Admission Of Air Research Articles

Efficacy of ancillary fluid injection technique for mitigation of vortex rope in hydraulic turbines: A review

Penetration of variable renewable energy into the electric grid requires parallel employment of power generation sources that can quickly balance the fluctuation in frequency of electric grid. Hydro power, being one of the most flexible power supplies, thus takes on an instrumental role in balancing the grid. However, in hydraulic turbines such flexibility is achieved at the expense of departure from turbine operation at the best efficiency point (BEP). Turbine operation at off-design conditions like part load (PL) or high load (HL) results in significant flow instability in the draft tube. Of particular prominence is the vortex breakdown phenomenon which manifests as a precessing vortex rope in the draft tube. The vortex rope causes dynamic pressure fluctuations in the system, additive to the compromise in efficiency. If resonant with the system natural frequency, these pressure fluctuations may affect the mechanical torque delivered by the turbine and cause a phenomenon called power swing. As such it is of paramount importance to circumvent the effects of the rope. Amidst many techniques developed by various investigators for mitigation of the rope, particularly recent the ancillary fluid injection technique exhibits promise. Ancillary fluid injection involves riddance of the stagnation zone that leads to rope formation, through transfer of momentum from a fluid injected at an appropriate location and velocity. This is usually accomplished using water. Admission of air for flow aeration is another method. An experimental as well as numerical perspective of these techniques as developed by various researchers is laid, to assess the benefit obtained alongside the entailing compromise.

Impact of condensate cooled air purging on indoor air quality in an air conditioned laboratory

An air conditioned laboratory is assessed for improvement in IAQ with intermittent purging of pre-cooled fresh air. The base case refers to regular operation without admission of any external fresh air. Air quality studies for the base case, revealed that 58% of occupants reported unpleasant odor and 70% of occupants felt suffocation inside the laboratory. The modified case corresponds to the admission of pre-cooled fresh air at 28 ± 0.3 °C, achieved by passing through a Pre-Cooling Unit (PCU) which gainfully utilizes AC condensate discharged at 16–17 °C. PCU helps in reducing the outdoor air temperature by 3–3.5 °C through sensible and latent storage cooling systems. Experimental and simulation studies were carried out to analyze the effect of admission of pre-cooled fresh air into the laboratory. Results show that the CO2 concentration dropped to 42% in the vicinity of the first two rows. Further experimental and simulation studies conducted in a 44 m3 scaled-down room showed that the concentration of CO2 could be maintained below 1000 ppm with the supply of pre-cooled fresh air. The air quality studies carried out through a questionnaire survey to assess the occupant perception were in line with the experimental and simulation studies carried out for the full room and the scaled-down room.

Studying the Aerodynamics of the TPP-210A Boiler Furnace When It Is Shifted to Operate with Dry-Ash Removal and Vortex Fuel Combustion

To reduce the amount of nitrogen oxide emissions and achieve more reliable operation of the TPP-210A boiler, a process arrangement for firing Grade TR Kuznetsk coal that involves using straight-flow burners and shifting the boiler from slag-tap to dry-ash removal is developed. Owing to a large burner downward slope angle and special arrangement of burners and nozzles, four large vertical vortices rotating in opposite directions are produced in the furnace lower part, as a result of which the combustion products dwell for a longer period of time in the burning zone and more complete fuel combustion is achieved. For verifying the operability and efficiency of the proposed combustion arrangement, investigations on a boiler furnace physical model were carried out using a technique for visualizing fuel jets and secondary and tertiary overfire air jets. The fuel jet temperature boundaries in the course of jet propagation in the furnace model are also determined. The study results have shown that staged fuel combustion will be set up with using the proposed arrangement of burners and nozzles. In addition, large vertical vortices produced in the furnace lower part will help to achieve more efficient use of the dry bottom hopper heating surfaces, due to which lower coal combustion product temperature in the furnace upper part and smaller content of combustible products in fly ash will be obtained. Owing to low values of air excess factor at the pulverized coal burner outlet and gradual admission of air into the vortex zone through a few nozzles with intense inner recirculation of combustion products to the jet initial section, staged combustion of pulverized coal and low nitrogen oxide emissions will be secured. Owing to expansion of fuel jets, a rapid growth of mass in the fuel jet is achieved, which is obtained both due to ejection of the jet itself and due to forced admission of hot fuel gases from other jets. Investigations carried out on the physical model have confirmed that the proposed combustion arrangement features high efficiency and that a low content of nitrogen oxides in flue gases is obtained.

