Erosive Burning Rate Research Articles

Extended Application and Experimental Verification of a New Erosive Burning Model Coupled Heat Transfer between Gas and Grain Based on a Star-Grain Solid Rocket Motor

The estimation of erosive burning is of great importance for the internal ballistics computation of a solid rocket motor (SRM) with a large aspect ratio. Because of the variety of parameters affecting erosive burning, most of the erosive burning models developed in earlier years usually contain unknown constants that need to be identified by a trial-and-error procedure for each SRM. Based on an SRM with a cylindrical grain, a new erosive burning model, which coupled the heat transfer between the gas and grain, was proven to be effective previously. To expand the scope of application of this model, in this paper, earlier and new erosive burning models were used in the transient one-dimensional internal ballistics computation, to obtain the internal ballistics for a star-grain SRM. A comparison between the computational and experimental results indicated that both the earlier and new erosive burning models can obtain results with good accuracy for a star-grain SRM. The paper shows that with no constants to be identified, the Ma model is easy to use and has the potential to predict the erosive burning rate before a firing test.

Parametric Study of Solid Fuel for Hydrogen Peroxide Hybrid Rocket Design

In this study, impact of the port diameter and length changes of a solid fuel on its performance parameters was investigated to propose design considerations for the solid fuel for hydrogen peroxide/high-density polyethylene hybrid rockets. A laboratory-scale hydrogen peroxide/high-density hybrid rocket was designed to perform a parametric study of the solid fuel through experiments. The ratio of the nozzle throat area to the fuel port area and ratio of the fuel length to the fuel port diameter were used to design the port diameter and length of the solid fuel. Altering the fuel port diameter affected the characteristic velocity efficiency, oxidizer mass flux, velocity-based erosive burning, oxidizer-to-fuel ratio, and regression rate. Altering the fuel length affected the oxidizer-to-fuel ratio and characteristic velocity efficiency and had little effect on the regression rate because it did not significantly contribute to the change in the oxidizer mass flux. No improvement was observed in the characteristic velocity efficiency after the ratio of the fuel length to the fuel port diameter reached 20. Finally, design considerations for the port diameter and length of the solid fuel for a hydrogen peroxide/high-density polyethylene hybrid rocket were suggested based on the experimental results considering the changes in the ratio of the nozzle throat area to the fuel port area and ratio of the fuel length to the fuel port diameter.

A New Erosive Burning Model of Solid Propellant Based on Heat Transfer Equilibrium at Propellant Surface

Erosive burning refers to the augmentation of propellant burning rate appears when the velocity of combustion gas flowing parallel to the propellant surface is relatively high. Erosive burning can influence the total burning rate of propellant and performance of solid rocket motors dramatically. There have been many different models to evaluate erosive burning rate for now. Yet, due to the complication processes involving in propellant and solid rocket motor combustion, unknown constants often exist in these models. To use these models, trial-and-error procedure must be implemented to determine the unknown constants firstly. This makes many models difficult to estimate erosive burning before plenty of experiments. In this paper, a new erosive burning rate model is proposed based on the assumption that the erosive burning rate is proportional to the heat flux at the propellant surface. With entrance effect, roughness, and transpiration considered, convective heat transfer coefficient correlation proposed in recent years is used to compute the heat flux. This allows the release of unknown constants, making the model universal and easy to implement. The computational data of the model are compared with different experimental and computational data from different models. Results show that good accuracy (10%) with experiments can be achieved by this model. It is concluded that the present model could be used universally for erosive burning rate evaluation of propellant and performance prediction of solid rocket motor as well.

