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A mathematical model of an open-chamber diesel engine has been programmed for solution on a digital computer. The program incorporates an automatic procedure which, given the limits of design variables, will predict the values of these variables that will optimize engine performance. This technique can provide these results in a fraction of the time taken by parametric methods and provides a quick and efficient tool that can be used directly by the designer or the development engineer. Examples are given to demonstrate how the technique can be employed to maximize engine power to torque.

The formation of nitric oxide in the combustion chamber of a spark ignition engine is formulated by developing a simple model. The state of the gas in the chamber and its thermal properties are estimated during a complete cycle. The estimation of the nitric oxide formation is based on the Zeldovich mechanism and assumes the burned gas either in a fully mixed or unmixed state. A simple heat transfer relation is used to estimate the heat loss from the gas to the chamber walls. The effect of the position of the ignition source relative to the exhaust port is also taken into account, and the predicted nitric oxide concentrations are compared with experimental results from a single-cylinder variable compression ratio IFP engine. It is found that the nitric oxide concentration predicted by the model agrees well over most of the operating range with the experimentally measured nitric oxide concentrations in the exhaust gas.

Hydrogen-supplemented fuel was investigated as a means of extending lean operating limits of gasoline engines for control of NOx. Single-cylinder engine tests with small additions of hydrogen to the fuel resulted in very low NOx and CO emissions for hydrogen-isooctane mixtures leaner than 0.55 equivalence ratio. Significant thermal efficiency improvements resulted from the extension beyond isooctane lean limit operation. However, HC emissions increased markedly at these lean conditions. A passenger car was modified to operate at 0.55-0.65 equivalence ratio with supplemental hydrogen. Vehicle emissions, as established by the 1975 Federal Exhaust Emissions Test, demonstrated the same trends as the single-cylinder engine tests. The success of the hydrogen-supplemented fuel approach will ultimately hinge on the development of both a means of controlling hydrocarbon emissions and a suitable hydrogen source on board the vehicle.

The characteristics of multiple spark ignition systems with respect to engine performance, emissions, lean misfire, and tolerance to exhaust gas recirculation (EGR) have been investigated using a carbureted single-cylinder engine. The results, which were compared to those obtained with a standard single spark ignition system, show that both lean misfire limit and EGR tolerance are extended with the multiple spark system. The amount of extension varies with engine load, being largest at the lighter loads studied. Engine power and emissions at non-misfiring conditions are the same with both ignition systems.

The small gas turbine engine, such as Avco Lycoming's LTS 101, has many intended applications. Use of improved materials and processes, which minimize labor input and material costs while maintaining standards of reliability and performance, makes it possible to meet customer requirements and acceptance for intended application. In the turbine section, the turbine wheels offer an opportunity to effectively combine reliability, performance, and cost-saving techniques. This paper describes the various process approaches used in manufacturing LTS 101 turbine wheels which proved to be successful in achieving these goals.

A performance model of a Wankel engine is developed which performs a leakage mass balance, accounts for heat transfer and flame quenching, and predicts the mass fraction burned as a function of chamber pressure. Experiments were performed on a production Wankel engine to obtain chamber pressure-time diagrams, and engine performance and emissions data. Model predictions of mass burned, global heat transfer, and hydrocarbon emission gave good agreement with measurements. Predictions of oxides of nitrogen are higher than measurements, especially at low loads. This is thought to be due to the adiabatic core gas assumption in the model. The need for a Wankel boundary layer study is identified.

The heat exchanger of a regenerative gas turbine is usually calculated for uniform flow distribution. In practice, however, the flow distribution is not uniform. Nonuniformity of flow is caused by the geometry of the flow path and manufacturing tolerances of the regenerator discs themselves. The consequence is a drop in regenerator efficiency. Cold airflow tests were carried out on a model gas turbine to find optimum flow path geometry and data to calculate the drop in heat exchanger efficiency. The entire test was conducted under true Newton number conditions. The efficiency calculation of the heat exchanger based on test results shows that the efficiency drop can be several percent. Suggestions are made as to the shape of the regenerator cover and power turbine diffuser.

