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Strict new governmental regulations regarding emissions force engine manufacturers to develop and implement new technologies for all types of diesel engines. In the present study, the exhaust emissions of a turbocharged, intercooled direct-injection off-road diesel engine were reduced by retarding the injection timing and by using exhaust gas recirculation (EGR). The effects of the retarded timing and EGR on the general engine performance, regulated exhaust emissions and exhaust particle number and size distribution were examined. The results showed that at some loads, the retarded injection increased the number of ultrafine particles, but the number of large particles decreased. At some loads, the injection retardation resulted, however, in increased particle numbers within the whole particle size range. The increase in the EGR rate increased the particle number steadily throughout the entire particle size range.

The effect of turbocharger design on engine performance and exhaust emissions was studied. The test engine was a direct injection turbocharged, intercooled off-road diesel engine. Special attention was paid to the exhaust particulate matter (PM) emissions of the engine. The engine was first equipped with a standard (Std), uncontrolled turbocharger (TC) which was then replaced by a waste-gate (WG) turbocharger. The engine was fueled with commercial diesel fuel oil. The engine was operated at three speeds within the entire load range. Basic performance, gaseous exhaust emissions and exhaust particle quantities were recorded. The results showed that the WG TC is advantageous at high loads at low and medium speeds, where reductions of PM emissions and smoke were observed when running the engine with this TC. At rated speed, however, the Std TC proved slightly better than the WG one. Regarding gaseous exhaust emissions, there was no noteworthy difference between the tested turbochargers.

Exhaust emissions of particulate matter (PM) of a direct injection turbocharged, intercooled tractor diesel engine were determined, while fueling the engine with a vegetable oil pressed from mustard seeds. The un-esterized mustard seed oil (MSO) was cleaned by simply letting it stand and clear. Appropriate injector tips were first selected. Thereafter, performance and exhaust emissions were measured in the large load-speed envelope. The results were compared to those obtained while running the engine with diesel fuel oil (DFO). The results showed that the engine emits more fine and ultra-fine particles when running with MSO than with DFO, although the exhaust smoke and total hydrocarbon emissions were lower and the brake thermal efficiency was very similar. In the range of larger particles, PM emissions were lower with MSO at high loads and lower with DFO at low loads. Preheating of MSO reduced the PM emissions, but not to a level observed with DFO in the range of nanoparticles.

A comparative injector test was performed with a direct injection turbocharged, intercooled tractor diesel engine, fueled with a vegetable oil pressed from mustard seeds. The un-esterized mustard seed oil (MSO) was cleaned by simply letting it stand and clear. Engine operation, performance and exhaust emissions were investigated using two-spring injectors as the injection valves. Two injector tips with different orifice diameters were tested. Injection timing was first optimized. Thereafter, performance and exhaust emissions were measured in the large load-speed envelope. The results showed that some benefits were obtained with two-stage injection, particularly at idle, but also at low loads at intermediate speed. The wet exhaust content of oxides of nitrogen decreased at idle, while the CO content and some species of HCs remained almost constant. The NOx emissions also decreased at low loads at intermediate speed.

A durability test was performed with a direct injection turbocharged, intercooled tractor diesel engine, fueled with a vegetable oil pressed from mustard seeds. The unesterized mustard seed oil (MSO) was cleaned by simply letting it stand and clear. A charge air cooler was installed in the engine. Basic performance and exhaust emissions were first determined by operating the engine on diesel fuel oil (DFO). Thereafter, the same measurements were made with MSO as fuel. At the third stage, the engine was operated for 150 hours according to a standard loading cycle using MSO as fuel. After this running period, performance and exhaust emissions were again measured. The results showed that the rated power had decreased somewhat during the period. The maximum torque and brake thermal efficiencies, however, were very similar to that observed before the test. The CO emissions were higher at some low loads, but the exhaust smoke had been reduced.

The performance and exhaust emissions of a direct injection turbocharged tractor diesel engine were optimized by running the engine on a vegetable oil pressed from mustard seeds. The unesterized mustard seed oil (MSO) was cleaned just letting it stand and clear. Injection timing of the engine was varied to identify optimum timing. No other modifications were made to the engine. An injection advance of 17° proved to be the optimum when running on MSO, as the engine generated a brake torque with MSO almost equal to that achieved with a diesel engine. The brake thermal efficiencies (BTE) were rather similar, and use of the retarded timing further reduced NOx emissions. Exhaust HC emissions were determined using FT-IR technology. Generally, the contents of measured HC species were higher with diesel fuel than with MSO. Most of the field observations from four harvesting seasons proved encouraging.

The performance and exhaust emissions of a direct injection tractor diesel engine were investigated running the engine on vegetable oils pressed from mustard seeds. Two different mustard seed oils (MSOs) were tested. The unesterized MSOs were cleaned by letting them stand and clear. No modifications were made to the turbocharged diesel engine. The engine generated brake torque with MSOs almost equal to that with diesel fuel oil (DFO). Rather similar brake thermal efficiencies were measured with MSOs than with DFO. Use of MSOs reduced the exhaust smoke and NOx emissions. Exhaust HC emissions were determined using FT-IR technology. No great differences between the fuels were observed in the HC emissions.