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Today’s power engineer needs to be able to work in a multi-disciplinary environment and this presentation provides an overview of the challenges faced by today’s power engineers and sets forth skills most needed in this environment.
Emission characteristics of a three-cup P and W Axially Controlled Stoichiometry (ACS) sector combustor are reported in this article. Multiple injection points and fuel staging strategies are used in this combustor design. Pilot-stage injectors are located on the front dome plate of the combustor, and main-stage injectors are positioned on the top and bottom of the combustor liners downstream. Low power configuration uses only pilot-stage injectors. Main-stage injectors are added to high power configuration to help distribute fuel more evenly and achieve overall lean burn yielding very low NOx emissions. Combustion efficiencies at four ICAO LTO conditions were all above 99%. Three EINOx emissions correlation equations were developed based on the experimental data to describe the NOx emission trends of this combustor concept. For the 7% and 30% engine power conditions, NOx emissions are obtained with the low power configuration, and the EINOx values are 6.16 and 6.81. The high power configuration was used to assess 85% and 100% engine power NOx emissions, with measured EINOx values of 4.58 and 7.45, respectively. The overall landing-takeoff cycle NOx emissions are about 12% relative to ICAO CAEP/6 level.
Proteins are the molecular machines of life with numerous applications in energy, health, and sustainability. However, engineering proteins with desired functions for practical applications remains slow, expensive, and specialist-dependent. Here we report a generally applicable platform for autonomous enzyme engineering that integrates machine learning and large language models with biofoundry automation to eliminate the need for human intervention, judgement, and domain expertise. Requiring only an input protein sequence and a quantifiable way to measure fitness, this automated platform can be applied to engineer a wide array of proteins. As a proof of concept, we engineer Arabidopsis thaliana halide methyltransferase (AtHMT) for a 90-foldimprovement in substrate preference and 16-fold improvement in ethyl-transferase activity, along with developing a Yersinia mollaretii phytase (YmPhytase) variant with 26-fold improvement in activity at neutral pH. This is accomplished in four rounds over 4 weeks, while requiring construction and characterization of fewer than 500 variants for each enzyme. This platform for autonomous experimentation paves the way for rapid advancements across diverse industries, from medicine and biotechnology to renewable energy and sustainable chemistry.
We present an extensive study of the inception of supernova explosions by following the evolution of the cores of two massive stars (15 and 25 Solar mass) in multidimension. Our calculations begin at the onset of core collapse and stop several hundred milliseconds after the bounce, at which time successful explosions of the appropriate magnitude have been obtained. Similar to the classical delayed explosion mechanism of Wilson, the explosion is powered by the heating of the envelope due to neutrinos emitted by the protoneutron star as it radiates the gravitational energy liberated by the collapse. However, as was shown by Herant, Benz, & Colgate, this heating generates strong convection outside the neutrinosphere, which we demonstrate to be critical to the explosion. By breaking a purely stratified hydrostatic equilibrium, convection moves the nascent supernova away from a delicate radiative equilibrium between neutrino emission and absorption, Thus, unlike what has been observed in one-dimensional calculations, explosions are rendered quite insensitive to the details of the physical input parameters such as neutrino cross sections or nuclear equation of state parameters. As a confirmation, our comparative one-dimensional calculations with identical microphysics, but in which convection cannot occur, lead to dramatic failures. Guided by our numerical results, we have developed a paradigm for the supernova explosion mechanism. We view a supernova as an open cycle thermodynamic engine in which a reservoir of low-entropy matter (the envelope) is thermally coupled and physically connected to a hot bath (the protoneutron star) by a neutrino flux, and by hydrodynamic instabilities. This paradigm does not invoke new or modified physics over previous treatments, but relies on compellingly straightforward thermodynamic arguments. It provides a robust and self-regulated explosion mechanism to power supernovae that is effective under a wide range of physical parameters.
