IPC분류정보
국가/구분 |
United States(US) Patent
등록
|
국제특허분류(IPC7판) |
|
출원번호 |
US-0252841
(2008-10-16)
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등록번호 |
US-8286594
(2012-10-16)
|
발명자
/ 주소 |
|
출원인 / 주소 |
|
대리인 / 주소 |
|
인용정보 |
피인용 횟수 :
11 인용 특허 :
61 |
초록
▼
A water heating apparatus uses a low range blower assembly and a high range blower assembly, each providing a variable flow of premixed fuel and air to a burner assembly. Appropriate choice of the operating ranges of the blower assemblies can provide a high turndown ratio approximately equal to the
A water heating apparatus uses a low range blower assembly and a high range blower assembly, each providing a variable flow of premixed fuel and air to a burner assembly. Appropriate choice of the operating ranges of the blower assemblies can provide a high turndown ratio approximately equal to the product of the turndown ratios of each of the individual blower assemblies. Turndown ratios as high as 25:1 are achievable.
대표청구항
▼
1. A water heating apparatus, comprising: a combustion chamber;a burner assembly located within the combustion chamber;a variable flow premix low range blower assembly communicated with the burner assembly for supplying premixed fuel and air to the burner assembly, the low range blower assembly bein
1. A water heating apparatus, comprising: a combustion chamber;a burner assembly located within the combustion chamber;a variable flow premix low range blower assembly communicated with the burner assembly for supplying premixed fuel and air to the burner assembly, the low range blower assembly being operable over a low flow rate range extending from a low range low end to a low range high end;a variable flow premix high range blower assembly communicated with the burner assembly for supplying premixed fuel and air to the burner assembly, the high range blower assembly being operable over a high flow rate range extending from a high range low end to a high range high end, wherein the high range high end is greater than the low range high end; anda control system operably associated with the low range blower assembly and the high range blower assembly to selectively operate one or both of the blower assemblies as needed in response to heat demand on the water heating apparatus. 2. The apparatus of claim 1, wherein: the high range high end is at least 25 times the low range low end. 3. The apparatus of claim 2, wherein: the low range high end is at least 5 times the low range low end, and the high range high end is at least 5 times the low range high end. 4. The apparatus of claim 1, wherein: the high range blower assembly includes one and only one blower. 5. The apparatus of claim 1, wherein: the high range low end is substantially equal to the low range high end, so that an overall turndown ratio for the water heating apparatus is at least equal to the product of a low range turndown ratio of the low range blower assembly multiplied times a high range turndown ratio of the high range blower assembly. 6. The apparatus of claim 1, wherein: the high range low end is no greater than the low range high end; andthe control system is operable to supply premixed fuel and air to the burner assembly in a continuously variable combined flow rate range extending from the low range low end to at least the high range high end. 7. The apparatus of claim 1, wherein: the burner assembly includes a first plenum communicated with a first foraminous burner wall portion, and a second plenum communicated with a second foraminous burner wall portion, the first and second foraminous burner wall portions being sufficiently close to each other so that flame from the first foraminous burner wall portion will ignite fuel-air mixture exiting the second foraminous burner wall portion;the low range blower assembly is connected to the first plenum to supply premixed fuel and air to the first plenum; andthe high range blower assembly is connected to the second plenum to supply premixed fuel and air to the second plenum. 8. The apparatus of claim 7, further comprising: a direct spark ignition element adjacent the first foraminous burner wall portion, for igniting fuel and air from the first plenum. 9. The apparatus of claim 7, wherein: the first foraminous burner wall portion includes a first cylindrical foraminous burner wall; andthe second foraminous burner wall portion includes a second cylindrical foraminous burner wall and a flat foraminous burner wall spanning one end of the second cylindrical foraminous burner wall. 10. The apparatus of claim 7, wherein: a surface area ratio of the second foraminous burner wall portion to the first foraminous burner wall portion is substantially equal to a ratio of the high range high end to the low range high end, so that with both blower assemblies operating at maximum output a surface heat loading per unit area for the first and second foraminous burner wall portions is substantially equal. 11. The apparatus of claim 1, wherein: the control system is operatively associated with at least one of the low and high range blower assemblies to selectively provide supplemental air without fuel from the at least one blower assembly to the burner assembly. 12. The apparatus of claim 11, further comprising: a sensor for detecting a parameter related to possible condensation of combustion gases within the heating apparatus, the sensor providing an input to the control system; andthe control system is operative to provide the supplemental air without fuel from the at least one blower assembly to the burner assembly in response to the input from the sensor. 13. The apparatus of claim 1, wherein the heating apparatus has a heat input of at least 2,000,000 BTU/hr. 14. The apparatus of claim 1, further comprising: a check valve between the low range blower assembly and the burner assembly for preventing backflow from the burner assembly into the low range blower assembly. 15. The apparatus of claim 1, further comprising: a temperature sensor between the low range blower assembly and the burner assembly for detecting backflow from the burner assembly into the low range blower assembly; andwherein the control system is communicated with the temperature sensor and is operable to shut down the heating apparatus in response to a rise in temperature detected by the temperature sensor. 16. The apparatus of claim 1, further comprising: a temperature sensor between the high range blower assembly and the burner assembly for detecting backflow from the burner assembly into the high range blower assembly; andwherein the control system is communicated with the temperature sensor and is operable to shut down the heating apparatus in response to a rise in temperature detected by the temperature sensor. 