Methane and ethane are the two main components of natural gas and typically constitute more than 95% of it. In this study, a mixture of 90% CH 4 /10% C 2 H 6 diluted in 99% Ar was studied at fuel lean (equiv. ratio = 0.5) conditions, for pressures around 1, 4, and 10 atm. Using laser absorption diagnostics, the time histories of CO and H 2 O were recorded between 1400 and 1800 K. Water is a final product from combustion, and its formation is a good marker of the completion of the combustion process. Carbon monoxide is an intermediate combustion species, a good marker of incomplete/inefficient combustion, as well as a regulated pollutant for the gas turbine industry. Measurements such as these species time histories are important for validating and assessing chemical kinetics models beyond just ignition delay times and laminar flame speeds. Time-history profiles for these two molecules were compared to a state-of-the-art detailed kinetics mechanism as well as to the well-established GRI 3.0 mechanism. Results show that the H 2 O profile is accurately reproduced by both models. However, discrepancies are observed for the CO profiles. Under the conditions of this study, the CO profiles typically increase rapidly after an induction time, reach a maximum, and then decrease. This maximum CO mole fraction is often largely over-predicted by the models, whereas the depletion rate of CO past this peak is often over-estimated for pressures above 1 atm.

Even though the conventional method of supercharging and turbocharging of an internal combustion engine increases the engine specific power output, part of the shaft power developed by the engine is consumed by the superchargers. The control system that is present in both the chargers further complicates the system. This study proposes a novel method of forced induction in a diesel engine by using a jet compressor run by exhaust gas recirculation (EGR). This method apart from increasing the specific power output reduces the NOx formation by the engine due to forced induction. Performance analysis of the jet compressor using exhaust gas as the motive stream and atmospheric air as the propelled stream was carried out. Using the standard available code, the governing equations were solved numerically to get the optimum operating conditions such as exhaust gas pressure, temperature, and flow rate for a three cylinder diesel engine. The dimensions of the jet compressor were determined by solving the energy balance equations obtained from the constant rate momentum change method. Using the commercial software fluent, the performance optimization of jet compressor used for forced induction in a diesel engine was made for different percentage of EGR input and estimated the power output. From the results obtained, a performance map was drawn for the three cylinder diesel engine to get the optimum boost pressure and maximum entrainment ratio for a given percentage of exhaust gas recirculation and power output. Experiments were conducted on a three cylinder diesel engine fitted with a fabricated jet compressor with EGR used for forced induction application. Results obtained from the experiments were in good agreement with the numerical results obtained from fluent analysis.

Microalgae are currently receiving strong consideration as a potential biofuel feedstock to help meet the advanced biofuels mandate of the 2007 Energy Independence and Security Act because of its theoretically high yield (gal/acre/year) in comparison to current terrestrial feedstocks. For algal methyl ester biodiesel, fuel properties will be directly related to the fatty acid composition of the lipids produced by the given microalgae strain. Several microalgae species under consideration for wide scale cultivation, such as Nannochloropsis, produce lipids with fatty acid compositions containing substantially higher quantities of long chain-polyunsaturated fatty acids (LC-PUFA) in comparison to terrestrial feedstocks. It is expected that increased levels of LC-PUFA will be problematic in terms of meeting all of the current ASTM specifications for biodiesel. Moreover, these same LC-PUFA fatty acids, such as eicosapentaenoic acid (EPA: C20:5) and docosahexaenoic acid (DHA: C22:6) are known to have high nutritional value, thereby making separation of these compounds economically attractive. Given the uncertainty in the future value of these LC-PUFA compounds and the economic viability of the separation process, the goal of this study was to examine the oxidative stability of algal methyl esters with varying levels of EPA and DHA. Tests were conducted using a Metrohm 743 Rancimat with automatic induction period determination following ASTM D6751 and EN 14214 standards, which call for induction periods of at least 3 and 6 h, respectively. Tests were conducted at a temperature of 110 °C and airflow of 10 l/h with model algal methyl ester compounds synthesized from various sources to match the fatty acid compositions of several algae strains subjected to varying removal amounts of roughly 0% to 100% LC-PUFA. In addition, tests were also conducted with real algal methyl esters produced from multiple sources. The bis-allylic position equivalent (BAPE) was calculated for each fuel sample to quantify the level of unsaturation. The induction period was then plotted as a function of BAPE, which showed that the oxidative stability varied exponentially with the amount of LC-PUFA. The results suggest that removal of 45% to 65% of the LC-PUFA from Nannochloropsis-based algal methyl esters would be sufficient for meeting existing ASTM specifications for oxidative stability.

