SWIRL-PINTLE INJECTOR FOR OXY-COAL COMBUSTOR

BACKGROUND

The abundant availability of coal globally and its energy density make it particularly attractive for fossil power generation. However, the environmental impact of fossil fuels questions the feasibility of coal in the future power generation system. Coupled with climate restrictions, the constant need for power practically demands a highly efficient carbon-neutral coal power generation system. A realistic solution to this problem is a high-pressure oxy-coal combustion system.

Pressurized oxy-coal combustion systems can achieve high thermal efficiency along with near-zero carbon emission. Several studies have delineated the economic feasibility of these combustion systems. Pressurizing the system increases flue gas density, which increases the energy density per unit of the working fluids. Theoretically, higher thermal output and efficiency can be achieved by recovering the latent heat of steam. Besides, the increase in energy density allows for downsizing the turbomachinery footprint and reduce capital cost.

Furthermore, the NO_x-free high-pressure oxy-combustion enables up to 100% carbon capture. Since the CO₂in the exhaust is highly pure and pressurized, minimal processing is required, thereby permitting a less extensive carbon capture system. These proposed combustion systems operate at pressures between 10 to 80 bar.

The realization of the pressurized oxy-coal based systems require combustor components to be designed and demonstrated for an operating pressure above 10 bar. However, pressurized oxy-coal combustor design information at this pressure range is currently limited. A key component to accomplish the proposed oxy-coal combustion systems is the burner. In general, swirl burners are widely used in the pulverized coal combustion process and provide superior flame stability, high conversion rate, and low pollutant emission characteristics.

SUMMARY

A coaxial pintle injector with different swirls was investigated in this study. Coal-Water slurry with varying coal weight percentages was used as fuel. Two different swirl numbers (0.9 and 1.2) were investigated and compared with no swirler cases. High-speed shadowgraph technique was used to capture the atomization scenarios, and later the pictures were used to analyze their effects. The largest swirl creates the most significant number of particles. Including swirlers into the injector reduces the droplet sizes by 70%. Also, swirlers reduce the jet breakup lengths significantly compared to the no swirler case. Jet travel length is almost 57% smaller before secondary atomization zone for S=1.2 compared to S=0. This indicates a bigger swirler will have a smaller flame length and more space for flame development. Increasing swirler number results in higher momentum in oxidizer streams. Swirl decreases the TMR, which results in more uniform penetration and better atomization. Embodiments of the swirl feature can induce a swirl motion in the flow to improve mixture of combustion reactants, help anchor the combustion flame, and reduce probability of flame extinction.

There is a need for the following embodiments of the present disclosure. Of course, the present disclosure is not limited to these embodiments.

According to an embodiment of the present disclosure, an apparatus comprises: a main body comprising at least one gas inlet; a pintle coupled to the main body, wherein the pintle comprises at least one coal slurry inlet and at least one slurry outlet, wherein the pintle defines a pintle axis; and a swirler coupled to the main body, wherein the swirler imparts to a gas from the at least one gas inlet of the main body a circular motion around the pintle axis, wherein the swirler surrounds the pintle axis and comprises a plurality of vanes, wherein each of the plurality of vanes is configured at a flow turning angle φ and wherein the swirler defines a swirl number S of approximately 1.2 according to S=⅔ tan φ. In a preferred embodiment the pintle comprises a plurality of pintle tip orifices of approximately 5 mm diameter.

According to another embodiment of the present disclosure, a method of operating a pintle injector comprises: providing a coal slurry from a pintle of the pintle injector, wherein the pintle defines a pintle axis, wherein the coal slurry comprises a combustible phase and a liquid phase; providing oxygen to a main body of the pintle injector; then conveying the oxygen through a swirler of the pintle injector to impart to the oxygen a circular motion around the pintle axis, wherein the swirler surrounds the pintle axis and comprises a plurality of vanes, wherein each of the plurality of vanes is configured at a flow turning angle φ and wherein the swirler defines a swirl number S of approximately 1.2 according to S=⅔ tan φ; and then reacting the coal slurry from the pintle with the oxygen. In a preferred embodiment, the pintle comprises a plurality of pintle tip orifices having a diameter of approximately 5 mm.

These, and other, embodiments of the present disclosure will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following description, while indicating various embodiments of the present disclosure and numerous specific details thereof, is given for the purpose of illustration and does not imply limitation. Many substitutions, modifications, additions and/or rearrangements may be made within the scope of embodiments of the present disclosure, and embodiments of the present disclosure include all such substitutions, modifications, additions and/or rearrangements.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings accompanying and forming part of this specification are included to depict certain embodiments of the present disclosure. A clearer concept of the embodiments described in this application will be readily apparent by referring to the exemplary, and therefore nonlimiting, embodiments illustrated in the drawings (wherein identical reference numerals (if they occur in more than one view) designate the same elements). The described embodiments may be better understood by reference to one or more of these drawings in combination with the following description. It should be noted that the features illustrated in the drawings are not necessarily drawn to scale.

FIG. 1 is a cross sectional view of a pintle injector component.

FIGS. 2A-2B are isometric views of a swirler plate and a swirler vane.

FIG. 3 is a schematic view of a fluid delivery system.

FIG. 4 is a schematic view of a shadowgraph set-up.

