Positive displacement roots blower noise suppression

An apparatus comprising:

• a positive displacement roots blower having a pair of counter rotational rotors, each of the pair of counter rotational rotors having a plurality of respective lobes;
• an inlet structured to provide a compressible fluid to an intake side of the positive displacement roots blower;
• an outlet structured to discharge the compressible fluid from the positive displacement roots blower;
• and
• a pair of feedback loops having respective feedback loop inlets, venturis, and connecting tubes, the connecting tubes configured to divert a portion of the discharged compressible fluid from the outlet, the feedback loop inlets open to the positive displacement roots blower, the pair of feedback loops structured to increase a pressure between operating volumes between the plurality of lobes, each respective venturi defining a first chamber, a second chamber, and a constricted section formed therebetween, the first chamber and the second chamber having a flow-path cross-section that is larger than a flow-path cross-section of the respective connecting tube and the respective feedback loop inlet;
• and
• an air reservoir located proximate to the inlet for furnishing air to the operating volume;
• wherein each of the pair of counter rotational rotors rotates to a pressure equalization position in which adjacent lobes form a volume which is in fluid communication with a respective one of the pair of feedback loop inlets.

A method of reducing pressure pulsation in a positive displacement roots blower comprising:

• rotating a first rotor of a pair of intermeshed first and second rotors associated with the positive displacement roots blower, the positive displacement roots blower having an inlet, an outlet, and a passage connected to the outlet;
• supplying a working fluid to a volume created between adjacent lobes of respective first and second rotors;
• increasing a pressure of the volume created between adjacent lobes of the first rotor when the first rotor passes a venturi feedback loop inlet connected to the passage;
• wherein a venturi having a venturi ingress, a constricted section, and a venturi egress, is disposed between the venturi feedback loop inlet and the passage, a connecting tube in fluid communication with the venturi ingress and the passage, the connecting tube diverting a portion of fluid from the passage, wherein the venturi ingress and the venturi egress have a flow-path cross-section that is larger than a flow-path cross-section of the connecting tube and the venturi feedback loop inlet, respectively.