Engine Size Research Articles

Global Efficiency of Heat Engines and Heat Pumps with Non-Linear Boundary Conditions

Analysis of global energy efficiency of thermal systems is of practical importance for a number of reasons. Cycles and processes used in thermal systems exist in very different configurations, making comparison difficult if specific models are required to analyze specific thermal systems. Thermal systems with small temperature differences between a hot side and a cold side also suffer from difficulties due to heat transfer pinch point effects. Such pinch points are consequences of thermal systems design and must therefore be integrated in the global evaluation. In optimizing thermal systems, detailed entropy generation analysis is suitable to identify performance losses caused by cycle components. In plant analysis, a similar logic applies with the difference that the thermal system is then only a component, often industrially standardized. This article presents how a thermodynamic “black box” method for defining and comparing thermal efficiency of different size and types of heat engines can be extended to also compare heat pumps of different apparent magnitude and type. Impact of a non-linear boundary condition on reversible thermal efficiency is exemplified and a correlation of average real heat engine efficiencies is discussed in the light of linear and non-linear boundary conditions.

Improvement in the estimation and back-extrapolation of CO2 emissions from the Irish road transport sector using a bottom-up data modelling approach

Road transport is a major source of CO2 emissions in Ireland and accounts for almost 96% of the total CO2 emissions from the transport sector. Following the recent adopted UNFCCC reporting guidelines on annual inventories [24/CP.19], this study applied the 2006 IPCC Guidelines for National Greenhouse Gas Inventories (2006 IPCC GLs) tier 3 approach to estimate CO2 emissions from road transport at the vehicle category level, for the first time in Ireland. For this, disaggregated datasets were prepared based on year of vehicle registration and mileage since registration of the vehicle. Such an approach provided a more realistic national scenario in comparison to the use of average mileage degradation in emission calculations. This investigation comprised a recalculation of previous emissions estimates (1990–2012) and an estimation of CO2 emissions in 2013 using a previously unavailable level of data disaggregation for vehicle mileage as well as using vehicle class specific data and an improved bottom-up estimation methodology in COPERT. Historic vehicle fleet data were restructured, annual mileage data were estimated in relation to the fleet data and back extrapolated using a regression approach.The results showed that the mileage degradation was not only subject to fuel technology, engine size, and age but also the emissions class and vehicle category. It was also observed that the disaggregated level of data provided a different CO2 emissions split among the vehicle categories than that of previous estimations which were based on an aggregated level of data. Previous emissions inventories (1990–2012) were shown to have underestimated the share from diesel fuelled passenger cars by more than 56% in 2012. Diesel fuelled passenger cars were also found to account for the majority of CO2 emissions from road transport activities in Ireland in 2013. The level and trend assessment showed that emissions from Euro-II and Euro-III classed vehicles especially for passenger cars, which have a significant contribution to the total emission in 2013 have caused an increase in fleet level emissions in Ireland. In addition, the results also showed that the emissions share from Light Duty Vehicles and Heavy Duty Vehicles were overestimated by previous investigations. This paper highlights the importance of the resolution of data used in emissions inventory preparation which may impact upon future projections and policy formulation. The findings of this investigation are also discussed in relation their implications for road transport policy, including carbon taxation and future policy options aimed at achieving EU emissions target in 2020.

Gene Delivery Particle Engineering Strategies for Shape-dependent Targeting of Cells and Tissues.

Successful gene delivery requires overcoming both systemic and intracellular obstacles before the nucleic acid cargo can successfully reach its tissue and subcellular target location. Materials & Methods: Non-viral mechanisms to enable targeting while avoiding off-target delivery have arisen via biological, chemical, and physical engineering strategies. Herein we will discuss the physical parameters in particle design that promote tissue- and cell-targeted delivery of genetic cargo. We will discuss systemic concerns, such as circulation, tissue localization, and clearance, as well as cell-scale obstacles, such as cellular uptake and nucleic acid packaging. In particular, we will focus on engineering particle shape and size in order to enhance delivery and promote precise targeting. We will also address methods to program or change particle shape in situ using environmentally triggered cues.

