Fixed Air Flow Rate Research Articles

Analyzing the effect of flooring material type on the performance of an active greenhouse dryer

In this work, the impact of flooring (bottom) material selection on the performance of an active greenhouse dryer (AGD) has been empirically surveyed. In this regard, four AGD configurations with different flooring materials including soil, gravel, sheet metal with conventional black paint and sheet metal with iron (Fe) nano-enhanced black paint have been designed, manufactured, and experimented at same fixed air flow rate. According to experimentally obtained findings, utilizing nano-enhanced black-painted sheet metal in the AGD instead of soil has a potential to almost double the average air temperature difference. Also, using sheet metal with nano-enhanced black paint reduced the drying periods as 41.17 %, 33.33 % and 20 %, respectively in comparison to the configurations that used soil, gravel and sheet metal with conventional matt black paint as bottom material. Average exergetic efficiencies for the tested configurations were obtained between the range of 3.22–11.14 %. Also, using sheet metal with Fe nano-enhanced absorber coating as a bottom material in the system reduced the carbon footprint as 32.66 % (from 1.50 to 1.01 kgCO2eq) in comparison to the system with soil bottom.

Enhancing the performance of an unglazed solar air collector using mesh tubes and Fe3O4 nano-enhanced absorber coating

In the current article, it is intended to improve the performance of an unglazed solar air collector using mesh tubes as extended heat transfer surfaces and nano-enhanced black paint as a thermal conductivity booster of the absorber coating material. In this regard, three types of unglazed solar air collectors have been designed, produced and simultaneously tested containing a conventional (unmodified) system, a system with only mesh tube modification and a system with combined usage of mesh tubes and nano-enhanced absorber coating. It should be stated that Fe3O4 nanoparticles have been utilized within the scope of this work. Integrating nanoparticles to the absorber coating material (industrial matt black paint) averagely improved the thermal conductivity as 0.031 W/mK. The experimental process was tested at fixed air flow rate (0.0115 kg/s) in winter climatic conditions. As result of the experimental analysis, average thermal efficiency values were attained between 45.11 and 63.36%. Combined usage of mesh tubes and nano-enhanced black paint upgraded the mean thermal performance as 40.45% in comparison to the unmodified system. Also, obtained exergetic efficiencies are in the range of 5.49–9.96%. In addition to the energy-exergy analysis, enviro-economic survey was performed within the scope of the current work. Payback periods of the analyzed systems were found between 0.31 and 0.34 years.

Experimental study of a solar air heater with modified absorber plate through square obstacles with threaded pin fins

In this present experimental study, a flat absorber plate of a solar air heater (SAH) is modified through square obstacles with threaded pin fins to rate the performance of the SAH. It is evident from the literature that the poor rate of heat transfer of flat plate SAH remains a matter of concern for practicing engineers. The modification of the absorber plate’s surface becomes to be an effective practice for the researchers to counter the drawbacks and augment the performance of the SAH. From the energy, exergy, exergoeconomic, and enviroeconomic standpoint, the present study discloses that the modified absorber plate performs better than the conventional flat absorber plate. The exit temperature of the solar air heater is increased by about 9% using the modified absorber plate. The energetic efficiency is found to be improved with the governing parameters. For a fixed air flow rate of 0.0094 kg/s, using a modified plate absorber augments the useful energy gained and the energy efficiency by 28.81% and 23.59%, respectively, for the higher collector tilt angle of 35°. Similarly, exergy efficiency is reported to be increased by 30% for the same conditions. Using a modified absorber plate decreases the exergy destruction by about 10% for the higher collector tilt angle and air flow rate. The energy payback time is estimated to be 1.42 years and the CO2 mitigation is reduced to 32.98 kg/year compared to the CO2 mitigation value of 333.33 tonnes using the modified absorber plate for a system life of 30 years.

