Technical Description
General Specification
Background

The Model BG-3 consists of 5 main components:

1. Proprietary Radial Inflow Dilution Tunnel technology.
2. A dilution air flow meter.
3. A total air flow meter.
4. Propriatary T-DAC™ proportional controller and actuator.
5. Software.

The Model BG-3 is a Transient Partial Flow Sampling System (TPFSS) developed to provide an alternative to full flow CVS systems for the measurement of Particulate Matter (PM). Similar to CVS, the Model BG-3 is designed primarily to satisfy requirements for gravimetric filter measurement of PM, using filter holders that comply with either current or 2007 engine emissions standards.

The primary purpose of the Model BG-3 is to control the flow rate of a representative sample of exhaust during an engine 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. The combination of the above constraints can result in the use of high dilution ratios, exacerbating the requirements for flow accuracy.

The Model BG-3 is an integrated product that incorporates two flow controllers supplying and extracting gas from proprietary Radial Inflow technology 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. The Model BG-3 relies on patented T-DAC™ (transient dilution airflow control) technology to address the high dilution rates necessitated by temperature constraints. The dilution and total mass flow measurement devices must achieve accuracy levels that require advanced measurement techniques. The patented T-DAC technology used in the Model BG-3 assures the speed of operation of the dilute mass flow controller is fast enough to ensure that the sample flow is correctly correlated with the engine exhaust mass flow.