Thermodynamic Equilibrium Analysis of Rice Husk Pyrolysis

Pyrolysis of biomass materials can implement the efficient conversion of biomass to gaseous, liquid and solid energy products. Compared with experimental research which needs massive apparatus and funds and also takes long time, the computer simulation of biomass pyrolysis is more convenient and flexible to achieve the main characteristics of the process. Simulation of thermodynamic equilibrium for the pyrolysis of rice husk was studied in this paper. Based on the minimization of Gibbs free energy, MATLAB was used to calculate thermodynamic equilibrium for the pyrolysis of rice husk in the temperatures ranges from 523 K to 1723 K at intervals of 100 K. The results showed that the contents of H2 and CO increased rapidly with the temperature from 723 K to 1223 K, while the contents of H2O, CH4, CO2 and C decreased sharply. When the temperature was higher than 1223 K, the yields of H2 and CO reached the maximum of 51 mol% and 48 mol% respectively, and then kept stable. In order to be closer to experimental results, the constrain conditions of element C in tar was introduced in the calculations. The results indicated that, in the main components of tar from 523 K to 1223 K, the contents of naphthalene and toluene both decreased and then toluene vanished gradually. However, the content of benzene increased with increasing temperature and finally became the dominant product when the temperature was above 1300 K.

Ceramic Gas Turbine Development: Need for a 10-Year Plan

Ceramic gas turbine development that started in the 1950s has slowed considerably since most of the large-scale ceramic gas turbine development programs of the 1970s–1990s ended. While component durability still does not meet expectations, the prospect of significant energy savings and emissions reductions, potentially achievable with ceramic gas turbines, continues to justify development efforts. Four gas turbine applications have been identified that could be commercially attractive: a small recuperated gas turbine (microturbine) with ∼35% electrical efficiency, a recuperated gas turbine for transportation applications with ∼40% electrical efficiency with potential applications for efficient small engine cogeneration, a ∼40% efficient mid-size industrial gas turbine and a ∼63% (combined cycle) efficient utility turbine. Key technologies have been identified to ensure performance and component durability targets can be met over the expected life cycle for these applications. These technologies include: a Si3N4 or SiC with high fracture toughness, durable EBCs for Si3N4 and SiC, an effective EBC/TBC for SiC/SiC, a durable Oxide/Oxide CMC with thermally insulating coating, and the Next Generation CMCs with high strength that can be used as structural materials for turbine components for small engines and for rotating components in engines of various sizes. The programs will require integrated partnerships between government, national laboratories, universities and industry. The overall cost of the proposed development programs is estimated at U.S. $100M over ten-years, i.e. an annual average of U.S. $10M.

Performance Comparison of More Electric Engine Configurations

An analytical study was undertaken to investigate the fuel burn potential of More Electric Engine (MEE) configurations using the performance model of a 2-shaft high BPR 20–30 klbf turbofan in revenue service. The 3 following power off-take configurations were compared: an HP-generator, an LP-generator, and a split-power generator (small HP starter/generator and a main LP generator). For this study, because of the small performance differences, high accuracy steady-state and transient performance models must be used. For steady-state operating conditions, the design point was modified and the off-design redline margins were calculated; ground and flight idle settings were adjusted to yield both the lowest possible fuel burn and residual thrust within the surge margin of the compressor, and the resulting short range mission fuel burn was calculated. For transient conditions, the thrust response, as well as both HPC and LPC surge margin lapse during engine acceleration and deceleration, had to maintain those of the baseline engine and fulfill certification requirements. This was achieved by modifying the idle settings and acceleration/deceleration schedules. Subsequently, the resulting short range mission fuel burn was calculated. Lastly, an introduction to the business case is provided with a simple cost-effectiveness calculation. This study was an initial investigation into MEE’s that focused primarily on the propulsion unit. For further in-depth studies, it is recommended to consider in detail the business model, aircraft weight issues, and the interaction propulsion performance and aircraft performance.

Misalignment in Gas Foil Journal Bearings: An Experimental Study

As gas foil journal bearings become more prevalent in production machines, such as small gas turbine propulsion systems and microturbines, system level performance issues must be identified and quantified in order to provide for successful design practices. Several examples of system level design parameters that are not fully understood in foil bearing systems are thermal management schemes, alignment requirements, balance requirements, thrust load balancing, and others. In order to address some of these deficiencies and begin to develop guidelines, this paper presents a preliminary experimental investigation of the misalignment tolerance of gas foil journal bearing systems. Using a notional gas foil bearing supported rotor and a laser-based shaft alignment system, increasing levels of misalignment are imparted to the bearing supports while monitoring temperature at the bearing edges. The amount of misalignment that induces bearing failure is identified and compared to other conventional bearing types such as cylindrical roller bearings and angular contact ball bearings. Additionally, the dynamic response of the rotor indicates that the gas foil bearing force coefficients may be affected by misalignment.

Multi-Stage Compressor Model for Transient Performance Simulations

This paper describes the development of a multi-stage compressor model for transient performance calculations. The aim of the model is to simulate the interaction of the compressor stages with each other and the rest of the engine components during transient engine maneuvers. Especially rematching effects caused by transient heat flows and tip clearance changes are of interest, since they have a major impact on the stability of the compressor. In the first section of the paper the stage stacking ability is implemented in the performance tool. Therefore the compressor is split into several stages each of which is represented by a single compressor module. The specifics of this approach are discussed and the validity of the multi-stage model is shown by a comparison with results calculated with a conventional compressor model. Then the model is extended to simulate transient heat flows and tip clearance changes in each compressor stage. This is achieved by a state space approach which allows the calculation of the thermo-mechanical effects based on a set of previously identified matrices. The thermal calculation modules are linked to the performance model, and the quality of the combined simulation is shown by a comparison of results for two transient maneuvers with reference data. Finally the stage working line excursions of an acceleration are compared with those of a hot reslam demonstrating the advantage of the combined multistage performance model.