Energy and exergy analysis of a liquid desiccant heat and mass transfer loop with natural convection: The effect of heat sink and heat source temperature

Desiccant systems, as a promising air conditioning technology have opened new aspects as a replacement for vapor compression systems. The liquid desiccant energy exchanger system with natural convection flow is proposed here; the system is a loop with two hollow fiber membrane air-desiccant exchanger of shell-and-tube type that works as the humidifier and regenerator. The LiCl aqueous solution as desiccant directed over the fibers and the air is inside the fibers; the water stream flows outside the modules to provide the required heat exchange. The heat sink and source as merged subparts of the exchangers have a major influence on system performance. The system is examined from the energetic and exergetic viewpoints at different heat sink and heat source temperatures. Keeping the fixed air flow rate and using the standard air properties, the cold and hot water temperatures of 15–25 °C and 50–70 were employed and the effectiveness coefficients including the latent, sensible and total and 2nd law efficiency evaluated. It was shown that the values of NTU and Cr* depend on each other and attenuating effect of NTU reduction is higher than enhancing effect of Cr* increase on effectiveness values. The prominent factor on exergy performance which hinders the effect of the other parameters is the solution flow rate. Also, the highest and lowest values of 2 nd law efficiency are 81% and 5% which are for temperature pairs of (52, 20) and (65,25), respectively.

Optimized pleat geometry at specific pleat height in pleated filters for air purification.

The performance of an air purifier is determined by its clean air delivery rate (CADR), expressed as the product of the air flowrate and filter collection efficiency. A high CADR in a commercial air purifier is achieved using a pleated air filter with high filtration performance at a given air flowrate. However, obtaining this high filtration performance depends on the knowledge of the manufacturer, including the optimal pleating design, which remains uncertain to date. In this study, test pleated filters were prepared by folding a flat electrostatically-charged E12 filter medium to obtain different pleating geometries. The proper pleat geometry of the pleated filter, which has a minimum pressure drop at a fixed air flowrate, was dependent on the pleat length (PL ) and pleating ratio (α=pleat height/pleat width), wherein as the PL increases, the α range required to achieve a minimum pressure drop similarly increases. Based on the filter quality factor (qF ), the optimal pleat geometry of a pleated filter was between α values of 6-8, irrespective of the PL . Although both PL and α have certain influences on the qF , α has a greater influence on the pleated filter with no dead zone.

Experimental investigation on a cooling cum desalination system using a modified mechanical heat pump

An experimental study on a mechanical heat pump unit incorporated with a humidification-dehumidification system for desalination and cooling is presented. The experimental prototype is developed by modifying the condenser of a mechanical heat pump unit into an evaporative condenser. The evaporative condenser is used as a humidifier, and the evaporator as a dehumidifier, of the humidification-dehumidification desalination system. The proposed unit is evaluated with combinations of air and saline water flow rates, and also evaluated by means of total desalination output, cooling output, gained output ratio and energy utilization factor. At fixed air flow rate, increasing saline water flow rate decreases the desalination output, and increases the cooling output, gained output ratio and energy utilization factor, respectively. The highest fresh water yield and gained output ratio are 2.94 LPH and 1.30 respectively. The highest cooling output and energy utilization factor are 4.39 kWth and 4.12, respectively. The total urban heat island mitigation at the operating condition of 200 m3.h−1 and 380 LPH is 5.25 kWth. Compared with similar vapor compression refrigeration operated humidification dehumidification desalination units, the present study produces more fresh water yield and cooling output with fewer energy consuming devices and heat exchangers.

Optimum Drying Parameters of Fluidized Bed Dryer Operation for Rice and Corn

This study was carried out to develop a simulation model that can estimate the optimal drying parameters of a fluidized bed dryer such as drying time, moisture reduction rate and provide rough calculation of energy required and fuel consumption to dry a given volume of grains. Results shows that drying set up of 1400C drying temperature, bed height of 0.04m and an airflow rate of 2.3 m/s for paddy can provide lesser drying time and higher drying rate with a value of 164 minutes and 68.07 kg/hr, respectively. While for corn, a set-up of 1700C drying temperature, bed height of 0.1m and the fixed airflow rate of 2.7 m/s can deliver lesser drying time and higher drying rate with a value of 45 minutes and 369.9 kg/hr, respectively. The simulation results also showed that using a higher temperature, higher airflow and lower bed height gives a lesser drying time which also leads to higher drying rate. In terms of drying energy and fuel consumption, the results showed that the higher the drying temperature, the higher the energy and fuel consumption is required.

