Fuel Distribution Effects on Pulse Detonation Engine Operation and Performance

Abstract

The validity and accuracy of performance measurements for pulse detonation engines depend on the ability to accurately measure thrust and fuel mass flow rates during system operation. Experimental tests have revealed that when fuel mass flow rates are calculated by conventional mass metering methods, incorrect values of the aggregate fuel mass in the combustor will often be calculated due to inaccurate assumptions regarding the spatial fuel distribution. The difficulty in predicting the actual fuel distribution affects the ability to achieve reliable detonations for successful operation and introduces inaccuracies directly into the performance calculations. Tunable diode laser and absorption spectroscopy techniques have been applied to provide time-resolved fuel mass fraction measurements and improve the fidelity of the specific impulse calculations. Results show that stratified fuel distributions that begin near stoichiometric at the forward end of the combustor and gradually become fuel lean near the combustor exit produce substantially higher specific impulse values than axially uniform fuel distributions with the same amount of aggregate fuel due to the ability to reliably detonate while operating at an overall lean condition. Axially uniform fuel distributions at the same average equivalence ratio demonstrated lower detonability and accordingly had lower thrust and specific impulse values.

Experimental investigation of multi-cycle pulse detonation engine at different air inlet systems

“…It is a precondition for operation stability of PDE for the first process including fuel-fill fraction (volume fraction of detonable gas in detonation tube), [10][11][12] air inlet model, [13][14][15] equivalence ratio, 16 fuel distribution, [17][18][19][20] etc.…”

Internal Flow Dynamics in a Valveless Airbreathing Pulse Detonation Engine

“…In parallel to the experimental investigations [12][13][14], initial efforts have been applied to study numerically the first cycle of operation with an explicit timing strategy [16,17]. The present work extends our earlier approaches by conducting a comprehensive analysis of the internal flow dynamics in the entire valveless PDEs described in [12][13][14]. The purposes are to thoroughly understand the various processes in the engine operation, to assess the propulsive performance under limit-cycle conditions, and to provide guidelines for design optimization.…”

“…The stagnation of the airflow during the valve-closed period leads to some performance loss, although the problem may be mitigated by using multiple detonation tubes [9]. In the valveless design, the isolation between the inlet and the combustor is achieved through gas-dynamic means, such that no valves are required for controlling the air delivery into the combustor [2,[12][13][14][15][16][17]. The system is mechanically simpler and circumvents the disadvantage associated with airflow stagnation in the valved design.…”

“…Brophy and colleagues [12][13][14] conducted a series of experimental studies on valveless PDEs operating on ethylene, propane, and JP-10 fuels. The system, as shown in Fig.…”

“…The purposes are to thoroughly understand the various processes in the engine operation, to assess the propulsive performance under limit-cycle conditions, and to provide guidelines for design optimization. Figure 1 shows schematically the experimental facility described in [14]. The system includes a vitiator, an inlet module, an isolator, an initiator, and a combustor.…”