FIGS. 5A-5C are shadowgraph images for 30% Coal-70% Water of (FIG. 5A) Test 1 (S=0), (FIG. 5B) Test 2 (S=0.9), (FIG. 5C) Test 3 (S=1.2).

FIG. 6 shows mean equivalent diameter of the slurry lumps for different weight % coal mixtures.

FIGS. 7A-7C show droplet size distribution for (FIG. 7A) S=0, (FIG. 7B) S=0.9, (FIG. 7C) S=1.2.

FIGS. 8A-8B show a demonstration of jet breakup length measurement technique with test 3 (S=1.2).

FIGS. 9A-9B show spray angle measurement for (FIG. 9A) Test 4 (S=0.9), (FIG. 9B) Test 7 (S=1.2).

FIG. 10 is a cross sectional view of an injector product.

FIG. 11 is an isometric view of a first example closing plate with swirler.

FIG. 12 is an isometric view of an injector body.

FIG. 13 is an isometric view of a first example injector tip based on a threaded tip.

FIGS. 14A-14B are exploded views of the injector product, with subsystems (a) body with pintle post welded, (b) distribution plate, (c) swirler plate, and (d) pintle tip.

FIG. 15 is an isometric view of the injector product.

FIG. 16 is a cross sectional view of the injector product.

FIG. 17 is an isometric view of a second example closing plate with swirler.

FIG. 18 is an isometric view of a second example of an injector tip based on a pipe tip.

FIG. 19 is an isometric view of the injector body.

FIG. 20 is an exploded view of the injector product including the second example closing plate with swirler, with subsystems: (4) body with pintle post welded, (5) distribution plate, (3) swirler plate.

FIG. 21 is an isometric view of the pintle injector product with the second example closing plate.

FIGS. 22A-22C show Jet Break Up Length for Different Slurry Ratios.

FIGS. 23A-23C show Spray angle measurement for (a) test (30/70)₀, (b) test (30/70)_0.9, (c) test (30/70)_1.2.

FIGS. 24A-24F show qualitative particle size analysis using shadowgraph technique swirl for 30/70 slurry ratio (a FIGS. 24A-24B) (30/70)_{0.0 swirl}(b FIGS. 24C-24D) (30/70)_{0.9 swirl}(c FIGS. 24E-24F) 30/70)_{1.2 Swirl}.

DETAILED DESCRIPTION

Burner design and operating characteristics at elevated combustion pressure need to be evaluated. The current study proposes to use a swirl-pintle burner. Pintle burners are widely used in rocket propulsion and the automotive industry and have spectacular combustion efficiency. Although pintle burners have a scintillating track record operating with liquid fuels, limited information is available for solid-liquid bipropellant operation. The current investigation aims to design and characterize the burner for water-coal slurry mixture operation. The water-coal slurry mixture enables increased thermal output by recovering the steam's latent heat from the flue gas. Additionally, during operation, the vaporized water assists in system pressurizing. Incorporating swirlers with a pintle burner is projected to increase atomization, increasing flame stability, and increases ignition stability.

Motivated by the advantages, the current study prototypes a swirl-pintle burner for a high-pressure oxy-coal combustion system. This investigation's primary goal is to identify the optimum operating parameters of the swirl-pintle burner, operating with solid-liquid bipropellant (i.e., coal-water slurry). One of the major focuses is understanding the jet characteristics of the swirl-pintle burner for the current fuel. Another fundamental interest is to investigate the effect of swirlers on atomization and jet parameters. The outcome of this investigation will play a key role in designing the high-pressure combustor and identify operating conditions.

Pintle Injector

Referring to FIG. 1, a pintle injector component 100 is illustrated. The pintle injector component 100 includes main body 110. Pintle post 120 passes through main body 110. Distribution plate 130 is coupled to main body 110. Closing plate 140 is connected to main body 110 and distribution plate 130. Pintle tip 150 is coupled to pintle post 120.

In operation, water coal slurry 170 passes through pintle post 120. The water coal slurry 170 exits pintle post 120 via pintle tip orifices in pintle tip 150 that discharge water coal slurry 170 in a direction away from the pintle tip 150 shown by the horizontal arrows of FIG. 1. Meanwhile, a nitrogen oxidizer gas mixture 180 passes through main body 110, then through distribution plate 130, and then through closing plate 140. The nitrogen oxidizer gas mixture can include pure oxygen. The nitrogen oxidizer gas mixture can include preheated air.

For the first generation design, the modularity of the injector was a key feature. FIG. 1 shows the first-generation design. It includes the main body 110, pintle post 120, distribution plate 130, closing plate 140 and pintle tip 150. The main body 110 and the pintle post 120 are welded, whereas all the other parts can be removed. The benefit of a modular design is to test different configurations for the tip and the distribution plate. The slurry is fed through the pintle post and is delivered radially through the pintle tip. The gaseous fuel is delivered axially. The interaction of the two streams creates an atomized spray at the impingement point.

For the second-generation injectors, modifications are made in the design, and now it has only a modular tip. This ensures that the tip can be removed and cleaned in case of any clog. For these tests, a 5 mm orifice-sized tip is used. All the other parts are fixed. A second port has been introduced in the injector to gain stable atomization on all sides. For testing, the mass flow is calculated to ensure that the second port does not create additional propellant flux.

