Abstract:
A sampling device and method for use with a conduit for fluid which has at least one sampling nozzle or sample hole. The sample collected is directed to a manifold where an analysis is conducted and flow rates are measured. The sampled fluid is returned to the conduit. The Static Pressure Control System uses a vacuum pump or other device to equalize the static pressures of the sample nozzle collection manifold and the Static Pressure of the Conduit to achieve the mass-velocity and area-weighted average fluid composition and mass flow rate.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention is a sampling method and a device for obtaining real time, accurate measurements of the fluid composition and mass flow rates in conduits having uniform or non-uniform fluid composition, velocity and temperature profiles. The present invention includes the sampling of all fluids, including gases, aerosols, particulates, liquids and combinations of the same. 
         [0003]    2. Description of Related Art 
         [0004]    The problem of obtaining real-time accurate measurements of aerosol and gas in processes in conduits with uniform or non-uniform gas velocity, composition, temperature profiles, swirl and turbulence is a common one. Simply inserting a single-point gas sampling probe into a conduit of unknown characteristics only samples the fluid composition in one location which is not representative of the entire flow field in the conduit. The largest error is generally due to the velocity which can easily vary by a factor of five, the composition by a factor of three and temperature by 50% in combustion applications such as in a large coal-fired boiler, for example. In this example, measurement of the excess oxygen and carbon monoxide is a vital parameter to control combustion and improve plant efficiency. Measurement of the emission of particulates from all processes is very important for pollution control. The present invention can also be used to measure particulates as well. 
         [0005]    The applicant is aware of the following references which relate to sampling and measurement of fluid flowing in a conduit. 
         [0000]    
       
         
               
               
               
             
           
               
                   
                   
               
               
                   
                 Pat. No. 
                 Inventor(s) 
               
               
                   
                   
               
             
             
               
                   
                 2,523,721 
                 Russell et al 
               
               
                   
                 2,614,423 
                 Carbone 
               
               
                   
                 4,115,229 
                 Capone 
               
               
                   
                 4,290,315 
                 Grönberg 
               
               
                   
                 6,164,142 
                 Dimeff 
               
               
                   
                 6,642,720 
                 Maylotte et al 
               
               
                   
                 6,843,104 
                 Busch 
               
               
                   
                 6,862,915 
                 Staphanos et al 
               
               
                   
                 2003/018,586 
                 Orieskie et al 
               
               
                   
                   
               
             
          
         
       
     
         [0006]    Russell et al disclose an apparatus for analyzing gaseous fuel before it is delivered into the heating chamber. A sample is collected and burned under controlled conditions. The combustion products are analyzed. 
         [0007]    Carbone discloses the measurement of fluid flow through a conduit across the cross-sectional area of the conduit. The mean total differential between the impact pressure and the static pressure actuates a measuring and recording metering mechanism. 
         [0008]    Capone discloses a gas analyzer for analysis of explosive mixtures. A correction loop flow circuit is used to bring a sample past a gas sensing element and back to a common inlet-outlet chamber. 
         [0009]    Gröberg discloses an apparatus for determining the differential pressure and the volumetric fluid flow in a conduit. There is a pipe loop provided with a series of ports for sensing pressure. 
         [0010]    Dimeff discloses an air flow measuring device which present a restricted orifice to the air flow and measure the pressure drop to determine the flow rate. 
         [0011]    Maylotte et al disclose a wireless sensor assembly for measuring selected properties of a gas stream. 
         [0012]    Busch discloses a system for measuring gaseous constituents in a flowing gas mixture. A mixing device in a flow homogenizes the gas mixture before it is detected by the sensor which detects individual gas constituents. 
         [0013]    Staphanoes et al disclose a combustion gas analyzer for measuring the concentration of a gas constituent in an exhaust gas stream. 
         [0014]    Orieskie et al disclose a process flow device which has a self-averaging orifice plate. The volumetric rate of flow is measured by a differential pressure process. 
         [0015]    None of these references disclose a method of using one or more sampling nozzles which direct the fluid sample flow into a manifold wherein the flow rate and composition of the conduit fluid may be analyzed from a small sample stream of fluid having the same properties of the fluid in the conduit, nor a method in which the sample streams are collected independent of each other and collect a sample that represents the product of the fluid composition and the conduit mass flow rate at each nozzle or hole in the probe. 
       SUMMARY OF THE INVENTION 
       [0016]    It is an object of the present invention to provide a multi-point self-averaging mass velocity and flow area-weighted sampling method for measurement of fluid composition in conduits and the mass flow rate in the conduit. 
         [0017]    In accordance with the teachings of the present invention there is disclosed a sampling device for measuring fluid and particulate composition and flow rates in a conduit having a uniform or a non-uniform composition, velocity, and temperature profiles. The sampling device has a sampling loop having at least one probe mounted on a wall of the conduit with at least one nozzle mounted on the at least one probe and extending outwardly from the at least one probe. At least one sampling nozzle is oriented within the conduit facing into the flow wherein the pressure in the conduit forces a sample through the at least one nozzle into a sample collection manifold connected to the at least one sampling nozzle. Means are provided to adjust the static pressure within the sample collection manifold to be equal to the static pressure within the conduit. A composition measurement chamber is connected to the sample collection manifold. A fluid composition analyzer is connected to the composition measurement chamber wherein a sample is analyzed for each desired constituent, thereby providing a fluid composition representative of the flow in the conduit. A mass flow meter is connected to the composition measurement chamber wherein the flow rate in the composition measurement chamber is measured. Further, the mass flow meter is connected to the conduit through a static pressure port. The product of the flow rate times the fluid composition for each desired constituent provides a mass velocity weighted fluid composition. 
         [0018]    Further in accordance with the teachings of the present invention, there is disclosed a sampling device for measuring fluid composition and flow rates in a conduit having a uniform or a non-uniform composition, velocity, and temperature profiles. The sampling device has a plurality of sampling nozzles disposed across a cross-sectional area of the conduit. Each sampling nozzle communicates with a sample collection manifold. A pressure adjusting means is in communication with the sample collection manifold. A composition measurement chamber is connected to the sample collection manifold. A gas analyzer is connected to the composition measurement chamber. A means for measuring flow rate is connected to the sample collection manifold. In this manner fluid from the conduit is collected in the sampling nozzles and directed into the sample collection manifold. The static pressure in the sample collection manifold is adjusted to be equal to the static pressure in the conduit. The fluid in the composition measurement chamber is analyzed for composition and for flow rate. 
         [0019]    Still further in accordance with the teachings of the present invention, there is disclosed a method for taking a sample of a fluid flowing in a conduit, the fluid having a uniform or a non-uniform fluid composition, velocity, and temperature profile. At least one probe is mounted in the conduit. At least one sampling nozzle is mounted on the at least one probe and extends outwardly from said probe. The at least one sampling nozzle is placed in the conduit facing into the flow at a sampling point, thereby generating a flow of fluid having a mass velocity within the at least one sampling nozzle. Said flow of fluid is linearly proportional to a mass velocity in the conduit at the sampling point. The flow of fluid is directed into a sample collection manifold wherein a sample stream at a static pressure is formed having gas composition properties the same as the fluid in the conduit. The static pressure within the sample collection manifold is adjusted to be equal to the static pressure in the conduit. The flow of fluid is directed from the sample collection manifold into a composition measurement chamber. The composition of the fluid in the composition measurement chamber is measured using a gas analyzer. The flow rate of the fluid in the composition measurement chamber is measured using a mass flow rate meter. The fluid from the flow rate meter is directed back into the conduit through a static pressure point. 
         [0020]    These and other objects of the present invention will become apparent from a reading of the following specification taken in conjunction with the enclosed drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]      FIG. 1  is a diagram of the Sample Loop of the present invention. 
           [0022]      FIG. 2  is a top plan view of the Sampling Probe. 
           [0023]      FIG. 3  is a cross-sectional view taken along the lines  3 - 3  of  FIG. 2 . 
           [0024]      FIG. 4  is a cross-sectional view taken along the lines  4 - 4  of  FIG. 3 . 
           [0025]      FIG. 5  is a graph showing the Operating Characteristics of the present invention. 
           [0026]      FIG. 6  is a graph showing Pitch and Yaw Data. 
       
