PROGRESS REPORT NO. 1 DIESEL IGNITION AND COMBUSTION J. A. BOLT N. A. ~ENEIN Period: January 28, 1969 to February 28, 1969 March 1969 This project is under the technical supervision of the: Propulsion Systems Laboratory U. S. Army Tank-Automotive Center Warren, Michigan and is work performed by the: Department of Mechanical Engineering The University of Michigan Ann Arbor, Michigan Under Contract No. DA-AE07-69-1289

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I. BACKGROUND A program of activity to study the combustion process in supercharged diesel engines has been developed at The University of Michigan. This program is primarily concerned with the ignition delay and the effect of the several parameters on it. A special concern is given to the effect of the pressure and temperature of the cylinder air charge and engine speed on ignition delay. The program also includes the study of the effect of these variables on other combustion phenomena such as smoke, rate of pressure rise, maximum pressure reached in the cylinder, and rate of heat release. The different types of delay have been studied in detail and an emphasis is made on the pressure rise delay and illumination delay. The instruments needed for the measurement of these two delay periods have been developed and a continuous effort is being made to improve their accuracy. The present contract is a continuation of the work completed under previous Contract No. DA-20-018-AMC-1669(T) during the period July 1, 1964 to December 1, 1968. This research is being made on the ATAC high output open combustion chamber engine, with CITE refree grade (Mil-F-45121) fuel.

II. OBJECTIVES 1. To extend the experimental engine combustion studies to gas pressure-, at the start of injection, higher than the 1200 psia reached in Phase IVa of Contract DA-20-018-AMC-1669(T). This will require supercharging pressure up to four atmospheres, and pressure at the start of injection to 1600 psia. 2. Determine the wall temperatures and thermal loading on the cooling system over the complete range of supercharging pressures of item (1). 3. Analyze the experimental data of the complete range of the supercharging pressures and find a correlation between the ignition delay and the gas pressure. 4. Observations include the ignition delay, rate of pressure rise, maximum cylinder pressure, and exhaust smoke.

III. CUMULATIVE PROGRESS The cumulative progress on this work consists mainly of the previous study made under the Contract No. DA-20-018-AMC-1669(T). This work included both theoretical and experimental studies on two engines. The Lister-Blackstone engine has a precombustion chamber and the ATAC-1 engine has an open combustion chamber. A. LISTER-BLACKSTONE ENGINE Cumulative progress has been made in the following areas: 1. Review and analysis of previous work 2. Theoretical analysis 5. Experimental work on Lister-Blackstone engine 4, Comparison between the present work done on the Lister engine and previous work in bombs and engines B. ATAC-1 OPEN COMBUSTION CHAMBER ENGINE The cumulative progress made on ATAC-1 engine can be divided into three major areas: 1. Engine instrumentation 2. Experimental work 3. Theoretical work 1. Engine Instrumentation The engine has been instrumented and all the instruments calibrated to measure the following: a. Power output and engine speed b. Gas pressure during the cycle c. Illumination due to combustion do Wall surface temperature during the cycle

e. Wall temperature in the fire deck near the inlet and exhaust valves f. Fuel pressure before the injector g. Injector needle lift h. Air flow rate into the engine and its temperature and pressure before the inlet valve i. Fuel flow rate j. Intensity of smoke in the exhaust gases, their temperature and pressure 2. Experimental Work on ATAC (a) Experiments were made on the ATAC engine to study the effect of temperature on ignition delay and combustion characteristics of the following fuels: (1) CITE refree grade (Mil-F-45121) fuel (2) Diesel No. 2 fuel (3) Mil-G-3056 refree grade gasoline fuel (b) Experimental work to compare between the combustion phenomena and the rate of heat release for the three fuels, under naturally aspirated conditions. The several computer programs made for these elaborate computations proved to be very successful, and can be used in future heat release computations under any set of running conditions. (c) Experimental work to study the effect of engine speed on the ignition delay and other combustion phenomena. Engine speeds covered a range from 1000 rpm to 3000 rpm. (d) Experimental work to study the effect of coolant temperatures on the combustion process of CITE fuel. The coolant used for these tests was ethylene glycol at temperatures up to 305~F.

3. Theoretical Analysis A thermodynamic analysis was made to study the different types of energy and processes taking place during the ignition delay, and to compare between the different definitions used in the literature for the ignition delay,

IV. PROGRESS DURING THIS PERIOD During this period, the engine was prepared to start the experimental work at high supercharging pressures. All the engine systems including the cooling, lubricating, inlet air, and exhaust systems were checked. Also the instruments were calibrated.

V. PROBLEM AREAS AND CORRECTIVE ACTION The fuel injection pump, originally supplied with the ATAC-1 engine, leaked excessive amounts of fuel into the oil sump. This required the lubricating oil to be changed after each run. The leakage became excessive after the tests made on the gasoline fuel. This pump was sent for complete overhaul to: AMBAC Industries, Inc., Springfield, Massachusetts. We have requested that a barrel and plunger of the ducted type be installed in this unit to avoid future dilution of the sump lubricating oil with fuel.

VI. FUTURE PLANS To extend the experimental engine combustion studies to gas pressures, at start of injection, higher than 1200 psia.

VII. SIGNIFICANT ACCOMPLISHMENTS These consist of publications that resulted from the work done on Contract No. DA-20-O18-AMC-1669(T). These publications are as follows: 1. "Ignition Delay in Diesel Engines." Presented at the SAE Annual Meeting in January 1967. Published in the SAE Transactions, 76, paper No. 670007. 2. "Correlation of Air Charge Temperature and Ignition Delay for Several Fuels in a Diesel Engine." SAE paper No. 690252 presented at the SAE Annual Meeting, Detroit, on January 17, 1969. 3. "Diesel Exhaust Smoke: Effect of Some Fuel and Engine Factors on Its Formation." This paper is scheduled for the SAE West Coast Meeting to be held in Seattle, Washington, between August 11-14, 1969.

VIII. PROJECT STATUS Start of Contract: January 28, 1969 Expiration Date: January 27, 1970 Funds available at the start of contract: $29,609.00 10

DISTRIBUTION LIST No. of Contract Distribution Copies Name and Address U. S. Army-Tank Automotive Center 4 Propulsion Systems Laboratory Warren, Michigan 48090 Attention: SMOTA-RCP Internal Distribution Professor Jay Bolt Professor E. T. Vincent 1 Professor N. A. Henein 2 11

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