Lean Direct Injection (LDI) is a combustor concept that reduces nitrogen oxides (NOx) emissions.This paper looks at a 3-zone multipoint LDI concept developed by Parker Hannifin Corporation. The concept was tested in a flame-tube test facility at NASA Glenn Research Center. Due to test facility limitations, such as inlet air temperature and pressure, the flame-tube test was not able to cover the full set of engine operation conditions. Three NOx correlation equations were developed based on assessing NOx emissions dependencies on inlet air pressure (P3), inlet air temperature (T3), and fuel air equivalence ratio(theta) to estimate the NOx emissions at the unreachable high engine power conditions. As the results, the NOx emissions are found to be a strong function of combustion inlet air temperature and fuel air equivalence ratio but a weaker function of inlet air pressure. With these three equations, the NOx emissions performance of this injector concept is calculated as a 66 reduction relative to the ICAO CAEP-6 standard using a 55:1 pressure-ratio engine cycle. Uncertainty in the NOx emissions estimation increases as the extrapolation range departs from the experimental conditions. Since maximum inlet air pressure tested was less than 50 of the full power engine inlet air pressure, a future experiment at higher inlet air pressure conditions is needed to confirm the NOx emissions dependency on inlet air pressure.
Lean Direct Injection (LDI) is a combustor concept that reduces nitrogen oxides (NOx) emissions. This paper looks at a 3-zone multipoint LDI concept developed by Parker Hannifin Corporation. The concept was tested in a flame-tube test facility at NASA Glenn Research Center. Due to test facility limitations, such as inlet air temperature and pressure, the flame-tube test was not able to cover the full set of engine operation conditions. Three NOx correlation equations were developed based on assessing NOx emissions dependencies on inlet air pressure (P3), inlet air temperature (T3), and fuel air equivalence ratio (Ф) to estimate the NOx emissions at the unreachable high engine power conditions. As the results, the NOx emissions are found to be a strong function of combustion inlet air temperature and fuel air equivalence ratio but a weaker function of inlet air pressure. With these three equations, the NOx emissions performance of this injector concept is calculated as a 66% reduction relative to the ICAO CAEP-6 standard using a 55:1 pressure-ratio engine cycle. Uncertainty in the NOx emissions estimation increases as the extrapolation range departs from the experimental conditions. Since maximum inlet air pressure tested was less than 50% of the full power engine inlet air pressure, a future experiment at higher inlet air pressure conditions is needed to confirm the NOx emissions dependency on inlet air pressure.
Lean Direct Injection (LDI) is a combustor concept that reduces nitrogen oxides (NOx) emissions. This paper looks at a 3-zone multipoint LDI concept developed by Parker Hannifin Corporation. The concept was tested in a flame-tube test facility at NASA Glenn Research Center. Due to test facility limitations, such as inlet air temperature and pressure, the flame-tube test was not able to cover the full set of engine operation conditions. Three NOx correlation equations were developed based on assessing NOx emissions dependencies on inlet air pressure (P3), inlet air temperature (T3), and fuel air equivalence ratio (Ф) to estimate the NOx emissions at the unreachable high engine power conditions. As the results, the NOx emissions are found to be a strong function of combustion inlet air temperature and fuel air equivalence ratio but a weaker function of inlet air pressure. With these three equations, the NOx emissions performance of this injector concept is calculated as a 66 percent reduction relative to the ICAO CAEP-6 standard using a 55:1 pressure-ratio engine cycle. Uncertainty in the NOx emissions estimation increases as the extrapolation range departs from the experimental conditions. Since maximum inlet air pressure tested was less than 50 percent of the full power engine inlet air pressure, a future experiment at higher inlet air pressure conditions is needed to confirm the NOx emissions dependency on inlet air pressure.
Lean Direct Injection (LDI) is a combustor concept that reduces nitrogen oxides (NOx) emissions. This paper looks at a 3-zone multipoint LDI concept developed by Parker Hannifin Corporation. The concept was tested in a flame-tube test facility at NASA Glenn Research Center. Due to test facility limitations, such as inlet air temperature and pressure, the flame-tube test was not able to cover the full set of engine operation conditions. Three NOx correlation equations were developed based on assessing NOx emissions dependencies on inlet air pressure (P3), inlet air temperature (T3), and fuel air equivalence ratio (phi) to estimate the NOx emissions at the unreachable high engine power conditions. As the results, the NOx emissions are found to be a strong function of combustion inlet air temperature and fuel air equivalence ratio but a weaker function of inlet air pressure. With these three equations, the NOx emissions performance of this injector concept is calculated as a 66 percent reduction relative to the ICAO CAEP-6 standard using a 55:1 pressure-ratio engine cycle. Uncertainty in the NOx emissions estimation increases as the extrapolation range departs from the experimental conditions. Since maximum inlet air pressure tested was less than 50 percent of the full power engine inlet air pressure, a future experiment at higher inlet air pressure conditions is needed to confirm the NOx emissions dependency on inlet air pressure.
