Fast-response Flame Ionization Detector Research Articles

J0550105 2次元丘模型の上流から点源放出されたエチレンの乱流拡散過程

We have investigated experimentally the turbulent diffusion processes of ethylene emitted from a point source in the upstream region of a two-dimensional hill model. By using the fast-response flame ionization detector (FFID), the mean and fluctuating concentration distributions are measured quantitatively. It is found that in the separated region, the mean concentration profiles are almost uniform in the vertical direction, and the locations of the maximum concentration appear along the dividing streamline formed in the downstream region of the hilltop. On the other hand, the r.m.s. values of concentration fluctuations become maximum at the outer edge of the concentration boundary layer, and become small in the separated region where the mean concentration keeps a high value.

Experimental investigation of the evaporation characteristics of the fuel in a direct-injection spark ignition engine subjected to a direct-start process

Because stopping an engine in the idling state and quickly restarting the engine can improve the engine’s fuel consumption, this paper studied the direct start of a direct-injection spark ignition engine that does not require a larger electrical starter for the conventional start–stop system. The formation of the fuel–air mixture before the first combustion determines the success of the direct start because the explosion energy acquired from first combustion to move the crankshaft is relatively small. The purpose of this study is to explore the evaporation characteristics of the gasoline in a spray chamber that was designed to simulate the cylinder of a direct-injection spark ignition engine. Fundamental studies were conducted to investigate the evaporation process under direct-start conditions. A numerical study was also conducted using evaporation and wall interaction models. The measurements obtained using a fast-response flame ionization detector hydrocarbon detection system (HFR500) indicated that the evaporation ratio of the gasoline spray increased with increasing temperature and achieved an upper limit of 90% at an ambient temperature of 140 °C. The lower limit of the equivalence ratio for a successful direct start should be 1.4–1.7 when the temperature is less than 100 °C. Suitable ignition timing of the first combustion should be 25 ms after the start of injection. Methanol–gasoline and ethanol–gasoline were tested in this study, and a poor evaporation performance was observed owing to the higher evaporation heat values of these fuels. Consequently, gasoline is preferable to oxygenated fuels for the direct start of direct-injection spark ignition engines.

Atmospheric dispersion modelling over complex terrain at small scale

Previous study concerned of qualitative modelling neutrally stratified flow over open-cut coal mine and important surrounding topography at meso-scale (1:9000) revealed an important area for quantitative modelling of atmospheric dispersion at small-scale (1:3300). The selected area includes a necessary part of the coal mine topography with respect to its future expansion and surrounding populated areas. At this small-scale simultaneous measurement of velocity components and concentrations in specified points of vertical and horizontal planes were performed by two-dimensional Laser Doppler Anemometry (LDA) and Fast-Response Flame Ionization Detector (FFID), respectively. The impact of the complex terrain on passive pollutant dispersion with respect to the prevailing wind direction was observed and the prediction of the air quality at populated areas is discussed. The measured data will be used for comparison with another model taking into account the future coal mine transformation. Thus, the impact of coal mine transformation on pollutant dispersion can be observed.

J057022 円柱後流におけるエチレンの乱流拡散過程 : 速度と濃度の同時計測(〔J057-02〕乱流における運動量、熱、物質の輸送現象(2))

We investigated a turbulent diffusion process of ethylene in a wake flow formed behind a circular cylinder installed in a grid turbulence using a simultaneous measurement system with a fast-response flame ionization detector (FFID) and a hot wire anemometer. Due to the existence of Karman vortex street, the mean and rms concentration distributions in the lateral direction have two peaks. The correlation coefficient between the streamwise velocity and concentration fluctuations indicates positive and negative values in the center and edge of the plume, respectively. Moreover, both of velocity and concentration spectra show the distinct peak at the dominant frequency caused by the vortex shedding.

J056021 乱流境界層中に点源供給された濃度場の乱流特性([J05602]乱流における運動量,熱,物質の輸送現象(2))

An experimental investigation has been made on the concentration field dispersed from a ground-level point source in a turbulent boundary layer. Fluctuating concentration signals of ethylene are measured by a fast-response flame ionization detector (FID). The mean concentration profiles are well described by the Gaussian plume model with a modification of the exponent in the wall-normal direction. The cross-sectional distributions of the concentration fluctuation intensity show two maxima near the wall. It is found that the instantaneous concentration field spreads very widely compared with the mean field.