ADAPTIVE REACTION OF SWISS BREED COWS FOR THE NEW REGIME OF MILKING

The aim of our research is to establish adaptive response of lactating cows of Swiss breed by regime change of milking with the installation of "Parallel".
 During milking of the Brown Swiss cows with using a milking machine, the hanger of the apparatus weights 2,1 kg with cylindrical rubber and with the size of vacuum – 42,5 kPa (basic mode), one-time milk yield is at the level of 12,8 kg, corresponding to the average level of cattle at the industrial complex. After replacing the parts of the milking machine, the weight of which increased slightly (80 g, 2,180 kg), with a trihedral rubber and calibrated hole in its head (the new regime), the value of one-time milk yield remains very high, though inferior to the basic level by 2,4%.
 However, if fullness of milking the cows for the new regime is quite satisfactory, duration of milking points to the adaptive reaction to the new regime of milking. Thus, if milking duration was less than 4,7 minutes under the basic mode, then in the new mode it increased by 17,5 % (P <0,001). That is, although the admission of air in space under the teats in the open phase of the milking apparatus provides quick evacuation of milk in the collector of apparatus but it reduces the amount of liquefaction which slows down the process of excretion milk from teats of an udder.
 Inadequate activity of milk output from an udder of the cows under the new regime of milking causes low intensity of milk output. Thus, if under the basic mode its average is 2,8 kg/min, then under the new regime it is less by 27,3% (P <0,001) and only 2,2 kg/min. The maximum intensity of milk output does not exceed 3 kg/min, which is lower by 43,3 % (P <0,001) compared with basic mode of milking.
 Unsatisfactory indicators of functional activity of the cow’s udder indicate low values of excretion milk under the new regime of milking. Thus, under the base regime during the first minute of working the milking apparatus, cows’ udders are emptied from milk by 21,7%, whereas the figure is less by 20,6% and not more than 18% under the new regime. Inadequate emptying of cow’s udder from milk is observed within two minutes of milking under the new regime. So, for this period of time less than half an udder (43%) is emptied from milk, when this figure in the cows under the basic mode of milking is higher by 31,4 % (P <0, 001) and is an average of 62,7%.
 During fifteen days under the new regime of milking, the cows are adapted for this regime, therefore the indicators of functional activity of an udder are improved. Thus, the average intensity of milk output reaches the level of 2,5 kg/min which exceeds the value of the third day of the new regime by 12 % (P <0,001). The maximum intensity of milk excretion increases to 3,4 kg/min which is higher by 11,8 % (P<0,001) than the value of the third day of the new regime of milking. At the same time, these indicators are inferior by 12 % (P <0,01) and 26,5 % (P <0,001) respectively compared with the base mode of milking.
 Inadequate intensity of milk excretion of the Brown Swiss cows is the result of peculiarities of open phase of the milking apparatus by reducing the magnitude of the vacuum.
 Increasing the vacuum of system by 2,5kPa improves the milk excretion. Average intensity of the milk excretion was at the level of 2,7 kg/min, which was 18,5 % (P <0,001) more than the indicator in system at vacuum of 42,5 kPa and almost exactly meets the basic mode of milking.
 Adaptation of the cows was in the fact that the reaction of the functional activity of an udder corresponded to the gentle vacuum mode in the space under teats.

Wood stove combustion air retrofits: A low cost way to increase energy savings in dwellings

In Europe, wood-fired stoves remain as major renewable household heating and emission sources. This study focused on improving the performance of a wood stove (natural draft) traditionally used in Portugal by the adoption of alternative combustion air retrofits. Additionally, the performance of a new pellet stove (forced-air) was determined to investigate the highest achievable goal for solid-fuel stoves. In the wood stove, an outer chimney component was installed around the existing chimney to allow the vertical admission of outdoor air that was preheated before entering the combustion chamber. This measure increased the thermal efficiency of the wood stove from 62% to up to 79%. Another component was used to administrate secondary air to the wood stove reducing the carbon monoxide emissions by 39% to 2808 mg Nm−3. The two retrofits enhanced a more stable heat release from the wood stove, which reached a thermal efficiency 11% lower than that achieved by the pellet stove. This research suggests that retrofitting stoves with chimney components that allow the admission of combustion air can substantially increase energy savings in dwellings. Further efforts should focus on improving the interplay between the outdoor air and secondary air admission to achieve higher emission reductions at low-cost.

