Impulse Correlation for Partially Filled Detonation Tubes

Abstract

to calculate the specific thrust and specific impulse over the Machnumber regime. The specific impulse results are shown in Fig. 3. A Mach-number dependent static inlet temperature profile was used for these calculations in order to account for altitude effects. 7 The nozzle inlet total temperature was chosen to be 4200 R (2300 K). The ratio of specific heats was 1.3. The fuel heating value was 19,000 BTU/lbm (44,000 kJ/kg), typical for many hydrocarbon fuels.Also shown in the Fig. 3 are the performance results for a ramjet and for afterburning turbojets with compressor pressure ratios of 30 and 4. For the turbojet calculations the compressor and turbine adiabatic efficiencies were again 0.85 and 0.90, respectively. The combustor and afterburner were assumed loss free (i.e., constant total pressure). The turbine inlet temperature was 3000 R (1670 K). It can be seen that the ideal PDE performance is fairly consistent over the Mach-number regime and that it is comparable with a nonideal, afterburning turbojet having a compressor pressure ratio of 4.0. For turbojets of a more realistic pressure ratio, the PDE shows significantly less specific impulse and (not shown) specific thrust. Compared with the ramjet, the performance advantages of a PDE are clear at Mach numbers below 3.0. Beyond this, there does not appear to be significant benefit. These PDE performance results are smaller than what is typically listed in the literature 1,2,10 ; however, because they represent computed results from a validated code, it can be argued that they are more representative of an idealization in the sense of being as good as can be expected.Other PDE applications can be examined in a straightforward manner using the map of Fig. 1. Examples would include gas-turbine topping cycles, afterburners (bypass duct or full flow), even ejectorbased cycles (if some assumptions are made regarding the work transfer process).Of the applications that have been examined, the process has been made easier through the use of Eq. (9); however, it should be kept in mind that for a given application, not all values of q 0 (and therefore enthalpy ratio) are possible. Also, the results shown represent a particular gasdynamic cycle. Other cycles, such as PDE cycles with valved exhaust (or low-loss, variable backpressure systems), or those employing shaped tubes can lead to different and possibly superior performance to that presented. 11,12 ConclusionsIt has been demonstrated in this work that idealized airbreathing PDE performance can be mapped onto a single plot of total pressure ratio vs total enthalpy ratio. It has further been shown that this format is useful in system studies because the PDE can be viewed as simply another component with straightforward input and output. The idealized PDE performance data were obtained from a onedimensional CFD code, and it has been shown that this is a more realistic approach than purely analytical methods. The performance shown is generally below that which has been previously reported for so-called idealized PDE ...

Optical and thrust measurement of a pulse detonation combustor with a coaxial rotary valve

“…Moreover, according to Cooper et al [31] and Sato et al [32], a PDE can achieve a dramatically high specific impulse by performing a partial fill of the propellant. Numerical analysis by Morris et al [23] and an experiment by Copper et al [33] showed that the expansion effect of by nozzle became dominant, like a steady flow, if the ambient pressure around a PDE was sufficiently low.…”

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

“…They showed that specific impulse I sp gradually increased as the fuel-fill fraction decreased. Cooper et al 11 proposed an empirical formula for I sp of partially filled detonation tubes by using previous experimental and numerical results with hydrocarbon fuels. Kasahara et al 12 experimentally verified the partialfill effect in a multi-cycle pulse detonation rocket engine (PDRE).When the fuel-fill fraction was greater than 0.130, the specific impulse was increased with the decrease of the fuel-fill fraction.…”

“…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.…”

Thrust Performance of Rotary-Valved Four-Cylinder Pulse Detonation Rocket Engine

“…The partial filling of the propellant in a detonation tube is the simplest way to increase the specific impulse. [11][12][13][14][15][16] In addition to the propellant in the detonation tube, purge gas, burned gas and air suctioned from the open end after the high-pressure burned gas has been blown down are compressed by a shock wave, and the specific impulse is increased by the compressed gases. In particular, the partial-fill effect is strongly dependent on the amount of suctioned air, because the air density of & air % 1:20 kg/m 3 at 1 atm and 300 K is higher than the burned gas density of & b % 0:104 kg/m 3 at 1atm.…”