Spark timing and fuel injection strategy for combustion stability on HEV powertrain

Stringent regulations on exhaust emission and fuel economy for vehicles have become major issues in the automotive industry. Hybrid electric vehicles (HEVs) are one of the crucial alternative plans over current conventional vehicles, but they have drawbacks, such as the increase of engine-out total hydrocarbon (THC) emission and the deterioration of combustion stability with frequent engine stopping and restarting. This study is an experimental investigation to obtain a better understanding of THC emission characteristics during engine restart and deceleration driving on a HEV powertrain of a parallel motor/generator type. Using a fast response flame ionization detector (FFID) and a specified tool for cycle by cycle and cylinder to cylinder investigation, the combustion stability and engine control characteristics were analyzed during the transient state of the HEV powertrain. The experimental conditions cover variations of the high voltage battery state of charge (SoC), spark ignition timing and injected fuel mass. As an experimental result, the effect of the spark timing control was slight, but the reasonable injection duration for stable combustion was more than 7ms at the first cycle shortly after engine start-up, although the injection rate was 2.7–3ms in the idle state. The reason for the greater volume of fuel being injected was that the fuel deposited in the cylinder and intake port was reduced due to discharge and vaporization during the deceleration step before the idle stop. A basic control algorithm for combustion stability under engine restart conditions was built by considering the experimental results.

Isothermal flow measurements in a gas turbine combustor using a fast flame ionization detector

A fast-response flame ionization detector (FFID) has been used to study isothermal gas transport and mixing inside a gas turbine combustion chamber. The large, highly linear dynamic range of the FFID coupled with a frequency response that extends up to approximately 200 Hz can reveal large-scale features of interest in turbulent flows. Experiments were performed in a ground-based test facility simulating high-altitude restart conditions. Pulses of propane were discharged into the core swirler of a fuel injector through a high-speed valve. The mole fraction of this tracer was monitored at various locations inside the combustion chamber. These measurements allowed the identification of recirculation timescales and flow instabilities at different points inside the combustion chamber, providing important insights into the altitude restart process.

Combustion stability analysis during engine stop and restart in a hybrid powertrain

A cycle-resolved analysis system was designed with the specified measurement instruments to investigate the characteristics of combustion stability in a mild gasoline hybrid powertrain. A Fast Response Flame Ionization Detector (FFID), cylinder pressure transducer and engine torque transducer were used to observe both the engine-out THC emissions and engine performance during a brief moment of engine restart. This research aimed to improve combustion stability and was performed by varying the battery State Of Charge (SOC), injection duration and ignition timing. The results indicate that engine combustion tends to be more stable with longer fuel injection durations and advanced ignition timing, while the effect of the battery SOC is negligible. Also, peculiar differences in the catalyst conversion efficiency at the front and rear of the catalyst during engine restart and deceleration were revealed, with the degree of HC oxidation being the suspected cause. This study not only analyzed the engine control and engine-out total hydrocarbon (THC) emission characteristics, but also implemented control strategies that allowed for combustion stability during engine stop and restart operation.

Effects of Spark Ignition Timing and Fuel Injection Strategy for Combustion Stability on HEV Powertrain during Engine Restart and Deceleration Driving

Stringent regulations of exhaust emission and fuel economy from vehicles have become major issues in the automotive industry. Hybrid Electric Vehicle (HEV) can be one of the crucial alternative plans over current conventional vehicle, but they have drawbacks such as the increase of engine out total hydrocarbon (THC) emission and the deterioration of combustion stability at frequent engine stop and restart. This study performs experimental investigation to obtain a better understanding of THC emission characteristic at engine restart and deceleration driving on a HEV powertrain of parallel motor/generator type using a Fast response Flame Ionization Detector (FFID) and specified tool for cycle by cycle, cylinder to cylinder combustion and engine control characteristic analysis during transient state of HEV powertrain. The experimental conditions cover variation of high voltage battery State of Charge (SoC), spark ignition timing and injected fuel mass. As an experimental result, the effect of the spark timing control is so little, but the reasonable injection duration for stable combustion is more than 7 (ms) at the first cycle shortly after engine start-up by motor although the injection rate is 2.7 ~ 3 (ms) at idle state. The reason why more fuel was injected was that the deposited fuel in the cylinder and intake port was reduced due to discharging and vaporization during deceleration step before idle stop.

