GB2243904A - Porous block wick type burner - Google Patents

Abstract

A burner for use in apparatus for pre-heating a vehicle engine comprises a housing 102, a pressurised liquid fuel inlet 28, a wick member 200 with base portion 202 received in the housing (in place of the wick 106 and base 104 in Fig 5) and ribs 206 extending therefrom. The liquid fuel is transferred through the wick by the fuel pressure and capillary action and is ignited initially by a starter wick 124 and igniter 122. The wick member may be sintered bronze or stainless steel or of ceramic material. <IMAGE>

Description

DESCRIPTION BURNER The invention relates to liquid fuel burners. The invention is useful for heaters for watercooled diesel engines.

It is well known that combustion engines, particularly diesel automobile and goods vehicle engines, and off-highway equipment, are difficult to start in cold weather. Prior engine heaters are generally adapted for heating engines overnight. But, such devices are generally not suitable for rapidly preheating engines.

The present invention resides in a liquid fuel burner comprising: a housing having a fuel inlet; a unitary porous wick member received in an opening in said housing, said wick member having a base portion and a rib portion integral with and projecting from said base portion; and means for pressurlzing fuel within said housing above atmospheric pressure for propelling fuel through said unitary porous wick member.

The housing is preferably cup-shaped. The fuel supply means may comprise a fuel pump and a pressure-actuated inlet valve. An igniter may be provided. The fuel pump and the inlet valve operate to maintain fuel pressure in the housing slightly above atmospheric pressure, forcing the fuel through the fuel passages in the plate and into the wick. The amount of fuel delivered to the wick may thus be controlled by regulating the output of the fuel pump.

The inlet valve operates to close off fuel to the burner when the latter is not in operation. A glow plug may be used for igniting the burner.

The invention is further described, by way of example, with reference to the accompanying drawings, in which: Fig.l is a schematic perspective view of a heater fitted with a liquid fuel burner; Fig.2 is a horizontal cross-sectional view of the heater, taken along line 2-2 of Fig.l, illustrating a two-stage heat exchanger; Fig.3 is a vertical cross-sectional view of the heater3 taken along line 3-3 of Fig.2; Fig.4 is a plan view of the burner; Fig. 5 is a vertical cross-sectional view taken along line 5-5 of Fig.4 Fig.6 is a schematic electrical wiring diagram relating to the heater; Fig.7 is a schematic logic diagram for the operation and control of the heater: Fig.8 is a plan view of a burner plate for the burner of Figs. 4 and 5; and Fig.9 is a side view of the burner plate of Fig.8.

Referring to Fig.l, a watercooled engine 10, a vehicle fuel tank 12, vehicle battery compartment 14 and a storage battery 16 are schematically depicted.

A liquid, namely engine coolant, is circulated through a heater 18 through a liquid inlet line 20 and a liquid return line 22. The liquid is circulated by a liquid pump 24 having a drive motor 26. Fuel is supplied to the heater 18 from the tank 12 through the fuel line 28 by a fuel pump 30 having a drive motor 32. Clean air is supplied to the heater 18 through an air line 34 from a blower 36. The blower 36 is driven by a motor 38. Warm air is discharged from the heater 18 through an air discharge line 40.The warm air discharge line 40 is connected to the battery compartment 14 for preheating the battery 16, and then to the engine compartment (not shown) through a line 11. Additionally. warm clean air from line 40 may be supplied to tLle operator's (driver's) compartment (not shown) through a line 15. or to further improve cold starting, to the engine air intake (not shown) through a line 17. Combustion gases are expelled from the heater 18 throut all exhaust pipe 42.

The liquid lines 20 and 22 are preferably conventional vulcanized rubber hose. The liquid pump 24 and motor 26 preferably are a conventional coolant pump and a 12-volt direct current motor.

The fuel line 28 is preferably copper tubing. The fuel pump 30 and motor 32, likewise are preferably a conventional automobile fuel pump whose fuel delivery rate can be varied by varying the voltage applied to the 12-volt direct current motor.

The air lines 34 and 40 are preferably conventional flexible, heat resistant pipe having a steel spring reinforcing member. The blower 36 and motor 38 are preferably a squirrel cage, "heater" type blower having a 12-volt direct current motor.

The exhaust pipe 42 is preferably flexible steel pipe.