Swirlers are added in second and third-generation designs. The swirlers are welded onto the closing plate, as shown in FIGS. 2A-2B. The swirl number represents the amount of swirl imparted to the flow by the vane swirl angle. It is defined as the ratio of the axial flux of swirl momentum to that of axial momentum. The swirl number can be found using,

S=—⅔ tan φ (1)

The ratio of nozzle diameter to vane pack diameter in preferred embodiments is small to very small (e.g. 0.5 to 0.05). Here φ represents the blade angle, and a minimal blade angle increases swirl number. Swirl numbers of 0.9 and 1.2 are chosen for investigation as increased swirl flow promotes stabilized reaction zone.

Referring to FIGS. 2A-2B, a swirler plate 210 is illustrated in FIG. 2A and a swirler vane 250 in FIG. 2B. Swirler plate 210 includes 8 swirler vanes. Of course, embodiments of this disclosure can include more or fewer swirler vanes. Swirler vane 250 includes an air-foil shape. Of course, embodiments of this disclosure can include vanes with other shapes.

In this embodiment, the swirler is hubless. Consequently, there is no need for bearings. However, embodiments of this disclosure are not limited to a hubless swirler; and the swirler can be coupled to a hub that is coupled to the body to enable rotation (passive or driven) of the swirler relative to the body around an axis of rotation that is coaxial with the pintle post. In this embodiment, eight identical stainless steel vanes constitute each swirler. The nominal NACA 2430 model is used for the air-foil vanes. The chord width is 0.63 inches, and the camber radius is 0.522 inches. Angle of attack of zero degree to the flow path is used. The flow turning angle is 53° and 60.9° for injectors having swirl numbers of 0.9 and 1.2, respectively. Thus, three pintle injectors with no swirl, 0.9 swirl and 1.2 swirl are investigated here. However, embodiments of this disclosure are not limited to these swirl numbers, and the swirl number can be, for example, within a range of from approximately 0.7 to approximately 1.4, preferably within a range of from approximately 0.9 to approximately 1.2.

Experimental Setup

Referring to FIG. 3, a schematic of a fluid delivery system 300 is illustrated. The fluid delivery system 300 includes pintle injector 310 which can be tested in the context of fluid delivery system 300.

The experimental setup includes pintle injector 310, feed delivery, mixer, pump, and shadowgraph setup. Three injectors with different swirl conditions are tested. The injectors are swapped in the same setup to test their performance. The gaseous delivery system includes oxidizer lines. For the cold flow test, nitrogen has been used instead of oxygen to observe atomization. Pressure transducers and flow meters are added to monitor the flow. Pulverized coal is used in slurry form. The maximum powder size to be tested is 800 μm. The mixer includes a shaft with propellers to keep the slurry homogenous for the test's duration. It is set at an angle of 30° to prevent the accumulation of coal in parts of the container. A progressive cavity pump is used to deliver the slurry to the injector. A pressure transducer is added, right before delivery, to monitor slurry flow.

Shadowgraphy

Referring to FIG. 4, a schematic of a shadowgraph set up 400 is illustrated. The shadowgraph set up 400 includes a high speed camera 410 on one side of a test article 420 opposite a light diffuser 430 and light source 440.

Shadowgraphy is a high-resolution imaging technique that traces shadows to determine the size and frequency of objects. A high-speed camera is used in the system to capture the formation of droplets from the spray. The jet break up length, number and size of droplets can be identified using this technique. The setup is shown in FIG. 4. The test article is placed in the middle. A high-intensity light source is placed on one side of it, and a high-speed camera is placed on the other side. A light diffuser is placed in front of the light source to create a uniform lighting environment. A commercial software, DynamicStudio, analyzes the acquired images to get information on the droplets. The user-defined grey level profile identifies the droplets. So, the profile of the droplets is identified based on the light intensity as selected by the user. Thus, using shadowgraphy velocity, diameter and amount of droplets were identified.

Test Cases

For the tests, the ratio of water to coal was kept constant. A slurry containing 30% coal and 70% water by mass was chosen. The test matrix was designed to collect data on the performance of the pintle and the system's different concentrations of the mixture. After several trials, a tip with a 5 mm orifice size was chosen to get the best output from the experimental setup. Different nitrogen flows were tested to compare Total Momentum Ratios. Since nitrogen gas properties closely resemble oxidizer gas, in preferred embodiments the oxidizer will follow the same pattern in results for the hot fire test. This yielded different spray angles, diameters, and overall atomization.

The following Table 1 summarizes the different test cases for this study.

TABLE 1

Test Matrix

Mixture
Slurry
Nitrogen

Ratio
Mass
Mass

(w/w)%
Flow
Flow

Swirl Number
Test Points
(Coal/Water)
(kg/s)
(kg/s)

0 (No
1
30/70
0.081
0.0265

Swirler)
2
40/60
0.082
0.0267

3
50/50
0.085
0.0260

0.9
4
30/70
0.069
0.0224

5
40/60
0.068
0.0222

6
50/50
0.066
0.0234

1.2
7
30/70
0.065
0.0149

8
40/60
0.065
0.0145

9
50/50
0.068
0.0141

Results

The investigation is part of a project to fabricate an efficient combustor on a commercial scale. A novel injection technology is used to spray coal-water slurry and pure oxygen. Pure oxygen is intended to mean readily commercial or industrially available (e.g. welding gas) purity. Combustion is considered efficient when burnt fuel to input fuel ratio is high. The water in coal-water slurry gives it a similitude to liquid characteristics. Like liquid when injected, coal-water slurry also creates a continuous stream. For efficient combustion, atomization is necessary. Maximum burning needs to be ensured by exposing the maximum number of particles to the combustion environment. The high number of small particle generation is necessary for high efficiency. Coal-Water slurry is a highly viscous, non-Newtonian and two-phase liquid. The rheological properties of it make it harder to atomize and prone to clogging the orifice. To overcome these difficulties, injection velocities are increased, and turbulence is introduced.