A study of hybrid ventilation in an institutional building for predictive control

Hybrid ventilation can be employed to precool thermally massive buildings, reducing energy consumption for cooling the following day, particularly at night when the outdoor temperature is lower, and especially when its operation is done in a predictive manner by incorporating weather forecasts. An important requirement is defining the temperature low limit for admitting exterior cool air into a building through transition spaces, to ensure thermal comfort. This paper uses a case study of a 17-story high institutional building with a hybrid ventilation system. To develop a strategy for the admission of outside air into the building, this study focuses on the corridors as generic transition zones/buffer spaces with flexible thermal comfort limits and with the motorized façade openings to determine how the air temperature evolves with distance from the inlets. A developed thermal model, calibrated from a full-scale test, calculates the amount of heat removed from the 0.4 m thick concrete floor. Through 4 h of night cooling with an average local exterior temperature of 8.3 °C, the air temperature rises to about 12 °C in the transition corridor region at a time when occupancy in that area is expected to be nearly zero. Taking into consideration the flexibility in thermal comfort in the corridor transition spaces, control strategies are developed, based on exterior temperature and humidity. Using humidity ratio instead of relative humidity as criterion for admitting outdoor air potentially results in the system being active for 49% - 180% more hours during the year.

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A Simulation Based Study of Flow Velocities across Cross Flow Turbine at Different Nozzle Openings

The present work reports CFD based investigation of the effect of design parameters on the flow velocities of a cross flow turbine (CFT). Best described as an impulse type turbine with partial admission of air, cross flow turbines meet the demand for an efficient turbine to run at low head that is also easy to manufacture. The design of cross–flow turbine is unique due to the generation of power during two stages. This type of turbine is often used in small hydropower plants located in less–developed countries. The design parameters of CFT that can be varied to increase overall efficiency and power output of the turbine are water inlet angle, blade angle at inlet and outlet. In the present work the design parameters are varied for different nozzle openings and simulated using CFD. A full 3-D steady state flow simulation of the cross-flow turbine is performed including casing, runner and nozzle assembly.

The acoustic model of oscillations of gas combustion in coaxial pipes

Organization of pulse combustion mode is one of the possible solutions to the problem of energy efficiency installations using hydrocarbon fuel. For grate combustion of solid fuels, in particular, solid industrial wastes are considered to be promising coaxial system, allowing the admission of secondary air to the combustion zone. In this paper we proposed an acoustic model of oscillations of gas when burning solid fuel in the system is coaxially arranged pipes with natural air supply. The description of the motion of the gas in the system during one period of oscillation.

Study of the influence of vane angle on shaft output of a multivane air turbine. II. Different rotor to casing diameter ratios with optimal injection angle

This paper describes new results towards performance evaluations of a compressed air driven vane type rotary novel air turbine/engine. The compressed air has potential of becoming nearly zero pollution power source for running the prime-mover/engine of the small bikes/motorbikes. The proposed air turbine will transform the energy of compressed air into mechanical shaft work in place of the internal combustion engine. The effect of isobaric admission and adiabatic expansion of high pressure air for different rotor to casing diameter ratios at optimum injection and vane angles are considered in the mathematical model presented in this paper. The results are evaluated with optimal vane angles, injection angles, different rotor/casing ratios, and different casing diameters. It is seen that the power output is optimum to the typical values of rotor/casing diameter ratios (d/D). In this study, the maximum power outputs for linear expansion (i.e., for minimum air consumptions) are obtained as 3.98 kW (5.41 HP) at d/D = 0.70, 5.50 kW (7.48 HP) at d/D = 0.80, and 6.08 kW (8.27 HP) at d/D = 0.85 when casing diameters (D) are 100 mm, 150 mm, and 200 mm, respectively, at injection pressure 90 psi (6 bar) and speed of rotation 2500 rpm.