An Approach to Analysing Erosive Characteristics of Two-Channel Combustion Chambers

To acquire the erosive characteristics of two-channel combustion chambers, a quasi-one-dimensional internal ballistics model is proposed. Combining the model with two different erosive burning models, the modified L-R expression, and the Mukunda-Paul expression, the flow parameters and the internal ballistics performance of a test solid rocket motor are computed. The results show good agreement with experimental data. According to the results, the more severe the erosion is, the earlier, longer, and gentler the tail-off stage becomes. During the tail-off stage, the dramatic drop of pressure leads to a low normal burning rate and makes it easier for erosion burning to occur. For this reason, notable erosive burning might appear during tail-off if the case-to-throat area ratio is extremely low. The results also show that flows in the inner channel and the outer channel are similar but not identical. This leads to different erosive burning behaviours in the two channels. Also, the two erosive burning rate models involved in this paper are compared. It seems that the M-P expression provides better results than the modified L-R expression does, since it reveals the threshold phenomena. Besides, the M-P expression has great advantages for its universality for most propellants and different SRM geometries.

Combustion characteristics of solid propellants under high-temperature dense-particle erosion conditions

High-concentration alumina particle jet can erode the surface of the solid propellant inside a solid rocket motor under some special conditions such as flight acceleration. Because of lack of effective testing methods, knowledge of the combustion characteristics of solid propellants under dense-particle erosion conditions is very limited. In this study, the combustion characteristics of hydroxyl‑terminated polybutadiene and nitrate ester plasticized polyether propellants were investigated using real-time X-ray radiography technology and an overload simulation erosion motor. The high-temperature dense-particle jet can cause erosive burning of the solid propellants. No clear threshold velocity is found for the particle erosive burning, and the erosive burning rate increases with the particle velocity. The erosion of the dense-particle jet includes the heat flux increment effect and mechanical damage effect, and the particle erosive burning is mainly caused by the heat flux increment effect of the particles. Numerical simulation results show that the particles can impact the propellant surface at a very low speed and cause heat flux increments; this explains the lack of a clear threshold velocity for the particle erosive burning of solid propellants.

Numerical simulation of ignition transient in solid rocket motor: a revisit

PurposeThe capability to predict and evaluate the motor pressure during each phase by means of a numerical analysis can significantly increase the efficiency of the preliminary design process with a reduction of both the motor development and operational costs. This paper aims to perform numerical simulation to analyze the ignition transient in solid rocket motor by solving Euler equation coupled with some semi-empirical correlations. These relations take into account the main phenomena affecting the ignition transient. Coupling relationships include the heat transfer of the gas to the propellant and erosive burning rate relationship.Design/methodology/approachThe current research effort divides motor into series of control volumes along the port axis, and the variation of port area, burning surface and burning rate along the port are taken into account. A set of governing equations are then solved using explicit, time-dependent, predictor-corrector finite difference method. The numerical model helps to capture and embed shock wave associated with igniter flow within the solution. Second-order artificial viscosity dampens out the numerical oscillations due to sharp gradient within the flow field. The developed computer code predicts the start-up characteristics of motor. The study also provides comparison of simulation results with in-house experimental motor.FindingsSimulations are performed with and without erosive burning to demonstrate that the flow model is a good physical approximation of motor. Numerical results calculated by this model without erosive burning are not in good agreement with experimental results. This minor discrepancy has motivated the inclusion of erosive burning in numerical model. The simulated results are then compared with the experimental data for head-end and rear-end pressure. The agreement between simulation and experiment is remarkable. In summary, major finding of this study is that unsteady quasi-one-dimensional gas dynamic model can capture the flow field in the motor during ignition transient effectively.Research limitations/implicationsUnsteady quasi-one-dimensional gas dynamic model can capture the flow field in the motor during ignition transient effectively. However, in systems where two- and three-dimensional effects are pre-dominant, one would require to develop a more elaborate, multi-dimensional model which will allow for further understanding of the flow behavior and eventually lead to modeling of rocket motors with more complex geometries.Practical implicationsThe close agreement between experimental and simulation results can be considered as forced to some degree, because the general mathematical model of erosive burning contains a free variable erosive burning exponent. However, in future, this variable can be established a priori by erosive burning tests.Originality/valueThe solid propellant ignition process consists of series of rapid events and must be completed in a fraction of a second. An understanding of the dynamics of ignition has become increasingly vital with the development of larger and more sophisticated solid propellant rocket motors. This research effort provides the simulation framework to predict and evaluate the motor pressure during each phase by means of a numerical analysis, thus significantly increasing the efficiency of the preliminary design process with a reduction of both the motor development and operational costs.

