CN202303465U

CN202303465U - High-performance combustor

Info

Publication number: CN202303465U
Application number: CN2011203272692U
Authority: CN
Inventors: 朱宏锋
Original assignee: Individual
Current assignee: Individual
Priority date: 2011-09-02
Filing date: 2011-09-02
Publication date: 2012-07-04
Anticipated expiration: 2021-09-02
Also published as: WO2013029404A1; CA2847392A1; US20140208996A1

Abstract

The utility model relates to a high-performance combustor which comprises a shell, a combustion chamber accommodated in the shell, an ignition rod arranged in the shell and a fuel conveying mechanism which passes through the shell and is communicated to the combustion chamber, wherein the combustion chamber comprises a first combustion region which is communicated with one end of a feeding pipe in the shell, a second combustion region which is closely next to the first combustion region and a third combustion region which is closely next to the second combustion region and is communicated with a rear opening on the shell. The high-performance combustor provided by the utility model can effectively alleviate the fuel congestion, avoid slag bonding, improve the combustion efficiency and effectively prevent tempering.

Description

A kind of high-performance burner

Technical field

The utility model relates to biomass fuel using energy source apparatus field, especially relevant for a kind of burner that can improve bio-fuel stove and accessory combustibility.

Background technology

The energy utilization technology of biomass fuel such as straw, wood chip, agricultural crop straw etc. is a kind of novel energy solution, and its equipment also is modified gradually and is tending towards perfect.Biomass fuel utilizes that the parts of most critical are burners in the equipment, and it is related to important performances such as capacity usage ratio, safety, flue dust, dust, fuel slagging scorification.

The inventor discloses a kind of combustion chamber of using the stove and accessory of biomass fuel in Chinese utility model CN201903077 " a kind of combustion chamber ".This combustion chamber comprises a burning groove and a fuel-feed pipe, and burning groove has a bottom surface and two sides, and the bottom surface is a plane, and two parallel sided are extended and are about 135 ° angle with the bottom surface.Offer a fire rod installing hole on the bottom surface, the length of this fire rod installing hole is basically according to the extension of the fuel side of moving.Feed pipe is provided with several air admission holes that communicate with inlet box, and the tube wall of the basic and feed pipe of these air admission hole hole bodies in vertical state.

Find that in actual use the performance of this combustion chamber also has the space of lifting.At first, the bottom surface that is a horizontal plane has basically formed bigger resistance to fuel mobile, and this resistance can make near the fuel the feed pipe outlet produce and block up, cause ingress of air insufficient, thereby produce flue dust and slagging scorification.Near the charging aperture outlet fuel blocks up and also can produce fuel in this zone and rise excessively, causes danger.The second, the air supply mode existing problems of air feed are unified in the inferior combustion zone that fuel moves main combustion zone and the downstream at the upper reaches in the burning groove, and just there is the excessive problem of air quantity in the completion of the inferior combustion zone air output that can satisfy main combustion zone needs is close to to(for) power conversion.The excessive air quantity in inferior combustion zone will cause dust.The 3rd, several hole bodies that communicate with inlet box that are provided with on feed pipe air admission hole vertical with the feed pipe tube wall is for preventing that flame from fleeing in feed pipe promptly to prevent that the function of tempering is still perfect inadequately.Find that in actual use this structural design is difficult for reaching anti-backfire purpose.

Summary of the invention

The utility model technical problem to be solved provides the employed burner of a kind of bio-fuel stove and accessory, and it is more smooth and easy that this burner can make fuel move.

The utility model another technical problem to be solved provides the employed burner of a kind of bio-fuel stove and accessory, and this burner can not produce fuel and rise excessive near the charging aperture outlet.

The utility model another technical problem to be solved provides the employed burner of a kind of bio-fuel stove and accessory, and this burner can be realized main, inferior combustion zone difference air feed.

The utility model technical problem to be solved provides the employed burner of a kind of bio-fuel stove and accessory, and this burner can effectively prevent tempering.

