Hello Larry --
Larry Cottrill wrote:
Would it be a simple matter for you to give us your famous 'Acoustic Temperature' value for this pipe?
I gave you one better wrt. acoustic temperature - I put
Lady Anne through her paces in the pulsejet model.
As you asked for it, the acoustic temperature is a rather anemic
319,5 °K. This is not surprising if you were
to consider this motor in the same context as your previous offerings; the combustor section that you have
adopted for the FWE-series motors is apparently unable to support higher values of OAT. Sorry about that!
Setting acoustic temperature aside, you may be interested to read about this motor's other characteristics:
Note: I used Larry's drawings as a baseline for modeling, and substituted James' changes where available.
Code: Select all
Thrust and temperature data is referenced to ICAO standard day, sea-level at 15 °C
Physical length 547,0 mm : interior length
Acoustic length 563,8 mm : std. correction
Fundamental (OF1) 317,7 Hz : reported before
Temperature (OAT) 319,5 °K : see note for N1
S1 (step ratio) 4,04:1 : relatively large, < 3 typical for smaller motors
S2 (forward bias) > 2,50:1 : overexpanded; optimum exit diameter 49,5-50,5 mm
N1 (lockup ratio) 6,00:1 : acoustic temperature synchronised for lockup
E2 (gate ratio) 3,02:2 : exact integer ratio, e.g., 3:2, is preferred
E3 (tail ratio) ~ 8,5 : relatively(!) short, but motor runs out well
Thrust division 30:70 : relative contributions (%) inlet and exhaust
Maximum thrust 1280 g : NOC method (rigid combustor model) S2 = 2,45
Minimum thrust < 150 g : may require a precison fuel injection system
SFC at maximum < 1,8 kg/kgf/hr : range 1,6-1,8, for equivalence ratio 1,2-1,3
Maximum thrust 1410 g : NOC method (rigid combustor model) S2 = 2,50
SFC at maximum < 1,8 kg/kgf/hr : range 1,6-1,8, for equivalence ratio 1,2-1,3
Ultimate thrust 2050 g : NOC method (rigid combustor model) S2 = 2,50
SFC at ultimate < 1,4 kg/kgf/hr : equivalence ratio < 1,3; combustor saturated*
Observed thrust 1200 g : NOC method (rigid combustor model) S2 = 2,50**
SFC at observed < 2,2 kg/kgf/hr : range 2,0-2,2, for equivalence ratio 1,2-1,3
SFC at observed < 1,8 kg/kgf/hr : stoichiometric equivalence ratio ~ 0,95-1,05
*ultimate thrust assumes combustor is 100% saturated; may require special hardware
**observed thrust model incorporates visual evidence from James' latest photograph
Best regards,
M.