In this study, pure oxygen is used as an oxidizer. Oxygen streams are injected into the combustion chamber, hitting the slurry stream co-axially. The collision creates detachment of coal particles from the water stream. These suspending particles then enter the combustion environment and burn. This investigation looked into the potentials of swirler inclusion into the injector system. Two different sets of swirler were tested with swirler numbers, S=0.9, 1.2. They were compared to S=0, or no swirler injection.

Jet breakup lengths were investigated with different swirlers. It is one of the most quantified characteristics in the studies of atomization. Since this project's ultimate objective is to introduce this injection technology into commercial plants, offering the choice of compact burner design is desirable. Hence the jet breakup lengths were studied as they will indicate the flame length.

Slurries with different densities were investigated with the swirlers. Swirlers performances were observed for different mixture ratios in the input slurry. Three different mixture ratios were investigated. Percentages of coal in the mixtures were 30, 40, 50 by weight. The test cases are shown in Table 1.

A. Effects of Swirlers on Particle Number:

When the oxidizer stream penetrates the slurry stream, crushed coal particles will detach from the slurry stream. These particles are covered with water layers. A high number of smaller particles are desired as it will expose more surface area to the flame. The heat of the environment vaporizes the water layer, and the oxidizer can reach the coal particle. Only then burning happens. Since the suspending particles move through high pressure and high-velocity environments, exposure to the flame will be limited. Hence smaller particles can ensure efficient consumption of the input fuel.

Table 2 lists different parameters observed for comparison purposes. The number of particles and the size of the particles is listed in the table. Sizes are measured based on diameters extracted from the shadowgraph by DynamicStudio software. It can be observed that when there is no swirler, streams are mainly broken into lumps with sizes around 10 mm. When swirls are introduced, 70% smaller suspended elements were created. Particle sizes came down to around 2.5 mm.

Swirler 1.2 results in a higher number of particles than swirler 0.9. A higher swirler number essentially stands for a bigger flow turning angle and more swirl. A bigger turning angle creates more turbulence with increasing turbulence colliding surface area increases, which in turn causes more break up. As the swirler number increases by 33%, the number of particles increases almost twice. For S=0.9, more lumps are present than droplet particles.

Referring to FIGS. 5A-5C, shadowgraph images are illustrated for 30% coal-70% water slurry for (FIG. 5A) Test 1 (S=0), (FIG. 5B) Test 2 (S=0.9), (FIG. 5C) Test 3 (S=1.2). It can be appreciated that when S=1.2, more particles are visible, and uniform penetration of oxidizer can be presumed.

Viscosity is proportional to surface tension. Higher viscosity results in higher surface tension; hence to penetrate oxidizer streams require more energy. For S=0.9, 94% more particles are created for 30% C_wthan the case of 50% C_w. For S=1.2, the number of particles hikes up by 90% for lower viscosity. Even though more particles can be created at low viscosity, better results can be achieved by increasing swirler number lesser viscous slurry. The number of particles for S=0.9 and 30% C_wis almost equal to S=1.2 and 40% C_w. Particle formation is shown in FIGS. 5A-5C through shadowgraph images. No swirler case seems to have more ligaments and fewer particles. Penetration of the oxidizer stream is minimum here. At S=0.9, streams form a jot core, and membrane break up can be observed around the outer diameter. The annulus oxidizer streams are pushing the slurries inward, which forms the thick core. When S=1.2, more particles are visible, and uniform penetration of oxidizer can be presumed.

TABLE 2

Particle Diameter

Test Number
Number of Particles
Mean Equivalent Diameter (mm)

1
408
11.3

2
600
10.5

3
756
10.5

4
260
2.32

5
166
2.25

6
134
2.93

7
514
2.25

8
266
2.52

9
271
2.29

Referring to FIG. 6, mean equivalent diameter of slurry lumps for 3 different coal weight percent mixtures and three different swirler numbers are illustrated. The 3 points between 10 and 12 are for S=0. The mean equivalent diameter results are similar for S=0.9 and S=1.2 until 50 weight % coal where the mean equivalent diameter for S=1.2 is lower.

B. Particle Size Distribution:

Droplet size distribution is one of the most critical parameters to characterize the atomization process. The shadowgraphed pictures were analyzed by Dynamic Studio software. This software can provide equivalent diameter for all the particles is detected. Using that diameter, a size distribution analysis was done. The number of particles for a range of diameter size was investigated. The total numbers of particles are not the same for all the cases. Hence, to quantify the effect of swirler, the percentage frequency distribution of droplet sizes was calculated.