Effect of synchronized secondary air injection on exhaust hydrocarbon emission in a spark ignition engine

A synchronized secondary air injection (SAI) method has been proposed to reduce hydro- carbon (HC) emission by injecting secondary air intermittently into the exhaust port. The method has been tested in a single-cylinder spark ignition engine operating at cold-steady/cold-start conditions. HC concentration and exhaust gas temperature were monitored with a fast-response flame ionization detector and with thermocouples respectively. Effects of exhaust air-fuel ratio (A/F), engine A/F, spark timing and air injection timing have been investigated and the results are compared with a continuous SAI method and the baseline condition. Results show that HC reduction rate and exhaust gas temperature are sensitive to the timing of synchronized SAI. Two optimum SAI timings are observed which are at 100° crank angle (CA) after top dead centre (ATDC) and 230° CA ATDC depending on spark timing. At the cold-steady condition, the synchronized SAI is found to be more effective in HC reduction and also has much higher exhaust gas temperature than either the continuous SAI or the baseline condition. At the cold-start condition when a catalyst is not used, the accumulated HC emission during the first 120 s decreases by about 55 per cent with the synchronized SAI compared with that of the baseline condition, while the result with the continuous SAI is comparable with the baseline condition.

Measurements of cycle resolved air-fuel ratio near the spark plug in a spark ignition engine

Mixture preparation is a key contributor to both the combustion and emissions of the automotive gasoline engine. The air-fuel ratio near the spark plug may have an effect on combustion characteristics, especially at low load, since it is related to flame development. Therefore, measurements of the cycle-resolved equivalence ratio near the spark plug are particularly important for a better understanding of their contribution to combustion and emissions. This paper describes how the in-cylinder equivalence ratio was determined from the measured hydrocarbon concentrations near the spark plug using a fast response flame ionization detector (FRFID). The procedures established were then applied to a limited range of engine operating conditions, and the cycle-resolved equivalence ratio near the spark plug was determined from the measured hydrocarbon concentration. The results showed that with premixed propane fuel the cyclic variation in equivalence ratio near the spark plug was quite small and corresponded to the overall equivalence ratio from the universal exhaust gas oxygen (UEGO) sensor signal. However, with gasoline fuel the equivalence ratio near the spark plug varied by up to 10 per cent and did not coincide with the UEGO sensor signal on a cyclic basis. The variation in equivalence ratio near the spark plug affected the heat release rate, which in turn affected the indicated mean effective pressure (i.m.e.p.). The equivalence ratio excursions and its effects during acceleration and deceleration are strongly related to the exhaust emissions, fuel economy and so on. With this in mind, the quantitative measurement method using the measured hydrocarbon concentrations was studied for detailed analysis during transient conditions. It was also observed that cyclic variation in the equivalence ratio near the spark plug might be one cause of cycle-by-cycle variation.

Measurements of particulate mass concentration using atapered-element oscillating microbalance and a flameionization detector

Measurement of particulate mass concentration in the exhaust of automotive engines by means of the filter sampling method prescribed by the USA's Environmental Protection Agency (EPA) is tedious, costly, time consuming and labour intensive. This paper presents a new approach, which is capable of measuring real-time particulate mass emissions in the exhaust of a diesel engine by using a tapered-element oscillating microbalance (TEOM) and a fast-response flame ionization detector (FID). The measuring principle rests on the fact that, by operating the TEOM at 50 °C, water interference is minimized, albeit at the expense of reducing the hydrocarbon content condensed on the particles. This is corrected by a method that consists of a measurement of hydrocarbon gas concentration, used with an empirical correction factor to recover what the filter sampling method would produce. The time resolution for the measurement using this new method is limited by the sampling window of the TEOM which is 0.42 s, though the response of the FID offers a time resolution of milliseconds. Results show that the mass concentration of particulate matter measured by TEOM and FID is well correlated to that based on the conventional EPA filter sampling method. Keywords: particulate mass concentration, tapered-element oscillating microbalance, flame ionization detector, diesel exhaust particulate measurement, correlation to EPA (USA) standard

