[Code of Federal Regulations]
[Title 40, Volume 31]
[Revised as of July 1, 2007]
From the U.S. Government Printing Office via GPO Access
[CITE: 40CFR1065.220]

[Page 705-706]
 
                   TITLE 40--PROTECTION OF ENVIRONMENT
 
         CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED)
 
PART 1065_ENGINE-TESTING PROCEDURES--Table of Contents
 
                    Subpart C_Measurement Instruments
 
Sec.  1065.220  Fuel flow meter.

    (a) Application. You may use fuel flow in combination with a 
chemical balance of carbon (or oxygen) between the fuel, inlet air, and 
raw exhaust to calculate raw exhaust flow as described in Sec.  
1065.650, as follows:
    (1) Use the actual value of calculated raw exhaust flow rate in the 
following cases:
    (i) For multiplying raw exhaust flow rate with continuously sampled 
concentrations.
    (ii) For multiplying total raw exhaust flow with batch-sampled 
concentrations.
    (2) In the following cases, you may use a fuel flow meter signal 
that does

[[Page 706]]

not give the actual value of raw exhaust, as long as it is linearly 
proportional to the exhaust molar flow rate's actual calculated value:
    (i) For feedback control of a proportional sampling system, such as 
a partial-flow dilution system.
    (ii) For multiplying with continuously sampled gas concentrations, 
if the same signal is used in a chemical-balance calculation to 
determine work from brake-specific fuel consumption and fuel consumed.
    (b) Component requirements. We recommend that you use a fuel flow 
meter that meets the specifications in Table 1 of Sec.  1065.205. We 
recommend a fuel flow meter that measures mass directly, such as one 
that relies on gravimetric or inertial measurement principles. This may 
involve using a meter with one or more scales for weighing fuel or using 
a Coriolis meter. Note that your overall system for measuring fuel flow 
must meet the linearity verification in Sec.  1065.307 and the 
calibration and verifications in Sec.  1065.320.
    (c) Recirculating fuel. In any fuel-flow measurement, account for 
any fuel that bypasses the engine or returns from the engine to the fuel 
storage tank.
    (d) Flow conditioning. For any type of fuel flow meter, condition 
the flow as needed to prevent wakes, eddies, circulating flows, or flow 
pulsations from affecting the accuracy or repeatability of the meter. 
You may accomplish this by using a sufficient length of straight tubing 
(such as a length equal to at least 10 pipe diameters) or by using 
specially designed tubing bends, straightening fins, or pneumatic 
pulsation dampeners to establish a steady and predictable velocity 
profile upstream of the meter.