Nonlinear Sliding Mode Control Design for an Air-breathing Engine with State Estimation

A modern system theory based nonlinear control design is discussed in this paper for successful operation of an air-breathing engine operating at supersonic speed. The primary objective of the control design of such an air-breathing engine is to ensure that the engine dynamically produces the thrust that tracks a commanded value of thrust as closely as possible by regulating the fuel flow to the combustion system. However, since the engine operates in the supersonic range, an important secondary objective is to manage the shock wave configuration in the intake section of the engine which is manipulated by varying the throat area of the nozzle. A nonlinear sliding mode control technique has been successfully used to achieve both of the above objectives. In this problem, since the process is faster than the actuators, independent control designs are also carried out for the actuators as well to assure the satisfactory performance of the system. Moreover, to filter out the sensor and process noises and to estimate the states for making the control design operate based on output feedback, an Extended Kalman Filter based state estimation design is also carried out. The promising simulation results suggest that the proposed control design approach is quite successful in obtaining robust performance of the air-breathing engine.

Diesel Engine Driven Stand-Alone Variable Speed Constant Frequency Slip Ring Induction Generator - Theory and Experimental Results

The operation of a stand-alone, as opposed to grid connected generation system, using a slip-ring induction machine as the electrical generator, is considered. In contrast to an alternator, a slip-ring induction machine can run at variable speed and still deliver constant frequency power to loads. This feature enables optimization of the system when the prime mover is inherently variable speed in nature eg. wind turbines, as well as diesel driven systems, where there is scope for economizing on fuel consumption. Experimental results from a system driven by a 44 bhp diesel engine are presented. Operation at subsynchronous as well as super-synchronous speeds is examined. The measurement facilitates the understanding of the system as well as its design.

Comparison of heat transfer correlations for cryogenic engine thrustchamber design

A comparative study of the correlations available in the literature is made to arrive at an appropriate pair for estimating the coolant-side and hot-gas-side heat transfer coefficients in the thrust chamber of a cryogenic engine. Based on this, the thermal analysis of a supercritical liquid hydrogen cooled engine is carried out. Results are presented for axial variation of heat transfer coefficients and temperature distributions for coolant and exposed wall. Tubular as well as milled channel configurations are considered for coolant flow.

Cascaded Cross Flow DBD-Adsorbent Technique for NOX Abatement in Diesel Engine Exhaust

In this paper, a different type of cross flow dielectric barrier discharge (DBD) reactor was designed and tested. Here the gas flow is perpendicular to the barrier discharge electrode. Discharge plasma was utilized to oxidize NO contained in the exhaust gas to NO2 and subsequent NO2 removal can be improved using an adsorbent system. A detailed study of DeNO(X) in a stationary diesel engine exhaust was carried out using pulsed electrical discharges/adsorbent processes. Activated alumina (Al2O3) and MS-13x were used as adsorbents at room temperature. The main emphasis is laid on the removal of NOX from the filtered diesel engine exhaust. In filtered exhaust environment, the cross flow reactor along with adsorbent exhibits a superior performance with regard to NOX removal when compared to that with axial flow of gas. In this paper we bring out a relative comparison of discharge plasma and plasma-adsorbent process at various gas flow rates, ranging from 2 l/min to 25 l/min. The discharge plasma-adsorbent assisted barrier discharge reactor has shown promising results in NOX removal at high flow rates.

Time-domain-finite-wave analysis of the engine exhaust system by means of the stationary-frame method of characteristics. Part I. Theory

Time-domain-finite-wave analysis of the engine exhaust system is usually done using the method of characteristics. This makes use of either the moving frame method, or the stationary frame method. The stationary frame method is more convenient than its counterpart inasmuch as it avoids the tedium of graphical computations. In this paper (part I), the stationary-frame computational scheme along with the boundary conditions has been implemented. The analysis of a uniform tube, cavity-pipe junction including the engine and the radiation ends, and also the simple area discontinuities has been presented. The analysis has been done accounting for wall friction and heat-transfer for a one-dimensional unsteady flow. In the process, a few inconsistencies in the formulations reported in the literature have been pointed out and corrected. In the accompanying paper (part II) results obtained from the simulation are shown to be in good agreement with the experimental observations.

Time-domain-finite-wave analysis of the engine exhaust system by means of the stationary-frame method of characteristics. Part II. Computed results and experimental corroboration thereof

Time-domain-finite-wave analysis of engine exhaust systems is usually carried out by means of the method of characteristics. The theory and the computational details of the stationary-frame method have been worked out in the accompanying paper (part I). In this paper (part II), typical computed results are given and discussed. A setup designed for experimental corroboration is described. The results obtained from the simulation are found to be in good agreement with experimental observations.

Study of Pulsed Plasma in a Crossed Flow Dielectric Barrier Discharge Reactor for Improvement of NOx Removal in Raw Diesel Engine Exhaust

Improved performance of plasma in raw engine exhaust treatment is reported. A new type of reactor referred to as of cross-flow dielectric barrier discharge (DBD) was used, in which the gas flow is perpendicular to the corona electrode. In raw exhaust environment, the cross-flow (radial-flow) reactor exhibits a superior performance with regard to NOX removal when compared to that with axial flow of gas. Experiments were conducted at different flow rates ranging from 2 L/min to 25 L/min. The plasma assisted barrier discharge reactor has shown encouraging results in NOx removal at high flow rates.