With the increase of combustion loading and the trend to reduce engine size, there is a need for thinner but stronger wet cylinder liners. While most of the current cylinder liners are made of gray cast iron, due to its good tribological behavior, machinability performance, and competitive price, alternative casting materials such as compact graphite iron, ductile iron, and even steel are being considered to address future engine demands. In this paper, a new ductile iron (DI) cast material for wet cylinder liners is presented. The material has about 60 and 70% higher limits, respectively, for tensile stress and fatigue resistance as compared to conventional gray cast irons, but without a penalty on the tribological properties. There is also a potential improvement to avoid cavitation on the outside surface due to its higher young modulus, which also equates to a higher stiffness. The tested cylinder liners were induction hardened on the running surface and a slide hone process was used to improve wear and scuffing resistance. The liners were tested in a heavy duty diesel (HDD) engine with a peak cylinder pressure (PCP) of 245 bar and showed similar wear as observed with conventional cylinder liners of gray cast iron material. The DI cylinder liners were also tested in an abusive scuffing engine test without any concern. The improved mechanical properties of the described new DI material introduce possibilities to reduce the liner wall thickness or increase specific output. The preliminary evaluation in this paper showed that this new material is feasible for HDD diesel engines with a PCP up to 250 bar. In cases where the customer needs to increase the bore diameter for output reasons there is the potential to reduce the liner wall thickness by up to 25% based on high mechanical properties (UTS, Young’s modulus and fatigue strength). In both cases, a FEA analysis to support the new component design is recommended.

Centrifugal compressors driven by induction motors are most common in the turbomachinery industry. When sudden transients occur in the driver due to upsets in electrical supply to the motor, the air-gap torque generated by the motor undergoes a transient spike. This in turn gets transmitted through the coupling to the drive-shaft of the driven equipment, causing momentary high spikes in vibration that are torsional in nature, and can sometimes result in shaft torques that can create catastrophic damage to driven equipment components. In order to analytically predict these peak torques that can occur during transients, a complete drive-train torsional model needs to be created for the mechanical system, and the driving torque values need to be derived from the motor electrical system of equations. Various line faults are possible with induction motor driven equipment. A generalized analytical procedure based on motor electrical parameters to predict the peak shaft torques of compressor drive shafts is investigated in this paper. The effects of shaft transients due to 3-phase short circuits and reclosures are analyzed. The simulation has been performed for an industrial compressor train, and has been presented from a mechanical system point of view, rather than electrical. Comparisons and inferences are also made based on the simulation results.

In gas turbine combustion the gas dynamic and chemical energy release mechanisms have comparable time scales, so that equilibrium chemistry is inadequate for predicting species formation (emissions). In current practice either equilibrium chemical reactions are coupled with experimentally derived empirical equations, or time-consuming computations are used. Coupling nonequilibrium chemistry, fluid dynamic, and initial and boundary condition equations results in large sets of numerically stiff equations; and their time integration demands enormous computational resources. The response modeling approach has been used successfully for large reaction sets. This paper makes two new contributions. First it shows how pre-integration of the heat release maps eliminates the stiffness of the equations. This is a new modification to the response mapping approach, and it performs satisfactorily for non-diffusion systems. Second the theoretical framework is further extended to predict species formation in cases with diffusion, which is applicable to gas turbine combustion systems and others. The methodology to implement this approach to reacting systems, and to gas turbine combustion, is presented. The benefits over other reaction-mapping techniques are discussed.

