This study develops a three-dimensional multi-physics framework for simulating ignition transients in solid rocket motors (SRMs), explicitly resolving the coupled interactions of transient compressible flow, heat transfer, combustion, and structural dynamics. The methodology introduces a weighted residual formulation based on common-refinement discretization for fluid–structure interface data transfer, which rigorously enforces conservation laws while minimizing numerical errors across non-matching meshes. Temporal synchronization across physical domains is achieved through predictor–corrector iterations, ensuring stability in strongly coupled simulations. Validation employs a supersonic shock-panel interaction benchmark, where data exchange tests between mismatched fluid and solid surface meshes confirm the method’s accuracy and robustness properties. Quantitative comparisons with experimental measurements and reference numerical solutions demonstrate its accuracy in handling compressible fluid–structure coupling. Application to an SRM ignition case captures coupled flow evolution, flame propagation, and propellant structural responses. The coupled simulation reveals distinct flame spreading patterns and dynamic burning surface evolution, directly linked to chamber pressure variations unobserved in single-field analyses. Furthermore, the results identify the propellant’s viscoelastic behaviour and ignition-induced structural vibrations, underscoring the necessity of multi-physics coupling to resolve transient ignition mechanisms. This work establishes a computational foundation for analyzing critical interactions governing SRM ignition dynamics.

A zero-voltage switching (ZVS) push–pull self-oscillating arc ignition circuit was proposed, marking the first application of ZVS technology in welding arc ignition systems. The circuit’s working principle was analyzed, and time-domain waveforms of the switching transistors verified the realization of soft switching. A conducted interference test platform was established in order to assess the circuit’s electromagnetic compatibility under no-load and arc ignition transient conditions. In comparison with conventional domestic arc ignition circuits, the proposed ZVS circuit demonstrated substantially diminished quasi-peak interference levels, with a reduction exceeding 9.5 dB in both instances. Additionally, under no-load conditions, the ZVS circuit demonstrated interference levels comparable to those of a commercial Fronius system, while during arc ignition transients, it exhibited an over 5 dB reduction. The findings of this study demonstrate that the incorporation of soft-switching techniques into arc ignition circuits can effectively mitigate conducted interference, thus providing a promising and practical approach for industrial welding equipment.

<div class="section abstract"><div class="htmlview paragraph">Launch vehicle structures in course of its flight will be subjected to dynamic forces over a range of frequencies up to 2000 Hz. These loads can be steady, transient or random in nature. The dynamic excitations like aerodynamic gust, motor oscillations and transients, sudden application of control force are capable of exciting the low frequency structural modes and cause significant responses at the interface of launch vehicle and satellite. The satellite interface responses to these low frequency excitations are estimated through Coupled Load Analysis (CLA). This analysis plays a crucial role in mission as the satellite design loads and Sine vibration test levels are defined based on this. The perquisite of CLA is to predict the responses with considerable accuracy so that the design loads are not exceeded in the flight. CLA validation is possible by simulating the flight experienced responses through the analysis. In the present study, the satellite interface responses are validated for a launch vehicle with solid motors. The source of dynamic force in solid motor is mainly the motor ignition transient. Transient response analysis is carried out using the Finite Element models of launch vehicle coupled with the satellite to simulate the responses during solid motor ignition. The required excitation is generated from the motor ignition transients measured in the flight. The criticality in the simulation is to define and model the forcing function appropriately. The responses estimated from the analysis are compared with the responses measured in the flight and observed to be in good match in both temporal and frequency domain. The study confirmed that the forcing functions developed from the flight measured data are adequate. The post flight simulation studies helps to improve the prediction methodology for future missions.</div></div>

Effect of spark location and laminar flame speed on the ignition transient of a premixed annular combustor

