Radial Compressor Impeller and Diffuser Design for High Pressure Ratio
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Solution Overview
Problem
Current turbocharger systems for diesel engines have efficiency limitations, especially at high pressure ratios, leading to impaired engine performance and increased fuel consumption, due to the constraints of existing compressor designs and materials.
Innovation Solution
A radial compressor with an impeller having a blade angle of at least 40° and a diffuser with a low solidity airfoil design, featuring a diameter ratio between 0.50-0.62 and blade pitch ratio of 0.7-1.5, which allows for higher isentropic efficiency without reducing the stable working range, enabling a two-stage turbo system with reduced peripheral velocity and material costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If the blade angle βb2 of the compressor is increased to improve pressure ratio, then the pressure build-up improves, but the peripheral velocity and tensions in the impeller increase
Solution Approach 1:
The patent changes the diameter ratio parameter Di/Du from the conventional range of 0.63-0.70 to a reduced range of 0.50-0.62. This parameter change allows the compressor to achieve high pressure ratios (above 3:1) while operating at lower peripheral velocities, thereby reducing impeller tensions and allowing the use of less expensive materials like cast aluminum instead of forged aluminum or titanium.
2Stress or pressure
If the blade angle βb2 is increased to achieve higher pressure ratio, then the pressure build-up improves, but more expensive materials with higher strength properties are required
Solution Approach 1:
The patent applies parameter changes to the diameter ratio Di/Du, reducing it to 0.50-0.62, which enables high pressure ratios to be achieved at lower peripheral velocities. This reduces the mechanical stresses on the impeller, allowing the use of cost-effective cast aluminum materials instead of expensive forged aluminum or titanium materials.
3Loss of energy
If the diffuser is provided with aerodynamically configured blades (LSA diffuser) to improve efficiency at high pressure ratios, then the efficiency improves, but the device complexity increases
Solution Approach 1:
The patent changes the solidity ratio parameter of the diffuser blades, defining a low solidity airfoil (LSA) diffuser where the ratio of blade length to pitch is within the range 0.7-1.5. This parameter change optimizes the diffuser structure to achieve high compressor efficiency at pressure ratios above 3:1 while maintaining a relatively simple and cost-effective design.
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
This configuration achieves higher isentropic efficiency at high pressure ratios, reducing specific fuel consumption and allowing for a more effective supercharging system with improved transient response and reduced material requirements.
Implementation Method 1
Upon rotation of the shaft, gas, for example air, is sucked into the impeller, whereupon the static pressure level and flow velocity increase
Implementation Method 2
During passage through the diffuser, some of the velocity energy of the gas is converted into a further static pressure increase
Data Source
AI summary
A turbocharger unit for an internal combustion engine having at least one exhaust line for the evacuation of exhaust gases from the combustion chamber of the engine and at least one inlet line for the supply of air to the combustion chamber is provided. The turbocharger unit includes a turbine which interacts with a compressor in order to extract energy from the exhaust-gas flow of the engine and pressurize the inlet air of the engine. The compressor is of the radial type and is provided with an impeller having backswept blades in which the blade angle between an imaginary extension of the center line of the blade between root section and tip section in the direction of the outlet tangent and a line connecting the center axis of the impeller to the outer tip of the blade is at least about 40 degrees. The ratio between the inlet diameter of the impeller and its outlet diameter lies within the range 0.50-0.62. The compressor diffuser is provided with blades, the length of which has a ratio to the distance between them, along the periphery in the blade inlet, within the range 0.7-1.5.