Conventional CLD 1-2 second response time
Cambustion Fast CLD 1-10 millisecond response time
The Chemiluminescence Detector (CLD) is the industry-standard method of measuring engine exhaust nitric oxide concentrations. Conventional CLDs have response times of 1-2 seconds, and are typically used to measure “bag emissions” where the concentration changes very slowly. Cambustion's fast CLD's allow NO, total NOx and NO2 (via LIF) measurements at up to 1kHz. This gives full resolution of short lived transients such as tip-ins or even individual firing cycle events.
A need for fast emissions analyzers
During the 1-2 seconds it takes a conventional CLD 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. Cambustion fast CLDs have a time response as low as 2 ms T10-90. This allows the analyzers to distinguish between two adjacent firing cycles, and even offer information about the variation in NO/NO2 concentration during a single exhaust stroke.
In addition, increased awareness in local air quality has led to the need for fast and highly sensitive measurement of nitric oxides. To accurately determine the risk to human health it is critical these sometimes alarmingly high short-term exposures are quantified effectively.
Benefits of fast emissions analyzers
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 CLD is carefully designed and calibrated to be linear to well above expected engine engine out levels (e.g. 0-10'000ppm range) while still retaining impressive sensitivity.
The CLD50 has allowed investigations into the real emissions exposure from vehicles allowing local and national health authorities draw conclusions on road infrastructure and traffic flow changes, clean air zones, retrofit schemes and many more emission reducing tools.
Cambustion NOx Analyzer Range
CLD500 two channel analyzerFind out more
Using a chemi-luminescence detector, Cambustion fast NOx analysers offer NO&NO2 measurements at up to 500Hz. This is fast enough to observe NOx from individual firing cycles (which can vary substantially) and observe the consequent performance of NOx aftertreatment.
The entry level fast CLDFind out more
New in 2021 is the CLD50 “entry level” fast CLD designed for both engine and non-engine single channel applications where a 15 ms T10-90 response time is sufficient. The CLD50 is capable of both [NO] and [NO2] measurement directly (NO2 via LIF) with only an oxygen and power supply needed.
The ability to measure cycle by cycle NO and NOx allows researchers and engineers to investigate and quantify features such as NOx breakthrough during lambda excursions on a gasoline engine.
Common to both Diesel and gasoline engines, EGR is a widely adopted technique for controlling NOx emissions. During transient operation, delays and imperfect control of EGR flow may lead to spikes in transient NOx emissions. Furthermore, distribution of recirculated exhaust gas between cylinders on a multi-cylinder engine is not always equal. This can lead to one cylinder receiving too little EGR, with a consequent increase in NOx emissions. The ability of the CLD500 to measure gas from a single cylinder (sampling in the port) as well as in the mixed exhaust provides crucial data to overcome such issues. Combined with fast CO2 measurement from Cambustion's NDIR500, the CLD500 allows the user to directly correlate NOx emissions and delivered EGR, even on a cycle-by-cycle basis.
A current major concern with urban air quality is the NOx emissions from diesel passenger vehicles. Although legislated NOx limits for new vehicles have been steadily reduced over many years, a similar reduction in NOx air pollution hasn’t been achieved. This has been attributed to the Real World Driving Emissions (RDE) of vehicles being only poorly represented by the standard European Drive Cycle. Most OEMs are investigating “off-cycle” emissions by using on-board analyzers to measure directly from the vehicle’s tailpipe during urban and rural driving. The CLD500 fast NOx analyzer can be configured to measure the fast transient [NO] emissions from any vehicle and some data showing the real time [NO] emissions during a real world driving can be seen here.
It is also important to quantify the contribution these emitters have to local and roadside air quality which can in-turn lead to high human exposure to nitric oxides. Due to recent improvements, the CLD50 can be configured for ambient monitoring with detection limits of 5ppb [NO] while retaining a 100ms response time. This allows local and national health authorities to draw conclusions on road infrastructure and traffic flow changes, clean air zones, retrofit schemes and many more emission reducing tools. Please refer to our air quality page for example videos.
Selective Catalytic Reduction (SCR) is another method of reducing NOx emissions using ammonia or urea, and is increasingly used in heavy duty Diesel applications. SCR requires careful control of the conditions and reactant concentrations in the catalyst, and the CLD500 is used to monitor catalyst performance, both at cold start and during transient operation.
Lean NOx Trap (LNT) is another technology for reducing NOx emissions- using a NOx absorbing element which stores the NOx, and periodically purging the absorber while providing excess hydrocarbons which react with the NOx as it is released. The reactants then exit the tailpipe as H2O and N2. To perform well, the LNT and supply of reactants must be carefully matched to the exhaust conditions. The CLD500 is used to monitor LNT performance, even during transient conditions.
The CLD500 is available with support for AK protocol, allowing easy integration with the test bench for improved test reliability and reduced workload.
For more information see Applications and Sample data.
Key Application Notes
|Title||Data Type||Download File||Size||Last Updated|
|Title||Transient NOx measurements from motorcycle real world driving||Data Type||Application note||Download File||cld10v02-motorcycle-rde-transient-nox-emissions.pdf||Size||1.63 MB||Last Updated|
|Title||Transient NOx from in-service buses||Data Type||Application note||Download File||cld09v01-transient-nox-from-in-service-buses.pdf||Size||1.18 MB||Last Updated|
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