Search Results

The recent oil crisis has once again emphasized the need to develop both fuel efficient engines and alternately fueled engines, particularly for automotive applications. Engines which burn coal or coal pyrolysis products are attractive, but ignition delay and metal erosion problems continue to limit high speed operation of such engines. Further, the throttled spark ignition engine often used with methanol and natural gas does not prove an efficient or tolerant device for the combustion of a wide range of fuel. Therefore, an novel approach must be taken in order to achieve the efficient and flexible operation of such an engine. A novel design of a fuel tolerant engine suitable for burning coal fuels separates the combustion from the piston in order to have more careful flame control and to exclude the particulate matter from the engine's piston rings.

The Rand Cam engine is a novel design which avoids the use of pistons in favor of a cavity of varying size and shape. A set of vanes protrudes from a rotor into a circular trough in a stator. The vanes seal to the walls and base of the trough, which is of varying depth, and progress around the trough with rotation of the rotor. These vanes therefore pass through the rotor and are constrained to move parallel to the rotational axis. Intake and exhaust processes occur through ports in the stator wall which are revealed by the passing vanes. Advantages of the basic design include an absence of valves, reduction in reciprocating masses, presence of an integral flywheel in the rotor and strong fluid movement akin a swirl induced by the relative velocity between the rotor and stator.

A set of experiments were conducted to evaluate the performance differences between a Low Heat Rejection Engine (LHRE) which is ceramic-insulated and a conventional baseline metal diesel engine which is water-cooled. Both engines were single cylinder, direct injection, and turbocharged. The objective of the study was to investigate the rate of heat release of these engines so that performance improvement procedures could be obtained. In this paper, the difference of the ignition delay between the two engines was determined. Two methods for improving the combustion process of the LHRE were studied: use of mixture fuels and increase the fuel injection rate. Both methods proved effective and reduced the fuel consumption rate of the LHRE.

A bi-fuel engine with the ability to run optimally on both compressed natural gas (CNG) and gasoline is being developed. Such bi-fuel automotive engines are necessary to bridge the gap between gasoline and natural gas as an alternative fuel while natural gas fueling stations are not yet common enough to make a dedicated natural gas vehicle practical. As an example of modern progressive engine design, a Saturn 1.9 liter 4-cylinder dual overhead cam (DOHC) engine has been selected as a base powerplant for this development. Many previous natural gas conversions have made compromises in engine control strategies, including mapped open-loop methods, or resorting to translating the signals to or from the original controller. The engine control system described here, however, employs adaptive closed-loop control, optimizing fuel delivery and spark timing for both fuels.

Data has been gathered using the West Virginia University Heavy Duty Transportable Emissions Laboratories from buses operating on diesel and a variety of alternate fuels in the field. Typically, the transportable chassis dynamo meter is set up at a local transit agency and the selected buses are tested using the fuel in the vehicle at the time of the test. The dynamometer may be set up to operate indoors or outdoors depending on the space available at the site. Samples of the fuels being used at the site are collected and sent to the laboratory for analysis and this information is then sent together with emissions data to the Alternate Fuels Data Center at the National Renewable Energy Laboratory. Emissions data are acquired from buses using the Central Business District cycle reported in SAE Standard J1376; this cycle has 14 ramps with 20 mph (32.2 km/h) peaks, separated by idle periods.

With the implementation of a closed loop fuel control system, operation of lean-burn natural gas engines can be optimized in terms of reducing emissions while maximizing efficiency. Such a system would compensate for variations in fuel composition, but also would correct for variations in volumetric efficiency due to immediate engine history and long-term engine component wear. Present day engine controllers perform well when they are operated with the same gas composition for which they were calibrated, but because fuel composition varies geographically as well as seasonally, some method of compensation is required. A closed loop control system on a medium-duty lean-burn engine will enhance performance by maintaining the desired air-fuel ratio to eliminate any unwanted rich or lean excursions (relative to the desired air-fuel ratio) that produce excess engine-out emissions. Such a system can also guard against internal engine damage due to overheating and/or engine knock.

A novel engine concept, currently under study, addresses many of the problems commonly associated with conventional internal combustion engines. In its simplest form the novel engine consists of a single crankshaft operating both a piston compressor and a piston expander which are connected by a continuous flame combustion chamber. One might regard this as a Brayton piston engine which is similar to a previous engine investigated by Warren. Also, due to the use of piston cylinders as the compression and expansion devices, this engine varies little mechanically from current engine technology thus allowing for easy implementation. The main improvement from conventional engine design is that the expansion cylinder can have a larger displacement than that of the compression cylinder. This allows more power to be extracted by lowering the loss due to blowdown and this will increase the thermal efficiency.

The Stiller-Smith mechanism is a new mechanism for the translation of linear motion into rotary motion, and has been considered as an alternative to the conventional slider-crank mechanism in the design of internal combustion engines and piston compressors. Piston motion differs between the two mechanisms, being perfectly sinusoidal for the Stiller-Smith case. Plots of dimensionless volume and volume rate-change are presented for one engine cycle. It is argued that the different motion is important when considering rate-based processes such as heat transfer to a cylinder wall and chemical kinetics during combustion. This paper also addresses the fact that a Stiller-Smith engine will be easier to configure for adiabatic operation, with many attendant benefits.

The emissions reduction benefits of Fischer-Tropsch (FT) diesel fuel have been shown in several recent published studies in both engine testing and in-use vehicle testing. FT diesel fuel shows significant advantages in reducing regulated engine emissions over conventional diesel fuel primarily to: its zero sulfur specification, implying reduced particulate matter (PM) emissions, its relatively lower aromaticity, and its relatively high cetane rating. However, the actual effect of FT diesel formulation on the in-cylinder combustion characteristics of unmodified modern heavy-duty diesel engines is not well documented. As a result, a Navistar T444E (V8, 7.3 liter) engine, instrumented for in-cylinder pressure measurement, was installed on an engine dynamometer and subjected to steady-state emissions measurement using both conventional Federal low sulfur pump diesel and a natural gas-derived FT fuel.