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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.

A neat, alkali-refined sunflower oil, a 50/50 blend (v/v) of sunflower oil and #2 diesel fuel, and 100% #2 diesel fuel were evaluated in a direct injected, one-cylinder Petter engine according to the SAE 13 mode test procedure. The experiment was conducted to evaluate the effects of plant oil based alternative fuels on exhaust emissions and to simultaneously compare the test fuels. Additionally, the effect of engine load and speed on the exhaust emissions using the plant oil alternative fuels was statistically evaluated. The response variables were CO, NO, HC, and smoke. The predictor variables were the concentration of sunflower oil in the test fuel, the engine speed, and load. A multivariate test and covariance analysis were used for the results evaluation.

The paper* describes the analysis of experimental results of a laboratory flow apparatus used to measure the energy released during premixed combustion at atmospheric pressure in near quiescent air. The flow apparatus, described in a parallel paper, has the means to provide air temperatures in the range between 800 and 950° K. 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 difference in response times between the two sensors offers information about the non-luminous premixed combustion. Four fuels, No. 2-D diesel fuel, a 50/50% volumetric mixture of diesel fuel and sunflower oil, neat sunflower oil, and neat high oleic safflower oil were used.

Field tests for a variety of fuels on different tractor engines were carried out during the summers of 1981 through 1986. Fuels tested included alkali refined and winterized sunflower oil blended with diesel fuel, crude degummed sunflower oil blended with diesel fuel, high oleic safflower oil blended with diesel fuel, methylester of sunflower oil, or soybean oil. Blends of either 25% vegetable oil and 75% diesel fuel or 50% vegetable oil and 50% diesel fuel were used. Methylesters were not blended with diesel fuel. The manufacturers that participated in the project were John Deere, J.I. Case and Allis Chalmers. The project indicated that farm diesel tractors can be operated on any of the fuels that were tested. Care should be taken, however, since some signs of premature engine problems were observed. In general, continued use of these fuels cannot be recommended at this time.

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.

This paper presents the evaluation results from the analysis of different blends of fuels using the 13-mode standard SAE testing method. Six high oleic safflower oil blends, six ester blends, six high oleic sunflower oil blends, and six sunflower oil blends were used in this portion of the investigation. Additionally, the results from the repeated 13-mode tests for all the 25/75% mixtures with a complete diesel fuel test before and after each alternative fuel are presented.

This paper presents the evaluation results from the EMA durability test on 25% high oleic sunflower oil/75% diesel fuel and 25% high oleic safflower oil/75% diesel fuel. The test results from both fuels were compared to the outcome for a standard diesel fuel. The fuels were compared based on the performance and emissions results including; power output, fuel consumption, CO, CO2, NO and HC and the carbon and lacquer residue formation on the internal parts of the engine. The results indicated no significant change in engine performance for the tested fuels, throughout the duration of the investigation. The carbon and lacquer residue formations were within a normal range for both fuels in comparison to the results from the fuel for standard diesel fuel.

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.

A new statistical procedure to use with the Engine Manufacturers Association 200 hour duraability test for alternate fuels evaluation has been proposed. Data from a laboratory endurance test is used to illustrate the proposed statistical procedures. The assumptions for each statistical test are given. Further, problems encountered during the endurance test which affected the validity of the statistical tests are discussed.

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 effect of temperature on the rate of lacquer deposit formation from neat sunflower oil on the needles of fuel injection nozzles was investigated. Boson fuel injection nozzles were tested on a fuel injection calibration stand. A pneumatic leak test was developed to monitor the needle clearance reduction due to deposit buildup. For fuels with physical and chemical properties similar to those of neat sunflower oil, excessive residue on the internal surfaces of the injection nozzles is likely to occur with the ultimate result of complete needle immobility. The rate of the lacquer buildup on the needle increases with temperature. Prior to final needle sticking, delay in start of injection, sluggish needle lift, increases in duration of injection, maximum, final residual, and maximum residual line pressures, and decrease in maximum needle lift can be observed. Based on the obtained results, the temperature of injection nozzles handling plant oil fuels should be kept as low as possible.

A numerical optimization technique has been applied in order to obtain the optimum level of some design variables of the diesel fuel injection nozzle. A description of the optimization procedure is provided together with a discussion of the physical and mathematical flow model used. Sample applications of the optimization procedure addressing design of a fuel injection nozzle consideration along with comparisons among three different fuels are presented. The fuel injection mean rate, the diameter of the injection cavity, and the diameter of the injection orifice were used as the objective functions in different aspects of the optimization procedure. Chosen design variables were: the angle of the needle tip, the diameter of the nozzle injection cavity, and the injection orifice diameter. Some constraints characterizing the operating conditions of the injection nozzles were taken under consideration.

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.

The multivariate statistical procedure has been used to compare various alternate fuels based on the long term engine performance. The results from the multivariate analysis of covariance procedure, which does the simultaneous comparison of the chosen response variables, were adjusted for time of engine operation since the time factor was found to be significant. The assumptions for this test procedure are presented. Problems which could affect the validity of the statistical procedures for the laboratory endurance test are discussed. To illustrate the statistical method, data from a laboratory screening endurance test was used. Results of the analysis were in close agreement with the engineering interpretation of the observed differences between fuels.

The effect of increased clearance between the needle and its guides in a fuel injection nozzle on the rate of lacquer deposit formation from neat sunflower oil was investigated. Bosch fuel injection nozzles were tested on a fuel v injection calibration stand. The needle clearance reduction due to deposit buildup was monitored with a pneumatic leak test. Two test series of 100 hours duration each were performed at a temperature of 350°C. Each series consisted of ten 10-hour segments with a complete system shutdown after each segment. For the first test series the system was allowed to cool down before each shutdown. During the second test series the system was stopped while still hot. For fuels with physical and chemical properties similar to those of neat sunflower oil, excessive residue on the internal surfaces of the injection nozzles is likely to occur with the ultimate result of complete needle immobility.

A new type of centrifugal pump which can be used for transportation of alternate fuels such as coal slurries was tested. Design and performance of the pump, and analysis of the fluid flow in the pump is presented. The unique internal flow pattern, which was determined using a high speed camera, results mainly from the recessed impeller design and the geometry of the blades. The qualitative and quantitative analysis of the flow profiles indicate the existence of suitable conditions for a decrease in the direct contact of the abrasive particles of the slurry with the interior surface of the pump which translates to longer maintenance-free performance. The test pump performance for slurries at higher concentrations compared well with the existing slurry pumps. The highest concentration used during the test was 60% by weight. At this level the maximum efficiency of the pump was 30%. The corresponding power required and the flow rate were 5.97 kW and 528 L/min, respectively.

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.