Learning control for batch thermal sterilization of canned foods

A control technique based on Reinforcement Learning is proposed for the thermal sterilization of canned foods. The proposed controller has the objective of ensuring a given degree of sterilization during Heating (by providing a minimum temperature inside the cans during a given time) and then a smooth Cooling, avoiding sudden pressure variations. For this, three automatic control valves are manipulated by the controller: a valve that regulates the admission of steam during Heating, and a valve that regulate the admission of air, together with a bleeder valve, during Cooling. As dynamical models of this kind of processes are too complex and involve many uncertainties, controllers based on learning are proposed. Thus, based on the control objectives and the constraints on input and output variables, the proposed controllers learn the most adequate control actions by looking up a certain matrix that contains the state-action mapping, starting from a preselected state-action space. This state-action matrix is constantly updated based on the performance obtained with the applied control actions. Experimental results at laboratory scale show the advantages of the proposed technique for this kind of processes.

Effect of Rotor to Casing Ratios with Different Rotor Vanes on Performance of Shaft Output of a Vane Type Novel Air Turbine

This paper deals with new concept of using compressed atmospheric air as a zero pollution power source for running motorbikes. The motorbike is equipped with an air turbine in place of an internal combustion engine, and transforms the energy of the compressed air into shaft work. The mathematical modeling and performance evaluation of a small capacity compressed air driven vaned type novel air turbine is presented in this paper. The effect of isobaric admission and adiabatic expansion of high pressure air for different rotor to casing diameter ratios with respect to different vane angles (number of vanes) have been considered and analyzed. It is found that the shaft work output is optimum for some typical values of rotor / casing diameter ratios at a particular value of vane angle (no. of vanes). In this study, the maximum power is obtained as 4.5kW 5.3kW (5.5-6.25 HP) when casing diameter is taken 100 mm, and rotor to casing diameter ratios are kept from 0.95 to 0.70 and the said power output is sufficient to run motorbike.

Para-Quinone-Containing Bis(pyrazol-1-yl)methane Ligands: Coordination Behavior Toward CoII and a C−H Activation Reaction with CeIV

Two series of sterically demanding para-dimethoxyphenyl-substituted bis(pyrazol-1-yl)methane ligands have been synthesized, i.e., L2(R,R') = ((MeO)(2)C(6)H(3))C(H)(pz(R,R'))(2) and L3(R,R') = ((MeO)(2)C(6)H(3))C(Me)(pz(R,R'))(2) (R,R' = 3-Me,5-Me; 3-Ph,5-H; 3-tBu,5-H). In the solid state, already the sterically least encumbered derivative L2(Me2) is able to stabilize Co(II) complexes of the form [X(2)Co(L2(Me2))] (X = Cl, NO(3)); in solution, these complexes are at an equilibrium with the 1:2 species [Co(L2(Me2))(2)](2+). Oxidative demethylation of L3(Ph) and L3((t)Bu) with [Ce(NH(4))(2)(NO(3))(6)] leads to the corresponding para-benzoquinonyl-substituted bis(pyrazol-1-yl)methane ligands L4(Ph) and L4((t)Bu). Contrary to that, the methyl derivative L3(Me2) is transformed into the ortho-benzoquinone species L5(Me2), which still contains one methoxy substituent while one oxygen atom has been newly introduced. The formation of L5(Me2) requires (i) the admission of air, (ii) the presence of both methoxy substituents of L3(Me2), and (iii) the presence of (methyl) substituents both at the exocyclic carbon atom and at the 5- positions of the pyrazolyl rings. The parent ortho-hydroquinonyl-substituted bis(pyrazol-1-yl)methane ligand ((HO)(2)C(6)H(3))C(H)(pz(H,H))(2) is readily available from 3,4-dihydroxybenzaldehyde and (pz(H,H))(2)SO/pyridine.

Analytical Evaluations of Shaft Output on Different Rotor to Casing Diameter Ratios at Optimal Value of Vane and Injection Angles for a Multi-Vane Air Turbine

The atmospheric air is freely available but once it is compressed, it develops the potential power source for running any prime mover as a zero pollutant. Thus air turbine proposed to be installed here on motorbike transforms the energy of the compressed air into shaft work in place of an internal combustion engine. This paper details a mathematical modeling and performance evaluation of an air driven vane type rotary novel air turbine / engine. The effect of isobaric admission and adiabatic expansion of high pressure air for different rotor to casing diameter ratios at optimum vane and injection angles as 450, 300 respectively have been considered and analyzed. The optimum work output is seen at some typical values of rotor / casing diameter ratios at moderate air consumptions. In this study, the power obtained along linear expansion (without excessive air consumption) as 6.0-7.6 kW (8-10 HP) between rotor to casing diameter ratios 0.85 to 0.80, at casing diameter of 200 mm, injection pressure of 90 psi (6 bar) and speed of rotation 2500 rpm which is enough to run any motorbike or light vehicle.

