Pressure-Gain Combustion: Part II—Experimental and Model Results

1996 ◽  
Vol 118 (3) ◽  
pp. 469-473 ◽  
Author(s):  
G. A. Richards ◽  
R. S. Gemmen
Keyword(s):  
Control Volume ◽  
Operating Conditions ◽  
Volume Analysis ◽  
Pulse Combustor ◽  
Model Predictions ◽  
Pressure Gain Combustion ◽  
Mean Pressure ◽  
Pulse Combustion ◽  
Complex Fluid ◽  
Geometric Changes

An experimental investigation of aerovalve pulse combustion is presented. The experimental measurements compare favorably with model predictions from a control volume analysis of the pulse combustor. Particular emphasis is placed on the mean pressure differences through the combustor as an indicator of the so-called pressure gain performance. Both the operating conditions and combustor geometry are investigated. It is shown that complex fluid/combustion interactions within the combustor make it difficult to isolate the effect of geometric changes. A scaling rule developed from the control-volume analysis is used to produce a combustor geometry capable of producing pressure gain.

Pressure-Gain Combustion: Part I—Model Development

1996 ◽  
Vol 118 (3) ◽  
pp. 461-468 ◽  
Author(s):  
L. Narayanaswami ◽  
G. A. Richards
Keyword(s):  
Control Volume ◽  
Model Development ◽  
Combustion Products ◽  
Bimolecular Reaction ◽  
Operating Pressure ◽  
Pulse Combustor ◽  
Pressure Gain Combustion ◽  
Pulse Combustion ◽  
Model Equations ◽  
Fresh Charge

A model for aerodynamically valved pulse combustion is presented. Particular emphasis is placed on using the model equations to identify characteristic length and time scales relevant to the design of pressure-gain combustors for gas turbine applications. The model is a control volume description of conservation laws for several regions of the pulse combustor. Combustion is modeled as a bimolecular reaction. Mixing between the fresh charge and the combustion products is modeled using a turbulent eddy time estimated from the combustor geometry and flow conditions. The model equations identify two characteristic lengths, which should be held constant during combustor scaleup, as well as certain exceptions to this approach. The effect of ambient operating pressure and inlet air temperature is also discussed.

An Analytical Approach to Understanding the “Pressure Gain” Combustor

1997 ◽  
Vol 119 (1) ◽  
pp. 49-54 ◽  
Author(s):  
M. C. Janus ◽  
G. A. Richards ◽  
R. S. Gemmen ◽  
E. K. Johnson
Keyword(s):  
Combustion Process ◽  
Stagnation Pressure ◽  
Pollutant Emissions ◽  
Primary Concern ◽  
One Dimensional ◽  
Pulse Combustor ◽  
Pressure Gain Combustion ◽  
Pulse Combustion ◽  
Commercial Applications ◽  
Made In

Although pulse combustion has been successfully utilized in various commercial applications, one potential application yet to reach the market is the pressure gain gas turbine (PGGT). A PGGT would incorporate a pulse combustor rather than the typical steady-flow combustor to increase system efficiency and decrease pollutant emissions. The distinctive advantage of pulse combustion is its ability to achieve a stagnation “pressure gain” from inlet to exit. A primary concern with pressure gain combustion development, however, is the lack of understanding as to how a combustor should be designed to achieve a pressure gain. While significant progress has been made in understanding the fundamental controlling physics of pulse combustor operation, little research has been aimed at understanding and predicting whether a given system will produce pressure gain. The following paper proposes a simple framework which helps to explain how a pulse combustor achieves a stagnation pressure gain from inlet to exit. The premise behind the framework is that pressure gain can be achieved by closely approximating a constant volume combustion process, is closely approximated by matching the resonant and operating frequencies of the system. The framework is primarily based upon results from a one-dimensional method-of-characteristics model.