Enhancement of biogas combustion by co-firing dimethyl ether in a gas turbine model combustor

To improve the combustion intensity of biogas which is a renewable gas turbine fuel with methane (CH4) and CO2 as major components, dimethyl ether (DME, CH3OCH3) was used to co-fire with biogas in a gas turbine model combustor in this work. Swirl combustion characteristics of biogas/DME mixtures under different DME contents in fuel mixtures (α) and CO2 contents in biogas mixtures (β) were measured. Numerical simulation and kinetic analysis were performed to provide insights into the effects of DME co-firing and CO2 content on combustion characteristics. It was observed that flame shape and flame size remain almost unchanged with varying DME content and CO2 content at the fixed air flow rate, which are associated with the nearly unchanged flow field. The flame displays a purple color with DME co-firing due to the enhanced formaldehyde (CH2O) chemiluminescence. DME co-firing can effectively improve the flame stability and lower the lean blowout limit (LBO). The decreased LBO is associated with the enhanced fuel reactivity, which results in the reduced ignition delay time and the increased laminar flame speed, OH peak value and high-level OH area. However, increasing CO2 content raises LBO, which is associated with the decreased laminar flame speed, OH peak value and high-level OH area. The ignition delay time can hardly follow the LBO trend with varying CO2 content as it cannot account for the thermal effect caused by CO2 addition. Furthermore, the NO emissions increase with DME co-firing and exceed 20 ppm in pure DME combustion due to the increased temperature level and high-T area, while the amplitude of combustion acoustics is elevated by ∼30–70% with increasing DME content. In contrast, both the NO emissions and amplitude of combustion acoustics attenuate with increasing CO2 content.

Performance study on a mono-pass solar air heating system (MPSAH) under the influence of a PCM

The present investigation presents the findings of an experiential examination of the effectiveness of a Mono-Pass Solar Air Heating System (MPSAH) using a paraffin-based phase changing material (P-PCM) as an energy storing medium for off-sunshine hours. A mono-pass solar air heating system was fabricated with the absorbers having parallelly placed plate fins for attaining the effective heat transfer during solar time. The trials had been carried out in two configurations on the days with similar irradiative pattern in March 2020 at 12.8750° N, 80.2257° E. In the first configuration, the unaltered solar air heating system was used and named as MPSAH. In the second configuration, the MPSAH was packed with the technical grade paraffin beneath the absorber and named as MPSAH-PPCM. The experiments had been accompanied at a fixed air flow rate of 0.167 kg/s. The results demonstrated that the incorporation of P-PCM into the plate finned SAH significantly improved its energy efficacy. The P-PCM increased the MPSAH's energy efficacy by 12.15 percent.

A data-driven approach using machine learning for early detection of the lean blowout

A data-driven approach using machine learning is presented for the identification of the critical flame location for the early detection of an incipient lean blowout (LBO) in a realistic gas turbine engine combustor under engine-relevant conditions. This method is demonstrated by utilizing the temperature (T) and the hydroxyl radical mass fraction (YOH) data from high fidelity large eddy simulations (LES) of Jet-A combustion. The fuel flow rate is progressively reduced in numerical simulations with a fixed airflow rate to mimic experimental studies of LBO in the gas turbine combustor. These simulations are the first of their kind for a fully resolved realistic combustor geometry with adaptive mesh refinement and have accurately captured the dynamics of the LBO process and global lean blowout equivalence ratio. Time-series of T and YOH are extracted in the primary zone of the combustor, from stable flame condition to LBO condition, to train the machine learning model. A Support Vector Machine (SVM) model with radial basis function is successfully developed to identify the critical flame location for early detection of incipient LBO condition in a practical combustor for the first time. The performance of the SVM model is quantified using the F-score, and the critical flame location corresponds to the maximum value of the F-score. The critical flame location is found to be in the flame root region and is effective in the early detection of incipient LBO. The conventional statistical measures are compared with the results of the trained machine learning model to assess the feasibility of the latter for online flame health monitoring. The machine learning model successfully prognosticated the LBO approximately 20 ms before the event, and this study has shown significant promise for the use of the SVM model in engine prognostics and health management.

