Advanced Compressor Engine Controls to Enhance Operation,

Reliability, & Integrity

Project DE-FC26-03NT41859Project DE-FC26-03NT41859

Gary D. BournGary D. Bourn

Southwest Research InstituteSouthwest Research Institute

12-16-200312-16-2003

Presentation Outline

Executive SummaryExecutive Summary Technical OverviewTechnical Overview Project ScheduleProject Schedule

Executive Summary The gas transmission industry operates >3,000 integral The gas transmission industry operates >3,000 integral

engine compressors with a median age of 40 years and a engine compressors with a median age of 40 years and a median size of 2000 horsepower. These engines pump at median size of 2000 horsepower. These engines pump at least half of the 23 TCF of natural gas presently consumed.least half of the 23 TCF of natural gas presently consumed.

The natural gas consumption is projected to exceed 30 TCF The natural gas consumption is projected to exceed 30 TCF by 2020. While new pipelines and compressors will be by 2020. While new pipelines and compressors will be installed to increase capacity, the reliability of the existing installed to increase capacity, the reliability of the existing infrastructure is critical to meet the demand.infrastructure is critical to meet the demand.

Wholesale replacement of existing integral compressors is Wholesale replacement of existing integral compressors is not economically feasible. Therefore, the integrity, capacity, not economically feasible. Therefore, the integrity, capacity, emissions, and efficiency of existing units must improve to emissions, and efficiency of existing units must improve to help meet the project growth. help meet the project growth.

Executive Summary (cont.) New technologies are required to improve the older integral New technologies are required to improve the older integral

compressors, and these include combustion, ignition, compressors, and these include combustion, ignition, breathing, and controls. breathing, and controls.

Advanced control technologies are necessary for these older Advanced control technologies are necessary for these older integral engines to meet impending emissions regulations, integral engines to meet impending emissions regulations, and achieve enhanced operation, integrity, and capacity for and achieve enhanced operation, integrity, and capacity for continued use in the U.S. natural gas transmission network.continued use in the U.S. natural gas transmission network.

The objective of this project is to develop, evaluate, and The objective of this project is to develop, evaluate, and demonstrate advanced engine control technologies and demonstrate advanced engine control technologies and hardware, specifically closed-loop NOhardware, specifically closed-loop NOXX emissions control, emissions control,

on a two-stroke integral gas compressor engine.on a two-stroke integral gas compressor engine.

Technical Overview

Current Engine Control StatusCurrent Engine Control Status Proposed Advanced Controls TechnologiesProposed Advanced Controls Technologies Project Co-FunderProject Co-Funder Test BedTest Bed Project Work Breakdown StructureProject Work Breakdown Structure

Example Two-Stroke Integral Compressor Engine

Typical Control Strategy for Integral Compressor Engines Fuel Header Pressure is modulated to maintain engine Fuel Header Pressure is modulated to maintain engine

speed - governorspeed - governor Controller adjusts Wastegate to modulate Air Manifold Controller adjusts Wastegate to modulate Air Manifold

Pressure based on derived relationship - “air/fuel ratio”Pressure based on derived relationship - “air/fuel ratio” Linear relationship of Air Manifold Pressure as a function Fuel Linear relationship of Air Manifold Pressure as a function Fuel

Header Pressure is derivedHeader Pressure is derived

Individual Cylinder Balancing usually done manually.Individual Cylinder Balancing usually done manually. Ignition Controller does not always communicate with Ignition Controller does not always communicate with

“Air/Fuel Ratio” Controller“Air/Fuel Ratio” Controller

Typical Control Strategy for Integral Compressor Engines

Two-Stroke Integral Engine Issues Open Chamber configurations w/ mechanical fuel admissions Open Chamber configurations w/ mechanical fuel admissions

exhibit relatively high cylinder-to-cylinder & cycle-to-cycle exhibit relatively high cylinder-to-cylinder & cycle-to-cycle deviation in firing pressuredeviation in firing pressure These deviations contribute to: higher NOThese deviations contribute to: higher NOXX emissions, reduced fuel emissions, reduced fuel

efficiency, reduced operating envelope, as well as increased stress peaks efficiency, reduced operating envelope, as well as increased stress peaks on the crankshafton the crankshaft

Combustion instability often blamed on inconsistent fuel/air mixing - Combustion instability often blamed on inconsistent fuel/air mixing - improved w/ pre-combustion chambers & enhanced mixing fuel injectorsimproved w/ pre-combustion chambers & enhanced mixing fuel injectors

Data suggests imbalance between cylinders in airflow (trapped air mass), Data suggests imbalance between cylinders in airflow (trapped air mass), which would create air/fuel ratio varianceswhich would create air/fuel ratio variances Two-Stroke breathing highly dependent on instantaneous manifold dynamics Two-Stroke breathing highly dependent on instantaneous manifold dynamics

