John Clifford

Monitoring of carbon dioxide exhaust emissions using mid-infrared spectroscopy

An optical fibre sensor for monitoring carbon dioxide emissions from modern road vehicles and operating in the mid-infrared spectral region is reported. The wavelength range of operation is centred at 4.23??m and has required a novel implementation of this sensor using low cost and robust components. The sensor is shown to be capable of detecting CO2 to a minimum level of 350?ppm, to be stable over several hours of continuous operation and insensitive to the presence of other species present in the exhaust.

Simulation and measurement of carbon dioxide exhaust emissions using an optical-fibre-based mid-infrared point sensor

A novel optical-fibre-based sensor for measurement of CO2 gas emission concentrations in exhaust systems of a motor vehicle is reported. The sensing principle is based on open-path direct absorption spectroscopy in the mid-infrared range. The sensor system comprises of low cost and compact mid-infrared components, which make it suitable for insertion into the exhaust system of automotive vehicles. The sensor utilizes a calcium fluoride CaF2 narrow band pass (NBP) filter for detection of CO2 gas without cross-sensitivity to other gases present in the exhaust system. Furthermore, it can be integrated into the mechanical and electronic interface systems of existing vehicles without any problems.

Detection of high level carbon dioxide emissions using a compact optical fibre based mid-infrared sensor system for applications in environmental pollution monitoring

A novel and highly compact optical fibre based sensor system for measurement of high concentrations CO2 gas emissions in modern automotive exhaust is presented. The sensor system works based on the principle of open-path direct absorption spectroscopy in the mid-infrared wavelength range. The sensor system, which comprises low cost components and is compact in design, is well suited for applications in monitoring CO2 emissions from the exhaust of automotive vehicles. The sensor system utilises calcium fluoride (CaF2) lenses and a narrow band pass (NBP) filter for detection of CO2 gas. The response of the sensor to high concentrations of CO2 gas is presented and the result is compared with that of a commercial flue gas analyser. The sensor shows response times of 5.2s and demonstrates minimal susceptibility to cross interferences of other gases present in the exhaust system.

Vibration-insensitive temperature sensing system based on fluorescence decay and using a digital processing approach

A fluorescence-based temperature sensor system using a digital signal processing approach has been developed and evaluated in operation on a working automotive engine. The signal processing approach, using the least-squares method, makes the system relatively insensitive to intensity variations in the probe and thus provides more precise measurements when compared to a previous system designed using analogue phase-locked detection. Experiments carried out to determine the emission temperatures of a running car engine have demonstrated the effectiveness of the sensor system in monitoring exhaust temperatures up to 250 °C, and potentially higher.

Mid-infrared point sensor for in situ monitoring of CO2 emissions from large-scale engines.

This paper describes an optical fiber based system that has been developed for the monitoring of carbon dioxide emissions in situ within engines above 500 kW. Conventional sensors, reviewed here, fail to meet monitoring requirements, such as lifespan, accuracy, and robustness. This paper describes a sensor designed as a single point reflective probe configuration using low cost, compact mid-infrared optical components, making it suitable for insertion in large-scale engines including automotive tailpipes. The response of the sensor to carbon dioxide supplied from a cylinder in the laboratory environment is presented, as well as a number of experimental results taken in situ in an exhaust of an automotive diesel engine (smaller than 500 kW). The sensor is shown to have a long term stable operation over a wide range of concentrations (2%-15% CO(2)) with a lower detection limit smaller than the lowest value encountered in modern day engines.

Optical fibre sensors for the monitoring of harmful emissions from land transport vehicles

In order to meet increasingly stringent emission control laws it is necessary to develop a sensor that can accurately monitor the level of pollutants entering the atmosphere from land transport vehicles. These pollutants are generally a mixture of hot gases and particulates. An optical fibre sensor is particularly well suited to this task. Due to its small size and weight it is minimally invasive making it suitable for insertion into the vehicles exhaust system. Optical fibres are immune from poisoning by the analyte gases, although they do require shielding from airborne particulates. As they do not transmit electricity they are also highly safe and furthermore they are immune from electromagnetic interference. To detect the presence of the gases it is proposed to use an optical absorption technique. The majority of gases of industrial and environmental importance have their fundamental absorption line in the mid-infrared region of the electromagnetic spectrum, with weaker overtones in the near infrared. Due to the greater availability of components, optimised for communications, most optical fibre gas sensing has taken place in the near-infrared region of the spectrum. In this paper mid-infrared optical fibre gas sensing techniques are investigated and the results of the investigation are presented. Due to the inhomogeneous state of the gas flow it is necessary to measure temperature especially just upstream of the after-treatment section where this can rise to as high as 650oC with large temporal gradients. Measurements of temperature of hot gases from a full size test engine using an optical fibre probe based on fluorescence decay time measurements are also presented.

Online monitoring of exhaust emissions using mid-infrared spectroscopy

Existing automotive sensors do not quantify the levels of pollutants entering the atmosphere; instead they merely indicate that pollution is occurring. However to meet European legislation on emission control, it is necessary to quantify the levels of each type of pollutant leaving the exhaust of a vehicle. This paper discusses the development of an optical sensor suitable for the detection of gas emissions from a motor vehicle based on mid-infrared spectroscopy. Initial tests to detect carbon dioxide using low-cost mid-infrared components are described and a detection system, which could be fitted to an automobile, is outlined.

Overview of the OPTO-EMI-SENSE Project: Optical Fibre Sensor Network for Automotive Emission Monitoring

An optical fibre based system has been developed which is capable of monitoring the presence of exhaust gas emissions and measuring their temperature on line in the exhaust system of a modern vehicle. There exists at present no commercial sensor, which is capable of providing online measurements of these exhaust gases as required by European legislation. The design of this sensor using low cost and compact optical components, which make it suitable for operation on board a vehicle, is discussed. The sensor is capable of detecting NO, NO2, SO2 to a minimum detection threshold of 5ppm, CO and HCs to a minimum threshold of 200 ppm, CO2 in the range 300 ppm to 20% and temperature from 0°C to 900°C. Results measured in the exhaust of a modern engine are presented for each of these parameters.

Detection of carbon dioxide emissions from a land transport vehicle using a mid-infrared optical fiber based sensor

An optical fibre based exhaust gas sensor has been developed from low-cost mid-infrared components which is capable of detecting carbon dioxide (CO2) emissions from both diesel and petrol engines. The optical fibre sensor is not cross sensitive to other gaseous species in the exhaust such as water vapour (H2O), carbon monoxide (CO), oxides of nitrogen (NOx) or oxides of sulphur (SOx). Initial tests of this sensor on a modern diesel engine are outlined in this paper.

Mid-Infrared Optical Fibre Sensor Based Detection of Exhaust Gas Emissions

In order to satisfy increasingly stringent automotive emission control laws, it is necessary to develop sensors that are capable of quantifying exactly the pollutants entering the atmosphere. The development of a mid-infrared optical fibre based sensor suitable for the detection of automotive emissions is discussed in this paper. Mid-infrared spectroscopy is deemed suitable for the task as the fundamental absorption lines of the majority of the pollutant exhaust gases are in the mid-infrared region of the spectrum. This paper focuses on the monitoring of carbon dioxide gas as it has significant absorption in the mid-infrared.