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An on-board version of a fast response chemiluminsescence analyzer with a 3-millisecond response time enables the recording of high temporal resolution transient NOx emissions during cold start and pull-away, gear changes, speed bumps and other real world transient conditions. Tests were initially performed on a 1.6 litre turbo GDI vehicle before comparison with a diesel vehicle. The data has been correlated with on-board engine data available from the vehicle’s electronic control unit to study the underlying causes of these short-duration events. Exhaust gas was generally sampled from downstream of the after treatment system but before the silencer (muffler) to preserve all high frequency detail and to allow accurate integration of pollutant concentration and engine exhaust mass flow.

Cyclic combustion variability (CCV) is an undesirable characteristic of spark ignition (SI) engines, and originates from variations in gas motion and turbulence, as well as from differences in mixture composition and homogeneity in each cycle. In this work, the cycle to cycle variability on combustion and emissions is experimentally investigated on a high-speed, port fuel injected, spark ignition engine. Fast response analyzers were placed at the exhaust manifold, directly downstream of the exhaust valve of one cylinder, for the determination of the cycle-resolved carbon monoxide (CO) and nitric oxide (NO) emissions. A piezoelectric transducer, integrated in the spark-plug, was also used for cylinder pressure measurement. The impact of engine operating parameters, namely engine speed, load, equivalence ratio and ignition timing on combustion and emissions variability, was evaluated.

An accurate prediction of residual burned gas within the combustion chamber is important to quantify for development of modern engines, especially so for those with internally recycled burned gases and HCCI operations. A wall-guided GDI engine has been fitted with an in-cylinder sampling probe attached to a fast response NDIR analyser to measure in-situ the cycle-by-cycle trapped residual gas. The results have been compared with a model which predicts the trapped residual gas fraction based on heat release rate calculated from the cylinder pressure data and other factors. The inlet and exhaust valve timings were varied to produce a range of Residual Gas Fraction (RGF) conditions and the results were compared between the actual measured CO2 values and those predicted by the model, which shows that the RGF value derived from the exhaust gas temperature and pressure measurement at EVC is consistently overestimated by 5% over those based on the CO2 concentrations.

A study has been conducted to measure the transient HC, NOx, CO, CO2 and particulate emissions from a modern 1.6-liter, Euro IV-stage turbocharged Gasoline Direct Injection (GDI) passenger car engine. The tests were conducted using ultra-fast-response analyzers with millisecond response times so that the real-time effects of the individual combustion events and the ECU's start strategy could be studied. The results show that through the use of an aggressive cold start calibration strategy, the catalyst is very efficient after light-off at about 30s. However, during this same period, there are signs of partial misfires and rich AFR excursions, both of which contribute to the overall tailpipe emissions. The data from the fast-response analyzers allowed clear discrimination between rich events and partial misfires and would allow appropriate calibration actions to be taken.

A study has been conducted to measure the particle number emissions from a current-generation 1.6-liter, Euro IV-compliant turbo-charged Gasoline Direct Injection (GDI) passenger car engine. A fast-response particle size spectrometer was used along with a PMP-compliant particulate measurement system to measure the effect of various engine parameters on the particulate emissions during the New European Drive Cycle (NEDC). Overall particle number is shown along with further analysis of the transient particle emissions. The cold start clearly affects particle formation with approximately 50% of the cumulative particle number being emitted within 200 seconds of the start. Even beyond 200 seconds, the particle number emissions fall as the test progresses and are generally consistent with increases in engine coolant temperature indicating that cold engine fuel preparation issues are contributing to the particle number count.

The control of transient emissions from turbocharged diesel engines remains an important objective to manufacturers, since newly produced engines must meet the stringent criteria concerning exhaust emissions levels as dictated by the legislated Transient Cycles. In the present work, experimental tests are conducted on a medium-duty, turbocharged and after-cooled diesel engine in order to investigate the behavior and formation mechanism of nitric oxide (NO), smoke and combustion noise emissions under various transient operating schedules including acceleration, load change and starting. To this aim, a fully instrumented test bed was set up in order to record and research key engine and turbocharger variables during the transient events. The main parameters measured were nitric oxide concentration and smoke opacity (both using ultra-fast response analyzers) as well as combustion noise.