Referring to FIGS. 7A-7C, particle size distributions for different swirler numbers and different densities (coal weight percent mixtures) of coal. FIG. 7(a) presents particle sizes of three cases with 30% wt. of coal in the CWS. For no swirler case smallest particles are detected are around 4 mm. And, 20% of the total particles found had sizes bigger than 15 mm. Absence of swirler results in lumps and ligaments instead of atomized droplets. For S=1.2, smaller particles can be detected than S=0.9. 22% of the total particles for S=1.2 have an equivalent diameter below 1 mm, where for S=0.9, it is 19%. However, it can be seen from Table 2 that the total number of particles is much higher for S=1.2 than S=0.9. Hence, a slight increase in percentage distribution can indicate a more significant increase in the total number of smaller particles. For S=0.9, the total number of particles smaller than 1 mm is 49, whereas, for S−1.2, it is 112.

FIG. 7(b) presents particle sizes of three cases with 40% wt. of coal in the CWS. With no swirler, the injector could not produce a significant amount of particles smaller than 4 mm. The density seems to have some effect on particle distribution as well. Overall the distribution for all the cases shifted towards a smaller spectrum. However, the number of smaller particles is more with S=1.2 than S=0.9 for this coal density too. The total number of particles was 267 for S=1.2, whereas, for S=0.9, it was 168. Size distributions for 50% wt. of coal are presented in FIG. 7(c). S=0 does not seem to change a lot with the change in density. Increasing the amount of coal in CWS seems to have benefits only when high swirl is introduced to the injection setup. Higher swirl number clearly seem to have advantages over smaller ones. Here S=1.2 case produces a higher number of smaller particles than the S=0.9. Out of 272 particles, 53 is below 1 mm for S=1.2, whereas for S=0.9, only 19 out of 135 particles fall below that range. The largest droplet detected for S=1.2 is around the 8 mm range. But for S=0.9, quite a few droplets can be found larger than 8 mm.

C. Effects of Swirlers on Jet Break-Up Lengths and Spray Angles:

Break-up lengths decide the combustor body size as it accommodates the flame and the burning environment. A shorter length of the flame can leave more space for flame development hence more burning. After primary atomization jet breakup zone starts. In this region, ligaments start to break down into particles. And the smallest particles can be seen in the secondary atomization zone. However, as the injection hole's distance increases, entrainment of surrounding gasses into the oxidizer stream will increase. So, the effect of the oxidizer streams in the secondary atomization zone is minimum. Table 3 summarizes the breakup lengths for different swirler numbers at 30% C_w. Higher density causes higher viscosity, and viscosity resists liquid ligament breakup. So, for one swirler number, breakup lengths will be higher at higher coal concentrations. Studying lengths for one viscosity but with several swirler numbers can give insight into relative swirler performance. In preferred embodiments at a higher density, the performance trend will be similar. Careful calibrations were conducted before each test utilizing a linear length measuring scale. The calibrated pictures later were used to measure and scale the atomization zones. An example of the process is demonstrated in FIG. 8.

Referring to FIGS. 8A-8B, a demonstration of a jet breakup length measurement technique is illustrated in the context of Test 3 (S=1.2). Referring to FIG. 8A, as the slurry exits the pintle tip orifices, the slurry is impacted by the gas mixture and passes through primary atomization zone 810. Moving further from the pintle tip, jet break up zone 820 is encountered. As the plume continues to travel, secondary atomization zone 830 is encountered. Beyond these zones, drops 840 present themselves. Beyond that, droplets 850 are present.

When there is no swirler, a jet travels approximately 4 inches before it starts to see proper atomization. While for S=1.2, the jet travels approximately 2.5 inches to enter the secondary atomization zone, which is 44% less than the S=0. For S=0.9, jet travels 57% less than S=0. However, the number of particles suggests, at a lower swirler number, the secondary atomization zone will contain more lumps and ligaments than combustible particles.

TABLE 3

Jet Breakup Lengths

Primary
Jet
Secondary

Test
Atomization Zone
Breakup Zone
Atomization Zone

Numbers
(approx.), in.
(approx.), in.
(approx.), in.

1
0.5
3.50
1.00

4
0.50
1.20
1.50

7
0.5
1.75
1.00

D. Effects of Swirlers on Total Momentum Ratios:

The total momentum ratio (TMR) is defined as the momentum rate of the slurry flowing through the pintle over the momentum rate of the oxidizer stream being injected through the pintle. As the two streams impinge on each other with momentum, the momentum ratio between the streams plays a vital role in forming particles. A larger TMR indicates slurry streams have higher energy in them, and it will be harder for the oxidizer streams to penetrate them. The introduction of a non-dimensional parameter like TMR helps normalize the test conditions and allows a straightforward analysis. Two methods were used to calculate TMR, and then the results were compared. Theoretical TMR can be calculated using mass flow rates and slurry velocity. And experimental TMR can be calculated by measuring the spray angle. TMR is the tangent value of the spray angle. Spray angles were measured through visual inspection. A demonstration of the method is shown in FIGS. 8A-8B. The results of the analysis are summarized in Table 4. The table shows the theoretical and experimental TMR for different swirler numbers and different slurry densities. It also a percentage of deviation between the two.

