Teknologi emisi rendah: aplikasi aliran berpusar

Buku ini secara amnya menerangkan mengenai penggunaan teknologi pusaran udara untuk mengurangkan pembentukan emisi dari proses pembakaran seperti oksida nitrogen (NOx), karbon monoksida (CO) dan hidrokarbon tak terbakar (HC). Perbincangan dalam buku ini memfokuskan kemampuan pemusar udara aliran jejarian dengan pemboleh ubah kekuatan pusaran yang berupaya menambahbaik percampuran bahan api cecair dan udara serta mengawal pembentukan bahan cemar ketika dioperasikan pada tekanan ambien. Buku ini dipersembahkan dalam cara yang dirasakan dapat membantu pembaca untuk memahami masalah yang ditimbulkan dan bagaimana penggunaan teknologi pusaran dapat menyelesaikan masalah tersebut. Perlaksanaan penyelesaian yang dibincangkan merupakan gabungan daripada permodelan berkomputer serta ujikaji yang telah dijalankan di makmal. Permodelan berkomputer melibatkan analisis isoterma dan permodelan tindak balas (pembakaran) sementara keputusan ujikaji memberi lebih tumpuan kepada analisis emisi pembakaran. Walaupun tidak dinafikan terdapat pelbagai lagi kaedah yang dapat mengurangkan emisi, penulis merasakan teknologi pusaran yang dibentangkan dalam buku ini merupakan antara kaedah yang paling cekap dan mudah untuk dipraktikan dalam menghasilkan sebuah pembakar yang lebih mesra alam sekitar

Pengaruh nombor pusar ke atas pengurangan emisi NOx dari pembakar berbahan api cecair menggunakan pemusar udara aliran paksi

Pemusar udara, selain menstabilkan nyalaan adalah satu bentuk kawalan pasif bagi mengurangkan emisi gas pembakaran. Bahan cemar yang keluar bersama gas ekzos terdiri daripada gas oksida nitrogen (NOx). Gas ini amat merbahaya dan membawa kepada pencemaran udara sekeliling. Penggunaan udara pusar didapati dapat mengurangkan emisi NOx ini. Kekuatan pusaran diukur melalui nilai nombor pusar yang dapat dikira semasa merekabentuk pemusar udara. Kadar emisi ini bergantung kepada sudut pesongan bilah pemusar tersebut. Di dalam kajian ini, pemusar aliran paksi yang mempunyai sudut pesongan 40°, 50°, 60° dan 70° digunakan bagi membuktikan keberkesanan penggunaan pemusar udara aliran paksi ke atas pembakar dan pengaruh nombor pusar dalam mengurangkan emisi dari pembakar. Daripada ujikaji yang dijalankan dapat dilihat semakin tinggi nombor pusar, emisi NO semakin berkurangan. Emisi NOx menurun sebanyak 36% apabila menggunakan pemusar aliran paksi bersudut 70° dibandingkan dengan pemusar aliran paksi bersudut 40°

Combustor aerodynamic using radial swirler

A study has been conducted to investigate the flow pattern in a gas turbine combustion chamber by simulation and experimental approaches. Flow pattern inside a combustor is important to self sustain the flame, increase mixing of air and fuel, and increase combustion intensity. Aerodynamically curved vanes allow the incoming axial flow to turn gradually. This inhibits flow separation on the suction side of the vane. Thus, more complete turning and higher swirl and radial-velocity components can be generated at the swirler exit with the added advantage of lower pressure loss. The swirl number varied from 0.49, 1.29 and 2.29 for flat vanes and only 1.57 for curved vane. The highest swirl number of 2.29 for flat vane and 1.57 for curve vane are capable of creating a clear reversal mass flow rate zone and higher swirl strength reduces the corner recirculation zone size and hence reduces the negative impact on the combustion process and the homogeneity of the wall temperature as well. Further investigation can be done for higher swirl number for both types of swirler

Numerical analysis of effect of preheat and swirl of inlet air on temperature profile in canister burner

