Volume Combustion Chamber Research Articles

Design of a Guided Missile Interceptor Using a Genetic Algorithm

An apportioned pareto genetic algorithm was used to manipulate a solid rocket design code, an aerodynamic designcode,andathree-loopautopilottoproduceguidedmissileinterceptordesignscapableofaccuratelyengaging a high-speed/high-altitude target. Dee nition of the optimization problem required 29 design variables, and 4 primary goals were established to assess the performance of the interceptor designs. Design goals included the following: minimize miss distance, minimize intercept time, minimize takeoff weight, and minimize maximum g loading. In 50 generations, the genetic algorithm was able to develop 2 basic types of external aerodynamic designs that performed nearlythe same, with miss distances less than 1.0ft. The solid rocket motors that propelled these external shapes shared common characteristics such as a large initial burning area and a large combustion chambervolume. Thegeneticalgorithmdid not prefermaximizing theamount offuel within therocket motorcase (high fuel volume ratio). A higher fuel volume ratiotypicallymeans higher launch weight, but does not necessarily guarantee faster intercepts given enite thermal limits. Examination of the intercept trajectories themselves shows that standard proportional navigation guidance works adequately, but could probably be improved by thrust compensation,especiallyduringthelaunchtransient.Thethree-loopautopilotperformswellevenforhigh-altitude engagements, and the analytic gain determination makes the autopilot straightforward to implement.

Minimum Fuel Consumption Design of a Turbo-Charged V-6 Engine

The design of a turbocharged, gasoline fueled, four-stroke engine is considered with the goal of selecting design and operating variables to minimize fuel consumption. The development of the engine simulation code and the effect of model assumptions on the results are presented. The optimization includes constraints on detonation, exhaust emissions, and torque. Variables are bounded to assure the validity of the simulation. A number of observations about the interaction between the thermo-fluid model and the nonlinear programming algorithm are made and general strategies to enhance the optimization under such circumstances are discussed. The method is illustrated by exploring the design of a turbocharged Buick V-6 engine on an IBM PC/AT personal computer. Stock design variables, and operating variables that provided a design away from the constraints imposed by torque, emission, and detonation were chosen as the starting point for the optimization. Application of the optimization strategy resulted in an 18 percent reduction in predicted fuel consumption at 50 miles per hour. Significant specific recommendations included a reduction in combustion chamber volume, an increase in intake manifold pressure, an increase in intake duration, a decrease in exhaust duration, and relatively small changes in valve geometry. The paper clearly demonstrates that it is feasible to do relatively sophisticated engineering design and optimization on personal computers, and it sets the stage for further work in this area.

Pulse Combustion: Demonstration of the Characteristic Mixing Time in a Commercial Burner

Abstract The response of a prototype Helmholtz-type commercial pulse combustor to changes in two fundamental characteristic times has been investigated both experimentally and numerically. The natural resonant frequency and the fluid dynamic mixing geometry were modified separately. The response of the combustor to these changes was determined by measurements of pressure, frequency, and OH· chemiluminescence. The combustion chamber volume was modified to change the resonant frequency of the combustor. Changes in the fluid dynamic mixing time were obtained by injecting premixed reactants axially and then temporally and spatially modifying the injection profile by varying the geometry of a novel injection system. A wide dynamic range in pressure amplitude and frequency was obtainable by changing the characteristic fluid dynamic mixing time. Results from systematic changes in these two parameters compare well with the results from the numerical model of a pulse combustor that has been developed at Sandia National Laboratories.

The Influence of the Variation of Combustion Chamber Volume under pressure load on the determinational of thermodynamic characteristics of solid propellants in pressure bombs

AbstractDetailed combustion studies in high‐pressure bombs show that the measured maximum gas pressures are always lower than theoretically calculated values and that these differences increase more than proportionally with rising loading densities. By means of experiments and calculations we show that a considerable part of the pressure difference is brought about by the expansion of the combustion chamber during pressure load.The expansion of the combustion chamber is responsible for pressure measurements that are about 5% too low at currently used pressures of 500 MPa. Furthermore the covolume yields an error of about 12% if the constants of the Abel state equation are determined using the standardized method for loading densities of 0.20 g/cm3 and 0.22 g/cm3. The error of the force constant remains under 1%.As the values determined from pressure bomb measurements are to be introduced into further calculations, they must be corrected according to the combustion chamber expansion, or new measuring methods will be necessary.

Mathematical modelling of three-dimensional heat transfer from the flame in combustion chambers

In this article, mathematical modelling with the Monte-Carlo solution and the finite difference method is used to solve the integral-differential equations of the three-dimensional heat transfer process from flame in combustion chambers or furnaces. By using this kind of mathematical modelling, the combustion chamber volume and its walls can be divided into thousands of elements for calculation; both the temperature distribution of the gases in the combustion chamber volume and the heat flux distribution on its walls can be solved easily. With the modified method, statistical modelling calculation of the radiant energy, speeding up the convergence of the solution, consideration of the absorption coefficient of the gray gases in the combustion chamber as a function of the coordinate in space, and consideration of the influence of the fouling factor of the walls on heat transfer, make the calculated results quite satisfactory.

Experimental Determination of Non-ignition Diameter for Various Ignition Positions

Abstract When a nozzle diameter is greater than the quenching diameter, the flame from an explosion inside a chamber can pass through the nozzle, but it will not always ignite the outside combustible mixture. There is a non-ignition diameter, greater than the quenching diameter, below which ignition will not occur and above which it will. The present paper presents experimental determinations of non-ignition nozzle diameters for different values of several parameters (ignition position, mixture concentration and chamber volume). The non-ignition diameter is affected by the ignition position, the mixture concentration and the primary combustion chamber volume. As the ignition position moves to the far end of the nozzle, the non-ignition diameter increases gradually, and the largest non-ignition diameter exists at the ignition position 3, having the highest introduced pressure. For any ignition position, the minimum non-ignition diameter is found to occur near the stoichiometric mixture. The non-ignition diameter is approximately proportional to the ejected velocity.

Importance of Combustion Chamber Geometry in High Frequency Oscillations in Rocket Motors

The experiments reported herein were concerned with the determination of some of the underlying factors which contribute to the occurrence of transverse modes of combustion pressure oscillation in rocket motors. Two rocket motors having different diameters and several different lengths were employed in the experiments using a gaseous hydrocarbon fuel and air as propellants. The investigation indicated that changes in the aspect ratio and volume of the rocket motor combustion chamber had a profound effect on the incidence and amplitude of the transverse modes. These effects were modified by interactions of the transverse modes with the longitudinal mode. The transverse modes present in the experiments were determined to be the spinning and the radial modes.

The Calculation of the Volume of Rocket Combustion Chambers

In contrast with previously known methods of calculating the volume of rocket combustion chambers which are concerned with a ‘characteristic length’ to be determined experimentally for each fuel and for each injection system, it will be shown that there is available: (a) a generally valid qualitative theoretical relationship between the combustion chamber volume VC and any desired combustion pressure, mass flow, fuel and combustion chamber shape. (b) a generally valid relationship, for practical design purposes, between the combustion chamber volume VC and any desired combustion pressure, mass flow, fuel and combustion chamber shape. Further, the theoretical results will be compared, by means of examples, with combustion chambers which have been tested in practice. Moreover, the important fact will be indicated that the formula proposed in this article must, in principle, also be applicable to the calculation of the volume of the gas turbine combustion chamber.