When no swirler was used, theoretical TMRs are almost twice the ones with swirlers. Swirlers induce velocity in the oxidizer stream, which results in higher momentum for them. A 45° angle between the pintle post and the slurry stream is considered optimum for this study. Bigger angles can result in the crashing of unburnt droplets on the combustor body. And smaller angles can create a bigger jet core instead of breaking it up into droplets. Angle 45° corresponds to TMR=1. With a nitrogen flow rate of 0.26 kg/s, S=0 produces a TMR of 2.5. Whereas, with almost the same flow rate, S=0.9 can achieve a TMR around 1.

Furthermore, S=1.2 needs only half the oxidizer flow rate to reach TMR=1. This predicts more atomization for higher swirler numbers than no swirlers. However, the deviation between the experimental and theoretical values for no swirler cases is in the 60%-80% range. Lower oxidizer momentum not only hinders penetration but also allows easy entertainment of external gasses. Since the theoretical calculation does not account for this phenomenon, the deviation percentage is high for this scenario.

For the same reason, S=0.9 cases show more deviation in experimental and theoretical TMR than S=1.2 cases. For S=1.2, the deviations are below 12%, which predicts less external influence.

Referring to FIGS. 9A-9B, a demonstration of spray angle measurement technique is illustrated in the context of (FIG. 9A) Test 4 (S=0.9), and (FIG. 9B) Test 7 (S=1.2). The measured angle for S=0.9 910 is less than the measured angle for S=1.2 920.

From FIG. 9, it can be observed that at S=0.9, the jet core is thicker and lengthier than S=1.2. A thick and long jet core indicates less atomization as most masses are concentrated in the middle. The TMR values for S=1.2 are around 1, which indicates a spray angle of 45°. This angle is desirable as it is the result of the maximum uniform penetration. Also, it decides the travel length of burning particles before they hit the combustor wall.

TABLE 4

Total Momentum Ratio (TMR) for Each Case

Theoretical
Experimental

Test
TMR from
TMR from
% Deviation

Number
momentum
angle
In TMR

1
2.44
1.00
59%

2
2.37
0.90
62%

3
2.57
0.58
78%

4
1.05
0.58
45%

5
1.01
0.70
31%

6
0.83
0.60
28%

7
1.08
1.04
4%

8
1.1
1.07
3%

9
1.21
1.08
11%

EXAMPLES

Specific exemplary embodiments will now be further described by the following, nonlimiting examples which will serve to illustrate in some detail various features. The following examples are included to facilitate an understanding of ways in which embodiments of the present disclosure may be practiced. However, it should be appreciated that many changes can be made in the exemplary embodiments which are disclosed while still obtaining like or similar result without departing from the scope of embodiments of the present disclosure. Accordingly, the examples should not be construed as limiting the scope of the present disclosure.

Example 1

A working example of an embodiment of this disclosure is the verified product shown in FIGS. 10-16. This example has a threaded pintle tip and a closing plate with shorter segment swirl vanes.

Referring to FIG. 10, a cross sectional view of swirl pintle injector 1000 is illustrated. The swirl pintle injector 1000 includes injector body 1010. Pintle post 1020 passes through injector body 1010. The open top of the pintle post can be termed a slurry inlet 1022. The injector body 1010 includes 1 gas inlet 1015. Distribution plate 1030 is coupled to injector body 1010. Distribution plate 1030 includes distribution orifices. Plate 1040 is connected to injector body 1010 and distribution plate 1030. Tip 1050 is coupled to pintle 1020.

Referring to FIG. 11, an isometric view of closing plate 1040 with swirler 1060 is illustrated. Swirler 1060 includes a plurality of air-foil shaped vanes.

Referring to FIG. 12, an isometric view of body 1011 is illustrated. Body 1011 includes two gas inlets 1215.

Referring to FIG. 13, an isometric view is illustrated of injector tip 1050. Injector tip 1050 includes a threaded tip.

Referring to FIGS. 14A-14B, exploded views of the swirl pintle injector are illustrated. The body 1010 is welded to pintle post 1020. Distribution plate 1030 diffuses the oxidizer. The swirler 1040 imparts a rotational movement to the oxidizer about pintle axis 1021 in one of the circular directions of double headed arrow 1023 depending on an angle of the vanes of swirler 1040. In this example, the vanes of swirler 1040 will impart a clockwise rotational movement to the oxidizer relative to axis 1021 when viewed from the open end of pintle post 1020. Of course, the invention is not limited to any particular direction of rotational movement. Pintle tip 1050 is connected to pintle post 1020.

Referring to FIG. 15, an isometric view of the swirl pintle injector are illustrated. The pintle tip 1050 is coupled to the body 1011.

Referring to FIG. 16, the injector assembly has 3 interfaces. Interface A is the coal slurry inlet (feed) that is connected to a 1 inch tube through standard a Swagelok connection. Interface B are 2 gas inlets (gaseous feeds) [for oxidizer] that are connected to two 0.25 inch ports through standard Swagelok connections. Interface C is for connection of the injector itself to an assembly through a mounting flange. The mounting flange has a bolt pattern. In this example, plate 1040 is welded to body 1011.

Example 2

A working example of an embodiment of this disclosure is the product shown in FIGS. 17-21. This example has a straight wall pintle tip and a closing plate with longer segment swirl vanes.