Compliant Foil Journal Bearing Performance at Alternate Pressures and Temperatures

An experimental test program has been conducted to determine the highly loaded performance of current generation gas foil bearings at alternate pressures and temperature. Typically foil bearing performance has been reported at temperatures relevant to turbomachinery applications but only at an ambient pressure of one atmosphere. This dearth of data at alternate pressures has motivated the current test program. Two facilities were used in the test program, the ambient pressure rig and the high pressure rig. The test program utilized a 35 mm diameter by 27 mm long foil journal bearing having an uncoated Inconel X-750 top foil running against a shaft with a PS304 coated journal. Load capacity tests were conducted at 3, 6, 9, 12, 15, 18, and 21 krpm at temperatures from 25°C to 500°C and at pressures from 0.1 to 2.5 atmospheres. Results show an increase in load capacity with increased ambient pressure and a reduction in load capacity with increased ambient temperature. Below one-half atmosphere of ambient pressure a dramatic loss of load capacity is experienced. Additional lightly loaded foil bearing performance in nitrogen at 25°C and up to 48 atmospheres of ambient pressure has also been reported. In the lightly loaded region of operation the power loss increases for increasing pressure at a fixed load. Knowledge of foil bearing performance at operating conditions found within potential machine applications will reduce program development risk of future foil bearing supported turbomachines.

Parametric Analysis of Variable Nacelle Nozzle Throat Area Using Warped Chevrons

Simulations of the NASA Rotor 67, Stator 67A stage integrated into a bespoke nacelle were performed using ANSYS CFX. The throat area of the nacelle nozzle was varied by use of warped chevrons. 8, 12 and 16 chevron nozzles were simulated to evaluate the impact of the variation in geometry upon the nacelle wake and local forces. The force produced from the nozzle and fan, is compared to the baseline case where the throat area is optimised for cruise conditions. The variation in gross thrust between cases is also analysed. The turbulence kinetic energy and total temperature variation through the wake is compared. A reduction in peak wake mixing massflow-averaged turbulent kinetic energy of 11.9% was attained. Surface force measurements of the rotor, stator and nozzle duct indicate a rising thrust loss with increasing nozzle throat area. However, measurement of the nozzle exit velocities and massflow rates enable subsequent estimation of the gross thrust which indicate a rise of 2.4% relative to the baseline is achievable.

Damage Evolution and Failure Mechanisms for APS-TBCS

Thermal barrier coatings (TBC-s) have been utilized in gas turbine engines for over two decades, primarily to protect the existing materials under the demands for higher temperatures and greater engine efficiency. Atmospheric Plasma Sprayed TBC, commonly used for hot combustion chamber components of advanced gas turbines, are exposed to thermo-mechanical loads, which may lead to failure in form of macroscopic spallations from the metallic component. The durability of TBC is limited by the interaction of different processes and parameters, such as bond coat oxidation, cyclic strains, visco-plastic and relaxation properties, interface roughness and others. In this work, the spallation failure mechanisms and damage evolution of APS-TBC system are investigated on samples aged by isothermal and thermal cycle tests using different time and temperatures exposures. Several parameters have been analyzed by SEM and a life prediction model approach for APS-TBC is being developed focusing on oxidation kinetics, identifying the parameters such as rumpling, bond coat oxidation, TGO thickness and interdiffusion of base metal elements which drive the oxide formation and TBC spallation mechanisms.

Three-Dimensional Stress Analysis and Configuration Optimization of Cross Wavy Primary Surface Recuperator for Microturbine System

Recuperator in a microturbine system, which has to work under a high temperature and high pressure condition, is a key component to improve the electricity efficiency of the system. High temperature and pressure may cause high stress inside the Cross-Wavy Primary Surface (CWPS) sheet, and it is essential to analyze the stress distribution to ensure the security while the recuperator is working. In this paper the combined thermomechanical design of a CWPS recuperator for a 100kW microturbine system is presented. With the ANSYS Parametric Design Language (APDL), calculation procedures for heat transfer and stress analysis are combined in order to perform a reliable strength prediction of the recuperator. A program has been generated, which allows the automatic generation of the numerical model, the mesh and the boundary conditions. Also with the energy minimum principle, an optimal configuration of the air and gas passages is obtained. The results show that the material of the primary sheet (0Cr18Ni11Nb) is reliable. The stress distribution changes with the different configuration of the passages. Since the air pressure is much higher than that of the exhaust gas, the configuration of the primary sheet is much better when the sectional area of the gas passage is larger than that of the air passage. If the pitch of the sheet is maintained at 2mm, the best configuration is obtained when the dimension of passage is at r = 0.35–0.42mm, R = 0.55–0.48mm.

Fischer-Tropsch Fuel Characterization via Microturbine Testing and Fundamental Combustion Measurements

Synthetic fuels such as Fischer-Tropsch (FT) fuels are of interest as a replacement for aviation, diesel, and other petroleum-based fuels, and the present paper outlines a joint program to study the combustion behavior of FT synthetic fuels. To this end, shock-tube spray and high-recirculation combustion rig experiments are being utilized to study the ignition delay times, formation of soot, and emissions of FT jet fuels. Undiluted shock tube spray experiments were conducted using a recently developed heterogeneous technique wherein the fuel is sprayed directly into the test region of a shock tube. The high recirculation combustion rig is a complete gas turbine system where Syntroleum FT jet fuel was combusted, and soot formation and emission characteristics were observed. Reduction of soot volume fraction and unchanged emissions were observed, in agreement with previous investigations. The fundamental shock tube results were found to be consistent with the observations made in the experimental engine.