A short study has been conducted to measure both AFR and residual gas fraction on a cycle-by-cycle basis for a gasoline engine during cold start and during a throttle transient. In-cylinder and exhaust port measurements were recorded using a fast response NDIR instrument to provide some insight in to the dynamic processes involved during these important transient engine conditions. The CO&CO2 results are presented showing evidence of the large cyclic variability of fuel delivery during the first few firing cycles of the start. Misfires are also identified. A description of a post-processing tool is discussed for conversion of this data to AFR. It is hoped that this measurement method will be valuable to engine researchers and calibrators as a tool to understanding and lowering cold start and throttle transient HC and CO emissions as well as validating internal EGR models.

For domestically produced passenger car gasoline fuelled vehicles, the forthcoming task of emissions compliance in India (Bharat-IV by 2010) may require a more detailed knowledge of transient engine behaviour by Indian engineers. Under steady state conditions and with reasonable fuel preparation, three-way catalytic converters can remove around 98% of legislated pollutants. However, during cold start and gear changes, the transient emissions are not fully converted by the catalyst; the cold start alone contributing typically 90% of the total Cycle Hydrocarbon (HC) emissions for the Euro- IV drive cycle [1]. This paper presents data measured pre and post the three-way catalyst on a EURO- III compliant European manufactured production Port-Fuel-Injection (PFI) gasoline engine running on a FTP drive cycle. The transient emissions were measured using fast response gas analyzers, with time response giving resolution at better than engine firing frequency.

The gaseous and particulate emissions from a diesel passenger car have been studied during cold start and Diesel Particulate Filter (DPF) regeneration events occurring during the New European Drive Cycle (NEDC). During the initial phase of the cycle, Diesel Oxidation Catalyst (DOC) light-off was seen to be highly dynamic with catalyst efficiency changing dramatically with changes in catalyst temperature. Accumulation mode particulate emissions were sampled directly from the exhaust after the DPF. From cold start with a clean (regenerated) DPF, accumulation mode particle emissions were seen to be very much higher than those from a loaded DPF. This accumulation mode slip lasted only approximately 200 seconds. During regeneration of the DPF, the oxidation of trapped soot was associated with a large tailpipe emission of nucleation mode particles.

This paper examines cold start of a gasoline PFI engine using a fast λ (normalised AFR) measurement technique. The technique uses established fast gas sensing equipment and post-processing calculations to obtain λ with a response time T90-10% of 8ms. The fast λ is compared with UEGO data. Known characteristics of the UEGO include slower T90-10% and output errors when subjected to high quantities of HC; the new technique is shown to avoid these issues. Five cold starts are performed. Fast λ can resolve each cycle. Differences were seen between the UEGO and fast λ and these are attributed to the characteristics mentioned above. Good repeatability was seen over the starts and the fast λ was similarly repeatable. This data will be of importance to reduce emissions over this critical part of the drive cycle.

This paper describes the application of a non-dispersive infrared-based instrument designed to measure CO with a response time of 7ms. Spark ignition engine emission measurements recorded during the first 505 seconds of an FTP75 drive-cycle for a 4 cylinder engine are presented, including fast response hydrocarbon and NO measurements. An analysis of the engine-out (pre-catalyst) exhaust gas is provided. Data collected simultaneously with a standard emissions test stand and conventional dilution tunnel are compared to the high frequency measurements. Fast CO analysis provides new insight into cold-start fuelling calibration and cylinder-to-cylinder AFR variation. Under rich conditions, the strong dependence of CO production on the quantity of excess fuel allows a significantly faster estimate of engine stoichiometry than a UEGO sensor.

A new fast response NO detector, based on the chemiluminescence (CLD) method has been used to measure continuous, real time levels of NO in the cylinder, and simultaneously in the exhaust port of a virtually unmodified production SI engine. The real time NO concentration data show a great deal of information. Simultaneous NO measurements taken in-cylinder at sample points a few millimetres apart show substantial differences. Exhaust and in-cylinder levels from the same cycle show even greater differences, though the levels on average are well correlated.

A novel Fast Response Chemiluminescence Detector and a Fast Flame Ionization detector have been used to examine the instantaneous NO and unburnt hydrocarbon concentration in the cylinder and exhaust port of a DI Diesel engine. The in-cylinder results indicate very high levels of NO in the premixed phase of combustion, followed by generally lower levels during the diffusion burning phase. Hydrocarbon signals also indicate significant detail. The in-cylinder uHC signal is consistent with the probe location being between two of the fuel sprays. Both in-cylinder and exhaust results indicate rather high cyclic variability in the NO levels at steady conditions. Variations in the timing and structure of the exhaust uHC signal during the valve open period with load may give insight into the fuel spray/air motion.