FLOW TEST OF A BRISTOL SLEEVE-VALVE ENGINE CYLINDER 0% Mark Riley Thomson Submitted in Partial Fulfillment of the Requirements for the Bachelor of Science Degree in Mechanical Engineering from the Massachusetts Institute of Technology 1951 Signature redacted . Mi ov Instructor in Charge of Thesis olgnature redacted May 18, 1951 Professor Joseph 8, Newell Secretary of the Faculty Massachusetts Institute of Technology Dear Professor Newell: In partial fulfillment of the requirements for the degree of Bachelor of Science from the Massachusetts Institute of Technology, I herewith submit a thesis entitled "Flow Test of a Bristol Sleeve-Valve Engine Cylinder, Sincerely yours, Signature redacted Mark R., Thomson TABLE OF CONTENTS: Letter of Transmittal Table of Contents Acknowledgements Abstract Introduction Description of Test 10 Diagram of Apparatus 12 Description of Apparatus 13 Photograph of Cylinder Parts, aL Valve Port Profiles ib Curve "C Ay" vs. C.A!, "Hercules" 16 Curve "CyAy" vs. C.A.", "Cyclone" 17 Summary of Results 18 Engine Specifications 19 Conclusions 20 Curve "e, vs. @" 21 Application of # 22 Calculations 23 Curve "Cy vs. L/D", "Cyclone" 27 Curve "L vs. C.A.", "Cyclone" cd Curve ih + vs, A", "Hercules" «J Errors J Suggestions for Further Study LY: Bibliography Data: Sleeve Position vs, C.A. Data: Flow Test Data: Calculated Air Flow The author wishes to express his appreclation for the assistance and supervision given to him by Professor C, Fayette Taylor Professor P, M, Ku Professor William A, Leary Mr, James C, Livengood and the personnel of the Sloan Laboratory, Acknowledgement is also made for the use of the facllities of the MIT Hobby Shop and the MIT Experi- mental Foundry, ABSTRACT One of the primary advocates of the use of sleeve valves in high performance internal combustion engines has been the Bristol Aeroplane Company, Ltd., of Bristol, England, Development by this firm began in 1927, and through successive stages of modification in design and construction evolved the "Hercules" engine, a fourteen cylinder, double row radial type, that has proved itself a serviceable, efficient power plant in more than 60,000 applications, The Bristol Company claims for its engines greater simplicity of construction and maintenance, due mainly to fewer component parfs; cleaner aerodynamic profile, in the absence of poppet valve assemblies atop the cylinders; and greater engine output and efficiency resulting from improved induction and combustion charac- teristics, B8ince the induction system 1s effected more directly by the use of the sleeve valve than other characteristic parts of the engine, and since the air capaclty, hence, power output, is limited by the efficiency of the induc=- tion system, it 1s the purpose of this investigation to compare the flow characteristics of the induction valve system of the "Hercules" engine cylinder to similar data for a conventional poppet valve system, A useful method for the determination of valve per formance 1s the steady flow test, in which the valve coefficient is determined for a specified valve setting, at a given pressure drop across the valve, The average valve coefficient for all positions of the valve during the inlet process can be found by means of a series of such tests; and this average coefficient, together with a characteristic valve dimension, is useful as a measure~ ment of the performance of the valve in the engine cylinder, From the standpoint of air capacity, the results of this investigation show the sleeve valve induction system of the "Hercules" engine to be superior to the poppet valve system used in the Wright "Cyclone" engine, INTRODUCTION: Since man's earliest successful attempts to fly, the need has been established for lightwelght engines of high power output. The high performance aircraft engine in its present state of development is limited in its output by the material from which 1t 1s made, and its physical dimensions, Now, the power output of any heat engine 1s dependent on the mass of working fluid passing through the engine in a given time; in the case of the internal combustion engine, high air capacity is attainable by using a large engine, or by increasing the density of the entering alr, Directly related to the alr capacity of an engine 1s its volumetric efficiency, and it is toward the attainment of high volumetric effi- ciency that the induction system of an engine must be designed, The question has risen whether an induction system designed around poppet valves 1s or is not superior to a system designed around a sleeve valve arrangement, Studies of flow through poppet valves are frequently made using steady flow techniques; such tests usually consider only the valve and valve seat as the system involved, and the air flow