This paper presents results from tests in a flame tube facility, where a bio-derived alternate fuel was compared with JP-8 for emissions and general combustion performance. A research version of General Electric Aviation (GE) TAPS injector was used for the tests. Results include combustion efficiency from gaseous emission measurements, 2D planar laser-based imaging as well as basic flow visualization of the flame. Four inlet test conditions were selected that simulate various engine power conditions relevant to NASA Fundamental Aeronautics Supersonics Project and Environmentally Responsible Aviation Program. One inlet condition was a pilot-only test point. The other three inlet conditions incorporated fuel staging via a split between the pilot and main circuits of either 10%/90% or 20%/80%. For each engine power condition, three fuel mixes were used: 100% JP-8; 100% alternative; and a blend of the two, containing 75% alternative. Results for the inlet cases that have fuel split between pilot and main, indicate that fuel from the pilot appears to be evaporated by the time it reaches the dome exit. Main circuit liquid evaporates within a downstream distance equal to annulus height, no matter the fuel. Some fuel fluorescence images for a 10%/90% fuel staging case show a distinct difference between JP-8 and bio-derived fuel. OH PLIF results indicate that OH forms in a region more centrally-located for the JP-8 case downstream of the pilot, in its central recirculation region (CRZ). For the bio-derived Hydrotreated Renewable Jet (HRJ) fuel, however, we do not see much OH in the CRZ. The OH image structure near the dome exit is similar for the two fuels, but farther downstream the OH in the CRZ is much more apparent for the JP-8 than for the alternate fuel. For all conditions, there was no discernable difference between fuel types in combustion efficiency or emissions.
Aerodynamic stability is a fundamental limit in the compressor design process. The development of robust techniques for increasing stability has several benefits: enabling higher loading and fewer blades, increasing safety throughout a mission, increasing tolerance to stage mismatch during part-speed operation and speed transients, and providing an opportunity to match stages at the compressor maximum efficiency point, thus reducing fuel burn. Mass injection upstream of the tip of a high-speed axial compressor rotor is a stability enhancement approach known to be effective in suppressing stall in tip-critical rotors if the injection is activated before stall occurs. This approach to stall suppression requires that a reliable stall warning system be available. Tests have recently been performed to assess whether steady injection can also be used to recover from fully developed stall. If mass injection is effective in recovering from stall quickly enough to avoid structural damage or loss of engine power, then a stall warning system may not be required. The stall recovery tests were performed on a transonic compressor rotor at its design tip speed of 1475 ft/sec using four injectors evenly spaced around the compressor case upstream of the rotor. The injectors were connected to an external air source. In an actual engine application, the injected air would be supplied with compressor bleed air. The injectors were isolated from the air source by a fast-acting butterfly valve. With the injectors turned off, the compressor was throttled into stall. Air injection was then activated with no change in throttle setting by opening the butterfly valve. The compressor recovered from stall at a fixed throttle setting with the aid of tip injection. The unsteady operating characteristic of the rotor was measured during these tests using high-response pressure sensors located upstream and downstream of the rotor. The figure shows the results, where the unsteady pressure and mass flow are superimposed on the steady operating characteristic. The total injected mass flow was equal to 1.3 percent of the compressor flow. The solid line with no solid squares on it denotes the operating point during the beginning of throttle closure and the initial drop into stall. The gray traces denote the operating point during an additional throttle closure that occurred over the next 1200 rotor revolutions (4 sec). The dashed line denotes the recovery from stall that occurred during 90 rotor revolutions (0.3 sec) after the injectors were activated with no change in throttle setting. Tip injection not only recovers the compressor from stall, but also restores the compressor to its pre-stall level of pressure rise. In contrast, standard stall recovery schemes such as compressor bleed, stator vane actuation, or engine throttle modulation result in a loss of pressure rise across the compressor, which results in a loss of engine power.