Sizing implications of a regional aircraft for inner-city operations

PurposeThe paper aims to assess the potential of aircraft operation from city centres to achieve shortened travel times and the involved aircraft design process.Design/methodology/approachThe paper describes the methodical approach and iterative procedure of the design process. An assessment of potential technologies is conducted to provide the required enhancements to fulfil the constraints following an inner-city operation. Operational procedures were analysed to reduce the noise propagation through flight path optimization. Furthermore, a ground-based assisted take-off system was conceived to lower required take-off field length and to prevent engine sizing just for the take-off case. Cabin design optimization for a fast turnaround has been conducted to ensure a wide utilization spectrum. The results prove the feasibility of an aircraft developed for inner city operation.FindingsA detailed concept for a 60-passenger single aisle aircraft is proposed for an Entry-Into-Service year 2040 with a design range of 1,500 nautical miles for a load factor of 90 per cent. Although the design for Short Take-off and Landing and low noise operation had to be traded partly with cruise efficiency, a noteworthy reduction in fuel burn per passenger and nautical mile could be achieved against current aircraft.Practical implicationsThe findings will contribute to the evaluation of the feasibility and impact of the Flightpath 2050 goal of a 4-h door-to-door by providing a feasible but ambitious example. Furthermore, it highlights possible bottlenecks and problems faced when realizing this goal.Originality/valueThe paper draws its value from the consideration of the overall sizing effects at aircraft level and from a holistic view on an inner-city airport/aircraft concept design for a 4-h door-to-door goal.

Energy-Based Design of Powertrain for a Re-Engineered Post-Transmission Hybrid Electric Vehicle

This paper presents a systematic approach for the design of post-transmission hybrid electric vehicle powertrains, as an instrument aiding the designer in making the right decision. In particular, a post-transmission series/parallel hybrid electric powertrain is considered, and all of the possible energy paths are taken into account, in order to automatically select the configuration that gives the lowest fuel consumption, thus better fitting to the considered mission. The optimization problem is solved with the Dijkstra algorithm, which is more computationally efficient than other optimization algorithms in the case of massive design spaces. In this way, it is possible to design a vehicle in terms of architecture and component sizes, without making any a priori choices, which are usually based on common sense, likely compromising the overall system efficiency. In order to demonstrate the effectiveness of the methodology, different driving cycles have been simulated, and some results are presented. The methodology is particularly applied to re-engineered vehicles, aimed at maximizing the benefits of the vehicle hybridization process. Results show how the introduction, in the optimization algorithm, of the engine load factor and sharing factor, for the engine torque split between the generator and the wheels, is crucial. For example, a 10% reduction of the original engine size, suggested by a low load factor, is able to allow for a 24% reduction in the fuel consumption. On the other hand, the sharing factor is of particular importance in suggesting if the vehicle architecture should be series, parallel or rather combined.

Convex Modeling and Optimization of a Vehicle Powertrain Equipped With a Generator–Turbine Throttle Unit

This paper investigates an internal combustion (gasoline) engine throttled by a generator-turbine unit. Apart from throttling, the purpose of this device is to complement the operation of a conventional car alternator and support its downsizing by introducing an additional source of energy for the electric auxiliaries. Its energy recovery potential is examined by employing a novel, convex approach to modeling and optimization of the resulting vehicle powertrain. For a given gear-shifting strategy, the proposed method allows the computation of optimal control trajectories, e.g., the optimal engine fuel, alternator, and turbine power, as well as of optimal design parameters, i.e., the optimal battery, alternator and turbogenerator size. The conducted numerical case study shows that a generator-turbine throttle unit has a potential to reduce the total operational (fuel) and component (battery, alternator, and turbogenerator) costs by typically 2%–6%, depending on factors such as the engine size and the choice of a driving cycle.

Thermal Design of Linear Induction and Synchronous Motors for Electromagnetic Launch of Civil Aircraft

The engine size of modern passenger transport aircraft is principally determined by take-off conditions, since initial acceleration requires maximum engine power. An electromagnetic launch (EML) system could provide some or all of the energy required at takeoff so that the aircraft engine power requirement and fuel consumption may be significantly reduced. So far, EML for aircraft has been adopted only for military applications to replace steam catapults on the deck of aircraft carriers. This paper will describe the potential application of EML to propel civil aircraft on the runways of modern airports. A comparison of synchronous and asynchronous electrical motor systems designed to launch an A320-200 sized aircraft is presented. The paper also describes a solution of the transient heat transfer problem applied to the conductive components of EML systems.

