The gases emissions measurement systems in internal combustion engines are strict and expensive nowadays. For this reason, a virtual instrument was developed to measure the combustion emissions from an internal combustion diesel engine, running with diesel-biodiesel mixtures. This software is called virtual instrument for emissions measurement (VIEM), and it was developed in the platform of LabVIEW 2010® virtual programming. VIEM works with sensors connected to a signal conditioning system, and a data acquisition system is used as interface for a computer in order to measure and monitor in real time the emissions of O2, NO, CO, SO2, and CO2 gases. This paper shows the results of the VIEM programming, the integrated circuits diagrams used for the signal conditioning of sensors, and the sensors characterization of O2, NO, CO, SO2, and CO2. VIEM is a low-cost instrument and is simple and easy to use. Besides, it is scalable, making it flexible and defined by the user.
Air pollution is caused in large part by vehicles due to the burning of fossil fuels that emit pollutant gases such as NO, CO, SO2, and CO2 [
The biodiesel utilization is an alternative to reduce the pollutant emissions from vehicles with internal combustion engines that run on diesel. Biodiesel is a renewable and environmental-friendly fuel that is derived from lipids. These react with a short chain alcohol in the presence of a catalyst, no matter whether it is acid, basic, or enzymatic, producing a monoalkyl esters mixture of fatty acids [
Biodiesel has become more important worldwide, and it has shown rapidly industrial growth as an alternative fuel instead of diesel [
International governments and organizations are currently introducing new regulations that establish more strict emission limits to reduce the greenhouse gases emissions [
There are several types of systems in the market for emissions measurement of internal combustion; these may also be fixed or portable depending on their implementation. Conventional systems have several disadvantages, among them we emphasize the high costs purchase from US $2.000 to $20.000, strictness, and impossibility of being scalable [
The virtual instrument implementation has been recently suggested for emissions measurement of internal combustion gases [
National Instruments developed a virtual instrument for the emissions measurement generated by internal combustion engines. This instrument is based on the international emissions standards, in particular, the Euro 4 and EPA. These agencies specify the total amount of pollutants that an internal combustion engine must emit to the atmosphere. These emission factors units are defined in general as gram per mile [
In this work, a virtual instrument for the measurement and monitoring of emissions (VIEM), based on the LabVIEW 2010 virtual programming platform, was developed. VIEM is synchronized with the sensors, data acquisition device, and signal conditioners to measure and register in real time the emissions of O2, NO, CO, SO2, and CO2. The VIEM programming, the electronic schematics diagrams used for the signal conditioning sensors, and the sensors characterization of O2, NO, CO, SO2, and CO2 are presented as results [
Four main devices were involved in the system hardware configuration: firstly, the O2, NO, CO, SO2, and CO2 sensors, the characteristics and operating ranges for each of which are shown in Table
Sensors characteristics and operating ranges.
Features | Operating conditions | ||||
---|---|---|---|---|---|
SO2 | NO | O2 | CO | CO2 | |
Operating ranges | 0–2000 ppm | 0–250 ppm | 0–30% O2 | 0–500 ppm | 0–100% Vol. |
Model | EC4-2000-SO2 | EC4-250-NO | EC410 | EC4-500-CO | IR11BR |
Sensitivity | 8–20 nA/ppm SO2 | 320–480 nA/ppm NO | N/A | 55–85 nA/ppm CO | N/A |
Maximum overload | N/A | 1000 ppm | 100% O2 | 1500 ppm CO | N/A |
Zero in air at 20°C | <±50 ppm SO2 | −0.06 To 4.5 ppm NO | N/A | <±3.1 ppm of CO | N/A |
Zero deviation (−20 to +40°C) | 0 to 4 ppm SO2 | N/A | N/A | N/A | N/A |
Resolution | 5 ppm SO2 | 0.5 ppm NO | 0.1% O2 | 1 ppm CO | N/A |
Response time |
|
|
|
|
N/A |
Temperature range | −20 to +50°C | −20 to +50°C | −20 to +50°C | −20 to +50°C | −20 to +50°C |
Operating humidity | 15–90% RH noncondensing | 15–90% RH noncondensing | 15–95% RH | 15–90% RH noncondensing | 0–99% noncondensing |
Pressure range | 90–110 kPa | 90–110 kPa | 90–110 kPa | 90–110 kPa | 80–120 kPa. |
DC supply recommended | N/A | N/A | N/A | N/A | 5 V |
Operating block diagram of VIEM.
The DAQ digitizes the information that signal conditioners transmit. A DAQ board USB 6009 National Instruments model was used. Digital signals are transmitted to the laptop computer Sony Vaio, VGN-CR190 Intel Core Duo T7100 @ 1.8 GHz model, using Windows 7 operation system.
The infrared sensor works on the basis that is known as the nondispersive infrared analyzer (NDIR), and it is used to detect the presence of carbon dioxide to a volume of 100%. It is possible to determine the CO2 concentration using an infrared source with a specific filter, in which it is installed in the optical-gas cavity. The infrared sensor is connected to an electronic signal. Signals process involves the linearization and compensation in the temperature, using algorithms in the system software [
The infrared gas sensor uses a low-frequency flash lamp drive that is controlled by an excitation circuit. Infrared radiation pulses reflect inside providing a trajectory through the gas and objective. “Pyros” pyroelectric detectors are used to determine the infrared signal change. The active pyroelectric is sensitive to the changes in the infrared wavelengths that are usually absorbed by the gas, passing between the transmitter and receiver. Figure
Blocks diagram of a typical gas detector system using an infrared sensor.
