Roots Vacuum Pump Cooling Air Port and Discharge Groove Design
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional three-lobed spar rotor or helical rotor type Roots vacuum pumps face issues with reduced volumetric efficiency, mechanical efficiency, and high noise levels due to temperature increases and communication between inlet and outlet ports, leading to increased costs for noise reduction and efficiency loss.
Innovation Solution
A Roots vacuum pump design with a casing featuring an inlet port and outlet port positioned 120° apart, with outside air or cooling air feed ports at a 90° return from the outlet port side, and discharge grooves covering 2% to 5% of the closed space volume, preventing port communication and reducing internal leaks and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the feed port for outside air or cooling air is provided in a part of the area of the positive displacement angle, then the temperature of the casing is reduced, but the volumetric efficiency and mechanical efficiency are reduced and noise increases to 90 dB or above
Solution Approach 1:
The feed port is positioned at a specific location (90° return from outlet port position) rather than distributed throughout the positive displacement angle area. This localized placement provides cooling where most needed while minimizing interference with the compression process and maintaining volumetric efficiency.
2Temperature
If the feed port for outside air or cooling air is provided in a part of the area of the positive displacement angle, then the temperature of the casing is reduced, but noise increases to 90 dB or above requiring additional noise reduction installation
Solution Approach 1:
The feed port is positioned at a specific location (90° return from outlet port position) rather than distributed throughout the positive displacement angle area. This localized placement provides cooling where most needed while minimizing interference with the compression process and maintaining volumetric efficiency.
3Temperature
If the feed port for outside air or cooling air is provided in a part of the area of the positive displacement angle, then the temperature of the casing is reduced, but the costs increase due to required noise reduction installation
Solution Approach 1:
The feed port is positioned at a specific location (90° return from outlet port position) rather than distributed throughout the positive displacement angle area. This localized placement provides cooling where most needed while minimizing interference with the compression process and maintaining volumetric efficiency.
4Temperature
If the feed port for outside air or cooling air is provided in a part of the area of the positive displacement angle, then the temperature of the casing is reduced, but the mechanical efficiency is reduced due to high-temperature gas leakage through minute gaps
Solution Approach 1:
The feed port is positioned at a specific location (90° return from outlet port position) rather than distributed throughout the positive displacement angle area. This localized placement provides cooling where most needed while minimizing interference with the compression process and maintaining volumetric efficiency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design improves volumetric efficiency by 20% to 40%, reduces energy consumption by 5% to 10%, decreases surface temperatures by 10° to 20°, and lowers noise levels by 5 dB to 10 dB compared to conventional pumps.
Implementation Method 1
a casing at an outlet port side has a temperature ranging from about 120° C. to about 150° C. by heat of compression when pressure difference of −45 kPa or above is caused between an inlet port side and the outlet port side during operation of the pumps
Implementation Method 2
the casing is provided with a feed port through which outside air or cooling air is introduced into the casing so that the aforesaid temperature of the casing is reduced to 120° C. or below
Data Source
AI summary
In a Roots vacuum pump, an inlet port is located at a position n spaced by a positive displacement angle of 120° in one direction from a center of each rotational axis relative to an imaginary line m connecting rotor axes. An outlet port is located at a position o opposite to the inlet port relative to the line. An air feed port is formed at a position t on a casing wall obtained by returning by 90° from the position o to the inlet port side so that two closed spaces are defined by adjacent rotor lobes and a casing inner wall at both port sides immediately after air suction respectively. The casing has discharge grooves in an area of the inner wall so as to communicate with the outlet port. The area ranges from the position o to a position u obtained by returning by 45° from the position o to the inlet port side. The discharge grooves have a total volume ranging from 2% to 5% of a volume of one of the closed spaces.