Modeling of the Transient Response for Compressible Air Cushion Vehicles (ACV)

A model for compressible Air Cushion Vehicles (ACV) is presented. In this model the compressible Bernoulli's equation and the Newton's second law of motion are used to predict the dynamic behavior of the heave response of the ACV in both time and frequency domains. The mass flow rate inside the air cushion of this model is assumed to be constant. The self excited response and the cushion pressure of the ACV is calculated to understand the behavior of the system in order to assist in the design stage of such systems. It is shown in this study that the mass flow rate and the length of the vehicle's skirt are the most significant parameters which control the steady state behavior of the self excited oscillations of the ACV. An equation to predict the transient time of the oscillatory response or the settling time in terms of the system parameters of the ACV is developed. Based on the developed equations, the optimum parameters of the ACV that lead to minimum settling time are obtained.

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Modeling of the Heave and the Cushion Pressure of Air Cushion Landing System (ACLS): Chaotic Dynamics Investigation

Volume 4: Dynamics, Control and Uncertainty, Parts A and B ◽

10.1115/imece2012-89995 ◽

2012 ◽

Author(s):

Ahmed S. Sowayan

Keyword(s):

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Chaotic Behavior ◽

Equations Of Motion ◽

Vertical Motion ◽

State Behavior ◽

Bernoulli’S Equation ◽

Air Cushion ◽

Heave Motion

A theoretical model for the dynamics behavior of an incompressible Air Cushion Landing System (ACLS) is introduced. In this model the incompressible Bernoulli’s equation and the Newton’s second law of motion are used to predict the dynamic behavior of the heave (vertical response) of the ACLS in both time and frequency domains. The mass flow rate inside the air cushion of this model is assumed to be constant. The self excited response for the heave and the cushion pressure of the ACLS are calculated. In this study, the dimensionless mass flow rate and the dimensionless skirt of the ACLS’s skirt are the only parameters which are considered to be investigated to control the steady state behavior of the oscillatory motion of the ACLS. The equations of motion of the proposed nonlinear model are solved numerically using a code written on the Matlab software which is based on the Runge Kutta numerical integration method. The chaotic behavior of the heave motion and cushion pressure dynamics are investigated with the aid of the Fourier analysis and the Poincaré map. Periodic behavior is noticed in the vertical motion; on the other hand a chaotic behavior is manifest in the pressure inside the cushion volume of the ACLS. This model will help designers of the ACLS to understand the dynamics behavior of this system in order to redesign such system so that the violent oscillatory self excited motion can be reduced or eliminated.

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Aerodynamic Loss Increase due to Individual Film Cooling Injections From Gas Turbine Nozzle Surface

Volume 4: Heat Transfer; Electric Power; Industrial and Cogeneration ◽

10.1115/98-gt-497 ◽

1998 ◽

Cited By ~ 3

Author(s):

Ryo Kubo ◽

Fumio Otomo ◽

Yoshitaka Fukuyama ◽

Yuhji Nakata

Keyword(s):

Gas Turbine ◽

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Pressure Loss ◽

Rate Ratio ◽

Flow Rate Ratio ◽

Design Stage ◽

Pressure Side ◽

Mass Flow Rate Ratio

A CFD investigation was conducted on the total pressure loss variation for a linear nozzle guide vane cascade of a gas turbine, due to the individual film injections from the leading edge shower head, the suction surface, the pressure surface and the trailing edge slot. The results were compared with those of low speed wind tunnel experiments. A 2-D Navier-Stokes procedure for a 2-D slot injection, which approximated a row of discrete film holes, was performed to clarify the applicable limitation in the pressure loss prediction during an aerodynamic design stage, instead of a costly 3-D procedure for the row of discrete holes. In mass flow rate ratios of injection to main flow from 0% to 1%, the losses computed by the 2-D procedure agreed well with the experimental losses except for the pressure side injection cases. However, as the mass flow rate ratio was increased to 2.5%, the agreement became insufficient. The same tendency was observed in additional 3-D computations more closely modeling the injection hole shapes. The summations of both experimental and computed loss increases due to individual row injections were compared with both experimental and computed loss increases due to all-row injection with the mass flow rate ratio ranging from 0% to 7%. Each summation agreed well with each all-row injection result. Agreement between experimental and calculated results was acceptable. Therefore, the loss due to all-row injections in the design stage can be obtained by the correlations of 2-D calculated losses from individual row injections. To improve more precisely the summation prediction for the losses due to the present all-row injections, extensive research on the prediction for the losses due to the pressure side injection should be carried out.