Electrochemical sensors use a solid catalytic electrolyte making electrons flow of a gas cell sample to a gas cell reference possible. In practice, catalytic coated ceramic materials, for example, ZrO2, remove the reference cell that contains a high concentration of O2, as well as an electric sample. When the temperature increases, the electrolyte enables the oxygen ionic components transfer from the reference cell to the sample cell. The surface of the electrolyte has a special electrocatalyst layer catalyzing the transfer processing, and it works as an electrode to attract the released electrons. The ions that move from the reference side to the lateral release electrons of the sample on this surface are forced into the equilibrium. However, since the sample is replenished continuously, an ongoing electrons flow is induced through the measurement load resistance. Thereafter, the electric current is used to deduce the oxygen concentration of the electric gas sample [
Block diagram of a typical gas detection system.
Because the electrons contain a finite catalytic activity, it is necessary to establish a limit to the diffusion speed of objective gas in the sensor, guaranteeing that gas reacts properly. It is performed through a barrier taking a shape of small hole or capillary located on the sensor cover, as is shown in Figure
Internal sensor structure of CO2.
Integrated circuits are used for conditioning and amplifying the signal that the sensors send when the amount information or gas concentration is registered. Registered voltage
Circuit designed for O2 Conditioning signal.
Registered voltage
Circuit designed for NO signal conditioning.
Registered voltage
Circuit designed for SO2 signal conditioning.
Registered voltage
Circuit designed for CO conditioning signal.
Figure
Absorbance fractional versus CO2 concentration.
Figure
Circuit designed for CO2 signal conditioning.
This section shows the programing description of the main blocks that are part of the virtual instrument for emissions measurement that was developed in LabVIEW 2010 platform. In the figures, the operation performed by each programing block is shown.
The VI counts the tests that have been performed to organize the files of the experiment. It is performed through the sub-VI test counter, which it saves in a text file (.txt) with a value that starts at zero and increases to 1 for each VIEM run. The corresponding programming block is shown in Figure
Test counter programming block.
The VI configures the set menus and toolbars using a property-node; these will be shown during the VIEM running. In Figure
Programming block of the configuration window.
While loop 1 runs routines for the configuration and test running. The length of the test is selected using the testing time control. The sample rate configuration is performed using an acquisition time control. The sub-VI “direction by testing” creates the direction and file name containing the samples of test that is in running process. The function sub-VI “Write to Spreadsheet File” creates a new file for each registered variable; this will be shown using a “testing” graphic indicator. The abovementioned is found in the “Event Structure” module, which it enables to synchronize with the computer clock using a time out of 2.00 ms. While loop 1 keeps in ongoing running. In Figure
While loop 1 programming block.
While loop 2 is used to receive the sensor signals. It is possible using sub-VI “acquisition.” Likewise, it configures the storage inputs directions for different variables of measurement displaying them through numerical indicators of “double” type. This series frequency depends directly on the configured value in the “acquisition time” control. This series has a run of “continue if true” type that is controlled using the run/stop button. Figure
While loop 2 programing block.
Sub-VI acquisition is used for data collection of the sensors using a DAQ ASSISTANT Express VI, by which it is configured as a, nondifferential analog input to a voltage range from −10 to 10 volts. The virtual instrument “acquisition” output shows to the user the readings in a numeral indicator. Data are processed for its storage using a function sub-VI Write to Spreadsheet. It is performed for a maximum amount of 8 sensors, and data flow is monitored using the “Flats sequence” structure to avoid overload information in the acquisition time. Figure
Sub-VI acquisition programing block.
Graphical programming in LabVIEW 2010 uses the programming model for data flow in contrast to the programming based on text, basing its programming in the flow control model. Instead of typing complicated text lines, risking making syntactic and logistics mistakes, LabVIEW 2010 is based on the icons connections with wires using. In addition, for most users, including the advanced users it is easier to view and read the graphical programming compared with the text programming. Figure
Operation flow scheme of VIEM.
The main operation of the measurement system for gas emissions of internal combustion is to measure the gases concentration of O2, NO, CO, SO2, and CO2, for which it uses electrochemical and infrared sensors. Sensors measure the emissions that are generated from a diesel engine that runs with diesel-biodiesel blends. The measurement is performed once the combustion gases are conducted through a pipeline. The flow is firstly conducted to an oil separator and finally to a heat exchanger. Then, the gases are conducted to an exhaust manifold, where the different outputs are connected to the sensors to meter readings in real time, register and storage data provided by the signal conditioners devices and processed through the virtual instrument in the PC. There is the versatility to meter readings every 15 and 20 seconds, as well as 1 and 5 minutes, to create a database.
Other virtual instrument applications are used in monitoring stations, chemical stations, steel industries, restaurants, power stations, combined cycle, internal combustion diesel engines, gasoline, natural gas, and departments of motor testing vehicle. They represent an option for the utilization of the VIEM through its redesign and adaptation to work as a portable system.
Figure
Main window graphical user interface, tab settings.
Figure
Graphical user interface, instant tab.
Figure
Graphical user interface, testing tab.
In this work a virtual instrument based on the LabVIEW 2010 platform was developed to measure and monitor the emissions such as O2, NO, CO, SO2, and CO2 from internal combustion engines that run on gasoline, diesel, or diesel-biodiesel blends. It is an open architecture instrument and user-friendly. It is possible to modify its graphical interface and include new operations, for example, sensors that measure other emissions depending on the type of concentration and pollutant volumes, according to the user needs.
The VIEM is a useful tool for the emissions measurement that could be used by the industry sector and motor vehicles, as well as its use in the research and academics.
It is recommended to add more sensors to the VIEM to measure a wider range of gases as well as some sensor or analyzer to measure in the order of parts per million.
The authors declare that they have no competing interests.
The authors thank the National Council on Science and Technology (CONACYT) and the Engineering Institute of the Autonomous University of Baja California for its support in the development of this work.