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This paper reports on an experimental study conducted to determine the effect on the knock limited operating map of a natural gas engine when propane is added to the fuel. The map involves engine parameters such as BMEP, spark timing, equivalence ratio, and propane fraction. The map shows that to maintain its design BMEP, the maximum and minimum equivalence ratios that the engine can operate with natural gas are 0.78 at a timing of 25 degrees BTDC and 0.73 at 20 degrees BTDC, respectively. However, when the propane percentage of the fuel is increased to 15% of the fuel by mass, the maximum and minimum equivalence ratios that the engine can operate are 0.75 and 0.70, respectively, which corresponds to spark timings of 22 and 20 degrees BTDC. The map demonstrates that knock is not a major constraint for typical natural gas. Spark timing retard is limited by the exhaust gas temperature and minimum equivalence ratio is limited by the BMEP requirement of the engine.

Knock-induced pressure waves in the combustion chambers of spark-ignited engines cause the engine block to vibrate at the same frequencies. These vibrations have different amplitudes at different locations on the engine block. This paper describes a project to find a location on the engine block where the amplitudes of the knock-induced vibrations are high enough to use in a knock control system. To find this location, six piezoelectric knock sensors were located on suitable regions of the engine block. Data were collected from the sensors at both knocking and non-knocking conditions using a high speed data acquisition system. After the data were transformed into the frequency domain, comparison of the knocking and non-knocking condition data indicated the frequencies and amplitudes of the knock-induced engine block vibrations. The location where knock-induced vibrations were transferred with the greatest amplitude was determined.

This work presents the analytic and experimental results relating engine performance and operating schedule with fuel cost and tail-pipe emissions for the series hybrid electric vehicle (HEV) design. Results are based on vehicle data from the electric G-van produced by Conceptor Industries. A computer simulation developed using basic principles predicts the battery demand over a specified vehicle operation profile. Engine tests on the effects of engine power level and number of starts show that while fuel consumption did not vary, carbon monoxide (CO) emissions did show an increase. The engine used was a 2-cylinder, spark ignited, 4-stroke, carbureted engine and did not utilize exhaust after-treatment. The results of the engine tests and simulation data are combined to predict the CO emissions and fuel cost for the series HEV design. The estimated CO output was 18.7 g/km, and the fuel cost was estimated between 4.3 and 4.5 cents/km.

Biodiesel, a fuel produced by transesterification of vegetable oils or animal fats, is receiving increasing attention as an alternative fuel for diesel engines. The properties of biodiesel can vary depending on its chemical composition. Biodiesel produced from vegetable oils is higher in esters of unsaturated fatty acids and biodiesel from animal fats is higher in esters of saturated fatty acids. This paper attempts to identify the mechanism for biodiesel's emissions reduction effect and discusses the effects of blending various pure esters with No. 2 diesel fuel on engine performance and emissions. This project concludes that biodiesel's particulate reducing effect can be attributed to two factors: its displacement of aromatic and shorter chain paraffin hydrocarbons and its oxygen content. The pure ester tests showed that while all esters demonstrated reductions in hydrocarbon and particulate emissions, methyl palmitate was the most effective ester in achieving these reductions.

A miniature sensor for detecting cylinder misfiring based on the principle of magnetostriction has been developed for on-board use in production vehicles. The sensor induces a magnetic field in the engine crankshaft, and via Faraday's law, obtains a signal directly related to the strength of the field. Due to magnetostriction, the field strength changes as the stress in the crankshaft changes during each cylinder firing. The output signal of the sensor is therefore high when any given cylinder fires and low when it misfires, permitting ready determination of misfiring. Tests on a manual transmission vehicle have shown that a single sensor can detect misfiring in one or more cylinders at any non-negative torque and any speed, as well as on very rough roads. Other uses for the sensor, such as knock detection, are anticipated.

A phenomenological, multizone, transient spray model has been developed to simulate the performance and nitric oxide emission characteristics of a turbocharged diesel engine fumigated with alcohol. The effects of speed, load, alcohol proof, and the fraction of the engine's power supplied by the alcohol have been investigated. The multizone model is designed to account for the heterogeneous composition of the cylinder contents by dividing the cylinder into a number of locally homogeneous zones. The model includes the interactions between the fuel spray and swirling air in the cylinder and the effect of wall impingement on fuel-air mixing and combustion. A complete thermodynamic analysis has been applied to the individual zones to obtain cylinder pressure data.