Numerical modelling of oxygen mass transfer in diffused aeration systems: A CFD-PBM approach

The diffused aeration process is the most energy-intensive operation of bioreactor treatment, amounting to 45–75 % of the plant energy costs. To improve its efficiency, it is essential to measure the oxygen transfer rate from the aerators to wastewater. In this study, a multiphase mixture computational fluid dynamics (CFD) model is developed using k-ε turbulence closure equations along with a discrete population balance model (PBM) add-on with specific bubble classes, to predict the oxygen mass transfer. The transfer of oxygen species from air to water is modeled using the species transport model. The PBM is used to analyze the formation, growth, breakage, and coalescence of air bubbles. The validated model is then extended for sensitivity analysis for a diffused aeration system in a bench-scale aeration tank. Results show that, the volumetric oxygen mass transfer coefficient increases by 15 %, with a decrease of air bubble size by 10 %. The air bubbles have a wider distribution, with a larger diameter near the bottom of the bioreactor and a narrow distribution with a smaller bubble size at the top. Results show that, in the bioreactor, the dissolved oxygen concentration reaches the equilibrium or saturation value when the height by breadth ratio is 2.5 and does not increase further with increase in height of the water column. Also, the air bubble size of 6 mm was the efficient bubble size for a fixed airflow rate of 1.45 m3 h−1.

Syngas Production From Palm Kernel Shells With Enhanced Tar Removal Using Biochar From Agricultural Residues†

In this study, palm kernel shells (PKS) were utilized in an air gasification process to produce syngas. Also, biochar prepared from pyrolysis of the mangosteen and durian peels in was used in the gasification process to enhance the tar removal efficiency. The expected outcomes of this study could result in not only the generation of renewable energy but also the waste utilization of agricultural residues. The effect of catalysts and biochar on tar reduction to improve the syngas quality were extensively studied. A downdraft gasifier equipped with catalytic and adsorption units was utilized to produce syngas. The process was operated with 1 kg of palm shell per batch at a fixed airflow rate of 25 L/min. The NiO/CaO catalysts with a fixed CaO amount of 10 wt% and various NiO contents of 2 wt%, 4 wt%, and 8 wt% were synthesized by co-impregnation on the ceramic supporter. The results of SEM analysis showed that the NiO and CaO were deposited and well dispersed on the porous ceramic ring supporters. The presence of an associated active NiO peak at a wavelength of 692 cm-1 was observed in the FTIR result. The durian and mangosteen peels residues were pyrolyzed at 400 – 700 oC for 2 hrs to prepare biochar to be used as tar adsorbent. The BET surface area of obtained biochar was 0.9219 - 0.9989 m2/g with a range of adsorption pore size of 11.193 - 11.912 nm. The syngas samples were collected from the gasification unit every 15 min during a 1-hr period of processing time. The syngas compositions were analyzed by gas chromatography. The GC results indicated that increasing NiO contents in the catalysts tended to result in increasing methane and carbon dioxide concentration of the syngas, possibly contributed from the further involving tar cracking reactions. With the presence of biochar, the amount of tar captured in the filter unit was significantly increased up to 9 times compared to the system without biochar.

Fixed air flow-rate selection by considering the self-regulating function of low power air-cooled PEMFC stack

In this study, it is found that the air-cooled proton exchange membrane fuel cell (PEMFC) has a self-regulating function in terms of its thermal and water balances within the fuel cell. Such a function enables the fuel cell's operation to be stable and efficient without any electronic controlling circuit to control the operating parameters. A small air-cooled PEMFC stack (15 cells with a rate power of 60 W) integrated with an axial fan is used for this experimental study to verify the self-regulating feature. The results show that the air-cooled open-cathode PEMFC stack can run stably and efficiently under a wide range of load currents at a fixed air flow rate. The best fuel cell performance and maximum system net power output are achieved at an air flow of 55.7 SLPM. To further validate the results, the temperature distribution and cell voltage distribution of the stack are simultaneously measured under different loads. The results demonstrate that the temperature and cell voltage of the stack are evenly distributed at the air flow of 55.7 SLPM. The present study may provide guidance in the design of a cooling subsystem of a small and compact fuel cell system incorporating an air-cooled open-cathode PEMFC.

