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In the present work, a tuned gas dynamics based blow by model was used for prediction of thermodynamic state variables till start of combustion in a high speed diesel engine. The burn rate fraction was determined from experimental pressure trace using Rassweiller-Withrow method. Furthermore, suitable single and double Wiebe parameters, consistent with the experimental combustion behavior were determined statistically. The comparison with experimental heat release and burn rate fraction confirmed the unsuitability of single Wiebe function for diesel combustion. A stochastic zero-dimensional thermodynamic model was used to predict pressure traces for various load/fueling conditions. The results exhibited a sub-15% error margin between predicted and experimental pressure traces across all crank angles and fuelling rates. Finally, the model constants are proposed as a function of non-dimensional fuelling rate.

A single cylinder direct injection (DI) diesel engine is modified to run in HCCI-DI mode using a novel in-cylinder dual injection strategy. In this present investigation effect of 2nd injection timing, premixed equivalence ratio and exhaust gas recirculation (EGR) on combustion and emission behavior is studied. Based on the characteristics of combustion, performance and emission behavior, 2nd injection timing is optimized at a constant split ratio (80%) and engine speed (1500 rev/min). Premixed equivalence ratio was varied (up to 0.38) at the optimized 2nd injection timing condition. It is identified that 2nd injection timing and premixed equivalence ratio play an important role in controlling the occurrences of all combustion parameters of HCCI-DI combustion. EGR was introduced in the cylinder to understand its effect on various combustion parameters and emission behavior.

Homogeneous Charge Compression Ignition (HCCI) combustion was studied as a means of reducing PM and NOx emission simultaneously while maintaining high thermal efficiency and lower fuel consumption. An innovative low cost dual injection strategy is developed to investigate HCCI-DI combustion. This study is focused on the effect of fuel properties and cetane number on HCCI-DI combustion to understand the combustion and emission behavior of a direct injection HCCI engine using double injection strategy with blends of n-heptane and isooctane as fuel. A comparison is also made to understand the behavior and benefits of HCCI-DI combustion over the conventional combustion system. All experiments were carried out at a constant speed of 1350 rev/min and at zero, 15% and 30% of the full load conditions to avoid high knock intensity for high cetane fuel which occurs beyond this operating load condition.

An innovative method is developed for achieving HCCI-DI combustion without any major engine geometry modification. Many control strategies have been reported in literature, in spite of that even today no HCCI combustion engine is available on commercial basis. Pilot and main fuel injection strategy is used as a control strategy in this work. Our developed technique is a low cost alternative to conventional CRDI pumps which can be implemented readily at least for rural application engines (where cost of the system is more important than any other aspects) to reduce emissions. Using this new technique a stable HCCI-DI combustion was achieved for a wide operating range. To realize the effectiveness of this developed experimentation technique, a detailed combustion study at various operating conditions were investigated using commercial diesel as fuel.

In the present experimental investigations the influence of injector opening pressures and injection timings on the engine performance and exhaust emissions of a naturally aspirated single cylinder diesel engine has been investigated. The test were conducted with four different fuels, namely diesel and Tung biodiesel blends (TB10, TB15, TB20 and TB50) at three different injector opening pressures (150 bar, 200 bar and 250 bar) respectively. Fuel injection opening pressures were varied by changing the spring tension of the needle valve of injector nozzle. The three different injection timings (Standard timing at 23° BTDC, Retarded Timing of 21° BTDC and Advanced Timing of 25° BTDC) were used. The injection timings were varied by changing the thickness of the shim. The entire tests were conducted at the constant engine speed of 1500 rpm under various load conditions.