The main purpose of this paper is to study the Computational Fluid Dynamics (CFD) prediction on temperature distribution inside the canister burner with inlet air pre-heating of 100K and 250K while varying the swirl angle of the radial swirler. Air swirler adds sufficient swirling to the inlet flow to generate central recirculation region (CRZ) which is necessary for flame stability and fuel air mixing enhancement. Therefore, designing an appropriate air swirler is a challenge to produce stable, efficient and low emission combustion with low pressure losses. A liquid fuel burner system with different radial air swirler with 280 mm inside diameter combustor of 1000 mm length has been investigated. Analysis were carried out using four different radial air swirlers having 30°, 40°, 50° and 60° vane angles. The flow behavior was investigated numerically using CFD solver Ansys Fluent. This study has provided characteristic insight into the distribution of temperature inside the combustion chamber. Results show that with the inlet air preheat before the combustion, the temperature distribution inside the canister would stabilize early into the chamber with higher swirl number (SN) compared without inlet air preheat. As for the inlet air preheat, the main effects are the resulting temperatures in the canister are higher, but there is a smaller hot-spot in the flame. This means that the temperature profile in the chamber is well distributed

Experimental analysis on the formation of CO-NO-HC in swirling flow combustion chamber

The main purpose of this paper is to evaluate the production of CO-NO-HC emissions while varying the swirl angle of curve vane radial swirler. Swirling flow generates central recirculation region (CRZ) which is necessary for flame stability and enhances fuel air mixing. Therefore designing an appropriate air swirler is a challenge to produce stable, efficient and low emission combustion inside burner system. Four radial curved vane swirlers with 30o, 40o, 50o and 60o vane angles corresponding to swirl numbers of 0.366, 0.630, 0.978 and 1.427 respectively were used in this experiment to measure the vane angles effect on emission production in the combustion chamber. Emission measurements were conducted at 5 axial distances from the burner throat, and at 5 locations along the radius starting the central axis at each section. It was found that at the core near the throat, CO and HC concentrations are low due to high available O2 and high fuel mixing rate producing efficient combustion. This is due to the high shear region created the high swirl flow

Development of low liquid fuel Burnera

Recently, most of the gas turbine combustion research and development involves in lowering the emissions emitted from the combustor. Emission causes adverse affect to the world and mankind especially. Main concern of the present work is to reduce the NOx emission since the CO emission could be reduced through homogeneous mixing of fuel and air. Homogeneous mixing of fuel and air is also needed in order to reduce NOx emission. A liquid fuel burner system with radial air swirler vane angle of 30o, 40o, 50o and 60o has been investigated using 163mm inside diameter combustor. Orifice plates with three different sizes of 20mm, 25mm and 30mm were inserted at the back plate of swirler outlet. All tests were conducted using diesel as fuel. Fuel was injected at two different positions, i.e. at upstream and downstream of the swirler outlet using central fuel injector with single fuel nozzle pointing axially outwards. Experiment has been carried out to compare the three emissions NOx, CO and SO2. NOx reduction of about 53 percent was achieved for orifice plate of 20mm with downstream injection compared to orifice plate of 20mm with upstream injection. CO2 and SO2 was reduced about 26 percent and 56 percent respectively for the same configuration. This comparison was taken using swirler vane angle of 60o. The overall study shows that larger swirler vane angle produces lower emission results compared to the smaller ones. Smaller orifice plates produce better emission reduction. Meanwhile, downstream injection position significantly decreases the emission levels compared to upstream injection position. Combination of smallest orifice plate and largest swirler vane angle with downstream injection produce widest and shortest flame length