In a ceramic gas turbine, the rotor is the component with the most demanding requirements, and its performance limits will determine the turbine operating conditions. Chemical vapor deposited (CVD) silicon carbide (SiC) has been shown to be one of the most promising materials considering strength, creep, oxidation, fabricability, and cost. The CVD process has produced rotors in the desired configuration and test samples with strengths of 100 ksi at 1400°C and peak values of 200 ksi at 1500°C. CVD SiC is a pure material with very low creep rates showing potential for operation to 10,000 h and possibly beyond at 1600°C and 30 ksi compared to 1000 h at 1200°C and 10 ksi for the best silicon nitride (Si3N4) available. Under equal heat flux conditions, the thermal stress generated in CVD SiC is similar to Si3N4, and CVD SiC has superior oxidation resistance to other materials tested.

The newest grades of hot rolled, high-strength low-alloy (HSLA) steels, characterized by an ultrafine grain size (ASTM 11-13), exhibit an excellent combination of strength (50,000-80,000 psi yield strength) and ductility. Various formability tests demonstrate that these steels are highly formable in spite of their high strength. Compared to mild steels, plane strain and stretch deformation characteristics of HSLA steels are reduced by only 25-40%. In the drawing mode deformation, HSLA steels perform similarly to mild hot rolled steels. Because of higher strength, the ductility of sheared work-hardened edges is low and sensitive to inclusion shape. When sheared edge deformation is necessary, the cracking tendency can be substantially reduced by converting stringer inclusions into globules.

Sensory studies have described diesel exhaust odor in terms of two major odor character groups-oily-kerosene and smoky-burnt. The odorous compounds have been identified in a detailed analytical chemistry-odor study. The oily-kerosene odor group is associated with the aromatic portion of the unburned fuel-principally, the alkyl substituted benzenes, indans, and tetralins. The smoky-burnt odors arise from partial combustion products of the paraffin and aromatic fuel components. Our studies have shown a good correlation between exhaust odor intensity and abundance of the partial combustion products. An analytical method has been developed, based on liquid chromatography, for the quantitative expression of exhaust odor intensity by measurement of the smoky-burnt odor group. Initial survey studies show the method to be applicable over a wide odor emission range. Fuel variation has little effect, whereas injector variables do influence odor intensity.

Analytical estimates of NOx formation as a function of peak flame temperature and residence are potentially useful in the conceptual design studies of combustors for low NOx emissions characteristics. It is apparent that the accuracy of these design studies depends upon the actual flow conditions and the variations of the time and temperature occurring within the combustor relative to the estimates. An experimental program was undertaken to determine the limitations, as imposed by practical combustor and fuel systems designs, on the potential reduction of NOx emissions based on flame temperature and residence time predictions. A premix combustor designed to operate at an equivalence ratio of 0.75 was tested with an ideally mixed gaseous fuel. This produced data demonstrating the lower limits of NOx that might be attained and is compared to analytical model predictions. Further, burner designs incorporating lean equivalence ratios, premixing, and rapid mixing concepts were also tested.

The odor profile method has been applied to the measurement and analysis of diesel exhaust odor. The human sensory panel has described the odor of diluted exhaust and analytical fractions isolated from the exhaust in terms of total intensity of aroma (TIA), and individual odor character notes. For convenience, diesel exhaust odor can be described in two character groups-oily-kerosene and smoky-burnt odor. The odorous species were determined by detailed chemical analyses supported by comparative data from reference compounds. To achieve reliable quantitative odor intensity measurements, it was necessary to present the odor panel with a series of concentrations (dilutions) of exhaust in air over a wide range. The odor intensity at a given exhaust concentration is computed from a least squares analysis of the entire panel data. The results demonstrate an odor intensity range of slight to moderately strong for diesel exhaust at 1000:1 dilution.