In situ gasification and CO 2 separation using chemical looping with a Cu-based oxygen carrier: Performance with bituminous coals

This paper is concerned with the chemical looping combustion of coal in a technique whereby the fuel is gasified in situ using CO 2 in the presence of a batch of supported copper oxide (the “oxygen carrier”) in a single reactor. As the metal oxide becomes depleted, the feed of fuel is discontinued, the inventory of fuel is reduced by further gasification and then the contents are re-oxidised by the admission of air to the reactor, to begin the cycle again. A catalyst support, impregnated with a saturated solution of copper and aluminium nitrates, acted as a durable oxygen carrier over numerous cycles of reduction and oxidation, using air as the oxidant. Two bituminous coals (Taldinskaya, Russia, and Illinois No. 5, USA) were investigated and compared with a lignite (Hambach, Germany). The lignite was highly reactive and was gasified completely by 15 mol% CO 2 in N 2 at 1203 K and 1 bar, so that there was no build up of char in the bed. The bituminous coals produced chars much less reactive than the lignite char, so that there was a steady accumulation of char in the bed with number of cycles, with the degree of accumulation being dependent on the reactivity of the char. Since the kinetics of gasification by CO 2 of the chars from either bituminous coal were slow, their rates were controlled by intrinsic chemical kinetics and were not affected by the ability of the oxygen carrier to alter the rates of external mass transfer when gasification is rapid. However, it is likely that rates of gasification in the presence of the carrier are still larger than in its absence, owing to the overall lower [CO] present in the bulk of the fluidised bed during chemical looping. At the temperature used, the carrier was cycling between Cu and Cu 2O, since CuO is only stable if the partial pressure of O 2 exceeds 0.03 bar at 1203 K. The CuO decomposes to Cu 2O and O 2 relatively rapidly at these temperatures, once the oxygen concentration is effectively zero. It was impossible to ascertain in our experiments whether the oxygen so generated, after the switching of the air for nitrogen before the start of the succeeding cycle of gasification, made any substantial difference to the reactivity of the char present in the bed. The rate of oxidation of the carrier was found to be much more rapid than the rate of oxidation of the inventory of char. This allows a preferential oxidation of the carrier and most likely accounts for why progressively less CO and CO 2 is produced during successive cycles with short periods of oxidation: the increasingly reduced carrier reacts more rapidly than the char. There was no obvious impact from the sulphur contained in the fuels, but longer-term testing is needed. No agglomeration between the carrier particles and the ash was observed, despite the high temperatures during oxidation.

Evolution of stress in evaporated silicon dioxide thin films

The evolution of stress in evaporated SiO2, used as optical coatings, is investigated experimentally through in situ stress measurement. A typical evolution pattern consisting of five subprocedures (thin film deposition, stopping deposition, cooling, venting the vacuum chamber, and exposing coated optics to the atmosphere) is put forward. Further investigations into the subprocedures reveal their features. During the deposition stage, the stresses are usually compressive and reach a stable state when the deposited film is thicker than 100 nm. An increment of compressive stress value is observed with the decrease of residual gas pressure or deposition rate. A very low stress of -20 MPa is formed in SiO2 films deposited at 3×10-2 Pa. After deposition, the stress increases slightly in the compressive direction and is subject to the stabilization in subsequent tens of minutes. In the process of venting and exposure, the compressive component increases rapidly with the admission of room air and then reaches saturation, followed by a logarithmic decrement of the compressive state in the succeeding hours. An initial discussion of these behaviors is given.

