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The energy assessment must be made through the energy quantity as well as the quality. But the usual energy analysis evaluates the energy generally on its quantity only. However, the exergy analysis assesses the energy on quantity as well as the quality. The aim of the exergy analysis is to identify the magnitudes and the locations of real energy losses, in order to improve the existing systems, processes or components. The present paper deals with an exergy analysis performed on an operating 50MWe unit of lignite fired steam power plant at Thermal Power Station-I, Neyveli Lignite Corporation Limited, Neyveli, Tamil Nadu, India. The exergy losses occurred in the various subsystems of the plant and their components have been calculated using the mass, energy and exergy balance equations. The distribution of the exergy losses in several plant components during the real time plant running conditions has been assessed to locate the process irreversibility. The First law efficiency (energy efficiency) and the Second law efficiency (exergy efficiency) of the plant have also been calculated. The comparison between the energy losses and the exergy losses of the individual components of the plant shows that the maximum energy losses of 39% occur in the condenser, whereas the maximum exergy losses of 42.73% occur in the combustor. The real losses of energy which has a scope for the improvement are given as maximum exergy losses that occurred in the combustor.

In order to optimize the performance of a small direct injection (DI) diesel engine with respect to noise, emissions, and fuel economy, an experimental investigation was undertaken using Taguchi methods. A single-cylinder 3.5 kW diesel engine was selected for performance tests at different levels of two operating parameters (speed and load) and six injection parameters of the engine (static injection timing, plunger diameter, nozzle valve opening pressure, nozzle hole diameter, number of nozzle holes, and nozzle tip protrusion). These controlled parameters were varied at two levels, and the resulting changes in responses were investigated, namely engine noise, combustion noise, smoke, brake specific fuel consumption (b.s.f.c.), and emissions of unburned hydrocarbons (HC), oxides of nitrogen (NO x), and carbon monoxide (CO) were investigated. The optimum values of engine noise, combustion noise, smoke, emissions, and b.s.f.c. could be predicted using signal-noise ( S/N) ratios, and a relevant combination of controlled input parameters was specified. Results of confirmation runs of the engine showed good agreement with the predicted quantities of interest based on Taguchi analysis. The relative importance of the controlled parameters to the above responses was evaluated in terms of the percentage contributions of the parameters using analysis of variance (ANOVA). The Taguchi method of experimental design was found to be robust and more cost effective for understanding the relationship between diesel engine parameters and noise, emissions, and b.s.f.c. than full factorial design.

The conflicting effects of the operating parameters and the injection parameter (injection timing) on engine performance and environmental pollution factors is studied in this paper. As an optimization objective, a 3.5 kW small direct injection diesel engine was used as the test engine, and its speed, load, and static injection timing were varied as per 4×4×3 full factorial design array. Radiated engine noise, smoke level, brake specific fuel consumption, and emissions of unburned hydrocarbons and nitrogen oxides were captured for all test runs. Objective functions relating input and output parameters were obtained using response surface methodology (RSM). Parameter optimization was carried out to control output responses under their mean limit using multi-objective goal programming and minimax programming optimization techniques.