Quality improvement of syngas from gasification process of palm kernel using NiO/CaO catalysts on ceramic supporter in coupled with biochar absorbent from agricultural residues

In this study, palm kernel shells were utilized in the gasification process to produce syngas. In addition, biochar prepared from pyrolysis of the left-over mangosteen and durian peels were used in the gasification process to enhance the tar removal efficiency. The expected outcomes of this study could result in not only the generation of renewable energy from but also the waste utilization of agricultural residues. The effect of catalysts and biochar on the syngas quality improvement were particularly studied. Palm kernel shell was used as raw material. The compositions and heating values of the biomass were characterized by the proximate, ultimate, and bomb analyses, respectively. Syngas was produced from a downdraft gasifier connected with catalytic and adsorption units in sequence. The gasification process was operated with 1 kg of palm shell per batch at a fixed air flow rate of 25 L/min. The NiO/CaO (10 %wt) catalysts on ceramic supporter with various NiO contents of 2%, 4%, and 8% were synthesized by co-impregnation. Biochars were synthesized by pyrolysis process of durian and mangosteen peels at around 300 - 500 °C for 2 hrs. Morphology and compositions of the synthesized catalysts and biochar were analyzed. The results of SEM analysis showed that the NiO and CaO were deposited and well dispersed on the porous ceramic ring supporters. The presence of active NiO on the catalyst was also confirmed in FTIR result with (wavelength of 692 cm−1). Biochar from durian and mangosteen peels, with BET surface area of 0.9219 - 0.9989 m2/g and adsorption pore size of 11.193 - 11.912 nm, were obtained from a pyrolysis process at 400 - 700 °C. The syngas samples were collected from the gasification unit every 15 min to 60 min. The gas chromatography was used to analyze the syngas compositions. The GC results indicated that increasing NiO contents in the catalysts tended to result in increasing CH4 composition of the syngas for both systems with and without biochar. With tar filtration unit containing biochar, the ability of tar removal was significantly increased by 2 to 9 times comparing to the system without biochar.

The emissions from co-firing of biomass and torrefied biomass with coal in a chain-grate steam boiler

ABSTRACTIn this study, biomass of rice straw (RS) and wood (WD) and their torrefied biomass (RST and WDT) were used as solid biofuel (SBF) for co-firing individually with coal in a commercial continuous chain-grate steam boiler system, which was conducted at fixed input rate of heating value of mixture of SBF and coal and at fixed airflow rate. The effects of key system parameters on the gaseous and particulate pollutions and ash were examined. These include SBF type and blending ratio (RBL) of biomass (i.e., SBF) in the mixture of coal and biomass based on heating values for co-firing.The results indicated that wood, which possesses high heating value while less amount of ash, is more suitable for co-firing with coal than rice straw. Torrefaction can increase the heating value of biomass and homogenize its property, being beneficial to co-firing. Also, torrefaction can decompose the hydroxyl group of biomass, which makes biomass tending to possess hydrophobicity. This, in turn, helps the storage and transportation of biomass. Generally, adding the RS (with RBL = 5-10%), WD (2-15%), RST (2-10%) and WDT (2-20%), respectively, with coal decreases the emissions of NOx and SO2, but increases that of CO (except RST). The emission of HCl is little. The addition of biomass also increases the emission of fine particulate matters (PM) especially PM2.5 in the flue gases, raising PM2.5/PM100 from 34.87 to 78.35 wt.% (Case 50%WDT). These emissions for the Cases tested satisfy with Taiwanese emission standards of stationary sources which set limitations of NOx, SO2, CO and HCl < 350, 300, 2000 and 80 ppmv, while PM < 50 mg/m3, respectively. The results support the use of RS, WD, RST and WDT for co-firing with coal.Implications: This study examined the suitability of using solid bio-fuels to co-fire with coal in an industrial chain-grate steam boiler system with a capacity of 100 kW, in order to achieve carbon-free emissions. Both biomass and torrefied biomass of solid bio-fuel were tested. The findings would be useful for proper design and rational operation of solid bio-fuel/coal co-firing combustion matching the appeal of sustainable material management and circular economy of biomass, and of adaptation of global warming induced by greenhouse gases. It also provides information for policy-makers to promote the co-firing application of biomass and related bio-waste materials.