    
    
     PRINCIPLE OF OPERATION 
       [0027]      FIG. 1  shows a simplified drawing of the preferred embodiment of a sampling loop for a single sampling probe assembly. Several such probe assemblies are required for large conduits. Each probe has sample nozzles located at the centroid of equal flow areas in the conduit  10 . The number of sample nozzles and probes is determined by the severity of the non-uniform properties of the velocity, temperature and fluid composition profiles. The Sampling Probe  12  consists of one or more sample nozzles  14  connected to a Sample Nozzle Collection Manifold  16  in which the sampled streams mix and flow through the Particulate Analyzer  38  (if desired), the Particulate Filter  18  (if required), the Fluid Composition Measurement Chamber  20 , Fluid Analyzers  32 ,  34  any other measurement devices, Mass Flow Meter  22  and Vacuum Pump  24  or equivalent device. The Sample Nozzle Collection Manifold  16  has Static Pressure Ports  26  mounted flush with the inside wall. The average Conduit Static Pressure Ports  28  are located on the surface of the outer wall of the sampling probe. The preferred embodiment takes advantage of the pressure distribution over a circular tube in cross-flow for which the Conduit Static Pressure occurs at an angle of about 35° on both sides of the flow stagnation point on a circular cylinder. The Conduit Static Pressure Ports  28  are used to obtain the average conduit static pressure. This method gives a very good average static pressure in the presence of swirl and non-axial fluid velocity components in the duct. 
         [0028]    A simplified drawing of the internal structure of the Sampling Probe  12  is shown in  FIG. 2  for a two-nozzle sampling system. The basic concept is to use the dynamic pressure of the fluid in the conduit to force a mass-velocity proportional sample flow into each nozzle. The sample stream from each nozzle is collected together and mixed in the Sample Nozzle Collection Manifold  16  and then flows into the Sample Loop depicted in  FIG. 1 . The following terms are applicable to  FIG. 2 .
       M=M A +M B =total mass flow of probe, nozzles A &amp; B   M A =ρ A V A2 ×A=mass flow through nozzle A   M B =ρ B V B2 ×A=mass flow through nozzle B   V A2  is sample nozzle velocity at nozzle A   V B2  is sample nozzle velocity at nozzle B       
 
         [0000]    
       
         
           
             
               A 
               N 
             
             = 
             
               
                 area 
                  
                 
                     
                 
                  
                 of 
                  
                 
                     
                 
                  
                 each 
                  
                 
                     
