Centrifugal Compressor Diffuser Throat Positioning for High Flow Efficiency

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Centrifugal compressors experience efficiency degradation due to excessive static pressure and pressure loss at high flow rates, as the static pressure field leads to dynamic pressure increases near the outlet of the scroll flow passage, causing inefficiency.

Innovation Solution

A centrifugal compressor design with a diffuser flow passage configuration where the average distance from the rotational axis to the throat portion is greater in the vicinity of the scroll-end part, expanding the flow passage area and reducing pressure loss, and an outer flow passage portion with a decreasing height in the radial direction to minimize stall region expansion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the diffuser flow passage is configured with a conventional uniform throat portion position, then the compressor operates stably at design flow rates, but efficiency degrades at high flow rates due to excessive dynamic pressure and pressure loss

Engineering Contradiction:

Improveoperational efficiency at high flow rateVSAvoidpressure loss in diffuser flow passage

Core Design Contradiction:

ProductivityVSLoss of energy

Solution Approach 1:

The patent applies local quality by varying the radial position of the throat portion along the circumferential direction of the diffuser flow passage. Specifically, the throat portion is positioned at different radial distances from the rotational axis at different angular positions, creating locally optimized flow conditions. This allows the diffuser to adapt to varying flow conditions at different circumferential locations, reducing pressure loss and preventing stall region expansion at high flow rates while maintaining stable operation at design conditions.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent implements parameter changes by modifying the geometric parameters of the diffuser flow passage, specifically the radial position of the throat portion. By changing the radial coordinate of the throat portion as a function of the angular position, the patent optimizes the flow passage area distribution. This parameter variation allows the compressor to maintain efficient operation across a wider range of flow rates, particularly improving high-flow performance by reducing excessive dynamic pressure effects.

Inventive Principle:

Principle #35Parameter changes

2Loss of energy

If the flow passage area is increased to reduce pressure loss, then efficiency improves at high flow rates, but the stall region may expand and compromise stability

Engineering Contradiction:

Improvepressure loss reductionVSAvoidflow stability and stall region control

Core Design Contradiction:

Loss of energyVSStability of the object's composition

Solution Approach 1:

The patent uses local quality to differently configure the throat portion position in various circumferential regions of the diffuser. By positioning the throat portion at optimal radial locations in different angular sectors, the patent locally controls the flow passage area to prevent stall region expansion while still reducing pressure loss in critical high-flow regions. This localized optimization balances stability improvement with efficiency enhancement.

Inventive Principle:

Principle #3Local quality

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 suppresses efficiency degradation on the high flow rate side by reducing pressure loss and preventing the expansion of the stall region, thereby enhancing the operational efficiency of the centrifugal compressor.

Implementation Method 1

a centrifugal compressor whose efficiency degradation on the high flow rate side is suppressed

Methodology Applied

Scientific EffectCentrifugal force: Centrifugal Force

Implementation Method 2

the static pressure on the outlet side of the scroll flow passage tends to decrease. As a result of researches by the present inventors, it became clear that due to the influence of the static pressure field, a dynamic pressure locally becomes excessive

Methodology Applied

Scientific EffectPressure gradient: Pressure Gradient

Data Source

PatentEP3712441B1Centrifugal compressor and turbo charger equipped with said centrifugal compressor

Publication Date: 2023.07.12 MITSUBISHI HEAVY IND ENGINE & TURBOCHARGER LTD

Figure 1
Figure 2
Figure 3

AI summary

A centrifugal compressor includes a housing which includes a scroll portion with a spiral scroll flow passage being formed on an outer peripheral side of an impeller, and a diffuser portion with a diffuser flow passage being formed, the diffuser flow passage extending along the scroll flow passage on a radially inner side of the scroll flow passage and communicating with the scroll flow passage. The diffuser flow passage includes an inner flow passage portion extending from an inlet portion of the diffuser flow passage to a throat portion with a flow passage height thereof decreasing, and an outer flow passage portion extending from the throat portion to an outlet portion of the diffuser flow passage. An average distance from the rotational axis to the throat portion within a range where an angular range in a circumferential direction with reference to a tongue section of the scroll portion is between 240° and 300° is greater than an average distance from the rotational axis to the throat portion outside the range where the angular range is between 240° and 300°.