Further investigation of the turbulence time-frequency spectral structure and its anisotropy and nonhomogeneity has been carried out in the combustion chamber of an automotive diesel engine with a high-squish reentrant in-piston-bowl and a helical intake port. An advanced HWA technique was applied for turbulence measurements along the injector axis, under motored engine conditions in the speed range of 600–3000 rpm. Autospectral density functions of each fluctuating velocity component, as was determined by a specific sensor-wire orientation, were evaluated in consecutive crank-angle correlation intervals during the induction, compression, and early expansion strokes. In order to study the speed dependence of the turbulence-structure anisotropy and nonhomogeneity in different portions of the engine cycle, time-scales of cycle-resolved and conventional turbulent fluctuations were analyzed as functions of the engine speed for different wire orientations, measurement locations, and correlation intervals. Anisotropy and nonhomogeneity were generally significant at low engine speeds, whereas a tendency towards isotropy and homogeneity was found by increasing the speed. With specific reference to the bowl-generated turbulence, spectral anisotropy was remarkable at all speeds in the reverse-squish flow, close to the cylinder-head wall. However, spectral nonhomogeneity was the main feature of the direct-squish flow at low engine speeds.

A theoretical study was conducted to investigate the cooling effect of throttling compressed natural gas during the pressure regulation process. The concept of using this effect in cooling down the induction air was investigated. A thermodynamic model was developed for a typical fuel delivery system used on a vehicle fueled with compressed natural gas. The model was based on a set of integral conservation laws applied to each component of the fueling system. Several heat exchanging arrangements between the throttled gas and the inlet air were examined. The effect of the added heat exchanger on engine delivery ratio was examined for different engine sizes as well as for different operating conditions. An increase of 1 to 2.5% in engine delivery ratio was predicted due to the added heat exchanger.

SatCon Technology Corporation has completed design, fabrication, and the first round of test of a 373 kW (500 hp), two-spool, intercooled gas turbine engine with integral induction type alternators. This turbine alternator is the prime mover for a World Sports Car class hybrid electric vehicle under development by Chrysler Corporation. The complete hybrid electric vehicle propulsion system features the 373 kW (500 hp) turbine alternator unit, a 373 kW (500 hp) 3.25 kW-h (4.36 hp-h) flywheel, a 559 kW (750 hp) traction motor, and the propulsion system control system. This paper presents and discusses the major attributes of the control system associated with the turbine alternator unit. Also discussed is the role and operational requirements of the turbine alternator unit as part of the complete hybrid electric vehicle propulsion system.

This paper presents a new experimental system to study the L-HCCF of an actual turbine disk mortise teeth at elevated temperature, using an actual disk as experimental component. This system ingeniously achieves combined loading (simulating low cycle radial centrifugal force and high cycle crosswise vibration of blade), high-frequency induction local heating (550°C constant temperature), control of high cycle vibrating frequency and amplitude, and crack real-time detection. The experimental result is identical with the practical flight failure. This method can be easily popularized to study the L-HCCF of many components.

Flow experiments in a single-pass heat exchanger using JP-8 and certain additives were initiated under controlled conditions to explore the effects of a metal surface on deposition. The experimental apparatus permitted a unique viewing of the time evolution of deposits at different axial locations under conditions of limited oxygen availability somewhat similar to those in jet aircraft. Scanning electron microscopy was used to examine deposit microstructure. In addition, x-ray photoelectron spectroscopy and Auger electron spectroscopy determined the chemical composition of the deposits. Oxygen concentration measurements in the bulk flow were also performed, and the observed transient oxidation behavior was related to measured time-dependent changes in the deposit. Increasing dissolved oxygen levels and large changes in deposition were characteristic of the induction time. Mechanisms of fouling in the heated and cooled sections were different. Spectroscopic analysis indicated that deposits formed in the heated section had chemical compositions different from those formed in the cooled section. Scanning electron microscopy revealed differences in microstructure between the heated and cooled sections: More uniform deposits formed in the cooled section as a result of once-soluble species becoming insoluble at low temperatures. In addition, the JP-8 additives significantly reduced fouling in the heated section, but their effectiveness in the cooled section, especially after long periods, was unclear.