                 
                  
                 flow 
                  
                 
                     
                 
                  
                 nozzle 
               
               = 
               
                 
                   π 
                    
                   
                       
                   
                    
                   
                     d 
                     2 
                   
                 
                 4 
               
             
           
         
       
       
         
           
             d=sample nozzle internal diameter 
             D=I.D. of sample collection manifold D&gt;&gt;d 
             θ=static pressure port angle from stagnation point on circular cylinder 
             ρ A =fluid density at nozzle A 
             ρ B =fluid density at nozzle B 
             C A , C B =fluid concentrations at nozzles A, B 
             T A , T B =fluid temperatures at nozzles A, B 
             P SA1 =conduit stack pressure at nozzle A 
             P SB1 =conduit stack pressure at nozzle B 
             P sa2 =pressure at entrance to nozzle A 
             P SB2 =pressure at entrance to nozzle B 
             P SM =static pressure of sample nozzle collection manifold 
             g c =32.15 ft/sec 2    
           
         
       
     
         [0047]      FIG. 3  is a drawing, (including definitions of all the variables) for a two-nozzle sample probe. Applying Bernoulli&#39;s Equation, the total pressure of the fluid streamlines at Nozzle A is: 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       P 
                       
                         
                           SA 
                            
                           
                               
                           
                            
                           1 
                         
                          
                         
                             
                         
                       
                     
                     + 
                     
                       
                         1 
                         2 
                       
                        
                       
                         
                           
                             ρ 
                             A 
                           
                            
                           
                             V 
                             
                               A 
                                
                               
                                   
                               
                                
                               1 
                             
                             2 
                           
                         
                         
                           g 
                           c 
                         
                       
                     
                   
                   = 
                   
                     
                       P 
                       
                         SA 
                          
                         
                             
                         
                          
                         2 
                       
                     
                     + 
                     
                       
                         1 
                         2 
                       
                        
                       
                         
                           
                             ρ 
                             A 
                           
                            
                           
                             V 
                             
                               A 
                                
                               
                                   
                               
                                
                               2 
                             
                             2 
                           
                         
                         
                           g 
                           c 
                         
                       
                     
                   
                 
               
               
                 
                   Equation 
                    
                   
                       
                   
                    
                   1 
                 
               
             
           
         
       
     
         [0000]    The available pressure difference to drive the sample flow into the sample nozzle and sample manifold is: 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       P 
                       
                         SA 
                          
                         
                             
                         
                          
                         2 
                       
                     
                     - 
                     
                       P 
                       
                         SA 
                          
                         
                             
                         
                          
                         1 
                       
                     
                   
                   = 
                   
                     
                       
                         1 
                         2 
                       
                        
                       
                         
                           
                             ρ 
                             A 
                           
                            
                           
                             V 
                             
                               A 
                                
                               
                                   
                               
                                
                               1 
                             
                             2 
                           
                         
                         
                           g 
                           c 
                         
                       
                     
                     - 
                     
                       
                         1 
                         2 
                       
                        
                       
                         
                           
                             ρ 
                             
                               A 
                                
                               
                                   
                               
                             
                           
                            
                           
                             V 
                             
                               A 
                                
                               
                                   
                               
                                
                               2 
                             
                             2 
                           
                         
                         
                           g 
                           c 
                         
                       
                     
                   
                 
               
               
                 
                   Equation 
                    
                   
                       
                   
                    
                   2 
                 
               
             
           
         
       
     
         [0000]    If V A2 =0 then no flow can occur and the device functions as a Pitot Tube and responds to the average pressure in the Sample Nozzle Collection Manifold  16 . 
         [0048]    For sampling purposes, it is desired that the nozzle velocity V A2  be proportional to the local conduit mass velocity V A1 . The sample flow through the nozzles and into the Sample Nozzle Collection Manifold  16  is dependent on the pressure of the Sample Nozzle Collection Manifold Static Pressure (P SM ). Therefore, the following equation applies: 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       P 
                       
                         SA 
                          
                         
                             
                         
                          
                         2 
                       
                     
                     - 
                     
                       P 
                       SM 
                     
                   
                   = 
                   
                     
                       
                         1 
                         2 
                       
                        
                       
                         
                           ρ 
                            
                           
                               
                           
                            
                           
                             V 
                             
                               A 
                                
                               
                                   
                               
                                
                               1 
                             
                             2 
                           
                         
                         
                           g 
                           c 
                         
                       
                     
                     - 
                     
                       
                         1 
                         2 
                       
                        
                       
                         
                           ρ 
                            
                           
                               
                           
                            
                           
                             V 
                             
                               A 
                                
                               
                                   
                               
                                
                               2 
                             
                             2 
                           
                         
                         
                           g 
                           c 
                         
                       
                     
                   
                 
               
               
                 
                   Equation 
                    
                   
                       
                   
                    
                   3 
                 
               
             
           
         
       
     
         [0049]    The maximum sample flow rate occurs when the sample loop is “short-circuited”. If P SA2 −P SM  is forced to be equal to 0 then it is obvious that V A1 =V A2  and the system is a self-driven linearly proportional sampler; however, there is a pressure drop caused by the sample nozzle. This pressure drop ΔP n  is shown in Equation 4: 
         [0000]    
       
         
           
             
               
                 
                   
                     Δ 
                      
                     
                         
                     
                      