A time-resolved measurement technique for particulate number density in diesel exhaust using a fast-response flame ionization detector

The fast-response flame ionization detector (FRFID) has been used widely to measure, in real time, the concentration of unburnt hydrocarbons in internal combustion engines. In this study, a FRFID is modified to measure, simultaneously, the concentration of the gaseous hydrocarbons and the number density of soot particulates present in the exhaust of a turbocharged Dl diesel engine. The system is also capable of differentiating the hydrocarbon fraction of the particulates from that of gaseous hydrocarbons, hence providing information for deducing the amount of gaseous hydrocarbon that is adsorbed by or condensed onto the surface of the particulates. Another unmodified FRFID, with a particulate collector placed immediately upstream of it, is used to determine the total particulate matter in terms of mass concentration. Experimental results show that the particulate number density measured by the modified FRFID is correlated well with the mass concentration determined by the filtration method under various engine operating conditions. The hydrocarbon fraction of the particulates shows a similar trend to the gaseous hydrocarbon present in the raw exhaust gas stream under various steady-speed engine test runs. A transient engine load acceptance test concludes the usability of this modified FRFID to measure, on a time-resolved basis, the particulate number densities with trends similar to those of generally known smoke opacities.

Relation between flame propagation characteristics and hydrocarbon emissions under lean operating conditions in spark-ignition engines

The objective of this work was the investigation of the hydrocarbon emissions of a spark-ignition (SI) engine under very lean operating conditions. A series of experiments has been conducted in which cycles exhibiting high hydrocarbon (HC) emission were analyzed using the fast response flame ionization detector (FID) in conjunction with a recently developed diagnostic, the head gasket ionization probe. It was found that for relative air/fuel ratios (λ) close to 1.4, single-cycle emissions correlate with single-cycle maximum pressure and indicated mean effective pressure (IMEP), which suggests that around that point postflame oxidation starts becoming less important. For relative air/fuel ratios greater than 1.4, cycles with very high emissions appear. We have divided these partial burns into two types depending on their HC-emission signature profiles and flame propagation characteristics. The first type is a global, slow-burning cycle that does not finish the oxidation of the charge by the time the exhaust valve opens. The second type is a normal burning cycle that exhibits a localized quench phenomenon: although the flame has propagated to the extremities of the cylinder, it has left a region of the charge unburned. The two types of cycles have different IMEP and flame speeds for the same mass fraction of the charge burned, as well as different HC emissions because of the different spatial and temporal location of the partial burn and the varying degrees of postflame oxidation the HC are subjected to.

Monitoring of the Mixture Strength in the Cylinders of a Port-Injected Gasoline Engine During Transient Operation

A method has been developed which allows monitoring of the air—fuel ratio within the cylinders of a running gasoline engine. The method, which uses a fast-response flame ionization detector (FID), is capable of resolving the air—fuel ratio of individual consecutive engine cycles This method was used to monitor the air—fuel ratio in a port-injected gasoline engine during fast throttle opening. The results obtained show that for a handful of engine cycles the air—fuel ratio departs from the stoichiometric Value. Using additional measurements of the air and fuel supplied to the engine, it was possible to investigate the accumulation of fuel on the inlet port walls of the engine during the throttle opening. The results presented in this paper suggest that the departure of the air—fuel ratio from the stoichiometric value is shorter lived than that recorded by other investigators who used exhaust oxygen sensors for their tests.

In-Cylinder Measurement of Mixture Strength in a Turbocharged Natural Gas Engine

Measurements of in-cylinder mixture strength, during compression and combustion, were made on a natural gas engine using a novel fast-response flame ionization detector (FID). The Collings FID was found to be an effective instrument for measuring the spatial and temporal development of mixture strength in such engines. It is necessary when using the FID to establish suitably controlled bench tests to validate its pressure independence. Other parameters, such as the transit time and the frequency response of the instrument, may be confirmed by similar bench tests. A comparison is made between experimental measurements of mixture strength in the prechamber close to ignition and the results of a computational fluid dynamics (CFD) study of the mixing processes.