Abrasive particles entering an engine because of inadequate air filtration can cause excessive wear, which may lead to premature engine failure. Despite the importance of filtration in engine systems, there is little understanding of the dynamics of the filtration process. Often, limited space is available for an engine air induction system. Therefore, filters are designed in smaller packages, resulting in higher aerosol velocities through the primary filter material. High aerosol velocities may cause dust re-entrainment and increase the amount of dust penetrating the filter. Our experiments with cellulose and synthetic-type filter media show examples of dust reentrainment for fine and coarse dust. Conditions for dust particle re-entrainment are discussed.

In-cylinder charge swirl is used in many internal combustion engines to promote combustion. The purpose of this work is to investigate the in-cylinder swirl characteristics generated by an engine head during the induction process by means of flow visualization and Particle Tracking Velocimetry (PTV). The study was carried out for an engine head with a shrouded intake valve in a special single-cylinder transient water analog. The results revealed that the in-cylinder swirl generated by the shroud is characterized by a strong single vortex with its center of rotation eccentric to the cylinder axis. The location of the center rotation differs from plane to plane along the cylinder axis. Furthermore, velocity data obtained for this study suggest that the in-cylinder swirl is not solid body rotation. Finally, the velocity fields were integrated and an equivalent swirl was calculated for the engine under transient conditions.

An existing multidimensional in-cylinder flow code, KIVA, was modified to calculate gas flow and fuel injection in a simplified (no valve stem and simplified valve-head geometry) engine intake port. A single-cylinder engine simulation program was used to specify the initial and boundary conditions for flow calculations. A previously developed spray model was also used to simulate pressure-atomized spray with isooctane as the fuel. Three cases with increasing degrees of complexity were considered: (1) an impulsively started port flow with both port ends open (the inlet-boundary velocity was changed from zero to a finite value at the start of computation), (2) an impulsively started port flow with one port end partially blocked to simulate gas flow through the valve annulus, and (3) port flow driven by the time-varying gas flow rate through the valve annulus calculated using a single-cylinder engine simulation program. A spray calculation was also made for each case. The calculations indicate that the KIVA code can be modified to conduct computations with complicated port geometries and open flow boundary conditions. The results also indicate that both gas flow and fuel-injection processes and port geometry have a strong influence on the details of fuel induction into the cylinder. This confirms that consideration of both gas flow and fuel-injection processes is necessary in order to understand the mechanisms of fuel-air mixing in an engine intake port employing port fuel injection.

In addition to the frequently used statistical ensemble-average, non-Reynolds filtering operators have long been proposed for nonstationary turbulent quantities. Several techniques for the reduction of velocity data acquired in the cylinder of internal combustion reciprocating engines have been developed by various researchers in order to separate the “mean flow” from the “fluctuating motion,” cycle by cycle, and to analyze small-scale engine turbulence by statistical methods. Therefore a thorough examination of these techniques and a detailed comparison between them would seem to be a preliminary step in attempting a general study of unconventional averaging procedures for reciprocating engine flow application. To that end, in the present work, five different cycle-resolved data reduction methods and the conventional ensemble-average were applied to the same in-cylinder velocity data, so as to review and compare them. One of the methods was developed by the authors. The data were acquired in the cylinder of a direct-injection automotive diesel engine, during induction and compression strokes, using an advanced hot-wire anemometry technique. Correlation and spectral analysis of the engine turbulence, as determined from the data with the different procedures, were also performed.

The computational fluid dynamics simulation program KIVA is augmented with a k-ε turbulence model and enhanced geometric capabilities. It is applied to the case of flow in an inlet port and a combustion chamber with a moving valve in order to investigate the effect of inlet flow on the prevailing aerodynamic conditions in the cylinder. The needed initial and time-varying boundary conditions at the upstream section of the intake port are obtained from a one-dimensional acoustic model of the complete single cylinder engine. The three-dimensional flow domain includes an intake port, a combustion chamber, and a moving valve. An internal dynamic rezoning procedure is presented and incorporated in the flow code, which ensures an adequate I, J, K-structured hexahedral mesh when the boundaries of the computation domain are severely distorted, as is the case with a moving valve. Flow computation is carried out from induction TDC to BDC. The resulting velocity and residual burned gas mass fraction fields are then examined and effects due to the geometry of the port and chamber are discussed.

