FLUID LEVEL MEASUREMENT SYSTEM AND METHOD

• US 20110239664A1
• Filed: 04/01/2011
• Published: 10/06/2011
• Est. Priority Date: 04/01/2010
• Status: Active Grant

• Current Assignee: Thermo King Corporation (Trane Technologies plc)
• Original Assignee: Thermo King Corporation (Trane Technologies plc)
• Inventors: McReynolds, Anthony J., Hochstein, Randy, Sanders, Russell L., Muralidhar, Ashok
• Granted Patent: US 8,997,512 B2
• Time in Patent Office: Days
• US Class Current: 62/56
• CPC Class Codes: G01F 23/2962 Measuring transit time of reflected waves
• CPC Class Codes: G01F 23/2968 Transducers specially adapted for acoustic level indicators
• CPC Class Codes: Y10T 29/49002 Electrical device making

Abstract

A transport refrigeration system for a transportable temperature controlled space includes a compressor, a condenser and an evaporator fluidly connected to one another, an engine operatively connected to the compressor, and a fuel tank assembly fluidly connected to the engine. The fuel tank assembly includes a fuel tank configured to contain the fuel, a fuel vapor and air, and an ultrasonic fluid level sensor for sensing a level of fuel, the fuel tank having a maximum fuel level. The fluid level sensor includes a transducer having a ring period. The distance from the fluid level sensor to the maximum fuel level is at least half the distance that the sound travels through the fuel vapor and air during the ring period of the transducer.

Claims

1. A transport refrigeration system for a transportable temperature controlled space, the transport refrigeration system comprising:

a compressor, a condenser and an evaporator fluidly connected to one another;

an engine operatively connected to the compressor; and

a fuel tank assembly fluidly connected to the engine, wherein the fuel tank assembly is subjected to vibrations from movement of the temperature controlled space as the temperature controlled space is transported, the fuel tank assembly including;

a fuel tank configured to contain a fuel, a fuel vapor and air, the fuel tank having a maximum fuel level;

an ultrasonic fluid level sensor for sensing a level of fuel, the fluid level sensor coupled to the fuel tank and positioned a distance from the maximum fuel level; and

a power source electrically connected to the fluid level sensor for powering the fluid level sensor;

wherein the fluid level sensor includes a transducer having a ring period and wherein the distance from the fluid level sensor to the maximum fuel level is at least half the distance that the sound travels through the fuel vapor and air during the ring period of the transducer.

2. The transport refrigeration system of claim 1, wherein the power source is electrically connected to the transport refrigeration system such that the fuel level sensor is subjected to electrical noise from startup of the transport refrigeration system

3. The transport refrigeration system of claim 1, further comprising a spacer positioned adjacent the fluid level sensor for providing a dry space between the fluid level sensor and the maximum fuel level, wherein the dry space has a length of at least half the distance that the sound travels through the fuel vapor during the ring period of the transducer.

4. The transport refrigeration system of claim 3, wherein the fluid level sensor abuts the spacer.

5. The transport refrigeration system of claim 3, wherein the spacer extends from an outer surface of the fuel tank.

6. The transport refrigeration system of claim 3, wherein the spacer is positioned substantially within an interior of the tank, wherein the spacer provides the dry space by trapping fuel vapor and air inside the spacer.

7. The transport refrigeration system of claim 1, wherein the fluid level sensor is distanced from the maximum fuel level by at least half a nearfield distance, wherein the near field distance is calculated using the equation D_nf=V_sd*T_t, where D_nf is the near field distance, V_sd is the speed of sound through the fuel vapor and air, and T_t is the ring period of the transducer.

8. A transport refrigeration system for a transportable temperature controlled space, the transport refrigeration system comprising:

a compressor, a condenser and an evaporator fluidly connected to one another;

an engine operatively connected to the compressor; and

a fuel tank assembly fluidly connected to the engine, wherein the fuel tank assembly is subjected to vibrations from movement of the temperature controlled space as the temperature controlled space is transported, the fuel tank assembly including;

a fuel tank configured to contain a fuel, a fuel vapor and air, the fuel tank having a maximum fuel level and an interior and an exterior;

an ultrasonic fluid level sensor for sensing a level of fuel, the fluid level sensor coupled to the fuel tank and spaced from the maximum fuel level; and

a tubular spacer having a first end and a second end and a length between the first end and the second end, wherein the first end is positioned adjacent the ultrasonic fluid level sensor and the second end is positioned in communication with the interior of the tank;

wherein the fluid level sensor includes a transducer having a ring period and wherein the length of the spacer is at least half the distance that the sound travels through the fuel vapor during the ring period of the transducer.

9. The transport refrigeration system of claim 8, wherein the spacer extends from an outer surface of the fuel tank.

10. The transport refrigeration system of claim 8, wherein the spacer is positioned substantially within an interior of the tank, wherein the spacer provides the dry space by trapping a gas inside the spacer.

11. The transport refrigeration system of claim 8, wherein the length of the spacer is at least half a nearfield distance, wherein the near field distance is calculated using the equation D_nf=V_sd*T_t, where D_nf is the near field distance, V_sd is the speed of sound through the fuel vapor and air, and T_t is the ring period of the transducer.

12. A method for positioning an ultrasonic fluid level sensor in a tank assembly including a tank containing a fluid, a fluid vapor and air, wherein the fluid level sensor includes a transducer having a ring period, the method comprising:

calculating a near field distance of the fluid level sensor based on the speed of sound through the fluid vapor and the ring period of the transducer;

determining a maximum fluid level in the tank; and

positioning the fluid level sensor at a distance from the maximum fluid level greater than or equal to half the near field distance.

13. The method of claim 12, wherein positioning the fluid level sensor includes providing a spacer between the fluid level sensor and the maximum fluid level.

14. The method of claim 12, wherein positioning the fluid level sensor includes:

providing a spacer adjacent the fluid level sensor, the spacer extending into an interior of the tank assembly, and

providing fuel vapor and air inside the spacer for spacing a surface of the fluid from the fluid level sensor.

15. The method of claim 12, wherein the near field distance is calculated using the equation D_nf=V_sd*T_t, where D_nf is the near field distance, V_sd is the speed of sound through the fuel vapor and air, and T_t is the ring period of the transducer.