                     
                       P 
                       n 
                     
                   
                   = 
                   
                     
                       C 
                       
                         D 
                          
                         
                             
                         
                       
                     
                     ( 
                     
                       
                         1 
                         2 
                       
                        
                       
                         
                           
                             ρ 
                             A 
                           
                            
                           
                             V 
                             
                               A 
                                
                               
                                   
                               
                                
                               2 
                             
                             2 
                           
                         
                         
                           g 
                           c 
                         
                       
                     
                     ) 
                   
                 
               
               
                 
                   Equation 
                    
                   
                       
                   
                    
                   4 
                 
               
             
           
         
       
     
         [0000]    where C D  is the nozzle pressure drop coefficient. 
         [0050]    This pressure drop must be accounted for by subtracting it from the right-hand side of Equation 3 as shown below: 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       
                         
                           
                             
                               P 
                               
                                 SA 
                                  
                                 
                                     
                                 
                                  
                                 2 
                               
                             
                             - 
                             
                               P 
                               SM 
                             
                           
                           = 
                             
                            
                           
                             
                               
                                 1 
                                 2 
                               
                                
                               
                                 
                                   
                                     ρ 
                                     A 
                                   
                                    
                                   
                                     V 
                                     
                                       A 
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                                       1 
                                     
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                                   g 
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                             - 
                             
                               
                                 
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                                   A 
                                 
                                  
                                 
                                   V 
                                   
                                     A 
                                      
                                     
                                         
                                     
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                                     2 
                                   
                                   2 
                                 
                               
                               
                                 g 
                                 c 
                               
                             
                             - 
                             
                               
                                 C 
                                 D 
                               
                                
                               
                                 1 
                                 2 
                               
                                
                               
                                 
                                   
                                     ρ 
                                     A 
                                   
                                    
                                   
                                     V 
                                     
                                       A 
                                        
                                       
                                           
                                       
                                        
                                       1 
                                     
                                     2 
                                   
                                 
                                 
                                   g 
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                           = 
                             
                            
                           
                             
                               
                                 1 
                                 2 
                               
                                
                               
                                 
                                   
                                     ρ 
                                     A 
                                   
                                    
                                   
                                     V 
                                     
                                       
                                         A 
                                          
                                         
                                             
                                         
                                          
                                         1 
                                       
                                        
                                       
                                           
                                       
                                     
                                     2 
                                   
                                 
                                 
                                   g 
                                   c 
                                 
                               
                             
                             - 
                             
                               
                                 ( 
                                 
                                   1 
                                   + 
                                   
                                     C 
                                     D 
                                   
                                 
                                 ) 
                               
                                
                               
                                 ( 
                                 
                                   
                                     1 
                                     2 
                                   
                                    
                                   
                                     
                                       
                                         ρ 
                                         A 
                                       
                                        
                                       
                                         V 
                                         
                                           A 
                                            
                                           
                                               
                                           
                                            
                                           2 
                                         
                                         2 
                                       
                                     
                                     
                                       g 
                                       c 
                                     
                                   
                                 
                                 ) 
                               
                             
                           
                         
                       
                     
                   
                    
                   
                     
 
                   
                    
                   
                     
                       
                         If 
                          
                         
                             
                         
                          
                         we 
                          
                         
                             
                         
                          
                         set 
                          
                         
                             
                         
                          
                         
                           P 
                           
                             SA 
                              
                             
                                 
                             
                              
                             2 
                           
                         
                       
                       - 
                       
                         P 
                         SM 
                       
                     
                     = 
                     0 
                   
                    
                   
                     
 
                   
                    
                   
                     
                       Then 
                        
                       
                           
                       
                        
                       
                         1 
                         2 
                       
                        
                       
                         
                           
                             ρ 
                             a 
                           
                            
                           
                             V 
                             
                               A 
                                
                               
                                   
                               
                                
                               1 
                             
                             2 
                           
                         
                         
                           g 
                           c 
                         
                       
                     
                     = 
                     
                       
                         ( 
                         
                           1 
                           + 
                           
                             C 
                             D 
                           
                         
                         ) 
                       
                        
                       
                         1 
                         2 
                       
                        
                       
                         
                           
                             ρ 
                             A 
                           
                            
                           
                             V 
                             
                               A 
                                
                               
                                   
                               
                                
                               2 
                             
                             2 
                           
                         
                         
                           g 
                           c 
                         
                       
                     
                   
                 
               
               
                 
                   Equation 
                    
                   
                       
                   
                    
                   5 
                 
               
             
             
               
                 
                   
                     V 
                     
                       A 
                        
                       
                           
                       
                        
                       2 
                     
                   
                   = 
                   
                     
                       V 
                       
                         A 
                          
                         
                             
                         
                          
                         1 
                       
                     
                     
                       
                         1 
                         + 
                         
                           C 
                           D 
                         
                       
                     
                   
                 
               
               
                 
                   Equation 
                    
                   
                       
                   
                    
                   6 
                 
               
             
           
         
       
     