The influence of the induction system on small-scale turbulence in a high-speed, automotive diesel engine was investigated under variable swirl conditions. The induction system was made up of two equiverse swirl tangential ducts, and valves of the same size and lift. Variable swirl conditions were obtained by keeping one of the inlet valves either closed or functioning, and by changing engine speed. The investigation was carried out for two induction system configurations: with both ducts operating and with only one of them operating. Two different engine speeds were considered, one relatively low (1600 rpm) and the other quite high (3000 rpm), the latter being the highest speed at which engine turbulence has been measured up to now. Cycle-resolved hot-wire anemometry measurements of air velocity were performed throughout the induction and compression strokes, under motored conditions, along a radial direction at an axial level that was virtually in the middle of the combustion chamber at top dead center. The velocity data were analyzed using the nonstationary time-averaging procedure previously developed by the authors. Correlation and spectral analysis of the small-scale turbulence so determined was also performed. The turbulence intensity and its degree of nonhomogeneity and anisotropy were sensibly influenced by the variable swirl conditions, depending on both the intake system configuration and engine speed; they generally showed an increase with increasing swirl intensity, at the end of the compression stroke. A similar trend was observed in the cyclic fluctuation of both the mean velocity and turbulence intensity. The micro time scale of turbulence was found to be almost uniform during induction and compression, showing a slight dependence on the measurement point and on the intake system configuration, but a more sensible dependence on the engine speed. No effect of the cylinder wall on turbulence was apparent.

A comparison of the accuracy of several techniques recently developed for solving stiff differential equations is presented. The techniques examined include two general-purpose codes EPISODE and LSODE developed for an arbitrary system of ordinary differential equations, and three specialized codes CHEMEQ, CREK1D, and GCKP84 developed specifically to solve chemical kinetic rate equations. The accuracy comparisons are made by applying these solution procedures to two practical combustion kinetics problems. Both problems describe adiabatic, homogeneous, gas-phase chemical reactions at constant pressure, and include all three combustion regimes: induction, heat release, and equilibration. The comparisons show that LSODE is the most efficient code—in the sense that it requires the least computational work to attain a specified accuracy level—currently available for chemical kinetic rate equations. An important finding is that an iterative solution of the algebraic enthalpy conservation equation for the temperature can be more accurate and efficient than computing the temperature by integrating its time derivative.

Due to the increasing price of fuel, demands for fuel economy of heavy-duty trucks become severer year by year, and many efforts, such as reduction of air drag of vehicle, optimization of transmission and engine performance, improvement of engine combustion, etc., have been taken to meet these demands. However, requirements for the reduction of fuel consumption are expected to become even more critical, so the authors have studied a new design concept for heavy duty truck diesel engines to satisfy these requirements. The basic idea for getting a fuel-economic engine is to make the engine as small as possible and also to apply higher boost turbocharging for obtaining a sufficiently high output. However, measures to improve the undesirable problems which conventional turbocharged engines possess, such as lack of acceleration response and low-speed torque, increase of thermal and mechanical loads, shortage of engine brake torque, poor cold start ability, etc., should also be pursued. A chassis-mounted air-to-air intercooler, inertia-charged air induction system, highly backward-curved impeller of turbocharger, electronically controlled fuel injection timing device, etc., have been applied. And a new design technique as well as new material and construction have also been applied. This engine was installed to a long-haul truck with a gross weight of around 20,000 kg (44,000 lbs) and got better fuel mileage, as expected.

When the incoming air flow to a supersonic compressor rotor or cascade has a subsonic axial velocity component, a system of shock and Mach waves originates in the blade leading-edge region, propagates upstream of successive blades, and alters the incident flow conditions. The continuity constraint establishes a unique relationship between the incident Mach number and air flow angle. The shocks are detached and curved with blunt leading edged blades thereby violating the assumptions inherent in the classical simple wave analysis of this flow induction process. The current work employs detached shock models and a rotational flow analysis by the method of characteristics to investigate the effects of airfoil leading edge radius and cascade solidity on the unique incidence values and entrance region total pressure losses. The calculated results are compared to simple wave theory for the entrance region and it is shown that the simple wave assumptions lead to appreciable errors when detached shocks are present in the flow field.