Conventional Analyzers

The Flame Ionisation Detector (FID) is the industry-standard method of measuring engine exhaust hydrocarbons. Conventional FIDs have response times of 1-2 seconds, and are typically used to measure "bag emissions" where the concentration changes very slowly.

A need for fast emissions analyzers

During the 1-2 seconds it takes a conventional FID to respond, an engine will undergo many firing cycles. The conditions inside the combustion chamber can vary significantly between successive firing cycles- particularly when the engine conditions are changing rapidly such as during engine start or speed/load transients. The Cambustion HFR500 has a time response as low as 0.7ms T10-90. This allows the HFR500 to distinguish between two adjacent firing cycles, and even offer information about the variation in HC concentration during a single exhaust stroke.

Benefits of fast emissions analyzers

HFR500 sample head fitted in engine bay

Accurate measurement of exhaust emissions brings valuable insights into engine operation, and assists calibration engineers in reducing the engine out emissions. This can assist in emissions compliance while reducing after-treatment costs.

The fast FID (sometimes known as an fFID) is carefully designed and calibrated to be linear to well above misfire HC levels (e.g. 42,000 ppm C3 for a complete stoichiometric misfire in a gasoline engine) so that accurate concentrations during these important events can be recorded.

Applications

For all gasoline engines (port- or direct-injection) the most challenging phase of operation (from an emissions viewpoint) is the cold start. (Download a pdf presentation about gasoline cold start calibration)

The cold catalyst is initially unable to convert any of the engine-out emissions, and these therefore reach the tailpipe. Since in a cold gasoline engine the vaporization of the fuel is poor, additional fuel (i.e. more than stoichiometric ratio alone requires) must be injected during crank, to achieve an ignitable mixture in the cylinder. The rapid heat release caused by the first firing cycle leads to a rapid vaporization of this excess liquid fuel, and the second firing cycle may easily be rich, leading to high concentrations of unburnt hydrocarbons in the exhaust.

The HFR500's unique ability to measure cycle-by-cycle HC emissions during and after start allows engineers to optimize engine calibration for cold start; maintaining startability while minimizing these highly significant HC emissions. 

On gasoline engines, the use of an evaporative emissions canister to trap the HC vapours from the fuel tank requires the canister to be purged in to the intake system.  Normally, this is scheduled to occur a few minutes after engine start, but can lead to significant levels of additional fuel entering the combustion chambers.  With some additional accessories, it is possible to use the fast FID to sample from the intake (even downstream of the throttle) and measure the actual [HC] which are contributing to the engine’s fuelling.  Similar techniques can be used for fuel emerging from the crankcase blow-by gases via the crankcase ventilation system.

Alternative fuels such as ethanol (or a mix of gasoline and ethanol) have different vaporization characteristics and require additional calibration for cold start.

Once the engine is running, transients in speed and load can lead to hydrocarbon "spikes" (brief periods of high emission), since the airflow into the engine can change more quickly than the fuel. Conventional analyzers with time responses of around a second can not resolve these events, but the HFR500 offers valuable data about the exhaust HC concentration, on a cycle-by-cycle and cylinder-by-cylinder basis.

The HFR500 is available with support for AK protocol, allowing easy integration with the test bench for improved test reliability and reduced workload.

To read more about the application of the HFR500 to engine start and fuel puddle studies visit our Spark Ignition Engines page.

For more information on these and other applications please see Applications & Sample data.

The brochure may be downloaded here.

Please contact Cambustion for more information and prices.

Key Application Notes 
Title Data type Download File Size Last updated
Flame Traverse Sampling Application note PDF icon CLD06v01 Fast gas analysis traversing a methane flame.pdf 607.88 KB 22-Sep-2015
Cold start PFI gasoline HC emissions Application note PDF icon hfr01v02 si cold start.pdf 77.14 KB 18-Aug-2009
High rpm fuelling control Application note PDF icon hfr02v01 high rpm.pdf 149.57 KB 19-Aug-2009
HC emissions from a diesel-engined passenger vehicle Application note PDF icon HFR05v01 Diesel.pdf 288.67 KB 24-Feb-2015
Suitability of HFR500 for ethanol measurements Application note PDF icon hfr06v01 ethanol.pdf 13.2 KB 19-Aug-2009
Gasoline Direct Injection (GDI) HC emissions Application note PDF icon HFR07v01 GDI HC emissions.pdf 128.38 KB 24-Feb-2015
Intake manifold measurement of “found fuel” PDF icon HFR08v01 intake sampling.pdf 547.89 KB 02-Feb-2015
Combustion instability detection during catalyst heating phase of GDI cold start Application note PDF icon HFR09v01 GDI cold start catalyst heating strategy combustion instability.pdf 543.55 KB 24-Aug-2016
Cycle-by-cycle AFR measurement of a cold start using an NDIR500 and HFR500 Application note PDF icon NDIR03v02 AFR measurement.pdf 442.5 KB 24-Feb-2015