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.

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.

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.

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.

Unified Model for Gas-Liquid Pipe Flow Via Slug Dynamics: Part 1 — Model Development

2002 ◽  
Author(s):  
Hong-Quan Zhang ◽  
Qian Wang ◽  
Cem Sarica ◽  
James P. Brill
Keyword(s):  
Flow Pattern ◽  
Pipe Flow ◽  
Slug Flow ◽  
Control Volume ◽  
Model Development ◽  
Flow Patterns ◽  
Hydrodynamic Characteristics ◽  
Momentum Exchange ◽  
Two Phase ◽  
Inclination Angles

A unified hydrodynamic model is developed for predictions of flow pattern transitions, pressure gradient, liquid holdup and slug characteristics in gas-liquid pipe flow at different inclination angles from −90 to 90 deg. The model is based on the dynamics of slug flow, which shares transition boundaries with all the other flow patterns. By use of the entire film zone as the control volume, the momentum exchange between the slug body and the film zone is introduced into the momentum equations for slug flow. The equations of slug flow are used not only to calculate the slug characteristics, but also to predict transitions from slug flow to other flow patterns. Significant effort has been made to eliminate discontinuities among the closure relationships through careful selection and generalization. The flow pattern classification is also simplified according to the hydrodynamic characteristics of two-phase flow.

The Diffusion Stratification Effect in Bunsen Flames

1974 ◽  
Vol 96 (4) ◽  
pp. 530-535 ◽  
Author(s):  
G. I. Sivashinsky
Keyword(s):  
Reaction Zone ◽  
Reaction Rate ◽  
Lewis Number ◽  
Combustion Products ◽  
Bimolecular Reaction ◽  
Adiabatic Temperature ◽  
Strong Temperature Dependence ◽  
Light Component ◽  
Stratification Effect ◽  
Bunsen Flames

The thermal diffusion flame model for a bimolecular reaction under stoichiometry conditions of the fresh mixture was examined. The structure of the flame tip of the Bunsen cone was studied. A local breakdown in the stoichiometry in the vicinity of the reaction zone was found such that the light component is always insufficient. For Lewis numbers greater than unity, the flame front is continuous. The temperature at the exit from the reaction zone exceeds the adiabatic temperature of the combustion products. For a Lewis number of the light component less than unity, either a flame with a continuous front, the temperature of which is less than the adiabatic temperature, or a flame with an exposed tip is possible. The problem is solved on the assumption of a strong temperature dependence of the reaction rate.

An Analytical Model for Prediction of Two-Phase (Noncondensable) Flow Pump Performance

1985 ◽  
Vol 107 (1) ◽  
pp. 139-147 ◽  
Author(s):  
Okitsugu Furuya
Keyword(s):  
Analytical Method ◽  
Single Phase ◽  
Two Phase Flow ◽  
Control Volume ◽  
Model Development ◽  
Oil Well ◽  
Phase Flow ◽  
Flow Conditions ◽  
Two Phase ◽  
Pressurized Water

During operational transients or a hypothetical LOCA (loss of coolant accident) condition, the recirculating coolant of PWR (pressurized water reactor) may flash into steam due to a loss of line pressure. Under such two-phase flow conditions, it is well known that the recirculation pump becomes unable to generate the same head as that of the single-phase flow case. Similar situations also exist in oil well submersible pumps where a fair amount of gas is contained in oil. Based on the one dimensional control volume method, an analytical method has been developed to determine the performance of pumps operating under two-phase flow conditions. The analytical method has incorporated pump geometry, void fraction, flow slippage and flow regime into the basic formula, but neglected the compressibility and condensation effects. During the course of model development, it has been found that the head degradation is mainly caused by higher acceleration on liquid phase and deceleration on gas phase than in the case of single-phase flows. The numerical results for head degradations and torques obtained with the model favorably compared with the air/water two-phase flow test data of Babcock and Wilcox (1/3 scale) and Creare (1/20 scale) pumps.