Pembangunan pembakar berbahan api cecair dengan ciri-ciri rendah NOx

A liquid fuel burner system with curved radial air swirler vane angles with swirl number variation between 0.046 to 1.911 has been investigated. A combustor with single central fuel nozzle is used to determine the effect of swirl number in emissions formation especially NOX as well as the other emissions such as CO, UHc and CO2. Swirling flow affect the formation of recirculation zone thus provides the aerodynamics blockage to stabilise the flame, improve mixing between air and fuel and affect formation of emissions. NOX reduction of more than 26% was observed as the swirl number increases from 0.046 to 1.427. In order to achieve an enhanced recirculation zone as well as to have a better control on mixing process, a swirler, which consist of an orifice plate at the outlet of radial swirler was introduced. The purpose of orifice plate insertion was to create pressure loss at the swirler outlet. The pressure loss contribute to the increase of the turbulence and hence assist in mixing of air and fuel. This technique has show a further increase in the reduction of NOX formation of about 22%. Air staged combustion has also been recognised as other solution to further reduce emissions from combustion process. The secondary air introduced downstream of the fuel rich primary zone help to complete the combustion and reduced the formation NOX by suppressing the increase in combustion temperature. This technique has also shown on improvement in the reduction of NOX emissions for about 18%

The reduction of noxious emissions using urea based on selective non-catalytic reduction in small scale bio fuel combustion system

Selective Non-Catalytic Reduction (SNCR) of oxides of nitrogen (NOx) was studied experimentally by injecting different concentrations of aqueous urea solution in a pilot-scale Bio-fuel fired tunnel furnace at 3-4 % excess oxygen level and with low ppm of baseline NOx ranging from 65 to 75 ppm within the investigated temperature range. The furnace simulated small-scale combustion systems where the operating temperatures are usually in the range of about 973 to 1323 K and NOx emission level remains below 100 ppm. NOx reductions were studied with the variation of different parameters such as injection temperature, residence time, Normalized Stoichiometric Ratio (NSR) of the reagent, carrier gas pressure, etc. A significant amount of NOx reduction was achieved which was not pronounced by the previous researchers with urea SNCR for this low ppm of NOx. With 5% plain urea solution, at an NSR of 4 as much as 54% reduction was achieved at 1128 K, whilst in the additive case the NOx reduction was improved to as much as 69% at 1093 K

Noxious emission reduction from liquid fuel burner via air staging method

Combustion implicates harmful effect to the environment due to the emissions produced. The release of gaseous emissions such as oxides of nitrogen (NOX) and carbon monoxide (CO) into the atmosphere create major environment problems. These gaseous emissions affect plants, human being and animals. High concentration of emissions brings fatal effects to life form. Air staging or two-stage combustion, is generally described as the introduction of additional/secondary air into the boiler or furnace. Staging the air into the burner (internal air staging) is generally one of the design features of low NOX burner. Staged combustion is the technique in which a high temperature, fuel rich primary zone is generated with a sufficient residence time to minimize the total fixed nitrogen that is formed in the primary zone. The secondary air mixes downstream of the primary zone to complete the combustion. Staged combustion is an effective method of controlling thermal NOX. A study has been conducted to demonstrate the effectiveness of air staging in reducing emissions from combustion process. A liquid fuel burner system with 280 mm inside diameter combustor of 1000 mm length has been investigated. All tests were conducted using commercial diesel as fuel. The study shows that a much lower NOX emissions were obtained for the staged combustion when compared to the non-staged combustion. Significant reduction of more than 15 percent of NOX emissions reduction was obtained

The used of aqueous urea solution in reduction of noxious emissions in bio fuel combustion system using selective non-catalytic reduction

Selective Non-Catalytic Reduction (SNCR) of nitric oxide was studied experimentally by injecting different concentrations of aqueous urea solution; urea and ammonia in a pilot-scale Bio-fuel fired tunnel furnace at 3-4 % excess oxygen level and with low ppm of baseline NOx ranged from 65 to 75 ppm within the investigated temperature range. The furnace simulated small-scale combustion systems where the operating temperatures are usually in the range of about 973 to 1323 K and NOx emission level remains below 100 ppm. NOx reductions were studied with the variation of different parameters such as injection temperature, residence time, Normalized Stoichiometric Ratio (NSR) of the reagent, carrier gas pressure, etc. A significant result shows that for NSR, at higher NSR, ammonia could give significant reduction of NOx at the investigated injection temperature. Meanwhile, for the effect of residence time, both aqueous solution shows that the NOx reduction increased with increase in residence time. Finally for the effect on injection temperature, both aqueous solution, up to a certain temperature NOx reduction continued to increase with increasing injection temperature and afterward the reduction decayed with further increase in temperature