Theory Design Air Cushion Craft 2009 Part 14 ppt

... damage Total Damaged 41 31 19 5 18 21 5 14 0 Sinking 2 3 1 8 - 1 - 15 Total 43 34 20 13 18 22 5 15 5 16 Introduction to hovercraft Fig. 1. 14 British sidewall hovercraft HM- 218 in operation ... period, and later to 21m, to become the HM-2 21 (Fig. 1. 18). Contents Preface xi Acknowledgements xiii 1. Introduction to hovercraft 1 1 .1 Hove...

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... A /J J Air cushion wave-making drag 95 10 20 30 40 50 60 70 80 90 Fig. 3. 12(b) Wave-making drag coefficient for yawed craft, F r = 1.0. 10 20 30 40 50 60 70 80 90 Fig. 3. 12(c) ... (0.07656 Ib/ft 3 /32 .17 = 0.00 238 slug/ft 3 in imperial units) D c = nozzle discharge coefficient (2 .3. 4 item 5), D c = 0. 53 for 45° segment, L = peripheral len...

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... 119 X9.8N 16000 140 00 12000 10000 8000 6000 40 00 20 40 60 80 100 120 140 v(km/h) 2000 20 40 60 80 v(kn) Fig. 3.33 The drag and thrust curves of SR.N4. etc.) is included in the air profile ... achieve the designer's requirements in the speed range to 40 knots. Above this speed, an air cushion supporting most of the craft weight is most likely to...

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... T bt Units km/h N/m 2 m /s m m m m 26 .5 2813 5. 1 15 0 .52 54 0.2066 0.086 0.086 33.1 44.2 2789 2776 5. 1 15 5. 1 65 0 .58 23 0 .59 52 0.2008 0.1986 0.0 858 0.0868 0.0866 0.0868 55 .2 2787 5. 15 0 .55 99 0.2006 0.089 0.089 ... width W 4 fi c lJB e PA PC Q KG Z b,s a ft 5, t m m kgf/m N/m 2 m m deg deg m 13.7 13.2 3 .5 3.77 19.93 2630 0.00 757 1.27 0. 15 60 89 0.12 15. 9...

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... = 0 (6. 7) = [l = (i = 0 (6. 8) The expressions in equations (6. 6) and (6. 7) are the position derivatives, which can be obtained by wind tunnel experiments. Equation (6. 8) gives ... to air cushion and skirt F c = jetted thrust due to air leakage from cushion during turning manoeuvre F m = air momentum force z m = distance from ground to the centre...

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... in Figs 7. 2, 7. 9, 7. 10 and 7. 14. They are generally a series of almost circular trunks inflated iop b , extended to between 60 and 80% of cushion depth. For deep cushion craft, ... the cushion pres- sure acting on the stern skirt is uniformly distributed, may not be accurate, particu- larly in the case where craft are running on a water surface....

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... when the craft is running in high seas and the vertical motion of the craft is very large. In such a case, we can consider air leakage gap, air cushion pressure and air flow rate ... change of density of cushion air (g v ), i.e. due to the compressibility of the air cushion. In this case, we assume the change of air density in the cushi...

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... tank. Part of the outflow may be led directly into the cushion and another part via air ducts, the bow/stern bag and through into the air cushion. The distribution of air flow ... of air leakage and compressibility of cush- ion air will affect the change of cushion pressure and flow rate. Figure 8.42 shows such dependency between the craft dra...

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... of cushion air compression is too small to change the air flow rate and fluctuate the cushion pressure. This is not true for full-scale craft, especially for larger hovercraft ... C.G. H s Cushion depth B c Cushion beam 0.1 0.2 0.3 0.4 h G /B Fig. 10. 4 Vertical CG position compared to ACV cushion heights. 358 Design methodology and performance...

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... various Hovercraft Craft Country Type Cushion Cushion Craft Cushion Flow Q bar length area weight ^(t) pressure rate 4(m) 5 c (m 2 ) /> c (N/m 2 ) Q (mVs) HM.216 UK SES 11. 95 58.29 ... loss. It is important to remember that cushion air thrusters for ACVs, and cushion vent- ing systems in the case of SES, absorb part of the cushion air flow or l...

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... characteristic of air clearance, then the operation point at various craft weights and fan speeds can be obtained as shown in Fig. 12. 13. Figures 12. 12 and 12. 14 identify the ... the cushion pressure/length ratio pjl c . Due to support of the major part of the craft weight by the cushion, an SES structure is less highly loaded and can there...

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... rotors Air cushion craft Jeff (A) Q-FAN Free propeller theory I I I I I I I I I I I I I 3 45678910 2 Diameter parameter (DVl.OOO/P) 3 4 5 6 7 8 9 100 Fig. 15.10 77A/vs/?/A/ 05 [4]. ã cushion ... thrust developed from this air jet is T=Qp A (V } - V c ) where V c is the craft speed air speed and V } the air jet speed (15.44) 500 Propulsion system desi...

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... system design where C, is the discharge coefficient for the air jet under the skirt segments. At zero speed in still air equation (15.44) reduces to T=AC ] 2p c (15.45) Cushion ... are fixed, the designer has to make a choice of what craft operating condition should be optimized. Craft cruising conditions may be taken as a start. At lower craft sp...

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... well- designed installations. Now rjj = (T- Z>j) VJE (from 15. 91) = m[V- } -(\-w)V c - C Di 0.5 IVR V c (1 - vv)] VJE (15. 98) so by following the steps from (15. 93) to (15. 96), ... N/S 2 ( kw cm 2 ) Fig. 15. 44 A/ ss boundaries on plot of water jet thrust vs craft speed. 562 Propulsion system design ôss = n e 5 /(g X NPSH) 075 (15. 114) =...

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... during 155 with air cushion compartmentation on rigid surface 164 with air cushion compartmentation on water 164 without air cushion compartmentation on water 164 High-performance ... intake for air cushion vehicles. Hovering Craft & Hydrofoil, September 1968. 616 References 97. Tang ZF. Selection and design of lift fans on hovercraft....

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