& port open duration& port open duration

Individual cylinder control is necessary to improve engine Individual cylinder control is necessary to improve engine performanceperformance

Variation in Compression & Combustion Pressure

Average Cylinder Pressure04_16_2003_09_40_05_300

0

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90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 270

Crank Angle Degree

Cyl

ind

er P

ress

ure

(p

sia)

Cyl #2 Cyl #3 Cyl #4 Cyl #5 Cyl #6

Clark HBA-6TTGP Station 823

Advantages of Individual Cylinder Control

A/F Imbalance between cylinders leads to reduced Knock & Lean Limitmargins, lower overall efficiency, & higher overall NOx emissions. OverallNOx emissions skews toward rich cylinders due to non-linear relationship with Equivalence Ratio.

A/F Balance between cylinders gives increased Knock & Lean Limit margins, allowing more timing advance & leaner overall operation. This improves the Efficiency-NOx tradeoff.

Current Advanced Control Technologies Advantages of controlling to fuel/air equivalence ratio are Advantages of controlling to fuel/air equivalence ratio are

being realizedbeing realized Current approaches involve calculated equivalence ratio from in-Current approaches involve calculated equivalence ratio from in-

direct measurements & mapping of NOdirect measurements & mapping of NOXX

Parametric Emissions Monitoring (PEM)Parametric Emissions Monitoring (PEM) Advanced versions incorporate continuous cylinder pressure Advanced versions incorporate continuous cylinder pressure

measurement & tuned models to predict NOmeasurement & tuned models to predict NOXX

Electronic fuel injectionElectronic fuel injection Offer increased control flexibility & improved in-cylinder mixing Offer increased control flexibility & improved in-cylinder mixing

of air/fuel chargeof air/fuel charge Coupled w/ calculated equivalence ratio & continuous cylinder Coupled w/ calculated equivalence ratio & continuous cylinder

pressure measurementpressure measurement

Proposed Advanced Control Technologies Utilize NGK-Locke sensor to directly measure exhaust NOUtilize NGK-Locke sensor to directly measure exhaust NOXX & &

equivalence ratio (similar to automotive controls)equivalence ratio (similar to automotive controls) More accurate real-time control can be achievedMore accurate real-time control can be achieved Reduced engine mapping required to tune control algorithm for specific Reduced engine mapping required to tune control algorithm for specific

engine modelengine model Generalizes control algorithm for easier application to different engine Generalizes control algorithm for easier application to different engine

models models

NGK-Locke sensor provides both NONGK-Locke sensor provides both NOXX & O & O22 concentration in concentration in

exhaustexhaust OO22 channel can be calibrated to Equivalence Ratio (like UEGO) channel can be calibrated to Equivalence Ratio (like UEGO)

Has been demonstrated in both spark-ignition & diesel enginesHas been demonstrated in both spark-ignition & diesel engines SwRI has demonstrated sensor performance in two-stroke integral SwRI has demonstrated sensor performance in two-stroke integral

compressor enginescompressor engines

NGK-Locke NOX / O2 Sensor Utilizes thick film ZrOUtilizes thick film ZrO22

5th generation type5th generation type Integrated control electronics & Integrated control electronics &

temperature compensationtemperature compensation 14.0 +/-0.5V power 14.0 +/-0.5V power

requirementrequirement Linear in OLinear in O22 and NO and NOXX

concentrations => 0-5v outputconcentrations => 0-5v output < 30 msec response time< 30 msec response time NONOXX measurement accuracy is measurement accuracy is

±5ppm of reading±5ppm of reading

Calibration on GMVH Engine - NOX Concentration

y = 445.49x - 153.81

y = 426.32x - 131.68

R2 = 0.9998

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Voltage

NO

x C

on

ce

ntr

ati

on

(p

pm

)

Original NGK Calib. SwRI NG Engine Calib. Linear (Original NGK Calib.) Linear (SwRI NG Engine Calib.)

Calibration on GMVH Engine - Equivalence Ratio

y = -0.3197x + 1.7717

y = -0.4002x + 1.8956

R2 = 0.9992

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1.2

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Voltage

Eq

uiv

ale

nc

e R

ati

o (

sta

ck

)

Original NGK Calib. SwRI NG Engine Calib. Linear (Original NGK Calib.) Linear (SwRI NG Engine Calib.)

Based on assumed stoich A/F for NGK data

Proposed Advanced Control Technologies (cont.) Advanced control will take global NOAdvanced control will take global NOXX concentration input & concentration input &

control engine to maintain this specific level w/ optimized control engine to maintain this specific level w/ optimized efficiency on a cylinder-to-cylinder basisefficiency on a cylinder-to-cylinder basis

Most common engine configuration w/ mechanical fuel Most common engine configuration w/ mechanical fuel admission will be targetedadmission will be targeted Global Fuel Header Pressure still used for speed governing.Global Fuel Header Pressure still used for speed governing. Equivalence Ratio input used to modulate Wastegate.Equivalence Ratio input used to modulate Wastegate. Spark Timing set for optimal efficiency & trimmed globally (if Spark Timing set for optimal efficiency & trimmed globally (if

necessary) to maintain NOnecessary) to maintain NOXX..

