in the turbine itself and due to interaction with the downstream component which may be a turbine center frame or a low pressure turbine. Extending the viability of the single stage HPT to higher pressure ratios is attractive as it enables a compact engine with less weight, and lower initial and maintenance costs as compared to a two stage HPT. The present work was performed as part of the NASA UEET (Ultra-Efficient Engine Technology) program from 2002 through 2005. The goal of the program was to design and rig test a cooled single stage HPT with a pressure ratio of 5.5 with an efficiency at least two points higher than the state of the art. Preliminary design tools and a design of experiments approach were used to design the flow path. Stage loading and through-flow were set at appropriate levels based on prior experience on high pressure ratio single stage turbines. Appropriate choices of blade aspect ratio, count, and reaction were made based on comparison with similar HPT designs. A low shock blading design approach was used to minimize the shock strength in the blade during design iterations. CFD calculations were made to assess performance. The HPT aerodynamics and cooling design was replicated and tested in a high speed rig at design point and off-design conditions. The turbine met or exceeded the expected performance level based on both steady state and radial/circumferential traverse data. High frequency dynamic total pressure measurements were made to understand the presence of unsteadiness that persists in the exhaust of a transonic turbine.

scholarly journals Prediction of Two-Phase Critical Flow Rate

1965 ◽  
Vol 87 (1) ◽  
pp. 53-57 ◽  
Author(s):  
S. Levy
Keyword(s):  
Flow Rate ◽  
Thermal Equilibrium ◽  
Present Model ◽  
Critical Flow ◽  
Test Results ◽  
Two Phase ◽  
Mean Velocity ◽  
Critical Flow Rate ◽  
Pressure Losses ◽  
Gas Void Fraction

An analytical model to predict two-phase critical flow rate is proposed. The model is based upon thermal equilibrium, a “lumped” treatment of the two-phase velocity (each phase is represented by a single mean velocity), and upon the neglect of frictional and hydrostatic pressure losses. A comparison of the proposed predictions with available test results and previous analyses shows that: (a) The present model agrees very well with the published test data; (b) In contrast to all other analyses, the model requires no assumption about the gas void fraction.

Research on Channel Equipment Reliability Analysis Methods of Measurement and Control System of Ship-Borne

2013 ◽  
Vol 765-767 ◽  
pp. 2057-2060
Author(s):  
Si Fang Liu ◽  
Jiu Lin Guo ◽  
Jian Hong Xu ◽  
Hong Qiang Guo
Keyword(s):  
Control System ◽  
Power Level ◽  
Signal Power ◽  
Test Results ◽  
Mathematical Methods ◽  
Measurement And Control System ◽  
Equipment Reliability ◽  
And Control ◽  
Measurement And Control ◽  
Methods Of Measurement

Aiming at the feature of failure occurs frequently, check links, difficult to position for channel equipment of measurement and control system of the ship-borne, according as to equipment index that reflects equipment performance-signal power level, analyzes channel equipment reliability by different mathematical methods, and based on the previous equipment test results of data analysis, presents the method of wavelet neural network, to analyze equipment reliability and forecast malfunction .

Effect of a volute on the unsteady flow in the vane diffuser of a centrifugal compressor

2016 ◽  
Vol 230 (8) ◽  
pp. 773-791 ◽  
Author(s):  
Gong W Qi ◽  
X Hong Zhang
Keyword(s):  
Mass Flow ◽  
Centrifugal Compressor ◽  
Total Pressure ◽  
Pressure Ratio ◽  
Operating Conditions ◽  
High Mass ◽  
Flow Conditions ◽  
Asymmetric Component ◽  
Unsteady Loading ◽  
Vane Diffuser