         [0051]    Equation 6 demonstrates that the method provides a sample nozzle velocity directly proportional to the local conduit velocity. Therefore, if the static pressure in the Sample Nozzle Collection Manifold is maintained equal to the Conduit Static Pressure the sample nozzle velocity V A2  will be proportional to the local conduit velocity (V A1 ). In practice V A2  is about 90% of V A1 , for gases, for example. 
         [0052]    Additional sample loop pressure drop caused by friction, bends, fittings, valves, Particulate Filter, Gas Composition Analyzers, Mass Flow Meter and will greatly affect the performance of the invention as the Sample Nozzle Manifold Static Pressure will rise above the conduit static pressure and cause the sample rate to decrease; and the nozzle velocity will not be proportional to the local conduit velocity, therefore, not meeting the desired average fluid concentration nor total duct mass flow rate. The solution to this problem and the essence of the present invention is to use a Vacuum Pump  24  or other suitable device to offset any sample loop pressure drops in order to obtain the same result as given in Equation 6. The other devices may be a jet eductor, a fan, a blower or other devices known to persons skilled in the art. By meeting the criteria the operators of each nozzle is independent of the other nozzles, which is a required condition for mass-velocity weighted composition measurements. 
         [0053]    This is accomplished by using an Active Control System  30  in which the Differential Pressure Transmitter  42  measures the difference between the Sample Nozzle Collection Manifold Static Pressure Port  26  and the Conduit Static Pressure Ports  28  and controls the Vacuum Pump  24  (or other device) to increase or decrease the Sample Nozzle Collection Manifold Static pressure whereby offsetting any pressure drop in the Sample Loop. 
         [0054]    Using Equation 5 and incorporating any additional sample loop pressure drop, ΔP, it can be shown that this invention solves the pressure drop interference problem: 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       P 
                       
                         SA 
                          
                         
                             
                         
                          
                         2 
                       
                     
                     - 
                     
                       P 
                       SM 
                     
                   
                   = 
                   
                     
                       
                         1 
                         2 
                       
                        
                       
                         
                           ρ 
                            
                           
                               
                           
                            
                           
                             V 
                             
                               A 
                                
                               
                                   
                               
                                
                               1 
                             
                             2 
                           
                         
                         
                           g 
                           c 
                         
                       
                     
                     - 
                     
                       
                         1 
                         2 
                       
                        
                       
                         
                           ρ 
                            
                           
                               
                           
                            
                           
                             V 
                             
                               A 
                                
                               
                                   
                               
                                
                               2 
                             
                             2 
                           
                         
                         
                           g 
                           c 
                         
                       
                        
                       
                         ( 
                         
                           1 
                           + 
                           
                             C 
                             D 
                           
                         
                         ) 
                       
                     
                     - 
                     
                       Δ 
                        
                       
                           
                       
                        
                       P 
                     
                   
                 
               
               
                 
                   Equation 
                    
                   
                       
                   
                    
                   7 
                 
               
             
           
         
       
     
         [0000]    ΔP=P SM −P SA1 =The difference between the Sample Nozzle Collection Static Pressure Manifold and the Conduit Static Pressure, as defined previously. 
       Then: 
       [0055]    
       
         
           
             
               
                 P 
                 
                   SA 
                    
                   
                       
                   
                    
                   2 
                 
               
               - 
               
                 P 
                 SM 
               
             
             = 
             
               
                 
                   1 
                   2 
                 
                  
                 
                   
                     ρ 
                      
                     
                         
                     
                      
                     
                       V 
                       
                         A 
                          
                         
                             
                         
                          
                         1 
                       
                       2 
                     
                   
                   
                     g 
                     c 
                   
                 
               
               - 
               
                 
                   1 
                   2 
                 
                  
                 
                   
                     ρ 
                      
                     
                         
                     
                      
                     
                       V 
                       
                         A 
                          
                         
                             
                         
                          
                         2 
                       
                       2 
                     
                   
                   
                     g 
                     c 
                   
                 
                  
                 
                   ( 
                   
                     1 
                     + 
                     
                       C 
                       D 
                     
                   
                   ) 
                 
               
               - 
               
                 P 
                 SM 
               
               + 
               
                 P 
                 
                   SA 
                    
                   
                       
                   
                    
                   1 
                 
               
             
           
         
       
     
         [0000]    So that: 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       P 
                       
                         SA 
                          
                         
                             
                         
                          
                         2 
                       
                     
                     - 
                     
                       P 
                       SM 
                     
                   
                   = 
                   
                     
                       
                         1 
                         2 
                       
                        
                       
                         
                           ρ 
                            
                           
                               
                           
                            
                           
                             V 
                             
                               A 
                                
                               
                                   
                               
                                
                               1 
                             
                             2 
                           
                         
                         
                           g 
                           c 
                         
                       
                     
                     - 
                     
                       
                         1 
                         2 
                       
                        
                       
                         
                           ρ 
                            
                           
                               
                           
                            
                           
                             V 
                             
                               A 
                                
                               
                                   
                               
                                
                               2 
                             
                             2 
                           
                            
                           
                             ( 
                             
                               1 
                               + 
                               
                                 C 
                                 D 
                               
                             
                             ) 
                           
                         
                         
                           g 
                           c 
                         
                       
                     
                   
                 
               
               
                 
                   Equation 
                    
                   
                       
                   
                    
                   8 
                 
               
             
           
         
       
     
