Prediction of lean blowout performance on variation of combustor inlet area ratio for micro gas turbine combustor

Purpose This paper aims to predict the effect of combustor inlet area ratio (CIAR) on the lean blowout limit (LBO) of a swirl stabilized can-type micro gas turbine combustor having a thermal capacity of 3 kW. Design/methodology/approach The blowout limits of the combustor were predicted predominantly from numerical simulations by using the average exit gas temperature (AEGT) method. In this method, the blowout limit is determined from characteristics of the average exit gas temperature of the combustion products for varying equivalence. The CIAR value considered in this study ranges from 0.2 to 0.4 and combustor inlet velocities range from 1.70 to 6.80 m/s. Findings The LBO equivalence ratio decreases gradually with an increase in inlet velocity. On the other hand, the LBO equivalence ratio decreases significantly especially at low inlet velocities with a decrease in CIAR. These results were backed by experimental results for a case of CIAR equal to 0.2. Practical implications Gas turbine combustors are vulnerable to operate on lean equivalence ratios at cruise flight to avoid high thermal stresses. A flame blowout is the main issue faced in lean operations. Based on literature and studies, the combustor lean blowout performance significantly depends on the primary zone mass flow rate. By incorporating variable area snout in the combustor will alter the primary zone mass flow rates by which the combustor will experience extended lean blowout limit characteristics. Originality/value This is a first effort to predict the lean blowout performance on the variation of combustor inlet area ratio on gas turbine combustor. This would help to extend the flame stability region for the gas turbine combustor.

Numerical and Experimental Investigations on Performance Optimization of a Microturbojet Engine Combustor

Sudden extinction of a microturbojet engine combustor was encountered during the engine accelerating process, which motivates the present work to optimize the combustor performance. Numerical results show that by decreasing the primary zone air-introducing area and increasing the dilution zone air-introducing area, the primary zone air percentage is reduced from 39.35% to 32%, and the primary zone excess air ratio is reduced from 1.122 to 0.915, which is believed to be beneficial for flame stability both in terms of residence time and rich burn. Meanwhile, the vortex flow pattern in the primary zone varies little as the variations of the airflow distribution. The new engine, which is equipped with the optimized combustor, is tested by experiments. The successful accelerating to the rotating design speed demonstrates the effectiveness of combustor optimization work.

Design and Validation of a Novel Test-Rig for RQL Flame Dynamics Studies

In this paper a novel test-rig for the investigation of low-frequency thermoacoustic instabilities in aero-engines with air-staging RQL (rich-quench-lean) is presented. The new approach is to separate the rich primary zone from the lean secondary zone to allow for an isolated thermoacoustic characterization of each combustion zone. In addition the test-rig offers the possibility to combine both zones to judge the transferability of the findings from the separated to the compact configuration. The high modularity of the test-rig is already considered in the design-phase and allows a cost and time efficient manufacturing. Heat losses in the primary zone and the transition duct between the two zones play a crucial role for the functionality of the facility and are estimated during design to guarantee a stable re-ignition in the secondary zone. The main design steps in the secondary zone for achieving complete burn-out of the hot primary combustion gases are described. The realization of the acoustic excitation via loudspeakers is described and damping measures to improve combustor stability are explained. The operation of both zones, their acoustic behavior and the operational limits of the test-rig are demonstrated experimentally. They include first thermoacoustic measurement data of naturally occurring instabilities, the corresponding eigenfrequencies and the validation of the test-rig design. Finally an outlook on the future work in the research project concludes this paper.

Computational and Experimental Analysis of a Compact Combustor Integrated into a JetCat P90 RXi

Ultra Compact Combustors (UCC) look to reduce the overall combustor length and weight in modern gas turbine engines. Previously, a UCC achieved self-sustained operation at sub-idle speeds in a JetCat P90 RXi turbine engine with a length savings of 33% relative to the stock combustor. However, that combustor experienced flameout as reactions were pushed out of the primary zone before achieving mass flow rates at the engine's idle condition. A new combustor that utilized a bluff body flame stabilization with a larger combustor volume looked to keep reactions in the primary zone within the same axial dimensions. This design was investigated computationally for generalized flow patterns, pressure losses, exit temperature profiles, and reaction distributions at three engine power conditions. The computational results showed the validity of this new Ultra Compact Combustor, with a turbine inlet temperature of 1080 K and a pattern factor of 0.67 at the cruise condition. The combustor was then built and tested in the JetCat P90 RXi with rotating turbomachinery and gaseous propane fuel. The combustor maintained a stable flame from ignition through the 36,000 RPM idle condition. The engine ran self-sustained from 25,000 to 36,000 RPM with an average exit gas temperature of 980 K, which is comparable to the stock engine.