A volute is the only circumferential asymmetric component in a centrifugal compressor, and thus, it should account for the circumferential asymmetry of the flow in a vane diffuser. This study performs a transient numerical analysis to investigate the effect of a volute on the flow in the vane diffuser of a centrifugal compressor under three operating conditions (near-stall, middle, and high mass flow). We compare numerical and experimental performance of the compressor, including polytropic efficiency, total pressure ratio, and unsteady pressure on a diffuser vane. The numerical scheme is proven valid owing to the fact that the numerical and experimental results considerably agree well with each other. Under middle and high mass flow conditions, the time-averaged static pressure recovery and the total pressure loss coefficients for all the diffuser passages indicate that the performance of the passages near and upstream of the volute tongue is affected negatively by the volute, whereas that of the passages downstream of the volute tongue is less affected. Under near-stall condition, the performance of all the passages is disturbed, and the diffuser passage marked as DP 3 demonstrates the worst performance. Investigation on the time-averaged aerodynamic forces, loading, and pressure on the vanes yields results that are consistent with those of the investigation on the performance of the passages. The harmonics with 0.5 fb and fb, which are included in the unsteady loading and pressure on the pressure and suction sides of the vanes, are dominant, where fb is the impeller main and splitter blades passing frequency. Their amplitude values increase as mass flow deviates from the middle mass flow condition. Under middle and high mass flow conditions, the harmonic with 0.5 fb is affected more negatively because of the larger amplitude on the vanes near and upstream of the volute tongue than those downstream, whereas the harmonic with fb is less affected by the volute. Under the near-stall condition, the transient vorticity fields along with the harmonics of 0.5 fb and fb are investigated to evaluate the performance of the diffuser passages. DP 3, which is located at approximately 90° downstream of the volute tongue, suffers the strongest flow deterioration and is inferred to stall first. Further researches for designing more matching diffuser/volute combination will be performed by referring this study.

A Method for Predicting Compressor Cascade Total Pressure Losses When the Inlet Relative Mach Number Is Greater Than Unity

1971 ◽  
Vol 93 (1) ◽  
pp. 119-124 ◽  
Author(s):  
R. L. Balzer
Keyword(s):  
Total Pressure ◽  
Axial Flow ◽  
Shock Formation ◽  
Flow Conditions ◽  
Compressor Cascade ◽  
Viscous Effects ◽  
Pressure Losses ◽  
The Past ◽  
Flow Compressor ◽  
Made In

During the last few years, considerable progress has been made in predicting the total pressure losses from viscous effects for axial-flow compressor cascades. With the advent of the transonic and the supersonic stage, another pressure loss generating mechanism was introduced—the shock wave. Various methods have been published over the past few years accounting for the pressure losses associated with the shock formation, but of those reviewed by this author, none of them has been consistently successful for predicting the losses at other than design conditions. This paper develops a method which has given consistent success at all flow conditions for compressors with subsonic axial and supersonic relative velocities.

Research on the ECAS System Model and Control Strategy

2013 ◽  
Vol 419 ◽  
pp. 654-660
Author(s):  
Xi Jin Zhang ◽  
Hong Yan Li ◽  
Zong De Fang ◽  
Mao Ting Wang ◽  
Jing Wen Pan ◽  
...  
Keyword(s):  
Control Method ◽  
Digital Simulation ◽  
Test Results ◽  
Test Bed ◽  
Air Spring ◽  
Measurement And Control System ◽  
Height Control ◽  
Car Model ◽  
And Control ◽  
Measurement And Control

Tractor SX4187NT361K, which is manufactured by the Shaanxi Automobile Group Limited Corporation, is regarded as a prototype vehicle. This paper investigates an 1/4 car model with air springs for the tractor and a working model of air spring. A height PID control method for ECAS is designed, and its digital simulation is conducted. An ECAS test-bed is designed, and hardware of a measurement and control system for the test-bed is designed with DSPACE system, its softwares are also designed with Simulink and ControlDesk. Finally, active and passive tests of the ECAS are conducted through changing frequencies and desired heights, simulation and test results show that the PID height control method for ECAS is feasible.

scholarly journals NUMERICAL STUDY OF THE EXHAUST GAS FLOW OF TV3-117 TYPE ENGINES IN COMPOSITION WITH A SCREEN - EXHAUST DEVICE