Cylinder pressure input provides for trimming/biasing individual cylinder Cylinder pressure input provides for trimming/biasing individual cylinder Spark Timing & Fuel Flow for balancing of NOSpark Timing & Fuel Flow for balancing of NOXX. This feature will . This feature will

increase efficiency for a given exhaust NOincrease efficiency for a given exhaust NOXX, increase operating range, & , increase operating range, &

improve mechanical integrity.improve mechanical integrity.

Advanced Control Strategy for Integral Compressor Engines

Not Shown: Individual Cylinder Firing Pressure Sensors

Project Co-Funder

Cooper Energy Services (CES) is not only Cooper Energy Services (CES) is not only providing co-funding to this project, but making providing co-funding to this project, but making available their research engine and expertise of available their research engine and expertise of integral compressor engines as an OEM.integral compressor engines as an OEM. Cooper-Bessemer engines make up a large percentage Cooper-Bessemer engines make up a large percentage

of the integral compressor engine fleetof the integral compressor engine fleet CES previously contracted with SwRI to setup CES previously contracted with SwRI to setup

their GMVH-6 laboratory engine at SwRI their GMVH-6 laboratory engine at SwRI facilities. facilities.

Engine Test Facility

330 rpm, 1350 bhp gas compressor engine330 rpm, 1350 bhp gas compressor engine Engine highly instrumented for R&D technologiesEngine highly instrumented for R&D technologies

Engine/System Controls Rapid Prototype Electronic Rapid Prototype Electronic

Control System (RPECS)Control System (RPECS) Full-authority controllerFull-authority controller SwRI developedSwRI developed Commercially availableCommercially available Rapid algorithm developmentRapid algorithm development SwRI interfaces with well-SwRI interfaces with well-

known control system known control system manufacturers to assist engine manufacturers to assist engine manufacturers with technology manufacturers with technology transfertransfer

Engine/System Controls Algorithm & Software DevelopmentAlgorithm & Software Development

Classic & Modern Control Classic & Modern Control AlgorithmsAlgorithms

Real-time Model-based ControlReal-time Model-based Control Diagnostics for Service & OBDDiagnostics for Service & OBD Adaptive Learn AlgorithmsAdaptive Learn Algorithms

Advanced Signal ProcessingAdvanced Signal Processing Source Code Development Source Code Development

in Assembly, C, and Graphical in Assembly, C, and Graphical Environments Such As Environments Such As Matlab/SimulinkMatlab/Simulink

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Time (secs)

Kn

ock V

olt

s,

Kn

ock T

ime,

Kn

ock B

ias

Knock Bias to Injectoror Ignition Module

Knock Min Timer

Knock Threshold

Knock Voltage

Project WBS

1.0 System Configuration1.0 System Configuration

2.0 Baseline Mapping2.0 Baseline Mapping

3.0 Algorithm Development3.0 Algorithm Development

4.0 Closed-Loop Control Evaluation4.0 Closed-Loop Control Evaluation

5.0 Data Analysis5.0 Data Analysis

6.0 Algorithm Schematic Development6.0 Algorithm Schematic Development

Project Schedule2003 2004

Task Description Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept.

0 Program Management 3 4

Research Management Plan 1

1 Technology Status Assessment 2

2 System Configuration

2.1 Engine Configuration

2.2 Controls Configuration

3 Control Algorithm Development

3.1 Initial Algorithm Development

3.2 Final Algorithm Development

4 Baseline Mapping

5 Closed-Loop Control Evaluation

6 Data Analysis

6.1 Baseline Data Analysis

6.2 Engine Modeling

6.3 Algorithm Test Data Analysis

7 Algorithm Schematic Development

Deliverables1 Research Management Plan Report2 Technology Status Assessment Report3 Semi-Annual Progress Report4 Final Report

Conclusion

The SwRI/CES team appreciates the support of The SwRI/CES team appreciates the support of DOE, & looks forward to the opportunity to DOE, & looks forward to the opportunity to advance the state of the art in integral compressor advance the state of the art in integral compressor engine controlsengine controls

Our goal is to develop technology that can be Our goal is to develop technology that can be realistically & cost-effectively implemented by the realistically & cost-effectively implemented by the gas transmission industry to help meet the gas transmission industry to help meet the growing demand for natural gas, while meeting growing demand for natural gas, while meeting current & future emissions regulationscurrent & future emissions regulations