INTERNAL BALLISTICS OF CLASSIC GUN WITH COMPOSITE CHARGE

2019 ◽  
Vol 147 (3/2018) ◽  
pp. 47-62
Author(s):  
Marek Radomski
Keyword(s):  
Mathematical Model ◽  
Hard Core ◽  
Combustion Products ◽  
Maximum Pressure ◽  
Muzzle Velocity ◽  
Internal Ballistics ◽  
Lumped Parameter ◽  
Model Equations ◽  
Gun Firing ◽  
Composite Charge

The paper presents a lumped parameter mathematical model considering the changes of thermodynamic properties for combustion products of a composite propelling charge, and of a burning cartridge casing or shell as well, when shot with classic guns. In addition a method was proposed for considering not coincidental instants of ignition for particular components of the charge and also for powder grains of each component, and the heat flow into the walls containing the space with combustion products. Some results of numerical computations are shown for 125 mm 2A46 tank gun firing a hard core projectile. Moreover an evaluation of accuracy of the results is given on the basis of experimental data. Maximum pressure and muzzle velocity were basic criteria at the verification of the model. Analysis of accuracy for solutions of model equations allows a conclusion that the proposed mathematical model may be useful at the designing process of ammunition and guns.

scholarly journals Effect of Pressure on the Uniformity of Nozzles Transverse Distribution and Mathematical Model Development

2017 ◽  
Vol 65 (2) ◽  
pp. 563-568 ◽  
Author(s):  
Vladimir Višacki ◽  
Aleksandar Sedlar ◽  
Rajko Bugarin ◽  
Jan Turan ◽  
Patrik Burg
Keyword(s):  
Mathematical Model ◽  
Coefficient Of Variation ◽  
Model Development ◽  
Pressure Change ◽  
Operating Pressure ◽  
Pesticide Application ◽  
Working Pressure ◽  
Transverse Distribution ◽  
Working Liquid

Timely and high-quality application of pesticides contributes to environmental protection, economical production and production of healthy food. The efficacy of pesticide application depends not only on the quality of pesticides but also the quality of the application. One of the factor that most influences the quality of applications, from the standpoint of mechanization, are nozzles. They working liquid applied on the surface the plant resulting in the same volume of pesticide is applied to the entire surface of the plants. To achieve this goal, nozzles must be performed uniform application of working liquid per unit area, or tractor sprayer working width. The variable factor in the application of pesticides may be nozzle and operating pressure. With increasing working pressure obtained smaller droplets. The paper presents test of three different nozzles. Each nozzle is characterized by a flat jet with an angle of 110° and a flow rate of 1.6 l∙min−1 at a pressure of 3 bar. Differ from each other are by the way of disintegration of the jet. Exactly this characteristic causes that with pressure change coming to changes in the uniformity of nozzles transverse distribution. So the best distribution has nozzle with a flat jet. The coefficient of variation is between roughly from 4 to 6 % at the pressure application of 2 to 4 bar. Obtained mathematical model that describes changes in the coefficient of variation depending on pressure applications can be a good basis for easy harmonization parameters in the pesticide application.

scholarly journals An experimental study on the pulse combustor. (Characteristics of the pulse combustion for designing)

1985 ◽  
Vol 51 (469) ◽  
pp. 3068-3073
Author(s):  
Toshihiko SAITO ◽  
Kazuo SAITO ◽  
Satoshi HISAOKA ◽  
Fusao HIRASAWA ◽  
Sumio TANAKA ◽  
...  
Keyword(s):  
Experimental Study ◽  
Pulse Combustor ◽  
Pulse Combustion

scholarly journals On the correct use of mathematical constructions in physical models

2020 ◽  
pp. 7-27
Author(s):  
M. Belevich
Keyword(s):  
Mathematical Models ◽  
Physical Meaning ◽  
Fluid Model ◽  
Model Development ◽  
Physical Models ◽  
Model Modification ◽  
First Case ◽  
Viscous Fluid Model ◽  
Model Equations ◽  
Physical Phenomena

The physical limitations of the mathematical constructions used in developing or modifying mathematical models are discussed. All reasonings are illustrated by examples from fluid mechanics. The following topics are considered: means of description; correct approach to model modification and the physical meaning of model development stages. In the first case, the method of describing physical objects using numbers as well as corresponding restrictions are investigated, followed by developing general recommendations on procedures for modifying mathematical models of fluid dynamics. The well-known procedure of averaging the viscous fluid model equations to obtain the turbulent fluid model is used as an illustration. Since we are considering the models of physical phenomena, it is natural to provide physical interpretation for each stage of model development. Unfortunately, some of the transformations used are often treated as purely technical tricks, therefore denoting the lack of the physical meaning in such cases, which does not make a mathematical procedure unacceptable, but does mark out the model's place which requires reasonable interpretation. In this paper, we are considering two variants of this kind of interpretation, namely the case of using imaginary quantities, and the case of applying integral transformations. Meanwhile, all the above-mentioned restrictions are not always given due attention. Sometimes this leads to various undesirable consequences, including excessive task complication, implicit substitution of a declared problem with another one, or, finally, lack of solution to the formulated problem.

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