ScienceRise ◽  
2020 ◽  
Vol 4 ◽  
pp. 17-23
Author(s):  
Mykhailo Kinaschuk
Keyword(s):  
Total Pressure ◽  
Gas Flow ◽  
Numerical Study ◽  
Experimental Studies ◽  
Flow Path ◽  
Constructive Method ◽  
Pressure Losses ◽  
Gas Dynamic ◽  
Scientific Results ◽  
Separation Zones

The object of research is a screen-exhaust device in the TV3-117 engine of the Mi-8 helicopter. Investigated problem: The problem of equalizing the flow in the exhaust nozzle is solved. As a result of the numerical study, the total pressure losses are calculated and the flow structures in the structural elements of the exhaust nozzle and the screen-exhaust device (SED) are analyzed. Main scientific results: Obtained Gas-dynamic parameters of the flow in the SED flow path are obtained and the verification of injection processes between the working circuits along the path in the SED design is done. Numerical modeling of gas flows in the SED flow path makes it possible to study in detail the characteristics of the flow at any of its points, as well as to determine the values of hydrodynamic losses associated with the formation of a boundary layer and the emergence of separation zones. A constructive method for leveling the gas-dynamic flow is proposed by installing a blade in the form of an aerodynamic profile in a standard engine exhaust nozzle. Two variants of engine nozzles are investigated under the same boundary conditions using a standard exhaust nozzle with and without a blade. The influence of uneven flow in the exhaust nozzle on the nature of the flow in the SED is shown. An insignificant equalization of the flow in the exhaust nozzle using the installed blade led to a decrease in the total pressure loss in the SED by more than 1 %. The area of practical use of the research results: The results of calculations and modeling can be used for computational and experimental studies aimed at improving the flow path of the exhaust nozzle and the screen-exhaust device by the developers of new military aviation equipment or when modernizing the existing helicopter fleet. Scope of application of the innovative technological product: a new screen-exhaust device has been proposed for left and right TV3-117 engines of all types, which can be installed on the Mi-8MSB-V, Mi-8MT, Mi-14, Mi-24 helicopters. It is competitive and has significantly higher technical and economic indicators compared to known analogues.

Experiments of Liquid Loading and Intermittent Production Using a Lab-Scale Reservoir-Tubing Setup

2021 ◽  
Author(s):  
Jos van 't Westende ◽  
Dries van Nimwegen ◽  
Stefan Belfroid ◽  
Harmen Slot
Keyword(s):  
Total Pressure ◽  
Gas Flow ◽  
Experimental Setup ◽  
Reservoir Model ◽  
Liquid Loading ◽  
Flow Rates ◽  
Pressure Losses ◽  
Set Up ◽  
Start Ups ◽  
Production Tubing

Abstract Experiments were performed to investigate the physics behind intermittent production and liquid loading, using a setup containing a reservoir model coupled to a vertical production tubing. In the experiments both gas and liquid are injected into the reservoir, which is a container in which sand with two different permeabilities is placed. Quick closing valves are incorporated into the experimental setup in order to simulate well shut-ins and start-ups. The experimental results show that the addition of the reservoir to the experimental set-up shifts the minimum in the total pressure losses over the system to lower gas flow rates as the permeability of the reservoir decreases. When performing shut-ins where a significant liquid column is present in the tubing, as is the case in liquid loaded wells, performing a sufficiently long shut-in can lead to the deliquification of the system.

Two-Phase, Two-Component Critical Flow in a Venturi

1972 ◽  
Vol 94 (1) ◽  
pp. 147-151 ◽  
Author(s):  
R. V. Smith
Keyword(s):  
Gas Phase ◽  
Gas Flow ◽  
Critical Flow ◽  
Flow Conditions ◽  
Transfer Coefficients ◽  
Two Phase ◽  
One Dimensional ◽  
Flow Equations ◽  
Heat Transfer Coefficients ◽  
Wide Range

This paper reports the results of an analytical and experimental investigation whose object was to test the hypothesis that the flow of the gas phase controls critical and near critical two-phase flow for cases where the gas flow is essentially in separate streams. The results substantiate the hypothesis. The analytical results also indicate that one dimensional flow equations with reasonably accurate estimates for the droplet size and for the drag and heat transfer coefficients will adequately describe critical and near critical flow over a wide range of flow conditions.

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