Internal Friction and Compressive Deformation in the Primary Zone during the High-Speed Cutting of SiCp/Al Composites

The present work proposes that there is internal friction and compressive deformation in the primary zone. Mathematical model was established, in which the internal friction coefficient and some compressive characteristics of serrated chips were calculated. High-speed orthogonal cutting experiment was performed on SiCp/Al composites at cutting speeds of 10–350 m/min and feed rates of 0.07–0.12 mm/r. The internal friction and compressive deformation in the primary zone were investigated by combing results obtained in the experiments with the mathematical model. The internal friction coefficient (0.21–0.47), compressive stress (185.4 MPa–226.9 MPa), and compressive strain rate (0.013×104 /s–0.554×104 /s) increased with increasing cutting speed. However, the compression value (17.3 µm–50.0 µm) and compressive strain (0.18–0.26) decreased with the cutting speed.

A CFD study on hydrocarbon mean residence time in a horizontal oil–water separator

This study presents computational fluid dynamics analyses on oil–water flow characteristics in a horizontal separator. The performance of these vessels are inferred from mean residence time and cumulative residence time distribution of the hydrocarbon phase inside the separator. The authors model a separator used by previous researchers and evaluate mean residence time of the hydrocarbon phase in a two-phase mixture of oil and water. Three different water-cuts of 21%, 32%, and 57% are used. Additional analyses are done to assess how certain geometric features of the separator influence hydrocarbon mean residence time. The results show that the addition of a second perforated baffle plate does not improve the hydrocarbon mean residence time significantly. However, introducing a downward slanting throat section between the primary zone and the gravity separation zone improves the hydrocarbon mean residence time at 21% and 32% water-cuts. The results suggest oil–water separators with a throat section may be more efficient than regular horizontal separators without the throat section at low water-cuts.

Study on the Hybrid Cooling of the Flame Tube in a Small Triple-Swirler Combustor

An experimental and numerical investigation is conducted to study the influence of different cooling schemes on the wall temperature of the flame tube in a small triple-swirler combustor in this paper. Two different cooling structures are adopted: the impingement-film and inclined multi-hole cooling structure (Scheme B, C), and the inclined multi-hole control group (Scheme A). The impact of parameters including inlet temperature (373–423 K), inlet Mach number (Ma) (0.12–0.18), and fuel–air ratio (FAR) (0.02–0.03) are discussed. The results show that the wall temperature of the flame tube rises with the increase in inlet temperature; as the inlet Mach number increases, the wall temperature (Scheme B, C) of the primary zone goes up and is distributed more uniformly; as FAR rises, the wall temperature in Scheme C is nearly unchanged, while it is increased in Scheme A and B. For the range of parameters considered in this study, the lowest wall temperature and the best cooling effect are observed in Scheme C. The experiment conducted on the impingement-film and inclined multi-hole structure shows a better cooling effect than that conducted on the traditional inclined multi-hole structure. Compared with the row number of multi-inclined holes, the diameter of jet hole has a more significant influence on the cooling effect.

BEHAVIOUR OF SULFUR, ARSENIC AND ORGANIC CARBON IN A GRAVITY CONCENTRATION OF GOLD FROM REFRACTORY ORE

The results of assay-gravimetric, chemical, mineralogical analyzes of gold ore are presented. According to the content of sulfide sulfur and the degree of oxidation of sulfur gold-bearing ore is assigned to the poor sulfide type of ore in the primary zone. Gold ore refers to refractory carbonaceous arsenic-containing sulfide ores. The gravity concentration of ore was assessed using a laboratory 3-inch Knelson KC-MD3 centrifugal concentrator. According to the results of the GRG test, the total gold extraction was 39.58% with the total concentrate yield of 3.96%. The extraction of gold in the first stage is lower than in the subsequent stages. This indicates the absence of large gold in the ore. The behavior of sulfur and arsenic during gravity concentration is similar to the behavior of gold. These data confirm that the main amount of gold is associated with arsenopyrite (arsenic pyrite) and pyrite. The behavior of organic carbon during gravity is significantly different. Only 3.39% of organic carbon passes into the gravity concentrate from ore, which reduces the persistence of the concentrate. Most of the organic carbon (96.61%) remains in the tails of gravity. The content of components in the total gravity concentrate was: Au 21.63 g/t, S 6.40%, As 0.82%, C(organic) 0.58%. The extraction of the components in the total concentrate is as follows, %: Au 39.58; S 34.52; As 27.27; C(organic) 3.39.

Pressure Gain Combustion by Using Shock Flame Interaction Pressure Rise

Pressure loss across a combustor in a gas turbine reduces thermal efficiency and increases specific fuel consumption. Theoretically, any pressure gain across the combustor results in higher thermal efficiency and lower specific fuel consumption. This work aims to obtain ‘time-averaged pressure rise across the combustor by using shock-flame interaction’. Multiple shock flame interaction increases the chemical heat release rate by two orders of magnitude. In this study, an impulsive heat addition for 30 microseconds with different heat release rates (10,30 and 100) is applied to a spherical zone within the primary zone of the combustor after a quasi-steady URANS combustion and the results are evaluated. A further study, the experimental part, will be based on shock flame interaction with different strengths of shocks. Inlet and outlet total pressures will be measured via high-pressure and high-temperature pressure transducers. Any pressure gain combustion can save billions of USD as gas turbines consume 13.9% of the total energy consumption.