Jet performance curves

Figure 16.3 A typical vacuum steam jet performance curve.

The thermal energy savings depend on the available motive-steam pressure end the compression ratio. From steam-jet performance curves, the ratio of suction vapor to motive steam flow rates is obtained and matched with the total steam requirements for the evaporator. The difference in the low rates between the existing evaporator steam without thermal compression and motive steam is the steam savings. The motive steam rate is the new steam consumption. The... 

Install a "Piccolo" as shown in Figure 13-5. The Picolo is nothing more than a pipe with calibrated holes. It is also obtained from the jet manufacturer. Remove one plug at a time. From a chart that comes with the Picolo, read the air flow to the jet based on the pressure in the mixing chamber and the hole size. Using the Picolo, one can generate a jet performance curve and compare it to the original performance curve. 

Compare the observed vacuum with the predicted vacuum at zero air flow as shown on the manufacturer s jet performance curve. 

I have rather implied up to now that a steam jet, depending on its mechanical condition, will develop a fixed compression ratio. This is not true. For one thing, the gas rate through the jet will influence its suction pressure. This is shown on the typical jet performance curve in Fig. 23.3, which is drawn for a constant discharge pressure of 100 mm Hg. 

Jet performance curve Issued by the steam jet manufacturer, describes the vacuum a jet should pull at various gas flow rates. 

Figure 6-110. Typical performance curves for steam jet ejectors, liquid ring pumps, and rotary piston oil-sealed pumps. By permission, Ryans, J. L. and Roper, D. L. [24],...

Calculations, Performance Curves, and Other Measurements in Jet Systems... 

To identify equipment constraints, equipment details must be modeled in simulation. For example, column geometry and internal data need to be provided so that column loadings, for example, jet flooding under maximum capacity operation and weeping for turndown operation, can be obtained. Compressors and turbines are modeled with performance curves, which predict head, speed, and efficiency. The design performance curves must be tuned to mimic test run data. This allows a more realistic prediction of performance at different loads and/or process conditions. 

Figure 7.3 shows theoretical impactor performance when a number of parameters are varied, including jet-to-plate spacing, jet Reynolds number, and throat length-to-width ratio. These curves indicate that impactor efficiency is fairly insensitive to Reynolds number in the range 500 < Re < 3000 and that impactor efficiency is also relatively independent of S/W and T/W ratios, except for small values of S/W. 

A PC-based controller was developed to operate the valves for fuel flow modulation in the various zones. The valve hardware and controller were bench tested in a jet-fuel wet-bench test facility to verify valve performance and controller effectiveness. Valve flow tests indicate stable and repeatable valve operation over the range of flow conditions tested. The valve flow curves demonstrated acceptable proportionality at lower mass flows, but became slightly nonlinear at higher mass flow conditions as illustrated by Fig. 17.6. 

---