In order to solve above technical problem, the utility model provides shell and has a bottom surface, two from the bottom surface upwardly extending side plate, a top opening relative with the bottom surface, one from the bottom surface upwardly extending header board, and rear opening relative with header board.Offer a fire rod installing hole on the side plate respectively.The header board below offers an air outlet near the place, bottom surface.The fuel conveying mechanism comprises a feed pipe that from header board, passes and a rotating fuel spiral push rod that is contained in the feed pipe.Offer the window that feeds intake on the feed pipe on the tube wall of shell with exterior portions; Shell has a discharging opening with interior part and on tube wall, offers several feed pipe wind pushing holes of lining up at least one circle, and the hole body of each feed pipe wind pushing hole all tilts towards the direction of combustion chamber.The combustion chamber comprise one with feed pipe on first combustion zone that is connected with an interior end of shell, second combustion zone that is right after first combustion zone, the 3rd combustion zone that is right after second combustion zone and is connected with rear opening on the shell.First combustion zone comprises that first base plate of a basic horizontal, two blocks of first tilting side plates, one are from upwardly extending first header board of first base plate and the first top opening relative with first base plate.Discharging opening passes first header board makes feed pipe be communicated with first combustion zone.Distance between two first side plates is basic identical at the width of discharging opening place and discharging opening, along increasing gradually from first combustion zone to the second combustion zone direction width.On first base plate, offer a fire rod window, on the position between fire rod window and the discharging opening, offering at least one air draft screen wind pushing hole on first base plate perpendicular to feed pipe.Second combustion zone comprises second base plate of the downward-sloping extension of edge first base plate and the second top opening relative with second base plate.The 3rd combustion zone comprises that one the 3rd base plate, one extend upward the preceding riser to second base plate, a back riser and three a top opening relative with the 3rd base plate that extends downward the bottom surface from the 3rd base plate from the 3rd base plate.Be provided with preceding upper cover plate between the header board and first header board, be equipped with a side upper cover plate between every block of side plate of every first side plate and homonymy.Also be installed with a split-wind plate that in shell, extends on the header board; Split-wind plate comprises a horizontal component and a last oblique part; Horizontal component traverses air outlet; Make the above area of horizontal component in the area of whole air outlet be about 2 times of following the area of horizontal component, a free end of going up tiltedly partly points to the joint between first base plate and second base plate.On the direction of air outlet, has a windscreen that is installed on first base plate in the fire rod lower end.The both sides of second combustion zone respectively are provided with second side plate that ability is high temperature resistant.Above the first header board top discharge mouth, be installed with a following inclined plate.

The beneficial effect that the utility model brought comprises; First; Compare with traditional air vent perpendicular to tube wall, head-on confrontation no longer takes place, the speed of cancelling out each other in the high wind that from the feed pipe wind pushing hole of several inclinations, comes out in any relative two; Thereby form powerful wind screen to greatest extent, prevent that the ability of tempering is able to remarkable increase.Second; Owing to the distance between two first side plates is basic identical at the width of discharging opening place and discharging opening; So compare with traditional parallel side plate structure, can not exist a fuel to be difficult for the dead angle that is moved ahead by follow-up fuel promotion in the junction of discharging opening both sides and side plate.The efficiency of combustion of fuel can improve, and the slagging scorification phenomenon can reduce.The 3rd; Only need short burning time and more a spot of air just can discharge most dump energy at the first combustion zone spent fuel; The second downward-sloping base plate both can alleviate this regional fuel to the blocking up of the first combustion zone fuel, and also can accelerate the preceding line speed of this regional fuel.Efficiency of combustion and slagging scorification phenomenon can further be improved again.The 4th; Can still have the energy of few part can supply burning at the second combustion zone spent fuel; When dropping on the 3rd base plate when the fuel gravitate, energy remaining both can discharge in the 3rd combustion zone and finish, and ashes can not exert an influence to the fuel in first and second combustion zones yet simultaneously.Efficiency of combustion and slagging scorification phenomenon are farthest improved.The 5th; Because the existence of split-wind plate; The big portion air quantity that accounts for 2/3 flow is used to supply with feed pipe wind pushing hole, wind screen wind pushing hole and first combustion zone that needs high wind and a large amount of oxygen, and little the air quantity that accounts for 1/3 flow is used to supply with the second and the 3rd combustion zone that only needs minor amounts of oxygen.Burn insufficient and the phenomenon of the excessive generation dust of combustion zone, rear portion air feed with regard to the anterior combustion zone air feed deficiency of having avoided producing under traditional average air feed situation like this.The 6th, rise excessive phenomenon of fuel that place, first combustion zone is easy to generate has effectively been suppressed in the existence of following inclined plate, has reduced the danger during burner uses.

