Method and apparatus for measuring evaporative vehicle emissions in a fixed-volume/variable temperature test chamber

• US 5,369,976 A
• Filed: 04/26/1993
• Issued: 12/06/1994
• Est. Priority Date: 04/26/1993
• Status: Expired due to Fees

• Current Assignee: Power-Tek, Inc.
• Original Assignee: Power-Tek, Inc.
• Inventors: Ratton, Kenneth
• Primary Examiner(s): Williams, Hezron E.
• Assistant Examiner(s): Olsen, James M.
• Application Number:
  US08/053,086
• Time in Patent Office: 589 Days
• Field of Search: 73/118.1, 73/23.35, 73/23.2, 73/116, 73/23.31, 73/40, 73/49.7
• US Class Current: 73/23.2
• CPC Class Codes: G01M 17/007 Wheeled or endless-tracked vehicles G01M17/08 takes precedence
• CPC Class Codes: G01N 33/0016 by regulating a physical variable, e.g. pressure, temperature
• CPC Class Codes: G01N 33/2852 alcohol/fuel mixtures

Abstract

Provided is a method and apparatus for measuring evaporative vehicle emissions in a fixed-volume/variable temperature test chamber. The method comprises the steps of providing a volume compensation device in fluid communication with a test chamber for compensating for changes in the test chamber fluid volume, determining the density of the evaporative emissions and the test chamber fluid in mass per unit volume at selected sample times t_n, where n is a positive integer, measuring the temperature of the test chamber fluid at the sample times t_n, measuring the absolute fluid pressure of fluid at the sample times t_n, determining the difference in the test chamber fluid volume between successive sample times t_n, determining the mass of the evaporative emissions in lost volume and mass measurements and summing the determined masses of the evaporative emissions to provide a calculation of the evaporative emissions lost by the volume compensation device during expansion of the test chamber fluid and summing this with the final sample to determine the total evaporative emissions from a vehicle. In an alternative embodiment, a plurality of impingers are also provided for use in determining the lost mass of alcohol emissions in flexible fueled vehicles.

Claims

1. A leak-tolerant method of measuring evaporative emissions from motor vehicles in accordance with prescribed fluid temperature profiles in a fixed volume test chamber filled with a fluid having a predetermined mass, volume, temperature and pressure at time t_o and a determined mass at a final reading t_f, (M_f), 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;

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

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

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

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

determining the difference in said test chamber fluid volume between successive sample times t_n, (Vn);

determining the lost mass of said evaporative emissions in Vn, (M_n);

summing the determined masses of said evaporative emissions (M_n) to provide a calculation of the total evaporative emissions lost by said volume compensation means during expansion of said test chamber fluid, (M_loss); and

summing M_loss and M_f.

2. A leak-tolerant method of measuring alcohol emissions from motor vehicles in accordance with prescribed fluid temperature profiles in a fixed volume test chamber, comprising the steps of:

providing flow metering means in fluid communication with said test chamber for compensating for changes in said test chamber fluid volume;

providing a first, second and third impinger, each adapted to be removably connected to said flow metering means;

passing a sample of said test chamber fluid through said first impinger at a first selected rate of flow for a first selected period of time to determine the initial concentration of alcohol in said test chamber fluid;

replacing said first impinger with said second impinger for the duration of said temperature profiles to determine the mass of alcohols lost during said temperature profiles;

replacing said second impinger with said third impinger and passing a sample of said test chamber fluid therethrough at a second selected rate of flow for a second selected period of time to determine the final concentration of alcohol in said test chamber fluid;

determining the difference between said initial and final alcohol concentrations,

determining the mass of said determined alcohol concentration difference; and

summing said determined mass of said alcohol concentration difference with said mass of alcohols lost during said temperature profiles.