Search Results

A NEW electronic circuit arrangement added to the electro-optical pyrometer developed at the University of Wisconsin indicates instantaneously the temperature in the combustion chamber of a diesel engine. The electronic device, which is described in this paper, solves an equation relating true temperature to intensity and wave length of monochromatic radiation from a luminous flame. True flame temperature is charted on an oscillograph as a function of such abscissas as time or crank angle. Several circuits are reviewed which were found unsuited for use with the pyrometer but which may be useful for other applications.

Obtaining and maintaining a stratified charge in a practical engine is a difficult problem. Consequently, many approaches have been proposed and reported in the scientific and patent literature. In attempting to assess the most profitable approach for future development work, it is important to group together similar approaches so that one can study their performance as a group. Making such a classification has the additional advantage of helping to standardize terminology used by different investigators. With this thought in mind, a literature study was made and a proposed classification chart prepared for the different engine combustion systems reported in the literature. For the sake of completeness, the finally proposed classification chart includes homogeneous combustion engines as well as heterogeneous combustion engines. Because of their similarity of combustion, rotary engines such as the Wankel engine are considered as “reciprocating” although gas turbines are not included.

DATA presented in this paper show temperature-time diagrams obtained from mufflers mounted on trucks which were traveling over their regular routes. Using these temperature data, specimens made of possible muffler materials were subjected to laboratory tests. A wide range of possible muffler materials and gas composition were covered in these tests. Results of the tests indicate that under long-run heavy-duty truck service, muffler failure occurs primarily because of high metal temperatures and that coated mild steel showed the most promise of longer muffler life.

An investigation into effects of multiple fuel introduction on isfc, rate-of-pressure rise, ignition delay, and smoothness of P-T diagram was conducted. Work, including pilot and manifold injection and the Vigom process, was conducted in a prechamber, an open chamber, and a Ricardo Comet chamber, all mounted on a CFR crankcase. Results show marked smoothening of the P-T diagram, with slight loss in fuel economy, particularly in the open chamber, and decrease in ignition delay for both high and low cetane fuels, especially at lower engine speeds. Data show that the quantity of preliminary fuel required for best performance changes considerably with cetane number of the fuel and with combustion chamber.

The purpose of the tests conducted on a single-cylinder laboratory engine was to determine the mechanism of combustion that affect exhaust emissions and the relationship of those mechanisms to engine design and operating variables. For the engine used in this study, the exhaust emissions were found to have the following dependence on various engine variables. Hydrocarbon emission was reduced by lean operation, increased manifold pressure, retarded spark, increased exhaust temperature, increased coolant temperature, increased exhaust back pressure, and decreased compression ratio. Carbon monoxide emission was affected by air-fuel ratio and premixing the charge. Oxides of nitrogen (NO + NO2 is called NOx) emission is primarily a function of the O2 available and the peak temperature attained during the cycle. Decreased manifold pressure and retarded spark decrease NOx emission. Hydrocarbons were found to react to some extent in the exhaust port and exhaust system.

This paper describes a method for studying reactions of hydrocarbons in S.I. engine exhaust gases. The reaction of ethane is described using an Arrhenius model (experimentally E = 86,500 cal/mole) for the rate of ethane diappearance and empirical correlations for distributions of the products carbon monoxide, ethylene, formaldehyde, methane, acetylene, and propane as a function of the fraction of ethane reacted. The results show that the nature of partial oxidation products from a nonreactive hydrocarbon may be less desirable from an air pollution viewpoint than the initial hydrocarbon.

The reasons for conducting research in a university are presented and discussed. It is concluded that fuel-engine studies are compatible with these reasons and therefore are well suited for university research. Past studies in this field are summarized and unanswered questions and future topics suitable for university investigation are suggested. Included in the topics discussed are: instrumentation, thermodynamic description of working fluids, fuel vaporization and atomization, combustion, and instantaneous heat transfer and mass flow rates. The steps that need to be taken to ensure continuing university interest in fuel-engine studies are presented.

A detailed mathematical model of the thermodynamic events of a crankcase scavenged, two-stroke, SI engine is described. The engine is divided into three thermodynamic systems: the cylinder gases, the crankcase gases, and the inlet system gases. Energy balances, mass continuity equations, the ideal gas law, and thermodynamic property relationships are combined to give a set of coupled ordinary differential equations which describe the thermodynamic states encountered by the systems of the engine during one cycle of operation. A computer program is used to integrate the equations, starting with estimated initial thermodynamic conditions and estimated metal surface temperatures. The program iterates the cycle, adjusting the initial estimates, until the final conditions agree with the beginning conditions, that is, until a cycle results.

The development of a high speed, multichannel data acquisition system is described. A precision magnetic tape recorder is used to record analog data from highly transient phenomena. Analog-to-digital data conversion is performed on a hybrid computer and the digitized data is processed using large, high speed digital computers. A detailed example of the application of the system to the measurement of rates-of-injection, rates-of-heat release, and instantaneous rates-of-heat transfer from the cylinder gases to the cylinder walls in a high speed open-chamber diesel engine is presented.

By the use of surface thermocouples to measure instantaneous temperatures, the instantaneous heat fluxes are calculated at several positions on the cylinder head and sleeve of a direct injection diesel engine for both motored and fired operation. Existing correlations are shown to be unable to predict these data. An analysis of convective heat transfer in the engine leads to a boundary layer model which adequately correlates the data for motored operation. The extension of this motored correlation to fired operation demonstrates the need for instantaneous local gas velocity and temperature data.

The ratio of two temperature gradients across the combustion-chamber wall in a diesel engine is used to provide a heat flow ratio showing the radiant heat transfer as a per cent of local total heat transfer. The temperature gradients were obtained with a thermocouple junction on each side of the combustion-chamber wall. The first temperature gradient was obtained by covering the thermocouple at the cylinder gas-wall interface with a thin sapphire window, while the second was obtained without the window. Results show that the time-average radiant heat transfer is of significant magnitude in a diesel engine, and is probably even more significant in heat transfer during combustion and expansion.