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Method and apparatus for measuring evaporative emissions in a fixed-volume enclosure

  • US 5,526,675 A
  • Filed: 12/06/1994
  • Issued: 06/18/1996
  • Est. Priority Date: 04/26/1993
  • Status: Expired due to Fees
First Claim
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1. A leak-tolerant method of measuring evaporative emissions in a fixed volume test chamber filled with a fluid having a predetermined mass of evaporative emissions M1, chamber volume, temperature and pressure at time t0 and a determined mass (Mn) of evaporative emissions at a reading tn, comprising the steps of:

  • providing volume compensation means in fluid communication with said test chamber for compensating for changes in said test chamber fluid volume;

    measuring the temperature of said test chamber fluid at said sample times tn ;

    measuring the absolute fluid pressure of said test chamber at said sample times tn ;

    determining the mass of evaporative emissions present in the chamber;

    determining the density of said evaporative emissions in said test chamber fluid in mass per unit volume at selected sample times tn, where n is a positive integer;

    determining the theoretical volume change of said test chamber fluid at said sample times tn in accordance with the Ideal Gas Law (PV=nRT);

    determining the aspirated mass of said evaporative emissions in Masp(n) ;

    summing the determined masses of said evaporative emissions Masp(n) to provide a calculation of the total evaporative emissions aspirated by said volume compensation means during expansion of said test chamber fluid, (Σ

    Masp(n)); and

    summing (Σ

    Masp(n)) and Mn, and subtracting M1 to determine a total mass of evaporative emission.

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