Studies on Compact Discharge Plasma Source for NOX Treatment in Engine Exhaust

This paper proposes a compact electric discharge plasma source for controlling NOX emission in diesel engine exhaust. An automobile ignition coil was used to generate the high voltage pulse using flyback topology. This design is aimed at retrofitting the existing catalytic converters with pulse assisted cleaning technique. In this paper we bring out a relative comparison of discharge plasma and plasma-adsorbent process at different gas flow rates. Activated alumina was used as adsorbent. The main emphasis is laid on the development of a compact pulse source from a DC supply for the removal of NOX from the filtered diesel engine exhaust.

Data rectification and detection of trend shifts in jet engine path measurements using median filters and fuzzy logic

Filtering methods are explored for removing noise from data while preserving sharp edges that many indicate a trend shift in gas turbine measurements. Linear filters are found to be have problems with removing noise while preserving features in the signal. The nonlinear hybrid median filter is found to accurately reproduce the root signal from noisy data. Simulated faulty data and fault-free gas path measurement data are passed through median filters and health residuals for the data set are created. The health residual is a scalar norm of the gas path measurement deltas and is used to partition the faulty engine from the healthy engine using fuzzy sets. The fuzzy detection system is developed and tested with noisy data and with filtered data. It is found from tests with simulated fault-free and faulty data that fuzzy trend shift detection based on filtered data is very accurate with no false alarms and negligible missed alarms.

Generalized model for infrared perception from an engine exhaust

A comprehensive scheme has been developed for the prediction of radiation from engine exhaust and its incidence on an arbitrarily located sensor. Existing codes have been modified for the simulation of flows inside nozzles and jets. A novel view factor computation scheme has been applied for the determination of the radiosities of the discrete panels of a diffuse and gray nozzle surface. The narrowband model has been used to model the radiation from the gas inside the nozzle and the nonhomogeneous jet. The gas radiation from the nozzle inclusive of nozzle surface radiosities have been used as boundary conditions on the jet radiation. Geometric modeling techniques have been developed to identify and isolate nozzle surface panels and gas columns of the nozzle and jet to determine the radiation signals incident on the sensor. The scheme has been validated for intensity and heat flux predictions, and some useful results of practical importance have been generated to establish its viability for infrared signature analysis of jets.

Noise and outlier removal from jet engine health signals using weighted FIR median hybrid filters

The removal of noise and outliers from measurement signals is a major problem in jet engine health monitoring. Topical measurement signals found in most jet engines include low rotor speed, high rotor speed. fuel flow and exhaust gas temperature. Deviations in these measurements from a baseline 'good' engine are often called measurement deltas and the health signals used for fault detection, isolation, trending and data mining. Linear filters such as the FIR moving average filter and IIR exponential average filter are used in the industry to remove noise and outliers from the jet engine measurement deltas. However, the use of linear filters can lead to loss of critical features in the signal that can contain information about maintenance and repair events that could be used by fault isolation algorithms to determine engine condition or by data mining algorithms to learn valuable patterns in the data, Non-linear filters such as the median and weighted median hybrid filters offer the opportunity to remove noise and gross outliers from signals while preserving features. In this study. a comparison of traditional linear filters popular in the jet engine industry is made with the median filter and the subfilter weighted FIR median hybrid (SWFMH) filter. Results using simulated data with implanted faults shows that the SWFMH filter results in a noise reduction of over 60 per cent compared to only 20 per cent for FIR filters and 30 per cent for IIR filters. Preprocessing jet engine health signals using the SWFMH filter would greatly improve the accuracy of diagnostic systems. (C) 2002 Published by Elsevier Science Ltd.

A cascaded discharge plasma-adsorbent technique for engine exhaust treatment

A cascaded system of electrical discharges (non-thermal plasma) and adsorption process was investigated for the removal of oxides of Nitrogen (NOx) and total hydrocarbons (THC) from an actual diesel engine exhaust. The non-thermal plasma and adsorption processes were separately studied first and then the cascaded process was studied. In this study, different types of adsorbents were used. The NOx removal efficiency was higher with plasma-associated adsorption (cascaded) process compared to the individual processes and the removal efficiency was found almost invariant in time. When associated by plasma, among the adsorbents studied, activated charcoal and MS-13X were more effective for NOx and THC removal respectively. The experiments were conducted at no load and at 50% load conditions. The plasma reactor was kept at room temperature throughout the experiment, while the temperature of the adsorbent reactor was varied. A relative comparison of adsorbents was discussed at the end.

Performance evaluation of nonthermal plasma reactors for NO oxidation in diesel engine exhaust gas treatment

The discharge plasma-chemical hybrid process for NOinfinity removal from the flue gas emissions is an extremely effective and economical approach in comparison with the conventional selective catalytic reduction system. In this paper we bring out a relative comparison of several discharge plasma reactors from the point of NO removal efficiency. The reactors were either energized by ac or by repetitive pulses. Ferroelectric pellets were used to study the effect of pellet assisted discharges on gas cleaning. Diesel engine exhaust, at different loads; is used to approximately simulate the flue gas composition. Investigations were carried out at room temperature with respect to the variation of reaction products against the discharge power. Main emphasis is laid on the oxidation of NO to NO2, without reducing NOx concentration (i.e., minimum reaction byproducts), with least power consumption. The produced NO2 will be totally converted to N-2 and Na-2 SO4 using Na-2 SO3. The ac packed-bed reactor and pelletless pulsed corona reactor showed better performance, with minimum reaction products for a given power, when the NO concentration was low (similar to 100 ppm). When the engine load exceeds 50% (NO > 300 ppm) there was not much decrease in NO reduction and more or less all the reactors performed equally. The total operating cost of the plasma-chemical hybrid system becomes $4010/ton of NO, which is 1/3-1/5 of the conventional selective catalytic process.