through the valve standing alone might reasonably be assumed to vary somewhat from that through the valve in its actual installation in an engine cylinder, Weiss and Yee in a thesis written in 1943, have considered the importance of exhaust valve design with respect to engine efficieney, but their attention has been focused on the valve itself without regard for the "environment" of the valve, A more com- prehensive coverage of this steady flow anology in 1ts application to inlet valve design can be found in the report of Wood, Hunter, Taylor, and Teylor, The amount of residual gases left in the cylinder after the exhaust stroke is reflective of the efficiency of the exhaust system; however, the effect of these residual gases 1s of secondary lmportance to the effect of volumetric efficiency. Hence, this investigation is primarily concerned with the inlet valve systen, Now, the question arises whether the design of the valves is the predominating factor affecting air capacity of a given engine, or whether an optimum desigh level has already been reached. Livengood and Eppes’ have 1. Weiss, H, J., and Yee, Y, L.: Investigation of Exhaust ValveDesignUsingSteady Flow. BS Thesis, M.I.T., 1943 2. Wood, G, B,,Jr; Hunter, D. U,; Taylor, E.8.; and Taylor, C. F.: AirFlow ThroughIntake Valves. SAE Journal, Volume 50, No, 6, June, 1942, 3, Livengood, J, C., and Eppes, J,V.D,; TN 1366, NACA, 1947, studied the effect on volumetric efficiency of such variables as piston speed and valve flow characteristics expressed as a dimensionless parameter, It 1s evident from their report that an increase in volumetric efficiency can be obtained by increasing the flow coefficient of the valve, but it can also be obtained by altering the valve timing. It might then be possible to have the game volumetric efficiency in a cylinder having a rela- tively poor inlet valve flow coefficlent but with optimum valve timing , as in a cylinder having a superior inlet valve coefficient but with valve timing other than optimum from the air capacity standpoint, The same or slightly lower volumetric efficiency may thus be had in a poppet- valve engine as in a sleeve valve engine, but the lower mechanical efficiency of the sleeve valve system may have a noticeable effect in reducing brake power output, The figures used for the power output of each engine in this work are those published by their respective men ufacturers, It might be interesting to note, however, that the actual rated power of the Wright R~1820 engine is, at the time of this writing, nearly equal to that of the Bristol "Hercules" engine, it DESCRIPTION OF TEST: Before removal from the engine, the movement of the sleeve with respect to the engine crankangle was recorded in terms of its distance from the top of the cylinder, and its rotation with respect to the cylinder, The distance from the top of the cylinder head was read directly to the accuracy of one hundredth of an inch by means of a steel scale, Accuracy was enhanced by the use of a knife edge attached to the cylinder head while measuring, A crank similar to the one used on the englne was used to provide conveniently and accurately the elliptical motion of the sleeve, Adjustment was provided to orient the sleeve correctly with the reference points already found, The linear dimension of the sleeve motion was the most accurate dimension, and was thus deemed appropriate for notation of the sleeve motion during the test, The conduct of the test itself was straightforward: A pressure difference of ten inches of water was maintained across the cylinder ports by adjusting the air flow accor= dingly, The pressure drop across the orifice, the pressure before the orifice, and the sleeve position were noted for different positions of the sleeve assumed during the inlet stroke of the engine, The error that would otherwise have been intruduced by the effect of valve overlap was elimi- nated by sealing the exhaust porte externally, Flow was stable throughout the test, enabling manometer readings to be made easily, .Atmospheric temperate and pressure were, of course, noted at the time of the test, PeORIFICE TYrrr ee CYUNOER & SLEEVE | | = : g, UJ UJ 2) GuosE vaLve 7 TT 0 PowPo Parw Pr PrP full n,SURGE THM | ly - pr 70 NASH [Fur Schematic Diagram of Apparatus. DESCRIPTICN OF APPARATUS: A cylinder, Jjunkhead (cylinder head) and sleeve were removed from the engine and attached to the surge tank by means of a mounting flange and bracket designed especially for that purpose, The sleeve motion was reproduced authentically by means of a crank attached to the mounting bracket and engaging the sleeve crank ball joint, A steel tube fitted inslde the sleeve provided passage for the air between the cylinder assembly and the surge tank, A sponge rubber strip