Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N1/00—Sampling; Preparing specimens for investigation
  • G01N1/02—Devices for withdrawing samples
  • G01N1/22—Devices for withdrawing samples in the gaseous state
  • G01N1/2247—Sampling from a flowing stream of gas
  • G01N1/2252—Sampling from a flowing stream of gas in a vehicle exhaust
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
  • G01N15/06—Investigating concentration of particle suspensions
  • G01N15/0656—Investigating concentration of particle suspensions using electric, e.g. electrostatic methods or magnetic methods
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N1/00—Sampling; Preparing specimens for investigation
  • G01N1/02—Devices for withdrawing samples
  • G01N1/22—Devices for withdrawing samples in the gaseous state
  • G01N1/24—Suction devices
  • G01N2001/242—Injectors or ejectors
  • G01N2001/244—Injectors or ejectors using critical flow orifices
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
  • Y02T10/00—Road transport of goods or passengers
  • Y02T10/10—Internal combustion engine [ICE] based vehicles
  • Y02T10/12—Improving ICE efficiencies

Definitions

• the present invention relates to an apparatus for monitoring particles and especially to an apparatus as defined in the preamble of independent claim 1.
• the present invention further relates to a method for monitoring particles and more particularly to a method as defined in the preamble of independent claim 6.
• Fine particles having diameter between 1 nm and 10 ⁇ are formed in many industrial processes and combustion processes. For various reasons these fine particles are measured.
• the fine particle measurements may be conducted because of their potential health effects and also for monitoring operation of industrial processes and combustion processes, such as operation of combustion engines, especially diesel engines.
• Another reason for monitoring fine particles is the increasing use and production of nanosized particles in industrial processes. The above reasons there is need for reliable fine particle measurement equipments and methods.
• One prior art method and apparatus for measuring fine particles is described in document
• WO2009109688 Al In this prior art method clean, essentially particle free, gas is supplied into the apparatus and directed as a main flow via an inlet chamber to an ejector provided inside the apparatus.
• the clean gas is further ionized before and during supplying it into the inlet chamber.
• the ionized clean gas may be preferably fed to the ejector at a sonic or close to sonic speed.
• the ionizing of the clean gas may be carried out for example using a corona charger.
• the inlet chamber is further provided with a sample inlet arranged in fluid communication with a channel or a space comprising aerosol having fine particles.
• the clean gas flow and the ejector together cause suction to the sample inlet such that a sample aerosol flow is formed from the duct or the space to the inlet chamber.
• the sample aerosol flow is thus provided as a side flow to the ejector.
• the ionized clean gas charges the particles.
• the charged particles may be further conducted back to the duct or space containing the aerosol.
• the fine particles of the aerosol sample are thus monitored by monitoring the electrical charge carried by the electrically charged particles. Free ions may removed further be removed using an ion trap.
• industrial processes and combustion processes form usually also particles having particle diameter greater than 1 pm, or greater than 2 pm, 3 pm, 5 pm or even greater.
• the size distribution of the diesel engine exhaust particles generally shows three different modes: the nuclei mode consists of particles having a diameter of less than approximately 50 nm, the accumulation mode consists of particles having diameters between 50 nm and 1 pm and in the coarse mode the particle diameter is greater than 1 pm.
• the nuclei mode consists of particles having a diameter of less than approximately 50 nm
• the accumulation mode consists of particles having diameters between 50 nm and 1 pm
• the coarse mode is greater than 1 pm.
• a majority of the diesel engine exhaust particles is born after the exhaust gases escape from the exhaust pipe and these particles typically belong to the accumulation and nuclei mode.
• One important demand for the fine particle monitoring apparatuses is reliable operation.
• these fine particle monitoring apparatuses may be operated long time periods without need for maintenance.
• the monitoring apparatus may be operated continuously for conducting fine particle measurements in real-time, it has been surprisingly discovered that one problem of the prior art fine particle measurement method in which the sample aerosol is sucked from a duct or space containing aerosol by using ionized gas flow and an ejector, is that during start-up of measurement from high-temperature ducts such as during start-up of diesel engine emission measurement, there is a risk that vapours present in the aerosol to be measured may condense on the inner surfaces of the fine particle measurement apparatus or to the essential vicinity of the fine particle measurement apparatus inlet. Condensation will lead to unreliable measurement of the fine particles.
• the object of the present invention is to provide an apparatus and method so as to overcome the prior art disadvantages.
• the objects of the present invention are achieved with an apparatus according to the characterizing portion of claim 1, which apparatus comprises means for switching the apparatus flow on at a set temperature.
• the present invention is based on the idea of providing a method for fine particle measurement in a channel or a space.
• the particles are measured with an apparatus into which at least part of the particles in the channel or space flow.
• the flow into the measurement apparatus is allowed only above a certain set temperature.
• the set temperature should be at least 100°C and to completely avoid condensation of volatile species which may be present in the exhaust gas of a combustion engine the set temperature should be at least 200°C.
• the particle measurement is based on charging at least a fraction of particles entering the measurement apparatus and by measuring at least a fraction of the current carried by the particles.