Hydrogen fuel cell-powered off-road vehicles can replace hydrocarbon-powered off-road vehicles to reduce carbon dioxide and criteria pollutant emissions in the agriculture, construction, and mining industries. Vehicle manufacturers and customers recognize health and environmental benefits of emissions reductions but are ultimately compelled by the total cost of ownership of their vehicles. In this study, we conduct a technoeconomic evaluation for three hallmark off-road vehicles, tractors, wheel loaders, and excavators, comparing vehicles with hydrogen fuel cell + battery hybrid powertrains to traditional diesel powertrains. Stakeholder-valued performance metrics include fuel cell engine power, engine durability, hydrogen consumption rate, hydrogen storage system volume, and energy-regenerative drivetrain efficiency. The total cost of ownership includes capital, operating and maintenance, fuel, and fuel storage costs. State-of-the-art fuel cell powered wheel loaders and excavators are currently cost competitive with diesel platforms. If targeted improvements to cost, performance, and durability improvements of fuel cell stacks and storage systems are achieved, fuel cell systems would be cost competitive for tractors and significantly lower total cost of ownership options for wheel loaders and excavators.
An investigation was conducted to determine the effects of three design modifications of the original NACA injection impeller on the performance of an R-3350 engine. Different methods of injecting the fuel into the impeller air stream were studied and evaluated from the individual cylinder fuel-air ratios and the resulting cylinder temperatures. Each impeller was tested for a range of engine powers normally used in flight operation. The relatively simple design of the original injection impeller produced approximately the same mixture- and temperature-distribution characteristics as the modified impellers of more complex design. None of the modifications appreciably affected the manifold pressure, the combustion-air flow, nor the throttle angle required to maintain a given engine power,
A flight investigation was undertaken to determine the effect of a fully controllable thrust reverser on the flight characteristics of a single-engine jet airplane. Tests were made using a cylindrical target-type reverser actuated by a hydraulic cylinder through a "beep-type" cockpit control mounted at the base of the throttle. The thrust reverser was evaluated as an in-flight decelerating device, as a flight path control and airspeed control in landing approach, and as a braking device during the ground roll. Full deflection of the reverser for one reverser configuration resulted in a reverse thrust ratio of as much as 85 percent, which at maximum engine power corresponded to a reversed thrust of 5100 pounds. Use of the reverser in landing approach made possible a wide selection of approach angles, a large reduction in approach speed at steep approach angles, improved control of flight path angle, and more accuracy in hitting a given touchdown point. The use of the reverser as a speed brake at lower airspeeds was compromised by a longitudinal trim change. At the lower airspeeds and higher engine powers there was insufficient elevator power to overcome the nose-down trim change at full reverser deflection.
The take-off distances over a 35-foot obstacle have been determined for a supersonic transport configuration characterized by a low maximum lift coefficient at a high angle of attack and by high drag due to lift. These distances were determined analytically by means of an electronic digital computer. The effects of rotation speed, rotation angle, and rotation time were determined. A few configuration changes were made to determine the effects of thrust-weight ratio, wing loading, maximum lift coefficient, and induced drag on the take-off distance. The required runway lengths based on Special Civil Air Regulation No. SR-422B were determined for various values of rotation speed and compared with those based on full engine power. Increasing or decreasing the rotation speed as much as 5 knots from the value at which the minimum take-off distance occurred increased the distance only slightly more than 1 percent for the configuration studied. Under-rotation by 1 deg to 1.5 deg increased the take-off distance by 9 to 15 percent. Increasing the time required for rotation from 3 to 5 seconds had a rather small effect on the take-off distance when the values of rotation speed were near the values which result in the shortest take-off distance. When the runway length is based on full engine power rather than on SR-422B, the rotation speed which results in the shortest required runway length is 10 knots lower and the runway length is 4.3 percent less.
