Total pressure loss

Combustors All gas turbine combustors perform the same function They increase the temperature of the high-pressure gas at constant pressure. The gas turbine combustor uses veiy little of its air (10 percent) in the combustion process. The rest of the air is used for cooling and mixing. The air from the compressor must be diffused before it enters the combustor. The velocity leaving the compressor is about 400-500 ft/sec (130-164 m/sec), and the velocity in the combustor must be maintained at about 10-30 ft/sec (3-10 iTi/sec). Even at these low velocities, care must be taken to avoid the flame to be carried downstream. To ensure this, a baffle creates an eddy region that stabi-hzes the flame and produces continuous ignition. The loss of pressure in a combustor is a major problem, since it affecls both the fuel consumption and power output. Total pressure loss is in the range of 2-8 percent this loss is the same as the decrease in compressor efficiency. 

The loss of pressure in a eombustor is a major problem, sinee it affeets both the fuel eonsumption and power output. Total pressure loss is usually in the range of 2-8% of statie pressure. This loss is the same as a deerease in eompressor effieieney. The result is inereased fuel eonsumption and lower power output that affeets the size and weight of the engine. 

The choice of these values is arbitrary. In practice, the cooling fraction will depend not only on the combustion temperature but also on the compressor delivery temperature (i.e. the pressure ratio), the allowable metal temperature and other factors, as described in Chapter 5. But with ip assumed for the first nozzle guide vane row, together with the extra total pressure loss involved (k = 0.07 in Eq. (4.48)), the rotor inlet temperature may be determined. These assumptions were used as input to the code developed by Young [11] for cycle calculations, which considers the real gas properties. 

This total pressure loss is not necessarily required in determining the frictional losses in the system. It is necessary when establishing gravity flow or the pumping head requirements for a complete system. 

In the usual case, liquid and gas do not issue from the reboiler with equal velocities, k. Total pressure loss. 

Actual fP/min (at fan inlet)] [Total pressure loss (in. water) through air-cooled outside fins]... 

Note that for straight duct flow at constant cross-section, the total and static pressures decrease together (constant resistance). At the contraction section, the total pressure decreases very litde, but static pressure is converted to velocity pressure, because static and velocity pressures are mutually convertible. At the sudden enlargement, the process of changing the velocity pressure to static pressure is inefficient, and a total pressure loss occurs. AtJ the static pressure is 0, and the total pressure is the velocity pressure as the gas stream leaves the duct. 

Total values calculated in (2). This is the system total pressure loss, static losses plus velocity head. 

Total Pressure Loss. Using Table 4-110 and Equations 4-150 and 4-151, the pressure loss across the turbine motor can be determined for the various circulation flowrates and the mud weight of 16.2 Ib/gal. These data together with the above bit pressure loss data are presented in Table 4-113. Also presented in Table 4-113 are the component pressure losses of the system for the various circulation flowrates considered. The total pressure loss tabulated in the lower row represents the surface standpipe pressure when operating at the various circulation flowrates. 

Figure 4-195. 5 /4-in. liner, total pressure loss versus flowrate, Example 2. (Courtesy Smith International, Inc.)... 

Total Pressure Loss. Since bit life is not an issue in a short deviation control motor run operation, it is desirable to operate the positive displacement motor at as high a power level as possible during the run. The motor has a maximum pressure loss with which it can operate. This is 580 psi (see Table 4-114). It will be assumed that the motor will be operated at the 580 psi pressure loss in order to maximize the torque output of the motor. To obtain the highest horsepower for the motor, the highest circulation flowrate possible while operating within the constraints of the surface mud pump should be obtained. To obtain this highest possible, or optimal, circulation flowrate, the total pressure losses for the circulation system must be obtained for various circulation flowrates. These total pressure losses tabulated in the lower row of Table 4-117 represent the surface standpipe pressure when operating at the various circulation flowrates. 

Pump Limitations. Table 4-116 shows there are six possible liner sizes that can be used on the Model E-700 mud pump. Each liner size must be considered to obtain the optimum circulation flowrate and appropriate liner size. The maximum pressure available for each liner size will be reduced by a safety factor of 0.90. The maximum volumetric flowrate available for each liner size will also be reduced by a volumetric efficiency factor of 0.80 and an additional safety factor of 0.90. Thus, from Table 4-116, the allowable maximum pressures and allowable maximum volumetric flowrates will be those shown in Figures 4-207 through 4-212, which are the liner sizes 5j-, 6, 6-[, 6- and 7 in., respectively. Plotted on each of these figures are the total pressure losses for the various circulation flowrates considered. The horizontal straight line on each figure is... 

Figure 26.3 shows the relationship between port diameter and fluid velocity at 4 and 7 m/s and highlights the nominal maximum velocities for various plates. As the flow through the machine increases, the entry and exit pressure losses also increase. The nominal maximum flow rate for a plate heat exchanger limits these losses to an acceptable proportion of the total pressure losses, and is therefore a function not only of the port diameter but... 

Example 27.4 The duct specified above has in it two bends, for which a pressure loss factor of 0.28 is shown in the tables ([4], Table C4). What is the total pressure loss ... 

Flight speeds of Mach.2.5 to 10 were examined and compared to those of a conventional ramjet. Performance was better than could be expected, because even with large inlet and wave total pressure losses, at high Mach number the overall cycle pressure ratio was well matched to the temp ratios obtd by combustion (Ref 17, p llg)... 

Once the total pressure loss is calculated, we can determine the de-rating factor to be multiplied by the effective relieving capacity of the SRV, which can be found on its tag plate. 

Each of these pressure losses is given derived equations, and each is a separate entry to be added as an algebraic sum for the total pressure loss. This of course is similar to Eqs. (6.14) and (6.15). 

The inlet section decreases the area of the fluid stream, causing the velocity to increase and the pressure to decrease. The low pressure is measured in the center of the cylindrical throat since the pressure will be at its lowest value, and neither the pressure nor the velocity is changing. The recovery cone allows for the recovery of pressure such that total pressure loss is only 10% to 25%. The high pressure is measured upstream of the entrance cone. The major disadvantages of this type of flow detection are the high initial costs for installation and difficulty in installation and inspection. 

Pressure drop is total pressure loss across the meter at 100% flow rate in inches of water column. 

In the first experimental installation, the fluid was placed initially in a reservoir and then forced out imder pressm-e exerted by nitrogen into an axisymmetrical or two-dimensional capillary. In this system, the total pressure loss is monitored [11, 14]. This is determined by using a Bourdon-type pressure gauge. The mass flow is measured by weighing and timing. 

---