Moderator: Mike Everman

Post Reply
WebPilot
Posts: 3716
Joined: Tue Dec 07, 2004 6:51 pm
Antipspambot question: 0
Location: 41d 1' N 80d 22' W

Post by WebPilot » Mon Sep 21, 2009 7:35 pm

The performance of a Solar PJ32 pulsejet engine, which is a 1/5-scale model of the Argus V-1 pulsejet engine developed for the Navy in 1951, is evaluated under static conditions and
compared with that of a pulsed-detonation engine (PDE) firing at similar inlet and operating
conditions. The pulsejet has a fuel-flow operating range of 2.5-4.5 lbm/min, which
corresponds to a thrust range of 40 lbf (at lean out) to 102 lbf (at flood out). Thrust is
calculated from combustion-chamber pressure histories and agrees with measured thrust
within 5-10%. Peak combustion-chamber head pressures range from 8 to 20 psig, while
significantly higher pressures (80-120 psig) are attained in PDEs. Airflow at the inlet of the pulsejet is measured and used to calculate specific thrust and equivalence ratio. Specific thrust ranges from 40-100 lbf-s/lbm over the range of fuel flows from lean to rich conditions.

A similarly operating PDE has a specific thrust around 120 lbf-s/lbm, making the PDE more
efficient in terms of air flow. The pulsejet equivalence ratio ranges from 0.6-1.0, with
rated/peak thrust occurring at rich conditions. Typical fuel-specific impulse (Isp) for the
pulsejet is 1400-1500 s for rated thrust conditions, whereas PDE performance (with a fill
fraction of 1) is around 1800 s. For the PDE operating in the same fill fraction range as the
pulsejet (~0.1), PDE Isp is estimated to be 6000-8000 s making the PDE cycle far more
efficient and desirable at comparable conditions.
For this pulsejet 8-20 psig is another way of saying peak pressure ratios of 1.544 to 2.361 relative to ambient.

For this PDE peak pressures ratios are 6.44 to 9.16 relative to ambient.

The higher the avg pressure over one cycle, the greater the thrust.
Image

WebPilot
Posts: 3716
Joined: Tue Dec 07, 2004 6:51 pm
Antipspambot question: 0
Location: 41d 1' N 80d 22' W

Re: ♑

Post by WebPilot » Wed Apr 14, 2010 8:31 pm

    Assessment of the Performance of a Pulsejet and
   Comparison with a Pulsed-Detonation Engine


          Paul J. Litke and Frederick R. Schauer
Air Force Research Laboratory, Propulsion Directorate, Wright-Patterson AFB, OH 45433
              Daniel E. Paxson*
   NASA Glenn Research Center, 21000 Brookpark Road, Cleveland OH 44135
                 and
          Royce P. Bradley and John L. Hoke
     Innovative Scientific Solutions, Inc., Dayton, OH 45440
Image

Thor
Posts: 11
Joined: Sun Aug 31, 2008 4:28 pm

Re: ♑

Post by Thor » Fri May 14, 2010 10:24 am

A really good read on the research results on this topic.

For those who has a similar interest I attached the pdf doc:
AIAA-2005-0228.pdf
(1.54 MiB) Downloaded 279 times
Good reading.

PyroJoe
Posts: 1743
Joined: Wed Aug 29, 2007 5:44 pm
Antipspambot question: 125
Location: Texas

Re: ♑

Post by PyroJoe » Fri May 14, 2010 3:12 pm

Yikes,

A comparison in which it is admitted:
"Performance results will be shown and compared to data from a
statically operated PDE run at stoichiometric conditions with similar length scales."

Probably went through great labor to assure the PDE runs stoichiometric using a fair ratio of brisant fuel such as hydrogen.

In comparison the PJ engine tested was designed in 1951 and fueled with "100 Octane, low-lead Aviation
Grade Gasoline (Avgas)"

Gee, I wonder which one will have an absurdly higher peak pressure? Which one will have a "slow mode of
combustion"

"A similarly operating PDE has a specific thrust around 120 lbf-s/lbm, making the PDE more
efficient in terms of air flow."
To this I ask the question: has anyone observed a self aspirating static PDE capable of inducing airflow, let alone efficient airflow?

IMO a quick review of the lines of the PJ32 quickly reveal it should not be tested statically.

It is sad for me to see such things, as I often think of engines that can transition between deflag. and PDE mode. Maybe pulling from the best characteristics of each type.

Instead we see stuff like this with one toe in a misunderstood past and one foot to deep in the lab, resulting comparison of a engine that won't sustain without considerable help, and one that is tested out of context.

A backyard builder of solid rocket motors would find most of this a laughable whiz in the wind "in comparison".

Apologies for the negative tone of this post. Moderators feel free to can my post if it is to far out of bounds.

Joe

Thor
Posts: 11
Joined: Sun Aug 31, 2008 4:28 pm

Re: ♑

Post by Thor » Fri May 14, 2010 4:16 pm

PyroJoe wrote:Yikes,

A comparison in which it is admitted:
"Performance results will be shown and compared to data from a
statically operated PDE run at stoichiometric conditions with similar length scales."

Probably went through great labor to assure the PDE runs stoichiometric using a fair ratio of brisant fuel such as hydrogen.

In comparison the PJ engine tested was designed in 1951 and fueled with "100 Octane, low-lead Aviation
Grade Gasoline (Avgas)"

Gee, I wonder which one will have an absurdly higher peak pressure? Which one will have a "slow mode of
combustion"

"A similarly operating PDE has a specific thrust around 120 lbf-s/lbm, making the PDE more
efficient in terms of air flow."
To this I ask the question: has anyone observed a self aspirating static PDE capable of inducing airflow, let alone efficient airflow?

IMO a quick review of the lines of the PJ32 quickly reveal it should not be tested statically.

It is sad for me to see such things, as I often think of engines that can transition between deflag. and PDE mode. Maybe pulling from the best characteristics of each type.

Instead we see stuff like this with one toe in a misunderstood past and one foot to deep in the lab, resulting comparison of a engine that won't sustain without considerable help, and one that is tested out of context.

A backyard builder of solid rocket engines would find most of this a laughable whiz in the wind "in comparison".

Apologies for the negative tone of this post. Moderators feel free to can my post if it is to far out of bounds.

Joe
Canceled

Post Reply