PROGRESS REPORT NO. 4 DIESEL IGNITION AND COMBUSTION J. A. >Bolt N. A. Henein Period: December,l, 1969 - December 31, 1969 January 1970 This project is under the technical supervision of the: Propulsion Systems Laboratory U. S. Tank Automotive Command 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 referee grade (Mil-F-45121) fuel.

II. OBJECTIVES 1. To extend the experimental engine combustion studies to gas pressures, 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. 5. Separate the thermal load on the cylinder head from that on the cylinder jacket, and determine their variation with the engine variables. 2

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 engihes. 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 3. 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 d. Wall surface temperature during the cycle 5

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 referee grade (Mil-F-45121) fuel (2) Diesel No. 2 fuel (3) Mil-G-3056 referee 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 combust.ion 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. (e) Experimental work to study the effect of fuel-air ratio on ignition

delay and other combustion phenomena of CITE fuel. This work was done at two levels of coolant temperatures, 170~F and 2500F. The coolant was ethylene glycol. (f) Experimental work to study the effect of the air-charge pressure on ignition delay and other combustion phenomena of CITE fuel. 3. Theoretical Analysis (a) 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. (b) A correlation was reached between the pressure rise delay and the air charge temperature. 5

IV. PROGRESS DURING THIS PERIOD (1) During this period experiments were made onethe ATAC-1 engine at supercharging pressures higher than those reached before. The experimental data obtained are being processed by using the digital computer programs made for this purpose. The high pressure runs were made with water at a constant outlet temperature of 170~F. The ethylene glycol was drained from the cooling system and replaced with water. It was found advisable to keep the same coolant conditions at those for the low pressure runs, for the sake of continuity and to avoid any effect of the coolant temperature on the ignition delay. (2) The cooling systems for the cylinder head and the cylinder jacket were separated, as shown in Figure 1. This required the use of blind cylinder head gaskets. The thermocouples required to measure the water temperatures at inlet and outlet were ordered. Separate sharp edge orifice-meters are used to measure the coolant flow rate to the head and jacket. 6

Coolant To Jets Sight Glass Water Inlet to Coolant Heat Exchanger ATAC- I Engine Pump Main Air - ($ Supply Valh Water Out to Drain '/water Tr Thermocouple Air Line to Valve -The —mostat. (Manually ie Thermostat Operated, Diaphragm Valve ) Diaphram Valve Figure 1. Separate cooling systems for the cylinder head and cylinder jacket.

V. FUTURE PLANS A. NEXT PERIOD To analyze the experimental results for the effect of gas pressure on the ignition delay and the other combustion phenomena. B. OVERALL (1) To instrument the engine for the measurement of the following exhaust emissions: nitric oxide, unburned hydrocarbons, carbon monoxide. (2) To reach a correlation between the air charge pressure and ignition delay. 8

VI. SIGNIFICANT ACCOMPLISHMENTS These consist of publications that resulted from the work done on Contract No. DA-20-018-AMC-1669(T). These publications are as follows: 1, "Ignition Delay in Diesel Engines." Presented at the SAE Annual Meeting in January 1967o 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." SAE paper No. 690557, presented in the SAE West Coast Meeting held in Seattle, Washington, August 14, 1969. This paper is given in Appendix B. 4. "The Effect of Some Engine Variables on Ignition Delay and Other Combustion Phenomena in a Diesel Engine." Paper No. 39, to be presented at the "Symposium on Diesel Combustion," Institute of Mechanical Engineers, London, England, April 1970. The paper has been approved with minor corrections by TACOM, and has also been accepted for publication by the Institution. 5. The work on the present project has been extended to April 30, 1970, to include exhaust emission studies. 9

VII. PROJECT COMPUTER GRAPH RECORDS Proj. Beg. Date: 1-28-69 P.D.: J. A. Bolt ~ Account No.: A 2451 Total Auth'n.: $29,609 P.R.: D. M. Plawchan Sponsor: DAAE07-b9-C-12b9 Proj,. Exp. Date: 1-27-70 Current Auth.: $29,609 - New 1-2-b9 to 1-27-7 Final Report Due: 2-27-70 Funds Available October 31: $8,753.46 40,000 35,000 30,000 25,000 20,000 a 15,000 10,000.) z 5,000 0 1:$500 F 1969 M A M JJ A S O N D J 1970 MONTH Prorated uncommitted balance Actual uncommitted balance O10

ACCUMULATIVE TECHNICAL PROGRESS, % OF TOTAL 0 0 0 0 OD 0 0 0 I I l 0 0 CL Q._ - O z I,3 z 0 cs 4 __"_-l _ I I I I _`'~11 N N.. N. -N N. N

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

UNIVERSITY OF MICHIGAN 3 9015 02229 1408111111 3 9015 02229 1408