Referring to FIG. 17, an isometric view is illustrated of closing plate 1740 with swirler plate 1760. Swirler 1760 includes a plurality of vanes 1750. Each of the plurality of vanes 1750 is air-foil shaped.

Referring to FIG. 18, an isometric view of injector tip 1850 is illustrated. Injector tip 1850 is based on a straight wall pipe tip.

Referring to FIG. 19, an isometric view of injector body 1911 is illustrated. In this example, there are two gas inlets on the injector body 1911.

Referring to FIG. 20, an exploded view is illustrated of the swirl pintle injector product. The closing plate 1760 covers distribution plate 2030. The injector body 1911 has a pintle post welded in place. The closing plate with welded swirlers can be pinned to pintle post and/or injector body 1911.

Referring to FIG. 21, an isometric view of the swirl pintle injector is illustrated. The injector tip 1850 is shown spaced apart from the body 1911 and all the welded vanes of the swirler are visible.

Example 3

A working example of an embodiment of this disclosure is documented in the results shown in FIGS. 8A-8B, and FIGS. 22A-22C, and FIGS. 23A-23C.

Jet Break Up Lengths Analysis

Referring again to FIGS. 8A-8B, jet breakup length can be accurately and precisely measured.

Referring now to FIGS. 22A-22C, jet break up lengths for different slurry ratios are illustrated. FIG. 22A shows the jet break up length results for a 30/70 coal/water weight percent ratio. FIG. 22 B is for a 40/60 coal/water weight percent ratio. FIG. 22 C is for a 50/50 coal water weight percent ratio. Jet breakup length is another widely used parameter to characterize pintle burners. The jet breakup length consists of the primary atomization/separation zone and the jet breakup zone. It significantly dominates the flame size and influences the combustor dimensions. The jets begin breaking up into large ligaments at the primary atomization zone. The slurry momentum and gravity generally dominate this zone that causes the ligament formation. The jet breakup zone starts after the primary atomization zone. Gas velocity in this region starts to decrease, and mixing increases; as a result, the ligaments start to break down into smaller droplets. In addition, the swirling momentum, turbulence, and interaction with the surrounding environment increase, resulting in a further breakup. The jet breakup zone is followed by the secondary atomization zone, where the smallest particles form. However, as the distance from the injection point increases, the entrainment of surrounding gasses into the jet stream increases; thus, the effect of the oxidizer streams in the secondary atomization zone is minimum.

The camera is first calibrated to a known reference to measure the jet breakup length. Once calibrated, the images are taken in an identical frame to measure and analyze the breakup length. FIGS. 8A-8B present images of the calibration and measuring process. A comparison of jet breakup lengths for different conditions is presented in FIGS. 22A-22C.

No Swirl Conditions:

According to FIGS. 22A-22C, the jet breakup length is highest at no swirl conditions. The results show that increasing the mixing ratio increases both primary atomization zone length and the breakup length. The increase in length is due to the slurry density and viscosity increase. Denser fluid streams have higher viscosity which prevents early flow separation, resulting in an increased primary separation zone. However, as the ligaments travel further from the injection point, the gravitational effect and the surrounding oxidizer stream effects increase and slurry momentum decreases, resulting in a similar breakup zone for denser fluid streams. In addition, without swirl, the mixing effects are minimum resulting in high breakup length.

Swirl S=0.9 Conditions:

The jet breakup length improves in the presence of a swirler. The outcomes suggest a 25-30% smaller primary separation zone than a no swirl condition across different mixing ratios. The presence of a swirler aids the flow separation by inducing tangential velocity and turbulence into the jet stream that results in early separation. In comparison, the breakup zone shows up to 10% improvement at different mixing ratios. Measurements show that the primary atomization zone lengths are 15, 18 and 20 mm, and jet breakup zones are 55, 58 and 60 mm across the mixing ratios 30/70, 40/60 and 50/50. The lowest breakup length is seen at the 30/70 ratio due to minimum slurry density and viscosity, resulting in a fast flow separation; the swirler effect is the most dominant here.

Swirl S=1.2 Conditions:

The jet breakup length significantly improves in the swirl S=1.2 conditions. The smallest primary separation zone is recorded 5 mm among all test conditions and up to an 80% faster jet separation at higher mixing conditions. The early breakup of the jet is associated with the high tangential momentum induced by the swirler 1.2. The high swirl also improves the breakup zone length; the lengths measure 50 mm, 45 mm, and 53 mm for 30/70, 40/60 and 50/50 mixing ratios. The total jet breakup length is also significantly smaller than other conditions. The outcomes indicate a high amount of gas interaction with the jet stream, resulting in a faster break up.

The analysis reveals that the swirl creates a shorter spray, and increasing the mixing ratio increases the primary separation zone. In addition, the performance is better at high swirl conditions. The high swirl also turns the oxidizer streams at a higher angle, allowing the interaction between the gas and the slurry close to the injection point. Additionally, the shorter breakup length allows longer residence time in the combustion environment, which improves ignition probability. However, a fast flow separation indicates high turbulence, negatively impacting lean flames. Therefore, operating with a dense coal-water slurry can provide better ignition ability, superior flame holding and flame stability under high swirl conditions. Thus, the 50/50 mixing ratio at S=1.2 is most suitable for operation.