Erosive Burning Modeling for Solid Propellant Rocket Motor

Abstract:Many phenomena occur during Solid Propellant (SP) Rocket Motor (RM) firing, one of the most important is known as SP erosive burning, which occurs at the end of grain, during the earliest period of firing after ignition. Calculating and analyzing erosive burning rate are an essential requirement for evaluating SPRM performance parameters. Intensive theoretical investigations are performed for the prediction of erosive burning and RM internal ballistic parameters. Investigations help in minimizing experimental work, which is expensive, risky and time consuming.This paper presents a SPRM erosive burning computer code with its mathematical simulation, based on heat transfer theory of Lenoir and Robillard. Results of modeling are compared with the results of experimental study and a satisfactory agreement is indicated by an error less than 5%. The experimental work is based on full-scale firing of artillery RM that has higher propellant filling coefficient (volumetric loading).A comprehensive analysis of the erosive burning phenomena and simplified formula are presented. The presented simulation code can be considered as a powerful tool for design parameters and analysis of the erosive burning rate for SPRM.

Analytical calculation of the negative erosive burning rate

The rate of negative erosive combustion is calculated using analytical methods and a simple model of the gas-phase chemical reactions A → B. The conversion of part of the thermal energy into the kinetic energy of motion of gaseous combustion products along the propellant gasification surface is taken into account within the model. Solutions are obtained for the cases where the thickness of the laminar sublayer is larger or smaller than the width of the combustion zone in the gas phase. The calculation results confirm the author’s previous conclusion: manifestation reduction in the negative erosive effect with decreasing initial temperature of the propellant is caused by narrowing of the region of its occurrence.

Природа и расчет скорости эрозионного горения твердого ракетного топлива

Природа и расчет скорости эрозионного горения твердого ракетного топлива

Numerical Study of Erosive Burning in Multidimensional Solid Propellant Modeling

Using numerical simulations, the combustion response of heterogeneous solid propellants to an imposed crossflow velocity field are examined. It is shown that this model flow is useful to capture the influence of shear flow in the so-called erosive burning phenomenon observed in actual experiments. Previous numerical studies on a model quarter-plane problem and on homogeneous solid propellants have shown that the presence of shear in the crossflow plays a role in increasing the heat transfer to the propellant surface, thus enhancing the burn rate. In the current work, the response of twoand three-dimensional packs to an imposed velocity field are first examined for different propellant morphologies and at different pressures. The imposed velocity field has its root in a separate nonreactive multiscale analysis. It is shown that, with the model flow, the variations of the erosive burning rate with shear parameters are captured, the trends being in line with experimental results. Furthermore, a comparison with experimental results present in the literature is examined, where it is shown that the results compare qualitatively well with the experiments using the estimated shear rates from the experiment. These results suggest that the influence of the shear flow on the primary diffusion flame may be a leading factor in the erosive burning effect.

On the threshold nature of erosive burning

A physical explanation for the existence of the threshold of erosive burning is proposed. It is shown that this type of combustion occurs when the thickness of the laminar sublayer in the turbulent boundary layer becomes smaller than the thickness of the laminar combustion zone. In this case, turbulent flame in the gas phase is formed. Relations are obtained linking the critical (threshold) velocity of the blowing flow and the critical Vilyunov number to the properties of the propellant and the gas resulting from propellant decomposition. Simple exponential dependences on the blowing velocity are found for the burning rate. The simplest representation of the erosive burning rate is obtained using the Bulgakov-Lipanov number, whose threshold value is equal to unity. A new mechanism for the occurrence of negative erosion is proposed, according to which the burning rate decreases during blowing because the boundary layer is displaced, resulting in a decrease in the heat flux from the flame zone to the solid-phase decomposition surface.

