which may be seen on the diagram. As the gas flow passes through the exhaust system (Part 6), small forward forces may act on the inner cone or bullet, but generally only rearward forces are produced and these are due to the 'drag' of the gas flow at the propelling nozzle.
6. It will be seen that during the passage of the air through the engine, changes in its velocity and pressure occur (Part 2). For instance, where a conversion from velocity (kinetic) energy to pressure energy is required the passages are divergent in shape, similar to that used in the compressor diffuser. Conversely, where it is required to convert the energy stored in the combustion gases to velocity, a convergent passage or nozzle, similar to that used in the turbine, is employed. Where the conversion is to velocity energy, 'drag' loads or rearward forces are produced; where the conversion is to pressure energy, forward forces are produced. Part 2, fig. 2-3 illustrates velocity and pressure changes at two points on the engine.
计算推力的方法
7．如果已经知道特定气流段进口和出口的面积、压力、速度和质量流量，就可计算发动机或发动机的任何气流段的推力或气体载荷。
9．为了计算一特定流段的总推力，必须计算进口和出口处的总的推力。总推力就是所得到的这两个值之差。
8.图20-1中表示的推力的分布可借助于依次考虑每一部件并采用一些简单的计算方法来计算。发动机产生的推力主要是流过发动机的空气的质量及其速度增量的乘积(即牛顿第二运动定律)，不过，某个特定流段的进口和出口之间的压差对发动机的总推力具有影响，计算时必须加以考虑。
Thrust distribution
METHOD OF CALCULATING THE THRUST the compressor and the conditions at the outlet from FORCES the compressor. Since the pressure and the velocity at the inlet to the compressor are zero, it is only
7.
The thrust forces or gas loads can be calculated necessary to consider the force at the outlet from thefor the engine, or for any flow section of the engine, compressor. Therefore, given that the compressor-provided that the areas, pressures, velocities and mass flow are known for both the inlet and outlet of OUTLET Area (A) = 182 sq.in.
the particular flow section. Pressure (P) = 94 lb. per sq.in. (gauge)
8.
The distribution of thrust forces shown in fig. 20-Velocity (vJ) = 406 ft. per sec. 1 can be calculated by considering each component Mass flow (W) = 153 lb. per sec.in turn and applying some simple calculations. The
The thrust
推力
thrust produced by the engine is mainly the product of the mass of air passing through the engine and the MVJ
= (A xP) +. 0velocity increase imparted to it (i.e. Newtons Second gLaw of Motion), however, the pressure difference 10．推力的计算采用下列公式：
式中
A=气流段的面积，单位为平方英寸
P=压力，单位为磅／平方英寸
W=质量流量，单位为磅／秒
vJ=气流的速度，单位为英尺／秒
g=重力常数，32.2英尺／平方秒
153 x 406
between the inlet to and the outlet from the particular = (182 x 94) +. 0 flow section will have an effect on the overall thrust
32 of the engine and must be included in the calculation.
= 19,049 lb. of thrust in a forward direction.
9.
To calculate the resultant thrust for a particular
flow section it is necessary to calculate the total
thrust at both inlet and outlet, the resultant thrust
being the difference between the two values
obtained.
10.
Calculation of the thrust is achieved using the
following formula:
MVJThrust = (A xP) + g
Where A = Area of flow section in sq.in.
P = Pressure in lb. per sq.in.
Diffuser duct
W = Mass flow in lb. per sec.
发动机推力计算
11．当采用上述方法计算不同部件上的单个推力载荷时，假设发动机是静止状态的。飞机前飞速度对发动机推力的影响将在第21章中讨论。为方便起见，在下列计算中，“g”取32。为了帮助计算，有关的位置用许多小的简图来表示。
13. The conditions at the diffuser duct inlet are the vJ = Velocity of flow in feet per sec.
same as the conditions at the compressor outlet, i.e.
g = Gravitational constant 32.2 ft. per 19,049 lb.
sec. per sec.
Therefore, given that the diffuser--OUTLET Area (A) = 205 sq.in. Pressure (P) = 95 lb. per sq.in. CALCULATING THE THRUST OF THE ENGINE (gauge) Velocity (vJ) = 368 ft. per sec.
11. When applying the above method to calculate Mass flow (W) = 153 lb. per sec.the individual thrust loads on the various components it is assumed that the engine is static. The effect of The thrust aircraft forward speed on the engine thrust will be WVJ
= (A xP) +.19,049dealt with in Part 21. In the following calculations 'g' g
is taken to be 32 for convenience. To assist in these calculations the locations concerned are illustrated 153 x 368
= (205 x 95) +.19,049by a number of small diagrams.
32
Compressor casing = 21,235 - 19,049
12. To obtain the thrust on the compressor casing it
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