Experimental evaluation of solar thermal performance of linear Fresnel reflector

The solar thermal performance of a 102 kW rated thermal capacity linear Fresnel reflector system was evaluated experimentally under fixed and variable airflow rate through the oil-air heat exchanger. The solar thermal system consisted of 240 mirrors (linear Fresnel solar reflectors), each of 1485 by 625 mm size to heat the thermal oil, which was used to heat the air using the oil to air heat exchanger (AFfE). The results show that the actual maximum efficiency of the solar collector lies in the range of 0.28 to 0.34, whereas the calculated one is about 0.54 for the variable airflow rates. However, for a fixed airflow rate, the actual maximum efficiency is between 0.26 and 0.30. It implies that the actual solar collector efficiency is much lower than the calculated values. One of the major factors, which is not accounted for in the theoretical efficiency calculation, is the effect of dust on the primary and secondary mirrors. The investigated site is observing considerable sand movement, which is affecting the thermal output of the solar collector. The maximum heat exchanger effectiveness, e, obtained for variable and fixed airflow conditions is 0.9 and 0.8, respectively.

Static Flame Stability of Circumferentially Arranged Fuel Port Inverse Jet Non-Premixed Flame Burner

ABSTRACT This paper presents experimental studies on flame appearance and static flame stability characteristics of inverse jet flame (IJF) using a circumferentially arranged fuel port (CAFP) burner by following two different methods, namely, Protocol I and Protocol II. In the case of Protocol I, experiments are conducted for a fixed air flow rate, by varying fuel flow rate whereas, in the case of Protocol II, by varying air flow rate for a fixed fuel flow rate. In Protocol I, the flame is lifted off from the burner rim unlike in Protocol II. Moreover, the flame base becomes unstable at higher fuel flow rate before the occurrence of flame liftoff for Protocol I. Momentum flux ratio (MFR) and overall equivalence ratio parameters are considered to obtain insights on the phenomenon with variation of flame liftoff height in CAFP-based IJF burner. An attempt has also been made to analyze the hysteresis effect on the flame liftoff. In contrast to the normal jet diffusion flame, the hysteresis effect is observed at lower MFR, and is absent particularly when the base flame gets strongly anchored to the burner rim for higher MFR. On the other hand, in Protocol II, with an increase in air velocity, the inverse jet diffusion flame is no longer diffusion controlled, rather mixing controlled. In addition, the flame blowoff for Protocol I is attributed to occurrence of leaner overall equivalence ratio obtained by reduction of fuel flow rate whereas global strain rate governs flame blowout for Protocol II. In addition to flame blowout and liftoff, the main flame for Protocol II experiences local extinction and re-ignition at certain conditions with increase in the global strain rate at certain threshold value. In addition, semi-empirical correlations based on Peclet number for main flame extinction, flame blowout and flame blowoff are proposed in the present study which can be employed for designing CAFP-based IJF-based combustor system.

Comparison of ozone production by DBDP reactors: difference external electrodes

Research on ozone generator performance technology of dielectric barrier discharge plasma (DBDP) has been conducted. The study was carried out by using two models of reactor configuration. The first model uses a wire mesh - aluminum foil configuration. The second model uses the wire mesh electrode configuration - wire mesh wrapped in aluminum foil. Ozone was generated using AC high Voltage. Oxygen that source of ozone has been taken from the water. The ozone was produced by DBDP reactor with voltage variation from 0.5 to 14 kV and a fixed air flow rate of 10 L / min. The first models of the reactor was Be Able to produce ozone of 138 ppm at a voltage of 14.3 kV with a maximum temperature of the inner reactor at 49 ° C. The second model of ozone produced with concentration of 163 ppm at a voltage of 14.2 kV and a maximum temperature of the inner reactor of 52 ° C. We found that reactor with wire mesh electrode configuration - wire mesh wrapped in aluminum foil can produce more high ozone concentration with the same voltage.