The Gathering of the Storm: Risks and Uncertainties in Global Warming

It is often mentioned that solar energy is becoming competitive and that modern renewables is more and more utilized. However, at the same no one speaks of the immense augmentation of air transportation and the construction of new giant infra structure facilities, for instance airports. Moreover, the number of cars increases as well as their engine size. The risk of policy failures and implementation gaps are great for the COP21 project, where one major nation already has reneged.

The choice of universal measuring instruments for monitoring the cylinder liners of the engine during selective assembly

The issues of ensuring the quality of single and small-scale machine-building production, including machine repairs, are currently relevant due to a number of objective and subjective factors that are related to the culture of designing and manufacturing machines. The purpose of the research is to study the influence of the measurement error on the formation of the scattering of the cylinder liner sizes of the YaMZ engine during selective assembly, taking into account the number of incorrectly received and incorrectly rejected parts, as well as determining the probabilistic value of the output of the measured parameter for each tolerance limit for incorrectly accepted products. The choice of measuring instruments to ensure the necessary accuracy is a complex task and should be carried out in accordance with the requirements of GOST 8.051-81 and RD 50-98-86. To analyze the formation of the size distribution in the process of selective assembly of the cylinder liners of YaMZ engines, the indicator gauges were selected with a value of 0,001 mm, the first was adjusted for the end measures of class 1 (error of 6.5 micrometers), and the second was tuned to the mounting rings ). An analysis of the data obtained on the scattering of dimensions indicates that the process of processing the liner can be considered unsatisfactory, since there is a correctable defective products of 4 % and an unrecoverable defective products of 2 %, the scattering zone is shifted toward corrected defective products, which characterizes the good qualifications of the workers performing this operation. When using a caliper with an accuracy of 6,5 micrometers number incorrectly, or out-of band defective parts on more than 4,95 %, and the number of incorrectly received parts of 4,7 % more than when using a caliper with an accuracy of 4 micrometers. Thus, when choosing a measuring instrument to control the quality of the cylinder liners of YaMZ engines under the conditions of a single, small-scale and repair production, the most precise one should be used from the proposed nomenclature of universal measuring instruments of linear dimensions, with a sampling unit 0,001 mm in value for setting rings. This will lead to a significant decrease in the number of incorrectly accepted groups and incorrectly left from the group or rejected parts, which in turn will affect not only the quality of the subsequent assembly of the connection, but also the economy of the enterprise.

Multivariate and conditioned statistics of velocity and wall pressure fluctuations induced by a jet interacting with a flat plate

The increasing size of aircraft engines is leading to reconsideration of their conventional integration in the under-wing configuration due to the strong interaction between the jet and the airframe components. As a consequence, more insight is needed into the complex mechanisms underlying the interaction phenomenon between the jet flow and a surface. The objective of this paper is to carry out a series of experimental tests on a simplified laboratory-scale model to approach/deepen the problem. This analysis is the continuation of a previous study (Di Marco et al., J. Fluid Mech., vol. 770, 2015, pp. 247–272) on a rigid flat plate installed tangentially to the axis of an incompressible jet. In the present work, the velocity and wall pressure fields were simultaneously measured for different radial distances of the plate from the nozzle axis. Pointwise hot-wire anemometer measurements were carried out to characterize the effect of the plate on the velocity field statistics up to the fourth-order moment. The analysis revealed that the presence of the plate brings about a deflection of the mean aerodynamic field over the surface and a reduction of the turbulence intensity. Wall pressure fluctuations induced by the jet flow over the plate were measured by a linear array of cavity-mounted microphones placed along the streamwise direction. The velocity/pressure cross-statistics are achieved in the time and frequency domains using cross-correlations and Fourier analysis. A wavelet-based conditional sampling procedure is applied as well to characterize the flow signatures related to the velocity and wall pressure fluctuations, revealing that the surface induces the breakdown of the large-scale turbulent structures. The dependence of the multivariate and conditioned statistics on the plate distance from the jet as well as on the streamwise and crosswise probe positions is extensively discussed. Different organized flow motions over the surface are found based on the wall pressure events detected. A scaling criterion for velocity signatures is also presented addressing the governing parameters of the jet–plate interaction phenomenon.