Character and Behavior of Mist Generated by Application of Cutting Fluid to a Rotating Cylindrical Workpiece, Part 1: Model Development

2004 ◽  
Vol 126 (3) ◽  
pp. 417-425 ◽  
Author(s):  
Y. Yue ◽  
J. Sun ◽  
K. L. Gunter ◽  
D. J. Michalek ◽  
J. W. Sutherland
Keyword(s):  
Control Volume ◽  
Film Theory ◽  
Model Development ◽  
Cutting Speed ◽  
Droplet Size Distribution ◽  
Rotating Disk ◽  
Operating Conditions ◽  
Cutting Fluid ◽  
Model Predictions ◽  
Cylindrical Workpiece

Increasing attention is being devoted to the airborne emissions resulting from a variety of manufacturing processes because of health, safety, and environmental concerns. In this two-part paper, a model is presented for the amount of cutting fluid mist produced by the interaction of the fluid with the rotating cylindrical workpiece during a turning operation. This model is based on relationships that describe cutting fluid atomization, droplet settling, and droplet evaporation. Experiments are performed to validate the model. In Part 1 of the paper, the emphasis is on model development. In the model, thin film theory is used to determine the maximum fluid load that can be supported by a rotating cylindrical workpiece; rotating disk atomization theory is applied to the turning process to predict the mean size of the droplets generated by atomization; and expressions for both the evaporation and settling behavior are established. Droplet size distribution and mass concentration predictions are used to characterize the fluid mist. Model predictions indicate that the droplet mean diameter is affected by both fluid properties and operating conditions, with cutting speed having the most significant affect. Model predictions and experimental results show that the number distribution of droplets within the control volume is dominated by small droplets because of the settling and evaporation phenomena. In Part 2 of the paper, the cutting fluid mist behavior model is validated using the results obtained from a series of experiments.

Numerical prediction of the performance of gas-lubricated spiral groove thrust bearings

1997 ◽  
Vol 211 (2) ◽  
pp. 117-128 ◽  
Author(s):  
Y Yue ◽  
T. A. Stolarski
Keyword(s):  
Control Volume ◽  
Numerical Procedure ◽  
Operating Conditions ◽  
Hydrodynamic Bearings ◽  
Thrust Bearings ◽  
Flow Balance ◽  
Control Volumes ◽  
Volume Method ◽  
Spiral Angle ◽  
Spiral Grooves

The objective of this paper is to develop an accurate numerical procedure for the analysis of nominally flat contacts with spiral grooves lubricated by gases. The numerical procedure, which is based on the control-volume method, enables the solutions of the non-linear Reynolds equation to be obtained without limitation in geometry and operating conditions. Satisfactory flow balance was achieved on the control volumes as well as on the whole boundary and the method was proved to be very accurate. Convergence of the method was quick for any compressibility number. Three types of contact with spiral grooves were analysed. They were hydrodynamic bearings without interior chambers, hydrodynamic bearings with interior chambers and hybrid bearings. The effects of spiral angle, groove geometry (length, depth and width) and compressibility on performances were investigated for all possible designs.

Optical Analysis of Pulse Combustion Using Shadowgraph and Planar CH-LIF Imaging Technique

2000 ◽  
Vol 123 (1) ◽  
pp. 59-63 ◽  
Author(s):  
Yojiro Ishino ◽  
Tatsuya Hasegawa ◽  
Shigeki Yamaguchi ◽  
Norio Ohiwa
Keyword(s):  
Large Scale ◽  
Ccd Camera ◽  
Pulsation Period ◽  
Planar Imaging ◽  
Camera System ◽  
Band Emission ◽  
Pulse Combustor ◽  
Pulse Combustion ◽  
Combustion Processes ◽  
Ch Radical

Planar imaging of laser-induced fluorescence of CH radical is made to examine combustion processes in a valveless pulse combustor. An excimer-pumped dye laser tuned to a wavelength of 387 nm is used to excite the R1N″=6 line of (0,0) band of the B2Σ−−X2Π system of CH radical, and an image-intensified CCD camera system is used to detect the (0,1) band emission at around 435 nm. According to the CH-LIF images, it is found that the progress in combustion during a pulsation period is expressed by the enlargement and breakup of the earlobe-shaped flame front along the outline of a pair of large-scale eddies of fresh mixture.

On symmetric intrusions in a linearly stratified ambient: a revisit of Benjamin's steady-state propagation results

2021 ◽  
Vol 929 ◽  
Author(s):  
M. Ungarish
Keyword(s):  
Steady State ◽  
Control Volume ◽  
Gravity Current ◽  
Head Loss ◽  
Stability Criteria ◽  
Ambient Fluid ◽  
Height Ratio ◽  
Stagnation Line ◽  
Volume Analysis ◽  
State Propagation