• the particles may be charged when they enter the measurement apparatus, but in most cases it is preferred to charge the particles in the apparatus.
• Particle charging may be carried out in various ways, e.g. by dielectric barrier discharge or by corona discharge. Charging the particles by the aid of ionized, essentially clean air, as described in WO2009109688 Al is a preferable embodiment for particle charging as it removes the problem of the discharge unit soiling.
• a preferable embodiment is the one where the switch reacting to the temperature set point is a passive switch, i.e. a switch which does not require external power supply.
• a bimetallic switch is used to convert a temperature change into mechanical displacement.
• the strip consists of two strips of different metals which expand at different rates as they are heated, usually steel and copper, or in some cases brass instead of copper. The strips are joined together throughout their length by riveting, brazing or welding. The different expansions force the flat strip to bend one way if heated, and in the opposite direction if cooled below its initial temperature.
• the metal with the higher coefficient of thermal expansion is on the outer side of the curve when the strip is heated and on the inner side when cooled. It is obvious for a person skilled in the art that although the phrase states for bimetallic switch, such a switch may actually be constructed from any two materials with suitable elasticity and/or suitable thermal expansion difference.
• thermoelectric device i.e. a device with direct heat to electricity conversation.
• Such devices include, but are not limited to e.g.
• thermocouples Peltier-elements and similar.
• Such device may e.g. control a valve opening and closing a flow channel.
• the on/off function may be carried out in the apparatus inlet or at the apparatus outlet.
• the on/off switching may also be carried out by switching the clean gas flow.
• This embodiment has a further advantage when the apparatus outlet is switched on and off, because at the off-stage the essentially clean gas flows through the apparatus inlet and thus effectively protects the inlet from cold gas entrance.
• Fig. 1 shows a principle of an embodiment of the invented apparatus.
• Figure 1 shows a principle drawing of apparatus 1 for monitoring particles in a channel or a space.
• Apparatus 1 comprises means 10 for switching the apparatus flow on at a set temperature.
• Apparatus 1 may further comprise means 7 for charging the particles in apparatus 1 and means 8 for detecting the current carried by at least some of the particles.
• apparatus 1 comprises means 5 for essentially clean gas flow inlet into apparatus 1 and means 6 for ionizing 6 the essentially clean gas.
• means 10 for switching the apparatus flow on at a set temperature 10 is a bimetallic switch. In another embodiment of the invention means 10 for switching the apparatus flow on at a set temperature comprises a
• thermoelectric device The embodiment of Figure 1 is suitable to be used as a particle sensor 1 for measuring particle concentrations inside or at the exit of the exhaust pipe 2 of a combustion engine.
• Apparatus 1 is coupled to the exhaust pipe 2 with couplings 3.
• Essentially clean, ionized gas flow creates a pressure difference between the inlet 12 of apparatus 1 and the exhaust pipe 2, the pressure at the inlet 12 being lower than the pressure in the exhaust pipe 2.
• the negative pressure causes gas flow from exhaust pipe 2 into the apparatus 1.
• Ionized glean gas flow is created by feeding essentially clean gas through gas conduit 5 to the corona discharge unit 6, which ionizes the essentially clean gas.
• Apparatus 1 further comprises means 8 for measuring the electrical current carried by the charged particles. It is essential to the present invention that apparatus 1 comprises means 10 for closing the particle- containing gas flow into apparatus 1 when the temperature of apparatus 1 is such that volatile compounds in the particle-containing gas flow may condense in apparatus 1.
• the measurement point 9 for measuring the temperature is preferably selected so that the measured temperature is representative for detecting the potential condensation risk. Measurement point 9 may be selected to be in- or outside apparatus 1 or in- or outside the exhaust pipe 2.
• Means 10 for closing the particle-containing flow into apparatus 1 preferably comprise a device reacting to temperature change.
• a device may be a bimaterial switch, such as a bimetal switch, where the different thermal expansion coefficients of at least two different materials make the bimetal switch to bend as the temperature of the bimetal switch increases so that at the set temperature the bimetal switch lets the particle-containing gas enter apparatus 1.
• Means 10 for closing the particle-containing gas flow into apparatus 1 may be placed either to the upstream or downstream side of apparatus 1. When means 10 are placed on the downstream side of apparatus 1, and means 10 closes the gas flow, the essentially clean gas will flow through inlet 12 out from apparatus 1 thus effectively preventing particle-containing gas flow into apparatus 1 thus keeping apparatus 1 clean before the measurement and even cleaning the inlet 12.
• Means 10 for closing the particle-containing gas flow into apparatus 1 may also comprise a thermoelectric device where the heat at the measurement point 9 creates an electrical signal which is used to control the on/off function of means 10 for closing the particle-containing gas flow into apparatus 1. In one embodiment of the present invention, the thermoelectric device controls valve 11, which switches the essentially clean gas flow 5 on or off. When the flow of the essentially clean gas to apparatus 1 is stopped, the suction of the particle-containing gas into apparatus 1 is stopped as well.
• Apparatus 1 may be heated to increase the temperature of apparatus 1 or measurement point 9. Heating may be carried out by external means but in a preferred embodiment for using apparatus 1 for measuring combustion engine exhaust particles heating is carried out by heat transfer from the exhaust gases to apparatus 1.