Abstract High‐speed self‐spin is one of extreme working conditions that alters ignition internal ballistic performance and can induce ignition abnormalities. To demonstrate the studies on mechanism of interior ballistics as the results of acceleration loads imposed on spinning SRM, the modes of swirl dynamical flow and acceleration‐induced combustion phenomena for igniter and propellant are developed and first taken into account in a new ignition model by user‐defined sources (UDS). To verify the model, the heat transfer, added‐mass and build‐up pressure modes of this ignition model are verified by comparison with static ignition experimental data, second, the swirl flow field mode is validated through comparison between models and by analogy with experimental phenomena, then the numerical model is proved by grid‐independent verification. Dimensionless analysis eliminates diversity in time scales at different periods. The influences of swirl flow, igniter, and propulsion acceleration‐induced combustion on various stages of ignition are studied. It was found that: (1) Time scale in the ignition process of spinning SRM is mainly affected by the igniter‘s sensitivity to rotational acceleration (Aig), whose change is approximately described as an empirical equation based on rotational overload (α) and ignition sensitivity coefficient limit Aig,max; (2) The acceleration effect on propellant combustion is mainly manifested in the pressure peak and the pressure rate, however, it has little effect on the ignition delay; (3) Swirl flow factors are not the main factors affecting the ignition process for small SRMs with small‐contraction nozzles.

The computer code is elaborated for numerical simulation of transient combustion of energetic materials (EM) subjected to the action of time-dependent heat flux and under transient pressure conditions. It allows studying combustion response upon interrupted irradiation (transient pressure) and under action of periodically varied heat flux (pressure) in order to determine stability of ignition transients and parameters of transient combustion. The originally solid EM melts and then evaporates at the surface. It is assumed that chemical transformations occur both in the condensed and gas phases. At the burning surface, the phase transition condition in the form of Clapeyron-Clausius law for equilibrium evaporation is formulated that corresponds to the case of combustion of sublimated or melted EM. The paper contains description of transient combustion problem formulation and several examples of transient combustion modeling. At present time a precise prediction of transient burning rate characteristics is impossible because of the lack of information about magnitude of EM parameters at high temperatures. However, the simulation results bring valuable qualitative information about burning rate behavior at variations in time of external conditions – radiant flux and pressure.

Combustion of Ammonium Perchlorate monopropellant: Role of heat loss

Experimental study on the coupling process of flow and combustion phenomena during pilot ignition transients

Numerical analysis of laser-pulse transient ignition of oxygen/methane mixtures in rocket-like combustion chamber

This paper investigates the impact factors of switching transient overvoltage (SOV) in an offshore wind farm (OWF) by analyzing multiple ignitions of a vacuum circuit breaker. The statistical features of transient overvoltages, which occur under real switching operation scenarios, are analyzed based on the measurements in a laboratory platform that is built according to the configuration of an actual OWF. Next, an OWF simulation transient model is established considering high-frequency characteristics of circuit breakers, which is verified to be able to calculate the SOV accurately. Based on the developed OWF simulation model, the occurrence mechanism of SOV is discussed in detail by studying characteristics of transient voltage and current during multiple ignitions within a vacuum circuit breaker when it is switched OFF. Then, the key impact factors of switching- OFF induced overvoltage are identified, which include the inter-phase capacitance of cable in a windmill tower, the actual operating capacity of a wind turbine generator, and the single-phase inlet capacitance in terminals of a wind turbine transformer. Finally, the recommended configurations are given for the transient mitigation in an OWF.

Numerical simulation on ignition transients of hydrogen flame in a supersonic combustor with dual-cavity

The startup represents a very critical phase during the whole operational life of solid rocket motors. This paper provides a detailed study of the effects on the ignition transient of the main design parameters of solid-propellant motors. The analysis is made with the use of a quasi-one-dimensional unsteady model of solid rocket ignition transient, extensively validated, and used in the frame of the Vega program, for ignition transient predictions, reconstructions, and analyses. Two baseline solid rocket motor configurations are selected for the parametric analysis: a big booster with a three-segment propellant grain shape, similar to Ariane 5, and a small booster/solid stage with an aft-finocyl grain shape, similar to Vega solid rocket motors. The discussion of the results is particularly addressed on the possible onset of the pressure oscillations during the startup of the two solid rocket motor configurations, pointing out the design parameters that affect them in terms of occurrence and amplitude.

Spontaneous ignition of isolated n-heptane droplets at low, intermediate, and high ambient temperatures from a mixture-fraction perspective

Fluid–solid coupled simulation of the ignition transient of solid rocket motor

To study the gas dynamic and heat transfer phenomena inside a single isolated longitudinal solid propellant surface crack, two 3-D geometric models with different crack shapes were constructed. Concerning the influence of propagation of jet from the igniter on the flame spreading phenomena in the crack, flow region around the opening of the crack was also included in the above geometric models. A theoretical framework was then adopted to model the conjugate heat transfer in the combustion channel and the crack cavity. Numerical simulation results indicate that the ignition shock wave can spread into the crack cavity. Extremely high overpressure and pressurization rate were observed along the crack front. It is possible that the crack may propagate before the flame front reaches it. An ignited region located at the crack front near to the channel surface in downstream direction was generated long before the flame front reached the crack opening in both models.