Previous studies have extended Benjamin's theory for an inertial steady-state gravity current of density $\rho _{c}$ in a homogeneous ambient fluid of density $\rho _{o} < \rho _{c}$ to the counterpart propagation in a linearly stratified (Boussinesq) ambient (density decreases from $\rho _b$ to $\rho _{o}$ ). The extension is typified by the parameter $S = (\rho _{b}-\rho _{o})/(\rho _{c}-\rho _{o}) \in (0,1]$ , uses Long's solution for the flow over a topography to model the flow of the ambient over the gravity current, and reduces well to the classical theory for small and moderate values of $S$ . However, for $S=1$ , i.e. $\rho _b = \rho _c$ , which corresponds to a symmetric intrusion, various idiosyncrasies appear. Here attention is focused on this case. The control-volume analysis (balance of volume, mass, momentum and vorticity) produces a fairly compact analytical formulation, pending a closure for the head loss, and subject to stability criteria (no inverse stratification downstream). However, we show that plausible closures that work well for the non-stratified current (like zero head loss on the stagnation line, or zero vorticity diffusion) do not produce satisfactory results for the intrusion (except for some small ranges of the height ratio of current to channel, $a = h/H$ ). The reasons and insights are discussed. Accurate data needed for comparison with the theoretical model are scarce, and a message of this paper is that dedicated experiments and simulations are needed for the clarification and improvement of the theory.

Injection Pump Analysis

2012 ◽  
Author(s):  
William W. Schultz ◽  
Eric Johnsen ◽  
Bosuk Han ◽  
Sung Park
Keyword(s):  
Control Volume ◽  
Optimal Performance ◽  
Device Performance ◽  
Volume Analysis ◽  
Injection Pump ◽  
Simple Geometry ◽  
Simplified Analysis ◽  
Moving Parts

An injection pump is one of the simplest mechanics devices imaginable with no moving parts and a very simple geometry. We examine the device performance for steam injectors using primarily a control volume analysis and consider to what extent this simplified analysis represents optimal performance. We seek the rationale for performing CFD studies and develop optimization scenarios.

scholarly journals Lift force for cylindrical and elliptical Coandă aircraft design

2018 ◽  
Vol 7 (4.13) ◽  
pp. 137
Author(s):  
Mohd Faisal Abdul Hamid ◽  
Azmin Shakrine Mohd Rafie ◽  
Ezanee Gires ◽  
Abd. Rahim Abu Talib
Keyword(s):  
Lift Force ◽  
Control Volume ◽  
Aircraft Design ◽  
The Body ◽  
Viscous Effect ◽  
Extended Version ◽  
Volume Analysis ◽  
Flow Effects ◽  
And Performance ◽  
Rotary Wing

Small aerial vehicles possess advantages in terms of size and accessibility in performing a variety of tasks. Presently, their design and performance is dependent on variations of conventional aerodynamic configurations (fixed- and rotary-wing). A disadvantage for these configurations is the aerodynamic potential between the mainstream airflow and the body surfaces are not fully utilized. To solve this issue, the Coandă effect is proposed whereby a high-velocity jet is blown tangentially over a curved surface to increase circulation and lift. Prior to the costly approach (experimental and numerical), an analytical formulation (via control volume analysis) to predict the aerodynamic Coandă lift force of the design concept is developed. This is an extended version of the existing mathematical formulations, capturing viscous flow effects. It is also pertinent for circular and elliptical-shaped designs. The results obtained show that the total lift force is dependent on the jet velocity, outflow angle, dimensions of the jet slot, the projected surface area, and the viscous effect. The approach has demonstrated how this modelling technique is effective in calculating the lift force for cylindrical and elliptical Coandă aircraft design.   

Aerodynamic Throttling of Two-Dimensional Nozzle Flows

1972 ◽  
Vol 23 (1) ◽  
pp. 53-61 ◽  
Author(s):  
R H Nunn ◽  
H Brandt
Keyword(s):  
Control Volume ◽  
Interaction Region ◽  
Experimental Measurements ◽  
Two Dimensional ◽  
Volume Analysis ◽  
Throat Region ◽  
Mainstream Flow ◽  
Nozzle Flows

SummaryThe inviscid interaction resulting from the penetration of a jet of air into the throat region of a bounded mainstream flow is investigated analytically and experimentally. Taking into account the effects of jet shocks, a control volume analysis is used to calculate the mainstream and jet conditions at the boundaries of the interaction region. These results are then used to estimate the shape of the interface separating the jet and mainstream. Particular attention is given to the throttling of the mainstream flow and the analytical predictions show agreement with the experimental measurements.

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