5ae8788fd7
Source-tree mirror of EVOLV.wiki.git refactor (27a42ee on wiki.git): - 7 master pages rewritten with clean design (Home, Architecture, Topology-Patterns, Topic-Conventions, Telemetry, Getting-Started, Glossary). Tables and Mermaid for visuals, gitea alert callouts for warnings, shields badges for metadata only. No emoji as decoration. - Archive.md becomes a removal-changelog pointing readers to git history and to the successor pages. - _Sidebar.md updated to navigate the new flat-name layout. - Concept / finding / manual pages: uniform mini-header (badges + "reference page" callout) added without rewriting domain content. - Every internal link now uses the flat naming that resolves on the live gitea wiki (Concept-ASM-Models, Finding-BEP-..., etc.). On wiki.git: 29 Archive-* pages hard-deleted (the git history preserves them; Archive.md documents the removal). Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
48 lines
2.3 KiB
Markdown
48 lines
2.3 KiB
Markdown
---
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title: NCog Behavior and Limitations
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created: 2026-04-07
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updated: 2026-04-07
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status: evolving
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tags: [rotatingMachine, NCog, BEP, efficiency]
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sources: [nodes/rotatingMachine/src/specificClass.js]
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---
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> [!NOTE]
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> Reference page. Maintained for context; not regenerated by code. See [Home](Home) for current top-level navigation.
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# NCog — Normalized Center of Gravity
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## What It Is
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NCog is a 0-1 value indicating where on its flow range a pump operates most efficiently. Computed per tick from the current pressure slice of the 3D pump curve.
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```
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BEP_flow = minFlow + (maxFlow - minFlow) * NCog
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```
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## How It's Computed
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1. Pressure sensors update → `getMeasuredPressure()` computes differential
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2. `fDimension` locks the 2D slice at current system pressure
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3. `calcCog()` computes Q/P (specific flow) across the curve
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4. Peak Q/P index → `NCog = (flowAtPeak - flowMin) / (flowMax - flowMin)`
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## When NCog is Meaningful
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NCog requires **differential pressure** (upstream + downstream). With only one pressure sensor, fDimension is the raw sensor value (too high), producing a monotonic Q/P curve and NCog = 0.
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| Condition | NCog for H05K | NCog for C5 |
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|-----------|--------------|-------------|
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| ΔP = 400 mbar | 0.333 | 0.355 |
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| ΔP = 1000 mbar | 0.000 | 0.000 |
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| ΔP = 1500 mbar | 0.135 | 0.000 |
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| ΔP = 2000 mbar | 0.351 | 0.000 |
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## Why NCog = 0 Happens
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For variable-speed centrifugal pumps, Q/P is monotonically decreasing when the affinity laws dominate (P ∝ Q³). At certain pressure levels, the spline interpolation preserves this monotonicity and the peak is always at index 0 (minimum flow).
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## How the machineGroupControl Uses NCog
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The BEP-Gravitation algorithm seeds each pump at its BEP flow, then redistributes using slope-based weights + marginal-cost refinement. Even when NCog = 0, the slope redistribution produces near-optimal results because it uses actual power evaluations.
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> [!warning] Disproven: NCog as proportional weight
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> Using NCog directly as a flow-distribution weight (`flow = NCog/totalNCog * Qd`) is wrong. It starves pumps with NCog = 0 and overloads high-NCog pumps. See `calcBestCombination` in machineGroupControl.
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