Flow Evolution Through a Turning Midturbine Frame with Embedded Design

The paper discusses the time-averaged flow of a new-concept turbine transition duct placed in a two-stage counter-rotating test turbine. As a possible architecture for the turbine transition duct of future engines, the structural vanes carrying the bearing loadings can be integrated with the first low-pressure vane row in one aerodynamically optimized wide-chord vane called the turning midturbine frame. To increase the flow uniformity and to decrease the unsteady content of the flow, a baseline turning midturbine frame is redesigned by embedding two splitter vanes into the strut passage. The discussion on the flowfield is based on numerical results obtained by computational fluid dynamics and validated by aerodynamic measurements. In particular, the splitters are seen playing a major role in suppressing the big structures generated by the struts and the secondary flows of the high-pressure turbine. On the other hand, new losses are introduced by the splitters. Such structures play a decisive role in the overall component performance; therefore, their effect should be properly understood. This work provides a deep insight into the flow physics of an embedded turning midturbine frame for next-generation aeroengines, which is seen as a promising architecture in order to compact the engine size while keeping component performance high. The present work can be considered as a first attempt to implement splitter blades into an already existing turning midturbine frame design, and its value lies in a thorough experimental and computational study on the losses and benefits of such a design.

Aerodynamic Effects of Propulsion Integration for High Bypass Ratio Engines

This work describes the assessment of the effect of engine installation parameters such as engine position, size, and power setting on the performance of a typical 300-seater aircraft at cruise condition. Two engines with very high bypass ratio and with different fan diameters and specific thrusts are initially simulated in isolation to determine the thrust and drag forces for an isolated configuration. The two engines are then assessed in an engine–airframe configuration to determine the sensitivity of the overall installation penalty to the vertical and axial engine location. The breakdown of the interference force is investigated to determine the aerodynamic origins of beneficial or penalizing forces. To complete the cruise study, a range of engine power settings is considered to determine the installation penalty at different phases of cruise. This work concludes with the preliminary assessment of cruise fuel burn for two engines. For the baseline engine, across the range of installed positions, the resultant thrust requirement varies by 1.7% of standard net thrust. The larger engine is less sensitive with a variation of 1.3%. For an assessment over a 10,000 km cruise flight, the overall effect of the lower specific thrust engine shows that the cycle benefits of in specific fuel consumption are supplemented by a relatively beneficial aerodynamic installation effect but offset by the additional weight to give a fuel-burn reduction.

Distributed generation with energy storage systems: A case study

Due to its relatively high efficiency, Distributed Generation (DG) is widely used to supply energy sources (generally power, heating and cooling) for on-site needs. This, however, presents a challenge to deal with an abrupt increase of electricity demand. To satisfy 100% of electricity demand with a high level dynamic performance energy storage is one of the most promising options for the DG system. In this study a hybrid DG system integrated with Compressed Air Energy Storage (CAES) and Thermal Energy Storage (TES) is proposed. Coupled with energy storage the DG system can perform a ‘peak shaving’ function and maintain the power output requirement properly, resulting in a lower core engine power rating and better process efficiency. To carry out technical evaluation the process flow chart is created and process models are developed. The results of simulation are also validated by IET’s CAES experimental data. The results reveal that the hybrid system’s exergy efficiency is 41.5%, and the primary fuel saving ratio is 23.13%. The CAES expander system is operated in a sliding pressure mode, satisfying various load profiles while its exergy efficiency for one day cycle is 64.7%. Compared with conventional DG system, within the hybrid system the core engine size can be downgraded by 35.3%, the fuel saving ratio is 11.06%.

Scaling model for a speed-dependent vehicle noise spectrum

Abstract Considering the well-known features of the noise emitted by moving sources, a number of vehicle characteristics such as speed, unladen mass, engine size, year of registration, power and fuel were recorded in a dedicated monitoring campaign performed in three different places, each characterized by different number of lanes and the presence of nearby reflective surfaces. A full database of 144 vehicles (cars) was used to identify statistically relevant features. In order to compare the vehicle transit noise in different environmental condition, all 1/3-octave band spectra were normalized and analysed. Unsupervised clustering algorithms were employed to group together spectrum levels with similar profiles. Our results corroborate the well-known fact that speed is the most relevant characteristic to discriminate between different vehicle noise spectrum. In keeping with this fact, we present a new approach to predict analytically noise spectra for a given vehicle speed. A set of speed-dependent analytical functions are suggested in order to fit the normalized average spectrum profile at different speeds. This approach can be useful for predicting vehicle speed based purely on its noise spectrum pattern. The present work is complementary to the accurate analysis of noise sources based on the beamforming technique.