Solving an Inverse Problem of Erosive Burning Rate Reconstruction

A new method for an experimental study of burning processes in condensed substances is suggested, based on the statement and solution of inverse problems. An inverse problem of reconstructing the erosive burning rate of solid propellants from experimental data is formulated. The choice of an approach to solving the problem by the joint application of well-known methods for inverse problem solution and specific features of experimental studies of burning processes, in particular, erosive burning, has been justified. The problem solution is illustrated by a numerical example. The testing involves a comparative analysis of two optimization methods: although both methods are characterized by an identical accuracy, the steepest descent method has a higher rate of convergence for this class of problems than the conjugate gradient method.

96/04156 Modelling of normal and erosive burning rate of a hot double-base homogeneous propeilant

96/04156 Modelling of normal and erosive burning rate of a hot double-base homogeneous propeilant

Modeling of normal and erosive burning rate of a hot double-base homogeneous propellant

The burning rate of a hot double-base homogeneous solid propellant is modeled by the numerical solution of the conservation equations characterizing the primary flame using a global kinetic scheme. The increase of the burning rate above the solid surface is modeled by an enhancement of the heat transfer between the flame and the wall by the turbulent mechanisms. The calculated burning rate overshoot, generally called erosive burning, accurately predicts the experimentally observed phenomena.

Study of flow induced by nonuniform lateral injection

The cold flowfield in a closed-end 90 m-porosity porous-walled two-dimensional duct at nonuniform lateral injection condition (approximately exponential distribution) has been investigated, using both laser-Doppler velocimetry measurements and theoretical analysis. The measured and predicted similar velocity profiles are in reasonable agreement, and the conditions for the existence of similarity are identified. A comparison with the previous case of uniform wall injection has also been made. The comparison includes the transition process of the mean-velocity profile, the shift of peak turbulence intensity, the evolution of relative turbulence intensity with axial distance, and the sensitivity of the local heat transfer or erosive burning rate to the relative injection ratio.

Turbulent Flow Analysis of Erosive Burning of Cylindrical Composite Solid Propellants

An axisymmetric turbulent boundary layer was analyzed in order to investigate erosive burning in composite solid-propellant rocket motors. It was found that there is a strong interaction between the core flow acceleration and turbulence level in the boundary layer. The increase of turbulence near the surface of the propellant plays an important role in the erosive burning mechanism. Reducing the port diameter makes a rocket motor more sensitive to erosive burning. When the port diameter is uniform, the erosive burning rate increases toward the aft end of the rocket motor. This trend is less pronounced or even reversed when the port diameter is divergent.

Measurements and Model Validation for Composite Propellants Burning under Cross Flow of Gases

Erosive burning rates of three types of ammonium perchlorate-based composite propellant formulations were measured by using the high-speed motion picture method. Experiments were conducted in a test rig designed to develop a well-defined, turbulent boundary layer with a distinct leading edge by the flow of combustion gases over two-dimensional propellant samples. Erosive burning rate correlations which relate the burning rate to freestream velocity and pressure were developed. The comparison of experimental data and theoretical results obtained from the erosive burning model, based upon the turblilent boundary-layer approach developed by the authors, showed a close agreement.

Erosive Burning Study of Composite Solid Propellants by Turbulent Boundary-Layer Approach

Erosive burning of composite solid propellants is investigated by analyzing a steady, two-dimensional, chemically reacting, turbulent boundary layer over a propellant surface. Predicted erosive burning rates agree closely with experimental data. The erosive burning rate augmentation is found to be caused by the increase in heat feedback introduced by the increase in transport coefficients, and the turbulence enhanced mixing and reaction of the oxidizer and fuel gases. The increase in freestream gas velocity brings the location of the peak turbulence intensity and the heat release zone closer to the propellant surface, thereby increasing the burning rate of a propellant.