Reductant Insertion Accuracy via Calibration Lookup Table

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Solution Overview

Problem

Existing exhaust aftertreatment systems for internal combustion engines face challenges in achieving accurate insertion of reductants into SCR systems due to part-to-part variations in pumps and injectors, leading to inconsistencies in NOx reduction and increased manufacturing and maintenance costs.

Innovation Solution

A system and method for calibrating a pump with a calibration injector to determine calibration values, adjusting the insertion time of the reductant injector based on pump operating parameters and predetermined calibration values to achieve a desired flow rate, ensuring accurate reductant insertion into the SCR system.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If part-to-part variations in pumps and injectors are not addressed, then manufacturing and maintenance costs increase, but reductant insertion accuracy deteriorates

Engineering Contradiction:

Improvereductant insertion accuracyVSAvoidcalibration system complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The system performs preliminary calibration of the pump-injector combination before actual operation. Calibration values are determined in advance by measuring the actual flow rates at various pump insertion times and storing these values in a lookup table. During operation, the controller simply retrieves the pre-determined calibration values based on the desired flow rate, eliminating the need for real-time complex calculations or adjustments.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

A calibration lookup table serves as an intermediary between the pump-injector assembly and the control system. This table stores pre-determined calibration values that map desired flow rates to actual pump insertion times. The intermediary translates the desired flow rate into the specific insertion time needed, compensating for part-to-part variations without requiring complex real-time control algorithms.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Manufacturing precision

If tight tolerance control is implemented on pumps and injectors, then reductant insertion accuracy improves, but manufacturing costs increase

Engineering Contradiction:

Improvereductant insertion accuracyVSAvoidmanufacturing cost

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The system changes the approach from controlling physical dimensions (tight tolerances on pump and injector parts) to controlling operational parameters (pump insertion time). By measuring and storing the relationship between insertion time and flow rate for each pump-injector combination, the system achieves accurate flow rate control without requiring tight mechanical tolerances, thereby reducing manufacturing costs.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

Each pump-injector assembly calibrates itself during a brief calibration procedure. The system automatically determines the calibration values by measuring the actual flow rates at different insertion times and storing these values in the lookup table. This self-calibration capability eliminates the need for expensive precision manufacturing while ensuring each assembly operates at its optimal accuracy.

Inventive Principle:

Principle #25Self-service

3Measurement precision

If calibration values are determined for each pump-injector combination, then flow rate accuracy improves, but system setup time increases

Engineering Contradiction:

Improveflow rate accuracyVSAvoidcalibration setup time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The calibration process uses a practical number of measurement points that provides sufficient accuracy without being excessively time-consuming. The system determines calibration values at key flow rate points and uses these to interpolate or select appropriate insertion times during operation. This partial calibration approach achieves the required flow rate accuracy while minimizing the time investment.

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS11306639B2Systems and methods for increasing reductant insertion accuracy

Publication Date: 2022.04.19 CUMMINS EMISSION SOLUTIONS INC

AI summary

An aftertreatment system comprises a SCR system, a reductant injector operatively coupled to the SCR system, and a reductant insertion assembly operatively coupled to the reductant injector. The reductant insertion assembly comprises a pump configured to pump the reductant through the reductant injector. A controller is operatively coupled to the reductant insertion assembly and configured to receive predetermined calibration values of the pump corresponding to delivery of a reductant by the pump through a calibration injector. The controller determines a desired flow rate value of the reductant into the SCR system. The controller determines an insertion time of the reductant injector for delivering the reductant through the reductant injector based on the desired flow rate value, a pump operating parameter value of the pump and the predetermined calibration values, and activates the reductant injector for the insertion time.