Performance calculations for rotary positive displacement blowers require the use of several equations. These equations are presented below in the calculation order that is most logical. Typical equations are provided for both Roots and Sutorbilt.
Slip represents the amount of gas (air) which leaks back through the very small clearances which are present between the impellers and headplate, the impellers and the cylinder and between the impellers. The slip is the RPM (Revolutions per Minute) required to compensate for this leakage. 0.00474 Represents a constant that includes 7.8% for friction losses If you want to fine tune your brake horsepower calculation, the Gas Horsepower will be calculated separately from the Friction Horsepower. Gas Horsepower for a conventional rotary positive displacement blower can be calculated with the following equation: The formula that is used for a Whispair© unit (jet – assisted) is: F g must be obtained from a graph that has gear tip speed on the x-axis and F g on the y-axis. This curve is specific for a particular series of units or a specific unit and is typically proprietary for the blower manufacturer. Friction Horsepower can be calculated using several different strategies. All strategies require a Friction Horsepower provided by the manufacturer.
This friction horsepower is typically based on either Friction Horsepower per 1000 RPM or Friction Horsepower at the maximum RPM which in turn can be related to gear tip speed. Friction Horsepower per 1000 RPM can be defined as follows: Friction horsepower defined by the maximum friction horsepower at the maximum speed is: FHP/1000, FHP N, FHP max, and N max are supplied by the manufacturer.
Blower Sizing. When you have used the Application Sizing page. The blower selection part of the program will assume that want mechanical seals to contain. Roots blower sizing program. It is possible to investigate the property variations with time at different parts of the blowersystem with the computer program written.
Gear tip speed in fpm (feet per minute)can be calculated with the following equation. N Speed of shaft in RPM We can now calculate temperature rise on the unit. Temperature rise is a critical calculation since the blower has limits on thermal growth. Easy Driver Pack 5.23 Win 7 64 Bit. To much temperature rise and the impellers will expand into the headplates causing the unit to seize and possibly causing extensive damage to the unit.
Two formulas can be used. The first formula is only applicable to air and is as follows: The following formula can be used for any gas: T a Actual absolute inlet temperature in °R (°F+460) BHP Brake Horsepower F t Temperature rise factor from manufacturers table k Ratio of specific heats for a gas c p/c v P a Actual absolute inlet pressure in psia Q a Actual Inlet Volume in cfm Temperature rise exerts a couple additional limitations on rotary positive displacement blowers. Wifi Internet Password Hacking Software Software here. Most manufactures impose an average temperature rule as well as a reduction in maximum allowable temperature rise when inlet gas temperatures exceed ambient conditions. These two rules can be expressed mathematically as follows.