The charts on each worksheet show the minimum and maximum values that can be measured for the Low Flow Air Test Stand. The measured values are plotted versus part pressure ratio. Part pressure ratio is defined as the absolute part inlet pressure, P3, divided by the local barometric pressure, Pa. Pr = P3/Pa. Thus the test stand is connected to the inlet of the part by the use of a plenum/fixture and the part will exhaust to atmospheric conditions. The charts are based on dry air at T3 = 529.67R = 70F and a local barometeric pressure, Pa = 14.7psia.

##### Step 1

To determine which model or hybrid model is appropriate for your needs a complete list of all passages to be tested is required. The list should include the following items.

- Part Number
- Passage or Test Description (A Part Number may have more than one test. Example, PN: 1, leading edge and trailing edge.
- Control Pressure (see below).
- Type and min./max. limit for the measured parameter (see below).

If you would like Flow Systems to select or derive a hybrid configuration for you, please forward the above information to mcarter@flowsystemsinc.com.

##### Step 2

The control pressure at the part may be expressed in one of the following methods:

- Pressure ratio, Pr=P3/Pa, which is a dimensionless ratio of absolute pressures.

No manipulation is required. Measured parameters are plotted versus Pr. - Pressure drop across the part, Dp = P3 – Pa

Pr = P3/Pa = (Dp+Pa)/Pa- If Dp is in units of inches of water column then; Pr = P3/Pa = [(0.036063)Dp+Pa]/Pa where Pa is in units of psia.
- If Dp is in units of inches of mercury then; Pr = P3/Pa = [(0.4912)Dp+Pa]/Pa where Pa is in units of psia.

- Part absolute pressure, P3.

Pr = P3/Pa- If P3 is in units of psia then; Pr = P3/Pa where Pa is in units of psia.
- If P3 is in units of inches of mercury then; Pr = [(0.4912)P3]/Pa where Pa is in units of psia.

Conversion factors for other pressure units and a Conversion Calculator can be found on the Worksheet named Unit Conversions in this Workbook.

##### Step 3

A chart is provided for each of the following measured parameters. In parenthesis are the OEM’s who measure each parameter.

- Effective Area, Ae, in units of square inches (Solar Turbines, General Electric Aircraft Engines, General Electric Gas Turbines, Rolls Royce, Allison.)
- Flow Parameter, m(T3)^.5/P3, in units of [lbm*R^.5/(sec*psia)] (Solar Turbines, General Electric Aircraft Engines, Pratt & Whitney)
- Mass Flow, m, in units of lbm/sec (General Electric Aircraft Engines)
- Reduced Mass Flow, m(T3)^.5/P3, in units of [kg*K^.5/(sec*bar,a)] (Alstom Power)

If you need help in determining the appropriate configuration for your application please forward the list of information required in Step 1 to mcarter@flowsystemsinc.com.

##### Low Flow Air Test Stand Configurations:

**Standard Configuration (0.031″ to 0.177″)**

**Option 2 Configuration (0.031″ to 0.250″)**