We presented results from the SASS Near-Field Interactions Flight (SNIF-III) Experiment which was conducted during May and June 1997 in collaboration with the Vermont and New Jersey Air National Guard Units. The project objectives were to quantify the fraction of fuel sulfur converted to S(VI) species by jet engines and to gain a better understanding of particle formation and growth processes within aircraft wakes. Size and volatility segregated aerosol measurements along with sulfur species measurements were recorded in the exhaust of F-16 aircraft equipped with F-100 engines burning fuels with a range of fuel S concentrations at different altitudes and engine power settings. A total of 10 missions were flown in which F-16 exhaust plumes were sampled by an instrumented T-39 Sabreliner aircraft. On six of the flights, measurements were obtained behind the same two aircraft, one burning standard JP-8 fuel and the other either approximately 28 ppm or 1100 ppm S fuel or an equal mixture of the two (approximately 560 ppm S). A pair of flights was conducted for each fuel mixture, one at 30,000 ft altitude and the other starting at 35,000 ft and climbing to higher altitudes if contrail conditions were not encountered at the initial flight level. In each flight, the F-16s were operated at two power settings, approx. 80% and full military power. Exhaust emissions were sampled behind both aircraft at each flight level, power setting, and fuel S concentration at an initial aircraft separation of 30 m, gradually widening to about 3 km. Analyses of the aerosol data in the cases where fuel S was varied suggest results were consistent with observations from project SUCCESS, i.e., a significant fraction of the fuel S was oxidized to form S(VI) species and volatile particle emission indices (EIs) in comparably aged plumes exhibited a nonlinear dependence upon the fuel S concentration. For the high sulfur fuel, volatile particle EIs in 10-second-old-plumes were 2 to 3 x 10 (exp 17) / kg of fuel burned and exhibited no obvious trend with engine power setting or flight altitude. In contrast, about 8-fold fewer particles were observed in similarly aged plumes from the same aircraft burning fuel with 560 ppm S content and EIs of 1 x 10(exp 15)/ kg of fuel burned were observed in the 28 ppm S fuel case. Moreover, data recorded as a function of plume age indicates that formation and growth of the volatile particles proceeds more slowly as the fuel S level is reduced. For example, ultrafine particle concentrations appear to stabilize within 5 seconds after emission in the 1100 ppm S cases but are still increasing in 20-second old plumes produced from burning the 560 ppm S fuel.
We demonstrate the existence of universal features in the finite-time thermodynamics of quantum machines by considering a many-body quantum Otto cycle in which the working medium is driven across quantum critical points during the unitary strokes. Specifically, we consider a quantum engine powered by dissipative energizing and relaxing baths. We show that under very generic conditions, the output work is governed by the Kibble-Zurek mechanism; i.e., it exhibits a universal power-law scaling with the driving speed through the critical points. We also optimize the finite-time thermodynamics as a function of the driving speed. The maximum power and the corresponding efficiency take a universal form, and are reached for an optimal speed that is governed by the critical exponents. We exemplify our results by considering a transverse-field Ising spin chain as the working medium. For this model, we also show how the efficiency and power vary as the engine becomes critical.
The use of blended fuel sources in land based gas turbine engines drives variations in the resulting operational profile (temperatures and pressures) which can impact engine reliability. Furthermore, variability in the manufacture of components affects the resulting microstructure which directly impacts material performance and reliability. Currently, data-driven models are typically used for maintaining and inspecting fleets of engines. Without explicitly capturing material and operational sources of variability conservatism must be used in developing component-level reliability models. Therefore, there exists an opportunity to use information from materials-scale physics models to better inform reliability modeling and reduce conservatism; the impact is more cost-efficient operation and maintenance of current and future fleets. Specifically, this work establishes a computational framework for evaluating the probabilistic high temperature creep performance of hot-section Ni-based superalloys where uncertainty comes from both microstructural and operational variability. A novel high-fidelity physics model which phenomenologically captures grain-boundary sensitive phenomena has been established. A probabilistic calibration procedure was used to calibrate the model and capture uncertainty in the parameterized model coefficients. A design of experiments methodology was established for identifying informative microstructural digital representations for suitable for forward model evaluation. Results show that training a machine-learning surrogate using this design criteria outperforms random selection of microstructural representations. Finally, two surrogate models were developed: (1) a deterministic surrogate model which predicts the local field response given microstructure, constitutive model parameters, and operating conditions (stress, temperature) and (2) a probabilistic model, where uncertainty comes from constitutive law uncertainty, built using denoising diffusion probabilistic models which samples responses given (1) microstructure and (2) operating conditions. These surrogate models enable partner Siemens Energy to rapidly perform UQ analysis specific to creep deformation across a range of microstructures and operating conditions. The impact is that these ML and physics codes can be used to establish more advanced reliability models for the inspection, servicing, and maintenance of land based gas turbine engines.
Program to modify hypergolic propellant spacecraft power unit to operate on gaseous hydrogen and oxygen