Patent GB-1051745-A (GB)
IPC: F02F3/00
Abstract: 1,051,745. Electric analogue calculating. FORD MOTOR CO. Ltd. Aug. 7, 1964 No. 32170/64. Heading G4G. Method of determining the relative heat transfers through different parts. of the piston of an I.C. engine, comprising erecting an electrical analogue representing heat transfer through the piston and corresponding three dimensionally thereto, or two dimensionally to an axial section; connecting one side of a potential source to the part of the analogue corresponding to the surface of the crown subject to combustion gases; connecting the opposite side of the source in parallel through electrical resistance analogues representing heat transfer through piston rings to the part of the analogue representing ring grooves; and then from current flows through the resistances deducing the relative heat transfer through certain parts of the piston represented by corresponding parts of the analogue. An internal combustion engine of conventional design (Fig. 1, not shown) has a pocketed spark plug and a piston with a well in the crown, two compression rings, and a scraper ring; the well and the plug pocket comprising the combustion chamber. To proportion the piston so that equal heat flow is achieved through the compression rings, an electric analogue is constructed (Fig. 2) comprising a square mesh network of identical resistors 26 whose boundary represents two dimensionally an axial section of the piston. Terminal 27 of a potential source 28 is connected over variable resistance 37 and plural identical resistances 29 to nodes 30 in the boundary of the network representing the piston crown, and terminal 31 of the source is connected over ganged identical variable resistors 32 to nodes 39, 40 located on the network boundary correspondingly to the compression ring grooves; two network resistors being omitted at 33, 34 to represent the grooves. The estimated crown temperature is represented by a voltage at 38 adjustable by. resistance 37, resistances 32 are adjusted to develop a voltage at 39 representing the temperature at the upper compression ring, and resistances 26 are removed from or added to the edge of the network, or the positions representing the grooves are varied, until the voltage at 40 equals that at 39. The resultant shape of the network boundary then represents the piston shape required to obtain equal compression ring temperatures in operation. A voltmeter 35 connectible between terminal 31 of the source and various nodes of the network enables voltage analogues of temperature and consequent isothermal lines of the piston structure to be derived. Heat flow from the underside of the piston (assumed to be about 1/6, that through the compression rings) is represented by plural identical resistances parallel connected between terminal 31 of the source and the boundary representing the piston underside, or as shown by a variable resistance 36 between the terminal and the boundary portion representing the skirt. The analogue network may alternatively comprise a pattern of homogenously electrically conductive material corresponding to a two-dimensional axial section, or a threedimensional conductive model e.g. a deformable mould containing conductive liquid; the electrical resistance of the resistors or conductive material being analogous to the thermal resistance of the piston material so that current is analogous to heat flow.