In situ gasification of a lignite coal and CO2 separation using chemical looping with a Cu-based oxygen carrier

Abstract Chemical looping combustion (CLC) has the inherent property of separating CO 2 from flue gases. This paper is concerned with the application of chemical looping to the combustion of a solid fossil fuel (a lignite and its char) in a technique whereby the fuel is gasified in situ using CO 2 in the presence of a batch of supported copper oxide (the “oxygen carrier”) in a single reactor. As the metal oxide becomes depleted, the feed of fuel is discontinued, the inventory of fuel is reduced by further gasification and then the contents are re-oxidised by the admission of air to the reactor, to begin the cycle again. The choice of oxides is restricted because it requires an oxide which is exothermic during reduction to balance the endothermic gasification reactions. Copper has such oxides, but a key question is whether or not it can withstand temperatures at which gasification rates are significant (∼1173 K), particularly from the point of view of avoiding sintering and deactivation of the carrier in its reduced form. It was found that an impregnated carrier, made by impregnating a θ -alumina catalyst support (BET area 157 m 2 /g) with a saturated solution of copper and aluminium nitrates, acted as a durable carrier over 20 cycles of reduction and oxidation, using both Hambach lignite coal, and its char, and with air as the oxidising agent. During the course of the experiments, the BET surface area of the support fell from ∼60 m 2 /g, just after preparation, to around 6 m 2 /g after 20 cycles. However, this fall did not appear to affect the overall capacity of the oxygen carrier to react with fuels and its effect on the kinetics of the reaction with CO did not influence the outcome of the experiments, since the overall performance of the looping scheme is dominated by the much slower kinetics of the gasification reaction. The apparent kinetics of the gasification are faster in the presence of the looping agent: this is because the bulk concentration of CO in the presence of the looping agent is lower, and partly because the destruction of CO in the vicinity of a gasifying particle enhances the rate of removal of CO by mass transfer (and increases the local concentration of CO 2 ). There was little evidence to suggest a direct reaction between carbonaceous and carrier solids, other than via a gaseous intermediate. However, the observation of finite rates of conversion in a bed of active carrier, fluidised by nitrogen, is a scientific curiosity, which we have not been able to explain satisfactorily. At 1173 K, as used here, rates of gasification of Hambach lignite, and its char, are significant. The CuO in the carrier decomposes at 1173 K to produce gas-phase O 2 and Cu 2 O: both can react with CO produced by gasification, whilst the O 2 can react directly with the char.

SPECTRALLY SENSITIZED PHOTOCONDUCTIVITY OF ZINC OXIDE CRYSTALS*

Abstract— Spectral sensitization of photoconductivity was found after coating single crystals with an organic dye in a methanol solution. Similar experiments have been carried out under conditions designed to exclude the influence of solvent and adsorbed gases. The dye was deposited from vapor onto clean crystal surfaces in ultrahigh vacuum and the spectral distribution of the photoconductivity was observed without admission of air. With both methods of dyeing, the quantum yields, referred to the absorbed light, were comparable to the yield in the intrinsic region. Also the influence of a transverse electric field upon surface conductivity before and after dyeing was studied. From the ‘field effect’ it is concluded that the adsorbed dye causes a considerable increase of the density of electronic surface states near the Fermi level.

Benzo- and naphthoimidazoxadiazolediene, naphthobisthiazole as well as naphthothiazine derivatives from 1-acylthiosemicarbazides

Acylthiosemicarbazides 1a-d reacted with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (2a), 2,3,5,6-tetrachloro-1,4-benzoquinone (2b), 2,3-dichloro-1,4-naphthoquinone (3a) and 2,3- dicyano-1,4-naphthoquinone (3b) in ethyl acetate with admission of air to form benzo- and naphtho-imidazoxadiazoles (5, 6, 11), naphthobisthiazoles (12a-d), naphthothiadiazines (13a-d) as well as 2,3,7,8-tetrachlorothianthrene-1,4,6,9-tetraone (7). Rationales for the observed conversions are presented.

Indazole, oxathiadiazole, and thiadiazine derivatives from thiosemicarbazides

4-Substituted thiosemicarbazides 1a–c reacted with 2,3-dicyano-5,6-dichloro-1,4-benzoquinone (DDQ, 2), 2,3,5,6-tetrachloro-1,4-benzoquinone (CHL-p, 6) and 2,3-dichloro-1,4-naphthoquinone (DCHNQ, 7) in ethyl acetate with admission of air and form the derivatives of 1,5,2,3-oxathiadiazole 8a–c, indazole 9a–c, 1,3,4-thiadiazine-6-one 10a–c, 1,3,4-thiadiazaphenanthren-9-one 11a–c, naphtho[1,2-e:4,3-è]bis134thiadiazine 12 and dibenzo[b,i]thianthrene-5,7,12,14-tetraone 13. A rationale for the conversions observed is presented.