Desirability Analysis Of Brake Thermal Efficiency And Unburnt Hydrocarbons

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5.3 Optimum parameters obtained by Desirability analysis
Figure 5.17, shows the optimality graph obtained by MINITAB 17 software for Brake specific fuel consumption, Brake thermal efficiency and Unburnt hydrocarbons of COME blends. The most favoured optimal condition obtained for Brake specific fuel consumption, Brake thermal efficiency and Unburnt hydrocarbons are shown.
Optimization is carried out by using Derringer’s Desirability approach of RSM. Equations to calculate desirability are shown below. The corresponding factor combination for the optimum solution is considered to be the best parameters for engine operation.

Desirability approach
RSM based desirability function approach is simple, efficient and most widely used technique for
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Weights are used to give more emphasis to the lower/ upper bounds. Weights can be ranged from 0.1 to 10; a weight greater than 1 gives more emphasis to the goal, weights less than 1 give less emphasis. In the overall desirability objective function (D), each response can be assigned an importance (r), relative to the other responses [22].

Figure 5.17 Optimal plot of performance and emission of COME blends.

Optimization criteria for the responses (bsfc, BThe, HC and CO) are shown in Table
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[2] The second order polynomial mathematical models are developed for of Brake specific fuel consumption, Brake thermal efficiency, HC and CO emissions to establish the functional relationship between the input variables and responses.
[3] Analysis of Variance is performed for the significance of each parameter on responses. [4] BThe, bsfc and CO emissions are mostly affected by load followed by CR and Blend. [5] HC emission is mostly affected by Biodiesel blend followed by Load and CR.
[6] Optimization of parameters is done using desirability approach.The optimum operating conditions of the engine are found to be at 9.03 kg of load, 18 compression ratio and blend of 15.30 % to get optimum performance of the engine with a composite desirability of 0.96. BThe, bsfc, HC and CO at optimized parameters is found to be 30.87 %, 0.2695 kg/kW h, 16.94 ppm and 0.06% respectively.
[7] Confirmation tests are carried out to find the error between the predicted and experimental results. The results reveal that the developed models are in good agreement with experimental

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