The Cambustion DPG: Diesel Particulate Filter testing without an engine dynamometer.
Conventional Testing
Traditionally DPFs have been tested in a variety of ways, combining cold flow tests with measurements of backpressure made using an engine and dynamometer to produce soot. The former use artifical soot, with markedly different characteristics to engine generated soot. While widely adopted, engine dynamometer testing requires expensive facilities and staff, and extreme care must be taken to ensure good repeatability and reproducability. The interaction between engine and DPF means that evaluation of different DPFs on a given engine platform may be extremely complex.
The Cambustion DPG Solution
Soot Loading
The DPG uses controlled combustion of Diesel fuel to produce a soot laden airflow. Tight control of the primary air/fuel ratio ensures an unvarying soot production rate, despite changes in the test conditions. Secondary air (not directly involved in combustion) prevents the flame contacting the walls of the burner housing, resulting in very stable combustion.
The flow of warm, particle laden gas may be blended with another (tertiary) flow, whose temperature and flow rate may be varied without affecting the burner. This allows a wide range of DPF inlet temperatures and flows to be generated without influencing the burner conditions. Flow rates and temperatures are typically representative of light duty diesel engines with soot rates in the range 2 - 20 g/hr
The gas is sucked through the DPF using vacuum blowers located downstream of the DPF. This approach decouples the burner conditions (pressure etc) from the changes caused as the DPF fills with soot. Such an interaction may be a problem when trying to devise tests using engine based systems, where soot rate can depend on DPF fill state. The system incorporates an air-to-air heat exchanger to protect the vacuum blowers from high temperature.
Software tools are available to correct the backpressure measurements from the DPG for equivalence with blown bench tests.
Regeneration
Control over the DPF inlet conditions allows the DPG to regenerate filters. This can provide a simple means of de-greening filters, regeneration after soot loading tests, or allow more complicated studies such as Maximum Soot Load tests, where the DPG's improved reproducibility and repeatability offer substantial advantages.
Cold Flow Tests
The DPG may also make cold flow tests, and results may be corrected to any set of reference conditions.
Advantages
The DPG has lower infrastructure and operation costs than an engine dynamometer.
Further, the computer control allows the system to operate unmanned for substantial portions of the test- only requiring operator input to weigh or change DPFs.
The DPG allows customers to study the behaviour of a filter without the corresponding difficulties associated with engine tests, avoiding issues such as passive regeneration due to NOx and engine / DPF interactions due to backpressure.
The DPG allows the DPF to be preheated to the loading temperature and flow conditions, while not producing any soot. The burner settings are then automatically switched to a soot producing mode while maintaining the same DPF inlet conditions. This allows the pore filling stage of filtration to be studied in unprecedented detail
Applications
For a list of Application Notes which offer detailed guidance on common uses of the DPG, click here.
In production quality assurance applications the DPG allows validation of backpressure characteristics, filtration efficiency and regeneration performance.
In an R&D environment it provides economic and repeatable soot loading of DPFs to support engine and after-treatment development.
Filter Test Housing accessory for bare brick testing
Cambustion offer a Filter Test Housing for use with the DPG. This reusable DPF housing allows an uncanned filter to be fitted to the DPG and loaded / regenerated as required. The filter can be quickly removed for weighing and examination, even at elevated temperatures.
This ability is particularly advantageous in both R&D and Quality Control applications, and allows filters to be tested before coating or other final processes take place.
For further information, please download the DPG and FTH brochures, together with the specifications or contact Cambustion.
DPF Testing Service
Cambustion also offer a DPF loading / testing service, using the DPG. For more information please see our Engineering Services pages.