Aircraft Design: Synthesis and Analysis - part 7

chứ không phải bằng cách cung cấp một thành phần lực đẩy. 2. Các kết quả được hiển thị ở đây đối phó với dòng chảy inviscid trên cánh không phẳng. Có một khác biệt nhỏ trong tải tối ưu trong trường hợp nhớt do để kéo nhớt nâng phụ thuộc vào. | actually be able to produce mush more thrust at low altitudes and speeds but they are limited often in software to lower thrust levels to extend engine life and reduce maximum loads. Thus some supersonic engines show very little reduction in thrust from sea-level static conditions to Mach 1 at 30 000 ft. Actual engine performance differs from the basic engine data in a number of ways. The air bled from the compressor for air conditioning the power extracted for hydraulic pumps and alternators and inlet and exhaust duct losses reduce engine thrust. The exact amount depends of course on the requirements of the accessories the engine size and the inlet and duct design but reasonable estimates for conventional inlets are 1 Thrust is reduced by below engine specification levels 2 Specific fuel consumption is increased by During the take-off the air conditioning bleed is often shut-off automatically to avoid the thrust loss. The remaining thrust loss is about 1 . If a long or curved S-bend inlet is involved as in center engine installations an additional thrust loss of 3 and a specific fuel consumption increase of 1-1 2 may be assumed. This additional loss applies only to the affected engine. Specific Fuel Consumption and Overall Efficiency The engine performance may be described in several ways. One of the useful parameters is specific fuel consumption or . For turbojets and fans the . is usually expressed as the thrust specific fuel consumption or . It is defined as the weight of the fuel burned per unit time per unit thrust. In English units . is usually quoted in lbs of fuel per hour per lb of thrust or just lb hr lb or 1 hr. In SI units the . is sometime expressed in kg hr kN. For turboprop or piston engines the . is often expressed as a power specific fuel consumption . weight of fuel per unit time per unit power delivered to the propeller. This quantity is often denoted . for brake-power . and has units of

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