Description of drawings

Fig. 1 is a schematic perspective view of the utility model preferred embodiment.

Fig. 2 is another schematic perspective view embodiment illustrated in fig. 1.

Fig. 3 is a three-dimensional exploded perspective view embodiment illustrated in fig. 1.

Fig. 4 is a side view embodiment illustrated in fig. 1.

Fig. 5 is the cutaway view of A-A direction among Fig. 4.

Fig. 6 is for being a vertical view embodiment illustrated in fig. 1.

Fig. 7 is the cutaway view of B-B direction among Fig. 6.And,

Fig. 8 is the local enlarged diagram for C part among Fig. 5.

The specific embodiment

With reference to figure 1, Fig. 2 and Fig. 3, it shows a kind of preferred embodiment of the employed high-performance burner of a kind of bio-fuel stove and accessory of the utility model.This burner comprises that 2, one of the combustion chambers that 1, one on a shell is contained in the shell 1 are installed in the fire rod 3 in the shell 1, and one is passed shell 1 and is communicated to the fuel conveying mechanism 4 in the combustion chamber 2.

Shell 1 have 10, two of bottom surfaces from the bottom surface 12, one of relative top openings in 11,11 ', one of 10 upwardly extending side plate and bottom surface 10 from the bottom surface 10 upwardly extending header boards 13, and rear opening 14 relative with header board 13.Offer a fire rod installing hole 110,110 ' respectively on the

side plate

11,11 '.Header board 13 belows offer an air outlet 130 near 10 places, bottom surface, and the airduct (not shown) of air blast can insert air outlet 130, air blast in shell 1.

Further with reference to figure 5 and Fig. 7, fuel conveying mechanism 4 comprises a feed pipe 40 that from the header board 13 of shell 1, passes and a rotating fuel spiral push rod 41 that is contained in the feed pipe 40.Offer the window 42 that feeds intake on the feed pipe 40 on the tube wall of shell 1 with exterior portions, shell 1 has a discharging opening 43 and on tube wall, offers several feed pipe wind pushing holes 44 of lining up at least one circle with interior part.With reference to shown in Figure 8, all 2 direction tilts the hole body of each feed pipe wind pushing hole 44 towards the combustion chamber.The diameter of each feed pipe wind pushing hole 44 can be between the 3-5 millimeter, and preferable is about 3.5 millimeters; In this preferred embodiment, offer two circle feed pipe wind pushing holes 44 on the feed pipe 40, feed pipe wind pushing hole 44 quantity that every circle can comprise can be 10-20, and preferable is 16.The diameter of feed pipe 40 can be between the 80-100 millimeter, preferably about 90 millimeters.

Further with reference to figure 7; Combustion chamber 2 comprise one with feed pipe 40 on first combustion zone 21 that is connected with an interior end of shell 1; The 3rd combustion zone 23 that 22, one of second combustion zone that are right after first combustion zone 21 is right after second combustion zone 22 and is connected with rear opening 14 on the shell 1.First combustion zone 21 comprises that the first tilting side plate 212 of first base plate 211, two of a basic horizontal, 212 ', one are from first base plate, 211 upwardly extending first header boards 213 and the first top opening 214 relative with first base plate 211.Discharging opening 43 passes first header board 213 makes feed pipe 40 be communicated with first combustion zone 21.Two first side plates 212, the distance between 212 ' are basic identical at the width of discharging opening 43 places and discharging opening 43, along increasing gradually from first combustion zone 21 to second combustion zone, 22 direction width.First base plate 211 can be the 80-150 millimeter, preferably about 120 millimeters from the length discharging opening 43 to second combustion zones 22.Simultaneously with reference to figure 5; On first base plate 211, offer a fire rod window 215 perpendicular to feed pipe 40 apart from discharging opening (43) 20-40 millimeter, preferable about 25 millimeters places; About 10 millimeters of the width of fire rod window 215, length is through two first side plates 212, between 212 '.On first base plate 211, on the position between fire rod window 215 and the discharging opening 43, offer at least one air draft screen wind pushing hole 216.