Referring now to Figs. 2 and 3, the heater 18 comprises a combustion chamber 44, a gas-to-air or first stage heat exchanger 46, and an air-to-liquid or second stage heat exchanger 48. The heat exchanger 46 comprises a plurality of spaced gas conduits 50 from the combustion chamber 44, defining air passages 52 therebetween. The first stage heat exchanger 46 also preferably includes baffles 60 in the gas conduits 50, and baffles 62 in the. air passages 52 to increase the path length of the gas and air, respectively, to increase efficiency of heat exchange from the combustion gas to the clean air.

In the preferred embodiment illustrated in Figs. 2 and 3, the gas-to-air stage heat exchanger 46 comprises a cylindrical member having a plurality of pie-shaped gas conduits 50 defining a like number of air passages 52 therebetween. However, other configurations may be used. For example, an alternative design for the gas-to-air heat exchanger could comprise one or more cylindrical combustion gas pipes from the combustion chamber surrounded by a larger diameter cylindrical member, air passage(s) being defined by the spaces between the pipes and/or between the pipes and the cylindrical member.

The air-to-liquid stage heat exchanger 48 comprises a liquid jacket 64 having a liquid inlet 66 and a liquid outlet 68, and a multiplicity of air conduits 70 therethrough. The second stage heat exchanger may include one or more baffles 72 to increase the path length of the liquid through the heat exchanger 48.

In the preferred embodiment illustrated in Figs. 2 and 3, the air-to-liquid stage heat exchanger 48 is annular and surrounds the gas-to-air stage heat exchanger 46. This design is preferred for several reasons. Firstly, heat from gas conduits 50 and air passages 52 radiates through the liquid jacket 64 contributing to heating the liquid. Thereby, the efficiency of the ultimate heat exchange from the combustion gas to liquid is increased. Secondly, the concentric design is compact, thus saving valuable space. Thirdly, the air-to-liquid stage exchanger 48 acts to insulate the extremely hot gas-to-air stage exchanger 46 from the environment in which the heater is installed, e.g. the vehicle engine compartment.

A first air manifold 54 directs air into the heat exchanger 46. The air manifold 54 has a clean air inlet 56 and outlets 58. The air manifold 54 receives clean air through its inlet 56 and directs the same against the combustion chamber 44 and then through its outlets 58 into the air passages 52.

A second air manifold 74 is provided to direct the hot air from the gas-to-air stage exchanger 46 into the air-to-liquid stage exchanger 48. The manifold 74 has inlets 76 connected to each of the air passages 52 and outlets 78 into one end of the air conduits 70.

A discharge air manifold 80 has inlets 82 for receiving warm air from the air conduits 70, and an outlet pipe 84. The outlet pipe 84 is connected to the air discharge line 40. which is connected to the battery compartment 14, engine compartment line 11.

operator's compartment line 15 and engine intake line 17, as previously aescribed.

The preferred embodiment of the. heater 18 further includes an exhaust manifold 86 having inlets 88 for receiving combustion gas from gas conduits 50, an air intake manifold 90 having an inlet pipe 92 and an annular outlet 94, and an air jacket 96. The inlet air manifold serves to shield and insulate the exhaust manifold 86 from the environment in which the heater 18 is installed, and to partially heat the incoming air. The air jacket 96 serves to insulate the second air manifold 74, discharge air manifold 80 and air-to-liquid stage heat exchanger 48 from the environment, and to convey the air from the intake manifold 90 to the first air manifold 54.

The gas-to-air stage heat exchanger 46 and exhaust manifold 86 are preferably fabricated from stainless steel sheet to withstand the extreme heat of the burning gases. The air jacket 96 and various air manifolds 90, 54, 74 and 80 may be fabricated from mild steel. The air conduits 70 are preferably small diameter copper or brass tubing, as such metals have superior heat transfer properties. The liquid jacket 64 and liquid inlet and outlet pipes 66 and 68 are preferably fabricated from brass tubing and silver soldered together or otherwise c6ld formed integral to eacr. other.

A burner 98 is secured in the combustion chamber 44 as illustrated in Fig.3. As shown in Figs. 3 and 5, the combustion chamber 44 is provided with openings 100 to permit air to be forced from the first air manifold 54 into the combustion chamber 44.

