Pulsed Detonator for Scramjet Ignition and Combustion Augmentation using On-board Resources

Ignition devices for defense applications are often one-shot pyrotechnic safety devices. Reusable scramjet or ramjet systems instead require indefinite reliable ignition cycles. Storage of hypergolic or non-standard resources is an option, yet long-term storage, replenishment, and complexity must be weighed against the relative simplicity and elegance of using existing on-board resources, such as bleed air and conventional aerospace fuels. Beyond reliable ignition across a range of environments, there also exists a need during off-nominal conditions to deposit additional energy into the flame-holding cavity or elsewhere in the combustor to maintain combustion in a supersonic scramjet flow. An appealing advantage would be devices capable of both ignition and sustaining energy deposition to support combustion. Numerous ignition device types have been studied and tested in supersonic flow conditions. The environmental requirements are severe for these applications and further exasperated in reusable systems. This drives the solution towards non-protruding mechanisms that can survive for extended periods. This proposal addresses pulsed detonators (PD) for ignition, with dual-use application in a pulsed setting for quasi-sustained energy deposition. The PD device is chosen for its ability to effectively deposit substantial energy deposition into a flame-holder cavity or combustor versus conventional low-energy passive ignition systems. A challenge is that on-board resources of air and JP or RP-type fuels have large detonation cell widths compared to pure oxygen/JP or air/hydrogen combinations. The detonation cell size substantially drives a PD igniter's overall diameters and lengths. In response, this project transforms available on-board resources to reduce the detonation cell width to minimize the total volume of the PD igniter device. A robust design of experiments with a testbed PD system validates the concept's ability to reduce detonation cell size and thus overall system volume. The result is a preliminary design of a pulsed detonator system suitable for ignition and extended energy deposition in ramjets and scramjets.