Real-time simulation of the TF30-P-3 turbofan engine using a hybrid computer

A real-time, hybrid-computer simulation of the TF30-P-3 turbofan engine was developed. The simulation was primarily analog in nature but used the digital portion of the hybrid computer to perform bivariate function generation associated with the performance of the engine's rotating components. FORTRAN listings and analog patching diagrams are provided. The hybrid simulation was controlled by a digital computer programmed to simulate the engine's standard hydromechanical control. Both steady-state and dynamic data obtained from the digitally controlled engine simulation are presented. Hybrid simulation data are compared with data obtained from a digital simulation provided by the engine manufacturer. The comparisons indicate that the real-time hybrid simulation adequately matches the baseline digital simulation

Method of discrete modeling and its application to estimation of TF30 engine variables

A method of discrete modeling is presented that effectively isolates steady state model accuracy from dynamic model accuracy. The steady state model may be generated from the engine design equations with any desired degree of accuracy. The dynamic model is generated by applying a step disturbance of a manipulated variable to an open loop engine simulation. The sampled response of the variable is combined with the steady state model's response to form a set of weighting factors. These weighting factors are then used to weight past values of the manipulated variable, thus forming the dynamic model. The method is used to estimate various TF30-P-3 engine variables. A dynamic trim function is developed to compensate for the dynamic nonlinearities of the variables as well as for inaccuracies in dynamic definition. The trim function is shown to be realted to the square root of the sum of the squares of the weighting factors obtained at various engine operating conditions. Finally, the estimation of variables without dynamic modeling is discussed

Study of turbojet combustor dynamics using sweep-frequency data

Sweep frequency nozzle pressure oscillation effects on turbojet combustor dynamic

Design and evaluation of a sensor fail-operational control system for a digitally controlled turbofan engine

A self-learning, sensor fail-operational, control system for the TF30-P-3 afterburning turbofan engine was designed and evaluated. The sensor fail-operational control system includes a digital computer program designed to operate in conjunction with the standard TF30-P-3 bill-of-materials control. Four engine measurements and two compressor face measurements are tested. If any engine measurements are found to have failed, they are replaced by values synthesized from computer-stored information. The control system was evaluated by using a realtime, nonlinear, hybrid computer engine simulation at sea level static condition, at a typical cruise condition, and at several extreme flight conditions. Results indicate that the addition of such a system can improve the reliability of an engine digital control system

Waste Cooking Oil-to-Biodiesel Conversion for Space Heating Applications

Transesterification is a process that converts triglycerides, like vegetable oil, into fatty acid methyl esters, commonly known as biodiesel. This conversion reaction requires the triglyceride feedstock, an alcohol, and an alkali-catalyst to produce the biodiesel. Biodiesel is a versatile biofuel that is renewable, biodegradable, and environmentally beneficial in the sense that combustion adds only biogenic carbon to the atmosphere. The main limitation of commercialization of biodiesel is cost. However, developing closed-loop systems that have an available triglyceride supply, such as waste cooking oil, as well as demand for diesel based fuels, can achieve substantial emissions reductions and energy avoidance, while simultaneously solving a waste disposal issue. Thus, an analysis of the development of a closed-loop waste cooking to biodiesel fuel production process is warranted. A waste-to-energy (WtE) system like this offers great potential to institutions. Thus, this analysis includes the development of a waste cooking oil to biodiesel fuel program utilizing the available waste cooking oil of a university, the production of the fuel, the internal use of the fuel, and subsequent analysis of the fuel characteristics, emissions, and the life cycle environmental and energy impacts of the production process and ultimate use. The results show that the waste cooking oil derived biodiesel meets the required American Society for Testing and Materials (ASTM) standard specifically for biodiesel, ASTM D6751. The produced biodiesel was blended with commercially available fuel oil, which met the ASTM specification D396-13b. Therefore, a blend of these two ASTM compliant fuels also met the required ASTM standards. The ASTM standards require high quality fuel characteristics and ensure proper utilization and combustion. Biodiesel blended heating fuels were utilized in two distinct heating facilities, both showing comparable emissions to conventional fuel oil. Small (500 mL) and large (1L) volume biodiesel blends were utilized in a conventional residential furnace. Emissions data were obtained through the exhaust ducting with a combustion gas analyzer. The same fuel blends were utilized in a lab-scale burner apparatus without a heat exchanger, which enabled near-flame interrogation and visualization of the combustion process. The emissions of both heating facilities were comparable to the incumbent fuel oil. The life cycle assessment results demonstrate the benefits of increasing the approved blends of biodiesel heating fuels. Currently, most oil burners are only approved up to a B5 blend (5% biodiesel, 95% fuel oil). The results show higher blends achieve substantial life cycle reduction in global warming potential and cumulative energy demand, as well as an energy return on investment of above 4, indicating more energy is obtained from the fuel than required to produce it