The burner 98 comprises an open top cup-shaped housing 102 and a plate 104 (Figs. 4 and 5) welded or press fitted into the top of the housing 102.

Figs. 8 and 9 illustrate a preferred burner plate 200 for the burner 98. The plate 200 replaces the plate 104 illustrated in Fig. 4. The plate 200 is moulded from a porous heat resistant material, such as ceramic, sintered metal or combination ceramic and sintered metal materials. Favourable results have been obtained with sintered bronze. However, other metals, such as sintered stainless steel may be used.

The plate 200 has a base portion 202 and rib or wick portion 204 integral therewith. The rib or wick portion 204 comprises a plurality of radially extending ribs 206 for supporting and carrying a flame. Although a radial rib pattern is illustrated, other patterns, such as a square or "waffle" pattern, could be used.

While one embodiment of burner plate has been shown and described, other embodiments may be constructed within the scope of this invention. The function of the burner plate is to enclose the housing 102 and provide fuel passages from the interior of the housing to the wick means. The wick means is integral with the plate as shown in Figs. 8 and 9. The wick means may be of any pattern to hold and carry a flame.

The housing 102 has a fuel inlet 114. The inlet 114 is preferably fitted with a valve 116. The valve 116 includes a closure member 120 and a spring 118. The spring 118 biases the closure member 120 in an upstream direction to close fuel flow to the housing 102.

In operation, the fuel pump 30 produces sufficient pressure upstream of the valve 116 to overcome the force of the spring 118 and thereby shuttle the closure member 120 to permit fuel to enter the housing 102. When the housing 102 is filled, the fuel within the housing is pressurized slightly above atmospheric pressure, forcing the fuel through the fuel passages 112 and into the burner plate 200.

The fuel from the housing is forced under pressure through the pores in the plate 200 into the wick means 206. Capillary action also assists in drawing fuel from the housing 102.

To ignite the burner 98, a glow plug 122 is secured either to the exterior of the burner 98 or to the manifold . It is preferable to secure the glow plug 122 to manitold 54 adjacent to, but not in contact with, the burner 98 or combustion chamber 44 to keep the plug as cool as possible. The glow plug is also cooled by the incoming air at 54. A starter wick 124 is secured to the burner 98 with one end proximate to the glow plug 122 and the other end in contact with the wick means 206, to transmit a flame started by the glow plug 122 to the wick means 206. Other means for igniting the burner 98 may be employed, if desired.A hood 126 is secured to the burner 98 surrounding the glow plug 122 to shelter the same from draught which would inhibit ignition, and also to direct starting fumes up through the combustion chamber 44 rather than backing up through the inlet 58.

The housing 102, plate 104 and hood 126 are preferably fabricated from stainless steel to withstand heat, but can be of mild steel due to the cooling effect of the incoming air. The starting wick 124 is preferably stainless steel mesh to withstand heat. The inlet 114 and valve 116 may be fabricated from steel tubing. The closure member 120 is preferably a brass or stainless steel ball, and. the spring 118 is preferably stainless steel.

Referring now to Figs. 6 and 7, a liquid temperature sensor 128 is secured to the inlet liquid line 20 to sense liquid temperature. The sensor 128 is preferably a simple heat switch set to open en the liquid temperature reaches a predetermined value, e.g., 1759F (79"C). The sensor 128 is electrically connected through a microprocessor 131 within a control module 130 to the coil of the power relay 132.Thus, when the predetermined liquid temperature is reached, the sensor 128 opens and initiates the shut down sequence, namely: cutting power to the fuel pump 32, which decreases the pressure in the fuel line 28, causing the valve 116 to close fuel flow to the burner 98; increasing the blower speed to maximum to consume remaining fuel in the burner, and thereby extinguish the same; followed by unlatching the power relay 132.

Means for maximizing combustion efficiency to produce maximum heat and minimize fuel consumption is provided. An air temperature sensor 136 is secured in the second air manifold 76. Alternatively, the sensor 136 may be secured in one of the gas conduits 50, one of the air passages 52 or exhaust manifold 86, or any other location where the temperature is primarily dependent on the heat produced by combustion. It is preferable to secure the sensor 136 in the air manifold 76 as the air here is somewhat cooler and cleaner than in the combustion gas flow, thus increasing the life and effectiveness of the sensor. The sensor 136 is electricallv connected to the flicro-processor 131 within the control module 130, as is the fuel pump motor 32 and blower motor 38.