Designing a micro Stirling engine for cleaner production of combined cooling heating and power in residential sector of different climates

In the present study the structure of an Alpha-type Stirling engine is designed which is capable of operating in reasonable operating condition ranges. The Alpha-type Stirling engine is simulated by GT-Suit program and the Solo V161 experimental data are used to validate the numerical model. The structure of the engine is kept constant and operating parameters such as, pressure, engine speed, temperature of the heater and working fluid are changed for using in a sample residential building in different climates. The engine is used for combined production of cooling, heating and power in micro scale (micro-CCHP). Three methods including following electrical load (FEL), following thermal load (FTL) and overall efficiency of the cycle are used for engine sizing. The maximum overall efficiency of the micro-CCHP ranges from 79% to 88% in different climates. The results show that both FEL and overall efficiency propose the same engine size and the highest overall efficiency for every climate. Furthermore, the reduction of environmental pollutants of CO2, CO, and NOx are calculated. The maximum CO2 reduction for every climate is more than 40%. In addition, leaking that usually occurs in this type of engine is lowered by operating at considerably lower pressure.

Performance optimization of a regenerative Brayton heat engine coupled with a parabolic dish solar collector

In this study, a detailed thermodynamic analysis of a regenerative Brayton heat engine cycle coupled with a parabolic-dish solar collector is conducted. The analysis examines the thermal performance of the coupled system for power generation applications. Important non-dimensional parameters that govern the optimized performance of the coupled system are identified. The efficiency of the coupled system is expressed in terms of three parameters namely the Brayton cycle pressure ratio, the concentration ratio of the parabolic dish collector, and the maximum temperature ratio of the Brayton cycle. The efficiency of the coupled system is then optimized with respect to the aforementioned parameters by solving the resultant system of three coupled non-linear algebraic equations using a MATLAB(R) program. Optimal values for Brayton cycle pressure ratio, concentration ratio of the parabolic dish collector, and maximum temperature ratio of the Brayton cycle are obtained corresponding to the optimal efficiency of the coupled system. Effects of variation of heat exchanger efficiency, total concentrator error, rim angle and non-dimensional radiation flux parameter on the optimal performance of the coupled system are investigated. Impact of these parameters on the engine size is also presented. In addition, a procedure for preliminary design of the coupled system using performance charts is developed. Results are presented in the form of performance charts that display the effects of changing the heat exchanger efficiency, total concentrator error, rim angle and non-dimensional radiation flux parameter on the optimal efficiency of the coupled system. The analysis show that higher optimal efficiency of the coupled system is achieved for lower values of total concentrator error and higher values of the heat exchanger efficiency. It is also seen that a solar thermal power generation system using the regenerative Brayton cycle results in migration of the optimal efficiency point towards lower values of engine pressure ratio.

Thermodynamic analysis of a gas turbine engine with a rotating detonation combustor

A rotating detonation combustor is a form of “pressure gain combustion” where one or more detonations continuously travel around an annular channel. Pressure gain combustion is a prospective technology being explored to advance gas turbine power plants. These thermodynamic cycles could potentially deliver a performance increase of 20% beyond the current state of the art. However, the combustor operates at extremely unsteady harsh conditions, and the integration of the combustor with the turbomachinery represent unprecedented aero-thermo-structural challenges. At a given instant each stream line experiences a different compression process through the combustor. In contrast to conventional combustors, where a steady approach is valid, in rotating detonation engines the flow particles entering the compressor will be exposed to different processes depending on the relative position of the rotor shaft to the detonation front. Hence, the overall performance assessment requires the development of ad-hoc tools suitable for this new class of combustors, and the modeling of the turbine exposed to supersonic pulsating flows. This paper presents a numerical tool to evaluate precisely the thermodynamic and non-isentropic processes across the entire engine. The NASA’s Toolbox for the Modeling and Analysis of Thermodynamic Systems was used to implement new libraries to help us quantify the benefits of a rotating detonation engine versus the conventional technology equipped with constant pressure combustion. The new developed libraries, based on sets of physics-based principles, replicate the engine components performance. This model should allow the optimization of components with respect to energy availability to enable optimal engine sizing and operation. Finally, the paper presents the pressure ratios for which the rotating detonation based engine outperforms the conventional power plants based on the Brayton cycle.

