Session: 04-23 Pressure Gain Combustion II

Paper Number: 152698

Experimental Analysis of Operating Frequency Enhancement and Pressure Characteristics in a Pulsed Detonation Combustor 

Pressure gain combustion (PGC) has garnered attention due to its potential for higher thermodynamic efficiency compared to traditional quasi-constant pressure combustion methods, such as those found in conventional gas turbine engines. One of the most promising PGC technologies is the Pulsed Detonation Combustor (PDC), which uses detonation waves for combustion, achieving rapid pressure rise and energy release. However, to become a competitive alternative to traditional combustion chambers, the PDC must operate at higher frequencies, which requires optimizing the combustion cycle. In particular, reducing the time spent in the filling phase, which is typically the most time-consuming stage of the PDC cycle, can significantly increase operational frequency, thus improving overall performance.

This paper explores an experimental approach to enhance the operating frequency of a hydrogen-fuelled PDC prototype by focusing on aerodynamic tuning through geometric adjustments. Specifically, the study investigates the effect of altering the length of the Hartmann-Sprenger resonator, a key component responsible for promoting vortex generation within the combustor, which can impact the detonation cycle's repetition rate. The PDC’s system has been designed with an initial target operating frequency of 100 Hz, corresponding to the synchronization of the spark plug ignition system. Throughout the experimental campaign, several test configurations presented in this paper show that operational frequencies can be enhanced beyond this baseline.

The experimental setup includes detailed measurements of pressure characteristics within the PDC. High-speed pressure sensors were used to record maximum and mean cycle pressures, as well as pressure gain over the cycle. These data points provide critical insights into the performance of the combustor, allowing for analysis of how the geometry of the resonator and the length of the exhaust pipe influence both pressure development and operating frequency. Additionally, the study evaluates dominant frequencies within the cycle and constructs histograms of detonation wave frequency to map the effects of the geometric changes.

Preliminary findings reveal that modifying the Hartmann resonator geometry significantly influences the combustor's performance, particularly in increasing the vortex generation frequency and enabling faster cycle repetition. While the spark plug remains set to trigger at 100 Hz throughout the experimental campaign, in certain configurations, the system achieved higher operational frequencies, demonstrating the capacity for further enhancement. Importantly, the resonator's role in promoting efficient mixing for deflagration-to-detonation transition (DDT) was achieved, with transitions occurring in less than 200 mm lengths. The study also underscores that the interplay between the resonator and exhaust pipe geometries is crucial in fine-tuning the PDC's overall efficiency and operational frequency.

This research highlights the potential of aerodynamic tuning through resonator design to significantly enhance both the frequency and pressure characteristics of a PDC, making it a more competitive alternative for future propulsion systems. The ability to achieve higher frequencies while achieving pressure gain is a critical milestone toward advancing PDC technology to the point where it can be integrated into practical applications, such as aerospace propulsion or energy systems. By focusing on the aerodynamic and geometric factors affecting the PDC cycle, this study demonstrates that resonator and exhaust system alterations are pivotal in driving the frequency and pressure performance of these combustors. Continued exploration of these variables could lead to further advancements, positioning PDC technology as a leading solution for high-efficiency combustion in next-generation propulsion systems.

Presenting Author: Andrei Vlad Cojocea Romanian Research & Development Institute for Gas Turbines - COMOTI

Presenting Author Biography: Eng. Andrei Vlad Cojocea, born in 1995 in Bucharest, Romania, is a Scientific Researcher at the Romanian Research and Development Institute for Gas Turbines (COMOTI) in Bucharest. He also serves as an assistant professor and is a PhD candidate at the Aerospace Doctoral School, Polytechnic University of Bucharest. With a solid academic foundation in aerospace engineering, he completed his MSc in Aeronautics at Imperial College London and an MRes in Turbomachinery at the Von Karman Institute for Fluid Dynamics.

His expertise spans a range of advanced topics, including fluid dynamics, hydrogen combustion, detonation engines, high-pressure turbines, supersonic flows, and turbulence modeling. He has authored several Q1 journal papers and actively participates in international research projects funded by the ESA and Horizon 2020 programs, as well as national research initiatives. Additionally, he has played a key role in the design and development of COMOTI’s TESS detonation test rig and is involved in its ongoing expansion.

His current research focuses on detonative combustion, advanced thermodynamic cycles, and supersonic flow modelling.

Authors:

Andrei Vlad Cojocea Romanian Research & Development Institute for Gas Turbines - COMOTI
Mihnea Gall ROMANIAN RESEARCH AND DEVELOPMENT INSTITUTE FOR GAS TURBINES - COMOTI
Ionut Porumbel Romanian Research & Development Institute for Gas Turbines - COMOTI
George Vrabie Romanian Research & Development Institute for Gas Turbines - COMOTI
Tudor Cuciuc Moldova State University,Institute of Applied Physics
Daniel Eugeniu Crunteanu National University of Science and Technology Polytechnic of Bucharest - Faculty of Aerospace Engineering