Vented propane combustion chamber for insect attractant engine
View Patent ↗A vented combustion chamber for an insect attractant engine is provided for a flying insect trapping device of the type that relies upon combustion of a fuel to generate a flow of carbon dioxide to attract flying insects. The combustion chamber, which is generally tubular and horizontally oriented in operation, is vented through a hole formed in one side of the chamber wall that extends from the outer surface of the chamber into the interior thereof. During operation of the device, this through-hole allows gas inside the chamber to be vented to the outside, changing the effective length of the combustion chamber for the purposes of wave generation is changed so that creation of a resonance cycle or standing wave, and the resulting acoustic phenomenon of howling, is prevented.
1. A combustion device for generating an outflow of exhaust gas comprising a combustion chamber having a generally tubular body extending between an inlet and an outlet, said combustion chamber having a substantially horizontal orientation when in use, the exhaust gas exiting said outlet being drawn away from the combustion device by an exhaust fan, an exterior wall of said combustion chamber having a through-hole formed therein with a spark ignitor electrode assembly mounted in said through-hole, said combustion chamber further including a vent formed using said through-hole through which gas inside said chamber is vented to surrounding atmosphere during device operation to prevent formation of a standing wave in said chamber.
2. The combustion device as set forth in claim 1 , wherein the device is part of an insect trapping apparatus.
3. The combustion device as set forth in claim 1 , wherein the spark ignitor electrode assembly includes a spark ignitor electrode that is received within said through-hole and a spark ignitor electrode mounting flange, said spark ignitor electrode assembly mounting flange being mounted on top of a thermistor assembly mounting flange to create a gap between the spark ignitor electrode assembly mounting flange and the combustion chamber wall, said gap in combination with an annular clearance area between an outer surface of said spark ignitor electrode and an inner diameter of said through-hole forming said vent.
4. The combustion device as set forth in claim 1 , wherein the vent is formed by a hole that extends through the wall into an interior of said combustion chamber, said hole having a cross-sectional area of about 0.025 square inches.
5. The combustion device as set forth in claim 1 , wherein the vent is formed by a hole that extends through the wall into an interior of said combustion chamber, said hole having a cross-sectional area of no more than about 0.05 square inches.
6. The combustion device as set forth in claim 5 , wherein the hole has a diameter of about 0.179 inches.
7. The combustion device as set forth in claim 1 , wherein the spark ignitor electrode assembly includes a spark ignitor electrode that is received within said through-hole and a mounting flange, a spacer and a fastening element for securing the spark ignitor electrode to the combustion chamber wall, said spacer being positioned between said flange and said wall to create a gap between the flange and the wall, said gap in combination with an annular clearance area between an outer surface of said electrode and an inner diameter of said through-hole forming said vent.
8. The combustion device as set forth in claim 7 , wherein said annular clearance area has a cross-sectional area of about 0.025 square inches.
9. The combustion device as set forth in claim 7 , wherein said annular clearance area has a cross-sectional area of no more than about 0.05 square inches.
10. The combustion device as set forth in claim 9 , wherein said gap is at least about 0.026 inches.
11. An insect attractant engine for an insect trapping device configured to be used with a fuel supply containing a combustible fuel, the engine comprising:
a combustion device configured to provide an interior combustion chamber for continuous combustion of the combustible fuel therein to create an exhaust gas including carbon dioxide, an exterior wall of said combustion chamber having a through-hole formed therein with a spark ignitor electrode assembly mounted in said through-hole;
an exhaust outlet configured to receive the exhaust gas;
an air movement generator for pulling the exhaust gas away from the exhaust outlet and creating an air flow through said combustion chamber; and
a vent formed using said through-hole in the exterior wall of said combustion chamber through which gas may be vented to surrounding atmosphere from said chamber during said continuous combustion to prevent formation of a standing wave in said chamber.
12. The insect attractant engine as set forth in claim 11 , wherein the vent is formed by a hole that extends through the wall into an interior of said combustion chamber, said hole having a cross-sectional area of no more than about 0.05 square inches.
13. The insect attractant engine as set forth in claim 11 , wherein said air movement generator is an exhaust fan.
14. The insect attractant engine as set forth in claim 11 , wherein said combustion chamber has a generally tubular configuration that is substantially horizontal in orientation during operation.
15. The insect attractant engine as set forth in claim 14 , wherein said spark ignitor electrode assembly includes a spark ignitor electrode that is received within said through-hole and a mounting flange, said spark ignitor electrode assembly mounting flange being mounted on top of a thermistor assembly mounting flange to create a gap between the spark ignitor electrode assembly mounting flange and the combustion chamber wall, said gap in combination with an annular clearance area between an outer surface of said electrode and an inner diameter of said through-hole forming said vent.
16. The insect attractant engine as set forth in claim 14 , wherein said spark ignitor electrode assembly includes a spark ignitor electrode that is received within said through-hole and a mounting flange, a spacer and a fastening element for securing the electrode to the combustion chamber wall, said spacer being positioned between said flange and said wall to create a gap between the flange and the wall, said gap in combination with an annular clearance area between an outer surface of said electrode and an inner diameter of said through-hole forming said vent.
17. The insect attractant engine as set forth in claim 16 , wherein said annular clearance area has a cross-sectional area of about 0.025 square inches.
18. The insect attractant engine as set forth in claim 16 , wherein said annular clearance area has a cross-sectional area of no more than about 0.05 square inches.
19. The insect attractant engine as set forth in claim 18 , wherein said gap is at least about 0.026 inches.