The micro-processor 131 in the control module 130 monitors variations in the electrical resistance of sensor 136. The micro-processor 131 also montitors and controls the voltage across the fuel pump motor 32 and blower motor 38. The microprocessor 131 is programmed to: incrementally increase the voltage to the fuel pump motor 32 when the sensor 136 indicates a decrease in temperature over a period of time, thus increasing the rate of fuel delivery to the burner 98; incrementally increase the voltage to the blower motor 38 when the sensor 136 indicates an increase in temperature over a period of time, thus increasing the rate of delivery of forced air to the burner 98; and decreasing by one-half an increment the voltage to the fuel pump motor 32 when the sensor 136 indicates an increase in temperature over a period of time and maximum voltage to the blower motor 38 has been achieved, thus decreasing fuel delivery to the burner 98 to avoid burning an over-rich mixture which results in smoking, and to avoid fuel flooding out of the housing 98. The foregoing monitoring and fuel and air adjustIng functions continue throughout the heating cycle maximizing combustion efficiency.

The apparatus also includes various other monitoring features. The valve 116 is wired to form a fuel flow indicator switch 138. Specifically, one electrical lead may be connected to the closure member 120 and another to a contact (not shown) on the valve housing 116 such that a circuit is completed when the member 120 is in a closed position and the circuit is broken when the member 120 is in an open position. Thereby, fuel delivery may be monitored. A burner flame sensor 140 is included. The sensor 140 is preferably a photo-electric cell. The sensor 140 is wired to the microprocessor 131 within control module 130 to discontinue power to the glow plug 122 via the glow plug relay 154 when ignition has been achieved and a healthy flame exists across the wick matrix 110 (or 206).

The apparatus and the complete logic of the control module is set forth in the Fig. 7 schematic flow diagram. The sequence of engaging components serves a self-diagnostic function for the operator. When the operator desires to preheat his engine and battery, he presses the main power switch on button 142 (momentary contact) which starts the liquid pump 24 circulating liquid from the engine 10 through line 20 into the air-to-liquid stage heat exchanger 43 and back to the engine 10 through line 22. The micro-processor 131 senses liquid flow via sensor 128 (flow switch portion). If no flow is perceived, a pump fault indicator light 144 is lit and the power relay 132 is prevented zrom latching. If no flow is indicated during operation power relay 13' is unlatched.If the flow switch closes, the power relay 132 is latched lighting the "ON" indicator light 146, and delivering power to the coil portion of the glow plug relay 154, latching the same, thereby delivering power to the glow plug 122. If a voltage drop is not indicated across the glow plug 122, an ignition fault indicator light 148 is lit and the power relay 132 is unlatched. If there is a voltage drop across the glow plug 122, a minimum voltage is delivered to the blower motor 38 through the micro-processor 131 causing the blower to force air through line 34 into the intake manifold 90 through air jacket 96 and into the first air manifold 54. A portion of the air then travels through opening 100 and up through the hood 126 to ensure a draught within the combustion chamber 44.The remaining air travels through the air passages 52 of the gas-to-air heat exchanger 46, the second air manifold 74, the air conduits 70 of the air-to-liquid heat exchanger 48, the air discharge manifold 80, the air discharge line 40 and into the battery compartment 14, and/or the engine compartment (line 11), operator S compartment (line 15) and engine intake (line 17). The blower output is monitored bv the micro-processor 131, via an air flow switch 156 located in line 34. If the air flow switch 156 does not close, indicating no air flow a blower fault lamp 150 s lit, and the power relay 132 is unlatched. If the air flow switch 156 closes, indicating that air is being delivered, coolant temperature is checked by micro-processor 131 via sensor 128.If the predetermined temperature has not been achieved, power is delivered to the fuel pump motor 32 through micro-processor 131 to drive the fuel pump 30.

Fuel is drawn from the fuel tan 12 through line 28 to the valve 116. When the fuel pressure in line 28 exceeds the force of the spring 118, the closure member 120 is forced open, permitting fuel to travel into the burner housing 102 where it passes through the openings 112 in the plate 104 (200) and into the wick 110 (204).