Spray Angle Analysis

Referring to FIGS. 23A-23C spray angle measurements are illustrated for different swirl numbers. FIG. 23A shows 45° for S=0 and 30/70. FIG. 23B shows 30° for S=0.9 and 30/70. FIG. 23C shows 46° for S=1.2 and 30/70.

Spray angle is another important parameter to characterize the pintle injector. The angle at which the coaxially injected streams collide can significantly impact combustion efficiency. A high spray angle indicates widely dispersed particles that are more likely to escape the flame region and hit the combustor wall. The unburned or partially burned particles deposited on the combustor wall can significantly reduce the life of the combustor by erosion, corrosion and slag buildup. On the other hand, a low spray angle results in injected streams forming a thick jet core instead of breaking up into atomized particles, reducing ignition ability, increasing residence time requirement, and impacting combustion efficiency. Therefore, it is imperative to analyze the spray angle at different conditions to optimize the combustor design and identify optimum operating parameters. A spray angle of 45° is ideal for the current operation based on analytical calculations and combustor designs.

A similar approach to the jet breakup length measurement was taken to measure the spray angle presented in FIGS. 23A-23C. FIG. 23B shows that for a low slurry ratio, the spray angle decreases with the inclusion of swirl, at (30/70)_0.9case compared to no swirl condition. However, the spray angle increases for S=1.2, seen in FIG. 23C. A detailed investigation found that spray angle heavily depends on the oxidizer and slurry momentum. For a given slurry momentum, increasing the oxidizer momentum in the presence of swirlers decreases the spray angle and vice versa. During S=0.9 experiments, the decrease in the slurry momentum while increasing the oxidizer momentum reduced the spray angle. In addition, the swirler induced tangential momentum that turned the oxidizer flow stream towards the jet stream. In the current case, the tangential momentum was sufficiently higher to prevent the jet from spreading, resulting in a narrow spray angle. During the S=1.2 experiments, oxidizer flow decreases by nearly 40%, resulting in a decreased oxidizer momentum. Although the tangential momentum increased because of a high swirl, the slurry momentum was adequate to spread the jet; thus, a higher spray angle for S=1.2 experiments. Therefore, the spray angle is significantly dominated by both the slurry and oxidizer momentum.

TABLE 5

Spray Angle for Different Test Cases

Tests
Experimental Angles

(30/70)₀
45°

(40/60)₀
42°

(50/50)₀
30°

(30/70)_0.9
30°

(40/60)_0.9
35°

(50/50)_0.9
31°

(30/70)_1.2
46°

(40/60)_1.2
47°

(50/50)_1.2
47.2°

The measurements show that the spray angle decreases with the increase in coal percentage under no swirl conditions. Since the slurry momentum increases, high fluid energy is required to disperse a more viscous fluid. An insignificant change in spray angle is observed by changing the slurry ratios under swirl conditions. Early jet breakup by swirler reduces the gravitational effects on the streams, while the increased tangential momentum and turbulence helps to atomize the droplets. When the gas momentum is optimum, it helps disperse the particles and spread the jet. On the contrary, if the gas momentum is too high, it can narrow the jet for dense mixtures. Therefore, a swirl flow helps the jet keep its shape and prevents the spray angle drop due to slurry effects. According to the outcomes, the S=1.2 design performs the best since it produces spray angles similar to the optimum angle of 45°.

Example 4

A working example of an embodiment of this disclosure is documented in the results shown in FIGS. 24A-24F.

Referring to FIGS. 24A-24F qualitative particle size analysis using shadowgraph technique is illustrated. FIGS. 24A-24B show (30/70) with 0.0 swirl. FIGS. 24C-24D show (30/70) with 0.9 swirl. FIGS. 24E-24F) 30/70) with 1.2 swirl. FIGS. 24A-24B present results from a control pintle injector without with swirler.

Referring again to FIG. 22A, primary atomization zone and jet break-up zone distances are shown for 30% coal by weight slurry in cases 1, 2 and 3 of Table 6 corresponding to FIGS. 24A-24B, FIGS. 24C-24D, FIGS. 24E-24F, respectively.

TABLE 6

Spray Angle for Different Test Cases

Test Point
Experimental Angles

(30/70)_{0.0 swirl}
45°

(30/70)_{0.9 swirl}
30°

(30/70)_{1.2 swirl}
46°

The description of the different illustrative embodiments has been presented for purposes of illustration and description and is not intended to be exhaustive or limited to the embodiments in the form disclosed. The different illustrative examples describe components that perform actions or operations. In an illustrative embodiment, a component can be configured to perform the action or operation described. For example, the component can have a configuration or design for a structure that provides the component an ability to perform the action or operation that is described in the illustrative examples as being performed by the component. Further, To the extent that terms “includes”, “including”, “has”, “contains”, and variants thereof are used herein, such terms are intended to be inclusive in a manner similar to the term “comprises” as an open transition word without precluding any additional or other elements.

Many modifications and variations will be apparent to those of ordinary skill in the art. Further, different illustrative embodiments may provide different features as compared to other illustrative embodiments. The embodiment or embodiments selected are chosen and described in order to best explain the principles of the embodiments, the practical applications, and to enable others of ordinary skill in the art to understand the disclosure for various embodiments with various modifications as are suited to the particular use contemplated.

SWIRL-PINTLE INJECTOR FOR OXY-COAL COMBUSTOR

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