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• Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Health & Medical Sciences (AREA)
• Pathology (AREA)
• General Physics & Mathematics (AREA)
• Physics & Mathematics (AREA)
• Immunology (AREA)
• Analytical Chemistry (AREA)
• Biochemistry (AREA)
• General Health & Medical Sciences (AREA)
• Molecular Biology (AREA)
• Biomedical Technology (AREA)
• Engineering & Computer Science (AREA)
• Dispersion Chemistry (AREA)
• Other Investigation Or Analysis Of Materials By Electrical Means (AREA)
• Measuring Temperature Or Quantity Of Heat (AREA)
• Sampling And Sample Adjustment (AREA)
• Devices And Processes Conducted In The Presence Of Fluids And Solid Particles (AREA)

Priority Applications (3)

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Publications (1)

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Citations (7)

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• 2010
  • 2010-02-25 FI FI20100093U patent/FIU20100093U0/fi not_active Application Discontinuation
• 2011
  • 2011-02-24 CN CN201180010972.3A patent/CN102792142B/zh not_active Expired - Fee Related
  • 2011-02-24 EA EA201290828A patent/EA024372B1/ru not_active IP Right Cessation
  • 2011-02-24 WO PCT/FI2011/000011 patent/WO2011104425A1/en active Application Filing
  • 2011-02-24 EP EP11746909.8A patent/EP2539685A4/en not_active Withdrawn

Patent Citations (7)

Non-Patent Citations (1)

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