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Improvement to Compressor Engine Reliability through Retrofit Micro-Pilot Ignition System
Project Number

The goal of this project is to develop a highly reliable micro-pilot ignition system that can be retrofitted to older, 2-stroke, natural gas compressor engines now used throughout the nation's pipeline network, to enhance operational integrity, increase fuel efficiency and reduce emissions from these machines.


Colorado State University (CSU) – project management, design and testing
Woodward Governor Company – system components and commercialization assistance

Fort Collins, CO
Blanco, NM 
Window Rock, AZ


In total, the U.S. pipeline industry has approximately 8,000 reciprocating engines installed for natural gas compression. The overwhelming majority of these engines are low compression ratio, slow speed, large bore, low brake-mean-effective-pressure, 2-stroke, gas engines. Almost all of these engines are between 20 and 50 years old, and they represent a critical part of the natural gas pipeline infrastructure. To replace any significant fraction of this asset base would cost billions of dollars. Spark ignition systems, which are a feature of these older engines, can be unreliable, leading to compressor downtime. A micro-pilot ignition system would operate similarly to the injectors used in a diesel engine, by injecting a small amount of pilot fuel that auto-ignites, in turn providing the ignition source for the natural gas fueling the engine. If such a system could be designed to be easily retrofitted to the existing stock of compressor engines, their reliability could be improved.


This technology, once fully developed and commercialized, could provide a dramatic impact on the capacity, operating reliability and/or emissions of the nation's existing natural gas compression infrastructure. By allowing older slow speed, 2-stroke reciprocating compressor systems to operate over a wider range, the micro-pilot ignition system offers the potential for reduced fuel consumption for a given throughput of the compressor. It can also allow the engine to run at much leaner air to fuel ratios while still preventing misfire, permitting the system to be optimized to reduce emissions where required. Overall the increase in system operating range and ignition reliability will reduce maintenance associated with the machines and their current spark plug configuration. The increased operational reliability of the compression infrastructure is a key factor in maintaining the reliability of natural gas delivery to the nation's consumers.

Accomplishments (most recent listed first)
  • Proved the concept by designing a common rail micro-pilot ignition system and demonstrating it in the laboratory,
  • Optimized the laboratory-based system over a range of conditions, and
  • Finalized pre-field test arrangements with commercialization partners.
  • Completed field testing installation and operational plan.
  • Successfully conducted full scale testing of micro-pilot only ignition (spark ignition disengaged) system on an operating pipeline compressor engine.

In Phase I of the program, the research team designed a common rail micro-pilot ignition system by combining Woodward controls and electronics with commercially available Delphi injectors modified to allow mounting in the test engine. The entire system is controlled with existing Woodward electronics. The system was retrofitted to a Cooper Bessemer GMV-4 engine and tested in the laboratory.

In Phase II of the program, the system was refined, optimized and further developed for field-testing. The optimization included evaluation of the performance effects of different pilot fuels, comparisons of combustion stability, fuel consumption, nitrogen oxides (NOX) production, and hazardous air pollutants (HAPs) production. The results were used to determine fuel selection, compression ratio, and other overall system parameters. Based on these results, new product specifications were developed to guide design changes and revisions (e.g., the standard, 5-hole automotive injector nozzles proved to be non-optimal and new, 3-hole nozzles were manufactured). Phase II ended with the preparation of a prototype design for field-testing.

Phase III of the project consisted primarily of the undertaking of development and carrying out field testing of the system. Three vendors have been selected to provide commercialization expertise and to participate in the field-testing of the system (Hoerbiger Corp. of America, Enginuity Inc., and Digicon Inc.). Two distinct field tests were conducted at sites in Window Rock, Arizona and Blanco, New Mexico. The field test team designed the testing protocol, installed the system as a retrofit on compressor engines at both field sites, conducted the field demonstration, and collected performance and emissions data. At the El Paso station at Window Rock the compressor was successfully operated using solely micro-pilot diesel ignition (spark ignition was disengaged) on a Worthington SUTC-10. This field demonstration successfully displayed the capability of the system to sustain operation of a large pipeline compressor engine. Data showed that the technique permitted increased operating range for the system by allowing leaner operation without misfire. Results also indicated the potential to tune operation of the system using micro-pilot ignition for reduced fuel consumption or reduced emissions. The unit remains at the site for extended duration testing. Testing at Blanco, New Mexico had limited success due to low atmospheric oxygen levels at the extreme altitude of the test site.

Micro-pilot Ignition system installed on Worthington SUTC-10 at El Paso's Window Rock, AZ Compressor Station
Micro-pilot Ignition system installed on Worthington SUTC-10 at El Paso's Window Rock, AZ Compressor Station


Current Status

and Remaining Tasks:
The work under this program has been successfully completed. The field test unit at Window Rock, Arizona is to continue for durability testing and the project cost share partner, Woodward Governor, has expressed interest in continued development of the system and future potential commercialization.

Project Start
Project End
DOE Contribution


Performer Contribution


Contact Information

NETL – Richard Baker ( or 304-285-4714)
CSU (EECL-Engines and Energy Conversion Laboratory) – Ted Bestor ( or 970-491-4781)