         [0056]    This gives the same result as Equation 5 which verifies that the Active Static Pressure Controller feature is essential to obtain a truly mass-velocity weighted fluid composition and mass flow rate measurement, and is the preferred embodiment of this invention. 
       Operating Characteristics: 
       [0057]      FIG. 5  shows the operating characteristics of the present invention. The ordinate P SA2 −P SM  is the difference between the pressure at the entrance to Nozzle A and the Sample Collection Manifold Static Pressure (P SM ). The abscissa (V A2 ) is the velocity in the sample nozzle.  FIG. 5  is a plot of Equation 8 previously described. 
         [0000]    There are four operating modes for the present invention: 
         [0058]    1) Mass-Velocity Proportional Sampling Mode 
         [0059]    2) Under-Sampling Mode 
         [0060]    3) Over-Sampling Mode 
         [0061]    4) Pitot Tube Velocity Mode
       A) Mass-Velocity Proportional Sampling Mode: This mode uses an Active Control System to maintain the Sample Manifold Static Pressure equal to the Conduit Static Pressure by means of a vacuum pump  24  or other device. The operating point for this Mode is labeled A on  FIG. 5 . This insures that there is no flow circulation between sample nozzles  14 , and that the various sample flows are independent of each other. The fluid composition is mass-velocity weighted at each sample nozzle and the mixture of all the sample inputs collected in the Sample Nozzle Collection Manifold  16  represents the true mass-velocity and conduit flow area-weighted sample for all fluid constituents. For gases, the velocity in the sample nozzles is about 90% of the local conduit velocity and the total sample flow is about 90% of the ideal sample flow. The velocity ratio can be experimentally determined so that knowing this ratio, the flow area of the conduit, the sample flow rate and the total sample nozzle area, the total mass-flow rate of the conduit can be accurately obtained over the entire range of operations.
           The sample nozzles in the preferred embodiment are insensitive to swirl and non-axial duct velocity components because of the nozzle design ( FIG. 6 ).   
               
 
         [0000]    
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Ref. 
                   
                   
                   
                   
               
               
                 Velocity 
                 Sample 
                   
                 Normalized 
                 Cosine 
               
               
                 (SFPM) 
                 (SCFM) 
                 Pitch (°) 
                 Sample 
                 Response 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 3854 
                 2.766 
                 −20 
                 0.932 
                 0.940 
               
               
                 3812 
                 2.8613 
                 −15 
                 0.964 
                 0.966 
               
               
                 3825 
                 2.9403 
                 −10 
                 0.991 
                 0.985 
               
               
                 3826 
                 2.978 
                 −5 
                 1.003 
                 0.996 
               
               
                 3823 
                 2.9683 
                 0 
                 1.000 
                 1.000 
               
               
                 3812 
                 2.954 
                 5 
                 0.995 
                 0.996 
               
               
                 3810 
                 2.932 
                 10 
                 0.988 
                 0.985 
               
               
                 3804 
                 2.854 
                 15 
                 0.961 
                 0.966 
               
               
                 3813 
                 2.701 
                 20 
                 0.910 
                 0.940 
               
               
                 1576 
                 1.0777 
                 −20 
                 0.951 
                 0.940 
               
               
                 1570 
                 1.0967 
                 −15 
                 0.968 
                 0.966 
               
               
                 1575 
                 1.1307 
                 −10 
                 0.998 
                 0.985 
               
               
                 1580 
                 1.137 
                 −5 
                 1.003 
                 0.996 
               
               
                 1570.5 
                 1.13343 
                 0 
                 1.000 
                 1.000 
               
               
                 1570 
                 1.131 
                 5 
                 0.998 
                 0.996 
               
               
                 1577 
                 1.1142 
                 10 
                 0.983 
                 0.985 
               
               
                 1570 
                 1.08233 
                 15 
                 0.955 
                 0.966 
               
               
                 1570 
                 1.02045 
                 20 
                 0.900 
                 0.940 
               
               
                   
               
             
          
         
       
       
         
           
             
               
                  The essential feature of this preferred embodiment is that pressure drops created by the Fluid Composition Analyzers  32 ,  34 , Particulate Filters  18 , Sample Mass Flow meters  22  and any other pressure drop causing devices in the sample loop  10  can be canceled out provided that the Sample Manifold Static Pressure and the Conduit Static Pressure are equal to each other. This is the preferred embodiment for all situations for clean or dirty fluids. 
               
             
             B) Under-Sampling Mode: The operating range, labeled B on  FIG. 5 , is between the Pitot Tube Velocity Mode, labeled D on  FIG. 5 , and the Mass Velocity Proportional Sampling Mode, labeled A in  FIG. 5 . The Sample Nozzle Collection Manifold static pressure is higher than the Conduit Static Pressure such that the sample rate is lower and incorrect compared to the Mass-Velocity Proportional Mode. Lower velocity areas of the conduit will not be sampled properly, and flow circulation will occur between the nozzles, such that the sample flows from each nozzle are not independent of each other which is a necessity of this invention. This Mode is affected by pressure drops in the sample loop. This mode can only be used for certain applications in which the sample loop pressure drops are very small and constant over time. 
             C) Over-Sampling Mode: In this mode the Sample Manifold Static Pressure is much less than the Conduit Static Pressure, such that a larger sample flow rate is achieved due to a vacuum pump  24  or other device. There is a special condition in which the Active Control System can operate the sample system at an average isokinetic condition (nozzle velocity equals local conduit velocity) labeled C on  FIG. 5 , but not all sample nozzles will be isokinetic nor independent of each other. The samples are not mass-weighted. 
             D) Pitot Tube Velocity Mode: This mode is labeled as D on  FIG. 5 . The Sample Nozzle Collection Manifold  16  is shut-off so the sample flow rate is zero. This mode operates as a multi-point Pitot Tube which the average differential pressure minus the Conduit Static Pressure. These devices do not give the accurate average velocity reading due to internal circulation between the sample nozzles unless the velocity profile is very uniform. This mode is not a sampling mode and is included in this disclosure only to show the complete operating characteristics of the present invention method and devices. 
           
