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13.3 Establish Engine Performance Data

 

 

423

Table 13.2. 30,000-ft altitude (ρ = 0.00088 slug/ft3, σ = 0.37) maximum climb

 

 

 

 

 

 

 

 

True air speed in knots

50

100

150

200

 

V in mph

57.54

115.08

172.62

230.16

 

SHPunistall from Figure 10.43a × 1,075

462

505

516

548

 

J = 0.0046 × knots

0.264

0.528

0.792

1.055

 

Cp = 0.000116 × SHP

0.138

0.150

0.154

0.163

 

ηprop (from Figure 10.35)

0.380

0.630

0.782

0.83

 

Uninstalled thrust, T (lb)

1,145

1,037

876

741

 

Installed thrust (lb)

1,098

996

842

712

 

Sfc (lb/hr/SHP) (Figure 10.43b)

0.475

0.472

0.465

0.445

 

Fuel-flow rate (lb/hr)

220

238

240

244

 

 

 

 

 

 

 

13.3.4 Turboprop Engine Performance

This type of turboprop engine is used in both civil and military aircraft design. The power settings are as in civil aircraft applications. Sizing of the Tucano class turboprop trainer aircraft requires a matched, installed engine TSLS = 4,000 lbs. Section 10.11.2 presents the generic, uninstalled, turboprop engine performance in nondimensional form. Section 10.11.4 works out the propeller thrust from the turboprop engine and establishes that the rated engine power of SHPSLS = 1,075 SHP (uninstalled) would develop as installed TSLS = 4,000 lbs.

Thrust computations from the turboprop SHP is repetitious work, as shown in Section 10.11.4. In this section, one computation each at the maximum climb rating and the maximum cruise rating, both at a 30,000-ft altitude for four speeds, are given in Tables 13.2 and 13.3, respectively.

Takeoff Rating (Turboprop): Standard Day

The installed takeoff thrust of a turboprop is plotted in Figure 10.40. It is repeated in this section as Figure 13.5 to keep all available thrust graphs in one section. At the takeoff rating, engine power is kept nearly constant at a speed when the enroute climb can start at a reduced power setting of the maximum climb rating. The psfc of the turboprop at takeoff is 0.5 lb/hr/shp, based on uninstalled power. Therefore, at SHPSLS, the fuel-flow rate is 0.5 × 1,075 = 537.5 lb/hr. The intake airmass

Table 13.3. 30,000-ft altitude (ρ = 0.00088 slug/ft3, σ = 0.37) maximum cruise

True air speed in knots

100

200

250

300

V in mph

115.08

230.16

287.70

345.24

SHPunistall = Figure 10.43a × 1,075

413

440

462

484

J = 0.00533 × knots

0.528

1.055

1.320

1.583

Cp = 0.000116 × SHP

0.123

0.131

0.138

0.144

ηprop (from Figure 10.35)

0.66

0.81

0.82

0.81

Uninstalled thrust, T (lb)

888

582

494

426

Installed thrust (lb)

852

558

474

409

Sfc (lb/hr/SHP) (Figure 10.44b)

0.46

0.45

0.44

0.43

Fuel flow rate (lb/hr)

190

198

204

208

 

 

 

 

 

424

Aircraft Performance

Figure 13.5. Available turboprop thrust at takeoff rating from a 1,100-SHP engine

flow at SHPSLS is 0.011 × 1,075 = 11.83 lb/s (the specific power of 0.11 lb/s/SHP is provided in Section 10.2.2).

Maximum Climb Rating (Turboprop): Standard Day

Figure 10.43a shows the uninstalled maximum climb SHP in nondimensional form and fuel consumption (sfc) up to a 30,000-ft altitude for four TAS from 50 to 200 kts. Following the same procedure as described in Section 10.11.4, the available installed thrust and fuel-flow rates at the maximum climb rating are worked out using a 4% loss of thrust due to installation effects. A sample computational table at a 30,000-ft altitude is in Table 13.2.

Figure 13.6 plots the available installed thrust and fuel flow at the maximum climb rating from sea level to a 30,000-ft altitude. The specified requirement of the initial climb rate for the example in this book is 4,500 ft/min.

Maximum Cruise Rating (Turboprop): Standard Day

Figure 10.44 shows the maximum cruise SHP in nondimensional form and fuel consumption (sfc) for speeds from the TAS of 50 to 300 kts and an altitude up to

Figure 13.6. Thrust and fuel flow at maximum climb rating

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