Second combustion zone 22 comprises second base plate 221 of an edge first base plate, 211 downward-sloping extensions and the second top opening 222 relative with second base plate 221.Second base plate 221 can be 8 °-30 ° with respect to first base plate, 211 downward-sloping angles, and preferable is about 17 °.The 3rd combustion zone 23 comprises that one the 3rd base plate 231, one extend upward the back riser 233 that extends downward bottom surface 10 to the preceding riser of second base plate 221 232, one from the 3rd base plate 231 and one the three top opening 234 relative with the 3rd base plate 231 from the 3rd base plate 231.Second base plate 221 can be the 60-130 millimeter from first base plate 211 to the length the preceding riser 232, preferably about 100 millimeters.The height of preceding riser 232 can be the 80-150 millimeter, preferably about 120 millimeters.The 3rd base plate 231 riser 232 in the past can be the 80-150 millimeter, preferably about 120 millimeters to the length between the riser 233 of back.The width of second base plate 221, the 3rd base plate 231, preceding riser 232, back riser 233 can be the 80-120 millimeter, preferably about 100 millimeters.First, second, third top opening, 214,222, the 234 common flame exports that form.Between the fire rod window 215 on first base plate 211 and second base plate 221, on second base plate 221, also all offer several oxygen wind pushing holes 217 on the 3rd base plate 231.The diameter of these oxygen wind pushing holes 217 can be the 2-4 millimeter, preferably about 3.5 millimeters.

Upper cover plate 15 before being provided with between the header board 13 and first header board 213, every first side plate 212,212 ' and every block of side plate 11 of homonymy, be equipped with a side upper cover plate 16,16 ' between 11 '.The bottom surface 10 of shell 1, side plate 11,11 ', header board 13; Before upper cover plate 15, side upper cover plate 16,16 ' and first header board, 213, the first side plates 212,212 ' of combustion chamber 2; First base plate, 211, the second base plates, 221, the three base plates 231; Preceding riser 232, back riser 233 surround an air blast zone 17 jointly.Also be installed with a split-wind plate 18 that in shell 1, extends on the header board 13, split-wind plate 18 comprises a horizontal component 181 and a last oblique part 182.Horizontal component 181 traverses air outlet 130, makes the area of horizontal component more than 181 in the area of whole air outlet 130 be about 2 times of the following area of horizontal component.The free end of going up oblique part 182 points to the joint between first base plate 211 and second base plate 221.

On the direction of air outlet 130, can provide a windscreen 30 that is installed on first base plate 211 in fire rod 3 lower ends, with the high wind influence igniting that prevents to come out from air outlet 130.Can provide a back upper cover plate 19 that is installed on the shell 1 at 234 places of opening above in the of the 3rd, its 21,22 places, first and second combustion zones of can the heat that 23 places, the 3rd combustion zone produce being led are to improve the utilization rate of heat energy.Because the temperature of second combustion zone 22 is higher, can respectively adds high temperature resistant second side plate 223,223 ' of ability in the both sides of second combustion zone 22 and at high temperature deform with the shell 1 that prevents this part.Second side plate 223,223 ' can be pottery or stainless steel materials.Above first header board, 213 top discharge mouths 43, be installed with a following inclined plate 218, it is excessive that it can prevent effectively that fuel from rising, thereby improve the security that burner uses.

In use; The user can energized opens the switch of stove and accessory; Graininess bio-fuel (all not showing among the figure) in the hopper falls into feed pipe 40 through the window 42 that feeds intake under the gravity effect; Under the promotion of fuel spiral push rod 41, get into first combustion zone 21, drop on first base plate 211 through discharging opening 43.Fire rod 3 energisings this moment become red-hot, with ignited fuel; Air blast is blown to air blast zone 17 through air outlet 130 simultaneously.Wind above the split-wind plate 18 is mainly through feed pipe wind pushing hole 44, wind screen wind pushing hole 216 and the 217 entering combustion chambers 2 of the oxygen wind pushing hole above first base plate 211; And the wind below the split-wind plate 18 is main through second base plate 221 and the top oxygen wind pushing hole 217 entering combustion chambers 2 of the 3rd base plate 231, for the burning of fuel provides required oxygen.The powerful wind screen that can stop fuel combustion can be formed from the air of feed pipe wind pushing hole 44 and wind screen wind pushing hole 216 entering combustion chambers 2, thereby the fuel combustion in the feed pipe 40, promptly so-called tempering phenomenon can be prevented.Compare with traditional air vent perpendicular to tube wall; Head-on confrontation no longer takes place in the high wind that from the feed pipe wind pushing hole 44 of several inclinations, comes out in any relative two; The speed of cancelling out each other, thus powerful wind screen formed to greatest extent, prevent that the ability of tempering is able to remarkable increase.In addition; Because two first side plates 212, the distance between 212 ' are basic identical at the width of discharging opening 43 places and discharging opening 43; So compare with traditional parallel side plate structure, can not exist a fuel to be difficult for the dead angle that is moved ahead by follow-up fuel promotion in the junction of discharging opening 43 both sides and side plate.The efficiency of combustion of fuel can improve, and the slagging scorification phenomenon can reduce.And two first side plates 212, the distance edges between 212 ' increase from first combustion zone 21 to second combustion zone, 22 direction width gradually; Then reduced when fuel moves ahead in traditional parallel lateral plate structure frictional force again effectively by side plate produced; Fuel blocks up and alleviates, and efficiency of combustion and slagging scorification phenomenon are further improved.

