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The paper describes experimental validation of a laboratory flow apparatus used to measure the ignition delay times of diesel fuels at atmospheric pressure in near quiescent air. To validate the proposed method the experimental data were compared with the results from the studies performend on non-engine combustion chambers with continuous air flow at atmospheric pressure and various temperatures. The proposed flow apparatus, described in an earlier paper, has the means to provide air temperatures in the range between 650 and 730°C. An infrared radiation detector monitors the evolution of the temperature inside the combustion chamber. Ignition delay is measured as the time interval between the beginning of the needle lift and the beginning of increase in infrared radiation detected by the sensor. Six test fuels were used.

The paper describes the design and operation of a laboratory combustion chamber used to measure the ignition delay times of diesel engine fuels at atmospheric pressure in near quiescent air. The flow apparatus has the means to provide air temperatures in the range between 650 and 730°K which is the typical temperature range at the end of the compression stroke in a diesel engine. An injection pump with a trigger mechanism delivers equal amounts of fuel to an injector, which sprays it into the constantly replensihed supply of fresh, hot air for combustion. An infrared radiation detector monitors the evolution of the temperature inside the combustion chamber. Ignition delay is measured as the time interval between the beginning of the needle lift and the beginning of increase in infrared radiation detected by the sensor. Test results for two fuels are presented and compared with the results from previous studies performed under similar test conditions.

The paper* describes the design and operation of a laboratory combustion chamber used to study the energy released during the premixed burning phase of diesel combustion. The flow apparatus operates at atmospheric pressure and has the means to provide near quiescent air at temperatures in the range between 800 and 950° K which is the typical temperature range at the end of compression stroke in a diesel engine. A rotary injection pump with a trigger mechanism delivers equal amounts of fuel to an injector, which sprays it into the constantly replenished supply of fresh, hot air for combustion. An infrared radiation detector and a photodiode sensitive to radiation in the visible range of the electromagnetic spectrum monitor the events taking place inside the combustion chamber through a sapphire lens. A beam splitter permits simultaneous observation of the combustion events by both sensors.

The paper describes engine modifications, which are proposed to provide a means to overcome the adverse effect of sunflower oil fuel on diesel engines' longevity. The proposed system consists of a dual fuel system and fuel preheater. The dual fuel system was designed to eliminate engine conditions that are responsible for the majority of the problems associated with the use of sunflower oil fuel. Specifically, the dual fuel system will (1) prevent the operation of an engine on alternative fuels at low-load, low-speed conditions, (2) reduce the exposure time of the fuel injection system to the sunflower oil at the excessively high temperature conditions during the transition process from high to light loads, (3) eliminate the conditions (such as cold start-up) at which the fuel temperature is too low for acceptable atomization, and (4) eliminate the exposure of the fuel injection system to sunflower oil during the shut-down period.

A 25-75 blend (v/v) of alkali-refined sunflower oil and diesel fuel, a 25-75 blend (v/v) of high oleic safflower oil and diesel fuel, a non-ionic sunflower oil-aqueous ethanol micro-emulsion, and a methyl ester of sunflower oil were evaluated as fuels in a direct injected, turbocharged, intercooled, 4-cylinder Allis-Chalmers diesel engine during a 200-hour ERA cycle laboratory screening endurance test. Engine performance on Phillips 2-D reference fuel served as baseline for the experimental fuels. This paper deals with several aspects of the anomalous behavior of the fuel injection system and its effects on long-term engine performance as experienced during the operation with the alternate fuels. Particular attention was paid to the changes in injection timing and the rates of injection pressure. Furthermore, secondary injection phenomena, initial and final stages of the fuel injection, which have been recognized as very frequent causes of abnormal combustion behavior, were analyzed.

An unmodified, direct-injected diesel engine was operated on diesel fuel and three blends of diesel fuel and sunflower oil. Heating of the fuels was used to change their viscosities. At normal fuel temperatures, specific fuel consumption and smoke emission increased for any power as sunflower oil content increased. Overall efficiency and exhaust temperature showed virtually no changes with fuel composition. Increasing fuel temperature caused a shift of best overall efficiency from high to low speeds, the magnitude of the shift depending on the plant oil concentration of the fuel. Thus fuel heating as a means of viscosity control may result in an efficiency penalty in the normal operating range of an engine. Typical plant oil induced engine contaminations such as wet stacking, excessive carbon accumulations, nozzle orifice blocking, and lubrication oil gelling were experienced.

The flow of diesel fuel through multi-hole injection nozzles is well understood. There are, however, no comprehensive experimental results for the design of injection nozzles for alternate fuels. A steady state flow generator was designed and employed to analyze the effects of the physical fuel properties and the needle lift on the discharge coefficient for the nozzle orifice. Three fuels were tested: diesel reference fuel, a 50/50 mixture of diesel fuel and sunflower oil, and 100%. sunflower oil. The fuel viscosities range from 3.0 cS to 30.0 cS at 40°C. Five injection pressures ranging from 3.5 to 13.8 MPa, and eight increments of needle lift between 0.031 and 0.940 mm were used in this investigation. A significant influence of needle lift, injection nozzle pressure, and physical properties of fuels on the flow coefficient in the normal operating range of a typical diesel engine was proven.

For the diesel engine performance analysis, the authors have developed computer programs that are implemented in the Statistical Analysis System (SAS). Programs have been developed specifically for the analysis of the diesel engine performance, residue formation on the internal engine parts, and fuel injection line pressure traces on the different alternative fuels while using EMA cycle. For the diesel engine testing, the consistency of the type of data and the experimental designs makes it possible to develop a system of SAS programs to analyze and report the data. The modularity of these programs makes adaptation from one trial to the next a simple procedure. Results from the analysis of the experimental data were in close agreement with the engineering interpretation of the observed differences between fuels. However, careful engineering interpretation of the results is required due to the high sensitivity of the statistical analysis.

Plant oils are considered viable replacement fuels for diesel engines. However, in order to become successful diesel fuel substitutes, problems associated with the formation of lacquer and carbon deposits on engine components must be resolved, else truly long-term engine reliability will not be possible. This paper reports some basic experiments into the formation of residues due to liquid phase reactions of a number of plant oils as a function of temperature. Heating tests on suspended drops of sunflower, corn, olive, and safflower oils were performed. Residue deposits were measured. For a heating air temperature of approximately 300°C, roughly 50% of the original oil drop mass remained as residue. This amount rapidly decreased as the air temperature was increased. Above approximately 500°C small amounts of residue formed which burned off shortly after formation. A methyl ester of sunflower oil also tested formed substantially less residue than any of the neat plant oils.

Five T31 turbochargers used on a direct-injected diesel engine were tested as part of a plant fuel evaluation program. The engine was tested on the 200-hour durability cycle proposed by the Engine Manufacturer's Association (EMA). Part of the evaluation was an investigation of premature carbon and lacquer deposits, and wear within the turbocharger due to oil deterioration from the hybrid fuels. The lubricant viscosities for all tested fuels, except the microemulsion, were within normal limits. A sudden increase in lubricating oil viscosity for the microemulsion was observed. At the same time, higher blow-by and increased lubricating oil consumption was noted. All turbochargers displayed journal bearing wear but no rubs or unusual seal leakage was formed. The turbine shafts showed various degrees of hot shutdown and high temperature operation for different fuels. The turbine wheels and housings varied in color from a soft gray to dark black.