         
       
     
       Mass Flow Measurement Method: 
       [0067]    The total mass flow rate for the conduit can be determined from the mass flow rate of one or more sampling assemblies that are appropriately located in the conduit and use the preferred embodiment. The ratio of the sample nozzle velocity to the conduit velocity is a function of the sample nozzle pressure drop coefficient (C D ) as shown in Equation 6. The total mass flow of the conduit for one sampling assembly as depicted for the two-nozzle sampling example of  FIG. 3  is: 
         [0000]    
       
         
           
             
               
                 
                   
                     M 
                     T 
                   
                   = 
                   
                     
                       ( 
                       
                         
                           1 
                           + 
                           
                             C 
                             D 
                           
                         
                       
                       ) 
                     
                      
                     
                       ( 
                       
                         
                           M 
                           A 
                         
                         + 
                         
                           M 
                           B 
                         
                       
                       ) 
                     
                     × 
                     
                       
                         A 
                         C 
                       
                       
                         2 
                          
                         
                           A 
                           N 
                         
                       
                     
                   
                 
               
               
                 
                   Equation 
                    
                   
                       
                   
                    
                   9 
                 
               
             
           
         
       
     
       Where: 
     M T =Total Sample Mass Flow Rate 
       [0068]    C D =is experimentally determined nozzle pressure drop coefficient
 
M A =Mass Flow Rate through Nozzle A
 
M B =Mass Flow Rate through Nozzle B
 
       A C =Flow Area of Conduit 
       [0069]    A N =Area of each nozzle 
       Effect of Non-Axial Conduit Velocity: 
       [0070]    Several nozzle designs have been tested to find the best shape to produce the largest sample flow rate for the lowest nozzle pressure drop and have good pitch and yaw behavior. The ideal response is for the nozzle to have a “cosine” response to pitch and yaw angles of the velocity vector. Many nozzle shapes have been tested including rounded inlets, sharp-edge nozzle inlets, inside and/or outside tapered nozzle inlets and holes in the probe instead of nozzles. The preferred embodiment is a constant diameter nozzle having a rounded inlet at the nozzle tip protruding into the flow stream. The preferred embodiment is a good compromise between a having high sample nozzle velocity and pitch and yaw characteristics and dirt accumulations. When a protruding nozzle is used, it has been found that by having the nozzle tip extend from the probe surface one or two diameters better pitch and yaw performance are obtained. This is due to the fact that the pressure distribution around a circular tube probe structure changes very rapidly with angle, and when a nozzle with an extended tip is used, it is less affected by the probe structure. 
         [0071]      FIG. 6  shows the pitch and yaw response data of the preferred embodiment compared to the ideal cosine response. This response is much better than most other fluid sampling devices known by the inventor. 
         [0072]    The only accurate sampling mode is the Mass-Velocity Proportional Sampling Mode as described above although the present invention includes other modes of operation. It produces an independent sample rate at each nozzle, compensates for all pressure drops in the sample loop, has good off-axis velocity response characteristics and pneumatically performs the provides a mathematically correct fluid composition equations for the average fluid composition and the conduit mass flow rate over a wide range of fluid velocities, fluid composition, temperature, pressure, and dirty fluids. 
       DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0073]    A diagram showing the system of the present invention is shown in  FIG. 1 . The present invention is a mass-velocity weighted sampling probe and is used to obtain truly representative samples for the analyzers. The present invention pneumatically performs the mass-velocity and area averaging according to the following equation which is the correct definition of the True Concentration Average. 
         [0000]    
       
         
           
             
               
                 C 
                 i 
               
               _ 
             
             = 
             
               
                 ∫ 
                 
                   ∫ 
                   
                     
                       ρ 
                        
                       
                         ( 
                         
                           x 
                           , 
                           y 
                         
                         ) 
                       
                     
                      
                     
                       V 
                        
                       
                         ( 
                         
                           x 
                           , 
                           y 
                         
                         ) 
                       
                     
                      
                     
                       
                         C 
                          
                         
                           ( 
                           
                             x 
                             , 
                             y 
                           
                           ) 
                         
                       
                       i 
                     
                      
                     
                        
                       x 
                     
                      
                     
                        
                       y 
                     
                   
                 
               
               
                 ∫ 
                 
                   ∫ 
                   
                     
                       ρ 
                        
                       
                         ( 
                         
                           x 
                           , 
                           y 
                         
                         ) 
                       
                     
                      
                     
                       V 
                        
                       
                         ( 
                         
                           x 
                           , 
                           y 
                         
                         ) 
                       
                     
                      
                     
                        
                       x 
                     
                      
                     
                        
                       y 
                     
                   
                 
               
             
           
         
       
     
