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This paper describes the development and proof-of-concept testing of an electrically based (i.e., non-optical) smoke sensor for diesel engines. The sensor is intended to provide a means of detecting smoke levels that exceed certain pre-defined limits. Potential applications for the sensor include closed loop control of Exhaust Gas Recirculation (EGR) and the diagnosis of fuel injection faults. Engine dynamometer tests were carried out using a heavy duty diesel engine equipped with a laboratory EGR system. EGR levels were adjusted to vary exhaust smoke levels at a fixed speed/load test point. Reference smoke measurements were provided by an AVL 415S variable sampling smoke meter. The experimental results showed a correlation between the sensor signal and the Filter Smoke Number (FSN) at FSN values between approximately 1 and 3. The sensor was able to detect relative changes in smoke levels, but its absolute sensitivity was not consistent.

This paper describes an experimental study of the effects of ignition spark characteristics on combustion behaviour in a light duty automotive engine. A prototype programmable energy ignition system was used to investigate the influence of both spark energy and the current/time profile used to deliver a given amount of energy. The engine was tested under part load conditions using a stoichiometric air/fuel ratio and relatively high levels of exhaust gas recirculation (EGR). In addition to tests with port-injected gasoline, tests were also carried out using propane (premixed upstream of the throttle) in order to investigate the possibility that improvements in the homogeneity of the mixture might influence the impact of varying the spark characteristics.

This paper describes the vehicle implementation and cold start calibration of a neat methanol (M100) fuelled port injected engine equipped with plasma jet ignition and prompt exhaust gas recirculation. Test results are presented in which the influence of various factors on fuel enrichment requirements were studied with the aim of identifying strategies to reduce enrichment and lower start-up emissions. Vehicle cold starting has been demonstrated down to -30°C and studied in detail circa -20°C. Reductions in start-up CO emissions at -7°C have been achieved by means of early closed loop fuel control. Experimental results are also presented which indicate that the potential exists to reduce start-up hydrocarbon emissions at 25°C when appropriate calibration strategies are employed.

This paper describes an experimental study in which the potential for fuel economy improvements with EGR was investigated using an automotive V6 engine. Steady state engine dynamometer tests were run at 2000 rpm and 200 kPa Brake Mean Effective Pressure (BMEP). The engine was fuelled with gasoline, methanol or natural gas. Plasma jet ignition was evaluated as a means of improving EGR tolerance. EGR tolerance with methanol was found to be better than with gasoline, while natural gas showed the poorest EGR tolerance. Plasma jet ignition extended EGR limits for all three fuels. Fuel economy benefits were realized with natural gas and gasoline at low EGR rates and without EGR but plasma jet ignition provided no improvements with methanol until over 10% EGR was used. Plasma jet ignition made stable operation possible with methanol at 40% EGR, where fuel economy improvements were ultimately limited by the slow burning associated with the high EGR rate.

Warm-up fuel consumption behaviour as affected by ambient temperature was evaluated for five OEM gasoline fuelled automobiles. Multiple EPA FTP 75 tests were performed with each vehicle at ambient test cell soak temperatures of 25°C and -7°C. Fuel consumption measured during the warm-up (Bag 1, Cold Transient) test segments at these two temperature conditions was compared to the fully warmed Hot Transient (Bag 3) fuel consumption from the 25°C ambient temperature tests (the Bag 1 and Bag 3 segments involve identical speed curves). Fuel consumption increases over the 25°C Bag 3 tests for the two warm-up test conditions were differentiated as those caused by increased drivetrain losses and those caused by intake charge enrichment. Results show wide variations in warm-up behaviour among the five vehicles with respect to the relative increases in fuel consumption, and the proportion of the fuel consumption increases attributable to drivetrain losses and enrichment.