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Flow Fields, Emission and Stabilization in Premixed Centrally-Staged Swirl Flames With Different Air Split Ratios

10.1115/gt2021-59061 ◽

2021 ◽

Author(s):

Tong Su ◽

Yuzhen Lin ◽

Chi Zhang ◽

Xiao Han

Keyword(s):

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Equivalence Ratio ◽

Flow Fields ◽

Design Stage ◽

Air Mass ◽

Split Ratio ◽

Flame Structures ◽

The Stability

Abstract The flow fields, emission levels, and static stability characteristics were investigated experimentally under various air split ratios (ASR, the ratio of the pilot stage air mass flow rate to the total air mass flow rate) at a fixed equivalence ratio of 0.8 of both main and pilot stages in a premixed centrally-staged swirl flame. The flame structures were captured by a CH* chemiluminescence high-speed camera and the corresponding results were processed by Abel deconvolution. Besides, the flow fields obtained by using planar Particle Image Velocimetry (PIV) technique were combined with flame structures to make a better study on the aerodynamic structures of the centrally-staged swirl flames. The emission levels of NOx and CO were measured by a gas analyzer. The stability boundaries and flame structures at different equivalence ratios under three ASRs were also studied. It is found that the size of the reacting primary recirculation zone (PRZ) becomes larger as more air is distributed to the pilot stage. This can be explained by the fact that the majority of the pilot fluid participates in the formation of the PRZ and also as a result of a stronger penetrability of the pilot jet. Moreover, the NOx emission levels increase while CO levels decrease, which is because of the longer residence time of the radicals within a larger PRZ and less impingement of the main flame on the combustor liner. Finally, the stability boundary is extended, and the total blowout equivalence ratio was decreased as the air split ratio increases, which demonstrates the flame stabilization effect of the pilot flame. In brief, the above findings can be a help to choose the appropriate air split ratio in the early design stage of the centrally-staged aero-engine combustors.

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Test stand for pulsed jet actuator command and characterization

Journal of Physics Conference Series ◽

10.1088/1742-6596/2130/1/012031 ◽

2021 ◽

Vol 2130 (1) ◽

pp. 012031

Author(s):

W Stryczniewicz ◽

W Stalewski

Keyword(s):

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Pressure Sensor ◽

Leading Edge ◽

Test Stand ◽

Design Stage ◽

Testing Procedures ◽

Pulsed Jet

Abstract The paper presents a test stand for characterization of a new design of a Pulsed Jet Actuator. The aim of the work was to characterize the performance of the PJA in terms of air parameters in the air supply line and velocity at the PJA outlet. To perform a detailed characterization of the system performance, the test bench comprised: a pressure reductor, a mass flow rate controller, a mass flow rate meter, a pressure sensor, a fast pressure sensor, a flow temperature sensor and a Constant Temperature Anemometer. The PJA was commanded by a real time controller with Field Programmed Gate Array architecture. The experimental results show good agreement with the results of Computational Fluid Dynamics simulations performed at the design stage of the PJA. It has been found that the flow parameters at the PJA nozzle outlet match the design goals. The developed bench testing procedures will be used for silent conditions tests of the PJA system integrated into a leading edge of a wind tunnel model.

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A Self-Starting Hydrodynamic Gas Bearing

Journal of Engineering for Industry ◽

10.1115/1.3428265 ◽

1972 ◽

Vol 94 (3) ◽

pp. 876-882

Author(s):

D. Molnar ◽

T. Ranov

Keyword(s):

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

The Self ◽

Air Supply ◽

Gas Bearing

An experimental self-starting hydrodynamic gas bearing was designed, built, and tested. This bearing operates on the principle that the bearing is started and stopped hydrostatically by means of an air supply which is generated by the bearing itself. For this purpose, a portion of the self-starting bearing is executed as a herringbone grooved bearing, which performs as a pump, charging a reservoir during hydrodynamic operation of the bearing. The reservoir air supply generated by the herringbone bearing is used for hydrostatic operation of the bearing during starts and stops. Starting and stopping of the experimental bearing was demonstrated using the air supply generated by the herringbone bearing. An equation was derived for the mass flow rate of the herringbone bearing pump.

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Features of a Cooling System Simulation Tool Used in Industrial Preliminary Design Stage

Volume 3: Turbo Expo 2004 ◽

10.1115/gt2004-53547 ◽

2004 ◽

Cited By ~ 11

Author(s):

Stefano Zecchi ◽

Lorenzo Arcangeli ◽

Bruno Facchini ◽

Daniele Coutandin

Keyword(s):

Heat Transfer ◽

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Cooling System ◽

Design Stage ◽

Preliminary Design ◽

Simulation Tool ◽

Cooling Systems ◽

Preliminary Design Stage

Due to expected increases in gas turbine performance, strictly related to firing temperature, heat transfer is a major issue in design processes. To keep components temperature levels below design requirements, cooling systems are commonly used. Nowadays, nozzle and blade cooling systems have reached a high degree of complexity. In a preliminary design stage, both experimental and 3D numerical analyses are usually not very suitable to define geometry, coolant mass flow rate or cooling system typology. This is mainly due to the uncertainty on several parameters, i.e. pressure distributions and materials properties, and their undefined interaction. This work presents a simulation tool useful to provide system cooling development with qualitative and quantitative information about metal temperature, coolant mass flow rate, heat transfer and much more. This tool couples energy, momentum and mass flow conservation equations together with experimental correlations for heat transfer and pressure losses. Metal conduction is solved by two dimensional calculations for several blade to blade sections. This methodology allows to investigate several cooling system configurations and compare them in a relatively short time. Main features of this simulation tool are shown comparing obtained results with experimental data.

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