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Particulate Partial Flow Sampling System
Datasheet
Specifications
ISO 16183 & 1065
Using the BG-3 
Data Quality Assurance
BG-3 Software Explained
  Testing Applications
Future of BG-2
Background & History

History Made.

US EPA Has Approved BG3 as Alternative Method to CVS

The BG3 Partial Flow Dilution (PFD) technology has been in use since 2004 as a workhorse performing engine research and development to accurately sample exhaust particulate matter (PM) emissions over both steady state and transient test cycles.   On January 7, 2011, PFD was signed into law and is now included in the United States Federal Register as a legally recognized alternative method to CVS in 40 CFR part 1065 for engine certification. The Direct Final Rule (DFR) contains, among other things, the heretofore unprecedented allowance to use PFD for engine emissions particulate matter (PM) transient certification testing.

The Docket for the DFR shows that the basis for the US EPA decision was the correlation to FTP and NRTC CVS transient test cycle PM, as required by 40 CFR Part 1065.12 demonstrated by BG3.  A nearly 5-year program in cooperation with the US EPA resulted in a BG3 vs CVS multiple engine, two-lab correlation study (requiring the measurement of PM over a two-decade range in concentration levels)  was performed to prove BG3 complies as a suitable, fully compliant alternative method to CVS for certification of engines tested on 2007 and Tier IV transient test cycles.  This historical milestone opens the door to greater PM testing flexibility for all Heavy Duty (HD) as well as the Light Duty engine manufacturers requiring compliance to 40CFR Part 1065 test procedures.

Access to all information posted on the US EPA website follows.


•  Direct Final Rule (Snapshot of Relevant Section Page 68452, Part D): Learn More... 
•  Direct Final Rule (Complete Version), see Page 68452, Part D; See Footnote 14 to see reference to Sierra Learn More...
•  BG3 vs CVS multiple engine correlation study: Learn More... 
•  Docket detailing DFR decision: Learn More...

What Makes the BG3 Ideal?

Reasons Customers Choose BG3...

• Approximately 1/10th of CVS system cost of ownership

• Approximately 1/100th to 1/1000th  the annual energy usage versus a CVS, depending on CVS size and design

• Can be used on engines of any size and on any fuel in both engine and chassis test cells

• Patented partial flow dilution tunnel has ultra-low particulate loss and requires no cleaning with proper operation

• Integrity of internal flow systems and proprietary daily mirror calibration method yields excellent accuracy and repeatability of PM results over wide range of dilution ratios

• Easily portable from cell to cell to maximize flexibility and return on investment

• Satisfies all ISO 8178, ISO 16183, 40 CFR 1065 and CFR Part 89 requirements for PDF performance

• Ability to accurately measure PM either pre and post catalyst and/or DPF for research or DF testing

Product Overview

The Model BG3 Partial Flow Sampling System (PFSS) is a highly flexible engine particulate emissions sampling device protected by nine patents with several other pending.  BG3 is the recognized standard in the industry for partial flow sampling. BG3 is the most widely used technology of its type and boasts an installed base of hundreds of units globally.   It can be used for proportional sampling on transient test cycles with any fuel (diesel, gasoline, natural gas, etc.) and can be used on engines of any size in both engine and chassis test cells.  BG3 can be used equally effectively for steady state test cycle PM measurements.  Steady-state sampling times range from two to five minutes depending on the relative particulate emissions output of the engine and the size of the filter holder used.  Test cycles for any regulation can be easily designated, set up, and run.  BG3 satisfies all ISO 8178, ISO 16183 and 40CFR 1065 requirements for transient and steady-state equivalency, plus satisfies EPA requirements for non-road steady-state (CFR Part 89), supplemental 13-mode and ramp modal cycle testing.  The system can also be used as a diluter for particle sizing instrumentation and for gaseous emissions measurement systems, while simultaneously and accurately sampling particulate matter.

The fundamental description of BG3, per ISO8178-1 (5) is as a “partial flow dilution system with flow control and total sampling”, otherwise known as a ‘split, then dilute” methodology.   The operational difference between BG3 and CVS is that a CVS first dilutes the full flow of raw exhaust and then collects PM from a small fraction of that flow (dilute, then split), while the BG3 first proportionally extracts and then dilutes a small fraction of the raw exhaust and then collects PM on a gravimetric filter from that flow (split, then dilute).  The BG3 design premise is to provide equivalent results to CVS by maintaining proportionality of the raw exhaust sample mass flow relative to the exhaust mass flow rate of the engine.

The primary purpose of BG3 is to control the flow rate of a representative sample of exhaust during an engine test cycle where engine speed, load, airflow and fuel flow values exhibit high rates of change over very short time frames. The magnitude of engine inlet air mass flow excursions can approach 10:1 within less than two seconds. The challenge for any PFSS is to maintain constant proportional flow from an exhaust stream with a highly variable mass flow rate throughout a typical test cycle. In order to ensure that the total mass of particulate trapped at the filter is equivalent to that obtained by the use of a full flow CVS, the sample flow rate must be controlled in real-time to be proportional to the exhaust mass flow. Further, it is necessary to control this sample flow rate to ensure that the filter temperature does not exceed the regulatory defined limit while the dilution air temperature is maintained in the range required by the regulations.  

Near Zero-Loss Dilution Tunnel

The magic of BG3 is the patented dilution tunnel which eliminates the major achilles heel of any PFSS, the deposition of particulate on dilution chamber walls as the diluted exhaust sample is transferred to the filter from the raw exhaust stream. Ultra low particulate loss in the patented radial inflow partial flow dilution tunnel (Pictured) and a very short equilibration zone before the filter set the BG apart from all other PFSS.   Sierra’s patented dilution tunnel technology is a chamber under pres­sure. Conditioned dilution air permeates from the outside of the chamber in through the walls of a sintered metal tube carrying the diluted sample, creating a hydrocarbon-free air barrier. This eliminates the effect of the dilution system’s “history” on the test sample.

BG3 is an integrated product that incorporates two flow devices supplying and extracting gas from used in the dilution tunnel design.  The mass flow of raw exhaust sampled at the probe is the difference between the flow rates of the dilution and total mass flow meters. This sample flow is calculated as the difference between the total and dilute flow.

Background

In 1991, Caterpillar Inc. and Sierra Instruments formed a joint agreement to commercialize several Caterpillar patents to produce the Model BG-1 Partial Flow Sampling System (PFSS). Sierra followed this effort up with the Model BG-2 PFSS which features advanced software. 

The flagship Sierra BG3 transient PFSS was developed in 2003 in response to pending requirements for transient cycle development and certification of non-road engines.  Due to their expanded power output levels, higher mass flow rates and elevated test cycle exhaust heat content, off-road engines present a unique set of challenges to the continued use of CVS systems.  Learn more...