21 spent fuels only need short burning time and more a spot of air just can discharge most dump energy in first combustion zone.The second downward-sloping base plate 221 both can alleviate this regional fuel to the blocking up of first combustion zone, 21 fuel, and also can accelerate the preceding line speed of this regional fuel.Efficiency of combustion and slagging scorification phenomenon can further be improved again.22 spent fuels can still have the energy of few part can supply burning in second combustion zone; Drop on 231 last times of the 3rd base plate when the fuel gravitate; Energy remaining both can discharge in the 3rd combustion zone 23 and finish, and ashes can not exert an influence to the fuel in first and second combustion zones 21,22 yet simultaneously.Efficiency of combustion and slagging scorification phenomenon are farthest improved.Because the existence of split-wind plate 18; The big portion air quantity that accounts for 2/3 flow is used to supply with feed pipe wind pushing hole 44, wind screen wind pushing hole 216 and first combustion zone 21 that needs high wind and a large amount of oxygen, and little the air quantity that accounts for 1/3 flow is used to supply with the second and the 3rd combustion zone 22,23 that only needs minor amounts of oxygen.Burn insufficient and the phenomenon of the excessive generation dust of combustion zone, rear portion air feed with regard to the anterior combustion zone air feed deficiency of having avoided producing under traditional average air feed situation like this.Fuel that first combustion zone 21 places the are easy to generate excessive phenomenon that rises has effectively been suppressed in the existence of following inclined plate 218, has reduced the danger during burner uses.

Such as those skilled in the art knowledge, accompanying drawing of the utility model and embodiment are merely function, structure and the principle of explanation the utility model and should become the restriction on the utility model understood; Simultaneously, the purpose of the utility model all realizes.The foregoing description possibly had some change under the situation that does not break away from the utility model principle, so the protection of the utility model should be as the criterion with the scope described in claims.

Claims

1. high-performance burner; It is characterized in that comprising a shell (1), a combustion chamber (2) that is contained in the shell (1), a fire rod (3) that is installed in the shell (1); And one passed shell (1) and be communicated to the fuel conveying mechanism (4) in the combustion chamber (2)

Shell (1) has a bottom surface (10); Two from the bottom surface (10) upwardly extending side plate (11,11 '), a top opening (12) relative with bottom surface (10), one from the bottom surface (10) upwardly extending header board (13); And rear opening (14) relative with header board (13); Offer a fire rod installing hole (110,110 ') on the side plate (11,11 ') respectively, an air outlet (130) is located to offer near bottom surface (10) in header board (13) below

Fuel conveying mechanism (4) comprises a feed pipe (40) that from header board (13), passes and a rotating fuel spiral push rod (41) that is contained in the feed pipe (40); Feed pipe (40) is gone up on the tube wall of shell (1) with exterior portions and is offered the window that feeds intake (42); Shell (1) has a discharging opening (43) with interior part and on tube wall, offers several feed pipe wind pushing holes (44) of lining up at least one circle; All the direction of (2) tilts the hole body of each feed pipe wind pushing hole (44) towards the combustion chamber

Combustion chamber (2) comprises first combustion zone (21) that is connected with an interior end with the last shell (1) of feed pipe (40); Second combustion zone (22) that is right after first combustion zone (21); The 3rd combustion zone (23) that is right after second combustion zone (22) and is connected with rear opening (14) on the shell (1)