How Well Do We Know the Future of CO2 Emissions? Projecting Fleet Emissions from Light Duty Vehicle Technology Drivers.

While the UK has committed to reduce CO2 emissions to 80% of 1990 levels by 2050, transport accounts for nearly a fourth of all emissions and the degree to which decarbonization can occur is highly uncertain. We present a new methodology using vehicle and powertrain parameters within a Bayesian framework to determine the impact of engineering vehicle improvements on fuel consumption and CO2 emissions. Our results show how design changes in vehicle parameters (e.g., mass, engine size, and compression ratio) result in fuel consumption improvements from a fleet-wide mean of 5.6 L/100 km in 2014 to 3.0 L/100 km by 2030. The change in vehicle efficiency coupled with increases in vehicle numbers and fleet-wide activity result in a total fleet-wide reduction of 41 ± 10% in 2030, relative to 2012. Concerted internal combustion engine improvements result in a 48 ± 10% reduction of CO2 emissions, while efforts to increase the number of diesel vehicles within the fleet had little additional effect. Increasing plug-in and all-electric vehicles reduced CO2 emissions by less (42 ± 10% reduction) than concerted internal combustion engines improvements. However, if the grid decarbonizes, electric vehicles reduce emissions by 45 ± 9% with further reduction potential to 2050.

Bandwidth-Based Control Strategy for a Series HEV With Light Energy Storage System

The twin goals of maximizing fuel economy (FE) and improving consumer acceptance by reducing the cost of the energy storage system (ESS) in a series hybrid electric vehicle (SHEV) powertrain is addressed here by using energy storage as a means for filtering drive-cycle power demands on the engine, rather than an energy source for supplying an all-electric drive mode. The concept is intended to minimize, if not eliminate, the battery in the SHEV without resorting to full-range proportional control of the engine and generator. An initial optimization study reported for a mid-size SHEV showed that a 4.5-kWh lithium-ion battery pack was still required. In this paper, a sports-car-class SHEV was studied, where the challenge is to reduce the size of the ESS even more because the available space allocation is only one fourth that of the mid-size vehicle. In this paper, a controller is developed, which allows a hybridized SHEV to be realized with a light ESS. The controller includes a duty-cycling feature that manages the engine performance in multiple efficient regions and a bandwidth-limited (BWL) proportional controller feature that limits low-bandwidth battery current. The performance of the controller has been validated for a SHEV powertrain model with an 80- $\text{V}_{\mathrm{dc}}$ 1.125-kWh battery, plus an 80- $\text{V}_{\mathrm{dc}}$ 46.4-F ultracapacitor module using a customized Autonomie vehicle model. The results show that the combined FE of the new design is increased by 13%, compared with the corresponding FE in the equivalent conventional vehicle. Additional FE improvement is possible by reducing the engine size further to reflect the average power demand imposed by real drive cycles.

Lower NOx but higher particle and black carbon emissions from renewable diesel compared to ultra low sulfur diesel in at-sea operations of a research vessel

ABSTRACTGas and particle emissions from R/V Robert Gordon Sproul were measured for ultra low sulfur diesel (ULSD) and hydrogenation derived renewable diesel (HDRD) during dedicated aerosol measurement cruises in 2014 (29 September–3 October) and 2015 (4–7 and 26–28 September). CO, CO2, and NOX were measured directly from the starboard stack from the 2-stroke, small bore, high speed engine, while number and mass size distributions for both particles and black carbon (BC) were measured by intercepting the ship plume. Measurements at constant engine speeds (1600 rpm, 1300 rpm, 1000 rpm, and 700 rpm) had emission factors of CO () and NOX that were lower by 20% and 13%, respectively, for HDRD compared to ULSD at 700 rpm. However, at 1600 rpm, and were within one standard deviation for both ULSD (: 4.0 ± 0.1 g [kg-fuel]−1; : 51 ± 0.8 g [kg-fuel]−1) and HDRD (: 3.9 ± 0.2 g [kg-fuel]−1; : 51 ± 2 g [kg-fuel]−1). HDRD emission factors of particle number and mass concentrations were higher than ULSD by 46% to 107% a...