EVALUATION METHODS AND WAYS OF IMPROVING THE OPERATIONAL DEPENDABILITY OF MASS AIRFLOW SENSORS IN ENGINES

The design of today’s car engine electronic control system practically always includes an engine load sensor. Normally, its role is played by the intake manifold absolute pressure sensor or the mass airflow sensor. Film mass airflow sensors are the most common ones. The sensor is installed in the intake between the air filter and the throttle plate of the engine intake manifold. In the process of operation the sensor is exposed to pollution and ageing of the gauging element due to interaction with dust particles and motor oil fumes in the airflow. That causes the output signal to deviate from the reference values and consequently inaccurate calculation of the fuel blend composition by the electronic engine control system. Given the design of the sensors, they cannot be repaired and are replaced with new ones. A new sensor is quite costly. Given the above, it is obvious that the subject is of relevance. The aim of the paper is to find methods of evaluation and ways of improving the operational dependability of film mass airflow sensors installed in modern automobiles. The evaluation of sensor operability is based on the voltage of the sensor output signal. Using a diagnostic scanner plugged into the automobile’s diagnostics port in the analog-to-digital converter channel viewing mode the voltage of the sensor output signal is recorded, the fuel blend long-lasting correction factor is evaluated, and the presence of error codes associated with the malfunction of mass airflow sensor in the memory of electronic control unit is verified. A digital oscilloscope is used for measuring the voltage at the moment of ignition lock activation and the resting voltage at zero airflow, as well as the transient time. Based on the obtained findings it becomes obvious that the operational dependability of such sensors can only be improved by correcting the calibration tables of the mass airflow sensor stored in the memory of the engine control unit. Using a mass airflow sensor test stand, input data is prepared for the correction procedure. The reference and tested sensors are installed on the same vacuum pump nozzle, and the airflow rate is changed gradually. Under a fixed airflow rate the sensors’ output voltage is measured. The resulting data is summarized in a table and processed with the Chip Tuning PRO calibration software. As can be seen, one of the causes of the loss of the sensors’ operational dependability is the pollution of the sensing element. The layer of pollution on the sensing element reduces the coefficient of heat transmission between the airflow and the sensor’s gauging element. Based on the conducted research, the paper presents the results of changing sensor output signal in operation as compared to the reference values, suggests a method of correction of the calibration table of mass airflow sensor parameters in the engine control program stored in the memory of the electronic control unit, provides recommendations regarding the methods of evaluation and ways of improving the sensors’ operational dependability.

Gasification of coal water mixture in an entrained-flow gasifier: Effect of air and oxygen mixing ratio

Entrained-flow gasifiers used in commercial integrated gasification combined cycles are usually oxygen-blown. However, oxygen-blown gasification system is expensive to install and operate due to the equipment involved in oxygen purification and supply. To resolve this issue, this study mixed air and oxygen to perform coal gasification. An entrained-flow gasifier of 1 T/D scale was used with the coal water mixture as feedstock. Gasification was carried out at a temperature range of 970–1220 °C, an equivalence ratio of 0.25–0.62, and an air/O2 ratio of 2.17–9.0. With an increasing gasification temperature, the amount of CO in the syngas increased while CO2 and CH4 decreased. Carbon conversion and cold gas efficiency continued to increase with the gasification temperature. In the equivalence ratio test, cold gas efficiency reached 52.1% at around 0.53 before decreasing under a fixed air flow rate of 90 N m3/h. By performing gasification with a varying air/O2 ratio after fixing the flow rate, the influence of the equivalence ratio was examined. In addition, the influence of the flow rate was observed through changes in the air/O2 ratio of the gasification agent with fixing the equivalence ratio. The maximum carbon conversion and cold gas efficiency were 90.7 and 57.7%, respectively, and the optimal air/O2 ratio fell in the range of 2.86–3.1.