A new theory was developed to obtain an exact sinusoidal simulation of material fatigue life when subjected to a gaussian narrow band random loading. The theory was based upon duplicating the probability density distribution of peak amplitudes that is Rayleigh. An experimental investigation was conducted to obtain validity of this theory. The fatigue lives obtained under the two types of loadings compared within 10%. The statistical probability density distribution of input and output acceleration processes for both types of loading compared very well. It is believed that the approach of the theory described herein can be applied to any real loading time history where the probability density distribution of the actual field service peak amplitudes is known.

The measurement of noise can be a rather complicated task. At least, it must not be taken for granted. One problem is that noise is a dynamic phenomenon. The other problem is that a microphone often affects the acoustical field it is trying to sense. These are strange phenomena to those of us who deal only with slowly varying signals and with transducers which do not affect their environment. The object of this paper is to list and explain the precautions that must be taken when measuring noise and documenting acoustical data for SAE criteria.

The propagation of sound from a small source over the ground, considered as an impedance boundary, is discussed theoretically and compared with measurements over short grass and asphalt. Interference phenomena relevant to the measurement configurations in SAE standard procedures for testing vehicles are emphasized. The effect of the ground impedance on propagation at the longer distances relevant to airport and highway design is also discussed.

This paper describes the results of a public opinion survey on testing of diesel exhaust odors conducted during 1969 and 1970. Major goals of the research were to relate public opinion of the odors and the objectionability associated with them to odor intensity, and to obtain a dose-response curve as the primary result. The dose-response curve was needed to assess odor-control technology by providing a criterion for deciding whether or not the effect of a given control item would be noticed by the general public, reduce complaints, or be worth the cost and effort required for its implementation. The engine used as the live odor source for the subject research was a two-stroke cycle type similar to those used in many buses. This engine type was chosen because its exposure to the public in urban bus applications is very widespread, and because a large portion of the Environmental Protection Agency's odor research had been performed with similar engines.

Only 2 of the 11 laboratories which have had diesel odor research projects underway during the last 16 years are still active in this research area. Much of the earlier work was devoted to developing diesel odor sampling, standards, and measurement techniques. Subsequently, work became generally focused upon the chemical identification of the odorants, a very difficult task due to their large number and low concentrations. After three years of concentrated effort involving the development of new odor measurement, sampling, and diesel exhaust analysis and preparation techniques, odorants comprising the two major diesel odor characteristics were identified. Compounds which are also components of diesel fuel were shown to contribute to one odor characteristic. Oxydized derivatives, generally of the same classes of compounds as those shown to contribute to the first odor characteristic, were tentatively identified by structure to comprise the second major odor characteristic.

A highly magnified picture of the surface of a shaft can be generated by running the profile signal from a stylus scanner into an X-Y recorder. Successive traces across a surface area can then be put together much the same as is the picture from a scanning electron microscope. Thus, a permanent record is made in which not only the lead of a shaft is identifiable, but also the surface condition including pits, flaws, burrs, and cracks.

It is very difficult for small cars to protect occupants in high-speed collisions. The Nissan ESV is of lightweight monocoque construction, and its body possesses crashworthiness designed to match the occupant protection system. This vehicle has experimentally proved to be effective in occupant protection. This paper primarily deals with the most difficult problem of crashworthiness in frontal collisions, first referring to the basic analyses and test results acquired in the development process, and then setting forth the body construction and test results of the two types of Nissan ESV (E1 and E2).

This paper describes and illustrates the more significant results obtained from development and test work on crashworthiness of three European ESVs in the 1500, 2000, and 2500 lb classes of current production cars. The diversity of weight, mechanical layout, and body features of the three types of cars-each type considered in the standard, reinforced, and ESV versions-has allowed a detailed survey of the more significant problems that may arise in improving crashworthiness. Emphasis is placed on the effect of the high specification requirements for the 4000 lb ESV in relation to the weight and cost of these car classes.