17. The apparatus of claim 1, further comprising: at least one blower fan speed sensor operably associated with at least one of the blower assemblies; andwherein the control system receives at least one blower fan speed signal from the at least one blower fan speed sensor, and the control system is operable to compare sensed blower fan speed to a programmed blower fan speed and to shut down the heating apparatus in the event of an unprogrammed change in sensed blower fan speed. 18. The apparatus of claim 1, wherein: the burner assembly is cylindrical in shape and includes first and second internal cylindrical zones divided by an internal wall, the first zone being communicated with the low range blower assembly and the second zone being communicated with the high range blower assembly. 19. The apparatus of claim 18, further comprising: a cylindrical heat exchanger wall defining the combustion chamber inside the cylindrical heat exchanger wall, the cylindrical heat exchanger wall including a first smaller diameter portion within which the first zone of the burner assembly is located and a second larger diameter portion within which the second zone of the burner assembly is located, so that a flame from the first zone fed by the low range blower assembly has a shorter standoff from the cylindrical heat exchanger wall than does a flame from the second zone fed by the high range blower assembly. 20. A water heating apparatus, comprising: a combustion zone;a burner apparatus extending into the combustion zone;a first variable flow premix blower assembly for supplying premixed fuel and air to the burner apparatus, the first blower assembly having a first blower flow rate range extending from a first range low end to a first range high end so that the first blower assembly has a first turndown ratio at least equal to the first range high end divided by the first range low end;a second variable flow premix blower assembly for supplying premixed fuel and air to the burner apparatus, the second blower assembly having a second flow rate range extending from a second range low end to a second range high end so that the second blower assembly has a second turndown ratio equal to the second range high end divided by the second range low end, the second range low end being substantially equal to or less than the first range high end so that there is no substantial gap between the first and second flow rate ranges; anda control system operably associated with the first and second blower assemblies to selectively operate one or both of the blower assemblies as needed in response to heat demand on the heating apparatus, wherein the first and second blower assemblies together provide a continuous combined turndown ratio at least as great as the sum of the first and second turndown ratios. 21. The apparatus of claim 20, wherein the second range low end is substantially equal to the first range high end, and the continuous combined turndown ratio is at least as great as the product of the first turndown ratio multiplied times the second turndown ratio. 22. The apparatus of claim 20, wherein the first and second flow rate ranges are substantially equal and the continuous combined turndown ratio is equal to the sum of the first and second turndown ratios. 23. The apparatus of claim 20, wherein the first and second flow rate ranges partially overlap each other and the continuous combined turndown ratio is less than the product of the first turndown ratio multiplied times the second turndown ratio. 24. The apparatus of claim 20, wherein: the first and second flow rate ranges are low and high flow rate ranges, respectively, the second range low end being higher than the first range low end, and the second range high end being higher than the first range high end. 25. A method of operating a water heating apparatus, the method comprising: (a) supplying premixed fuel and air to a burner assembly of the apparatus via a low range blower assembly at a flow rate within a low flow rate range;(b) supplying additional premixed fuel and air to the burner assembly via a high range blower assembly at a flow rate within a high flow rate range, the high range extending higher than the low range and there being no substantial gap between the low range and the high range; and(c) via an automated control system, selectively operating the blower assemblies as needed in response to heat demand on the water heating apparatus so that premixed fuel and air is supplied to the burner assembly over a substantially continuously variable combined flow rate range extending from a low end of the low flow rate range to at least a high end of the high flow rate range. 26. The method of claim 25, further comprising: prior to step (b), igniting the fuel and air from the low range blower assembly as the fuel and air exits the burner assembly thereby creating a first flame; andduring step (b), igniting the fuel and air from the high range blower assembly with the first flame. 27. The method of claim 26, wherein: the step of igniting the fuel and air from the low range blower assembly comprises igniting with a direct spark ignition device. 28. The method of claim 25, wherein in step (c) the continuously variable combined flow rate range provides a turndown ratio of at least 25 to 1. 29. The method of claim 28, wherein in step (c) the continuously variable combined flow rate range corresponds to a water heating apparatus input range from at most 80,000 BTU/hr to at least 2,000,000 BTU/hr. 30. The method of claim 25, further comprising: sensing a parameter related to possible condensation of combustion gases within the heating apparatus; andvia the automated control system in response to the sensed parameter, selectively operating one of the blower assemblies to provide supplemental air without fuel to the burner assembly to raise the condensation point of the combustion gases within the heating apparatus. 31. The method of claim 25, further comprising: preventing backflow from the burner assembly to the low range blower assembly. 32. The method of claim 31, wherein the preventing step comprises closing a mechanical check valve between the low range blower assembly and the burner assembly. 33. The method of claim 31, wherein the preventing step comprises: detecting a temperature rise between the low range blower assembly and the burner assembly; andshutting down the heating apparatus via the automated control system in response to the detected temperature rise. 34. The method of claim 31, wherein the preventing step comprises: sensing a blower fan speed of the low range blower assembly; andshutting down the heating apparatus via the automated control system in response to a determination that the sensed blower fan speed is different from an expected blower fan speed.
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