High-speed and Schlieren imaging have been used to visualize ignition transients, discharge behavior and flow fields of a plasma device integrating a low-power inductively coupled plasma torch, generating a high temperature thermal plasma, with a quenching device, able to cool the gaseous effluent down to biocompatible temperatures for effective use in biomedical applications.

The analysis presented in Part I of this study is extended to investigate ignition transients and flame development in an ethylene-fueled scramjet engine. Unheated gaseous ethylene is transversely injected into the combustor upstream of a recessed cavity flameholder. Immediately after the ethylene–air mixture reaches its steady state in the combustor, a hotspot igniter is activated in the cavity to initiate chemical reactions. Cases both with and without air throttling downstream of the cavity during the engine startup stage are examined in detail. Successful ignition can only be achieved with the aid of air throttling under the present flow conditions. As a consequence of the backpressurization by the throttling air, a shock train is generated in the isolator, which then decelerates the high-speed main stream, enhances the fuel mixing efficiency, and increases the temperature and pressure in the combustor. Chemical reactions are intensified and produce sufficient heat release to maintain a flow environment conducive to flame stabilization. A self-sustaining mechanism is thus established between the flow and flame development. Stable flames are achieved even after the deactivation of air throttling. The predicted pressure distribution along the entire flowpath agrees well with experimental measurements.

Achieving efficient ignition and stable combustion in a high-speed environment has long been a serious concern in the development of scramjet engines. In the engine startup stage, the low chamber pressure and unsettled fuel–air mixing tend to blow off the flame, even if a flameholding device such as a cavity is employed. The problem may be circumvented by modulating the flow structures in the isolator and combustor through air throttling downstream of the flameholder. In experiments, compressed air is introduced in a controlled manner into the combustor to generate a precombustion shock train in the isolator. The resultant increases in the temperature and pressure of the airstream in the combustor, along with the decrease in the flow velocity, lead to smooth and reliable ignition. The incidentally formed separated flows adjacent to the combustor sidewall improve fuel–air mixing as a result of enhanced flow distortion and increased residence time. Because insufficient reaction heat release often leads to an unstable shock train, and exceedingly large heat release may cause severe flow spillage or even inlet unstart, dynamic optimization of the throttling operation is needed to ensure the creation of flow conditions conducive to efficient ignition. The present work establishes an integrated theoretical/numerical framework, within which the influences of all known effects on the engine ignition transient and flame development are studied systematically. Part 1 of the study focuses on nonreacting flow development and fuel–air mixing under the influence of air throttling.

Fast and repeatable ignition transients for small solid rocket combustors can be difficult to achieve. This work sets out to characterize a thermite mixture to fill this need. Igniter function was determined using high-speed imaging, allowing an examination of product droplet size and combustion time as a function of packaging technique. Safety testing (electrostatic discharge, drop weight impact, and friction) indicated that this material is far safer than existing ignition compounds. A simple dual-criteria ignition model is applied to igniter sizing, and our modeling results were successfully evaluated using hot fire tests of motors with various exposed propellant surface conditions. The end result is a safe, inexpensive, reliable, and readily available method of igniting small (500 g–50 kg propellant mass) solid rocket combustors.

This paper illustrates the development and the main features of a ballistic simulation tool for performance prediction of a solid rocket motor of given geometry and propellant properties. The main purpose of the tool is to describe with sufficient accuracy the processes that take place inside the combustion chamber, from igniter activation to motor burn out, in order to evaluate the influence of the main rocket design parameters on them. The tool, also capable of describing the ignition transient of the motor, has been successfully validated by comparing its predictions to the results obtained from tests carried out in a dedicated experimental apparatus. In particular, the validation results shown in this paper are referred to a motor working with a newly designed solid propellant, intended to be used in an amateur rocket having the aim to launch a scientific payload to a maximum altitude of 50 km.