First combustion zone (21) comprises first base plate (211) of a basic horizontal; Two blocks of first tilting side plates (212; 212 '); One from upwardly extending first header board of first base plate (211) (213); And the first top opening (214) relative with first base plate (211); Discharging opening (43) passes first header board (213) makes feed pipe (40) be communicated with first combustion zone (21); Two first side plates (212; 212 ') distance between is located with the width of discharging opening (43) basic identical at discharging opening (43); Along increasing gradually to second combustion zone (22) direction width from first combustion zone (21); On first base plate (211), offer a fire rod window (215) perpendicular to feed pipe (40); Upward on the position between fire rod window (215) and the discharging opening (43), offer at least one air draft screen wind pushing hole (216) at first base plate (211)

Second combustion zone (22) comprises second base plate (221) of the downward-sloping extension of edge first base plate (211) and the second top opening (222) relative with second base plate (221),

The 3rd combustion zone (23) comprises that one the 3rd base plate (231), one extend upward the preceding riser (232) to second base plate (221), a back riser (233) and three a top opening (234) relative with the 3rd base plate (231) that extends downward bottom surface (10) from the 3rd base plate (231) from the 3rd base plate (231)

Be provided with preceding upper cover plate (15) between header board (13) and first header board (213), be equipped with a side upper cover plate (16,16 ') between every block of side plate (11,11 ') of every first side plate (212,212 ') and homonymy,

Also be installed with a split-wind plate (18) that in shell (1), extends on the header board (13); Split-wind plate (18) comprises a horizontal component (181) and one upward oblique partly (182); Horizontal component (181) traverses air outlet (130); Make the above area of horizontal component (181) in the area of whole air outlet (130) be about 2 times of following the area of horizontal component, going up tiltedly partly, a free end of (182) points to the joint between first base plate (211) and second base plate (221)

On the direction of air outlet (130), have a windscreen (30) that is installed on first base plate (211) in fire rod (3) lower end,

The both sides of second combustion zone (22) respectively are provided with second side plate (223,223 ') that ability is high temperature resistant,

Be installed with a following inclined plate (218) in the top of first header board (213) top discharge mouth (43).

2. high-performance burner as claimed in claim 1; The diameter that it is characterized in that each feed pipe wind pushing hole (44) is between the 3-5 millimeter; Feed pipe wind pushing hole (44) quantity that every circle comprises is 10-20; The diameter of feed pipe (40) is between the 80-100 millimeter, and first base plate (211) is the 80-150 millimeter from discharging opening (43) to the length second combustion zone (22), and fire rod window (215) is apart from discharging opening (43) 20-40 millimeter; Second base plate (221) angle downward-sloping with respect to first base plate (211) is 8 °-30 °; Second base plate (221) is the 60-130 millimeter from first base plate (211) to the length the preceding riser (232), and the height of preceding riser (232) is the 80-150 millimeter, and the 3rd base plate (231) riser (232) in the past is the 80-150 millimeter to the length between the back riser (233); The width of second base plate (221), the 3rd base plate (231), preceding riser (232), back riser (233) is the 80-120 millimeter, and the diameter of oxygen wind pushing hole (217) is the 2-4 millimeter.

3. high-performance burner as claimed in claim 2, the diameter that it is characterized in that each feed pipe wind pushing hole (44) are about 3.5 millimeters; Feed pipe wind pushing hole (44) quantity that every circle comprises is 16; The diameter of feed pipe (40) is about 90 millimeters; First base plate (211) is about 120 millimeters from discharging opening (43) to the length second combustion zone (22); About 25 millimeters of fire rod windows (215) apart from discharging opening (43); The width of fire rod window (215) is about 10 millimeters, and second base plate (221) angle downward-sloping with respect to first base plate (211) is about 17 °, and second base plate (221) is about 100 millimeters from first base plate (211) to the length the preceding riser (232); The height of preceding riser (232) is about 120 millimeters; The 3rd base plate (231) riser (232) in the past is about 120 millimeters to the length between the back riser (233), and the width of second base plate (221), the 3rd base plate (231), preceding riser (232), back riser (233) is about 100 millimeters, and the diameter of oxygen wind pushing hole (217) is about 3.5 millimeters.