       Where: 
       [0074]      C   i  is the mass-velocity and area average concentration in the conduit of fluid component i, ρ(x, y) is the fluid density, V(x, y) is the fluid velocity and C(x, y), is the concentration of Component i. 
         [0075]    As shown in  FIG. 1 , a probe  12  is installed which extends perpendicularly into the conduit, vent, duct or stack  10  in which the measurements are to be taken. Preferably, a plurality of probes  12  are used to effectively sample over the area of the conduit. Each probe  12  is located at the centroid of equal flow area locations within the conduit. At least one, and preferably, a plurality of Sampling Nozzles  14  are mounted on each probe  12 . The nozzles extend outwardly from the probe. The Sampling Nozzles  14  are oriented so that the flow of fluid within the conduit is directed into the opening in the nozzle. This opening communicates with the Sample Nozzle Collection Manifold  16 . The number of Probes  12  and Sampling Nozzles  14  is determined by extent of the non-uniform properties of the velocity, temperature and fluid concentration profile in the conduit. Preferably, the plurality of probes and nozzles are arranged on a cross-sectional area of the conduit. 
         [0076]    Thus, there is a least one Sampling Nozzle  14  placed at equal areas within the conduit facing the flow, each of which has a mass velocity that is linearly proportional to the local mass velocity of the fluid in the conduit such that the resulting flow rate from all the nozzles represents a truly representative sample of the aerosol and gases in the conduit. This sample flows through the Particulate Analyzer  38  (if used) the Particulate Filter  18  (if used) the Fluid Composition Measurement Chamber  20 , the In-Line Mass Flow Meter  22 , through the Vacuum Pump  24  (or other suitable device) and is exhausted back to the Conduit  10 , thus completing the Sample Loop. 
         [0077]    The mass rate of the Sample Loop is proportional to the mass flow rate for the area of the conduit being measured. One or more such multi-point sampling probe assemblies may be used to obtain the average fluid concentration and the mass flow rate of the entire conduit. The sum of the product of the mass flow rate and the concentration fluid constituent for each sampling probe assemblies divided by the number of sampling probe assemblies provides the mass-velocity weighted average concentration for each constituent that is being measured. The average mass flow rate of all the systems times the total area of the conduit times the nozzle velocity compared to the local conduit velocity provides an accurate and repeatable mass flow rate in the conduit as previously described in the Principle of Operation Section of the disclosure. 
         [0078]    It is well known that elbows, obstructions and area changes in conduits cause swirl, turbulences and non-axial fluid velocity vectors. The shape of the sampling nozzles  14  for the preferred embodiment provide a good response to pitch and yaw angles of the velocity in the conduit compared to the ideal cosine response  FIG. 6 . 
         [0079]    An important application for the present invention is for measuring and controlling the combustion process in fossil-fueled power plants. Accurate measurement of the excess Oxygen and Carbon Monoxide are required to optimize the efficiency. It is well known that fly ash is a major problem in coal-fired power plants. For such dirty applications, the preferred embodiment includes a Particulate Filter  18  in the Sample Loop. The filter cleans the sample fluid before it enters the Fluid Composition Measurement Chamber  20  and the Mass Flow Meter  22 . All Sample Loop Pressure Drops are canceled by the Active Static Pressure Control  30  Embodiment. 
         [0080]    The concentration of particulates in the Conduit  10  is measured by the Particulate Analyzer  38  which is placed in series with the Sample Nozzle Collection Manifold  16  and upstream of the Particulate Filter  18 . Detection of any other fluid properties can be made by placing the appropriate analyzer in series with the Sample Nozzle Collection Manifold  16  either upstream or downstream of the Particulate Filter  18 , as required. 
         [0081]    The active Static Pressure Control System  30  uses a Differential Pressure Transmitter  42  to measure the difference between the Sample Nozzle Collection Manifold Pressure Port  26  and the Conduit Static Pressure Port  28  and controls the Vacuum Pump  24  (or other suitable device) to make this difference equal to zero. The active Static Pressure Control System  30  constitutes the essence of the present invention.  FIG. 4  shows a cross section of the sampling probe and Conduit Static Pressure Ports. 
         [0082]    The Mass Flow Meter  22  is located at the Sample Loop shown in  FIG. 1 . The preferred embodiment is an In-Line Thermal Mass Flow Meter having a low pressure drop and high flow turn down performance. 
         [0083]    Another preferred embodiment of the present invention shown in  FIG. 1  is the Air Purge Cleaning Controller  36  for dirty fluid applications. It uses a “blow-down” tank of compressed air that flows through a heater (if required) to clean the Particulate Filter  18 , Sample Nozzle Collection Manifold  16 , the Sample Nozzles  14 , Sample Nozzle Manifold Static Pressure Ports  26  and Conduit Static Pressure Ports  28 . The cleaning air with the collected dirt is discharged to the conduit. There is a Valve  40  mounted on the end of the probe  12  that opens up when the cleaning cycle is activated and allows the accumulated dirt to escape into the Conduit  10 . Control Valves  44  are used to direct the purge air into the appropriate components and vent the purged air to the conduit. 
         [0084]    The preferred embodiment utilizes a Fluid Analyzer Measurement Chamber  20  which is essentially a pipe in which the sample gas flows in at one end and out of the other end into the Mass Flow Meter  22 . The Fluid Composition Analyzers  32 ,  34  are in-situ instruments that are usually inserted into a conduit. It is also possible to use extractive gas analyze similar to those used for US EPA CEM Stack Monitors by extracting the samples from the sample loop directly. 
         [0085]    Obviously, many modifications may be made without departing from the basic spirit of the present invention. Accordingly, it will be appreciated by those skilled in the art that within the scope of the appended claims, the invention may be practiced other than has been specifically described herein.