If the fuel flow switch 138 remains open, a fuel fault indicator light 152 is lit. If the fuel flow switch 138 closes and the flame sensor 140 indicates no flame.

power is continued to the glow plug 122 due to the time delay 157. The time delay 157 allows for slow ignition with thick fuels without flooding. RJhen the burner ignites. the flame sensor 140 detects the flame, and the glow plug relay 154 is unlatched. disconnecting power to the glow plug 122. The micro-processor 131 then steps up the voltage across the fuel pump motor 32 and blower motor 38, increasing fuel and air delivery, and holds them at a predetermined level. The micro-processor senses and stores in memory the temperature indicated by the air te.?eracure sensor 136. If a decrease is sensed) fuel delivery is increased again by an increment.If no decrease is sensed, the micro-processor then incrementally increases and holds voltage across the blower motor -38 increasing the flow of forced air to the combustion chamber 44. The micro-processor 131 again checks for a temperature decrease from sensor 136. If the temperature decreases, fuel supply is incrementally increased and held, enriching the fuel/air mixture. Temperature at sensor 136 will then go up, the micro-processor again increases blower speed and senses a temperature drop at 136. The cycle continues until maximum voltage is across the blower motor 38. Once maximum blower speed has been achieved and air temperature increases, as indicated by the sensor 136, fuel delivery is decreased by less than a full increment to lean the mixture. The process of adjusting the fuel delivery rate balanced on the lean side by the blower motor status continues throughout operation to maximize combustion efficiency and heat production with maximum smoking.

In the meantime flames from combustion roar in the combustion chamber 44 and into the gas conduits 50 heating the same red hot. The air passing across the hot exhaust manifold 86 in the air intake manifold 90 is partially eaten. The air is further heated by passing across the combustion chamber '4 in the first air manifold 54, and is finally heated by passing through the air passages 52 between the gas conduits 50. The now extremely hot air is directed by the second air manifold 74 into the air conduits 70 of the air-to-liquid stage heat exchanger 48 where heat is transferred through the walls of the conduits 70 into the liquid. The still warm air is discharged from the air conduits 70 into the discharge manifold 80.

Liquid is circulated through the liquid jacket 64 and returned to the engine block 10. The liquid is circulated until the engine block is sufficiently heated to start the engine. However, the liquid in the inlet line 20 cannot exceed the predetermined temperature.

When such occurs, the liquid temperature sensor 128 is activated Initiating the shut down sequence of the system. The engine block and battery are thereby rapidly heated to the desired temperature for easy starting.

The heater will run until it is either turned off by manual activation of the off button 155, by sensor 136 reaching 175-F (79~X), or by a component failure opening the power relay.

Various changes can be made to the illustrated embodiments of the invention and respresentative mode of use thereof. The foregoing description is directed to the use of the invention in a heater for preheating a watercooled diesel engine. However, the heater of the invention may have many uses, for example as a combined hot water heater and forced air furnace, and the invention is not limited to heating engines.

Claims (8)

1. A liquid fuel burner comprising: a housing having a fuel inlet; a unitary porous wick member received in an opening in said housing, said wick member having a base portion and a rib portion integral with and projecting from said base portion and means for pressurising fuel within said housing above atmospheric pressure for propelling fuel through said unitary porous wick member.

2. A liquid fuel burner as claimed in claim 1, wherein said means for pressurising fuel comprises a fuel pump, having a fuel outlet in fluid-tight communication with the fuel inlet to said housing.

3. A liquid fuel burner as claimed'in claim 2, further comprising a valve having an inlet in fluidtight communication with the fuel outlet of said pump and having an outlet in fluid-tight communication with the inlet to said housing, said valve having a closure member and neans for biasing said closure member in an upstream direction to a closed position.

4. A liquid fuel burner as claimed in any preceding claim, wherein said burner further comprises a glow plug for igniting said burner.

5. A liquid fuel burner as claimed in any preceding claim, wherein said rib portion comprises a plurality of radially disposed ribs.

6. A liquid fuel burner as claimed in any of claims 1 to 5, wherein said unitary porous wick member is made from porous ceramic material.

7. A liquid fuel burner as claimed in any of claims 1 to 5, wherein said unitary porous wick member is made from porous sintered metal.

8. A liquid fuel burner constructed and adapted to operate substantially as herein described with reference to and as illustrated in the accompanying drawings.