The temperature and pressure of the charge, reached at the end of the compression stroke when an engine is cranked for starting, decide whether it will start and attain selfsustained running. These, in turn, are affected by the crevice volume in, and the blowby from, the engine, particularly at cold ambient temperatures and low cranking speeds. This paper presents a model to estimate these effects. Tentative values are proposed for the parameters that appear in the model based on experiments performed on small engines motored in a cold chamber. The model can be incorporated in engine cycle simulation programs to allow for crevice and blowby effects. It is impossible to prevent gas leakage entirely from an operating reciprocating engine. Gas may leak at the valves, the cylinder head gasket, the spark plug gasket, the injector gasket and the piston rings. The gas that leaks from the cylinder past the piston rings into the crankcase is termed “blowby”.

This study describes the design and proof-of-concept testing of a system which has enabled sub-zero cold starting of a port-injected V6 engine fuelled with M100. At -30°C, the engine could reach running speed about 5s after the beginning of cranking. At a given temperature, starts were achieved using a fraction of the mixture enrichment normally required for the more volatile M85 fuels. During cold start cranking, firing is achieved using a high energy plasma jet ignition system. The achievement of stable idling following first fire is made possible through the use of an Exhaust Charged Cycle (ECC) camshaft design. The ECC camshaft promptly recirculates hot exhaust products, unburnt methanol and partial combustion products back into the cylinder to enhance combustion. The combined plasma jet/ECC system demonstrated exceptionally good combustion stability during fast idle following sub-zero cold starts.

A slightly modified thermodynamic cycle for a spark ignition engine is proposed as a means of improving cold starting, warm-up driveability and fuel economy. Tests were conducted on a single cylinder research engine using a modified camshaft to implement the cycle. Substantial improvements in BSFC were obtained not only during the warm-up period but also at normal steady-state temperatures. NOx, CO and UBHC were simultaneously reduced as well.

Methanol fuelled spark ignition engines have poor low- temperature starting capabilities. Since the problem is one of fundamental volatility, blending volatile additives with methanol can improve cold starting. In this study, minimum starting temperatures were determined for neat methanol, a 90% methanol fuel blend and seven 85% methanol fuel blends. The carburetted engine was from a 1.6 litre Escort produced for operation on methanol-based fuels. Starting was possible below −35° C with some of the M85 fuels. Instances of stalling during the engine acceleration from cranking to idle speed were found to be due to lean excursions in the fuel/air ratios delivered to the cylinders. M85 fuels primed with n-butane required the least cranking time before starting.

Geometric maldistribution is recognized as a major impediment to obtaining maximum efficiency from carbureted or single point injected methanol fuelled engines. In this program engine tests have been conducted with the inlet manifold inclined to provide a gravitational influence on the flow of fuel in order to study maldistribution effects due to manifold fuel films. It was found that substantial distribution errors were caused by this slight gravitational influence, which was only a fraction of that which could occur periodically in a maneuvering passenger car. Improved atomization is shown to be superior to heating the inlet air for reducing maldistribution, although the latter vaporized fuel more completely before the inlet ports. Fuel films may evaporate more easily than airborne droplets in the size range produced by many carburetors.

Engine cold starting tests have been conducted in a laboratory cold chamber to compare the performance of three 10% methanol/90% gasoline blends with that of Indolene. The blends had different Reid Vapour Pressures and tests were conducted over a wide range of fuel/air ratios at temperatures as low as −45°C. It was found that all M10 blends tested had poorer starting performance than Indolene at cold temperatures, including those of nominally higher volatility. Cold starting did not correlate to Reid Vapour Pressure even when comparing two oxygenated fuels. Graphs are presented showing minimum cold starting temperature as a function of fuel-air equivalence ratio.

The present cold starting performance of methanol fuelled spark ignition engines is poor compared to their gasoline counterparts. Apparatus has been developed to cold soak a small engine to temperatures as low as −65°C. Tests have been conducted using methanol, Indolene and sample of commercial gasoline of depressed volatility. Data are provided showing the effect of fuel-air ratio on minimum starting temperature for the three fuels. Methanol failed to start at temperatures below about 0°C whereas the Indolene started easily to below −45°C. Reid Vapour Pressure is shown to be ineffective as a predictor of cold starting performance for methanol.