Labour Migration and Shadow Prices

The effect of migration and home remittances on the shadow prices of labour and foreign exchange is analysed here , taking into consideration changes in their social marginal productivities. It is argued that appreciation of currency, due to large capital inflows and not to increased productivity, results in a misallocation of resources, and, therefore, there is an urgent need for a proper analysis to determine the optimal level of emigrants

LAND DRAINAGE POLICY IN IRELAND. DUBLIN, 1982

Ireland suffers from an extensive drainage problem. The source of the difficulty is not exception rainfall. It is the saucer shape of the countryside with its high maritime rim and flat interior. As a result, the rivers flow slowly through poor channels. Much of the land suffers from periodic or prolonged flood damage. Even at low-flow, the rivers provide poor outfalls that prevent adjoining lands being properly drained. If left unattended, these slow-flowing rivers tend to silt up and the drainage conditions degenerate. So, the need for remedial drainage work is recurrent. State involvement in arterial drainage has a long history, dating back to famine times. At that time, the work was all done manually, and it employed about forty thousand people at peak. The process has now become highly mechanised with the use of dragline excavators and floating dredgers for excavation, and specialised equipment for drilling and blasting rock. It is all carried out under the central direction of the Office of Public Works (OPW). Fewer than one thousand people are now employed on the programme. Almost all of the arterial work has consisted of deepening and widening river channels to accommodate existing river flows. The alternative - moderating river flows by diverting rivers or storing in reservoirs - is uncommon. Schemes are designed after the study of long records of water flows and a detailed survey of the catchment. Typically, the channel enlargement aims to give immunity from the three-year flood and to reduce the low-flow water table sufficiently so that satisfactory drainage is achieved of the land areas to be improved. This level of flood immunity means that flooding in the Spring-Autumn growing season will be very rare. The low water table provides sufficient outfall to enable farmers to fully rehabilitate their land by field drainage. State involvement in field drainage is of quite recent origin. It takes the form of grant aid. The one experiment in direct work by tile state proved unwieldy and was short-lived. The grant is administered by the Department of Agriculture

A lumped parameter mathematical model for simulation of subsonic wind tunnels

Equations for a lumped parameter mathematical model of a subsonic wind tunnel circuit are presented. The equation state variables are internal energy, density, and mass flow rate. The circuit model is structured to allow for integration and analysis of tunnel subsystem models which provide functions such as control of altitude pressure and temperature. Thus the model provides a useful tool for investigating the transient behavior of the tunnel and control requirements. The model was applied to the proposed NASA Lewis Altitude Wind Tunnel (AWT) circuit and included transfer function representations of the tunnel supply/exhaust air and refrigeration subsystems. Both steady state and frequency response data are presented for the circuit model indicating the type of results and accuracy that can be expected from the model. Transient data for closed loop control of the tunnel and its subsystems are also presented, demonstrating the model's use as a control analysis tool

THE MACROECONOMIC EFFECTS OF COUNTERPART FUNDS

Summary This article discusses the major macroeconomic effects of counterpart funds. These include their effects on the money supply, the balance of payments, government finances, and inflation. While the macroeconomic effects of aid and counterpart funds may be important in some countries at some times, in most countries they are probably too small to cause much instability or contribute much to stabilization efforts. We present some evidence on these issues. Résumé Les effets macro?économiques des fonds de contrepartie Cet article présente une discussion des principaux effets macro?économiques des fonds de contrepartie, y compris l'effet de ces derniers sur la masse monétaire, sur la balance des paiements, sur les finances gouvernementales, et sur l'inflation. S'il est vrai que les effets macro?économiques de l'aide et des fonds de contrepartie sont importants dans certains pays à certaines époques, dans la plupart des pays leur influence est probablement trop restreinte pour créer une instabilité perceptible ni encore pour contribuer aux efforts de stabilisation. Les auteurs présentent de l'évidence relative à ces questions. Resumen Los efectos macroeconómicos de los fondos de contrapartida El artículo examina los principales efectos macroeconómicos de los fondos de contrapartida. Estos incluyen: efectos en la provisión de dinero, la balanza de pagos, las finanzas del Estado, y la inflación. Si bien los efectos macroeconómicos de la asistencia y los fondos de contrapartida pueden ser importantes en algunos países en épocas determinadas, en la mayoría de los casos son demasiado pequeños para provocar inestabilidad o contribuir mucho a los esfuerzos de estabilización. En el artículo se presentan evidencias de estas conclusiones